U.S. patent number 3,850,241 [Application Number 05/377,983] was granted by the patent office on 1974-11-26 for high pressure jet well cleaning.
This patent grant is currently assigned to Chevron Research Company. Invention is credited to Stanley O. Hutchinson.
United States Patent |
3,850,241 |
Hutchinson |
November 26, 1974 |
HIGH PRESSURE JET WELL CLEANING
Abstract
Method and apparatus for directionally applying high pressure
jets to well liners to clean openings which are plugged with
foreign matter. High velocity jets of liquid having a velocity in
excess of 700 feet per second are jetted from jet orifices having a
standoff distance between 5 and 10 diameters of the orifice from
the openings to remove substantially all plugging material from the
openings. Apparatus for circulating foam is provided in combination
with apparatus for delivering high pressure jets. New swivels and
check valves permit rotation and reciprocation of the jet tool and
tubing string while maintaining high pressure in the apparatus.
Inventors: |
Hutchinson; Stanley O.
(Bakersfield, CA) |
Assignee: |
Chevron Research Company (San
Francisco, CA)
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Family
ID: |
26957020 |
Appl.
No.: |
05/377,983 |
Filed: |
July 10, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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274692 |
Jul 24, 1972 |
|
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150536 |
Jun 7, 1971 |
3720264 |
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Current U.S.
Class: |
166/222;
239/550 |
Current CPC
Class: |
E21B
37/08 (20130101); E21B 21/00 (20130101) |
Current International
Class: |
E21B
21/00 (20060101); E21B 37/00 (20060101); E21B
37/08 (20060101); E21b 021/00 () |
Field of
Search: |
;166/311,312,222
;175/422 ;239/DIG.13,450,536,550,101 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leppink; James A.
Attorney, Agent or Firm: Freeland, Jr.; Ralph L. Keeling;
Edward J.
Parent Case Text
This is a continuation of application Ser. No. 274,692, filed July
24, 1972, now abandoned, which application is a divisional of a
prior application Ser. No. 150,536, filed June 7, 1971, now U.S.
Pat. No. 3,720,264.
Claims
I claim:
1. Apparatus for jet washing a well liner positioned in a well
comprising first tubing means forming a well flow path from the
earth's surface to a location adjacent a well liner positioned in a
well, a source of high pressure liquid for supplying-liquid at
pressures in excess of 6,000 psi, conduit means connecting said
source of high pressure liquid to said first tubing means and jet
tool means for jetting said high pressure liquid at said well
liner, said jet tool means comprising an inner tubular member
connected to the lower end of said first tubing means and having at
least one hole in the wall thereof, a jet seat member fixedly
connected to said inner tubular member, said jet seat member having
a central internally threaded opening aligned with said hole and an
externally threaded jet body having a central opening of no greater
than 1/16th inch in diameter formed therein threadably engaged in
said jet seat member, the internal threads and the external threads
being mateable whereby said jet body may be rotated to provide
axial movement of said jet body with respect to said jet seat
member.
2. Apparatus for jet washing a well liner positioned in a well
comprising first tubing means forming a well flow path from the
earth's surface to a location adjacent a well liner positioned in a
well, a source of high pressure liquid for supplying liquid at
pressures in excess of 6,000 psi, conduit means connecting said
source of high pressure liquid to said first tubing means and jet
tool means for jetting said high pressure liquid at said well
liner, said jet tool means comprising an inner tubular member
connected to the lower end of said first tubing means and having a
hole in the side wall thereof, a jet seat member fixedly connected
to said first tubular member and having a central internally
threaded opening positioned over said hole, a second outside
tubular member concentrically arranged around said first tubular
member having a hole coaxially aligned with the hole in said first
tubular member, means connecting said second tubular member to said
jet seat member and an externally threaded jet body having a
central opening of no greater than 1/16th inch in diameter formed
therein threadably engaged in said jet seat member, the internal
threads and the external threads being mateable whereby said jet
body may be rotated to cause axial movement of said jet body with
respect to said jet seat member.
Description
BACKGROUND OF THE INVENTION
The present invention relates to cleaning openings in well liners
positioned adjacent fluid producing formations using high velocity
liquid jets and, more particularly, the present invention relates
to methods and apparatus for use in removing plugging material from
openings in oil well liners and the like with liquid jets having
velocities in excess of 700 feet per second which are directed at
the well liners through orifices having a standoff distance between
the end of the orifice and the well liner of between 5 and 10 times
the diameter of the orifice.
In the well producing art it is customary to complete an oil well
or a water well adjacent a fluid producing formation by inserting a
metallic well liner. Openings in the well liner provide passageways
for flow of fluid such as oil or water and other formation fluids
and material from the formation into the well for removal to the
surface. However, the openings which, for example, may be slots
preformed on the surface or perforations opened in the well, will
often become plugged. This problem is especially serious in areas
of viscous oil production from unconsolidated sand formations.
Since it is highly desirable to prevent sand from entering the
well, the liners used in this type of formation are often completed
with narrow longitudinal slots. The slots prevent the entry of most
of the sand with the oil, but in time they become plugged. Of
course plugging is not limited only to slotted liners but also
occurs in perforated liners even though the perforations may be
considerably larger in size than the slots. in any event, removal
and replacement of the liner is costly and is only a temporary
solution since the liner will eventually again become plugged.
Sections of recovered plugged liners have been analyzed to
determine the identity of the plugging material. Results have shown
that the plugging material is mostly inorganic. Generally, it
appears to be fine sand grains cemented together with oxides,
sulfides and carbonates. Some asphaltenes and waxes are also
present. Where water is produced, scale also seems to be present
and presents a very tough plugging material.
Many methods for cleaning openings in well liners have been
heretofore suggested. These methods include pumping a fluid between
two or more opposed washer cups until the pressure builds up
sufficiently to hydraulically dislodge the plugging material.
Explosives such as primer cord (string shooting) have been used to
form a high energy pressure shock wave to hydraulically or
pneumatically blow the plugging material from the perforations. The
disadvantages of these two methods are that the energy is applied
nondirectionally to the liner and it always takes the path of least
resistance. The use of these methods generally results in opening
only one or two perforations out of a perforation row containing
from 16 to 32 perforations.
