U.S. patent application number 10/818849 was filed with the patent office on 2005-10-13 for composition and method for fracturing subterranean reservoirs.
Invention is credited to Berger, Christie H., Berger, Paul D..
Application Number | 20050227874 10/818849 |
Document ID | / |
Family ID | 35061320 |
Filed Date | 2005-10-13 |
United States Patent
Application |
20050227874 |
Kind Code |
A1 |
Berger, Paul D. ; et
al. |
October 13, 2005 |
Composition and method for fracturing subterranean reservoirs
Abstract
A composition and method for fracturing subterranean reservoirs
by including a partially esterified, polyalkoxylated polyols as an
oxidizing breaker retarder in the aqueous fracturing fluid to delay
its gel breaking properties with the oxidizing breaker. The delayed
gel breaking properties will lead to the controlled breaking of the
fracturing fluid that reduces or eliminates damage to the formation
and facilitates well clean up.
Inventors: |
Berger, Paul D.; (Sugar
Land, TX) ; Berger, Christie H.; (Sugar Land,
TX) |
Correspondence
Address: |
PAUL BERGER
c/o OCT
13013 JESS PIRTLE BLVD.
SUGAR LAND
TX
77478
US
|
Family ID: |
35061320 |
Appl. No.: |
10/818849 |
Filed: |
April 6, 2004 |
Current U.S.
Class: |
507/211 |
Current CPC
Class: |
C09K 2208/26 20130101;
C09K 8/685 20130101 |
Class at
Publication: |
507/211 |
International
Class: |
E21B 043/00 |
Claims
What is claimed is:
1. A delayed breaking fracturing fluid composition for fracturing
subterranean reservoirs comprising a hydratable gelling agent, an
aqueous liquid, an oxidizing breaker, a partially esterified
polyalkoxylated polyol as oxidizing breaker retarder and optionally
a pH control agent, proppant, and crosslinking agent.
2. The delayed breaking fracturing fluid composition of claim 1
where the hydratable gelling agent is a polysaccharide and
derivatives thereof that contain one or more of the following
monosaccharide units: galactose, mannose, glucoside, glucose,
xylose, arabinose, fructose, glucuronic acid, pyranosyl
sulfate.
3. The delayed breaking fracturing fluid composition of claim 1
where the hydratable gelling agent is a synthetic polymer or
copolymer of one or more of the following: polyacrylate,
polymethacrylate, polyacrylamide, maleic anhydride methylvinyl
ether copolymers, polyvinyl alcohol, polyvinylpyrrolldone.
4. The delayed breaking fracturing fluid composition of claim 1
where the hydratable gelling agent is chosen from the group guar
gum and derivatives thereof, locust bean gum, tara, konjak,
tamarind, starch, cellulose and derivatives thereof, karaya,
xanthan, tragacanth, carrageenan.
5. The delayed breaking fracturing fluid composition of claim 1
where the aqueous liquid is water, a sodium chloride brine
solution, a potassium chloride solution, or water-alcohol
mixtures.
6. The delayed breaking fracturing fluid composition of claim 1
where the oxidizing breaker is ammonium persulfate, sodium
persulfate, potassium persulfate, sodium peroxide, sodium chlorite,
sodium, lithium or calcium hypochlorite, potassium perphosphate, or
sodium perborate.
7. The delayed breaking fracturing fluid composition of claim 1
where the partially esterified polyalkoxylated polyol oxidizing
breaker retarder is a mono and higher ester of one or more of
chosen from the group alkoxylated sorbitol, alkoxylated
monosaccharides, alkoxylated disaccharides, alkoxylated glycerine,
alkoxylated polyglycerine, alkoxylated pentaerythritol, alkoxylated
trimethylolpropane.
8. The delayed breaking fracturing fluid composition of claim 1
where the partially esterified polyalkoxylated polyol is an
alkoxylate containing ethylene oxide groups, propylene oxide
groups, butylene oxide groups or combinations of one or more
ethylene oxide groups, propylene oxide groups, butylene oxide
groups that has then been partially esterified with one or more
fatty acids.
