U.S. patent application number 16/867121 was filed with the patent office on 2020-08-20 for method of reducing fluid loss in formations.
The applicant listed for this patent is Maersk Olie Og Gas A/S. Invention is credited to Jens Henrik Hansen, Anne Ladegaard SKOV.
Application Number | 20200263517 16/867121 |
Document ID | 20200263517 / US20200263517 |
Family ID | 1000004799191 |
Filed Date | 2020-08-20 |
Patent Application | download [pdf] |
United States Patent
Application |
20200263517 |
Kind Code |
A1 |
SKOV; Anne Ladegaard ; et
al. |
August 20, 2020 |
METHOD OF REDUCING FLUID LOSS IN FORMATIONS
Abstract
The present invention relates to a method of providing a barrier
in a fracture-containing system, comprising: i) Providing a
treatment fluid comprising: a) a base fluid; b) an elastomeric
material, wherein said elastomeric material comprises at least one
polymer capable of crosslinking into an elastomer, and c) at least
one crosslinking agent; ii) Placing the treatment fluid in a
fracture-containing system; iii) Allowing the elastomeric material
to crosslink with itself to form a barrier in said
fracture-containing system; wherein the elastomeric material and/or
the crosslinking agent are of neutral buoyancy with regard to the
base fluid. The invention is contemplated to having utility not
only in the oil-drilling industry but also in the plugging of
fractures in sewer drains, pipelines etc.
Inventors: |
SKOV; Anne Ladegaard;
(Frederiksberg, DK) ; Hansen; Jens Henrik; (Doha,
QA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Maersk Olie Og Gas A/S |
Copenhagen O |
|
DK |
|
|
Family ID: |
1000004799191 |
Appl. No.: |
16/867121 |
Filed: |
May 5, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15644291 |
Jul 7, 2017 |
10683723 |
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16867121 |
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14648039 |
May 28, 2015 |
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PCT/EP2013/075002 |
Nov 28, 2013 |
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15644291 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09K 8/575 20130101;
C09K 8/516 20130101; E21B 33/138 20130101; C09K 8/426 20130101;
C09K 8/512 20130101 |
International
Class: |
E21B 33/138 20060101
E21B033/138; C09K 8/42 20060101 C09K008/42; C09K 8/575 20060101
C09K008/575; C09K 8/516 20060101 C09K008/516; C09K 8/512 20060101
C09K008/512 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2012 |
EP |
12195086.9 |
Feb 8, 2013 |
EP |
13154600.4 |
Claims
1. A method of providing a barrier in a fracture-containing system,
comprising: i) Providing a treatment fluid comprising: a) a base
fluid; b) an elastomeric material, wherein said elastomeric
material comprises at least one polymer capable of crosslinking
into an elastomer, and c) at least one crosslinking agent; ii)
Placing the treatment fluid in a fracture-containing system; iii)
Allowing the elastomeric material to crosslink with itself and with
the crosslinking agent to form a barrier in said
fracture-containing system; wherein the elastomeric material and/or
the crosslinking agent are of neutral buoyancy with regard to the
base fluid.
2. The method according to claim 1, wherein at least one of the
elastomeric material or the crosslinking agent is present in the
form of particles.
3. The method according to any one of the preceding claims, wherein
at least the elastomeric material is present in the form of
particles of elastomeric material.
4. The method according to any one of the preceding claims, wherein
the elastomeric material comprises one or more components selected
from the group consisting of natural rubber, acrylate butadiene
rubbers, polyacrylate rubbers, isoprene rubbers, chloroprene
rubbers, butyl rubbers, brominated or chlorinated butyl rubbers,
chlorinated polyethylene, neoprene rubbers, styrene butadiene
copolymer rubbers, sulphonated polyethylene, ethylene oxide
copolymers, ethylene-propylene rubbers, ethylene-propylene-diene
terpolymer rubbers, ethylene vinyl acetate copolymers,
fluorosilicone rubber, silicone rubbers, poly 2,2,1-bicyclo
heptane, alkylstyrene, crosslinked substituted vinyl acrylate
copolymers and diatomaceous earth, nitrile rubbers, hydrogenated
nitrile rubbers, fluoro rubbers, perfluoro rubbers,
tetrafluoroethylene/propylene, starch-polyacrylate acid graft
copolymers, polyvinyl alcohol-cyclic acid anhydride graft
copolymers, isobutylene maleic anhydride, acrylic acid type
polymers, vinylacetate-acrylate copolymer, polyethylene oxide
polymers, carboxymethyl cellulose type polymers,
starch-polyacrylonitrile graft copolymers, polymethacrylate,
polyacrylamide, and acrylic polymers, preferably wherein the
elastomeric material comprises one or more components selected from
the group consisting of natural rubber, acrylate butadiene rubbers,
polyacrylate rubbers, isoprene rubbers, chloroprene rubbers, butyl
rubbers, fluorosilicone rubber, silicone rubbers, and acrylic
polymers, more preferably silicone rubbers.
5. The method according to any one of claims 2-4, wherein the
elastomeric material is partially cured before mixing of said
material with the crosslinking agent and the base fluid to form the
treatment fluid.
6. The method according to any one of claims 2-5, wherein the
particles of the elastomeric material comprise an outer layer of a
first thermoplastic material.
7. The method according to any one of the preceding claims, wherein
the crosslinking agent is present in the form of particles.
8. The method according to claim 7, wherein the particles of the
crosslinking agent comprise an outer layer of a second
thermoplastic material.
9. The method according to any one of the preceding claims, wherein
the elastomeric material is a Polydimethylsiloxane (PDMS) rubber
and the crosslinking agent is a
methylhydrosiloxane-dimethylsiloxane copolymer.
10. The method according to any one of the preceding claims,
wherein the first and second thermoplastic material, independently
of each other, is selected from the group consisting of polyalkyl
methacrylate, such as polymethyl methacrylate (PMMA), fluorinated
polyalkyl methacrylate, such as heptafluorbutyl methacrylate
(HFBMA), copolymers of polyalkyl methacrylate and fluorinated
polyalkyl methacrylate, such as copolymers of polymethyl
methacrylate (PMMA) and heptafluorbutyl methacrylate (HFBMA),
polyester, polyurethane, polyvinyl acetate, polyvinyl chloride
(PVC), poly(acrylonitrile), poly(tetrahydrofuran) (PTHF),
styrene-acrylonitrile, polyethylene terephthalate,
polycyclohexylene dimethylene terephthalate, polyhydroxyalkanoates,
chlorinated polyethylene, polyimide, polylactic acid, polyphenylene
oxide, polyphthalamide, and polypropylene, preferably polymethyl
methacrylate (PMMA), preferably wherein the first and second
thermoplastic materials are both PMMA.
11. The method according to any one of the preceding claims,
wherein said base fluid is selected from the group consisting of a
gas, an aqueous fluid or an oleaginous fluid, preferably water or a
hydrocarbon fluid, more preferably water.
12. The method according to any one of the preceding claims,
wherein in step iii) the elastomeric material is allowed to
crosslink with the addition of energy, wherein said energy is
provided in the form of irradiation.
