U.S. patent application number 12/029995 was filed with the patent office on 2008-08-14 for fracture clean up method.
Invention is credited to Jonathan Abbott, Evgeny Borisovich Barmatov, Alexander Victorovich Golovin, Konstantin Mikhailovich Lyapunov.
Application Number | 20080190610 12/029995 |
Document ID | / |
Family ID | 39684847 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080190610 |
Kind Code |
A1 |
Barmatov; Evgeny Borisovich ;
et al. |
August 14, 2008 |
Fracture Clean up Method
Abstract
Methods including the pumping of fracturing fluid carrying
proppant. Simultaneously particulate is pumped made of substance
that under subterranean temperature releases hydrochloric or
etching acid precursor, wherein the said acid precursor reacts with
the formation water and produces acid. The methods stimulate the
inflow of formation fluid towards the well due to cleaning of the
surface of hydrofracture and due to growth of its area.
Inventors: |
Barmatov; Evgeny Borisovich;
(Sipachi, RU) ; Lyapunov; Konstantin Mikhailovich;
(Novosibirsk, RU) ; Golovin; Alexander Victorovich;
(Livny, RU) ; Abbott; Jonathan; (Didlot,
GB) |
Correspondence
Address: |
SCHLUMBERGER TECHNOLOGY CORPORATION;David Cate
IP DEPT., WELL STIMULATION, 110 SCHLUMBERGER DRIVE, MD1
SUGAR LAND
TX
77478
US
|
Family ID: |
39684847 |
Appl. No.: |
12/029995 |
Filed: |
February 12, 2008 |
Current U.S.
Class: |
166/280.2 |
Current CPC
Class: |
C09K 8/70 20130101; E21B
43/267 20130101; E21B 37/00 20130101; C09K 8/52 20130101; C09K 8/72
20130101 |
Class at
Publication: |
166/280.2 |
International
Class: |
E21B 43/267 20060101
E21B043/267 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 13, 2007 |
RU |
2007105188 |
Claims
1. A method for fracture clean up that includes the delivery to the
fracture of a substance capable to produce inorganic acid; the
fracture is propped by a mixture of proppant and particulate that
produces hydrochloric acid precursor under subterranean conditions
and due to reaction with formation fluid.
2. The method in accordance with claim 1, wherein the particulate
is particles of polyvinylchloride and/or its copolymers.
3. The method in accordance with claim 1, wherein the particulate
is particles of polyvinyldenchloride.
4. The method in accordance with claim 3, wherein the granulated
ammonium chloride or fluoride coated with oil-soluble composition
is employed.
5. The method in accordance with claim 1, wherein the particulate
is particles of copolymers of polyvinyldenchloride.
6. The method in accordance with claim 5, wherein the granulated
ammonium chloride or fluoride coated with oil-soluble composition
is employed.
7. The method in accordance with claim 1, wherein the particulate
is particles of polyvinyldenchloride and its copolymers.
8. The method in accordance with claim 7, wherein the granulated
ammonium chloride or fluoride coated with oil-soluble composition
is employed.
9. A method for fracture clean up that includes the delivery to the
fracture of a substance capable to produce inorganic acid; the
fracture is propped by a mixture of proppant and particulate that
produces etchingc acid precursor under subterranean conditions and
due to reaction with formation fluid.
10. The method in accordance with claim 9, wherein the particulate
is particles of polyvinylchloride and/or its copolymers.
11. The method in accordance with claim 9, wherein the particulate
is particles of polyvinyldenchloride.
12. The method in accordance with claim 11, wherein the granulated
ammonium chloride or fluoride coated with oil-soluble composition
is employed.
13. The method in accordance with claim 9, wherein the particulate
is particles of copolymers of polyvinyldenchloride.
14. The method in accordance with claim 13, wherein the granulated
ammonium chloride or fluoride coated with oil-soluble composition
is employed.
15. The method in accordance with claim 9, wherein the particulate
is particles of polyvinyldenchloride and its copolymers.
16. The method in accordance with claim 15, wherein the granulated
ammonium chloride or fluoride coated with oil-soluble composition
is employed.
17. The method in accordance with 11 wherein the particulate size
varies from 0.1 microns to 10 mm.
18. The method in accordance with 11 wherein the content of
polyvinylchloride and polyvinyldenchloride in copolymers is from
0.1 wt. % to wt. 99.9%.
19. The method in accordance with 11 wherein the content of
chlorine in particulates is from 0.01wt. % to wt. 85%.
