A cementitious composition comprising polymer microgels as gas migration inhibitors

Abstract

The present invention relates to the field of cementing technology, particularly in the construction of oil and / or gas wells or geothermal energy. More specifically, the subject matter of the present invention is a cement-based composition and an improved cementing method, which is to introduce a polymer microgel as a gas migration inhibitor into the cement.

Description

Technical Field

[0001] The present invention relates to the field of cementing technology, especially in the construction of oil and / or gas wells or geothermal energy. More specifically, the subject of the present invention is a cement-based composition and an improved cementing method, which is to introduce a polymer microgel as an anti-gas migration agent into the cement slurry. Background Art

[0002] Cementing involves pumping a cement slurry from the surface into the casing, and the cement slurry returns to the surface through the annular space between the casing and the borehole. One of the purposes of cementing is to isolate different formations penetrated by the drilling to prevent the migration of fluids (liquids or gases) between different geological layers or between the geological layer and the surface. In particular, from a safety perspective, it is necessary to prevent any gas from rising through the annular space between the wellbore (borehole) and the casing.

[0003] During the cementing stage, pressurized gas underground will penetrate through the various strata that the drilling and the cement pass through. This is a critical stage that lasts for several hours, during which the cement slurry no longer behaves as a liquid but has not yet behaved as an impermeable solid. This phenomenon occurs when the cement slurry has solidified to a certain extent and the hydrostatic pressure of the cement column is insufficient to prevent the propagation of pressurized gas cavities in the cement slurry. During the setting process, the gas will circulate in the cement column, forming multiple channels in the cement and reaching the surface. This flow of gas can lead to out-of-control pressure and even cause an explosion, which is why a series of additives have been developed in the industry to maintain gas tightness during the entire cement setting period.

[0004] These additives include latex, such as natural latex. Since the 1920s, such additives have been commonly used in Portland cement, especially due to the improvement of the mechanical properties of the cement. In the 1980s, Parcevaux et al. found that styrene-butadiene rubber is an effective additive to prevent annular gas migration, which was a decisive improvement. This technology was specifically introduced in U.S. Patent Document No. 4,537,918, which discloses a slag cement composition in which styrene-butadiene rubber can inhibit the escape of gas under pressure in the cement sheath even under high-temperature conditions.

[0005] WO 2012 / 150431 teaches a cementing fluid containing a polymer suspending agent, which can be prepared by inverse suspension polymerization, optionally in an inverse emulsion.

[0006] WO 2004 / 101952 describes a composition for cementing.

[0007] US2015 / 203402 describes a polycarboxylic acid copolymer additive for a cement composition.

[0008] WO 01 / 05365 describes a composition comprising a monomeric moiety of a water-soluble branched or crosslinked amphoteric polymer.

[0009] WO 2018 / 185037 describes a composition and its use as an agent for controlling filtrate and / or gas migration in a fluid injected underground under pressure.

[0010] Although styrene-butadiene rubber-based additives are the most commonly used additives for preventing gas migration, these products, while effective, require high concentrations and are relatively expensive. In addition, as described in US 4,537,918 and US 4,151,150, some products require the use of stabilizers to prevent their setting in cement.

[0011] FR 2704219 introduces a fluid loss control agent with gas migration resistance properties, suitable for petroleum industry fluids, especially cement slurries. This fluid loss control agent consists of a polymer obtained by chemical crosslinking of polyvinyl alcohol (PVA).

[0012] These fluid loss control agents are water-soluble polymers, and their effects are usually limited because some additives cannot be used at high concentrations due to the high viscosity of the slag during the mixing stage. These additives have limited effects in terms of reproducibility, performance, and stability, especially at temperatures above 50 °C.

[0013] U.S. Patent No. 4,569,395 proposes adding cellulose derivatives (such as hydroxyethyl cellulose) to cement in order to use PVA at temperatures up to 95 °C.

[0014] The formation of gas channels is a very serious problem because it can lead to embrittlement of the cement and problems related to surface safety.

