U.S. patent number 3,864,970 [Application Number 05/407,690] was granted by the patent office on 1975-02-11 for methods and apparatus for testing earth formations composed of particles of various sizes.
This patent grant is currently assigned to Schlumberger Technology Corporation. Invention is credited to William T. Bell.
United States Patent |
3,864,970 |
Bell |
February 11, 1975 |
METHODS AND APPARATUS FOR TESTING EARTH FORMATIONS COMPOSED OF
PARTICLES OF VARIOUS SIZES
Abstract
In the representative embodiments of the new and improved
methods and apparatus disclosed herein for testing earth formations
of differing compositions, fluid-admitting means carrying a
selectively-sized filter of a unique design are selectively
extended into sealing engagement with a potentially-producible
earth formation and operated so as to establish communication with
the isolated formation without the fluid-admitting means being
plugged with mudcake from the formation wall. Should, however,
loose formation materials enter the fluid-admitting means as the
testing is conducted, the filter is uniquely arranged to collect
these loose materials and halt the further erosion of such
materials from the formation wall so as to assure continued
communication with the isolated formation.
Inventors: |
Bell; William T. (Houston,
TX) |
Assignee: |
Schlumberger Technology
Corporation (New York, NY)
|
Family
ID: |
23613128 |
Appl.
No.: |
05/407,690 |
Filed: |
October 18, 1973 |
Current U.S.
Class: |
73/152.25;
73/152.51; 166/264 |
Current CPC
Class: |
E21B
49/10 (20130101) |
Current International
Class: |
E21B
49/00 (20060101); E21B 49/10 (20060101); E21b
049/04 () |
Field of
Search: |
;73/155,151,421R
;166/100,264 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Myracle; Jerry W.
Attorney, Agent or Firm: Archambeau, Jr.; Ernest R. Sherman;
William R. Moore; Stewart F.
Claims
What is claimed is:
1. A method for obtaining samples of connate fluids from earth
formations traversed by a borehole and having mudcake lining the
boreholes wall adjacent thereto and comprising the steps of:
packing-off a portion of said borehole wall adjacent to earth
formations therebeyond for isolating said wall portion and said
earth formations from fluids in said borehole;
inducting connate fluids from said formations through filtering
means having paralleled filter passages with at least a first one
of said filter passages being of an enlarged size sufficient to
pass particles of mudcake and at least a second one of said filter
passages being of a reduced size sufficient to retain loose
formation materials for initially drawing mudcake removed from said
isolated wall portion on through said first filter passage; and,
thereafter,
inducting additional connate fluids from said earth formations
through said filtering means for depositing loosened formation
particles in a permeable bridge over at least said first filter
passage so as to at least reduce the continued flow of connate
fluids therethrough and increase the continued flow of connate
fluids through said second filter passage.
2. The method of claim 1 wherein said first and second filter
passages are respectively arranged as separated elongated slits in
said filtering means.
3. The method of claim 1 wherein said first and second filter
passages are arranged as a single elongated slit in said filtering
means having an enlarged portion defining said first filter passage
and a reduced portion defining said second filter passage.
4. A method for obtaining samples of connate fluids from earth
formations traversed by a borehole and having mudcake lining the
borehole wall adjacent thereto and comprising the steps of:
packing-off a borehole wall adjacent to earth formations
therebeyond for isolating a portion of said wall and said earth
formations from fluids in said borehole;
inducting connate fluids from said isolated wall portion and earth
formations through filtering means having at least one enlarged
filter passage sized to pass particles of said mudcake and in
parallel flow relationship with at least one reduced filter passage
sized to retain loose formation particles for initially directing
at least a substantial portion of said mudcake particles on through
said enlarged filter passage; and
whenever loose formation particles are eroded from said isolated
wall portion, collecting such loosened particles with said
filtering means for reducing the flow of connate fluids through
said enlarged filter passage sufficiently to build a bridge of such
loosened particles across said enlarged filter passage and
directing at least a major portion of the flow of connate fluids
through said reduced filter passage to retain any
subsequently-loosened formation particles.
5. The method of claim 4 further including the step of:
measuring at least one property of connate fluids passing through
said filtering means for determining one or more characteristics of
said earth formations.
6. The method of claim 4 further including the step of:
collecting at least one sample of connate fluids passing through
said filtering means.
7. The method of claim 4 further including the steps of:
obtaining at least one measurement of the pressure of connate
fluids passing through said filtering means for determining one or
more characteristics of said earth formations; and, thereafter,
collecting at least one sample of connate fluids passing through
said filtering means.
8. Formation-testing apparatus adapted for suspension in a borehole
having mudcake lining the walls thereof adjacent to earth
formations containing producible connate fluids and comprising:
a body having a fluid passage adapted to receive connate
fluids;
fluid-admitting means on said body including a fluid entry coupled
to said fluid passage and adapted to be engaged with a borehole
wall for isolating a surface thereof from borehole fluids;
means selectively operable for positioning said fluid-admitting
means against a borehole wall to place said fluid entry in
communication with earth formations beyond the isolated wall
surface of said borehole wall; and
fluid-filtering means cooperatively arranged between said fluid
passage and said fluid entry for initially passing mudcake
particles displaced from said isolated wall surface on through said
filtering means into said fluid passage and operable thereafter
whenever loose formation particles of a size smaller than such
mudcake particles are eroded from said isolated wall surface for
collecting such loosened smaller formation particles as connate
fluids pass on through said filtering means into said fluid
passage.
9. The formation-testing apparatus of claim 8 wherein said
fluid-filtering means include:
a filter member having at least one reduced filter passage sized to
retain loose formation particles, and at least one enlarged filter
passage in parallel flow relationship with said reduced filter
passage sized to pass mudcake particles and cooperatively arranged
for collecting loosened formation particles in a bridge across said
enlarged filter passage for reducing the flow of connate fluids
therethrough so that at least a major portion of connate fluids
will then be directed through said reduced filter passage.
10. The formation-testing apparatus of claim 9 wherein said filter
passages are arranged as a single elongated slit having an enlarged
end portion for defining said enlarged filter passage and a reduced
end portion for defining said reduced filter passage.
11. The formation-testing apparatus of claim 9 further
including:
means selectively operable after disengagement of said
fluid-admitting means from said borehole wall for displacing from
said flud entry any loosened formation materials previously
collected as a bridge across said enlarged filter passage.
12. The formation-testing apparatus of claim 9 further
including:
pressure-measuring means coupled to said fluid passage and adapted
for providing at least one measurement representative of the
pressure of connate fluids in said fluid passage.
13. The formation-testing apparatus of claim 9 further
including:
sample-collecting means on said body and selectively operable for
obtaining a sample of connate fluids in said fluid passage.
14. The formation-testing apparatus of claim 9 further
including:
pressure-measuring means coupled to said fluid passage and adapted
for providing at least one measurement representative of the
pressure of connate fluids in said fluid passage; and
sample-collecting means on said body and selectively operable for
obtaining a sample of connate fluids in said fluid passage.
15. The formation-testing apparatus of claim 14 further
including:
means selectively operable after disengagement of said
fluid-admitting means from said borehole wall for displacing from
said fluid entry any loosened formation materials previously
collected as a bridge across said enlarged filter passage.
16. Formation-testing apparatus adapted for suspension in a
borehole having mudcake lining the walls thereof adjacent to earth
formations containing producible connate fluids and comprising:
a body having a fluid passage adapted to receive connate
fluids;
fluid-admitting means on said body and including a fluid-sampling
member having an inlet passage adapted to be engaged with a
borehole wall for isolating a surface thereof from borehole fluids
and an outlet passage downstream of said inlet passage and coupled
to said fluid passage;
means selectively operable for positioning said fluid-sampling
member against a borehole wall to place said inlet passage into
communication with earth formations beyond the isolated wall
surface of said borehole; and
filtering means cooperatively arranged on said fluid-sampling
member for intercommunicating said inlet and outlet passages and
including means defining a chamber adapted for collecting loose
formation particles entering said inlet passage, means defining at
least one enlarged filter passage between said chamber and said
outlet passage and selectively sized to initially pass mudcake
particles entering said particle-collecting chamber into said
outlet passage as well as to subsequently develop a bridge of
loosened formation particles across said enlarged filter passage
whenever such entering formation particles are collected in said
particle-collecting chamber, and means defining at least one
reduced filter passage upstream of said enlarged filter passage and
selectively sized to retain such loosened formation particles
without halting the flow of connate fluids between said inlet and
outlet passages.
17. The formation-testing apparatus of claim 16 wherein said
fluid-sampling member is tubular with a forward portion thereof
defining said inlet passage, said outlet passage includes an
inwardly-opening fluid chamber formed in an intermediate portion of
said fluid-sampling member, and said filtering means include a
filter member covering the entrance of said inwardly-opening fluid
chamber and having a forward portion with said reduced filter
passage therein and a rearward portion with said enlarged filter
passage therein and defining at least part of a side wall of said
particle-collecting chamber.
18. The formation-testing apparatus of claim 17 wherein said filter
passages are separated from one another.
19. The formation-testing apparatus of claim 17 wherein said filter
passage are joined to one another by an intermediate filter passage
having a width less than that of said enlarged filter passage.
20. The formation-testing apparatus of claim 17 wherein said filter
passages are joined to one another by an intermediate filter
passage having a width less than that of said enlarged filter
passage and greater than that of said reduced filter passage.
21. The formation-testing apparatus of claim 17 further
including:
a piston member coaxially arranged in said fluid-sampling chamber
for movement between a retracted position in the rearward portion
thereof to define the rear wall of said particle-collecting chamber
and a normal extended position in said forward portion of said
fluid-sampling member to block said inlet passage; and
means coupled to said piston member and selectively operable for
moving said piston member to its retracted position following
engagement of said fluid-sampling member with a borehole wall to
admit connate fluids into said inlet passage and for returning said
piston member to its extended position following disengagement of
said fluid-sampling member from a borehole wall to expel any
lossened formation materials previously collected as a bridge
across said enlarged filter passage from said fluid-sampling
member.