9. The delayed breaking fracturing fluid composition of claim 1
where the partially esterified polyalkoxylated polyol is used in
amounts from about 0.1 to about 20 gallons per 1000 gallons,
preferably from about 1.0 to about 10 gallons per 1000 gallons of
the delayed breaking fracturing fluid,
10. The delayed breaking fracturing fluid composition of claim 1
where the hydratable polymer is used in an amount from about 5 to
about 80 pounds per 1000 gallons of delayed breaking fracturing
fluid composition.
11. The delayed breaking fracturing fluid composition of claim 1
where the oxidizing breaker is used in amount of about 0.1 to about
10 pounds per 1000 gallons, preferably from about 0.1 to about 0.5
pounds per 1000 gallons of delayed breaking fracturing fluid
composition.
12. A process for fracturing a subterranean reservoir by: a)
injecting into said reservoir a composition having delayed gel
breaking properties and consisting of a hydratable gelling agent,
an aqueous liquid, an oxidizing breaker, a partially esterified
polyalkoxylated polyol as oxidizing breaker retarder, a proppant
and optionally a pH control agent and crosslinking agent, b)
allowing enough time for the gel to break, and c) allowing the
broken gel to flow back out of the reservoir while leaving the
proppant behind to keep the fracture open.
13. The process for fracturing a subterranean reservoir as
described in claim 12 where the hydratable gelling agent is a
polysaccharide and derivatives thereof which contain one or more of
the following monosaccharide units: galactose, mannose, glucoside,
glucose, xylose, arabinose, fructose, glucuronic acid, pyranosyl
sulfate.
14. The process for fracturing a subterranean reservoir as
described in claim 12 where the hydratable gelling agent is a
synthetic polymer or copolymer of one or more of the following:
polyacrylate, polymethacrylate, polyacrylamide, maleic anhydride
methylvinyl ether copolymers, polyvinyl alcohol,
polyvinylpyrrolidone.
15. The process for fracturing a subterranean reservoir as
described in claim 12 where the hydratable gelling agent is chosen
from the group guar gum and derivatives thereof, locust bean gum,
tara, konjak, tamarind, starch, cellulose and derivatives thereof,
karaya, xanthan, tragacanth, carrageenan.
16. The process for fracturing a subterranean reservoir as
described in claim 12 where the aqueous liquid is water, a sodium
chloride brine solution, a potassium chloride solution, or
water-alcohol mixtures.
17. The process for fracturing a subterranean reservoir as
described in claim 12 where the oxidizing gel breaker is ammonium
persulfate, sodium persulfate, potassium persulfate, sodium
peroxide, sodium chlorite, sodium, lithium or calcium hypochlorite,
potassium perphosphate, or sodium perborate.
18. The process for fracturing a subterranean reservoir as
described in claim 12 where the partially esterified
polyalkoxylated polyol oxidizing breaker retarder where the
partially esterified polyalkoxylated polyol oxidizing breaker
retarder is a mono and higher ester of one or more chosen from the
group alkoxylated Sorbitol, alkoxylated monosaccharides,
alkoxylated disaccharides, alkoxylated glycerin, alkoxylated
polyglycerine, alkoxylated pentaerythritol, alkoxylated
trimethylolpropane.
19. The process for fracturing a subterranean reservoir as
described in claim 12 where the partially esterified
polyalkoxylated polyol is an alkoxylate containing ethylene oxide
groups, propylene oxide groups, butylene oxide groups or
combinations of one or more ethylene oxide groups, propylene oxide
groups, butylene oxide groups that has then been partially
esterified with one or more fatty acids.
20. The process for fracturing a subterranean reservoir as
described in claim 12 where the proppant is chosen from sand, resin
coated sand, synthetic ceramics, or spherical pellets of glass.
21. The process for fracturing a subterranean reservoir as
described in claim 12 where the concentration and degree of
esterification and alkoxylation of the partially esterified
polyalkoxylated polyol is chosen to give the desired amount of
delayed breaking of the gelled fracturing fluid.