20. The method in accordance with 11 wherein the mass proportion of
particulates to the mass of proppant is from 0.1wt. % to wt.
99.9%.
21. The method in accordance with 1 wherein the particulate size
varies from 0.1 microns to 10 mm.
22. The method in accordance with 1 wherein the content of
polyvinylchloride and polyvinyldenchloride in copolymers is from
0.1 wt. % to wt. 99.9%.
23. The method in accordance with 1 wherein the content of chlorine
in particulates is from 0.01 wt. % to wt. 85%.
24. The method in accordance with 1 wherein the mass proportion of
particulates to the mass of proppant is from 0.1 wt. % to wt.
99.9%.
Description
[0001] This application claims foreign priority benefits to Russian
Patent Application No. 2007105188, filed on Feb. 13, 2007.
BACKGROUND
[0002] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0003] This invention relates to the oil and gas industry, and in
particular, to methods of oil and gas production, and can be
applied to improve hydrocarbon recovery from a fractured
subterranean reservoir due to fracture clean up.
[0004] The method of hydraulic fracturing of oil-bearing formation
is an efficient method for stimulation of oil/gas production from a
well. The goal of hydraulic fracturing is to pump a fluid under the
pressure and rate sufficient for cracking the formation of the
reservoir; this creates two fractures on opposite sides of wellbore
traveling in opposite directions. These large-scale fractures are
required as conduits for draining of hydrocarbon fluids into the
borehole; these conduits have a higher fluid conductivity than the
formation itself. To prevent the fracture closing when the fluid
pumping has ended, propping agents are delivered with the fluid
into the fractures. This proppant particulate is carried into the
formation by fracturing fluid with a required certain density and
viscosity. The preferable variant of fracturing fluid is viscous
solution of viscoelastic polymers (guar or
hydroxypropylcellulose).
[0005] The disadvantage of traditional fracturing methods is
damaging the fracture with polymers and products of their
decomposition. The residue of undamaged polymer stays in pores and
considerably reduces fracture permeability. Research data shows
that 45 to 75% of polymer remains in the fracture after an initial
flowback period. To counteract this damage breakers are used to
reduce gel viscosity and help remove concentrated polymer
residues.
[0006] Some methods are known where low-molecular oxidizers
(persulfates/peroxides of metals or ammonium) or organic peroxides
are applied as gel breaker. These oxidizers and peroxides are
effective up to 120.degree. C. Sometimes these breakers are poorly
compatible with the fracturing fluid or with resin coated
proppant.
[0007] Some methods describe treatment of near-wellbore zone with
hydrochloric acid pumped. This method is not adapted for removal of
gel and filter cake damage from propped fractures.
[0008] Other methods a method for acid treatment of the
near-wellbore zone. A mixture of polyvinylchloride and ammonium
bifluoride is thermally decomposed (due to in-situ ignition or
impact of formation temperature) and produces acid. The resulting
mixture of acids is used to break apart the colloidal sediments of
ferrous oxide. This method has not been adapted for removal of gel
and filter cake damage from propped fractures because is only used
to treat the near-wellbore zone.
[0009] Also known is a method of using acid to dissolve filter cake
via a proppant with coating made of organic acid precursor (e.g.,
polylactic acid). This method may also be applied to aid with gel
cleanup in gravel packs. The solid acid precursor can make up to
10% by weight of the total proppant mass. This invention is the
most similar to the disclosed invention.
[0010] There are many known methods for production improvement
after stimulation, by removal of concentrated gel and filter cake
from a propped fracture. Removal of gel damage is achieved by using
of polymers that are capable to produce organic or nonorganic acids
under subterranean conditions.
DESCRIPTION OF THE INVENTION
[0011] At the outset, it should be noted that in the development of
any such actual embodiment, numerous implementation-specific
decisions must be made to achieve the developer's specific goals,
such as compliance with system related and business related
constraints, which will vary from one implementation to another.
Moreover, it will be appreciated that such a development effort
might be complex and time consuming but would nevertheless be a
routine undertaking for those of ordinary skill in the art having
the benefit of this disclosure.