22. Formation-testing apparatus adapted for suspension in a
borehole having mudcake lining the walls thereof adjacent to earth
formations containing producible connate fluids and comprising:
a body having a first fluid passage adapted to receive connate
fluids;
fluid-admitting means on said body and including a fluid-sampling
member having a tubular forward portion adapted to be engaged with
a borehole wall for isolating a surface thereof from borehole
fluids;
means selectively operable for positioning said fluid-sampling
member against a borehole wall to establish communication with
earth formations therebeyond;
first means adapted for limiting the entrance of loose formation
particles into said first fluid passage including a second fluid
passage in said fluid-sampling member and coupled to said first
fluid passage, and filtering means cooperatively arranged on a wall
of said fluid-sampling member for controllably communicating said
second fluid passage with said tubular forward portion and
including enlarged filter passage means selectively sized to
initially pass mudcake particles entering said fluid-sampling
member as well as to subsequently develop a bridge of loosened
formation particles across said enlarged filter passage means
whenever such formation particles enter said fluid-sampling member
and reduced filter passage means upstream of said enlarged filter
passage means and selectively sized for retaining loosened
formation particles within said fluid-sampling member as filtered
connate fliuds pass through said filtering means into said second
fluid passage;
second means adapted for controlling the entrance of particles into
said fluid-sampling member and including a piston member coaxially
arranged in said fluid-sampling member for movement past said
filtering means between an advanced position within said tubular
forward portion ahead of said reduced filter passage means blocking
communication into said fluid-sampling member and a retracted
position to the rear of said enlarged filter passage means for
uncovering said filtering means and defining a space adjacent to
said enlarged filter passage means for collecting loosened
formation particles entering said tubular forward portion; and
piston-control cooperatively arranged for selectively moving said
piston member back and forth between its said advanced and
retracted positions.
23. The formation-testing apparatus of claim 22 wherein said second
fluid passage includes an annular chamber formed around an
intermediate interior wall portion of said fluid-sampling member
between said advanced and retracted positions of said piston
member; and said filtering means include a tubular filter member
coaxially mounted in said fluid-sampling member around said annular
chamber and sized for passage of said piston member as it moves
between its said positions.
24. The formation-testing apparatus of claim 23 wherein said filter
passage means are comprised of a plurality of
longitudinally-oriented slits circumferentially spaced around said
filter member and respectively having enlarged rearward portions
defining said enlarged filter passage means and reduced forward
portions defining said reduced filter passage means.
25. The formation-testing apparatus of claim 24 wherein said
longitudinally-oriented slits are symmetrically tapered between
said enlarged rearward portions and said reduced forward
portions.
26. The formation-testing apparatus of claim 23 wherein said filter
passage means are comprised of a plurality of
circumferentially-oriented slits spaced longitudinally along said
filter member with at least the rearwardmost ones of said slits
being wider than at least the forwardmost ones of said slits for
respectively defining said enlarged filter passage means and said
reduced filter passage means.
27. The formation-testing apparatus of claim 26 wherein all of said
slits ahead of said wider rearwardmost slits are of an equal width
which is narrower than the width of said wider rearwardmost
slits.
28. The formation-testing apparatus of claim 22 further
including:
sealing means cooperatively arranged on said fluid-admitting means
around said tubular forward portion and adapted for packing-off a
borehole wall around said tubular forward portion.
29. The formation-testing apparatus of claim 22 further
including:
means cooperatively mounting said fluid-sampling member on said
body for movement relative thereto between a laterally-extended
position and a retracted position; and
control means cooperatively arranged for selectively moving said
fluid-sampling member back and forth between its said extended and
retracted positions.
30. The formation-testing apparatus of claim 22 further
including:
sample-receiving means on said body and adapted for receiving
filtered connate fluids entering said first fluid passage; and
control means cooperatively arranged for selectively coupling said
sample-receiving means to said first fluid passage.
31. The formation-testing apparatus of claim 22 further
including:
pressure-monitoring means for providing indications at the surface
indicative of the pressure of connate fluids in said first fluid
passage.
32. The formation-testing apparatus of claim 22 further
including:
a wall-engaging member movably mounted on said body on the opposite
side thereof from said forward portion of said fluid-sampling
member; and
piston means cooperatively coupled to said wall-engaging member for
moving said wall-engaging member between an extended wall-engaging
position and a retracted position against said opposite body side
to respectively engage and disengage said fluid-admitting means
with and from a borehole wall.
33. The formation-testing apparatus of claim 22 further
including:
means cooperatively coupling said fluid-sampling member to said
body for movement relative to one side thereof between a
laterally-extended position and a retracted position; and
piston means cooperatively coupled to said fluid-sampling member
for moving said fluid-sampling member between its said
laterally-extended position and its said retracted position to
respectively engage and disengage said fluid-sampling member with
and from a borehole wall.
34. The formation-testing apparatus of claim 33 further
including:
a wall-engaging member movably mounted on said body on the opposite
side thereof; and
piston means cooperatively coupled to said wall-engaging position
and a retracted position against said opposite body side upon
movement of said fluid-sampling member between its said positions.
Description
Until very recently, the so-called wireline formation testers,
which have been most successful in commercial service have, for the
large part, been limited to attempting only a single test or, at
best, two tests of selected earth formations. Generally, the
success of these tests has depended to some extent upon knowing in
advance the general character of the particular formations which
were to be tested so that the tester could be equipped as required
to test a formation of a given nature.
For example, where the formations to be tested were considered to
be fairly competent and, therefore, not easily eroded, testers such
as that shown in U.S. Pat. No. 3,011,554 have been highly
effective. On the other hand, in those situations where tests were
to be conducted in fairly incompetent or unconsolidated formations,
it has usually been the practice to use new and improved testers
such as those shown in U.S. Pat. No. 3,352,361, U.S. Pat. No.
3,530,933, U.S. Pat. No. 3,565,169 or U.S. Pat. No. 3,653,435. As
fully described in these last-mentioned patents, each of those
testing tools employs a tubular sampling member which is
cooperatively associated with a filtering medium having fluid
openings of a selected, but uniform, size for preventing the
unwanted entrance of unconsolidated formation materials into the
testing tool. Thus, except for dual-purpose tools such as that
shown in U.S. Pat. No. 3,261,402, these typical formation testing
tools have been most successful in making tests in formations which
are known in advance either to be fairly competent or to be
relatively unconsolidated. Moreover, since all of these prior-art
testers are operated only once during a single trip into a well
bore, it has been customary to simply select in advance the
particular size of filter medium believed to be best suited for a
given testing operation.
One of the most significant advances in the formation-testing art
has been the recent introduction into commercial service of the new
and improved repetitively-operable testers such as fully described
in U.S. Pat. No. 3,780,575. As disclosed there, these tools are
capable of repetitively taking any number of pressure measurements
from various formations as well as collecting at least two fluid
samples during a single trip in a given well bore.
Although these new and improved testers have been quite successful,
there are situations where the performance of these testers is
significantly affected since no one filtering medium is capable of
operating efficiently with every type of earth formation. For
instance, if the tester is equipped with a particular filter which
is best suited for stopping exceptionally-fine formation materials,
the flow rate for this tester will be materially limited where a
fairly-competent formation is being tested. More importantly, in
situations like this, it is not at all uncommon for the filter to
be quickly plugged by the mudcake which usually lines the borehole
wall adjacent to a potentially-producible formation. Thus, a test
under these conditions will often be inconclusive, if not
misleading, since it will not be known for sure whether the
formation is truly unproductive or if the filter was simply plugged
at the outset of the test. On the other hand, if the tester is then
using a filter designed for filtering out only fairly-large loose
formation materials, there will often be an excessive induction of
very-fine formation materials into the tool where the tool is
testing a highly-unconsolidated formation. This will, of course,
frequently result in a continued erosion of the formation wall
around the sealing pad so that communication with the formation is
quickly lost. This also causes an incomplete or inconclusive
test.
It will be recognized, of course, that is wholly impractical to
change the filter in a repetitively-operable tool of this type
between tests of different types of formations in a given borehole.
Moreover, there is no assurance that the character of various
formations traversed by a given borehole can be reliably determined
in advance.
Accordingly, it is an object of the present invention to provide
new and improved formation-testing methods and apparatus for
reliably obtaining multiple measurements of one or more fluid or
formation characteristics as well as for selectively collecting one
or more samples of connate fluids, if desired, from different earth
formations of any character even where these formations vary in
their compositions and competency.
This and other objects of the present invention are attained by
providing formation-testing apparatus having fluid-admitting means
adapted for selective movement into sealing engagement with a
potentially-producible earth formation to isolate a portion thereof
from the borehole fluids. In practicing the methods of the present
invention for testing a formation, mudcake is first inducted into
the fluid-admitting means by way of a first filtering passage
selectively sized to readily pass such plugging materials. Then,
should incompetent formation materials be drawn into the
fluid-admitting means, these materials are collected so as to halt
their further erosion from the borehole wall by quickly blocking at
least substantial flow through this first passage as well as
thereafter directing the flow of connate fluids through a second
filter passage selectively sized to be smaller than the formation
materials. In the new and improved apparatus of the present
invention, the fluid-admitting means are provided with filtering
means having one or more enlarged filter passages sized to easily
pass large plugging materials such as mudcake particles and one or
more reduced filter passages which are sized to screen or retain
formation particles of a selected size. In this manner, when the
fluid-admitting means are initially placed into communication with
an isolated earth formation, mudcake lining the formation wall will
be passed through the enlarged filter passages thereby leaving the
inlet face of the filtering means free of such plugging materials.