[0015] The amount of effort made to solve this problem is sufficient to illustrate the severity of the problem, which has been a major concern of producers for many years.

[0016] There is still a need for additives that can make cement more effectively non-leaking during the setting process, can be used under any temperature conditions, and do not require additional additives.

[0017] The inventors have unexpectedly found that, compared with traditional products, the use of specific microgels can endow cement with more excellent gas migration resistance properties. Regardless of the temperature conditions, the microgels of the present invention exhibit good performance, and the required dosage is much less than that of the prior art solutions.

[0018] Using the cement - based composition of the present invention is part of the general principle of improving product performance, especially improving the performance of gas migration resistance agents. The better performance of the polymer microgels according to the present invention can reduce the amount of product required during application, which means that the emissions of greenhouse gases (such as carbon dioxide) associated with the manufacture and use of synthetic polymers can be reduced. Summary of the Invention

[0019] The present invention relates to a cement - based composition comprising:

[0020] - Cement;

[0021] - Optionally at least one cement additive;

[0022] - Polymer microgels; and

[0023] - Water.

[0024] The cement - based composition can be composed of these compounds.

[0025] In such a cement - based composition, the polymer microgels comprise at least one polymer structured by at least one cross - linker. This structured polymer is polymerized from at least one monomer in an inverse emulsion (water - in - oil emulsion).

[0026] The present invention also relates to a cementing process comprising injecting underground a cement - based composition containing polymer microgels comprising at least one structured polymer, the structured polymer being obtained by an inverse emulsion.

[0027] Description of the Invention

[0028] According to the present invention, the term "gas migration resistance agent" refers to an additive capable of restricting gas migration during the setting of cement.

[0029] Generally, a fluid loss control agent can restrict the loss of liquid fluids during the fluid loss stage of cementing, such as water loss when contacting porous zones such as underground clay layers.

[0030] In the literature, the effectiveness of gas migration resistance agents and that of fluid loss control agents are measured in the same way. Therefore, people wrongly think that fluid loss control agents have the property of gas migration resistance. However, although gas migration resistance agents do have the effect of restricting fluid loss, fluid loss control agents do not necessarily affect gas migration. Therefore, measuring the amount of liquid loss to measure the effect of gas migration resistance agents cannot evaluate the effect of gas migration resistance agents.

[0031] To determine the effectiveness of the gas migration inhibitor, a Static Gel Strength Analyzer (SGSA) is required. This device measures the Static Gel Strength (SGS) of cement under high temperature and high pressure conditions. The instrument is equipped with an internal processor board that sends and receives ultrasonic pulses through the cement slurry and then post-processes the data to determine the functional relationship between gel strength and time in a static medium.

[0032] Once the cement slurry is stationary, gel strength is generated, resulting in a loss of hydrostatic pressure (the pressure exerted by the cement slurry on the wellbore (drilling hole) and casing). When the hydrostatic pressure is lower than the pore pressure in the drilling zone, gas can infiltrate and migrate to areas of lower pressure, potentially reaching the surface. During the transition period, the cement slurry is neither a liquid capable of transmitting hydrostatic pressure nor a solid. At this time, the cement slurry has a gel structure. The gel strength value at which the hydrostatic pressure is lower than the pore pressure is called the Critical Static Gel Strength (CSGS). As a preventive measure, the gel strength value at which gas cannot migrate through the cement is 239 Pa (500 lb / 100 ft 2 ). Therefore, generally speaking, the transition period between CSGS and 239 Pa must be as short as possible to avoid the risk of gas migration. From a regulatory and safety perspective, the transition time must be less than 45 minutes. When the CSGS is at least 100 lb / 100 ft 2 (100 lb / 100 ft 2 = 0.4788 Pa), the slurry begins to gel, and when the CSGS is at least 500 lb / 100 ft 2 , the risk of gas migration ends. Those skilled in the art are familiar with conventional measurement equipment and methods. If necessary, those skilled in the art can refer to Chapter 5 of Volume 1 of "Fluid Chemistry Drilling and Completion".