Description
[0001] This patent is a substitution for U.S. patent application
Ser. No. 09/193,937 filed Nov.17, 1998 and abandoned Mar.13,
2001.
FIELD OF THE INVENTION
[0002] This invention relates to a fracturing fluid composition
containing an oxidizing breaker retarder and a method for
fracturing subterranean reservoirs using such fracturing fluid
composition.
BACKGROUND--DESCRIPTION OF PRIOR ART
[0003] Hydraulic fracturing is a technique commonly utilized to
stimulate the production of oil and gas from subterranean
formations of low permeability. In carrying out such techniques,
the fracturing fluid is introduced into the formation under
hydraulic pressure to produce one or more fractures in the target
formation. The fluid can include proppants that are deposited in
the fractures so that when the pressure against the formation is
relaxed, the proppants maintain the fracture in an open or propped
condition.
[0004] Upon completion of the treatment, it is generally desirable
to remove the gelled fracturing fluid from the formation. To
effectively remove the fluid, the viscosity of the fluid must be
reduced. The reduction of the viscosity of the gelled fluid is
referred to as "breaking" the gel. The agent responsible for
breaking the gel is referred to as a "gel breaker". Traditional gel
breakers include enzymes and oxidizing breakers. The breaker can
comprise substantially any of the well known oxidizing breakers.
Examples of oxidizing breakers include ammonium persulfate, sodium
persulfate, potassium persulfate, sodium peroxide, sodium chlorite,
sodium, lithium or calcium hypochlorite, potassium perphosphate,
sodium perborate and the like.
[0005] At formation temperatures of between about 75.degree. F. to
about 120.degree. F., and pH ranges of about 4 to 9, enzyme
breakers are suitable. At temperatures above 120.degree. F, the
enzyme breakers are inadequate and oxidizing breakers are required.
Generally, depending upon the temperature of the formation, between
about 0.1 and 5.0 pounds of the oxidizing breaker(s) per 1000
gallons of aqueous gel is sufficient to break the gel. However,
problems caused by insufficient breaking or the breaking of the
fluid too quickly are often experienced with the oxidizing
breakers. Ideally, a fracturing fluid has high initial viscosity
that remains stable during the well treatment and controlled
breaking after the treatment. Heretofore, the control of breaking
of the gel has been inadequate resulting in less than desirable
treatment results.
[0006] There have been several proposed methods for the delayed
breaking of the fracturing fluid that were aimed at eliminating the
above problems. U.S. Pat. No. 4,968,442 and U.S. Pat. No. 5,010,954
use various concentrations of ethylenediamine-tetraacetic acid
(EDTA) to break gels to a predetermined degree. One advantage
claimed in this disclosure is that gels can be broken to different
degrees thus controlling the flow-back characteristics of the
fracture. U.S. Pat. No. 4,202,795 uses persulfate or fumaric acid
or enzyme breaker encapsulated in a prill composed of a
hydrolyzable gel to delay the release of said breakers as well as
other additives such as demulsifiers that may be included in the
prill. U.S. Pat. No. 5,497,830 uses gel breakers coated with a
water insoluble wood resin to reduce the rate of release of
breaker. U.S. Pat. No. 5,437,331 uses an enzyme encapsulated in a
polymeric material such as polymethylmethacrylate (PMMA) to delay
the enzymatic breaking of the gel. U.S. Pat. No. 5,393,810 uses
sequestering agents such as copolymers of vinylpyrrolidone and
acrylic acid to reduce the gel breaking effectiveness of the
oxidizer.
[0007] Other delayed oxidizing gel breakers and techniques have
been used previously. These include enclosing the breaker within a
slowly dissolving or slowly melting capsule. The disadvantages of
this approach are 1) the technique is expensive and 2) the melting
and dissolving mechanism is dependent on the treatment and
formation conditions. If the temperature is not high enough the
capsules will not dissolve or melt.
[0008] In spite of all this technology, there still remains a need
for a composition and method for the controlled breaking of the
fracturing gel that is economical and effective and reduces or
eliminates damage to the formation and facilitates well clean
up.
