U.S. patent number 3,918,522 [Application Number 05/437,231] was granted by the patent office on 1975-11-11 for well completion method and system.
Invention is credited to George O. Suman, Jr..
United States Patent |
3,918,522 |
Suman, Jr. |
November 11, 1975 |
Well completion method and system
Abstract
A well completion method is provided wherein an inflatable
packer is positioned in an open borehole of a well opposite a
formation from which or into which a fluid is to flow. Cement is
then forced into the packer to expand its packing element into
contact with the wall of the borehole at the formation. The cement
is allowed to set and then at least one perforation is made from
the interior of the packer through the cement and packing element
to the formation. A well system is also provided in which the well
is equipped with such a packer so installed and having such a
perforation.
Inventors: |
Suman, Jr.; George O. (Houston,
TX) |
Family
ID: |
23735604 |
Appl.
No.: |
05/437,231 |
Filed: |
January 28, 1974 |
Current U.S.
Class: |
166/285; 166/187;
166/289; 166/297 |
Current CPC
Class: |
E21B
33/14 (20130101); E21B 21/08 (20130101); E21B
33/127 (20130101); E21B 43/11 (20130101); E21B
49/006 (20130101); E21B 3/00 (20130101) |
Current International
Class: |
E21B
21/00 (20060101); E21B 33/127 (20060101); E21B
49/00 (20060101); E21B 33/12 (20060101); E21B
33/13 (20060101); E21B 21/08 (20060101); E21B
3/00 (20060101); E21B 43/11 (20060101); E21B
33/14 (20060101); E21B 033/127 (); E21B 033/14 ();
E21B 043/11 () |
Field of
Search: |
;166/285,292,187,297,289,35R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Novosad; Stephen J.
Assistant Examiner: Suckfield; George A.
Attorney, Agent or Firm: Hyer; W. F. Eickenroht; Marvin
B.
Claims
The invention having been described, what is claimed is:
1. A method of completing a well having a formation penetrated by
an open borehole comprising positioning a packer in the borehole
opposite said formation, said packer having an elongated resilient
packing element expansible radially by forcing a fluid into the
packer, then flowing a fluid into the packer to cause the packing
element to expand radially into contact with the wall of the
borehole at said formation while causing the packer to confine said
fluid to be within said packing element, said fluid being capable
of setting as a solid mass, permitting said fluid to set to a solid
mass while so confined by said packer, and then forming at least
one perforation extending from the interior of the packer through
the confined solid mass and the packing element to the
formation.
2. The method of claim 1 wherein said fluid comprises portland
cement.
3. The method of claim 2 including the further step of flowing a
fluid through the perforation into or out of said formation.
4. The method of claim 1 wherein the packer extends vertically in
the borehole from a point above to a point below said
formation.
5. The method of claim 4 wherein the well has a second formation
vertically adjacent the first mentioned formation and wherein the
packer is caused to extend across both of such formations to assure
that a fluid cannot flow from one formation to another.
6. In a well system wherein a formation is penetrated by an open
borehole, a packer assembly positioned in the open borehole
opposite said formation, said packer assembly having a radially
expansible packing element mounted on and having a fluid tight
mechanical connection with the exterior of a mandrel, a time
setting solid mass between the mandrel and packing element in
sufficient quantity that the packing element is radially expanded
into engagement with said formation, and at least one continuously
open perforation extending from the interior of the packer assembly
through the mandrel, the solid mass and the packing element to said
formation.
7. The system of claim 6 wherein the packing element is of a length
to extend vertically in the borehole from a point above to a point
below said formation.
8. The system of claim 7 wherein a second formation vertically
adjacent the first mentioned formation is also penetrated by the
borehole and wherein the packing element is of a length to extend
across both of said formations to assure that a fluid cannot flow
along the wall of the borehole from one formation to another.
Description
This invention relates to a well completion method and system
wherein the annulus between a tubular well string and the wall of
the borehole is packed off with a greater degree of dependability
and efficiency than is achieved through conventional primary
cementation techniques. In another of its aspects, it provides a
more positive support for the formation being packed off, the
degree of which support can be selected and attained without
extensive manipulation.