[0033] The term "polymer" refers to a homopolymer or copolymer, where a copolymer refers to a polymer prepared from at least two different monomers. Therefore, it can be a copolymer of at least two monomers, and these two monomers can be selected from anionic monomers, cationic monomers, non-ionic monomers, zwitterionic monomers, and mixtures thereof.

[0034] The term "polymer microgel" refers to the microgel described on pages 227 - 275 of Chapter 8 of the document "Polymer Networks". Such a polymer is a roughly spherical structural polymer, and its size is comparable to the molecular size of a linear polymer or a branched polymer. A microgel is a microscopic network, and its properties depend on its cross-linking density, connectivity, the presence of a solvent, etc. A microgel is a polymer particle insoluble in the medium.

[0035] As used herein, "X and / or Y" means "X" or "Y" or "X and Y".

[0036] The present invention also includes all possible combinations between the various disclosed embodiments, whether these combinations are preferred embodiments or given by way of example.

[0037] Furthermore, when indicating a numerical range, the limiting values are also part of these ranges. The disclosure also includes all combinations between the limits of these numerical ranges. For example, the numerical range 1 - 20, preferably 5 - 15, means that the ranges "1 - 5", "1 - 15", "5 - 20" and "15 - 20" as well as the numerical values 1, 5, 15 and 20 are disclosed.

[0038] According to the process of the present invention, by selecting the preparation method of the polymer microgel and the chemical composition of the polymer microgel, cements of better quality can be obtained.

[0039] Composition

[0040] The present invention relates to a cement - based composition, comprising:

[0041] - Cement;

[0042] - Optionally at least one cement additive;

[0043] - Polymer microgel; and

[0044] - Water.

[0045] In such a cement - based composition, the polymer microgel comprises at least one structured polymer. The structured polymer is obtained by the polymerization reaction of monomers in an inverse emulsion.

[0046] The cement is preferably selected from pozzolanic materials such as lime - based mixtures, silica, alumina, calcium sulfate, Portland cement, ground granulated blast - furnace slag, fly ash and their mixtures, etc.

[0047] Cement additives are generally selected from additives commonly used in the application field, including but not limited to dispersants, anti - fluid - loss agents, retarders and their mixtures.

[0048] Generally, relative to the total weight of the cement - based composition, the weight of the polymer microgel in the cement - based composition is preferably between 100 and 100,000 ppm, more preferably between 500 and 50,000 ppm, and most preferably between 500 and 10,000 ppm.

[0049] The present invention also relates to the use of a polymer microgel for forming a cement - based composition, the polymer microgel comprising at least one polymer structured by at least one cross - linker,

[0050] wherein the structured polymer is obtained by inverse emulsion polymerization of at least one monomer.

[0051] The present invention also relates to a method for preparing a cement-based composition, said composition comprising a mixture of the following compounds:

[0052] - a polymer microgel;

[0053] - cement;

[0054] - water; and

[0055] - optionally at least one cement additive;

[0056] Said polymer microgel contains at least one polymer structured by at least one crosslinking agent,

[0057] wherein the structured polymer is obtained by inverse emulsion polymerization of at least one monomer.

[0058] Polymer microgel

[0059] The polymer microgel is a synthetic polymer microgel. Preferably, it contains a structured polymer polymerized from at least one anionic monomer and / or at least one non-ionic monomer and / or at least one cationic monomer and / or at least one zwitterionic monomer and / or at least one hydrophobic monomer. Preferably, these monomers have unsaturated olefinic bonds (double bonds between two carbon atoms).

[0060] In another preferred embodiment, the polymer microgel comprises at least one anionic monomer and optionally at least one non-ionic monomer.