Other prior art methods of cleaning the openings in liners include
the use of mechanical scratches and brushes to cut, scrape or gouge
the plugging material from the perforations. There are many
disadvantages of these approaches. For example, the knives or wires
in the brushes must be very thin to enter the slotted perforations
which generally measures only 0.040 to 0.100 inches wide and,
therefore, the knives and wires are structurally weak. Thus an
insufficient amount of energy is generally applied to really unclog
the perforations. Furthermore, the cleaning tool must be indexed so
that the knives or wires actually hit a perforation. Since only 3
percent of the liner surface area is generally perforated, the
chances are not favorable for contacting a perforation.
The use of chemicals such as solvents and acids have been used to
dissolve the plugging materials. There are major disadvantages to
the chemical approach. Thus the material plugging the perforations
varies widely even in a well which requires a number of different
chemicals to solubilize them. The combinations of plugging
materials often inhibits the reaction of the chemicals. For
example, an oil film will prevent an acid from dissolving a scale
deposit and a scale deposit will prevent a solvent from being
effective in dissolving heavy hydrocarbons. The chemicals cannot
always be selectively placed where they are needed due to varying
permeabilities encountered in a well bore and/or they dissolve the
material in a few perforations and then the chemicals are lost into
the formation where they can no longer be effective in cleaning the
perforations.
Jetted streams of liquid have also been heretofore used to clean
openings. The use of jets was first introduced in 1938 to
directionally deliver acid to dissolve carbonate deposits.
Relatively low velocities were used to deliver the jets. However,
this delivery method did improve the results of acidizing. In about
1958 the development of tungsten carbide jets permitted including
abrasive material in a liquid which improved the ability of a fluid
jet to do useful work. The major use of abrasive jetting has been
to cut notches in formations and to cut and perforate casing to
assist in the initiation of hydraulically fracturing a formation.
The abrasive jetting method requires a large diameter jet orifice.
This large opening required an unreasonably large hydraulic power
source in order to do effective work. The use of abrasives in the
jet stream permitted effective work to be done with available
hydraulic pumping equipment normally used for cementing oil wells.
However, the inclusion of abrasive material in a jet stream was
found to be an ineffective perforation cleaning method in that it
enlarged the perforation which destroyed the perforation's sand
screening capability.
There is, therefore, still a need for a method of cleaning openings
in a well liner which results in cleaning substantially the entire
opening and which is a practical and relatively easy operation to
perform. Further, there is need for a method of cleaning openings
in such liners which does not destroy or alter the openings or
damage the liner.
BRIEF DESCRIPTION OF THE INVENTION
Briefly, the present invention provides a method and apparatus for
directionally applying a high pressure jet to a well liner to clean
openings in the liner which are plugged with foreign matter. High
pressure liquid jets having a velocity in excess of 700 feet per
second are jetted at the liner from jet orifices having a standoff
distance less than 10 times the diameter of the orifice to remove
substantially all plugging material from the liner openings.
Apparatus for concurrently circulating foam is provided in
combination with the apparatus used to deliver the high pressure,
high velocity jets. The foam may be used before, with or after the
jets to remove material from the well. New swivels and check valves
permit rotation and reciprocation of the work string in the well at
high pressure conditions to permit directional application of the
high kinetic energy in the jet.
In one aspect the present invention provides a method of jet
cleaning openings in a well liner positioned adjacent a fluid
producing formation. A flow path is formed from the earth's surface
to a location adjacent a liner having plugged openings and high
pressure liquid is flowed down such flow path. A jet is formed of
the liquid adjacent the liner and is directed at the liner with a
velocity of at least 700 feet per second to clean openings in the
liner. The jet is formed from an orifice and is directed at the
liner from a standoff distance of not more than 10 times the
diameter of the jet as it leaves the orifice. It has been found
that relatively small diameter orifices which produce jets of
1/16th of an inch or less are useful in the present invention. Thus
a preferred orifice diameter for use in accordance with the
invention is 1/32nd of an inch. The use of small diameter jets is
very advantageous in that liquid volume requirements are lowered,
thus lowering horsepower requirements and reducing the possibility
of formation damage in low pressure formations caused by liquid in
the well overpowering the formation.
In another aspect, the method of the present invention provides for
jet cleaning openings in a well liner which openings have become
plugged from residual products from producing petroleum or other
fluids which includes the use of foam in conjunction with the high
pressure, high velocity liquid jet. Thus a first flow path from the
earth's surface to a location adjacent a liner having plugged
openings is formed and high pressure liquid is flowed down it and
jetted at the well liner. A second flow path is also formed from
the earth's surface down the well and terminates at a location
below the terminal end of the first flow path in the well. The
second flow path provides a path for flowing foam down the well to
assist in removing matter from the well. This may occur either
before, during or after the well has been cleaned with high
pressure jets in accordance with the present invention. Thus foam
may be used to remove sand from the well prior to jet cleaning the
liner. Foam may also be circulated during jetting to remove the
jetted liquid from the well to thus keep the well drawn down to
prevent the jetted liquid from entering the formation. Foam is also
useful after the jet cleaning operation to remove debris and liquid
from the well.
The present invention provides apparatus for jet washing a well
liner positioned adjacent a fluid producing formation to clean
openings in a well liner which have become plugged during
production from the well. A first tubing means forms a well flow
path from the earth's surface to a location adjacent the well
liner. The first tubing means has rotatably connected thereabout a
rotating swivel. A source of high pressure liquid is connected to a
flow path through the rotating swivel. An opening in the tubing
means communicates with the flow path in the rotating swivel to
provide a flow path into the interior of the tubing for the high
pressure liquid. A jet tool is connected to the end of the tubing
means adjacent the liner and is used to jet the high pressure
liquid at openings in the liner to clean them.
In a more particular aspect the apparatus of the present invention
is further characterized by a second tubing means arranged
concentrically around the first tubing means. The second tubing
means extends from the earth's surface to a location adjacent a
liner in the well. A foam surface is provided with conduit means
connecting it with the second tubing means to provide foam for use
in circulating in the well.
In another aspect the present invention includes a rotating swivel
comprising a housing member having a central opening through its
entire length with a mandril having a central opening through its
entire length positioned in the central opening of the housing
member. Means are provided to rotatably mount the mandril in the
central opening of said housing member. An opening is formed
intermediate the ends of said mandril to form a flow path from the
outside of the mandril into the central opening of said mandril.
Port means in said housing member communicate with the opening in
the mandril. Means are provided for connecting a foam conduit to
the port means.
In still another aspect, this invention is directed to a check
valve useful to permit flow in one direction and prevent flow in
the opposite direction in an annular passageway formed by two
concentrically arranged tubing members. Thus a first tubing member
having a central opening through its entire length and a second
similar tubing member of larger diameter are concentrically
arranged to form an annular passageway between the tubing members.