Thereafter, should loose formation materials be inducted into the
fluid-admitting means, they will be collected in a compact mass
along the inlet face of the filtering means so as to effectively
block at least significant flow through the enlarged filter
passages and direct the flow of producible connate fluids through
the reduced filter passages.
The novel features of the present invention are set forth with
particularity in the appended claims. The invention, together with
further objects and advantages thereof, may be best understood by
way of the following descriptions of the new and improved methods
of the present invention as well as various embodiments of
exemplary apparatus employing the principles of the invention as
illustrated in the accompanying drawings, in which:
FIg. 1 depicts the surface and downhole portions of one embodiment
of formation-testing apparatus including new and improved
fluid-admitting means incorporating the principles of the present
invention;
FIG. 2 is an enlarged view of a preferred embodiment of the new and
improved fluid-admitting means shown in FIG. 1;
FIGs. 3A and 3B together show a somewhat-schematic representation
of the formation-testing tool illustrated in FIG. 1 as the tool
will appear in its initial operating position in readiness for
practicing the new and improved methods of the invention;
FIGS. 4, 5, 6A and 6B respectively depict the successive positions
of various components of the testing tool shown in FIGS. 3A and 3B
during the course of a typical testing and sampling operation to
illustrate the methods as well as the operation of the new and
improved fluid-admitting means of the present invention; and
FIGS. 7-9 schematically illustrate the practice of the methods of
the present invention by the new and improved fluid-admitting means
with different types of earth formations as well as depict
alternative embodiments of filter members which may be employed
therewith to achieve the objects of the present invention.
Turning now to FIG. 1 a preferred embodiment of new and improved
fluid-admitting means 10 incorporating the principles of the
present invention is shown on a formation-testing tool 11 as this
tool will appear during the course of a typical measuring and
sampling operation in a well bore such as a borehole 12 penetrating
one or more earth formations as at 13 and 14. As illustrated, the
tool 11 is suspended in the borehole 12 from the lower end of a
typical multiconductor cable 15 that is spooled in the usual
fashion on a suitable winch (not shown) at the surface and coupled
to the surface portion of a tool-control system 16 as well as
typical recording-and-indicating apparatus 17 and a power supply
18. In its preferred embodiment, the tool 11 includes an elongated
body 19 which encloses the downhole portion of the tool-control
system 16 and carries a selectively-extendible tool-anchoring
member 20 arranged on one or more piston actuators, as at 21, for
movement from the opposite side of the body from the new and
improved fluid-admitting means 10 as well as one or more
fluid-collecting chambers 22 and 23 which are tandemly coupled to
the lower end of the tool body 19.
As is explained in greater detail in U.S. Pat. No. 3,780,575 which
is incorporated by reference herein, the depicted formation-testing
tool 11 and its control system 16 are cooperatively arranged so
that, upon command from the surface, the tool can be selectively
placed in any one or more of five selected operating positions. As
will be subsequently described briefly, the control system 16 will
function either to successively place the tool 11 in one or more of
these positions or else to selectively cycle the tool between
various ones of these operating positions. These five operating
positions are simply achieved by selectively moving suitable
control switches, as schematically represented at 24 and 25,
included in the surface portion of the control system 16 to various
switching positions, as at 26-31, so as to selectively apply power
to different conductors 32-38 in the cable 15.
The new and improved fluid-admitting means 10 of the present
invention are cooperatively arranged for selectively sealing-off or
isolating selected portions of the wall of the borehole 12; and,
once a selected portion of the borehole wall is packed-off or
isolated from the borehole fluids, establishing pressure or fluid
communication with the adjacent earth formation, as at 13. In the
preferred embodiment depicted in FIG. 2, the fluid-admitting means
10 include an elastomeric annular sealing pad 39 mounted on the
forward face of an upright support member or plate 40 that is
coupled to a longitudinally-spaced pair of laterally-movable piston
actuators, as at 41, which are similar to the actuators 21 and are
arranged transversely on the tool body 19 for moving the sealing
pad back and forth in relation to the forward side of the tool
body. Accordingly, as the control system 16 selectively supplies a
pressured hydraulic fluid to the piston actuators 41, the sealing
pad 39 will be moved laterally between a retracted position
adjacent to the forward side of the tool body 19 and an advanced or
forwardly-extended position.
By arranging the annular sealing member 39 on the opposite side of
the tool body 19 from the tool-anchoring member 20 (FIG. 1), the
simultaneous extension of these two wall-engaging members will, of
course, be effective for urging the sealing pad into sealing
engagement with the adjacent wall of the borehole 12 as well as for
anchoring the tool 11. It should, however, be appreciated that the
tool-anchoring member 20 would not be needed if the effective
stroke of the piston actuators 41 is sufficient for assuring that
the sealing pad 39 can be extended into firm sealing engagement
with one wall of the borehole 12 with the rear of the tool body 19
securely anchored against the opposite wall of the borehole.
Conversely, the piston actuators 21 could be similarly omitted
where the extension of the tool-anchoring member 20 alone would be
effective for moving the front side of the tool body 19 forwardly
toward one wall of the borehole 12 so as to place the sealing pad
39 into firm sealing engagement therewith. However, in the
preferred embodiment of the formation-testing tool 11, both the
tool-anchoring member 20 and the fluid-admitting means 10 are
arranged to be simultaneously extended to enable the tool to be
operated in boreholes of substantial diameter. This preferred
design of the tool 11, of course, keeps the overall stroke of the
piston actuators 21 and 41 to a minimum so as to reduce the overall
diameter of the tool body 19.
To conduct connate fluids into the testing tool 11, the
fluid-admitting means 10 of the present invention further include
an enlarged tubular member 42 having an open forward portion
coaxially disposed within the annular sealing pad 39 and a closed
rear portion which is slidably mounted within a larger tubular
member 43 secured to the rear face of the plate 40 and extended
rearwardly therefrom. By arranging the nose of the tubular
fluid-admitting member 42 to normally protrude a short distance
ahead of the forward face of the sealing pad 39, extension of the
fluid-admitting means 10 will engage the forward end of the
fluid-admitting member with the adjacent surface of the wall of the
borehole 12 just before the annular sealing pad is also forced
thereagainst for isolating that portion of the borehole wall as
well as the nose of the fluid-admitting member from the borehole
fluids. The significance of this sequence of engagement will be
subsequently explained. To selectively move the tubular
fluid-admitting member 42 in relation to the enlarged outer member
43, the smaller tubular member is slidably disposed within the
outer tubular member and fluidly sealed in relation thereto as by
sealing members 44 and 45 on inwardly-enlarged end portions 46 and
47 of the outer member and a sealing member 48 on the
enlarged-diameter intermediate portion 49 of the inner member.
Accordingly, it will be appreciated that by virtue of the sealing
members 44, 45 and 48, enclosed piston chambers 50 and 51 are
defined within the outer tubular member 43 and on opposite sides of
the outwardly-enlarged portion 49 of the inner tubular member 42
which, of course, functions as a piston member. Thus, by applying
an increased hydraulic pressure in the rearward chamber 50, the
fluid-admitting member 42 will be moved forwardly in relation to
the outer tubular member 43 as well as to the sealing pad 39.
Conversely, upon the application of an increased hydraulic pressure
to the forward piston chamber 51, the fluid-admitting member 42
will be retracted in relation to the outer member 43 and the
sealing pad 39.
Pressure or fluid communication with the new and improved
fluid-admitting means 10 of the present invention is preferably
controlled by means such as a generally-cylindrical valve member 52
which is coaxially disposed within the fluid-admitting member 42
and cooperatively arranged for axial movement therein between a
retracted or open position and the illustrated advanced or closed
position where the enlarged forward end 53 of the valve member is
substantially, if not altogether, sealingly engaged with the
forwardmost interior portion of the fluid-admitting member. To
support the valve member 52, the rearward portion of the valve
member is axially hollowed, as at 54, and coaxially disposed over a
tubular member 55 projecting forwardly from the transverse wall 56
closing the rear end of the fluid-admitting member 42. The axial
bore 54 is reduced and extended forwardly along the valve member 52
to a termination with one or more transverse fluid passages 57 in
the forward portion of the valve member just behind its enlarged
head 53.
To provide actuating means for selectively moving the valve member
52 in relation to the fluid-admitting member 42, the rearward
portion of the valve member is enlarged, as at 58, and outer and
inner sealing members 59 and 60 are coaxially disposed thereon and
respectively sealingly engaged with the interior of the
fluid-admitting member and the exterior of the forwardly-extending
tubular member 55. A sealing member 61 mounted around the
intermediate portion of the valve member 52 and sealingly engaged
with the interior wall of the adjacent portion of the
fluid-admitting member 42 fluidly seals the valve member in
relation to the fluid-admitting member. Accordingly, it will be
appreciated that by increasing the hydraulic pressure in the
enlarged piston chamber 62 defined to the rear of the enlarged
valve portion 58 which serves as a piston member, the valve member
52 will be moved forwardly in relation to the fluid-admitting
member 42. Conversely, upon application of an increased hydraulic
pressure to the forward piston chamber 63 defined between the
sealing members 59 and 61, the valve member 52 will be moved
rearwardly along the forwardly-projecting tubular member 55 so as
to retract the valve member in relation to the fluid-admitting
member 42.
As previously discussed, it will, of course, be appreciated that
many earth formations, as at 13, are relatively unconsolidated and
are, therefore, readily eroded by the withdrawal of connate fluids.