[0061] Preferably, other anionic monomers that can be used within the scope of the present invention can be selected from a large class of monomers. These monomers can have functional vinyl groups, especially acrylic, maleic, fumaric, malonic, itaconic or allyl groups. These monomers can also contain carboxyl, phosphonic, phosphoric, sulfonic or other anionic groups. Preferably, monomers belonging to this class are selected from the group consisting of: acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, acrylamidoundecanoic acid, 3-acrylamido-3-methylbutyric acid, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid (ATBS), vinylsulfonic acid, vinylphosphonic acid, allylsulfonic acid, methallylsulfonic acid, 2-sulfoethyl methacrylate, sulfopropyl methacrylate, sulfopropyl acrylate, allylphosphonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanedisulfonic acid, and their salts, or combinations thereof. Preferably, it is 2-acrylamido-2-methylpropanesulfonic acid (ATBS) and / or its salts.

[0062] In a particular embodiment of the present invention, the anionic monomer can be salified (salts).

[0063] By salification is meant that at least one acid functional group of an anionic monomer is replaced by a salt that neutralizes the negative charge of the acid functional group. In other words, the non-salified form corresponds to the acidic form of the monomer, such as the R-C(=O)-OH form of a carboxylic acid functional group, while the neutralized form of the monomer corresponds to the R-C(=O)-O - X + form, where X + corresponds to a positively charged salt. The neutralization of the acid functional groups in the polymer microgel can be partial or complete.

[0064] The salified form is preferably a salt of an alkali metal (Li, Na, K, etc.), an alkaline earth metal (Ca, Mg, etc.) or ammonium (such as ammonium ion or tertiary ammonium). The preferred salt is sodium salt.

[0065] Salification can be carried out before polymerization, during polymerization or after polymerization.

[0066] The content of the anionic monomer in the polymer microgel is preferably between 0 and 100 mol%, more preferably between 20 and 100 mol%, more preferably between 40 and 100 mol%, more preferably between 50 and 100 mol%.

[0067] The polymer microgel preferably contains at least 30 mol% of the anionic monomer, more preferably at least 50 mol%, more preferably at least 70 mol%, more preferably at least 90 mol%, and more preferably contains only the anionic monomer. Therefore, the polymer microgel is preferably a polymer of at least one acidic and / or salified anionic monomer.

[0068] In a particular embodiment of the present invention, the polymer microgel preferably contains 0 to 100 mol% of the salified anionic monomer, preferably 0 to 50 mol%.

[0069] In a particular embodiment of the present invention, when the anionic monomer is 2-acrylamido-2-methylpropanesulfonic acid, it is in the hydrated form. The hydrated form of 2-acrylamido-2-methylpropanesulfonic acid is a particular form of 2-acrylamido-2-methylpropanesulfonic acid and can be obtained by controlling the crystallization of the 2-acrylamido-2-methylpropanesulfonic acid monomer. US10,759,746 describes the hydrated form of 2-acrylamido-2-methylpropanesulfonic acid.

[0070] Preferably, the non-ionic monomers that can be used in the present invention are selected from the group consisting of: acrylamide, methacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-hydroxymethylacrylamide, N-vinylformamide (NVF), N-vinylacetamide, N-vinylpyridine, and N-vinylpyrrolidone (NVP), N-vinylimidazole, N-vinylcaprolactam, N-vinylsuccinimide, acryloylmorpholine (ACMO), acryloyl chloride, glycidyl methacrylate, glycerol methacrylate, diacetone acrylamide, hydroxyalkyl (meth)acrylate (C1-C3 alkyl), aminoalkyl (meth)acrylate (C1-C3 alkyl), thioalkyl (meth)acrylate (C1-C3 alkyl), or a combination thereof. Preferably, acrylamide is used.

[0071] The content of the non-ionic monomer in the polymer microgel is preferably between 0 and 100 mol%, more preferably between 0 and 80 mol%, more preferably between 0 and 60 mol%, more preferably between 0 and 50 mol%.

[0072] The content of the non-ionic monomer in the polymer microgel is preferably less than 70 mol%, more preferably less than 50 mol%, more preferably less than 30 mol%, more preferably less than 10 mol%.