A resilient member having one end mounted on the exterior of the
first tubing member and the other end flared outwardly from the
first tubing member to engage the inside wall of the second tubular
member provides flow control in the annular space between the
tubing members.
This invention also provides a jet tool for use in directing high
velocity liquid jets at a well liner. The jet tool includes an
inner tubular member having at least one hole in the wall thereof
and a jet seat member fixedly connected to the tubular member and
having a central opening aligned with the hole in the tubular
member. A jet body having a central opening formed therein is
threadably engaged in said jet seat member to provide a jetting
orifice for directing a high pressure jet.
In a more specific aspect the invention is directed to a jet tool
which is useful both to jet clean a liner and to simultaneously
provide foam for circulation in the liner annulus. An inner tubular
member having a hole in the side wall thereof is provided with a
jet seat having a central opening positioned over the hole. A
second outside tubular member is connected to the jet seat and is
concentrically arranged around the first tubular member. The second
tubular member also has a hole which is coaxially aligned with the
hole in the first tubular member. A jet body means having a central
opening therein is seated in said jet seat member to permit jetting
of liquid from the interior of the first tubular member through to
the outside of the second tubular member. Foam can be circulated in
the annulus between the two tubular members past the jet seat
member before, during or after liquid is being jetted through the
jet body.
PRINCIPAL OBJECT OF THE INVENTION
The principal object of the present invention is to provide a
method and apparatus for directionally applying high velocity, high
energy liquid jets to clean plugged well liners. Further objects
and advantages of the present invention will become apparent from
the drawings and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view, partially in section, illustrating
the preferred embodiment of apparatus assembled in accordance with
the present invention positioned in a well;
FIG. 2 is an elevation view, partially in section, and illustrates
in greater detail the high pressure rotating swivel of the
preferred embodiment of apparatus;
FIG. 2A is a sectional view taken at line 2A--2A of FIG. 2;
FIG. 3 is an elevational view, partially in section, and
illustrates the safety clamp and rubber tubing stripper of the
preferred embodiment of apparatus;
FIG. 3A is a sectional view taken at line 3A--3A of FIG. 3;
FIG. 3B is a layout view of a portion of the apparatus illustrated
in FIG. 3;
FIG. 4 is an elevation view, partially in section, and illustrates
the elevators and rotating head of the preferred embodiment of
apparatus;
FIG. 5 is an elevation view, with portions broken away for clarity
of presentation, and illustrates the power rotating swivel of the
preferred embodiment of apparatus;
FIG. 6 is an elevation view with portions broken away for clarity
of presentation and illustrates the foam swivel of the preferred
embodiment of apparatus;
FIG. 6A is a section view taken at line 6A--6A of FIG. 6;
FIG. 7 is an elevation view, partially in section, and illustrates
the wellhead and tubing slips of the preferred embodiment of
apparatus;
FIG. 8 is a sectional elevational view illustrating the concentric
check valve of the preferred embodiment of apparatus;
FIG. 8A is a sectional view taken at line 8A--8A of FIG. 8;
FIG. 9 is a sectional view and illustrates the crossover connection
of the preferred embodiment of apparatus;
FIG. 10 is a sectional view and illustrates the jet tool of the
preferred embodiment of apparatus;
FIG. 10A is a sectional view taken at line 10A--10A of FIG. 10;
FIG. 11 is an elevation view with portions broken away for clarity
of presentation and illustrates the drop ball valve and bit of the
preferred embodiment of apparatus; and
FIG. 12 is a detail view of the jet body and a well liner showing
standoff distance in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is an elevation view, partially in section, and illustrates
the preferred embodiment of apparatus assembled in accordance with
the present invention positioned in a well. FIG. 1 thus illustrates
the overall view of the preferred apparatus of the present
invention. FIGS. 2 through 12 illustrate portions of the preferred
apparatus in greater detail.
In FIG. 1 a well is shown drilled into a fluid producing formation
12 from the earth's surface 14. The upper portion of the well is
cased with a suitable string of casing 16. A liner 18 having
suitable openings 19 is hung from the casing and extends along the
producing formation 12. The openings which may be slots or
perforations permit flow of formation fluids from formation 12 into
the interior of the well. As the formation fluids are produced, the
openings in the slotted liner 18 tend to become plugged by
depositions of scale, asphalt, clay and sand. The plugging material
in the various slots at different elevations in the liner will vary
in composition and, depending on the composition, will be more or
less difficult to remove in order to reopen the slots. As the slots
become plugged production from the well will tend to decline. Once
it has been determined that the openings 19 in the well liner 18
have become plugged to the extent that cleaning is required for
best operation of the well, the apparatus shown in FIG. 1 is
assembled to accomplish such cleaning.
The present invention utilizes high velocity jets of liquid to
clean plugged openings in well liners. The high kinetic energy of
the jet is directionally applied to the openings by means of a
rotatable and reciprocal jetting apparatus. Thus the apparatus of
the present invention can be rotated while jetting high pressure
liquid jets at the liner. Additionally, the present apparatus may
be concurrently raised or lowered in the well to provide for
overall coverage of the liner by the jetted liquid.
The use of high velocity jets, i.e., above 700 feet second, permits
maximum energy release to clean the openings of a liner with
minimum volume of liquid. This is an important feature of the
invention since accumulation of large amounts of liquid in the well
can overpressure the producing formation and cause the liquid to
flow into the formation causing formation damage. Additionally, the
reduced volume of liquid made possible by the present invention
greatly reduces horsepower requirements to move and jet the
liquid.
In accordance with the invention a method of jet cleaning a well
liner is provided by flowing high pressure liquid down a flow path
from the earth's surface to a point adjacent the plugged openings
in the liner. A jet of liquid is formed by passing the liquid
through a small diameter jet orifice at a velocity of at least 700
feet per second and directing the jet of liquid at the liner to
clean the slots thereof from a distance of between 5 and 10
diameters of the orifice. The jet is rotated and reciprocated in
the liner to insure substantially complete coverage of the surface
of the liner. This rotating and reciprocating is accomplished while
the jet is simultaneously jetted against the liner to thereby clean
the slots of the liner.
In accordance with one form of the invention, a second flow path in
addition to the jet liquid flow path is concurrently formed from
the earth's surface to a point below the orifice forming the jet.