[0009] In U.S. Pat. No. 6,617,285, polyols are used to accelerate
the enzymatic breaking of borate crosslinked gels. Unexpectedly, as
will be shown later, we have found that if these polyols and other
polyols are partially esterified they actual serve to retard the
breaking process of the oxidizing breaker(s), thus rendering it
more controllable.
BRIEF DESCRIPTION OF THE INVENTION
[0010] The present invention relates to fracturing-fluid
compositions containing an oxidizing breaker retarder and a method
for fracturing subterranean reservoirs using such fracturing fluid
compositions.
[0011] The fracturing fluid compositions include gelling agent(s),
cross-linker(s), oxidizing breaker(s), pH control agent(s), and
other desirable additives that comprise gelled fluids and that are
known in the art. In addition the fracturing fluids contain unique
oxidizing breaker retarders. The oxidizing breaker retarders are
partially esterified, polyalkoxylated polyols that moderate the
effect of the oxidizing breaker(s) according to their
concentrations, the well treating conditions and also by varying
the degree of esterification and the degree of alkoxylation of the
partially esterified, polyalkoxylated polyols. By the present
invention and the inclusion of partially esterified,
polyalkoxylated polyols in aqueous fracturing fluid formulations as
oxidizing breaker retarders, the gel breaking time can be
controlled.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The composition and method of the present invention is
directed to the fracturing of subterranean formations using gelled
aqueous fracturing fluids. The present invention includes a
partially esterified, polyalkoxylated polyol(s) as the oxidizing
breaker retarder in the gelled aqueous fracturing fluid
composition.
[0013] The preferred gelled fracturing fluid composition includes a
hydratable gelling agent, an aqueous liquid, an oxidizing breaker
and partially esterified, polyalkoxylated polyols as oxidizing
breaker retarder. Optionally, pH control agents, such as potassium
carbonate and the like, may be used to adjust and control the pH.
Also crosslinking agents are usually necessary to improve the gel
characteristics of the polymer used. Also proppants are usually
included to assist in keeping the fractures open.
[0014] The gelling agents include hydratable polymers, which
contain, in sufficient concentration and reactive position,
cis-hydroxyl, carboxyl, sulfate, sulfonate, amino or amide.
Particularly suitable polymers are polysaccharides and derivatives
thereof, which contain one or more of the following monosaccharide
units: galactose, mannose, glucoside, glucose, xylose, arabinose,
fructose, glucuronic acid or pyranosyl sulfate. Natural hydratable
polymers containing the foregoing functional groups and units
include guar gum and derivatives thereof, locust bean gum, tara,
konjak, tamarind, starch, cellulose and derivatives thereof,
karaya, xanthan, tragacanth and carrageenan.
[0015] Hydratable synthetic polymers and copolymers which contain
the above-mentioned functional groups and which can be utilized in
accordance with the present invention include, but are not limited
to, polyacrylate, polymethacrylate, polyacrylamide, maleic
anhydride methylvinyl ether copolymers, polyvinyl alcohol and
polyvinylpyrrolidone.
[0016] The aqueous liquid may include water, a sodium chloride
brine solution, a potassium chloride solution, water-alcohol
mixtures and the like. The hydratable polymer and aqueous liquid
are preferably prepared by combining the polymer with the aqueous
liquid in an amount in the range of from about 5 to about 80 pounds
of polymer per 1,000 gallons of aqueous liquid.
[0017] Preferably, after combining the aqueous liquid with the
gelling agent, the gelling agent may be crosslinked by the addition
of sufficient quantities of a crosslinking agent. Typical
crosslinking agents include, for example, boron, titanium,
antimony, zirconium, and aluminum. The amount of crosslinking agent
added to the hydrated gelling agent may depend upon several
factors, such as for example, the type and quantity of polymer
present in the aqueous liquid, such surface conditions to be
encountered by the crosslinked gel system, and the purpose for
which the crosslinked gel system is to be used, i.e. gel pad,
fracturing, graveling packing, etc. These and other factors are
appreciated and well known by those skilled in the art of preparing
crosslinked gel systems, and therefore sufficient quantities of
crosslinking agent are readily determinable.