13. A treatment fluid comprising: a) a base fluid; b) an
elastomeric material, wherein said elastomeric material comprises
at least one polymer capable of crosslinking into an elastomer, and
c) at least one crosslinking agent; wherein the elastomeric
material and/or the crosslinking agent are of neutral buoyancy with
regard to the base fluid.
14. A use of a treatment fluid according to claim 13 for fracture
blocking, preferably for fracture blocking in an oil drilling well.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method of reducing fluid
loss in formations such as a subterranean formation or water or
sewer systems. More particularly the present invention relates to a
method of providing a barrier in a fracture-containing system. The
invention is contemplated to having utility not only in the
oil-drilling industry but also in the plugging of fractures in
sewer drains etc.
BACKGROUND OF THE INVENTION
[0002] In subterranean oil reservoirs the oil is often present in
zones or layers. There are many factors, such as voids, fractures
etc. which may lead to a fluid loss and complicate the recovery of
the oil. Thus the recovery of oil will be largely affected by the
heterogeneity of rock such a high permeability channels, voids and
fractures. When fluids, such as water, flow through the oil
reservoir consisting of rock of varying permeability, a higher
percentage of the fluid tends to flow in the sections with higher
permeability.
[0003] It would be desirable to control or prevent the passage of
fluid through a portion of a subterranean formation and/or isolate
specific areas in a subterranean formation or a well-bore.
Similarly, in water systems or sewer drains etc. it would be
desirable to be able to plug any leakages in a simple and
cost-effective manner.
[0004] Hydrolyzed polyacrylamide (HPAM) has been applied to block
high permeability channels and fractures due to its low price and
high efficiency in blocking the high permeability channels and
fractures by crosslinking with a chromium compound (Seright, R. S.
& Recovery, P. An Alternative View of Filter-Cake Formation in
Fractures Inspired by Cr (III)-Acetate-HPAM Gel Extrusion, SPE
Journal 18, 65-72 (2003). However, with high efficiency in
blocking, HPAM also blocks the pores inside the rock in an oil
field. As a result oil recovery will become less efficient due to
decreasing permeability of the pores.
[0005] WO 2007/141519 A2 discloses silicone-tackifier matrixes and
methods of use thereof by providing a treatment fluid that
comprises a base fluid and a silicone-tackifier matrix composition
that comprises at least one silicone polymer component, at least
one tackifying agent, and at least one curing agent and/or at least
one cross linking agent, placing the treatment fluid in a
subterranean formation, and allowing the silicone-tackifier matrix
to form at least one silicone-tackifier matrix therein.
[0006] WO 2007/010210 discloses a method of servicing a wellbore in
contact with a subterranean formation comprising placing a sealing
agent and a nonaqueous carrier fluid in the wellbore, placing a
nonaqueous activating fluid in the wellbore, and contacting the
sealing agent with the nonaqueous activating fluid to form a
sealant composition.
[0007] WO 2008/009957 discloses a method of forming a barrier for a
fluid in a subterranean area penetrated by a wellbore, comprising
depositing of particulate material in a fracture, wherein the
particulate material comprises at least some particles made from
material that swells when contacted with said fluid.
[0008] US 2008/0017376 discloses a method of reducing fluid loss in
a subterranean formation comprising placing a lost circulation
composition comprising a base fluid and a swellable elastomer and
allowing the swellable elastomer to swell upon contact with a
fluid.
[0009] US 2006/234871 A1 discloses a sealant composition for
servicing a wellbore comprising at least one gel system, a leak off
prevention material and water.
[0010] U.S. Pat. No. 4,649,998 discloses a method of treating a
subterranean, unconsolidated sand and petroleum containing
formation penetrated by at least one well, which is in fluid
communication with at least a portion of the unconsolidated sand
containing subterranean formation, in order to form a flexible,
permeable barrier around the well which restrains the movement of
sand particles into the well while permitting the passage of
formation fluids including petroleum there through.
[0011] Various attempts have been made to reduce fluid loss in a
subterranean formation. However, there is still a need in the art
for a composition efficient for sealing leaks or fractures in a
wall or formation such as a well bore, drain or pipeline. Moreover
there is a need for a composition providing an efficient and
cost-effective control or prevention of leakage from e.g. a
subterranean formation and providing a fracture plug capable of
withstanding the harsh conditions experienced in the oil drilling
industry but which does not leak into the pores of a subterranean
formation. Moreover, there is a need in the art for a method
whereby it is possible to obtain a plug flow of the treatment fluid
to the desired place in a fracture-containing system.
OBJECT OF THE INVENTION
[0012] It is an object of embodiments of the invention to provide a
composition allowing an efficient sealing of leaks or fractures in
a well bore, drain or pipeline. More particularly, it is an object
of embodiments of the invention to provide an efficient and
homogenous sweep of an oil well and thereby a more efficient
utilization thereof. Even more particularly it is an object of
embodiments of the invention to provide a method providing a
chemically created barrier in a fracture-containing system to
obtain an efficient blocking of a fracture.
SUMMARY OF THE INVENTION
[0013] It has been found by the present inventors that by providing
an elastomeric material comprising at least one polymer capable of
crosslinking into an elastomer together with at least one
crosslinking agent in a base fluid and allowing the elastomeric
material to crosslink with itself and with the crosslinking agent
an efficient barrier is created.
[0014] So, in a first aspect the present invention relates to a
method of providing a barrier in a fracture-containing system,
comprising: [0015] i) Providing a treatment fluid comprising:
[0016] a) a base fluid; [0017] b) an elastomeric material, wherein
said elastomeric material comprises at least one polymer capable of
crosslinking into an elastomer, and [0018] c) at least one
crosslinking agent; [0019] ii) Placing the treatment fluid in a
fracture-containing system; [0020] iii) Allowing the elastomeric
material to crosslink with itself and with the crosslinking agent
to form a barrier in said fracture-containing system; wherein the
elastomeric material and/or the crosslinking agent are of neutral
buoyancy with regard to the base fluid.
[0021] In a second aspect the present invention relates to a
treatment fluid comprising: [0022] a) a base fluid; [0023] b) an
elastomeric material, wherein said elastomeric material comprises
at least one polymer capable of crosslinking into an elastomer, and
[0024] c) least one crosslinking agent; wherein the elastomeric
material and/or the crosslinking agent are of neutral buoyancy with
regard to the base fluid.
[0025] In a third aspect the present invention relates to a use of
a treatment fluid according to the invention for fracture
blocking.
DETAILED DISCLOSURE OF THE INVENTION
Definitions
[0026] In the present context the term "elastomer" refers to
compositions of matter that have a glass transition temperature,
T.sub.g, at which there is an increase in the thermal expansion
coefficient, and includes both amorphous polymer elastomers and
thermoplastic elastomer (thermoplastics). An elastomer exhibits an
elasticity deriving from the ability of the polymer chains of the
elastomer to reconfigure themselves to distribute an applied
stress.
[0027] The term "elastomeric material" refers in the present
context to a material, which may, in addition to elastomer, include
fillers and additives. Non-limiting examples of fillers are e.g.
reinforcing fillers such as silica and carbon black as well as
fillers with color enhancement such as titanium dioxide.