Thus, to prevent any significant erosion of such unconsolidated
formation materials, the fluid-admitting member 42 is arranged to
define an internal annular space 64 and a flow passage 65 in the
forward portion of the fluid-admitting member. As will subsequently
be described in greater detail by reference to FIGS. 7-9, the
objects of the present invention are preferably attained by
coaxially mounting a tubular filter member 66 (or 66') with slits
or apertures therein of a unique arrangement in the nose of the
fluid-admitting member 42 so as to cover the annular space 64. In
this manner, when the valve member 52 is retracted from its
extended position inside of the filter, formation fluids will be
compelled to pass through the now-exposed filter member 66 ahead of
the enlarged head 53, into the annular space 64, and then through
the fluid passage 65 into the fluid passage 57 and the tubular
member 55. Thus, as the valve member 52 is retracted, should loose
or unconsolidated formation materials be eroded from a formation as
connate fluids are withdrawn therefrom, the materials will be
stopped by the uniquely-arranged filter 66 ahead of the enlarged
head 53 of the valve member thereby quickly forming a permeable
barrier to prevent the continued erosion of loose formation
materials once the valve member halts.
Turning now to FIGS. 3A and 3B, the new and improved
fluid-admitting means 10 as well as the entire downhole portion of
the control system 16, the tool-anchoring member 20, and the
fluid-collecting chambers 22 and 23 are schematically illustrated
with their several elements or components depicted as they will
respectively be arranged when the tool 11 is fully retracted and
the control switches 24 and 25 are in their first or "off"
operating positions 26 (FIG. 1). Since the aforementioned U.S. Pat.
No. 3,780,575 fully describes the control system 16 and various
components of the tool 11, it is believed adequate to simply cover
only the major aspects of this system.
A sample or flow line 67 is cooperatively arranged in the
formation-testing tool 11 and has one end coupled, as by a flexible
conduit 68, to the fluid-admitting means 10 and its other end
terminated in a pair of branch conduits 69 and 70 respectively
coupled to the fluid-collecting chambers 22 and 23. To control
fluid communication between the new and improved fluid-admitting
means 10 and the fluid-collecting chambers 22 and 23,
normally-closed flow-control valves 71-73 of a similar or identical
design are arranged respectively in the flow line 67 and in the
branch conduits 69 and 70 leading to the sample chambers. For
reasons which will subsequently be described, a normally-open
control valve 74 which is preferably similar to the normally-closed
control valves 71-73 is cooperatively arranged in a branch conduit
75 for selectively controlling communication between the borehole
fluids exterior of the tool 11 and the upper portion of the flow
line 67 and the flexible conduit 68 extending between the flow-line
control valve 71 and the new and improved fluid-admitting means
10.
As illustrated, the normally-open control valve 74, for example, is
operated by a typical pressure-responsive actuator 76 which is
arranged to close the valve in response to an actuating pressure of
at least a predetermined magnitude. As fully described in the
aforementioned U.S. Pat. No. 3,780,575, a spring biasing the
control valve 74 to its open position is cooperatively arranged to
establish the magnitude of the pressure required to close the
valve. Furthermore, the normally-closed control valves 71-73 are
preferably similar to the control valve 74 except that they are
respectively operated by pressure-responsive actuators 77-79
selectively arranged to open these valves in response to pressures
of different predetermined magnitudes.
In the particular embodiment of the testing tool 11 shown in FIGS.
3A and 3B, a branch conduit 80 is coupled to the flow line 67 at a
convenient location between the sample-chamber control valves 72
and 73 and the flow-line control valve 71, with this branch conduit
being terminated at an expansion chamber 81 of a predetermined
volume. A reduced-diameter displacement piston 82 is operatively
mounted in the chamber 81 and arranged to be moved between selected
upper and lower positions therein by a typical piston actuator
shown generally at 83. Accordingly, it will be appreciated that
upon movement of the displacement piston 82 from its lower position
as illustrated in FIG. 3A to an elevated or upper position, the
combined volume of whatever fluids that are then contained in the
branch conduit 80 as well as in that portion of the flow line 67
between the flow-line control valve 71 and the sample-chamber
control valves 72 and 73 will be correspondingly increased.
As best seen in FIG. 3A, the control system 16 further includes a
pump 84 that is coupled to a driving motor 85 and cooperatively
arranged for pumping a suitable hydraulic fluid such as oil or the
like from a reservoir 86 into a discharge or outlet line 87. Since
the tool 11 is to be operated at extreme depths in boreholes, as at
12, which typically contain dirty and usually corrosive fluids, the
reservoir 86 is preferably arranged to totally immerse the pump 84
and the motor 85 in the clean hydraulic fluid. The reservoir 86 is
also provided with a spring-biased isolating piston 88 for
maintaining the hydraulic fluid at a pressure about equal to the
hydrostatic pressure at whatever depth the tool is then situated as
well as accommodating volumetric changes in the hydraulic fluid
which may occur under different borehole conditions. one or more
inlets, as at 89 and 90, are provided for returning hydraulic fluid
from the control system 16 to the reservoir 86 during the operation
of the tool 11.
The fluid outlet line 87 is divided into two major branch lines
which are respectively designated as the "set" line 91 and the
"retract" line 92. To control the admission of hydraulic fluid to
the "set" and "retract" lines 91 and 92, a pair of normally-closed
solenoid-actuated valves 93 and 94 are cooperatively arranged to
selectively admit hydraulic fluid to the two lines as the control
switch 24 at the surface is selectively positioned; and a typical
check valve 95 is arranged in the set line 91 downstream of the
control valve 93 for preventing the reverse flow of the hydraulic
fluid whenever the pressure in the set line is greater than that
then existing in the fluid outlet line 87. Typical pressure
switches 96-98 are cooperatively arranged in the set and retract
lines 91 and 92 for selectively starting and stopping the pump 84
as required to maintain the line pressure within a selected
operating range. Since the pump 84 is preferably a
positive-displacement type to achieve a rapid predictable rise in
the operating pressures in the set and retract lines 91 and 92,
each time the pump is to be started the control system 16 also
functions to temporarily open the control valve 94 (if it is not
already open) as well as a third normally-closed solenoid-actuated
valve 99 for bypassing hydraulic fluid directly from the output
line 87 to the reservoir 86 by way of the return line 89. Once the
motor 85 has reached operating speed, the bypass valve 99 will, of
course, be reclosed and either the set line control valve 93 or the
retract line control valve 94 will be selectively opened as
required for that particular operational phase of the tool 11.
Accordingly, it will be appreciated that the control system 16
cooperates for selectively supplying pressured hydraulic fluid to
the set and retract lines 91 and 92. Since the pressure switches 96
and 97 respectively function only to limit the pressures in the set
and retract lines to a selected maximum pressure range commensurate
with the rating of the pump 84, the control system 16 is further
arranged to cooperatively regulate the pressure of the hydraulic
fluid which is being supplied at various times to selected portions
of the system. Although this regulation can be accomplished in
different manners, it is preferred to employ a number of
pressure-actuated control valves such as those shown schematically
at 100-103 in FIGS. 3A and 3B for controlling the hydraulic fluid
in the control system 16. As shown in FIG. 3A, the hydraulic
control valve 100, for example, includes a valve body 104 having an
enlarged upper portion carrying a downwardly-biased actuating
piston 105 which is cooperatively coupled to a valve member 106 as
by an upright stem 107 thereon which is slidably disposed in an
axial bore 108 in the piston. A spring 109 of selected strength is
disposed in the axial bore 108 for normally urging the valve member
106 into seating engagement.
In its non-actuated position depicted in FIG. 3A, the control valve
100 (as well as the valve 101) will, therefore, simply function as
a normally-closed check valve. That is to say, in this operating
position, hydraulic fluid can flow only in a reverse direction
whenever the pressure at the valve outlet is sufficiently greater
than the inlet pressure to unseat the valve member 106 against the
predetermined closing force imposed by the spring 109. On the other
hand, whenever the actuating piston 105 is elevated by the
application of hydraulic pressure thereto, opposed shoulders, as at
110, on the stem 107 and the piston 105 will engage for unseating
the valve member 106. As shown in FIGS. 3A and 3B, it will be
appreciated that the control valve 102 (as well as the valve 103)
is similar to the control valve 100 except that in these
first-mentioned control valves, the valve member, as at 111, is
preferably rigidly coupled to its associated actuating piston, as
at 112. Thus, the control valve 102 (as well as the valve 103) has
no alternate checking action allowing reverse flow but is simply a
normally-closed pressure-actuated valve for selectively controlling
fluid communication between its inlet and outlet ports.
The set line 91 downstream of the check valve 95 is comprised of a
low-pressure section 113 having one branch 114 coupled to the fluid
inlet of the control valve 102 and another branch 115 which is
coupled to the fluid inlet of the hydraulic control valve 100 to
selectively supply hydraulic fluid to a high-pressure section 116
of the set line which is itself terminated at the fluid inlet of
the hydraulic control valve 103. To regulate the supply of
hydraulic fluid from the low-pressure section 113 to the
high-pressure section 116 of the set line 91, a
pressure-communicating line 117 is coupled between the low-pressure
section and the control port of the hydraulic control valve 100.
Accordingly, so long as the pressure of the hydraulic fluid in the
low-pressure section of the set line 91 remains below the
predetermined actuating pressure required to open the hydraulic
control valve 100, the high-pressure section 116 will be isolated
from the low-pressure section 113. Conversely, once the hydraulic
pressure in the low-pressure line 113 reaches the predetermined
actuating pressure of the valve 100, the hydraulic control valve
will open to admit the hydraulic fluid into the high-pressure line
116.
The hydraulic control valves 102 and 103 are respectively arranged
to selectively communicate the low-pressure and high-pressure
sections 113 and 116 of the set line 91 with the fluid reservoir
86. To accomplish this, the control ports of the two hydraulic
control valves 102 and 103 are each connected to the retract line
92 by suitable pressure-communicating lines 118 and 119. Thus,
whenever the pressure in the retract line 92 reaches their
respective predetermined actuating levels, the hydraulic control
valves 102 and 103 will be respectively opened to selectively
communicate the two sections 113 and 116 of the set line 91 with
the reservoir 86 by way of the return line 89 coupled to the
respective outlets of the two control valves.