[0012] The description and examples are presented solely for the
purpose of illustrating the preferred embodiments of the invention
and should not be construed as a limitation to the scope and
applicability of the invention. While the compositions of the
present invention are described herein as comprising certain
materials, it should be understood that the composition could
optionally comprise two or more chemically different materials. In
addition, the composition can also comprise some components other
than the ones already cited. In the summary of the invention and
this detailed description, each numerical value should be read once
as modified by the term "about" (unless already expressly so
modified), and then read again as not so modified unless otherwise
indicated in context. Also, in the summary of the invention and
this detailed description, it should be understood that a
concentration range listed or described as being useful, suitable,
or the like, is intended that any and every concentration within
the range, including the end points, is to be considered as having
been stated. For example, "a range of from 1 to 10" is to be read
as indicating each and every possible number along the continuum
between about 1 and about 10. Thus, even if specific data points
within the range, or even no data points within the range, are
explicitly identified or refer to only a few specific, it is to be
understood that inventors appreciate and understand that any and
all data points within the range are to be considered to have been
specified, and that inventors possession of the entire range and
all points within the range.
[0013] The current invention describes a method for cleaning up a
propped fracture by aiding the breakdown and removal of gel and gel
residue from the fracture.
[0014] The technical benefit of this method is the improved fluid
mobility into and inside the propped fracture and therefore
enhancement of hydrocarbon production from the fracture.
[0015] The said technical result is achieved by the following
means: the fracturing fluid carries proppant and particulate into
the propped fracture; the said particulate under formation
temperature releases a substance that reacts with the formation
fluid and produces hydrochloric or etching acid. The preferable
embodiment of this patent uses the particles of polyvinyl chloride
or polyvinylden chloride or their copolymers comprising monomers of
vinyl chloride or vinylden chloride, as well as their chlorinate
analogs. Another variant is the use of material granulated and
encapsulated into oil-dissolving coating; the said material is
ammonium chloride or fluoride, ammonium difluoride, pyridine
fluoride, and fluoride-bearing polymers, e.g., fluoride of
polyvinylpyridine. The usual size of polymer particulate varies
from 0.1 microns to 10 mm. The preferable amount of vinyl chloride
is from 0.1% to 99.9% wt., and the content of chloride in the
polymer is from 0.01% to 85% wt. The proportion of polymeric
particulate as a percentage of proppant mass varies from 0.1% to
99.9%.
[0016] The method is based on using the substances which release
hydrochloride under conditions of the formation temperature and in
a water-oil medium; the produced hydrogen chloride destroys the
polymer gel and dissolves the gel residue, typically filter cake.
The disclosed method is based on using a new material for this
technique (preferably, polyvinylchloride or co-polymers).
BRIEF DESCRIPTION OF THE DRAWING
[0017] FIG. 1 shows the diagram that illustrate a loss of polymer
mass over the time of the thermal treatment.
[0018] These new substances enable efficient cleanup of polymers
typically used in hydraulic fracturing fluid by removal of
concentrated gel and gel residues, such as filter cake. The
advantages of using a polymer based on vinylchloride monomer in
contrast to other methods of destruction the polymer gel in propped
fractures are the following:
[0019] 1. It is possible to reduce the concentration of costly gel
breakers or abandon their use completely.
[0020] 2. The yield of hydrogen chloride from the said polymeric
material is a long-term process (tens of days). A long time
interval facilitates more uniform distribution of produced
hydrochloric acid over the fracture volume and ensures more
complete breaking of polymer gel.
[0021] 3. The particulate of polymer based on vinylchloride monomer
releases hydrogen chloride at elevated temperatures (130 . . .
200.degree. C.), where most commercially available peroxide
breakers lose effectiveness (e.g., peroxide and persulfate of metal
or ammonium).
[0022] 4. Unlike common peroxide breakers, the polymer particles
with vinylchloride monomers do not react with resin coated proppant
(RCP) or reduce the strength of the proppant packing that can lead
to a reduction of fracture width.
[0023] 5. Unlike peroxide-type (persulfate-type) gel breakers, the
polymer particles with vinylchloride monomers are non-reactive with
the fracturing fluid during the fracturing process and fracture
closure; the particulate does not affect the rheology of fracturing
fluids or solids transport properties.
[0024] 6. Hydrogen chloride released from particulates with
vinylchloride monomers can dissolve a carbonate rock and create
microchannels in the formation. This creates a divaricated system
of drainage and improves the hydrocarbon flow towards the
wellbore.
[0025] 7. Hydrogen chloride released from polymer particulates can
dissolve the filter cake formed during filtration on gel by the
rock matrix.
[0026] If other types of substances meet the conditions formulated
in the independent claim of the invention formula, the advantages
must be the same.