[0073] Preferably, the cationic monomers that can be used in the present invention can be selected from vinyl-type monomers, especially acrylamide, acrylic acid, allyl, or maleic acid monomers having an ammonium functional group (preferably quaternary ammonium). Preferred monomers belonging to this category are selected from the group consisting of: quaternized-dimethylaminoethyl-acrylate (DMAEA), quaternized-dimethylaminoethyl-methacrylate (DEAEMA), dimethyldiallylammonium chloride (DADMAC), acrylamido-propyltrimethyl-ammonium chloride (APTAC), methacrylamido-propyltrimethyl-ammonium chloride (MAPTAC), or a combination thereof.

[0074] The polymer microgel preferably contains 0 to 100 mol% of the cationic monomer, more preferably 0 to 80 mol%, more preferably 0 to 60 mol%, more preferably 0 to 50 mol%.

[0075] The content of the cationic monomer in the polymer microgel is preferably less than 70 mol%, more preferably less than 50 mol%, more preferably less than 30 mol%, more preferably less than 10 mol%.

[0076] Those skilled in the art know how to prepare quaternized monomers, for example, by R-X alkyl halides, where R is an alkyl group (preferably C1-C3) and X is a halogen (especially methyl chloride). In addition, the present invention also includes monomers of the DADMAC, APTAC, and MAPTAC types, whose halide counterions are fluorides, bromides, or iodides instead of chlorides.

[0077] The zwitterionic monomers used in the present invention are preferably derived from vinyl units, especially acrylamide, acrylic acid, allyl, or maleic acid. Such monomers have amine or ammonium functional groups (preferably quaternary ammonium) and acid functional groups of carboxylic acid (or carboxylate), sulfonic acid (or sulfonate), or phosphoric acid (or phosphate), or combinations thereof. Examples of zwitterionic monomers include derivatives of dimethylaminoethyl acrylate, such as 2-((2-(acryloyloxy)ethyl)dimethylamino)ethane-1-sulfonate. In particular, it may include (but is not limited to): 3-((2-(acryloyloxy)ethyl)dimethylamino)propane-1-sulfonate, 4-((2-(acryloyloxy)ethyl)dimethylamino)butane-1-sulfonate, [2-(acryloyloxy)ethyl](dimethylamino)acetate, derivatives of dimethylaminoethyl methacrylate, such as 2-((2-(methacryloyloxy)ethyl)dimethylamino)ethane-1-sulfonate, 3-((2-(methacryloyloxy)ethyl)dimethylamino)propane-1-sulfonate, 4-((2-(methacryloyloxy)ethyl)dimethylamino)butane-1-sulfonate, [2-(methacryloyloxy)ethyl](dimethylamino)acetate, derivatives of dimethylaminopropyl acrylamide, such as 2-((3-acrylamidopropyl)dimethylamino)ethane-1-sulfonate, 3-((3-acrylamidopropyl)dimethylamino)propane-1-sulfonate, 4-((3-acrylamidopropyl)dimethylamino)butane-1-sulfonate, [3-(acryloyloxy)propyl](dimethylamino)acetate, dimethylaminopropyl methacrylamide or derivatives, such as 2-((3-methacrylamidopropyl)dimethylamino)ethane-1-sulfonate, 3-((3-dimethylamino)propane-1-sulfonate, 4-((3-methacrylamidopropyl)dimethylamino)butane-1-sulfonate, and propyl [3-(methacryloyloxy)](dimethylamino)acetate and their mixtures. FR 3104578 also describes examples of zwitterionic monomers that can be used.