As previously mentioned, in FIGS. 3A and 3B the tool 11 and the
sub-surface portion of the control system 16 are depicted as their
several components will appear when the tool is retracted. At this
point, the tool-anchoring member 20 and the sealing pad 39 are
respectively retracted against the tool body 19 to facilitate
passage of the tool 11 into the borehole 12. To prepare the tool 11
for lowering into the borehole 12, the switches 24 and 25 are moved
from their first or off positions 26 to their second or
"initialization" positions 27. At this point, the hydraulic pump 84
is started to raise the pressure in the retract line 92 to a
selected maximum to be certain that the pad 39 and the
tool-anchoring member 20 are fully retracted. At this time, the
pressure-equalizing valve 74 is open and that portion of the flow
line 67 between the closed flow-line control valve 71 and the
fluid-admitting means 10 will be filled with borehole fluids as the
tool 11 is being lowered into the borehole 12.
When the tool 11 is at a selected operating depth, the switches 24
and 25 are advanced to their third positions 28. Then, once the
pump 84 has reached its rated operating speed, the hydraulic
pressure in the output line 87 will rapidly rise to its selected
maximum operating pressure as determined by the maximum or off
setting of the pressure switch 96. As the pressure progressively
rises, the control system 16 will successively function at selected
intermediate pressure levels for sequentially operating the several
control valves 71-74 and 100-103 in an operating cycle such as the
one described fully in the aforementioned U.S. Pat. No. 3,780,575.
It must, however, be recognized that the forthcoming particular
operational sequence of the tool 11 as illustrated is not essential
to either the practice of the methods of the present invention or
the successful operation of the new and improved fluid-admitting
means 10. Those skilled in the art will, therefore, understand that
the present invention can be practiced either with different types
of formation-testing tools or with different arrangements of the
tool 11 and the control system 16.
Turning now to FIG. 4, selected portions of the control system 16
and various components of the tool 11 are schematically represented
to illustrate the operation of the illustrated embodiment of the
tool at about the time that the pressure in the hydraulic output
line 87 reaches its lowermost intermediate pressure level. To
facilitate an understanding of the operation of the tool 11 and the
control system 16 at this point in the operating cycle illustrated
in the several drawings, only those components which are then
operating are shown in FIG. 4.
At this time, since the control switch 24 (FIG. 1) is in its third
position 28, the solenoid valves 93 and 99 will be open; and, since
the hydraulic pressure in the set line 91 has not yet reached the
upper pressure limit as determined by the pressure switch 96, the
pump motor 85 will still be operating. Since the hydraulic control
valve 100 (not shown in FIG. 4) is closed, the high-pressure
section 116 of the set line 91 will still be isolated from the
low-pressure section 113. Simultaneously, the hydraulic fluid
contained in the forward pressure chambers of the piston actuators
21 and 41 will be displaced (as shown by the arrows as at 120) to
the retract line 92 and returned to the reservoir 86 by way of the
open solenoid valve 99. These actions will, of course, cause the
tool-anchoring member 20 as well as the sealing pad 39 to be
respectively extended in opposite lateral directions until each has
moved into firm engagement with the opposite sides of the borehole
12.
It will be noticed in FIG. 4 that hydraulic fluid will be admitted
by way of branch hydraulic lines 121 and 122 to the enclosed
annular chamber 50 to the rear of the enlarged-diameter portion 49
of the fluid-admitting member 42. At the same time, hydraulic fluid
from the piston chamber 51 ahead of the enlarged-diameter portion
49 will be discharged by way of branch hydraulic lines 123 and 124
to the retract line 92 for progressively moving the fluid-admitting
member 42 forwardly in relation to the sealing member 39 until the
nose of the fluid-admitting member engages the wall of the borehole
12 and then halts. The sealing pad 39 is then urged forwardly in
relation to the now-halted tubular member 42 until the pad
sealingly engages the borehole wall for packing-off or isolating
the isolated wall portion from the borehole fluids. In this manner,
mudcake immediately ahead of the fluid-admitting member 42 will be
displaced radially away from the nose of the fluid-admitting member
so as to minimize the quantity of unwanted mudcake which will
subsequently be admitted into the fluid-admitting means 10. Those
skilled in the art will appreciate the significance of this unique
arrangement.
It should also be noted that although the pressured hydraulic fluid
is also admitted at this time into the forward piston chamber 63
between the sealing members 59 and 61 on the valve member 52, the
valve member is temporarily prevented from moving rearwardly in
relation to the inner and outer tubular members 42 and 55 inasmuch
as the hydraulic control valve 101 (not shown in FIG. 4) is
preferably still closed thereby temporarily trapping the hydraulic
fluid in the rearward piston chamber 62 to the rear of the valve
member. The purpose of this delay in the retraction of the valve
member 52 will be subsequently explained.
As also illustrated in FIG. 4, the hydraulic fluid in the
low-pressure section 113 of the set line 91 will also be directed
by way of a branch hydraulic line 125 to the piston actuator 83.
This will, of course, result in the displacement piston 82 being
elevated as the hydraulic fluid from the piston actuator 83 is
returned to the retract line 92 by way of a branch hydraulic
conduit 126. As will be appreciated, elevation of the displacement
piston 82 in the expansion chamber 81 will be effective for
significantly decreasing the pressure initially existing in the
isolated portions of the branch line 80 and the flow line 67
between the still-closed flow-line control valve 71 and the
still-closed chamber control valves 72 and 73 (not shown in FIG.
4). The purpose of this pressure reduction will be subsequently
explained.
Once the tool-anchoring member 20, the sealing pad 39 and the
fluid-admitting member 42 have respectively reached their extended
positions as illustrated in FIG. 4, it will be appreciated that the
hydraulic pressure delivered by the pump 84 will again rise. Then,
once the pressure in the output line 87 has reached its second
intermediate level of operating pressure, the hydraulic control
valve 101 will open in response to this pressure level to now
discharge the hydraulic fluid previously trapped in the piston
chamber 62 to the rear of the valve member 52 back to the reservoir
86.
As illustrated in FIG. 5, once the hydraulic control valve 101
opens, the hydraulic fluid will be displaced from the rearward
piston chamber 62 by way of branch hydraulic lines 127, 128 and 124
to the retract line 92 as pressured hydraulic fluid from the set
line 91 surges into the piston chamber 63 ahead of the
enlarged-diameter portion 58 of the valve member 52. This will, of
course, cooperate to rapidly drive the valve member 52 rearwardly
in relation to the now-halted fluid-admitting member 42 for
establishing fluid or pressure communication between the isolated
portion of the earth formation 13 and the flow passages 54 and 57
in the valve member by way of the filter member 66.
Although this is not fully illustrated in FIG. 5, it will be
recalled from FIGS. 3A and 3B that the control valves 71-73 are
initially closed to isolate the lower portion of the flow line 67
between these valves as well as the branch line 80 leading to the
pressure-reduction chamber 81. However, the flow-line
pressure-equalizing control valve 74 will still be open at the time
the hydraulic control valve 101 opens to retract the valve member
52 as depicted in FIG. 5. Thus, as the valve member 52
progressively uncovers the new and improved filtering member 66,
borehole fluids at a pressure greater than that of any connate
fluids which may be present in the isolated earth formation 13 will
be introduced into the upper portion of the flow line 67 and, by
way of the flexible conduit member 68, into the rearward end of the
tubular member 55. As these high-pressure borehole fluids pass into
the annular space 64 around the filtering member 66, they will be
forcibly discharged (as shown by the arrows 129) from the forward
end of the fluid-admitting member 42 for washing away any plugging
materials such as mudcake or the like which may have become
deposited on the internal surface of the filtering member when it
is first uncovered by the retraction of the valve member 52. Thus,
the particular embodiment of the control system 16 illustrated in
the drawings is operative for providing a momentary outward surge
or reverse flow of borehole fluids for cleansing the filtering
member 66 of unwanted debris or the like before a sampling or
testing operation is commenced. This is, however, not essential to
the successful operation of the new and improved fluid-admitting
means 10.
It will be appreciated that once the several components of the
formation-testing tool 11 and the control system 16 have reached
their respective positions as depicted in FIG. 5, the hydraulic
pressure in the output line 87 will again quickly increase to its
next intermediate pressure level. Once the pump 84 has increased
the hydraulic pressure in the output line 87 to this next
predetermined intermediate pressure level, the hydraulic control
valve 100 will selectively open as depicted in FIG. 6A. As seen
there, opening of the hydraulic control valve 100 will be effective
for now supplying hydraulic fluid to the high-pressure section 116
of the set line 91 and two branch conduits 130 and 131 connected
thereto for successively closing the pressure-equalizing valve 74
and then opening the flow-line control valve 71.
In this manner, as respectively depicted by the several arrows at
132 and 133, hydraulic fluid at a pressure representative of the
intermediate operating level will be supplied by way of a typical
check valve 134 to the upper portion of the actuator 76 of the
normally-open pressure-equalizing valve 74 as fluid is exhausted
from the lower portion of the actuator by way of a conduit 135
coupled to the retract line 92. This will, of course, be effective
for closing the pressure-equalizing valve 74 so as to now block
further communication between the flow line 67 and the borehole
fluids exterior of the tool 11. Simultaneously, the hydraulic fluid
will also be admitted to the lower portion of the actuator 77 of
the flow-line control valve 71. By arranging the actuator 76 for
the normally-open pressure-equalizing valve 74 to operate somewhat
quicker than the actuator 77 for the normally-closed flow-line
control valve 71, the second valve will be momentarily retained in
its closed position until the first valve has had time to close.