[0027] A new method of conducting of hydraulic fracturing is
disclosed in the following claims; according to this method,
proppant is delivered to the fracture with a mixture polymer
particles (polyvinylchloride or copolymers of vinylchloride),
wherein the main proppant and polymeric particulate can be mixed
before the job or on-the-fly and then delivered to the subterranean
formation. Under the conditions of high subterranean temperature
the polymeric material produces hydrogen chloride that destroys the
network of intermolecular cross-links in the polymer gel; the said
cross-linked network is formed due to intermolecular bonds between
hydroxyl groups of polymer gel and ions of multivalent metals (the
cross-linking agents). The produced hydrogen chloride breaks the
gel and improves the water solubility of polymer components
suspended in the fracturing fluid; this reduces the viscosity of
fracturing solution. In general, the said factors facilitate a more
complete cleanup of polymer gel from the fracture and improve the
fracture permeability. In addition, the method ensures dissolving
of the filer cake and formation of micro channels in the formation;
the later creates a divaricated system of drainage and facilitates
the flow of hydrocarbons towards the wellbore.
[0028] The molar concentration of vinylchloride monomer units in a
copolymer varies from about 0.1% to about 99.9%.
[0029] The copolymer may include plasticizers, thermostability
agents, and organic and inorganic compounds.
[0030] Other organic or inorganic compounds can be used for the
same purpose if they produce hydrogen chloride or hydrogen fluoride
under formation conditions; the released hydrogen chloride or
hydrogen fluoride combine in water to form hydrochloric acid or
etching acid.
[0031] In the method disclosed, the particles of polymeric material
can be employed during the entire operation of hydrofracturing or
at the final stages.
EXAMPLES
[0032] The application feasibility of the method disclosed was
proven by example using a polymer with vinylchloride monomers
placed under conditions imitating the conditions of a producing oil
well.
[0033] The release of hydrogen chloride by polyvinylchloride was
proven by the following experiment. A sample of polyvinylchloride
was stored for several days at a high temperature (110.degree. C.)
in crude oil. The polyvinylchloride sample initially had a glass
transition temperature of 56.degree. C. and crystalline degree
equal to 12%. There was no plasticizer in the composition.
[0034] The evolution of sample weight during 1-32 days (showed on
the abscissa axis) is plotted in the FIG. 1 (the sample mass is on
the left ordinate axis). It is apparent in this diagram that over
the time of the thermal treatment there is loss of polymer mass
showed on the left ordinate axis. The data of elementary analysis
(carbon, hydrogen, chlorine) for initial sample and current state
of degraded sample demonstrated that the mass loss of the
polyvinylchloride correlates with the production of hydrogen
chloride, showed on the right ordinate axis in gram
[0035] For example, a sample of polyvinylchloride with the initial
mass of 0.100 kg was stored for the period of 19 days at
temperature of 110.degree. C. and produced 0.029 kg of hydrogen
chloride, which is equivalent to 0.193 kg of hydrochloric acid with
concentration 15%. This quantity of acid is enough to dissolve of
0.042 kg calcite rock, a typical component of carbonate
formations.
[0036] Advantages of the disclosed method in comparison to known at
the art are the following:
[0037] 1. It is possible to reduce the concentration or abandon
completely the costly gel breakers.
[0038] 2. The yield of hydrogen chloride from the said polymeric
material is a long-run process (tens of days). A long time interval
facilitates more uniform distribution of produced hydrochloric acid
over the fracture volume and ensures more complete breaking of
polymer gel.
[0039] 3. The particulate of polymer based on vinylchloride monomer
effectively releases hydrogen chloride at elevated temperature of
formation (130 . . . 200.degree. C.), when most of commercially
available peroxide gel breakers (e.g., peroxide and persulfate of
metal or ammonium) fail.
[0040] 4. Unlike common peroxide-type gel breakers, the polymer
particles with vinylchloride monomers does not react with
components of resin coated proppant and therefore should not damage
the proppant pack strength which can lead to a reduction of
fracture width.
[0041] 5. Unlike peroxide-type (persulfate-type) gel breakers, the
polymer particles with vinylchloride monomers do not react with
fracturing fluids during any stage of the fracturing process or
during fracture closure; the particulate will not affect the
rheology of fracturing fluid or proppant transport properties.
[0042] 6. Hydrogen chloride or hydrogen fluoride released from
particulates can dissolve a carbonate rock and create micro
channels in the formation. This creates a divaricated system of
drainage and facilitates the flow of hydrocarbons towards the
wellbore.
[0043] 7. Hydrogen chloride or hydrogen fluoride released from
polymer particulates is capable of filter cake removal because
these particles will be trapped inside the fracture, near the
fracture surface.
* * * * *