The present almost universal manner of completing a well to pack
off certain formations of interest is to flow cement into the
annulus between the casing and the wall of the borehole. Although
this practice has been subject to considerable investigation and
improvement for many years, it still remains one of the most
unreliable steps involved in completing a well. For example, the
cement should totally displace the drilling mud (or other fluid
which is in the well just prior to cementation) from the vertical
interval which is to be perforated and perhaps of somewhat lesser
importance, over other vertical intervals which are not to be
perforated. However, even when the best known techniques of
cementing are applied, overall mud displacement efficiency remains
too low, particularly in certain areas such as the Gulf Coast of
the United States.
Excessively poor mud displacement can result in vertical mud
channels, usually along the cement-borehole interface, mud pockets,
localized cement dilution and in general, discontinuities in the
cement between the casing and wall face. Also, there can be poor
bonding of the cement to the casing and to the well face. These
imperfections result in a poor cement job with attendant
difficulties known to those skilled in the art.
Accordingly, it is an object of this invention to provide a well
completion method and system in which the primary pack-off between
a tubular well string and a formation positively mechanically
displaces substantially all of the drilling mud or other well fluid
from the desired vertical interval to be packed off.
Another object is to achieve such a result while maintaining the
cement used for such pack off out of physical contact with the
drilling mud thereby preserving the integrity of the cement.
Another object is to provide a method and system which results in a
completed interval which can be more effectively and positively
subjected to secondary formation treatments, such as acidizing,
hydraulic fracturing and the like, than can many intervals
completed by conventional primary cementing techniques.
Another object is to provide a method and system which permits
continuous and controlled support of a formation over a broad range
of degree of support which is largely unaffected by other
completion and stimulation operations.
Other objects, advantages and features of the invention will become
apparent to those skilled in the art upon consideration of the
detailed description, the claims and the drawings wherein:
FIG. 1 illustrates a preferred embodiment of the invention as
applied to two formations in a well; and
FIG. 2 illustrates another application of the invention to complete
a single formation which lies intermediate of and adjacent to two
other formations and which are isolated from the single
formation.
In accordance with the primary aspect of this invention, a radially
expansible packer is positioned in the borehole opposite the
formation to be perforated. The packer is then expanded radially
into contact with the face of the formation thus causing the
drilling mud or other well fluid to be mechanically displaced from
the interval in the casing-borehole annulus along which the packer
extends. Preferably the expansion is to a degree not only to
displace the mud but to provide mechanical support for the
formation to a desired degree. Then a continuously open perforation
is formed extending from the interior of the packer to its exterior
to be in fluid communication with the formation. In the most
preferred mode, the packer is of the inflatable type and cement is
forced into the packer to expand the same as aforesaid. After the
cement has set to a hardened mass, the perforation is formed to
extend through the packer mandrel, the cement forced into the
packer and the resilient packing element.
Referring to the drawings, there is shown a well which has been
dually completed in upper and lower formations A and B,
respectively, which formations are penetrated by a borehole 10. It
will be understood that the method and system of this invention are
applicable to single zone completions as well as multiple zone
completions.
Thus, after the borehole has been drilled, it will contain drilling
mud or other fluid for formation control and other purposes. A
string of casing 11 is then run into the hole after a pair of
packers, preferably inflatable packers 12 and 13, have been made up
therein and spaced so that when the casing has been landed, the
packers will be opposite their respective formations. The well can
then be subjected to a primary cement job by conventional
techniques so that cement 14 fills the annulus between the casing
string and the wall of the borehole. During this operation, packers
12 and 13 remain in deflated condition so that cement can flow
therepast to cement the intervals between the packers and above the
packers.
The packers are preferably of the inflatable type and can be of the
construction shown at page 2847 of the 1972-73 Composite Catalog of
Oilfield Equipment and Services with suitable adjustment of their
length to accommodate formations of various thicknesses. Other
inflatable packer constructions can be used. In any event, the
packer will usually comprise a mandrel 15 which can be provided by
a length of casing sealingly and slidably extending through an
upper connector assembly 16 to be connected to a lower connector
assembly 17. A radially expansible packing element 18 extends
between and is connected to the upper and lower connector
assemblies 16 and 17. The packing element can comprise a sleeve of
rubber or other suitable material which, in its contracted
position, is of a somewhat larger outer diameter than the casing
but which, when expanded, forcibly engages the face of the
borehole. Expansion of the packer is accomplished in accordance
with this invention by forcing cement through passageway 19 into
the interior of the sleeve until the latter is suitably expanded. A
valve system 20 can be provided to open at a preset pressure to
allow cement to flow into the packer and to close to prevent
backflow of cement from the packer before the cement has set. Such
a valve system is indicated in the above page of the Composite
Catalog.