Then, once the pressure-equalizing valve 74 closes, as the
hydraulic fluid enters the lower portion of the actuator 77 of the
flow-line control valve 71, the latter valve will be opened as
hydraulic fluid is exhausted from the upper portion of its actuator
through a typical check valve 136 and a branch return line 137
coupled to the retract line 92.
It will be appreciated, therefore, that with the tool 11 in the
position depicted in FIGS. 6A and 6B, the flow line 67 is now
isolated from the borehole fluids and is in communication with the
isolated portion of the earth formation 13 by way of the flexible
conduit 68. It will be recalled from the preceding discussion of
FIG. 4 that the fluid volumes in the branch flow line 80 as well as
the portion of the main flow line 67 between the flow-line control
valve 71 and the sample-chamber control valves 72 and 73 were
previously expanded by the upward movement of the displacement
piston 82 in the reduced-volume chamber 81. Thus, upon opening of
the flow-line control valve 71, the isolated portion of the earth
formation 13 will be communicated with the reduced-pressure space
represented by the previously-isolated portions of the flow line 67
and the branch conduit 80.
Of particular interest to the present invention, it should be
further noted that should the formation 13 be relatively
unconsolidated, the rearward movement of the valve member 52 in
cooperation with the forward movement of the fluid-admitting member
42 will allow only those loose formation materials displaced by the
advancement of the fluid-admitting member into the formation to
enter the fluid-admitting member. This is to say, the
fluid-admitting member 42 can advance into the formation 13 only by
displacing loose formation materials; and, since the space opened
within the forward end of the fluid-admitting member by the
rearward displacement of the valve member 52 is the only place into
which the loose formation materials can enter, further erosion of
the formation materials will be halted once the fluid-admitting
member has been filled with loose materials as shown at 138 in FIG.
6B. On the other hand, should a formation interval which is being
tested be relatively well-compacted, the advancement of the
fluid-admitting member 42 will be relatively slight with its nose
making little or no penetration into the isolated earth formation.
It will, of course, be appreciated that the nose of the
fluid-admitting member 42 will be urged outwardly with sufficient
force to at least penetrate the mudcake which typically lines the
borehole walls adjacent to permeable earth formations. In this
situation, however, the forward movement of the fluid-admitting
member 42 will be unrelated to the rearward movement of the valve
member 52 as it progressively uncovers the filtering member 66. In
either case, the sudden opening of the valve 52 will cause the plug
of mudcake in the nose of the fluid-admitting member 42 to be
pulled to the rear of the filter 66. The significance of these
actions will be subsequently explained.
As best seen in FIGS. 6A and 6B, therefore, should there be any
producible connate fluids in the isolated earth formation 13, the
formation pressure will be effective for displacing these connate
fluids by way of the new and improved fluid-admitting means 10 into
the flow line until such time that the lower portion of the flow
line 67 and the branch conduit 80 are filled and pressure
equilibrium is established in the entire flow line. By arranging a
typical pressure-measuring transducer, as at 140 (or, if desired,
one or more other suitable types of property-measuring transducers)
in the flow line 67, one or more measurements representative of the
characteristics of the connate fluids and the formation 13 may be
transmitted to the surface by a conductor 141 and either indicated
or, if desired, recorded on the recording apparatus 17 (FIG. 1). In
any event, the pressure measurements provided by the transducer 140
will, of course, permit the operator at the surface to readily
determine the formation pressure as well as to obtain one or more
indications representative of the potential producing capability of
the formation 13. The various techniques for analyzing formation
pressures are well known in the art and are, therefore, of no
significance to understanding the present invention.
The measurements provided by the pressure transducer 140 at this
time will indicate whether the sealing pad 39 has, in fact,
established complete sealing engagement with the earth formation 13
inasmuch as the expected formation pressures will be recognizably
lower than the hydrostatic pressure of the borehole fluids at the
particular depth which the tool 11 is then situated. This ability
to determine the effectiveness of the sealing engagement will, of
course, allow the operator to retract the tool-anchoring member 20
and the sealing pad 39 without having to unwittingly or needlessly
continue the remainder of the complete operating sequence.
Assuming, however, that the pressure measurements provided by the
pressure transducer 140 show that the sealing pad 39 is firmly
seated, the operator may leave the formation-testing tool 11 in the
position shown in FIGS. 6A and 6B as long as it is desired to
observe as well as to record the pressure measurements. As a
result, the operator can determine such things as the time required
for the formation pressure to reach equilibrium as well as the rate
of any pressure increase and thereby obtain valuable information
indicative of various characteristics of the earth formation 13
such as permeability and porosity. Moreover, with the illustrated
embodiment of the tool 11, the operator can readily determine if
collection of a fluid sample is warranted.
Before continuing with a description of a complete testing
operation it is believed appropriate to now consider the details of
the present invention. The significance of the present invention
will be best understood with the performance of the new and
improved fluid-admitting means 10 while obtaining a pressure
measurement or fluid sample is compared to the performance of
prior-art formation testers with conventional filtering members.
Typically, these prior-art filter members have been an elongated
tubular member having only a plurality of narrow slits of a uniform
width which are disposed either longitudinally along the tubular
member or circumferentially around the member. U.S. Pat. No.
3,352,361 is an example of this previous practice. Alternatively,
either porous members or finely-meshed screens of a conventional
design have often been employed as described, for example, in U.S.
Pat. No. 3,653,436. In any case, these prior-art tools have
employed conventional filters having only uniformly-sized filter
openings which are customarily sized as dictated by the particular
size of loose formation particles which were expected to be
encountered during a given operation.
It has been found, however, that when these prior-art filters are
used in soft formations, the pressure drop across the filtering
element and the accumulated formation particles will often become
so excessive that a fluid sample simply cannot be obtained in a
reasonable period of time. This is easily understood when a
prior-art testing tool such as shown in U.S. Pat. No. 3,653,436 is
considered. As shown in FIG. 5 of that patent, fluids entering the
nose of the sampling tube will be divided into a number of fluid
paths, with the shortest path being through the first opening in
the filter screen at the forward end of the sampling tube and the
longest path theoretically being through the sampling tube and out
the rearwardmost opening in the screen. In actuality, however, it
has been found that by virtue of the additional flow resistance
imposed by the tightly-packed column of finely-divided sand
particles which will be trapped in the sampling tube, most, if not
all, of the flow will be through the forwardmost openings in the
filter screen. Thus, since, at best, little or none of the flow
will be through the rearward portions of the screen, the overall
flow rate will be drastically curtailed. It should be noted in
passing, however, that in this situation, it is unlikely that the
filter screen will be entirely plugged by mudcake since any mudcake
initially entering the sampling tube is typically concentrated at
the rearward end of the tube and held there by the column of sand
since the mudcake particles are too large to pass through filter
openings small enough to retain the sand particles. Experience has
shown, however, that if the screen openings are slightly oversized
so that some sand grains will pass through the front openings, it
is not at all uncommon for the sand to gradually erode the filter
screen to the point that the screen is no longer effective. Thus,
enlargement of the openings to improve the flow rate will often
result in rapid failure of the filter.
A more-serious problem is encountered, however, when a prior-art
testing tool equipped with a conventional filter having very narrow
slits is used to test a fairly competent or hard formation. In this
situation, the usual result will be that the mudcake entering the
sampling tube will swirl around inside of the tube so that the
internal or inlet face of the filter screen will be quickly coated
with the mudcake particles thereby plugging the narrow filter
openings. Heretofore, the only practical solution to this problem
has been to use a screen with the largest-possible openings that
will hopefully still trap any loose formation materials which might
be encountered. This obviously poses a problem where formations
composed of different degrees of hardness or competency are
expected to be encountered during a multi-formation testing
operation such as is capable of being performed by the tool 11.
Thus, if the filter openings are too large, sand will easily pass
through the filter screen when unconsolidated formations are
tested. On the other hand, if the screen openings are too small,
they will be easily plugged by mudcake when hard formations are
tested.
The practice of the methods of the present invention as well as the
new and improved fluid-admitting means 10 avoids these several
problems, however. Accordingly, as best seen in FIGS. 7 and 8,
somewhat-simplified enlarged views are respectively shown of the
new and improved fluid-admitting means 10 at successive moments
during the initiation of a test of an incompetent earth formation,
as at 13, which is primarily composed of extremely-fine particles
of sand and the like. At the time illustrated in FIG. 7, the
various elements of the tool 11 have just been placed in their
respective positions as previously described by reference to FIGS.
6A and 6B. Thus, as previously discussed, upon advancement of the
fluid-admitting member 42 into the formation 13, the plug of
mudcake 142 in the nose of the fluid-admitting member will be
impelled from the wall of the borehole 12 into the tubular member
and its interior will be quickly filled with the loose formation
materials 138 that are correspondingly displaced into the
fluid-admitting member as it penetrates the formation.
As illustrated in FIG. 7, since the plug of mudcake 142 from the
wall of the borehole 12 enters the fluid-admitting member 42 ahead
of the inrushing formation materials 138, the mudcake will, of
course, be carried to the rear of the tubular member as the valve
member 52 is moved to the rear of the filter member 66. However,
instead of the mudcake plug 142 coming to rest at the rear of the
fluid-admitting member 42 as has been the case with prior-art
testing tools, the mudcake will be capable of passing through the
rearward slits 143 in the screen 66. As will be subsequently
described, however, the uniquely-arranged filter member 66 will
trap the incoming sand particles so as to quickly form a compacted
column of these particles, as at 138.