This second flow path is used to inject a circulating fluid, such
as foam, in the well either before, during or after the jet
cleaning. In the preferred form, the flow paths are arranged
concentrically. Thus the jetting liquid is injected down a small
diameter tubing and the foam is injected down the annulus between
such small diameter tubing and a larger diameter tubing
concentrically arranged thereabout. The use of foam in connection
with the high pressure jets is especially advantageous to remove
material from the well during the operation. It is particularly
helpful in low pressure formations in that the liquid which has
been jetted at the liner and is collecting in the well may be
circulated to the surface by the foam. Further, any sand or other
material in the well may also be circulated to the surface with the
foam. Methods and apparatus for preforming and circulating foam are
disclosed and claimed in U.S. Pat. Nos. 3,463,231; 3,486,560; and
3,559,739. The disclosure of such patents is incorporated herein by
reference.
In order to facilitate the understanding of the present invention
the preferred embodiment of apparatus will be generally discussed
from top to bottom in relation to FIG. 1. The apparatus of the
present invention is hung above and in the well by means of
elevators 20 and suitable long links 22 and 24. The links 22, 24
are connected to a traveling block (not shown) on the conventional
hoist which is utilized to move the elevators up and down thereby
raising or lowering the apparatus of the present invention.
A conventional plug valve indicated generally by the number 26 is
attached to the upper end of small diameter tubing 28. The plug
valve operates to close off the upper end of the tubing 28. The
valve 26 may be opened to insert objects in the interior of the
tubing string if one desired. A high pressure rotating swivel 30
having an inner flow path therethrough is rotatably connected on a
tubing means between tubing 28 and tubing 32. A high pressure
liquid source is connected through a suitable conduit 34 to the
high pressure rotating swivel 30 to provide a flow path for high
pressure liquid into the tubing string which forms a first flow
path down the well.
A larger diameter tubing 36 is concentrically arranged around inner
tubing 32 below the high pressure rotating swivel 30. The upper end
of the larger diameter tubing 36 is coupled to a rubber tubing
stripper 38 by collar 40. The rubber tubing stripper 38 contains an
inner rubber stripper which seals off the upper end of tubing 36
against tubing 32. A rotating clamp indicated generally as 42 is
connected between the inner tubing string 32 and the outer tubing
string 36 to cause the tubing strings 36 and 32 to be rotated
together. A rotating head 44 is seated on elevator 20 to permit
rotation of the dual tubing strings 36, 32 while the tubing strings
are being hung from elevator 20. Although it is recognized that a
number of segmented sections are connected together to form tubing
string, the inner and outer tubing strings in the present invention
will be numbered 32 and 36, respectively, to facilitate description
of the invention. A conventional power rotating swivel 46 is
connected onto outer tubing string 36 so that the tubing string may
be rotated as desired. As noted, rotating of outer tubing string 36
causes inner tubing string 32 to also rotate because of the
connector clamp 42. The annulus formed between the two concentric
tubing strings 32, 36 forms a second flow path down the well. A
foam swivel 48 is rotatably connected to the outer tubing string
36. A foam source is connected through a suitable conduit 50 to the
foaming swivel 48 to provide foam for flow down the well in the
annulus between outer tubing 36 and inner tubing 32.
The outer tubing string 36 below the foaming swivel 48 can be hung
at the wellhead 52 by means of slips 54. The inner tubing string 32
is run in compression and is supported on a crossover connection
located near the jet tool. Stripper rubber 56 on the interior of
the wellhead 52 prevents flow of fluid through the wellhead
adjacent the outer tubing 36. Flow out from the well annulus 13
occurs through either blooie line 58 or kill line 60. Each of these
lines is provided with appropriate valves to control flow into or
out of the casingtubing annulus.
The concentric tubing strings 36 and 32 extend down the well to a
position adjacent the openings in a liner that are to be cleaned. A
concentric string check valve indicated generally as 62 is located
in the annulus between inner tubing 32 and outer tubing 36
preferably at a depth near the earth's surface but far enough down
so that the liner can be washed up without pulling the check valve.
Thus the check valve would be near the surface when the jetting
operation is completed. The concentric check valve 62 permits
downward flow of fluid through the tubing-tubing annulus but
prevents backflow of fluids up this annulus. A jet washing tool
indicated generally as 64 is connected to the lower end of the
tubing strings. A suitable crossover connection 66 is utilized to
connect the inner tubing string 32 with the jet washing tool 64. A
closeable drop ball valve 67 is used to control flow through the
lower end of tubing 32. One or more jets 68 are connected on jet
tool 64 and provide a flow path for high pressure fluid from the
interior of inner tubing 32 to the wall of the well liner. A sand
bit 70 is connected to the lower end of the jet tool to assist in
cleaning out sand and to provide mechanical centralization of the
jet tool. The centralizing provided by the bit 70 is particularly
important while the jet tool 64 is being run (lowered) into the
well. If the jet tool 64 were not so centralized there is danger of
the jets 68 being sheared off while the tool is being run. The jet
tool 64 is hydrolically centralized during the jetting operation by
the balanced placing of the jets 68. A suitable downwardly opening
flapper valve contained in sub 72 permits downward flow of liquid
through bit 70 and prevents backflow of fluid up the interior of
the jet tool and tubing strings.
In accordance with the invention then, a flow path for high
pressure liquid is provided from the surface of the earth to a
position in a well adjacent a liner having openings which are to be
jet cleaned. High pressure liquid is jetted against such a liner
from a distance related to the diameter of the orifice used to form
the jet. It has been found that to insure efficient and
satisfactory opening of the closed slots or perforations that the
jetted liquid must have the velocity of 700 feet per second and be
directed against the liner from a distance between 5 and 10
diameters of the orifice used to form the jet. It has been
determined that a standoff distance of more than 10 diameters is
too great to insure substantially 100 percent cleaning of difficult
material likely to be found in the openings of a well liner. When
the standoff distance is reduced to less than 5 diameters the jet
bodies are subject to undesirable errosion by splashback. A high
pressure rotating swivel utilized on the tubing which forms the
flow path for high pressure jet liquid permits rotation of the
jetting string during jetting operations. The jetting string may
also be reciprocated in the well during such operations and by
combining a preplanned program of rotation and reciprocation
substantially complete coverage of the liner with the high pressure
jet can be obtained.
A concentric outside tubing string is also provided and forms an
annular flow path from the surface to a point below the jet washing
tool so that a circulating medium, such as foam, can be injected
and circulated as desired before, during or after the high pressure
jet washing operation. Since the foam flow path terminates below
the jet tool foam may be circulated up past the jet tool to free it
should it become sanded in. Thus much closer tolerances between the
tool and the casing are possible than would ordinarily be the case.