[0028] The terms "crosslinking agent" and "crosslinker" are used
interchangeably and in the present context means a material capable
of forming bonds between one polymer chain and another.
[0029] The term "thermoplastic material" in the present context
means a polymer that turns to a liquid when heated and solidifies
to a rigid state when cooled sufficiently.
[0030] The term "barrier in a fracture-containing system" in the
present context means a physical obstruction of the passage of
material through said fracture so that at most 5% of the original
area is available for passage, preferably at most 3%, more
preferably at most 1%, even more preferably less than 0.1% of the
original area.
[0031] The term "particle size" of an elastomeric material or a
crosslinking agent, respectively, means the average diameter of the
particles in question without any coating or outer layer.
[0032] The term "accelerator" in the present context refers to a
material that accelerates the breakdown of the first and/or second
thermoplastic material layer.
[0033] The term "thickness" of a layer, such as the thickness of
the first and/or second thermoplastic material layer, refers to the
average thickness thereof.
[0034] The term "activation" in the present context refers to the
action of removal of the layer of the first and/or second
thermoplastic material in order to expose the interior of the
particles in question for reaction, such as crosslinking.
[0035] The term "curing" in the present context refers to the
process of cross-linking of polymer chains. The term "partial
curing" in the present context refers to a cross-linking process
wherein only a proportion of the reactive groups of the polymer
chains of the elastomeric material available for reaction are
crosslinked.
[0036] The term "neutral buoyancy" in the present context means
that the density of the particles of the elastomeric material
and/or the crosslinking agent is the same as the density of the
base fluid so that said particles will float in the base fluid and
thus will neither sink nor rise. That the density of the particles
of the elastomeric material and/or the crosslinking agent is the
same as the density of the base fluid means that the numerical
values of the densities in g/ml is the same .+-.5%, such as .+-.3%,
and preferably deviates no more than 1% from each other.
Specific Embodiments of the Invention
[0037] The elastomeric material and/or the crosslinking agent are
of neutral buoyancy with regard to the base fluid or in other words
are present under isopycnic conditions. This secures that the
elastomeric material and/or the crosslinking agent will be
transported to the desired place of action. The presence of
isopycnic conditions provides for plug flow of the treatment fluid
and thereby a controlled and specific delivery to the intended
place of action without loss or premature leakage of treatment
fluid. The density of the elastomeric material and/or the
crosslinking agent may be controlled, if desired, via addition of
e.g. fillers, such as silica.
[0038] In an embodiment of the invention at least one of the
elastomeric material or the crosslinking agent is present in the
form of particles. Thereby a tailoring of the treatment fluid to
the fracture to be sealed is more readily obtained.
[0039] In an embodiment of the invention the elastomeric material
is present in the form of particles of elastomeric material.
[0040] In an embodiment of the invention the elastomeric material
comprises one or more components selected from the group consisting
of natural rubber, acrylate butadiene rubbers, polyacrylate
rubbers, isoprene rubbers, chloroprene rubbers, butyl rubbers,
brominated or chlorinated butyl rubbers, chlorinated polyethylene,
neoprene rubbers, styrene butadiene copolymer rubbers, sulphonated
polyethylene, ethylene oxide copolymers, ethylene-propylene
rubbers, ethylene-propylene-diene terpolymer rubbers, ethylene
vinyl acetate copolymers, fluorosilicone rubber, silicone rubbers,
poly 2,2,1-bicyclo heptane, alkylstyrene, crosslinked substituted
vinyl acrylate copolymers and diatomaceous earth, nitrile rubbers,
hydrogenated nitrile rubbers, fluoro rubbers, perfluoro rubbers,
tetrafluoroethylene/propylene, starch-polyacrylate acid graft
copolymers, polyvinyl alcohol-cyclic acid anhydride graft
copolymers, isobutylene maleic anhydride, acrylic acid type
polymers, vinylacetate-acrylate copolymer, polyethylene oxide
polymers, carboxymethyl cellulose type polymers,
starch-polyacrylonitrile graft copolymers, polymethacrylate,
polyacrylamide, and acrylic polymers.
[0041] In a particular embodiment of the invention the elastomeric
material comprises one or more components selected from the group
consisting of natural rubber, acrylate butadiene rubbers,
polyacrylate rubbers, isoprene rubbers, chloroprene rubbers, butyl
rubbers, fluorosilicone rubber, silicone rubbers, and acrylic
polymers, more preferably silicone rubbers such as RTV (Room
Temperature Vulcanizing) silicone rubbers, HTV (High Temperature
Vulcanizing) silicone rubbers or LSR (Liquid Silicone Rubbers). A
preferred silicone rubber is an RTV silicone such as
silica-reinforced PDMS (PolyDiMethylSiloxane). An example of a
commercially available silica-reinforced PDMS is Sylgard.TM. 184
from Dow Corning or Elastosil RT625 from Wacker Chemie AG.
[0042] In contrast to traditional hydrocarbon based polymers
silicone rubbers lack the C--C bond in their polymeric backbone
structure which makes them less susceptible to ozone, UV, heat,
chemical degradation, and other ageing factors than hydrocarbon
based polymers. Other advantages of silicone rubbers are generally
good resistance towards water, acids, aliphatic hydrocarbons, and
oils. Furthermore silicone rubbers generally possess low gas
permeability, large spreadability in the prereacted state, a very
wide temperature range of operation (-150 to 550.degree. C.) and a
density similar to brine which makes delivery possible without any
phase separation due to differences in densities.
[0043] In an embodiment of the invention the particle size of the
particles of the elastomeric material is in the range of 0.1-1000
.mu.m, preferably in the range 1-500 .mu.m, more preferably in the
range 5-300 .mu.m, such as 10-200 .mu.m, more preferably 10-100
.mu.m.
[0044] The particle size is chosen to allow an efficient plugging
of a fracture while not allowing the particles to seep into the
pores of a subterranean formation.
[0045] A typical cross section of a subterranean fracture is in the
range 0.5-5 mm, while the diameter of the pores of a subterranean
formation is typically in the range 1-10 .mu.m. Thus particle sizes
in the above range are able to create an efficient fracture plug
while being of a size larger than the typical pore sizes.
[0046] In an embodiment of the invention the elastomeric material
is partially cured before mixing of said material with the
crosslinking agent and the base fluid to form the treatment
fluid.
[0047] In an embodiment of the invention said partial curing is
obtained by reaction with at least one curing agent in an amount in
the range 10-70% by mole, such as 20-60% by mole, such as 25-50% by
mole of the stoichiometric amount of the reactive groups of the
elastomeric material.
[0048] In an embodiment of the invention said partial curing is
obtained by mixing the elastomer and the curing agent to obtain an
emulsion using a mixer speed depending on the desired final
particle size. Thus a speed in the range 500-2000 rpm may be used,
such as 700-1500, such as 800-1200, such as about 1000 rpm.
[0049] In an embodiment of the invention said curing agent is a
crosslinking agent as disclosed further below.
[0050] In an embodiment of the invention said crosslinking agent is
a hydride-vinyl crosslinking agent as disclosed further below.