To accomplish this, the filtering member 66 of the new and improved
fluid-admitting means 10 is selectively arranged so that at least
the rearwardmost filter openings or slits 143 are individually
wider than the forwardmost openings or slits 144. If desired, the
intermediately-located slits, as at 145, in the filtering member 66
also can be selectively sized to have a width somewhat less than
the width of the rear slits 143 but slightly greater than the width
of the forward slits 144. This can, of course, be accomplished in
different manners. For example, as shown by the preferred
embodiment in FIGS. 7 and 8, the several filter openings are
respectively arranged as circumferentially-oriented elongated slits
which are disposed in multiple sets of two or three slits around
the filter member 66, with the several sets being distributed along
almost the full length of the filter member and respectively sized
or incrementally graduated so that the rearwardmost slits, as at
143, are selectively wider than the forwardmost slits, as at 144.
Alternatively, as shown in somewhat of an exaggerated form in FIG.
9, the filter member 66' could also be arranged with a plurality of
elongated longitudinally-oriented slits spaced uniformly around the
circumference of the filter member and tapered or progressively
graduated so as to have relatively-wide rear portions, as at 143',
and relatively-narrow forward portions, as at 144'.
In either manner, during the practice of the methods of the present
invention with the tool 11, mudcake, as at 142, which enters the
fluid-admitting member 42 at the very outset of the testing
operation is capable of freely passing through the enlarged
rearward slits 143 (or the rear slit portions 143') and on into the
flow line 67. Therefore, as shown in both FIGS. 7 and 9, by virtue
of the new and improved methods and apparatus of the present
invention mudcake, as at 142, is effectively purged from the
interiors of the fluid-admitting member 42 and the filtering member
66 so as to eliminate this mudcake as a source of possibly-plugging
materials such as frequently occurs during the testing of
fairly-competent formations, as at 14, in FIG. 9.
It must be recognized, however, that the presence of the enlarged
filter openings 143 (or the rearward slit portions 143') presents a
potentially-serious problem where the formation, as at 13, is
substantially composed of unconsolidated fine materials such as the
sand particles 138. As previously discussed, unless the flow of
such fine particles into the fluid-admitting member 42 is quickly
halted, the isolated wall portion of the unconsolidated formation,
as at 13, will be rapidly eroded away to the extent that the
sealing pad 39 will no longer be in sealing engagement with the
wall of the borehole 12.
Accordingly, as a further significant aspect of the inventive
concept of the new and improved methods and apparatus disclosed
here, the rear filter openings 143 (or the rearward slit portions
143') are selectively sized so that once a significant number of
the rapidly-inrushing sand particles, as at 138, have entered the
fluid-admitting member 42, these fine particles will be capable of
quickly and reliably bridging the rear openings. This bridging
action should, of course, occur by the time the fluid-admitting
member 42 is fully extended. Once this bridging occurs, the
compacted column of collected sand grains 138 will thereafter serve
as an auxiliary filtering medium which will at least significantly
reduce, if not completely block, further fluid flow through at
least the rearwardmost filter slits 143 (as well as the rearward
slit portions 143'). It will, of course, be appreciated that the
narrower forward slits 144 (as well as the forward slit portions
144') must be selectively sized to positively retain sand particles
of a given size under even relatively-high flow rates. On the other
hand, although the wider rearward slits 143 (as well as the rear
slit portions 143') are sufficiently larger than the forward slits
144 (as well as the front slit portions 144') so as to easily pass
mudcake particles at high flow rates, these rearward slits and slit
portions cannot exceed a particular width which will reliably
create rapid bridging of the entrapped sand particles 138 once the
increasing pressure drop across the column of sand particles has
effected a significant reduction in the flow rate of fluids passing
through these rear slits and slit portions.
To understand the operation of the new and improved fluid-admitting
means 10 of the present invention, a description of fluid theory as
it relates to the fluid-admitting means is believed in order. With
the new and improved fluid-admitting means 10 in the position
illustrated in FIG. 7, for example, it will be recognized that if
the formation 13 contains producible connate fluids, these fluids
can enter the flow line only as fast as these fluids can pass
through the fluid-admitting member 42 and the filtering member 66.
The total flow rate of these fluids will, as a matter of course, be
directly governed by the degree of flow restriction presented by
the column of entrapped formation particles 138 and the filtering
member 66.
It will be recognized, of course, that the pressure differential
between any arbitrary point, as at 146, in the nose of the tubular
member 42 and the annular space 64 will be a constant for a given
flow situation; and that this overall pressure differential will be
a function of the total flow rate, the total restriction presented
by the filter member 66, and the total restriction of the column of
entrapped formation particles 138. Fluids entering the
fluid-admitting member 42 must, of course, divide into a number of
flow paths, as at 147-149, in order to pass through the various
openings 143-145 along the full length of the filtering member 66
before the fluids recombine in the annular space 64. Thus, for
there to be any fluid flow along the rearwardmost flow path 147,
for example, the total pressure drop of fluids flowing along that
path between the point 146 and the chamber 64 cannot exceed the
overall available pressure differential then existing between these
two locations.
The total pressure along any one of the several flow paths 147-149
is, of course, the total of each of the partial pressure drops
along that path. Thus, for the longest flow path 147, the total
pressure drop will be the summation of the pressure drop through
the entire columnar length of the entrapped particles 138 and the
pressure drop through the rearwardmost openings or slits 143 in the
filter member 66. On the other hand, the pressure drop along the
shortest path 149 will be the total of the drop through only the
first few of the trapped particles 138 and the drop through the
forwardmost openings or slits 144 in the filter member 66. This, of
course, means that for any given testing situation with an
unconsolidated formation, the entering fluids will be inherently
divided proportionally along the several flow paths 147-149, with
the flow rate along any one of these flow paths being a function of
the combined incremental pressure drops at that flow rate along the
length of the path through the column of sand grains 138 and
whichever one of the several slits 143-145 that portion passes
through. Since the overall pressure drop along each of these paths
147-149 will be the same for that particular situation, the net
result will be that a major percentage of the total flow will be
through the forward slits 144, a significant percentage of the flow
will perhaps be through the intermediate slits 145, and, at best,
only a minor percentage of the flow will be through the enlarged
rearward slits 143.
This division of the flow along the several flow paths 147-149 is,
therefore, a critical aspect of the present invention. As
previously mentioned, the rearward slits 143 must, on the one hand,
be large enough to reliably pass particles of mudcake at least when
a competent formation is being tested and, on the other hand, be
small enough to reliably effect a quick bridging of sand grains
across these slits when an unconsolidated formation is instead
being tested. This critical limitation is best achieved by sizing
the rearward slits 143 so that, with whatever overall pressure
differentials that may be reasonably experienced during the testing
of an unconsolidated formation, the compacted column of sand grains
138 will present such a substantial flow restriction that only
minimal flows can pass along the flow path 147 and pass through the
enlarged slits without disrupting the bridge of sand grains formed
across those slits.
Thus, by deliberately restricting the flow path 147 through these
rearward slits 143 (or the enlarged rear slit portions 143') in
this manner, it can be reliably assured that the flow of fluids
therethrough will be well below the critical flow rate which would
preclude either the formation or the maintenance of bridges of the
sand grains in the compacted column 138 across the rearward slits.
In other words, for a given width of the rearward slits 143 and for
a given overall available pressure differential between the point
146 and the annular space 64, a determination can be easily made
(either by empirical testing or calculations) of the maximum
allowable flow rate of fluids which can be passed safely through
these enlarged slits before sand grains of a size ordinarily
retained by the forward slits 144 will no longer bridge across the
rearward slits. Knowing this, it is, of course, simple to then
determine length of the column of sand grains 138 required to
provide a flow restriction sufficient to keep the flow rate along
the long flow path 147 well below the maximum allowable flow rate
which will be reliably supported by the sand particles bridging the
rearward slits 143.
It will, of course, be appreciated that the same criteria can be
applied to designing intermediately-located slits, as at 145, to
have an intermediate width if this is desired. There will naturally
be a proportional reduction in the restriction provided by the
compacted column of sand grains 138 since the flow path 148 goes
through a proportionately-shorter length of the column. Thus, since
this lesser restriction will result in a proportionately-greater
flow rate along the intermediate flow path 148 for a given overall
pressure differential, the intermediate slits 145 must be somewhat
narrower than the rearward slits 143 to maintain a bridge of sand
particles across the intermediate slits. This degree of refinement
is believed unnecessary, however. By way of example, with the
filter member 66 arranged generally as depicted in FIG. 7, it has
been found that three rows of the rear slits 143 each with a width
of 0.018 -inch and eight rows of slits each with a width of
0.010-inch for the intermediate and forward slits 145 and 144,
respectively, will enable the sample-admitting means 10 to
effectively function in most, if not all, testing situations and
still provide much-greater flow rates in finely-divided formation
materials than were possible with prior-art filters.
Although FIG. 9 depicts an alternative embodiment of apparatus
arranged in accordance with the principles of the present
invention, it will be noted that in the illustrated situation, the
formation, as at 14, is more competent than the formation 13. As a
result, the fluid-admitting member 42 has not been able to move
forwardly to its furtherest-possible extended position. This has,
therefore, resulted in substantially fewer sand particles entering
the flud-admitting member so that a much-higher overall flow rate
is possible than would have occurred if the fluid-admitting member
42 had been filled with such particles. In this situation, it is,
of course, quite possible that some, if not all, of any entering
sand particles will simply flow on through the rear portions 143'
of the tapered slits. The same thing would, of course, occur with
the filter member 66. Thus, should there be only a short column of
the sand particles (or none at all) captured in the filter member
66', the larger available flow area defined by the rear slit
portions 143' (or the rear slits 143) will simply result in greater
flow rates than would otherwise be possible with conventional
filters. The important thing to note here is that in the testing of
a relatively-competent formation, the unique design of the filter
66' (as well as the filter 66) with the enlarged rear slit portions
143' (or the rear slits 143) will assure the passage of most, if
not all, of the mudcake which typically lines the wall of the
borehole 12 where it traverses a permeable formation, as at 14.
