U.S. patent application number 10/447591 was filed with the patent office on 2004-12-02 for methods of fracturing subterranean zones with less pumping.
Invention is credited to McMechan, David, Pauls, Richard W., Todd, Brad.
Application Number | 20040238169 10/447591 |
Document ID | / |
Family ID | 33451273 |
Filed Date | 2004-12-02 |
United States Patent
Application |
20040238169 |
Kind Code |
A1 |
Todd, Brad ; et al. |
December 2, 2004 |
Methods of fracturing subterranean zones with less pumping
Abstract
Methods of fracturing subterranean zones with less pumping are
provided. The methods basically comprise the steps of providing an
aqueous fracturing fluid comprised of a brine having a density in
the range of from about 9 to about 19 pounds per gallon, pumping
the aqueous fracturing fluid into the subterranean zone at a rate
and pressure sufficient to fracture the subterranean zone and
recovering the aqueous fracturing fluid from the subterranean
zone.
Inventors: |
Todd, Brad; (Duncan, OK)
; Pauls, Richard W.; (Duncan, OK) ; McMechan,
David; (Duncan, OK) |
Correspondence
Address: |
Robert A. Kent
Halliburton Energy Services
2600 South 2nd Street
Duncan
OK
73536
US
|
Family ID: |
33451273 |
Appl. No.: |
10/447591 |
Filed: |
May 29, 2003 |
Current U.S.
Class: |
166/280.2 ;
166/281; 166/308.3; 507/211; 507/213; 507/216; 507/266; 507/271;
507/273; 507/277; 507/924 |
Current CPC
Class: |
E21B 43/26 20130101 |
Class at
Publication: |
166/280.2 ;
166/281; 507/266; 507/277; 507/211; 507/213; 507/216; 507/271;
507/273; 507/924; 166/308.3 |
International
Class: |
E21B 043/267 |
Claims
1. A method of fracturing a subterranean zone penetrated by a well
bore comprising the steps of: (a) providing an aqueous fracturing
fluid that comprises a brine having a density in the range of from
about 9 to 19 pounds per gallon; (b) pumping said aqueous
fracturing fluid into said subterranean zone at a rate and pressure
sufficient to fracture said subterranean zone; and (c) recovering
said aqueous fracturing fluid from said subterranean zone.
2. The method of claim 1 wherein said brine is selected from the
group consisting of calcium chloride brine, calcium bromide brine,
sodium bromide brine, sodium chloride brine, potassium formate
brine, cesium formate brine, zinc chloride brine, zinc bromide
brine, and mixtures thereof.
3. The method of claim 1 wherein said brine is calcium chloride
brine.
4. A method of fracturing a subterranean zone penetrated by a well
bore comprising the steps of: (a) providing a viscous aqueous
fracturing fluid that comprises a brine having a density in the
range of from about 9 to about 19 pounds per gallon and a gelling
agent; (b) pumping said viscous aqueous fracturing fluid into said
subterranean zone at a rate and pressure sufficient to fracture
said subterranean zone; and (c) recovering said aqueous fracturing
fluid from said subterranean zone.
5. The method of claim 4 wherein said brine is selected from the
group consisting of calcium chloride brine, calcium bromide brine,
sodium bromide brine, sodium chloride brine, potassium formate
brine, cesium formate brine, zinc chloride brine, zinc bromide
brine, and mixtures thereof.
6. The method of claim 4 wherein said brine is calcium chloride
brine.
7. The method of claim 4 wherein said gelling agent is selected
from the group consisting of hydroxyethylcellulose, guar, xanthan
and succinoglycan.
8. The method of claim 4 wherein said gelling agent is xanthan.
9. The method of claim 4 wherein said gelling agent is present in
said aqueous fracturing fluid in an amount in the range of from
about 0.1% to about 2% by weight of said brine therein.
10. The method of claim 4 wherein said aqueous fracturing fluid
further comprises a cross-linking agent for cross-linking said
gelling agent.
