U.S. patent application number 09/733591 was filed with the patent office on 2002-06-13 for completing wells in unconsolidated formations.
Invention is credited to Nguyen, Philip D..
Application Number | 20020070020 09/733591 |
Document ID | / |
Family ID | 24948281 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020070020 |
Kind Code |
A1 |
Nguyen, Philip D. |
June 13, 2002 |
Completing wells in unconsolidated formations
Abstract
A method of completing an unconsolidated formation by first
injecting a curable resin into diametrically-opposed zones within
the formation and then allowing the resin to set to form a
consolidated mass in these zones. Once the resin has set, the
consolidated zones are hydraulically fractured to establish fluid
communication between the untreated area of the formation outside
these zones and the wellbore. Preferably, the fracturing fluid
carries resin-coated proppants which, when set, form a permeable
mass within the fractures to thereby allow flow of fluids through
the fracture while preventing flow of sand.
Inventors: |
Nguyen, Philip D.; (Duncan,
OK) |
Correspondence
Address: |
DENISE Y. WOLFS
EXXONMOBIL UPSTREAM RESEARCH COMPANY
3120 BUFFALO SPEEDWAY
P.O. BOX 2189
HOUSTON
TX
77252-2189
US
|
Family ID: |
24948281 |
Appl. No.: |
09/733591 |
Filed: |
December 8, 2000 |
Current U.S.
Class: |
166/295 ;
166/308.1 |
Current CPC
Class: |
E21B 43/261
20130101 |
Class at
Publication: |
166/295 ;
166/308 |
International
Class: |
E21B 043/26 |
Claims
What is claimed is:
1. A method of completing an unconsolidated, subterranean formation
through a wellbore, said method comprising: injecting a
consolidating agent through said wellbore and into at least one
zone within said formation to form a consolidated mass therein; and
fracturing said consolidated mass with a fracturing fluid to
establish fluid communication between the area of said formation
outside of said zone and said wellbore.
2. The method of claim 1 wherein said consolidating agent is a
curable resin.
3. The method of claim 2 wherein said resin is selected from the
group consisting of thermo-setting epoxy, phenolic, furan, and
polyurethane.
4. The method of claim 1 wherein said fracturing fluid contains
proppants.
5. The method of claim 4 wherein said proppants are
resin-coated.
6. A method of completing an unconsolidated subterranean formation
through a wellbore, said method comprising: casing said wellbore
with a casing; forming openings in said casing adjacent said
formation; injecting a consolidating agent down said wellbore into
said formation through said openings in said casing; allowing said
consolidating agent to set to form consolidated zones within said
formation which lie adjacent said openings in said casing; and
injecting a fracturing fluid through said openings in said casing
to fracture said consolidated zones and thereby establish fluid
communication between the untreated area of said formation outside
said consolidated zones and said wellbore.
7. The method of claim 6 wherein said openings comprise: two sets
of openings formed in said casing and spaced diametrically-opposed
from each other.
8. The method of claim 7 wherein said two sets of openings are
positioned adjacent the natural fracture plane of said
formation.
9. The method of claim 7 wherein said openings are perforations
through said casing.
10. The method of claim 7 wherein said openings are slots through
said casing.
11. The method of claim 7 wherein said consolidating agent is a
curable resin.
12. The method of claim 11 wherein said resin is selected from the
group consisting of thermo-setting epoxy, phenolic, furan,
polyurethane
13. The method of claim 11 wherein said curable resin is injected
into said formation through each of said two sets of openings in
said casing to form respective consolidated zones in said formation
adjacent said sets of openings.
14. The method of claim 13 wherein said fracturing fluid contains
proppants.
Description
DESCRIPTION
[0001] 1. Technical Field
[0002] The present invention relates to a method for completing a
well in an unconsolidated formation and in one of its aspects
relates to a method for completing a well in an unconsolidated
formation wherein a zone within the formation is consolidated by
injecting a curable resin and then fractured once the resin has set
to thereby provide fluid communication between the untreated
formation and the wellbore.