Thus, regardless of which one of the filters 66 or 66' is being
employed with the new and improved fluid-admitting means 10, there
will be little or no mudcake retained in the filter member which
would otherwise be capable of plugging the filter. By virtue of the
enlarged filter openings 143 (or 143'), the mudcake will instead be
free to quickly pass on into the flow line 67 so that the interior
of the filter 66 (or 66') will remain fully open. It will, of
course, be recognized that since few if any formation particles
will be dislodged from the wall of the borehole 12 in this
situation, there will be no occasion requiring bridging of the
particles over the rearward openings 143 (or 143') to prevent
continued erosion of the isolated portion of the formation 14.
Now that the methods and apparatus of the present invention have
been fully set out, it is believed necessary only to quickly
summarize the balance of the complete operating cycle of the tool
10. Accordingly, referring again to FIGS. 6A and 6B, it will be
appreciated that once the several components of the tool 11 and the
control system 16 have moved to their respective positions shown in
these figures, the hydraulic pressure will again rise until such
time that the set line pressure switch 96 operates to halt the
hydraulic pump 84. Inasmuch as the pressure switch 96 has a
selected operating range, in the typical situation the pump 84 will
be halted shortly after the pressure-equalizing valve 74 closes and
the flow-line control valve 71 opens. At this point in the
operating cycle of the tool 11, once a sufficient number of
pressure measurements have been obtained as previously described, a
decision can be made whether it is advisable to obtain one or more
samples of the producible connate fluids present in the earth
formation 13. If such samples are not desired, the operator can
simply operate the control switches 24 and 25 for retracting the
tool-anchoring member 20 as well as the sealing pad 39 without
further ado. This freedom of action is, of course, made possible by
virtue of the flexibility of operation of the new and improved
fluid-admitting means 10 and the assurance that connate fluids can
reliably pass through the filter member 66.
On the other hand, should a fluid sample be desired, the control
switches 24 and 25 (FIG. 1) are advanced to their next or so-called
"sample" positions 29 to open, for example, a solenoid valve 150
(FIG. 3B) for coupling pressured hydraulic fluid from the
high-pressure section 116 of the set line 91 to the piston actuator
78 of the sample-chamber control valve 72. This will, of course, be
effective for opening the control valve 72 to admit connate fluids
through the flow line 67 and the branch conduit 69 into the sample
chamber 22. If desired, a "chamber selection" switch 151 (FIG. 1)
in the surface portion of the control system 16 could also be moved
from its "first sample" position 152 to its so-called "second
sample" position 153 (FIG. 1) to energize a solenoid valve 154
(FIG. 3B) for opening the sample-chamber control valve 73 to also
admit connate fluids into the other sample chamber 23. In either
case, one or more samples of the connate fluids which are present
in the isolated earth formation 13 can be selectively obtained by
the testing tool 11.
Upon moving the control switches 24 and 25 to their so-called
"sample-trapping" positions 30, the pump 84 will again be
restarted. Once the pump 84 has reached operating speed, it will
commence to operate much in the same manner as previously described
and the hydraulic pressure in the output line 87 will again begin
rising with momentary halts at various intermediate pressure
levels.
Accordingly, when the control switches 24 and 25 have been placed
in their sample trapping positions 30 (FIG. 1), the solenoid valve
94 (FIGS. 3A and 3B) will open to admit hydraulic fluid into the
retract line 92. By means of the electrical conductor 98a, however,
the pressure switch 98 is enabled and the pressure switch 97 is
disabled so that in this position of the control switches 24 and 25
the maximum operating pressure which the pump 84 can initially
reach is limited to the pressure at the operating pressure level
determined by the pressure switch 98. Thus, by arranging the
hydraulic control valve 103 to open in response to a hydraulic
pressure corresponding to this predetermined pressure level,
hydraulic fluid in the high-pressure section 116 of the set line 91
will be returned to the reservoir 86 by means of the return line
89. As the hydraulic fluid in the high-pressure section 116 returns
to the reservoir 86, the pressure in this portion of the set line
91 will be rapidly decreased to close the hydraulic control valve
100 once the pressure in the line is insufficient to hold the valve
open. Once the hydraulic control valve 100 closes, the pressure
remaining in the low-pressure section 113 of the set line 91 will
remain at a reduced pressure which is nevertheless effective for
retaining the tool-anchoring member 20 and the sealing pad 39 fully
extended.
As hydraulic fluid is discharged from the lower portion of the
piston actuator 78 by way of the still-open solenoid valve 150 and
fluid from the retract line 92 enters the upper portion of the
actuator by way of a branch line 155, the sample-chamber control
valve 72 will close to trap the sample of connate fluids which is
then present in the sample chamber 22. Similarly, should a fluid
sample have also been collected in the other sample chamber 23, the
sample-chamber control valve 73 can also be readily closed by
operating the switch 151 (FIG. 1) to reopen the solenoid valve 154.
Closure of the sample-chamber control valve 72 (as well as the
valve 73) will, of course, be effective for trapping any fluid
samples collected in one or the other or both of the sample
chambers 22 and 23.
Once the sample-chamber control valve 72 (and, if necessary, the
control valve 73) has been reclosed, the control switches 24 and 25
are moved to their next or so-called "retreat" switching positions
31 for initiating the simultaneous retraction of the tool-anchoring
member 20 and the sealing pad 39. In this final position of the
control switch 25, the pressure switch 98 is again rendered
inoperative and the pressure switch 97 is enabled so as to now
permit the hydraulic pump 84 to be operated at full rated capacity
for attaining hydraulic pressures greater than the first
intermediate operating level in the retract cycle. Once the
pressure switch 98 has again been disabled, the pressure switch 97
will now function to operate the pump 84 so that the pressure will
now quickly rise until it reaches the next operating level.
At this point, hydraulic fluid will be supplied through the retract
line 92 and the branch hydraulic line 135 for reopening the
pressure-equalizing control valve 74 to readmit borehole fluids
into the flow line 67. Opening of the pressure-equalizing valve 74
will admit borehole fluids into the isolated space defined by the
sealing pad 39 so as to equalize the pressure differential existing
across the pad before it is retracted. Hydraulic fluid displaced
from the upper portion of the piston actuator 76 of the
pressure-equalizing valve 74 will be discharged through a typical
relief valve 156 which is arranged to open only in response to
pressures equal or greater than that of this present operating
level. The hydraulic fluid displaced from the piston actuator 76
through the relief valve 156 will be returned to the reservoir 86
by way of the branch hydraulic line 130, the high-pressure section
116 of the set line 91, the still-open hydraulic control valve 103,
and the return line 89.
When the hydraulic pressure in the output line 87 has either
reached the next operating level or, if desired, a still-higher
level, pressured hydraulic fluid in the retract line 92 will reopen
the hydraulic control valve 102 to communicate the low-pressure
section 113 of the set line 91 with the reservoir 86. When this
occurs, hydraulic fluid in the retract line will be admitted to the
retract sides of the several piston actuators 21 and 41. Similarly,
the pressured hydraulic fluid will also be admitted into the
annular space 51 in front of the enlarged-diameter piston portion
49 for retracting the fluid-admitting member 42 as well as into the
annular space 62 for returning the valve member 52 to its forward
position. The hydraulic fluid exhausted from the several piston
actuators 21 and 41 as well as the piston chambers 50 and 63 will
be returned directly to the reservoir 86 by way of the low-pressure
section 113 of the set line 91 and the hydraulic control valve 102.
This action will, of course, retract the tool-anchoring member 20
as well as the sealing pad 39 against the tool body 19 to permit
the tool 11 either to be repositioned in the borehole 12 or to be
returned to the surface if no further testing is desired.
It should be noted that although there is an operating pressure
applied to the upper portion of the piston actuator 77 for the
flow-line control valve 71 at the time that the pressure-equalizing
valve 74 is reopened, a normally-closed relief valve 157 which is
paralleled with the check valve 136 is held in a closed position
until the increasing hydraulic pressure developed by the pump 84
exceeds the operating level used to retract the tool-anchoring
member 20 and the sealing pad 39. At this point in the operating
sequence of the new and improved tool 11, the flow-line control
valve 71 will be reclosed.
The pump 84 will, of course, continue to operate until such time
that the hydraulic pressure in the output line 87 reaches the upper
limit determined by the setting of the pressure switch 97. At some
convenient time thereafter, the control switches 24 and 25 are
again returned to their initial or off positions 26 for halting
further operation of the pump motor 85 as well as reopening the
solenoid valve 99 to again communicate the retract line 92 with the
fluid reservoir 86. This completes the operating cycle of the
illustrated embodiment of the tool 11.
Accordingly, it will be appreciated that the new and improved
fluid-admitting means 10 of the present invention enable the
formation-testing tool, such as that shown herein at 11, to be
operated for testing any type of formation which may be reasonably
expected to be encountered during a formation-testing operation. By
providing a filter member with selectively-larger filter openings
at the rear of the member, it is assured that a buildup of
formation particles in the sample member will not block the flow of
connate fluids through at least the rear portion of the
fluid-admitting member into the portions of the fluid-admitting
means. Thus, with the new and improved fluid-admitting means
described herein, tests may now be conducted in various types of
formations without experiencing either unduly-reduced flow rates
where a given formation is composed of exceptionally-fine,
unconsolidated sand particles or plugging of the filtering means
with mudcake or the like where a relatively-complete formation is
encountered.
While only one method and particular embodiments of apparatus of
the present invention have been shown and described, it is apparent
that changes and modifications may be made without departing from
this invention in its broader aspects; and, therefore, the aim in
the appended claims is to cover all such changes and modifications
as fall within the true spirit and scope of the present
invention.
* * * * *