[0051] Thus the elastomeric material may be partially cured by
adding a curing agent, such as a crosslinker, in deficit compared
to the molar amount of elastomeric material, to an elastomeric
material. In an embodiment of the invention the mixture obtained
may be added to an aqueous phase formed by dissolving a surfactant,
or a mixture of surfactants, in water with stirring. The surfactant
may be any surfactant suitable for the treatment fluid in question
and is selected from the group consisting of anionic, cationic,
non-ionic or zwitter-ionic surfactants. Non-limiting examples of
suitable surfactants include an anionic surfactant such as sodium
dodecyl sulphate (SDS), a cationic surfactant such as polyvinyl
alcohol (PVA), a nonionic surfactant such as a polyoxyethylene
glycol (PEG) alkyl ether, a polyoxypropylene glycol (PPG) alkyl
ether or a polyoxyethylene-polyoxypropylene glycol (PEG-PPG) alkyl
ether, and a zwitterionic surfactant such as Lecithin. A
particularly preferred surfactant is selected from the group
consisting of SDS, PVA and a polyoxyethylene-polyoxypropylene
glycol (PEG-PPG) alkyl ether or a mixture thereof, such as a
mixture of SDS and PVA. A polyoxyethylene-polyoxypropylene glycol
(PEG-PPG) alkyl ether is commercially available under the trade
name Pluronic, such as Pluronic.TM. F-108.
[0052] In an embodiment of the invention the partial curing may be
obtained by means of irradiation. Irradiation may be obtained by
heating, such as heating to a temperature in the range
50-100.degree. C., such as in the range 60-80.degree. C.
[0053] In an embodiment the partial curing may be obtained by means
of irradiation by means of electromagnetic or particle radiation.
Secondary gamma radiation may take place by means of supplying an
electric current. Any other source of radiation that may be
switched on electrically may be of operational advantage.
[0054] In an embodiment of the invention the partially cured
elastomeric material is present in the form of particles and may be
used without any protective layer of a first thermoplastic
material.
[0055] In another embodiment of the invention the particles of
partially cured elastomeric material are provided with a protective
layer of a first thermoplastic material. This may be obtained by
adding partially cured particles to an aqueous solution of a
surfactant, such as any one of the surfactants mentioned above,
such as polyvinyl alcohol (PVA), sodium dodecyl sulphate (SDS) or a
polyoxyethylene-polyoxypropylene glycol (PEG-PPG) alkyl ether or a
mixture thereof, and adding said solution to an oil phase of a
first thermoplastic material, such as PMMA, in an organic solvent
to form an oil-in-water emulsion. Non-limiting examples of suitable
solvents include acetone, dichloromethane (DCM), tetrahydrofuran
(THF), and dimethylformamide (DMF). Coated particles of elastomeric
material may e.g. be obtained by rotary evaporation of solvent.
[0056] In another embodiment of the invention the particles of
elastomeric material are provided with a protective layer of a
first thermoplastic material without any preceding partial curing
of the elastomeric particles. In this embodiment an elastomeric
material and a first elastomeric material, such as PMMA, may be
dissolved in an organic solvent, such as dichloromethane,
tetrahydrofuran, or dimethylformamide, to form an oil phase. An
aqueous solution of a surfactant, such as polyvinyl alcohol, may be
prepared by stirring, and the oil phase may be added over a period
of time, such as 30-120 min, in particular 45-90 min, such as 60-80
min, to the aqueous solution to form an oil-in-water emulsion.
Coated particles of elastomeric material may be obtained by rotary
evaporation of solvent.
[0057] By providing a protective outer layer or coating on the
particles of the elastomeric material handling thereof is
simplified and the reactivity of the elastomer system is hindered
until the protective outer layer has been fully or partly removed.
Activation of the particles, i.e. removal of the protective layer,
may take place by the action of heat, irradiation or solvent
dissolution as disclosed in more detail below.
[0058] In an embodiment of the invention the crosslinking agent is
selected from the group consisting of carboxyl-to-amine
crosslinking, amine-reactive crosslinking, sulfhydryl-reactive
crosslinking, carbonyl-reactive crosslinking, photoreactive
crosslinking, hydroxyl-reactive crosslinking, and hydride-vinyl
crosslinking agents.
[0059] The following table I exemplifies some commonly used
crosslinking agents:
TABLE-US-00001 TABLE I Crosslinking functionality Crosslinking
agents Carboxyl-to-amine Carbodiimides such as crosslinking
1-Ethyl-3-[3- dimethylaminopropyl]carbodiimide hydrochloride (EDC),
dicyclohexylcarbodiimide (DCC), N-hydroxysuccinimide (NHS) and
N-hydroxysulfosuccinimide (Sulfo-NHS) amine-reactive
N-Hydroxysuccinimide crosslinking Esters (NHS Esters) Imidoesters
such as dimethyl adipimidate (DMA) dimethyl pimelimidate (DMP)
dimethyl suberimidate (DMS) sulfhydryl-reactive Maleimides,
haloacetyls, disulfides crosslinking carbonyl-reactive Hydrazides
such as sulfonylhydrazides crosslinking photoreactive Aryl azides
(also called crosslinking phenylazides), cinnamic acids and other
photoactive polymers hydroxyl-reactive Branched Silanol containing
crosslinking PolyDimethylsiloxanes, Ethylsilicate,
ethyltriacetoxysilane, tetra-n-propoxysilane Hydride-vinyl
Crosslinkers containing 3 or more vinyl crosslinking groups such as
Vinylmethylsiloxane- Dimethylsiloxane Copolymers, vinyl resins or
vinyl gums. Crosslinkers containing 3 or more hydride groups such
as MethylHydrosiloxane- Dimethylsiloxane Copolymers,
polyMethylHydrosiloxanes and Hydride Q Resins
[0060] In an embodiment of the invention the crosslinking agent is
present in the form of particles.
[0061] In an embodiment of the invention the particle size of the
particles of the crosslinking agent is in the range of 0.1-1000
.mu.m, preferably in the range 1-500 .mu.m, more preferably in the
range 5-300 .mu.m, such as 10-100 .mu.m.
[0062] In an embodiment of the invention the particles of the
crosslinking agent comprise an outer layer of a second
thermoplastic material. Preparation of particles of crosslinking
agent comprising an outer layer of a thermoplastic material may
take place by dissolving a crosslinking agent and a thermoplastic
material in a conventional organic solvent, such as
dichloromethane, to form an oil phase which is added to an aqueous
phase formed by dissolving a surfactant, such as polyvinyl alcohol,
in water. Further non-limiting examples of suitable surfactants
include an anionic surfactant such as sodium dodecyl sulphate
(SDS), a nonionic surfactant such as a polyoxyethylene glycol (PEG)
alkyl ether, a polyoxypropylene glycol (PPG) alkyl ether or a
polyoxyethylene-polyoxypropylene glycol (PEG-PPG) alkyl ether, and
a zwitterionic surfactant such as Lecithin. A particularly
preferred surfactant is selected from the group consisting of SDS,
PVA and a polyoxyethylene-polyoxypropylene glycol (PEG-PPG) alkyl
ether or a mixture thereof, such as a mixture of SDS and PVA. An
oil-in-water-emulsion may be formed by adding the oil phase with
stirring to the aqueous phase. Coated particles of crosslinking
agent may be obtained by rotary evaporation of solvent.