The outer tubing is provided with a foaming swivel which permits
injection of foam to the tubing annulus during rotation and
reciprocation of the tubing strings. The tubing strings are locked
together so that rotation and reciprocation occur simultaneously in
the tubing strings.
The apparatus of the present invention will be discussed in greater
detail with reference to FIGS. 2 - 12 and the various sections
thereof. Briefly, FIGS. 2 and 2A show the concentric rotating
swivel; FIGS. 3 and 3A show the safety clamp and rubber tubing
stripper; FIG. 4 shows the elevators and rotating head; FIG. 5
shows the power rotating swivel; FIGS. 6 and 6A show the foam
swivel; FIG. 7 shows the wellhead and tubing slips; FIGS. 8 and 8A
show the concentric check valve; FIG. 9 shows a suitable crossover
connection; FIGS. 10 and 10A show the jet tool; FIG. 11 shows the
drop ball valve and the bit; and FIG. 12 shows standoff distance in
accordance with the invention.
The high pressure liquid is introduced into the inner tubing string
32 as shown in FIGS. 2 and 2A by means of a high pressure rotating
swivel indicated generally by the number 30. A mandril section 80
is rotatably mounted in a central opening of a housing member 82.
The mandril 80 has a longitudinal flow path through its entire
length and has suitable pipe threads at both ends for connecting
into tubing string 32 at the lower end and plug valve 26 at the
upper end. An opening such as holes 83, is formed in the
intermediate portion of the mandril 80 to permit communication
through the mandril to the interior of the tubing string 32. The
holes 83 are aligned with the port 84 forming a flow path through
the side wall of housing member 82 of the rotating swivel. The
total area of the hole or holes 83 should be at least as great as
the cross-sectional interior flow area of the tubing string 32.
Tubing 34 connects flow path 84 of the housing 82 to a source of
high pressure liquid. Thus the high pressure liquid has a flow path
into the interior of tubing 32 through the port 84 and the annular
chamber 85 formed in the inner wall of housing member 82 and thence
through the holes 83 in the mandril 80. A spacer insert 86 having a
plurality of holes 87 aligned with holes 83 of the mandril is used
to space fluidtight packing 88 and 89 above and below,
respectively, the high pressure liquid entry system. A shoulder 90
in the interior of housing 82 forms an abutment for the upper
packing 88 which, in turn, supports spacer 86 and lower packing 89.
A packing retainer nut 91 is threadably engaged in the lower
portion of housing 82 and is used to compress the packing a
suitable amount. A lock bolt 92 engages through a hole in the
packing retainer nut and engages against the housing 82 to lock the
packer retainer nut in suitable position. O-ring seals 93 and 94
assist in packing off the mandril and the housing member.
The tubular mandril 80 is rotatably mounted in the rotating swivel
by suitable ball bearing sets 95 and 96. Grease fittings 97 and 98
are useful to lubricate the ball bearings. A relief hole 99 is
formed in the housing member 82 and communicates with the inner
chamber thereof between the major packing 88 and the upper o-ring
93. In this manner if the packing fails the high pressure liquid
can escape through the relief hole 99 without damaging the ball
bearings. A second relief hole 81 is also formed in the housing 82
and communicates with the inner chamber thereof between the lower
major packing 89 and lower o-ring 94 to serve a similar function
for the lower portion of the rotating swivel.
FIG. 3 and FIG. 3A illustrate the concentric string clamp 42 and
the concentric string stripper assembly 38. FIG. 3B is a view of
the upper portion of the clamp 42 in an opened position. Inner
tubing string 32 extends through the clamp 42 and the stripper
assembly 38. A suitable collar 40 connects larger diameter tubing
36 with a bell sub 100. The bell sub 100, in turn, is connected by
collar 101 to cap 102 and collar 103 which has an opening to
slidably engage tubing 32. Stripper rubber 104 prevents flow
between the outside of tubing 32 and collar 103. In this manner,
the upper end of the annular chamber 105 between the inner tubing
32 and the outer tubing 36 is closed off.
The inner tubing string 32 and the outer tubing string 36 are
clamped together for rotational and reciprocal movement by
concentric string clamp 42. A pair of gripping members 106 and 108
are swingably mounted on hinge pin 110. The gripping members are
engaged around tubing 32 and locked in place by means of bolt 112
and nut 114. A sleeve 116 is formed at the end of member 108 and a
corresponding sleeve 118 is fixedly connected by bar extension 120
to the outside tubing string 36 by means of collar 40. A locking
pin 122 is inserted through the axially aligned holes in the
sleeves 116 and 118 to lock the inner tubing string 32 and the
outer tubing string 36 together for rotation.
FIG. 4 illustrates the elevators 20 and the rotating head 44. The
elevators are suspended from a suitable hoist by means of links 22
and 24. The links are U-shaped and the back portion of each link is
not shown in the drawing. The links 22 and 24 are held under
flanges 123 and 125, respectively, and maintained in place by pins
127 and 129 which engage between the upper flanges 123 and 125 and
lower flanges 131 and 133. Swinging doors 135 and 137 open to
permit easy insertion and removal of tubing into the elevators. The
rotating head 44 sits on top of the main deck 139 of the
elevators.
The rotating head 44 is provided with a central opening to freely
receive the inner and outer tubing strings. This permits the tubing
string to be rotated while being held in the elevators. More
specifically, an outer case member 141 rests on the upper surface
139 of the elevators, a bearing support member 143 is threadably
engaged into case member 141 and a cap member 145 is connected by
bolts 147, 149 to the cap member. Each of these three members is
provided with a central opening to receive a mandril section 151.
The ends of the mandril section are threadably connected to the
outer tubing string 36. This arrangement cooperating with the inner
tubing 32 continues annulus 105 which forms the foam flow path down
the well through the rotating head. Mandril section 151 includes an
annularly extending shoulder portion 153 which engags into a
recessed portion 155 of bearing supporting member 143. An annularly
extending thrust bearing 157 provides a running surface between
shoulder 153 and the bearing support member 143. Suitable annular
packing rings 159 and 161 are provided to seal off the bearing
chamber.
FIG. 5 illustrates in greater detail a power rotating sub 46.