[0003] 2. Background of the Invention
[0004] In producing hydrocarbons or the like from loosely or
unconsolidated subterranean formations, it is not uncommon to
produce large volumes of particulate material (e.g. sand) along
with the formation fluids. This "sand production" routinely causes
a variety of problems which result in added expense and substantial
downtime. For example, the produced sand may cause (1) severe
erosion and premature wearing of the well tubing and other
production equipment; (2) clogging of the flow from the well which
requires a workover of the well; (3) extra processing of the
produced fluids at the surface to remove and dispose of the sand;
(4) caving of the formation, etc. Accordingly, it is extremely
important to control the production of sand from such wells.
[0005] There are several techniques that are well known for
controlling "sand production" from unconsolidated formations. One
such known technique involves injecting a consolidating agent, e.g.
curable resin, into the formation to stabilize the area of the
formation which lies near the wellbore. The resin is injected, in
its uncured state, through the wellbore into the near-wellbore area
of the formation where it coats and bonds the grains of sand
together to form a solidified matrix around the wellbore. In the
prior art consolidated treatment, a postflush liquid is then
injected into the formation to displace the resin from the pore
spaces formed between the bonded grains of sand within the matrix,
thereby restoring some permeability to the treated area through
which the formation fluids can flow through the matrix and into the
wellbore.
[0006] While such techniques have been widely used, unfortunately,
they experience some major drawbacks. For example, since this type
of consolidation treatment is usually carried out in a well having
an "open hole" completion (i.e. wellbore is uncased adjacent
formation to be treated), there is always uncertainty of whether or
not the resin has uniformly penetrated into the formation which
surrounds the wellbore. In other words, there is no assurance that
the bulk of the resin did not merely flow into the formation at one
point adjacent the wellbore (i.e. path of least resistance) while
leaving the areas around the wellbore virtually untreated. This is
obviously undesirable, if not unacceptable, since substantial
amounts of sand may still be produced from the untreated areas of
the formation abutting the wellbore thereby significantly defeating
the overall benefits of the consolidation treatment.
[0007] Further, the actual amount of permeability which exists in
the consolidated matrix once the resin has cured is difficult to
predict and is often substantially less than expected and, in some
cases, is not adequate for commercial production. In such
instances, the treatment may have to be repeated or some other
workover performed before the well will produce at satisfactory
rates.
SUMMARY OF THE INVENTION
[0008] The present invention provides a method of completing an
unconsolidated, subterranean formation by treating zones of the
formation with a consolidating agent, e.g. curable resin, wherein
(a) the injection of the resin is controlled to insure proper
placement of the resin and (b) the final permeability of the
consolidated zone is assured whereby flow of formation fluids can
flow into the wellbore while flow of sand is prevented. Basically,
in the present method, a curable resin is injected into selected
zones and is allowed to set to form a consolidated mass within
these zones. These zones are then hydraulically fractured to
establish fluid communication between the untreated area of the
formation and the wellbore and are propped by proppants, preferably
resin-coated.
[0009] More specifically, a wellbore is drilled through the
formation and is cased with a string of casing. Two sets of
openings (e.g. perforations, slots, etc.) are formed in the casing
diametrically-opposed to each other with each set of openings lying
substantially adjacent the natural fracture plane of the formation.
A consolidating agent, e.g. a curable resin, is injected down the
wellbore and out into the formation through the opposed sets of
openings in the casing and form two zones in the formation which
lie adjacent the respective sets of openings. The resin is allowed
to set and cure in these zones to become consolidated masses around
the respective sets of openings. Preferably, the resin is a
thermosetting resin which is cured by the temperature in the
formation.
[0010] Once the resin has hardened, a fracturing fluid is pumped
under pressure down the wellbore and out through the same
respective sets of opposed openings in the casing to thereby create
a fracture through the respective consolidated zones and thereby
establish fluid communication between the untreated area of the
formation outside of the zones and said wellbore. Preferably, the
fracturing fluid contains proppants which are resin-coated so that
once the proppants are placed in the fractures by the fracturing
fluid, the resin on the proppants sets and cures to bind the
proppants together into a consolidated, permeable mass within the
fractures. This permeable mass of bonded proppants allows fluids
from the untreated areas of the formation to flow into the wellbore
while acting as a filter in preventing flow of sand
therethrough.