[0063] In an embodiment of the invention the elastomeric material
is a silicone rubber and the crosslinking agent is a hydride-vinyl
crosslinking agent.
[0064] In an embodiment of the invention the hydride-vinyl
crosslinking agent is selected from the group consisting of
methylhydrosiloxane-dimethylsiloxane copolymers,
polymethylhydrosiloxanes, and vinylmethylsiloxane-dimethylsiloxane
copolymers.
[0065] In an embodiment of the invention the elastomeric material
is a Polydimethylsiloxane (PDMS) rubber and the crosslinking agent
is a methylhydrosiloxane-dimethylsiloxane copolymer.
[0066] Poly(dimethyl siloxane) (PDMS) is an inert elastomer that
have unique properties such as elastic behaviour and resistance to
high temperatures, chemical attack and light degradation.
Additionally, the reactive groups on the siloxane surface groups
can be used as convenient chemical "handles" for particle
functionalization. Moreover, PDMS presents high permeability to
various solvents and gases allowing PDMS particles to promptly
absorb selected agents from the local environment.
[0067] In an embodiment of the invention partly cured PDMS
microspheres with reactive handles are subjected to a
hydrosilylation addition reaction to prepare cross-linked PDMS
elastomers where linear PDMS polymers with two vinyl terminated
groups react with a multifunctional cross-linker leading to a
three-dimensional cross-linked network.
[0068] In an embodiment of the invention the elastomeric material
is a silicone rubber and the crosslinking agent is an organic
peroxide selected from the group consisting of
Di(2,4-dichlorobenzoyl) peroxide (Perkadox PD), Di(4-methylbenzoyl)
peroxide (Perkadox PM), Dibenzoyl peroxide (Perkadox L) and
tert-Butyl peroxybenzoate (Trigonox C).
[0069] In an embodiment of the invention the first and second
thermoplastic material, independently of each other, is selected
from the group consisting of polyalkyl methacrylate, such as
polymethyl methacrylate (PMMA), fluorinated polyalkyl methacrylate,
such as heptafluorbutyl methacrylate (HFBMA), copolymers of
polyalkyl methacrylate and fluorinated polyalkyl methacrylate, such
as copolymers of polymethyl methacrylate (PMMA) and heptafluorbutyl
methacrylate (HFBMA), polyester, polyurethane, polyvinyl acetate,
polyvinyl chloride (PVC), poly(acrylonitrile),
poly(tetrahydrofuran) (PTHF), styrene-acrylonitrile, polyethylene
terephthalate, polycyclohexylene dimethylene terephthalate,
polyhydroxyalkanoates, chlorinated polyethylene, polyimide,
polylactic acid, polyphenylene oxide, polyphthalamide, and
polypropylene, preferably polymethyl methacrylate (PMMA),
preferably wherein the first and second thermoplastic materials are
both PMMA.
[0070] The aim of the first and the second thermoplastic material,
respectively, if present, is to protect the particles of the
crosslinking agent and the elastomeric material, respectively,
until the point of use, and at that point in time to be able to be
removed quickly and efficiently to activate the particles by
exposing the interior of said particles, i.e. the particles without
a layer of thermoplastic material. A preferred thermoplastic
material should have a glass transition temperature in the range
80-110.degree. C. which is close to the typical operation
temperature of an oil well.
[0071] Encapsulating or coating of particles may be obtained by
several techniques, which can be broadly divided into two major
groups: Physical and chemical methods. Non-limiting examples of
physical methods include air suspension, coacervation phase
separation, centrifugal extrusion, spin coating, spray drying and
pan coating, whereas solvent evaporation and polymerization are
non-limiting examples of methodologies well recognized as chemical
processes for coating/encapsulating particles.
[0072] In an embodiment of the invention encapsulation is obtained
by the solvent evaporation technique, where a coating polymer
(PMMA) may be dissolved in a volatile organic solvent that is
immiscible with water, such as dichloromethane (DCM), or in a
water-soluble solvents, such as THF and/or acetone, whereby the
coating polymer (PMMA) will be in the same phase as the cured PDMS
particles. In an embodiment of the invention a mixture of solvents
may be used, such as acetone and THF.
[0073] In another embodiment of the invention encapsulation is
obtained by spin coating.
[0074] In an embodiment of the invention the first and second
thermoplastic materials are both PMMA. PMMA has a glass transition
temperature of 90-100.degree. C. which is close to the operation
temperature of an oil well. Thereby it is possible, optionally with
further addition of energy, to melt the PMMA layer and subject it
to shear forces which will remove the protective layer of
thermoplastic material. PMMA is also degradable by gamma-radiation
which will cause "scissioning", i.e. cutting of the polymer chains
of PMMA. A further activation method is solvent dissolution,
wherein the particles are flushed by a solvent which gradually
removes the polymer chains of PMMA. Thus several activation
mechanisms may be used, either separately or in combination.
[0075] In an embodiment of the invention a minor amount, such as
from 1-5% by weight, such as about 3% by weight, of an oil, such as
silicone oil, may be added to the thermoplastic material in order
to assist the thermoplastic material in the coating of the
elastomeric material. Without being bound to any theory it is
believed that silicone oil may assist e.g.
[0076] PMMA in the coating of particles of an elastomeric material,
such as PDMS microspheres, due to the high interaction parameter
between silicone oil and the elastomeric material, and its
non-reactive property.
[0077] Another advantage of the use of PMMA as protective layer is
that PMMA is water resistant and will not swell at the typical
temperatures of use.
[0078] In an embodiment of the invention the thickness of the layer
of the first thermoplastic material is in the range of 0.01-20
.mu.m, preferably in the range of 0.1-5 .mu.m.
[0079] In an embodiment of the invention the thickness of the layer
of the second thermoplastic material is in the range of 0.01-20
.mu.m, preferably in the range of 0.1-5 .mu.m.
[0080] The thickness of the outer protective layer of the first
and/or second thermoplastic layer is a balance between on the one
hand the wish for efficiency of the system, as a consequence of
which the thickness needs to be low such that the activation
initiates a fast and efficient removal of the protective layer, and
on the other hand the desire for a complete coating of the
individual particles. Thus if the thickness of the protective outer
layer is too small the particles may very well have unprotected
spots which can react prematurely and cause irreversible
agglomeration of the particles in the treatment fluid.
[0081] In an embodiment of the invention the base fluid is a gas,
an aqueous fluid or an oleaginous fluid, preferably water or a
hydrocarbon fluid, more preferably water. In the case of wellbore
drilling a readily available base fluid material is water in the
form of brine.
[0082] Non-limiting examples of a gas to be used as base fluid
according to the invention include air, methane or natural gas.
[0083] In an embodiment of the invention the treatment fluid
further comprises one or more additives conventionally used in the
art, such as fillers, flow or viscosity modifiers, anti-foaming
agents, suspending agents, dispersing agents, buffers, and
surfactants.
[0084] In an embodiment of the invention the treatment fluid
comprises a filler in the form of e.g. sand, grit or the like which
may increase the strength of the treatment fluid.