[0078] Preferably, the monomers having hydrophobicity that can be used in the present invention are selected from the following groups: having a C4-C 30 alkyl chain, arylalkyl (C4-C 30 alkyl, C4-C 30 aryl), propoxylated, ethoxylated, or ethoxylated and propoxylated (meth)acrylates; having a C4-C30 Alkyl, propoxylated arylalkyl (C4-C 30 Alkyl, C4-C 30 aryl), ethoxylated, ethoxylated and propoxylated or di-C4-C 30 (meth)acrylamide derivatives; alkyl aryl sulfonates (C4-C 30 alkyl, C4-C 30 aryl), or those derived from (meth)acrylamides having a C4-C 30 alkyl chain, arylalkyl (C4-C 30 alkyl, C4-C 30 aryl), propoxylated, ethoxylated, or ethoxylated and propoxylated, which are mono- or di-substituted amides; (meth)acrylamide derivatives having a C4-C 30 alkyl, propoxylated arylalkyl (C4-C 30 alkyl, C4-C 30 aryl), ethoxylated, ethoxylated and propoxylated, or C4-C 30 di-alkyl chain; alkyl aryl sulfonates (C4-C 30 alkyl, C4-C 30 aryl), or combinations thereof. Generally, aryl is preferably C5-C 30 or C6-C 30 .

[0079] Preferably, the content of hydrophobic monomers in the polymer microgel is less than 10 mol%.

[0080] In a particular embodiment of the present invention, the polymer microgel may comprise at least one thermosensitive monomer. By a thermosensitive monomer is meant a monomer that changes the physical properties of the polymer with temperature. For example, groups at the lower critical solution temperature (LCST), such as LCST macromonomers; groups at the upper critical solution temperature (UCST), such as UCST macromonomers, may be mentioned. Those skilled in the art are aware of these types of monomers, which are known and conventional in the general knowledge of the art, and if necessary, those skilled in the art may refer to WO 2016162532.

[0081] In the process of preparing the polymer microgel, the amounts of the various monomers can be adjusted by a person skilled in the art so that they do not exceed 100 mol%.

[0082] The polymer microgel is structured by at least one crosslinking agent. Preferably, such a crosslinking agent is selected from polyvinyl unsaturated monomers (which have at least two unsaturated functional groups), such as vinyl groups, especially allyl and propenyl functional groups, or monomers having at least two epoxy functional groups. Examples that may be mentioned are methylene bisacrylamide (MBA), triallylamine, tetraallylammonium chloride, 1,2-dihydroxy-ethyl-bis(N-acrylamide) or (meth)acrylates having multiple functional groups, such as poly(meth)acrylate (ethylene glycol) (PEG-di(meth)acrylate). Preferably, methylene bisacrylamide is used.

[0083] Based on the weight of the monomers, preferably the amount of the crosslinking agent is less than 5%, more preferably less than 1%, more preferably less than 0.5%, more preferably less than 0.3%. According to a particular embodiment, based on the weight of the monomers, it is at least equal to 0.005%, more preferably at least equal to 0.01%, more preferably at least equal to 0.05%.

[0084] As described above, the structured polymer is obtained by inverse emulsion. The structured polymer is formed in the hydrophilic phase droplets containing the monomers, thereby producing polymer microgels.

[0085] Inverse emulsion

[0086] The emulsion consists of a turbid two-phase medium. In the absence of surfactants (surfactants include water-in-oil emulsifiers and oil-in-water emulsifiers), the emulsion may be unstable. Under stirring, particles dispersed in water or oil can be observed, and their size distribution is very wide, and the average value may be around one micron. During emulsion polymerization, the monomers are dispersed in large emulsion droplets (with a diameter of about 1 μm to 10 μm) and small emulsifier micelles (with a diameter of about 5 to 10 nm).

[0087] Such polymerization techniques, especially inverse emulsion techniques, are well known to those skilled in the art. It involves emulsifying the hydrophilic phase containing the monomers and the crosslinking agent in the lipophilic phase. This emulsification is carried out using a water-in-oil emulsifier.

[0088] An inverse emulsion generally includes at least:

[0089] - A hydrophilic phase, including monomers and a crosslinking agent;

[0090] - A lipophilic phase;

[0091] - At least one water-in-oil emulsifier;

[0092] - At least one oil-in-water emulsifier.