11. The method of claim 10 wherein said cross-linking agent is
selected from the group consisting of sodium borate decahydrate,
zirconium oxychloride, calcium salts, aluminum salts, magnesium
salts, iron compounds, iodine compounds and baron compounds.
12. The method of claim 10 wherein said cross-linking agent is
sodium borate decahydrate.
13. The method of claim 10 wherein said cross-linking agent is
present in said aqueous fracturing fluid in an amount in the range
of from about 0.1% to about 66% by weight of said gelling agent
therein.
14. The method of claim 4 wherein said aqueous fracturing fluid
further comprises a proppant material.
15. The method of claim 14 wherein said proppant material is
selected from the group consisting of graded sand, sintered
bauxite, walnut hulls, and glass beads.
16. The method of claim 14 wherein said proppant material is graded
sand.
17. The method of claim 14 wherein at least part of said proppant
material is coated with a hardenable resin composition.
18. The method of claim 14 wherein said proppant material is
present in said aqueous fracturing fluid in an amount in the range
of from about 1 to about 18 pounds per gallon of said fracturing
fluid.
19. The method of claim 4 wherein said aqueous fracturing fluid
further comprises a delayed breaker for effecting a controlled
reduction in viscosity of said aqueous fracturing fluid.
20. The method of claim 19 wherein said delayed breaker is selected
from the group consisting of sodium perborate, potassium periodate,
sodium persulfate, t-butyl hydroperoxide, sodium bromate, lithium
hypochlorite, sodium hypochlorite and sodium chlorite.
21. The method of claim 19 wherein said delayed breaker is sodium
perborate.
22. The method of claim 19 wherein said delayed breaker is present
in said aqueous fracturing fluid in an amount in the range of from
about 0.01% to about 5% by weight of gelling agent therein.
23. A method of fracturing a subterranean zone penetrated by a well
bore comprising the steps of: (a) providing a viscous aqueous
fracturing fluid that comprises calcium chloride brine having a
density in the range of from about 9 to about 19 pounds per gallon,
a xanthan gelling agent present in said viscous fracturing fluid in
an amount in the range of from about 0.1% to about 2% by weight of
said brine therein, a graded sand proppant material present in said
viscous fracturing fluid in an amount in the range of from about 1
pound to about 18 pounds per gallon of said viscous fracturing
fluid, and a sodium perborate delayed breaker present in said
viscous aqueous fracturing fluid in an amount in the range of from
about 0.01% to about 5% by weight of said gelling agent therein;
(b) pumping said viscous aqueous fracturing fluid into said
subterranean zone at a rate and pressure sufficient to fracture
said subterranean zone; and (c) recovering said aqueous fracturing
fluid from said subterranean zone.
24. The method of claim 23 wherein said aqueous fracturing fluid
further comprises a cross-linking agent comprising sodium perborate
tetrahydrate present in said aqueous fracturing fluid in an amount
in the range of from about 0.01% to about 5% by weight of said
gelling agent therein.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to methods of fracturing
subterranean zones penetrated by well bores with reduced wellhead
pressures and hydraulic horsepower requirements.
[0003] 2. Description of the Prior Art
[0004] Hydraulic fracturing production stimulation treatments are
commonly utilized in subterranean hydrocarbon producing zones
penetrated by well bores. In such treatments a treating fluid,
referred to in the art as a fracturing fluid, is pumped through the
well bore into a subterranean zone to be treated at a rate and
pressure such that fractures are formed and extended into the
subterranean zone. The fracturing fluid carries particulate
proppant material, e.g., sand into the fractures which functions to
prevent the fractures from closing. That is, the proppant material
is deposited in the fractures when the fracturing fluid is broken
and recovered. As a result, the formed fractures are prevented from
closing whereby conductive channels are formed through which
produced fluids can flow to the well bore.
[0005] In order to pump a heretofore used fracturing fluid at a
rate and pressure sufficient to fracture a subterranean zone,
special elaborate pumping equipment in addition to the pumping
equipment used for drilling and cementing the well bore must
generally be utilized. The use of such pumping equipment is time
consuming and expensive to mobilize, set up and use.