[0085] In an embodiment of the invention the treatment fluid
comprises one or more surfactants. Surfactants are known in the art
and non-limiting examples thereof include sodium dodecyl sulphate
(SDS), polyvinyl alcohol (PVA) and surfactants of the Pluronic.TM.
series, such as Pluronic.TM.F-108.
[0086] In an embodiment of the invention the treatment fluid
comprises a viscosity modifier as known in the art. Commercially
available viscosity modifiers include viscosifiers from MI SWACO,
such as viscosifiers marketed under the tradenames DUROGEL.TM. and
SAFE-VIS.TM..
[0087] In an embodiment of the invention the accelerator is a
capsule comprising a core and a coating. In an embodiment of the
invention the core is made of a material suitable as solvent for
the first and/or second thermoplastic material. In an embodiment of
the invention the coating is made of a copolymer of the first
and/or second thermoplastic material and a polymer compatible with
the core material of the capsules.
[0088] In an embodiment of the invention the accelerator is an
organic solvent. Non-limiting examples include hydrocarbons such as
hexane and heptane and silicone oils, preferably low molecular
weight silicone oils such as Dow Corning.RTM. OS10, OS20 or
OS30.
[0089] In an embodiment of the invention the accelerator comprises
a catalyst in an organic solvent, such as the solvents mentioned
above. Non-limiting examples of catalysts include platinum or tin
or complexes thereof.
[0090] In an embodiment of the invention the accelerator is an
inorganic salt, such as CaSO.sub.4 or MgSO.sub.4, which is
encapsulated by a thermoplastic material such as the first and/or
second thermoplastic material as defined above. When the
encapsulation has been broken calcium and magnesium sulphate will
upon contact with water react exothermically to release heat. In
the case of particles of the elastomeric material encapsulated by a
first thermoplastic material and/or particles of a crosslinking
agent encapsulated by a second thermoplastic material acceleration
of the degradation of the first and/or second thermoplastic
material may thereby be obtained.
[0091] In an embodiment of the invention the particles of the
elastomeric material are present in an amount in the range of
10-75% by volume of the treatment fluid, preferably in the range
25-50% by volume, such as in the range 30-40% by volume. Hereby a
pumpeable solution is generally obtained such that the particles
can pass the pump without destruction as well as be delivered at
the desired place of use.
[0092] In an embodiment of the invention the particles of the
crosslinking agent are present in an amount in the range of 0.1-50%
by volume of the treatment fluid, preferably in the range 0.5-20%
by volume, such as 2-10% by volume. Hereby a pumpeable solution is
obtained such that the particles can pass the pump without
destruction as well as be delivered in the right place.
[0093] In an embodiment of the invention in step iii) the
elastomeric material is allowed to crosslink with the addition of
energy. Energy input is believed to be necessary at least for an
initiation of the crosslinking reaction of the elastomeric
material.
[0094] In an embodiment of the invention said energy is provided in
the form of irradiation.
[0095] Irradiation may be provided by means of thermal irradiation.
Thermal irradiation may penetrate relatively deeply into a
formation but may be a relatively slow form of energy input. Thus
heat may be supplied or may be present as thermal energy from the
ground.
[0096] In an embodiment of the invention energy input may be
provided by means of electromagnetic or particle radiation. The
effect of activation by means of particle radiation may be applied
relatively fast compared to for instance the effect of activation
by means of thermal radiation. Radiation may be supplied in the
form of y radiation. Activation may thus be performed by means of
supplying an electric current.
[0097] In an embodiment of the invention energy input may be
provided by a combination of e.g. thermal irradiation and
electromagnetic or particle radiation.
[0098] The order of energy required is generally believed to be in
the range of 0.1-100 J/g of active silicone, (i.e. the reactive
part of the total elastomer mixture excluding any fillers and
additives).
[0099] In an embodiment of the invention the treatment fluid is
prepared by mixing elastomeric material, crosslinking agent and a
base fluid and heating to an elevated temperature, such as in the
range 60-100.degree. C., preferably in the range 70-80.degree. C.
in order to obtain crosslinking of the elastomeric material to
obtain a plug thereof.
[0100] In an embodiment of the invention a first proportion of
treatment fluid comprises particles of the elastomeric material of
a particle size in the range 500-1000 .mu.m, and a second
proportion of treatment fluid comprises particles of the
elastomeric material of a particle size in the range 10-100
.mu.m.
[0101] In an embodiment of the invention said first and said second
proportion of particles of the elastomeric material are provided
simultaneously or consecutively to the treatment fluid. By having
particles of different particle sizes a tailoring of the fracture
to be blocked is more efficiently obtained. Thus by providing a
first proportion of treatment fluid comprising particles of a
larger particle size and subsequently a second proportion of
treatment fluid comprising particles of a smaller particle size,
the latter may fill out any interstices formed between the larger
particles in order to obtain an efficient blocking of a
fracture.
[0102] In another embodiment of the invention a first proportion of
treatment fluid comprises particles of the elastomeric material of
a particle size in the range 10-100 .mu.m, and a second proportion
of treatment fluid comprises particles of the elastomeric material
of a particle size in the range 500-1000 .mu.m. Thus by providing a
first proportion of treatment fluid comprising particles of a
smaller particle size and subsequently a second proportion of
treatment fluid comprising particles of a larger particle size the
smaller particles may first fill out small interstices at the end
of a fracture and larger particles may subsequently fill out the
larger part of a fracture.
[0103] In an embodiment of the invention use of the treatment fluid
according to the invention is for fracture blocking in an oil
drilling well.
[0104] In an embodiment of the invention use of the treatment fluid
according to the invention is for fracture blocking in sewer
drains.
[0105] The method according to the invention may be performed by
means of a sealing device for sealing fractures or leaks in a wall
or formation surrounding a tube-shaped channel, such as a drain,
pipeline or well bore, the sealing device including an elongated
body having a longitudinal direction and being adapted to be
introduced into the tube-shaped channel, the elongated body
including a sealing fluid placement section arranged between a
first and a second annular flow barrier adapted to extend from a
circumference of the elongated body to the wall or formation
surrounding the tube-shaped channel, and the sealing fluid
placement section including a sealing fluid outlet port. The
sealing device is disclosed in more detail in the Applicants'
copending patent application of same date entitled "Sealing device
and method for sealing fractures or leaks in wall or formation
surrounding tube-shaped channel", EP No. 12194965.5.
Example 1
[0106] 1.1. Preparation of Silicone Microspheres with Partial
Pre-Curing
[0107] Sylgard.TM. 184 silicone elastomer which is provided from
Dow Corning as a two-parts kit of a polydimethylsiloxane (PDMS)
elastomer and a "curing agent" comprising a crosslinker were mixed
at a ratio of 20:1 at 1000 rpm for 2 mins in order to form a
mixture S resulting in an elastomer with excessive amounts of vinyl
groups as the "curing agent" was added in deficit (the recommended
ratio of Sylgaard.TM. 184 is 10:1 PDMS:curing agent). The bubbles
formed were removed from the mixture S with a vacuum pump for 10
mins. Thereafter 2 g of mixture S was added to 60 g aqueous
solution containing 0.06 g of the surfactant Pluronic.TM. F-108
from BASF, a copolymer consisting of PEG-PPG-PEG, average Mn
14,600). The mixture was ultrasonicated for 5 mins to disperse the
mixture S in the aqueous solution and cured at 60.degree. C. for 4
h.