[0018] Proppants may be selected from sand, resin coated sand,
synthetic ceramics, spherical pellets of glass and the like, as
commonly used in the aqueous fracturing processes.
[0019] The breaker can comprise substantially any of the well known
oxidizing breakers. Examples of breakers include ammonium
persulfate, sodium persulfate, potassium persulfate, sodium
peroxide, sodium chlorite, sodium, lithium or calcium hypochlorite,
potassium perphosphate, sodium perborate and the like. The breaker
generally will be admixed with the gelled aqueous liquid in an
amount of from about 0.1 to about 10 pounds per 1000 gallons of
aqueous gel and preferably, from about 0.1 to about 0.5 pounds per
1000 gallons of aqueous fluid depending on the preferred gel break
time.
[0020] The oxidizing breaker retarder can be any of a number of
partially esterified, polyalkoxylated polyols. These include, but
are not limit to, mono and higher esters of alkoxylated sorbitol,
alkoxylated mono and disaccharides such as glucose, fructose, and
sucrose, alkoxylated glycerine, alkoxylated polyglycerine,
alkoxylated pentaerythritol, or alkoxylated trimethylolpropane any
of which have been alkoxylated with ethylene oxide (POE), propylene
oxide (POP) and butylene oxide (POB) or mixtures of one or more
POE, POP, POB.
[0021] The amount of oxidizing breaker retarder used is determined
by several factors, including the degree of delayed break required,
the temperature, the amount of oxidizing breaker present, the
nature and the amount of crosslinked polymer present in the aqueous
fracturing fluid. Generally the amount of oxidizing breaker
retarder used is from about 0.1 to about 20 gallons, and preferably
from about 1.0 to about 10 gallons per 1000 gallons.
[0022] In the preferred method, the aqueous fracturing fluid is
pumped downhole, under pressure, to cause one or more fractures in
the reservoirs. After the fractures have been formed the gel is
broken and the aqueous fracturing fluid is withdrawn from the
reservoir.
EXAMPLES
[0023] The effectiveness of the partially esterified,
polyalkoxylated polyols as oxidizing breaker retarders was
determined for a crosslinked guar gum system. The crosslinked gel
system contained 40 lbs per 1000 gallons of the guar gum, 10 lbs
per 1000 gallons of the potassium carbonate and 1 lb per 1000
gallons of the borate crosslinking agent. 0.125 lbs per 1000
gallons of the Na.sub.2S.sub.2O.sub.8was added to the crosslinked
gel as the oxidizing breaker. Different amounts of the POE(30)
sorbitol trioleate, which is sorbitol reacted with 30 moles of
ethylene oxide and then esterified with 3 moles of oleic acid, were
added as the oxidizing breaker retarder.