[0006] Thus, there are needs for improved methods of fracturing
subterranean zones which utilize the pumping equipment available at
the well site or at least reduce the additional pumping equipment
required.
SUMMARY OF THE INVENTION
[0007] The present invention provides improved methods of
fracturing subterranean zones penetrated by well bores which meet
the needs described above and overcome the deficiencies of the
prior art. The methods basically comprise the following steps. An
aqueous fracturing fluid comprising a brine having a density in the
range of from about 9 to about 19 pounds per gallon is provided.
The fracturing fluid is pumped into the subterranean zone at a rate
and pressure sufficient to fracture the subterranean zone and the
fracturing fluid is recovered from the subterranean zone.
[0008] The methods of this invention eliminate the need for pumping
equipment in addition to the pumping equipment already at the well
site or substantially reduce the extra pumping equipment required
as a result of the aqueous fracturing fluid utilized having a very
high density. The pumping equipment that is generally associated
with a drilling rig is known in the art as "mud pumps." Off-shore
rigs also include additional pumping equipment known as the
"cementing unit." Mud pumps are high rate pumps that are usually
limited to wellhead pressures in the range of from about 2000 to
about 7000 psi. The high density of the fracturing fluid of this
invention produces a bottom hole pressure sufficient to fracture a
subterranean zone with considerably lower wellhead pressure and
hydraulic horsepower being required than when conventional lower
density fracturing fluids are utilized.
[0009] The objects, features and advantages of the present
invention will be readily apparent to those skilled in the art upon
a reading of the description of preferred embodiments which
follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0010] The present invention provides improved methods of
fracturing a subterranean zone penetrated by a well bore which
utilize lower wellhead pressures and reduced hydraulic horsepower
requirements. The methods basically comprise the following steps.
An aqueous fracturing fluid comprising brine having a density in
the range of from about 9 to about 19 pounds per gallon is
provided. The aqueous fracturing fluid is pumped into the
subterranean zone at a rate and pressure sufficient to fracture the
subterranean zone and the aqueous fluid is then recovered from the
subterranean zone.
[0011] Because the fracturing fluid has a density considerably
higher than prior art fracturing fluids, lower wellhead pressures
and reduced hydraulic horsepower are required. As a result,
fracturing procedures can be carried out in accordance with the
methods of this invention utilizing the pumping equipment available
at the well site or utilizing less auxiliary equipment than
otherwise would be required. As is understood by those skilled in
the art, the well head pressure equals the bottom hole treating
pressure minus the hydrostatic pressure plus the friction
pressure.
[0012] In addition to utilizing a high density brine fracturing
fluid to lower wellhead pressures and reduce the hydraulic
horsepower required, a larger work string through which the high
density brine fracturing fluid is pumped can be utilized to further
lower pressures and reduce horsepower. For example, instead of a 3"
inside diameter work string, a 4" inside diameter work string or
larger can be utilized.
[0013] Also, most mud pumps are incapable of pumping a fracturing
fluid containing proppant material, e.g., graded sand for propping
the fractures open. In order to prevent the use of additional
pumping equipment on off-shore rigs, the rig cementing unit can be
used to pump a high proppant material concentration slurry and the
mud pumps can be used to pump the high density brine fracturing
fluid with the two streams being metered together.
[0014] The brines which can be used in accordance with this
invention and that have densities in the range of from about 9 to
about 19 pounds per gallon include, but are not limited to, calcium
chloride brine, calcium bromide brine, sodium bromide brine, sodium
chloride brine, potassium formate brine, cesium formate brine, zinc
chloride brine, zinc bromide brine, and mixtures thereof. Of these,
calcium chloride brine is preferred.
[0015] In order to increase the viscosity of the brine and thereby
form a viscous aqueous fracturing fluid, a gelling agent can
optionally be combined with the brine. The gelling agents which can
be utilized include, but are not limited to, hydroxyethylcellulose,
guar, xanthan and succinoglycan. Of these, xanthan is preferred.