[0108] The yield for this process was about 66% of particles with a
mean diameter of approximately 1 micrometer.
[0109] 1.2 Preparation of Coated Silicone Microspheres with Partial
Precuring
[0110] 0.272 g of hard silicone microspheres according to example
1.1 were added to 25 ml of 1% polyvinyl alcohol (PVA) solution. The
aqueous solution was sonicated for 15 min and then let to cool to
room temperature. Afterwards, 25 ml of a 1.3% PMMA solution in
acetone was added to form an oil-in-water emulsion. Agitation was
maintained for 2 h and then the solution was rotary evaporated for
20 min, with the temperature being ramped from 20 to 65.degree. C.
over this period of time. Later, the vacuum was switched off and
the solution was kept at 65.degree. C. for further 40 min. The
rotary speed was 260 rpm. The dispersion of coated microspheres was
cleaned with distilled water and filtered.
[0111] 1.3 Preparation of Cured PDMS Microspheres
[0112] First PDMS microspheres were prepared in a separate step. In
order to obtain small partly cured PDMS microspheres with a large
surface area with reactive handles the initial speed of mixing was
assessed. Several PDMS mixtures with different viscosities were
prepared by mixing the prepolymer base elastomer and the curing
agent in several weight ratios (10:1, 20:1 and 25:1). Then, the
resulting mixtures were mechanically stirred and subjected to
vacuum for 15 min and finally transferred to a syringe. 1 ml PDMS
mixture was poured into 250 ml of an aqueous solution that
contained anionic SDS (3% w/w) and polymeric (1% w/w) PVA
surfactants. The emulsification process was basically divided into
a three-step procedure. Firstly, the dispersion was mechanically
stirred intensively for approximately 2 min at varying initial
speeds (2000, 1200, 800 and 500 rpm, respectively). Secondly, the
speed for all procedures was reduced to 500 rpm for 10 min.
Finally, the rotation speed was reduced further to 110 rpm and the
temperature was increased up to 85.degree. C. for 2 hours for
faster curing of the PDMS microspheres. The cured PDMS microspheres
were filtered and washed with distilled water.
[0113] The result of the above testing is shown in Table II
below.
TABLE-US-00002 TABLE II Average particle size of cured PDMS
microspheres compared to the weight ratio and rotation speed
Particle size (.mu.m) Ratio 10:1* Initial (recommended by the speed
manufacturer) Ratio 20:1* Ratio 25:1* Entry (rpm) D(0.1)** D(0.5)
D(0.9) D(0.1) D(0.5) D(0.9) D(0.1) D(0.5) D(0.9) 1 2000 7 63 172 33
104 292 16 89 190 2 1200 38 130 394 46 144 510 15 83 203 3 800 50
133 516 34 100 252 33 100 313 4 500 54 149 732 37 98 227 46 103 387
*Ratio between the silicone elastomer base and the silicone
elastomer curing agent. **D(0.1), D(0.5) and D(0.9) are standard
"percentile" readings from the analysis. This means D(0.1) is the
size of particle for which 10% of the sample is below this size and
so forth.
[0114] The results in Table II show that the average particle size
generally increases when decreasing the initial speed applied by
the mechanical stirrer in the emulsification process. This means
that the average particle size is dependent on the initial speed
applied which provides the initial shearing force for the break-up
of the spheres.
[0115] 1.4 Preparation of PMMA Coated Cured PDMS Microspheres
[0116] 0.3 g of cured PDMS microspheres (20:1) was added to 25 ml
of 1% (w/w) PVA solution. The aqueous solution was sonicated for 10
min to provide as little aggregation as possible since the spheres
physically adhere together. Following the sonication the mixture
was allowed to cool down to room temperature before adding 25 ml of
1.3% (w/w) PMMA solution in DCM. Agitation was maintained for 2 h.
Afterwards, the solution was rotary evaporated for 20 min, with the
temperature being ramped from 20 to 65.degree. C. during this time,
after which the vacuum was switched off and the solution was kept
at 65.degree. C. for further 45 min. The rotary speed was set to
260 rpm. PMMA coated cured PDMS microspheres were washed with
distilled water and finally the microspheres were filtered. The
same procedure was repeated but replacing DCM with THF and acetone,
respectively. Hot plate heating with magnetic stirring was also
used instead of the rotavapor to study if the agglomeration of
microspheres upon solvent removal could be avoided.
[0117] 1.5 Preparation of (Partly) Cured PDMS Microspheres
[0118] 8 g Sylgard 184 elastomer (Batch A) and the respective
amount of curing agent were mixed in a polystyrene cup in a weight
ratio of 10:1 or 20:1 at 1000 rpm for 2 min to yield a mixture S. 7
g of mixture S was then poured into a conical flask with 200 g of
aqueous surfactant solution (SDS, PVA or a mixture thereof). A 2.0
cm diameter impeller with two inclined blades was used to stir for
2 min at 2000 rpm to produce the emulsion. After the emulsion was
formed, the system was inserted into an oven at 80.degree. C. for 2
h to cure the PDMS microspheres. Then the system was filtered by
use of a vacuum filter and washed with deionised water several
times to remove the residual surfactant. The PDMS microspheres were
then dried in an oven at 80.degree. C. for 2 h.
[0119] 1.6 Preparation of Coated PDMS Microspheres
[0120] 0.4 g PDMS microspheres (in a weight ratio of elastomer to
curing agent of 20:1) prepared as in 1.5 above was introduced to a
polystyrene watch glass (r=2.2 cm). PMMA was dissolved in DMF to
yield a solution of 1%, 3%, or 5% (wt) DMF, and 3% (wt) silicone
oil was also dispersed into the solution. The polystyrene glass
watch was covered with a lid and subjected to a spin coater. Spin
coating was performed at 5000 rpm for 1 min with an acceleration of
1000 rpm/s from 0 to 5000 rpm. Then the polystyrene glass watch was
inserted into an oven at 80.degree. C. to remove the residual
DMF.
[0121] The result of the above was tested by thermogravimetric
analysis (TGA) of PDMS microspheres coated with silicone oil and
different concentrations of PMMA by spin coating, cf. Table III
below.
TABLE-US-00003 TABLE III PMMA Silicone Content of concentration oil
in Coating Char PDMS in Sample in solution solution speed yield at
microspheres ID (%) (%) (rpm) 430.degree. C. (%) PMMA -- -- -- 0 --
Silicone -- -- -- 15.1 -- oil PDMS 96.1 PDMS- 1 3 5000 94.9 98
P1S3D PDMS- 3 3 5000 93.8 97 P3S3D PDMS- 5 3 5000 91.5 95 P5S3D
[0122] At a temperature of 430.degree. C., PMMA degrades completely
while silicone degrades to a degree of 85%, and the content of
PMMA, silicone oil and PDMS can thus be calculated by measuring the
char yield (wt %) at this temperature.