Generally stated the function of the rotating power sub is to
rotate outer tubing string 36. A suitable power rotating sub for
use in the present invention is the Bowen PS-2 power sub described
and illustrated in the 1968-69 Composite Catalog of Oil Field
Equipment and Services, at pages 636 and 637. Briefly, the power
rotating sub utilizes a hydraulic motor 202 having motor manifold
204 to drive a main gear (not shown) inside of gear box 206.
Telescoping torque reins 208 and 209 extend from the main gear box
body 206. The power rotating sub permits carrying the annular flow
path 105 through the sub.
FIGS. 6 and 6A illustrate in detail foam swivel 42. The foam swivel
42 permits injection of foam through conduit 50 into the annulus
105 between the inner tubing string 32 and the outer tubing string
36. A foaming swivel is rotatably mounted with respect to the
tubing strings so that the tubing strings may be rotated inside of
the foam swivel 42.
More specifically, the foam swivel includes an outer housing 164
which has a central opening therein to receive a mandril section
166. The mandril section 166 has a central opening through its
entire length and is threadably connected at either end with outer
tubing string 36 to provide a continuation of annular flow path 105
through the foam swivel 42. Two sets of annular tapered roller
bearings 168 and 170 are provided above and below a foam entry port
172 in outer housing 164. Roller bearings 168 are packed off above
by annular packing ring 174 and below by annular o-rings 176 and
178. The lower annular bearing 170 is packed off below by annular
packing ring 180 and above by o-rings 182 and 184. Grease openings
186, 188, 190 and 192 are provided in the outer case 164 for
lubricating the bearings. Upper cap collar 194 and lower cap collar
196 threadably engage in the outer housing 164 to maintain the
bearings in place. Mandril section 166 is provided with an opening
such as one or more holes 198 intermediate its length. These holes
198 are positioned adjacent an annularly extending recess 200 in
the inner wall of housing members 164. Entry port 172 communicates
with the annular chamber 200 so that fluid injected into the
chamber through conduit 50 will enter the interior of the mandril
through the annular chamber 200 and the holes 198 in the mandril.
In this manner foam may be injected into the annular space 105
between the tubing strings 32, 36. This annular conduit provides a
flow path for foam down the well.
FIG. 7 shows in more detail the tubing hanging slips 54 and the
wellhead 52. The tubing hanging slips 54 are adapted to engage and
disengage outer tubing string 36 to hang the tubing string 36 in
the well. Handles 211 and 213 are used to engage and disengage the
jaws 215 and 217 of the slips against the tubing string 36. An
annularly extending stripper rubber 56 seals off the annular space
13 between the casing 16 and the outer tubing string 36. Flow into
and out of the casing-tubing annulus 13 is accomplished through
blooie line 58 or kill line 60.
FIGS. 8 and 8A illustrate the concentric check valve which is
indicated generally by the number 62. The function of the check
valve is to close off the annulus 105 between the outer tubing
string 36 and the inner tubing string 32 to flow in an upward
direction. Concentric check valve 62 permits flow in a downward
direction in this annular flow path. The concentric string check
valve includes a tubular mandril section 220 having a central
opening over its entire length. The lower end of the mandril
section is connected into tubing string 32. An annular-depending
truncated cone-shaped resilient member 221 is engaged over the
outside of the tubular mandril section 220. The tapered end of the
resilient member 221 is fitted over sleeve 222 and the flared end
224 of the resilient member engages against the interior wall of
tubing section 36. A collar member 226 connects the upper end of
mandril section 220 to interior tubing string 32 and additionally
forces the resilient member 221 out against the interior wall of
the outer tubing string 36.
The resilient member is preferably made of rubber. A preferred form
of rubber is buytle N. In a particular instance for a concentric
check valve for use in a 350 psi foam system such rubber material
having Shore hardness of 70 gave excellent results. It should be
noted that a similar material having a Shore hardness of 40 was too
soft to prevent flowback and a similar material having a Shore
hardness of 90 was too hard to allow pump by of the foam.
FIG. 9 illustrates in greater detail the liner 18--casing 16
juncture and illustrates a crossover connection between inner
tubing string 32 and the jet washer tool. This crossover connection
66 facilitates connecting tubing string 32 into the jet washing
tool after the tool has been run into the well on outer tubing
string 36. Briefly, the crossover connection includes a sub 229
connected into the inner tubular member 232 of the jet washer. Sub
229 has interior square threads at its upper end which are adapted
to easily receive similar threads on the outside of tubing sub 231.
The square threads contain o-rings to seal the connection. Tubing
sub 231 is connected at its upper end to tubing string 32. In this
manner tubing string 32 can be run into the hole with tubing sub
231 connected to its lower end and a remote connection can be
easily made between tubing sub 231 and crossover sub 229 which had
been previously run with tubing string 36.
FIGS. 10 and 10A illustrate jet washing tool 64 in more detail. As
noted above, the jet tool 64 is positioned adjacent well liner 18
which has slots 19 which need cleaning. An inner tubular member 232
having its upper end connected to inner tubing string 32 extends
the length of the jet tool 64. One or more jets 64 are connected to
inner tubular member 232 and extend through outer tubular member
236. The outer tubular member 236 has its upper end connected to
tubing string 36 and continues to form annulus 105 with inner
tubular member 232. The jets communicate with the interior of
tubing member 232 and the annular space 13 between the outer tubing
36, 236 and the casing 16--liner 18. The jets comprise a jet body
238 having a central opening 239 formed therein. The jet body thus
forms the orifice through which the jet is formed. A jet seat
member 240 having interior threads is fixedly connected between
inner tubular member 232 and outer tubular member 236 by suitable
means such as welding. The tubular members have axially aligned
openings to receive the jet seat member. The jet seat members 240,
240' serve the dual function of seating the jet bodies 238, 238'
and maintaining tubular members 232 and 236 in predetermined
spaced-apart relationship. A jet body has an exterior thread
portion adapted to be mated with the interior threads of jet seats
240. The jet bodies, therefore, may be turned in or out to adjust
the standoff distance between the exit of the jet from orifice 239
to the well liner. This distance is adjusted so that the exit of
the jet from the jet body 238 at orifice 239 is between 5 and 10
times the diameter of the orifice 239 formed in the jet. In other
words, the diameter of the jet as it leaves the tip of jet body 238
determines the standoff spacing of the jet. This is clearly shown
in FIG. 12. Note that the distance B--B must be from 5 to 10 times
the distance A--A. Also the length of the orifice having the
diameter A--A should be at least 5 times the diameter A--A.