When used, the gelling agent is included in the aqueous fracturing
fluid in a general amount in the range of from about 0.1% to about
2% by weight of the brine in the aqueous fracturing fluid, most
preferably in an amount of about 0.5%.
[0016] In some fracturing applications wherein a higher viscosity
fracturing fluid is required than that produced by a gelling agent
alone, a cross-linking agent can be included in the fracturing
fluid. The cross-linking agent cross-links the gelling agent in the
fracturing fluid which has the effect of substantially increasing
the viscosity of the fracturing fluid. Examples of cross-linking
agents which can be utilized include, but are not limited to,
sodium borate decahydrate, zirconium oxychloride, calcium salts,
aluminum salts, magnesium salts, iron compounds, iodine compounds,
and boron compounds. Of these, sodium borate decahydrate is
preferred. When used, the cross-linking agent is included in the
aqueous fracturing fluid in an amount in the range of from about
0.1% to about 66% by weight of the gelling agent in the aqueous
fracturing fluid, more preferably in an amount of about 1.5%.
[0017] In fracturing operations wherein proppant material is placed
in the created fractures, the proppant material is usually
suspended in a viscosified end portion of the fracturing fluid.
After placement of the fracturing fluid containing the proppant
material, the fracturing fluid is broken whereby it reverts to a
thin fluid and the proppant material is deposited in the fractures.
The proppant material functions to prevent the formed fractures
from closing whereby conductive channels are formed through which
produced fluids can flow to the well bore. Examples of proppant
material which can be used include, but are not limited to, graded
sand, sintered bauxite, walnut hulls, and glass beads. Of these,
graded sand is preferred. The proppant material utilized is
generally present in the aqueous fracturing fluid in an amount in
the range of from about 1 to about 18 pounds per gallon of the
fracturing fluid.
[0018] All or part of the proppant material in the fracturing fluid
can be coated with a delayed hardenable resin composition whereby
after the proppant material is deposited in the fractures, the
hardenable resin composition hardens and consolidates the proppant
material into one or more permeable packs having high compressive
strengths.
[0019] As mentioned, when a viscous aqueous fracturing fluid or a
viscous portion of an aqueous fracturing fluid is utilized, it can
include a delayed breaker for effecting a controlled reduction in
the viscosity of the aqueous fracturing fluid so that the proppant
material is deposited in the fractures and the fracturing fluid is
recovered. Examples of delayed breakers which can be utilized
include, but are not limited to, sodium perborate, potassium
periodate, sodium persulfate, t-butyl hydroperoxide, sodium
bromate, lithium hypochlorite, sodium hypochlorite, and sodium
chlorite. Of these, sodium perborate is preferred. When used, the
delayed breaker is included in the aqueous fracturing fluid in an
amount in the range of from-about 0.01% to about 5% by weight of
gelling agent in the aqueous fracturing fluid, more preferably in
an amount of about 1%.
[0020] A preferred method of this invention for fracturing a
subterranean zone penetrated by a well bore comprises the steps of:
(a) providing an aqueous fracturing fluid comprising a brine having
a density in the range of from about 9 to about 19 pounds per
gallon; (b) pumping the aqueous fracturing fluid into the
subterranean zone at a rate and pressure sufficient to fracture the
subterranean zone; and (c) recovering the aqueous fracturing fluid
from the subterranean zone.
[0021] Another preferred method of this invention for fracturing a
subterranean zone penetrated by a well bore comprises the steps of:
(a) providing a viscous aqueous fracturing fluid comprising a brine
having a density in the range of from about 9 to about 19 pounds
per gallon and a gelling agent; (b) pumping the viscous aqueous
fracturing fluid into the subterranean zone at a rate and pressure
sufficient to fracture the subterranean zone; and (c) recovering
the viscous aqueous fracturing fluid from the subterranean
zone.