[0024] The samples were set in a 140.degree. F. oven and the
viscosity was measured after 0.5, 1, 2, and 3 hours. The data in
Table 1 indicates that the POE(30) Sorbitol Trioleate retards the
gel breaking rate of the oxidizing breaker. Using the same
oxidizing breaker concentration, the time required for the gel to
break is increased by increasing the amount of POE(30) Sorbitol
Trioleate. The sample without any oxidizing breaker remained a
complex gel after 3 hours at 140.degree. F. The sample with the
oxidizing breaker but without any POE(30) Sorbitol Trioleate was
reduced from complex gel to 7 cps in 2 hours. Samples containing
different amounts of POE(30) Sorbitol Trioleate demonstrated
retarded viscosity breaking proportional to the amount of POE(30)
Sorbitol Trioleate added
1TABLE 1 VISCOSITY (cps) @ 140.degree. F. Sample 0.5 hr 1.0 hr 2.0
hr 3.0 hr 1 C C C C 2 C WC 7 B 3 C C 14 B 4 C C 47 4 5 C C C 35
Note: Sample No. 1: Control, crosslinked guar gum system only
Sample No. 2: crosslinked guar gum system + oxidizing gel breaker
Sample No. 3: crosslinked guar gum system + oxidizing gel breaker +
2 gal/1000 gal POE(30) Sorbitol Trioleate as oxidizing breaker
retarder Sample No. 4: crosslinked guar gum system + oxidizing gel
breaker + 5 gal/1000 gal POE(30) Sorbitol Trioleate as oxidizing
breaker retarder Sample No. 3: crosslinked guar gum system +
oxidizing gel breaker + 10 gal/1000 gal POE(30) Sorbitol Trioleate
as oxidizing breaker retarder C = Complexed Gel WC = Weak Complexed
Gel B = Broke
[0025] Table 2 shows the effect of the degree of esterification and
the degree of ethoxylation on the oxidizing gel breaker
retardation. Different samples were prepared using sorbitol reacted
with from 20 to 40 moles of ethylene oxide and then esterified with
from 0 to 6 moles of oleic acid. The crosslinked gel system
contained 40 lbs per 1000 gallons of the guar gum, 10 lbs per 1000
gallons of potassium carbonate, 1 lb per 1000 gallons of the borate
crosslinking agent, 0.125 lbs per 1000 gallons of the
Na.sub.2S.sub.2O.sub.8, and 2.0 gallons per 1000 gallons of various
partially esterified, polyalkoxylated polyols. The viscosity was
measured after 1 hour at 140.degree. F. by the visual judgment
system as described in U.S. Pat. No. 5,393,810.
2TABLE 2 EFFECT OF DEGREE OF ESTERIFICATION/ALKOXYLATION ON
OXIDIZING GEL BREAKER RETARDATION Moles Acid/EO 20 24 26 28 30 36
40 0 B B B B B B B 1 B B B WC MC WC B 2 B B WC MC SC MC B 3 B WC MC
SC SC MC B 4 B B WC MC SC SC B 5 B B B WC MC MC B 6 B B B B B WC B
NOTE: B = Broke WC = Weak Complex MC = Medium Complex SC = Strong
Complex
[0026] As shown in Table 2, no gel breaking retardation was
observed using oxidizing breaker retarder with less than 20 moles
EO or more than 40 moles EO regardless of the degree of
esterification. The samples of Sorbitol with 30 moles EO and then
esterified with 2-4 moles of oleic acid showed the maximum
oxidizing breaker retardation in the crosslinked gel system.
[0027] Similar results to those obtained with oleic acid were found
when tall oil fatty acid, lauric acid, and stearic acid were used
instead of oleic acid indicating that the fatty acid used to
esterify the polyalkoxylated sorbitol was not as critical as the
degree of alkoxylation and esterification.
CONCLUSIONS
[0028] The partially esterified, polyalkoxylated polyols can be
used as oxidizing breaker retarders in aqueous gelled fracturing
systems. They moderate the effect of the oxidizing breaker(s)
according to their concentrations, the well treating conditions and
also by varying the degree of esterification and the degree of
alkoxylation of the product. The inclusion of partially esterified,
polyalkoxylated polyols in aqueous fracturing fluid compositions
containing an oxidizing breaker and the fracturing of subterranean
reservoirs using such formulations can better control the gel
breaking time and optimize the treatment results.
[0029] Although the description above contains many specifics these
should not be construed as limiting the scope of the invention but
as merely providing illustrations of some of the presently
preferred embodiments of this invention. Various other embodiments
and ramifications are possible within it's scope. For example,
other acids such as stearic, lauric and tall oil fatty acids may be
used. Alkoxylates may be formed using ethylene oxide and propylene
oxide, ethylene oxide and butylene oxide or ethylene oxide and both
butylene and propylene oxide, in various proportions. Other polyols
such as glycerine, polyglycerine, glucose, fructose, sucrose,
pentaerythritol, trimethylolpropane, and polymers of ethylene oxide
and propylene oxide may be used.
[0030] Thus the scope of the invention should be determined by the
appended claims and their legal equivalents, rather than by the
examples given.
* * * * *