The lower end of tubular member 236 is connected to a tubular sub
336 leading to the check valve and bit. FIG. 11 illustrates in more
detail the drop ball valve indicated generally by the number 67 and
bit 70. The lower end of the inner tubular member 232 terminates in
a ball valve seat. Thus ball valve seat member 245 having a central
opening 247 of reduced diameter is connected to inner tubular
member 232 by crossover sub 249. A ball 251 having a diameter
smaller than the overall inner diameter of the flow path 32, 232,
249 but larger than the reduced diameter 247 of ball valve seat 245
is shown resting in the ball valve seat to close the flow path
above such valve. The ball is introduced into the inner tubing
string 32 at lock valve 26. It is noted that prior to introduction
of the ball, fluid may be circulated through the inner tubing
string flow path 32, 232 and the well annulus 13.
A flapper valve sub 72 is connected to the tubular sub 336 and
contains a conventional downwardly opening flapper valve indicated
in dashed lines at 256. A sand bit 70 is connected below the
flapper valve sub 256 and is useful in removing sand or other
debris from the well in conjunction with foam injected down the
annulus between the inner tubing and outer tubing. The foam goes
through the flapper valve 256 and is then ejected out of the lower
portion of bit 70 and circulates sand or the debris to the surface
via annulus 13 and out blooie line 58. The bit 70 is also very
important in providing mechanical centralization of the jet tool
during running of the tool in the well on the outside tubing
string. Thus the blades of the bit 70 are selected to be only
slightly less in diameter than the inside diameter of the liner
which is to be cleaned.
The use of relatively smaller diameter jet orifices of less than
1/8th inch in the present invention has the advantage of reducing
to a minimum the amount of liquid being injected into the well.
This reduces the horsepower requirements. Further, the lower
volumes of liquid reduce the possibility of the liquid column in
the well overpowering the formation and doing formation damage.
Table I below indicates the effect of jet size on flow volume and
standoff distance on power. It also illustrates the difference in
fluid requirements to obtain the necessary jet velocities with
different sized jets. As noted, it has been discovered that small
diameter jets at the higher velocities taught herein are effective
in cleaning liner openings of substantially all plugging
material.
TABLE I ______________________________________ EFFECT OF JET SIZE
ON FLOW VOLUME AND JET STAND-OFF ON POWER LOSSES
______________________________________ POWER SIZE GPM at FULL 1/10
1/100 JET 7000 PSI (6D) (12D) (28D)
______________________________________ 1/32" 1.94 0.187" 0.374"
0.784" 1/16" 7.8 0.375" 0.750" 1.75" 1/8" 31.2 0.750" 1.36" 3.50"
______________________________________
Table II below summarizes results obtained in high pressure jet
cleaning of plugged liners. The data in Table II indicates that jet
velocities in excess of 700 feet per second are needed to obtain
substantially complete cleaning of the plugged openings. In this
regard many different types of plugging material are encountered in
wells. It is important that the openings be substantially 100
percent cleaned, so therefore the most difficult material must be
removed. This can be done if velocities and standoff distance are
maintained in accordance with this invention. The cleaning liquid,
which in this instance was water, was jetted through a 1/16th inch
jet orifice at pressures in excess of 6,000 pounds per square inch.
The environmental fluid through which the water was jetted was
either foam or water as indicated. The data indicates that a
standoff distance of greater than one inch with a 1/16th inch
diameter jet orifice is too great for effective cleaning. A 5/8
inch standoff or less is preferred using a 1/16th inch jet orifice.
An angled jet is somewhat more efficient than a head-on jet. In
order to clean substantially all the slots, a standoff distance of
less than 10 diameters is required. All tests were done with 1/16
inch nozzle. The liners were 51/2 inches and had 40 mil slots on 3
inch centers. The rotation rate of the liner was 30-35 RPM.
Vertical movement rate of the nozzle was 2 inch/min. Tests 1
through 12 were on one liner and 13 through 15 on another.
TABLE II
__________________________________________________________________________
TEST FLUID PRESSURE JET STAND-OFF NO. ENVIRONMENT PSIG VELOCITY
INCHES CONCLUSION
__________________________________________________________________________
1 Water 6,000 945 3/8 All slots cleaned. 2 Water 6,000 945 3/4 All
slots clean. 3 Water 6,000 945 11/8 It was decided tests should be
continued before deciding. 4 Water 6,000 945 11/8 Continuing 3 --
Estimated 60% clean. 5 Water 6,000 945 11/2 Penetrated slightly
into nearly all slots but did not clean hardly any all the way
through. 6 Water 7,000 1,020 11/2 Same as 5. 7 Water 7,000 1,020
11/2 Nozzle was not moved in this test. Liner was rotated 5 mins.
90% of slots were clean for about 1/2" length. 8 Water 7,000 1,020
11/8 50-60% of material in slots was removed. Only .about. 20-30%
of slots completely clean. 9 Foam 7,000 1,020 11/8 50-60% clean --
Similar to 8. 10 Foam 6,000 945 11/8 Same result as 9. 11 Foam
6,000 945 3/4 80-90% of material removed but only about 50% of
slots were completely clean. 12 Foam 7,000 1,020 3/4 Same as 11. 13
Foam 7,000 945 1/2 Half of a 3 foot liner section was used. 50-75%
of slots were completely cleaned. 14 Foam 7,000 945 1/2 Second half
of liner section was cleaned. Nozzle with 10.degree. angle upward
was used. Result was similar to 13 -- slightly better. 15 Water
7,000 945 3/8 Liner in 13 and 14 was cleaned second time -- 75-90%
of slots were now open.
__________________________________________________________________________
Table III below summarizes additional results obtained in high
pressure jet cleaning of plugged liners. The data in Table III
indicates that jet velocities in excess of 700 ft. per second are
needed to obtain satisfactory cleaning of the openings. In some of
these runs gas was entrained in the liquid. This gave poor results
indicating that liquid alone should be used as the jetting media.
The data also reveals that the smaller diameter 1/16 inch jet is at
least as effective as the larger 1/8 inch diameter jet in cleaning
the openings. The runs were conducted in an air environment. The
data for liner No. 7 indicates that cleaning at a standoff distance
of about 13 diameters for some material in some openings is
effective. However, to insure substantially complete cleaning of
openings having various plugging materials, it is necessary to be
within 10 diameters when jetting.
TABLE III
__________________________________________________________________________
Liquid Size Jetting Pump Nitrogen Pump Jet Observed No. of Time
Rate Rate Pressure Velocity Jet Perforation Jets Jets Minutes GPM
SCFM PSI Ft/Sec Standoff Cleaning Evaluation
__________________________________________________________________________
Liner No. 1 65/8" 60M 2 1/8" 2 52 0 6000 783 1.06" Missed Perf'ns.