[0022] Still another preferred method of this invention for
fracturing a subterranean zone penetrated by a well bore comprises
the steps of: (a) providing a viscous aqueous fracturing fluid
comprising calcium chloride brine having a density in the range of
from about 9 to about 19 pounds per gallon, a xanthan gelling agent
present in the viscous aqueous fracturing fluid in an amount in the
range of from about 0.1% to 2% by weight of the brine therein, a
graded sand proppant material present in the viscous aqueous
fracturing fluid in an amount in the range of from about 1 pound to
about 18 pounds per gallon of the viscous aqueous fracturing fluid
and a sodium perborate delayed breaker present in the viscous
aqueous fracturing fluid in an amount in the range of from about
0.01% to about 5% by weight of gelling agent therein; (b) pumping
the viscous aqueous fracturing fluid into the subterranean zone at
a rate and pressure sufficient to fracture the subterranean zone;
and (c) recovering the aqueous fracturing fluid from the
subterranean zone.
[0023] In order to further illustrate the methods and aqueous
treating fluids of the present invention, the following example is
given.
EXAMPLE 1
[0024] Wellhead pressures were calculated for water (8.33 lb/gal
density and 0.9 cP viscosity) and brine (12 lb/gal density and 4 cP
viscosity) at various flow rates through 3" ID and 4" ID pipe
strings disposed in a 10,000 ft well having a fracture gradient of
0.75 psi/ft. The wellhead pressures for the water and brine were
calculated for pure water and brine, for water and brine including
succinoglycan polymer at a concentration of 35 lb/1000 gal and for
water and brine including xanthan polymer at a concentration of 35
lb/1000 gal. The results of the calculations are set forth in Table
1 below.
1TABLE 1 Wellhead Pressure Calculations Rate Well Head Pressure,
psi bbls/ Pipe ID, No Polymer Succinoglycan Xanthan min inches
Water Brine Water Brine Water Brine 1 3 3194 1305 3265 1359 3297
1391 5 3 3573 1960 3336 1549 3400 1660 10 3 4650 3732 3813 2335
3723 2185 20 3 8761 10225 5670 5270 4862 3974 30 3 15464 20535 8724
9968 6636 6696 1 4 3178 1276 3230 1323 3245 1338 5 4 3270 1439 3255
1348 3290 1451 10 4 3525 1872 3310 1502 3340 1554 20 4 4482 3432
3774 2260 3587 1952 30 4 6024 5875 4556 3502 3960 2539
EXAMPLE 2
[0025] Example 1 was repeated except that the brine had a density
of 15 lb/gal and a viscosity of 10 cP. The results of the
calculations are set forth in Table 2 below.
2TABLE 2 Wellhead Pressure Calculations Rate, Pipe Well Head
Pressure, psi bbls/ ID, in- No Polymer Succinoglycan Xanthan min
ches Water Brine Water Brine Water Brine 1 3 3194 -234 3265 -200
3297 -168 5 3 3573 702 3336 113 3400 272 10 3 4650 3176 3813 1211
3723 1001 20 3 8761 12036 5670 5218 4862 3434 30 3 15464 25855 8724
11516 6636 7076 1 4 3178 -277 3230 -235 3245 -220 5 4 3270 -42 3255
-210 3290 -24 10 4 3525 571 3310 43 3340 118 20 4 4482 2737 3774
1098 3587 666 30 4 6024 6074 4556 2797 3960 1467
[0026] From the Tables, it can be seen that the well head pressure
of brine is lower than the well head pressure of water at rates up
to and including 20 bbls/min. Also, it can be seen that the well
head pressure of brine containing succinoglycan or xanthan polymers
is lower than the well head pressure of water at rates up to and
including 30 bbls/min.
[0027] Thus, the present invention is well adapted to carry out the
objects and attain the ends and advantages mentioned as well as
those which are inherent therein. While numerous changes can be
made by those skilled in the art, such changes are encompassed
within the spirit of this invention as defined by the appended
claims.
What is claimed is:
* * * * *