Example 2
[0123] Preparation of Coated Silicone Microspheres without
Pre-Curing
[0124] PMMA (1 g) was dissolved in dichloromethane (DCM) (75 ml)
and then 2 g of the Sylgard.TM. 184 polydimethylsiloxane elastomer
from Dow Corning was added. An aqueous surfactant solution (77.5 g
of 1% PVA) was prepared and added to a 250 ml conical flask. The
aqueous phase was mechanically stirred at 2000 rpm for 2 min, and
the oil phase was added over 60 s to form an oil-in-water emulsion.
The agitation was kept for 1 h at 1000-750 rpm before pouring the
emulsion into a further 120 ml of aqueous surfactant solution (1%
PVA). The diluted emulsion was rotary evaporated for 25 min
(20.degree. C. and 65.degree. C.), after the vacuum was turned off
and the dispersion was kept at 65.degree. C. for a further 1 h. The
rotary speed was 250 rpm. The dispersion of microspheres was
filtered by using filtration pump and qualitative filter paper, 413
(particle retention: 5-13 mm). The product was cleaned with
distilled water (.about.1.5 L) and afterwards it was washed three
times with heptane.
Example 3
[0125] Preparation of Particles of a Crosslinking Agent
[0126] PMMA (1 g) was dissolved in dichloromethane (DCM) (75 ml)
and then the crosslinking agent HMS-301
(methyl-hydrosiloxane-dimethylsiloxane) from Gelest, Inc., (1.5 g)
was added to form an oil phase. An aqueous surfactant solution
(77.5 g of 1% PVA) was prepared and added to a 250 ml conical
flask. The aqueous phase was mechanically stirred at 2000 rpm for 2
min, and the oil phase was added over 60 s to form an oil-in-water
emulsion. The agitation was kept for 1 h at 1000-750 rpm before
pouring the emulsion into a further 120 ml of aqueous surfactant
solution (1% PVA). The diluted emulsion was rotary evaporated for
25 min (20.degree. C. and 65.degree. C.) after the vacuum was
turned off and the dispersion was kept at 65.degree. C. for a
further 1 h. The rotary speed was 250 rpm. The dispersion of
microspheres was filtered by using filtration pump and qualitative
filter paper, 413 (particle retention: 5-13 mm). The product was
cleaned with distilled water (.about.1.5 L) and afterwards it was
washed three times with heptane.
Example 4
[0127] Preparation of a Treatment Fluid Containing Uncoated
Elastomer Microspheres
[0128] 10 g of the silicone microspheres of Example 1.1, 0.5 g of
the particles of a crosslinking agent of Example 3 and 10 g of
silicone oil Dow Corning.RTM. OS20 as base fluid were mixed at room
temperature and then heated to 70.degree. C. where the silicone
elastomer crosslinked and set to form a plug of approximate
strength 50 Shore A.
Example 5
[0129] Preparation of a Treatment Fluid Containing Coated Elastomer
Microspheres
[0130] 20 g of the silicone microspheres of Example 1.2, 0.5 g of
the particles of a crosslinking agent of Example 3 and 10 g of
silicone oil Dow Corning.RTM. OS20 as base fluid were mixed at room
temperature and then heated to 70.degree. C. where the silicone
elastomer crosslinked and set to form a plug of approximate
strength 50 Shore A.
Example 6
[0131] 10 g of the silicone microspheres of Example 1.1, 0.5 g of
the particles of a crosslinking agent of Example 3 and 100 g of tap
water as base fluid were mixed at room temperature and then heated
to 70.degree. C. where the silicone elastomer crosslinked and set
to form a plug in the top of the mixture upon setting of the
mixture of approximate strength 50 Shore A.
Example 7
[0132] 20 g of the silicone microspheres of Example 1.2, 0.5 g of
the particles of a crosslinking agent of Example 3 and 100 g of tap
water as base fluid were mixed at room temperature and then heated
to 70.degree. C. where the silicone elastomer crosslinked and set
to form a plug in the top of the mixture upon setting of the
mixture of approximate strength 50 Shore A.
Example 8
[0133] 10 g of the silicone microspheres of Example 2 and 1 g of
the particles of a crosslinking agent of Example 3 and 100 g of tap
water as base fluid were mixed at room temperature and then heated
to 70.degree. C. where the silicone elastomer crosslinked and set
to form a plug at the top of the mixture upon setting of the
mixture of approximate strength 50 Shore A.
Example 9
[0134] Preparation of PMMA Coated Cured PDMS Microspheres
[0135] 1 g of microspheres (20:1) according to Example 1.1 were
added to 50 ml of 1% PVA solution in a 100 ml beaker. The mixture
was sonicated for 15 min and afterwards cooled to room temperature.
Then the solution with microspheres was poured into a 250 ml beaker
and 50 ml of 1.3% PMMA solution in acetone was added to the mixture
with mechanical stirring at 150 rpm. The agitation was kept for 2
hours. After that time the mixture was heated for the next 2 hours
(65.degree. C.) on a hot plate in a water bath. The agitation speed
remained the same. The microcapsules were left in a fume hood
overnight while stirring at room temperature. After that time all
acetone had evaporated and only a small amount of water was left.
The microspheres did not agglomerate. In the end, the microspheres
were filtered and cleaned with deionized water.
Example 10
[0136] Preparation of Different PMMA Coated Particles of a
Crosslinking Agent
[0137] The preparation procedure for all PMMA coated particles was
similar as set forth below.
[0138] PMMA and the crosslinking agent HMS-301 from Gelest, Inc.
were dissolved in dichloromethane (DCM) to provide an oil phase.
Then the oil phase was added to equal volumes of surfactant
solution, either PVA or PMAA. In some cases acetone was added to
the oil phase. While adding the oil phase the emulsion was
mechanically stirred at 2000 rpm. After that the speed was
decreased to 750 rpm and the emulsion was stirred for another 1
hour. The mixture was then diluted with 120 ml of surfactant
solution and DCM was removed by using rotary evaporator. The
particles were then washed with deionized water and heptane on a
filter paper and dried at room temperature.
[0139] The different PMMA coated particles appear from table IV
below.
TABLE-US-00004 TABLE IV Content [HMS- [Sur- of En- For- [PMMA] 301]
factant] [Acetone] HMS-301 try mulation (%) (%) % % % 1 PMMA -- --
-- -- -- 2 HMS-301 -- -- -- -- -- 3 PMMA 1 1.5 PVA No 56 capsules 4
PMMA 1 1.5 PMAA Yes (2.5) 7 capsules 5 PMMA 3.3 5.0 PMAA Yes 12
capsules 6 PMMA 2.4 3.7 PVA No 36 capsules 7 PMMA 2.4 3.7 PVA Yes
47 capsules 8 PMMA 1 1.5 PVA No 44 capsules 9 PMMA 1 1.5 PVA Yes 48
capsules 10 PMMA 2.4 3.7 PMAA No 31 capsules 11 PMMA 2.4 3.7 PMAA
Yes 21 capsules 12 PMMA 1 1.5 PMAA No 8 capsules 13 PMMA 1 1.5 PMAA
Yes 16 capsules
LIST OF REFERENCES
[0140] WO 2007/141519 A2 [0141] WO 2007/010210 [0142] WO
2008/009957 [0143] US 2006/234871 [0144] US 2008/0017376 [0145]
U.S. Pat. No. 4,649,998
* * * * *