Advanced too fast, 26'/min while rating 90RPM. Partially plugged
with soft asphaltenes and clays 2 1/8" 2 30 800 7000 638 1.06" Fair
Slowed forward motion with friction on liner. The driving roller
slipped which caused them to transport the loose plugging material
on the outside of the liner into the cleaned perforations. This
driving method masked the cleaning action. Removed electric motor
from the driven roller train and substituted a pneumatic motor to
slow the liner rotational speed from 90 to 5-10 RPM. The pitch of
the driving rollers caused the liner to be cleaned to advance 3.5
inches per revolution. 2 1/8" 2 38 1100 9100 773 1.06" Poor
Cleaning Jet seemed to be ineffective plus had trouble hitting
perforation w/only 2 jets. 3 1/8" 3 60 0 9500 910 1.06" Fair --
perforations hit were cleaned except the high pressure loosened the
milled burrs which were driven into the perforations and provided
for a partial plug. Energy level probably too high. -- 2 1/8" 5 25
450 4000 563 1.06" Poor Cleaning Did not seem to be able to get
jets to hit plugged portion of perforations. 4 1/8" 11 84 0 4000
753 1.06" Excellent Polish cleaned - all slots opened. Four jets
solved indexing problem. Liner No. 2 65/8" 60M 4 1/8" 8 82 0 4000
700 1.06" Poor to Fair Partially opened perforations. Checked jets
- all opened. Repositioned for rerun. Partially plugged with soft
asphaltenes, hard scale and 4ust. 1/8" 5 65 500 4100 615 1.06" Poor
Didn't clean all of perforations. 4 1/8" 6 100 0 6000 1030 1.06"
Good Cleaned all perforations except where products of corrosion
were present. Liner No. 3 65/8" 60M 4 1/8" 10 84 -- 4000 753 1.15"
Good Poor test because of soft plugging material. Plugged with soft
asphaltenes. Liner No. 4 65/8" 60M 4 1/8" 7 53 450 3000 505 1.15"
Poor Had very low indicated energy level. Seems that entrained gas
softened blow - acts like shock absorber. Unplugged estimated 20%
of perforations hit. Overall, about .+-.10% of perforations opened.
Plugged with soft asphaltenes 4 1/8" 7 90 -- 4000 870 1.15" Good
Cleaned most of perforations -- estimate 98% cleaned. Liner No. 5
65/8" 60M 4 1/8" 4 90 -- 4000 870 1.15" Fair Partially cleaned
perforations Hard weathered plugging material of scale, cement and
rust. 4 1/8" 5 105 -- 6000 1115 1.15" Good Estimate 98% effective
cleaning job. Believe balance of problem is that of indexing jet so
that it hits all of the perforations. See Pictures. Liner No. 6
51/2" 60M 4 1/8" 6 71 1125 6000 667 .95" Very Poor Very low energy
level indicated. Estimate .+-.5% of perforations cleaned. Hard
weathered asphaltenes and clays. 4 1/8" 5 105 -- 6000 1115 .95"
Very Good Rewashed 1/2 liner with water-detergent solution. All
perforations cleaned. 4 1/8" 6 70 1125 6000 660 .95" Very Poor
Rewashed 1/2 liner with foam. Very low energy level indicated.
Presence of compressable gas seems to dampen jetting action.
Estimate 25% of perforations open. Liner No. 7 51/2" 60M 2 1/16" 12
10 -- 6000 705 .86" Excellent Jets failed to hit all of
perforations due to spacing and advancing speed. Cleaned all
perforations hit. Plugged with hard rust scale and hydrocarbons 2
1/16" 7 15 -- 10,000 1600 .86" All perforations cleaned and end of
this
__________________________________________________________________________
test.
Field operations were conducted in a number of California wells
having liners whose openings were plugged to the point that
production had declined to below a desirable rate. In instances
where the jet standoff distance was below 5 diameters of the jet
there occurred excessive erosion of the jet body from splash back.
Thus, although successful cleaning can be accomplished at very
close range, it is preferred to maintain at least a standoff
distance of 5 diameters to prevent erosion of the jet body. The
results of field operations are summarized in Table IV below. The
concentric string apparatus disclosed in this application was
utilized in Wells A, B and C. A single string apparatus was
utilized in Well D. Foam was used prior to, concurrent with and
after the jetting in Wells A, B and C.
TABLE IV
__________________________________________________________________________
DAILY DAILY JET JET STANDOFF PRODUCTION PRODUCTION JET VELOCITY IN
JET BEFORE AFTER WELL SIZE F.P.S. JET DIAMETERS LIQUID OIL/WATER
OIL/WATER REMARKS
__________________________________________________________________________
A 1/16" 945-1015 8.35 H.sub.2 O 17/90 46/303 Well had previously
been string shot with favorable results but had rapid production
decline. Well is in steam displacement project. B 1/16" 945-1000
4.65 H.sub.2 O 4/35 35/33 Operation successful in opening slots.
Short standoff distance resulted in excess erosion to jet body do
to excessive splash back. Prefer 5 diameters minimum. C 1/16"
1000-1050 4.0 H.sub.2 O 7/5 19/11 Jet washed well evaluated
production -- then preformed cyclic steam injection operation.
Daily production after steaming was 105 oil and 104 water. Without
jet washing would estimate production limited to 40 oil and 20
water. Minimum standoff again caused erosion of jet body. D 1/32"
1000-1050 6.0 H.sub.2 O 4/5 24/125 Jet washed the liner. Then foam
cleaned well after jetting. Then steamed well and returned to
__________________________________________________________________________
production.
SUMMARY OF ADVANTAGES OF PRESENT INVENTION
The present invention provides methods and apparatus for jet
cleaning plugged openings in well liners. A principal advantage of
the present invention is the ability to apply high energy
directionally to clean openings in well liners. In accordance with
the invention the directional application of high energy is done
with high velocity liquid through small diameter jet orifices.
Thus, the invention has the advantage of requiring relatively low
horsepower. Further, liquid volume required to do the cleaning is
also reduced. The apparatus of the invention permits rotation and
reciprocation of the jet tool in the well during high pressure
jetting to provide for the directional application of the cleaning
energy. Thus new swivels, jet tools and a check valve are provided.
Additional advantages will be apparent to those skilled in the
art.
* * * * *