During the primary cementing operation, a suitable plug 21 or other
shut off device is placed in the casing and pumped down the same by
additional cement on top of the cementing plug. As the cementing
plug passes the packers, it will shear off a plug 20a on each of
them so that cement 22 is caused to flow into the packer to inflate
and expand the packer. This will cause the packing elements or
sleeves 18 to not only displace the primary cement between the
packing element and the formation but also to displace any mud or
other well fluid that may exist in such an interval so that there
is a continuous and uninterrupted contact of the packing element
with the formation face. Also, additional cement can be forced into
the packer to cause it to exert a desired degree of supportive
force against the formation. After all of the packers have been
set, cement remaining in the casing can be drilled out in a
conventional manner. Alternatively, it can be circulated out using
tubing or a macaroni string to conduct the wash fluid into the well
for such operation.
After the cement in the packers has set to a solid mass, one or
more perforations 23 are formed from the interior of the element 18
to the respective formations and preferably thereinto as shown.
Thereafter, various other completion and formation treatment
operations can be conducted in a conventional manner.
In FIG. 1, each of the packers is shown to be of a length to extend
vertically from a point above to a point below their respective
formations. This effectively isolates the formations from other
formations above or below the packed off formations. In this
connection, FIG. 1 also illustrates, perhaps in a somewhat
exaggerated manner, a poor cement job in the intervals between the
packers. Thus the cement 14 in the annulus does not completely fill
the annulus since there are outer annuli or channels 24 which
remain filled with mud. It is through such channels that one
formation communicates with another in the case of a poor cement
job. However, as shown in FIG. 1, these channels are terminated by
the packers above and below their respective formations so that
such communication is prevented.
FIG. 2 illustrates a single zone completion with the packer also
completely isolating formations 30 and 31 lying above and below the
formation 32 to be perforated. This assures not only formations 30
and 31 (which may be, for example, fresh water formations) from not
only communicating with formation 32 but also with all other
formations. Since the elements of FIG. 2 correspond generally with
those described in connection with FIG. 1, they have been assigned
like numerals.
While cement has been referred to specifically as the fluid for
expanding the packer, other fluids capable of being flowed into the
packer and thereafter setting to a solid mass can be used. Also,
while the perforations have been referred to as being formed, such
as by conventional shaped charge perforating techniques, it is
possible to form the perforation by using a Permeator of the type
sold by the Permeator Corporation of Houston, Texas. In using
Permeators, their housing is screwed into a threaded opening in the
packer mandrel and their smaller piston is attached to an opening
in the packing element. Then after the packer has been expanded as
aforesaid, the acid soluble plugs in the Permeators can be
dissolved in conventional fashion to open the perforation from the
interior of the packer to the formation. In this case, one need not
wait on the cement to set into a hardened mass before the plugs are
dissolved.
The practice of this invention has several advantages over
conventional completion techniques among which are:
1. Optimum conditions exist for the best bond between the mandrel
15 and the cement 22 since the surface of the mandrel is not
"wetted" by mud or oil.
2. Elimination of mud channels and pockets, and when applied, an
elevated state of formation stress by the packer minimizes the
chance for vertical cement sheath tension failures during formation
treatments at elevated pressures.
3. The cement adjacent to perforations will not be weakened due to
mud contamination.
4. The opportunity for hydraulic bond failure will be
minimized.
5. Formation pre-stress prevents cylindrical openings from forming
at the cement-formation interface during high pressure
treatments.
6. Shattering of the cement in the packer would not create
communication channels to other formations because of the packing
element seals to the formation face along its entire depth.
7. Acid treatments cannot dissolve the rubber-formation
interface.
* * * * *