[0011] By injecting the consolidating agent through
diametrically-opposed openings in the well casing, its placement
will be controlled so that it flows into those areas of the
formation which are to be treated. Further, by subsequently
fracturing only the treated zones within the formation, only the
desired production fluids can flow from the untreated areas of the
formation into the wellbore.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The actual construction, operation, and apparent advantages
of the present invention will be better understood by referring to
the drawings which are not necessarily to scale and in which like
numerals identify like parts and in which:
[0013] FIG. 1 is a plan, cross-sectional view of a cased wellbore
at a point adjacent an unconsolidated formation to be completed
illustrating an initial step of the method of the present
invention;
[0014] FIG. 2 is the plan, cross-sectional view of FIG. 1 after an
intermediate step of the present invention has been carried out;
and
[0015] FIG. 3 is the plan, cross-sectional view of FIG. 2 after the
formation has been completed in accordance with the present
invention.
[0016] While the invention will be described in connection with its
preferred embodiments, it will be understood that this invention is
not limited thereto. On the contrary, the invention is intended to
cover all alternatives, modifications, and equivalents which may be
included within the spirit and scope of the invention, as defined
by the appended claims.
BEST KNOWN MODE FOR CARRYING OUT THE INVENTION
[0017] Referring more particularly to the drawings, FIG. 1
illustrates a cross-sectional, plan view of wellbore 10 which has
been drilled from the surface (not shown) through an unconsolidated
production formation 11. As will be understood by those skilled in
the art, wellbore 10 has been cased and cemented with casing 12 and
cement 13 through formation 11. In carrying out the method of the
present invention, openings 14 are formed through casing 12 and
cement 13 at point(s) adjacent formation 11 to thereby provide
fluid communication between the formation and wellbore 10. Openings
14 comprise two set of openings which are formed
diametrically-opposed from each other in casing 13 and are
positioned to lie substantially on the natural fracture plane of
the formation.
[0018] Preferably, these openings are perforations which are formed
by a standard 180.degree. perforating gun which, in turn, has been
oriented with respect to the fracture planes of formation 11 by
commercially-available techniques. Alternatively, the sets of
opposed openings 14 can be slots formed by standard, known
hydrojetting techniques. The forming of the opposed openings 13,
either by perforating or by hydrojetting, will also aid in
initiating a single bi-wing fracture when the formation is
subsequently hydraulically-fractured as will be more fully
explained below.
[0019] Next, a consolidating agent is injected down a workstring
(not shown) within wellbore 10 and into formation 11 through
openings 14 in casing 13. The consolidating agent may be any
substance which can be placed in its liquid state and then hardens
to bond the sand grains of the formation into a solid-like mass.
Preferably, the consolidating agent is a curable resin, e.g.
thermo-setting epoxy, phenolic, furan, polyurethane, or the like
and a curing agent, if necessary, as is known in the art. The resin
flows out through the opposed openings 14 and coats the sand grains
into zones 15 of formation 11 on either side of casing 13 as shown
in FIG. 2. When the desired volume of resin has been injected, it
is allowed to set and cure (e.g. under the influence of the
formation temperature) to thereby form a consolidated mass within
zones 15 which lie adjacent said openings 14.
[0020] Once the resin has cured, a typical fracturing fluid, e.g.
cross-linked polymer gel, is pumped down a workstring (not shown)
and out into zones 15 through openings 14 in casing 13 to
"hydraulically fracture" zones 15. The fracturing fluid is pumped
at a pressure sufficient to create the bi-winged fracture 16 in the
respective zones 15 on either side of the casing as illustrated in
FIG. 3. It is preferred that the fracturing fluid carry particulate
material (e.g. large grain sand having 8-60 mesh size) which act as
proppants to keep fractures 16 open when the fracturing pressure is
relieved.
[0021] Further, preferably, the particulate material is
resin-coated proppants, either pre-coated or "coated on-the-fly",
so that once placed in the fractures 16, the resin on the proppants
sets and cures to bind the proppants together into a consolidated,
permeable mass within the fractures 16. This permeable mass of
bonded proppants serves to fluidly connect the untreated,
unconsolidated areas of formation 11 outside of consolidated zones
1b to the wellbore 11 by allowing flow of fluids therethrough while
acting as a filter in preventing flow of sand therethrough.
* * * * *