[0093] An inverse emulsion includes droplets (hydrophilic phase) dispersed in the lipophilic phase.

[0094] In the present invention, the term "water-in-oil emulsifier" refers to a compound capable of emulsifying water in oil, while the "oil-in-water emulsifier" refers to a compound capable of emulsifying oil in water. Generally, water-in-oil emulsifiers are surfactants with a hydrophilic-lipophilic balance (HLB) strictly less than 8, while oil-in-water emulsifiers are surfactants with an HLB greater than or equal to 10. Surfactants with an HLB between 8 and 10 are regarded as wetting agents. If necessary, those skilled in the art may refer to Chapter 11 of "Handbook of Applied Surface and Colloid Chemistry" by K. Holmberg.

[0095] The hydrophilic-lipophilic balance (HLB) of a compound is a measure of its hydrophilicity and / or lipophilicity, determined by calculating values for different segments of the molecule, as described by Griffin in 1949.

[0096] In the present invention, we have adopted Griffin's method, i.e., calculating values based on the chemical groups of the molecule. Griffin assigned a dimensionless value between 0 and 20 to provide information on water solubility and oil solubility.

[0097] The HLB value of a substance with a total molecular weight M and a hydrophilic part with molecular weight Mh is obtained from the following formula:

[0098] HLB = 20(Mh / M)

[0099] The lipophilic phase of the inverse emulsion can be mineral oil, vegetable oil, synthetic oil, or a mixture of several oils.

[0100] Examples of mineral oils include mineral oils containing aliphatic, naphthenic, paraffinic, isoparaffinic, naphthenic, or naphthalene saturated hydrocarbons.

[0101] Examples of synthetic oils are hydrogenated polydecene or hydrogenated polyisobutene, and esters such as octyl stearate or butyl oleate. The product series of Exxon Corporation is very suitable.

[0102] The solvent of the hydrophilic phase of the inverse emulsion is preferably water.

[0103] Generally, during the polymerization process, the weight ratio of the hydrophilic phase to the lipophilic phase of the inverse emulsion is preferably between 50 / 50 and 90 / 10, more preferably between 70 / 30 and 80 / 20.

[0104] Preferably, the inverse emulsion contains at least one water-in-oil emulsifier selected from the group consisting of: sorbitan extracts such as sorbitan monooleate or sorbitan polyoleate, sorbitan isostearate or sorbitan sesquioleate, polyethoxylated sorbitan esters, diethoxylated cetyl oleyl alcohol, tetraethoxylated lauryl acrylate, condensation products of higher fatty alcohols with ethylene (such as the reaction product of oleyl alcohol and 2 units of ethylene oxide), condensation products of alkylphenols with ethylene oxide (such as the reaction product of nonylphenol and 4 units of ethylene oxide), or combinations thereof. Ethoxylated fatty amines (such as 511), betaine products, and ethoxylated amines and their mixtures can also be used as emulsifiers.

[0105] Generally, the weight of the water-in-oil emulsifier in the inverse emulsion accounts for 0.1% to 10% of the total weight of the inverse emulsion.

[0106] Preferably, the inverse emulsion can contain a stabilizer. For example: polyesters with a molecular weight between 1000 and 3000 g / mol, condensation products of polyisobutylene succinic acid or its anhydride with polyethylene glycol, where the molecular weight of the water-soluble block polymer is between 2500 and 3500 g / mol, such as the product sold under the name.

[0107] Generally, relative to the total weight of the inverse emulsion, the inverse emulsion contains 0.1 to 10% (by weight) of the stabilizer.

[0108] The oil-in-water emulsifier is preferably selected from ethoxylated nonylphenols, preferably having 4 to 10 ethoxy groups (i.e., the degree of ethoxylation is preferably between 4 and 10); ethoxylated / propoxylated alcohols, preferably having 12 to 25 carbon atoms in the ethoxylated / propoxylated group; ethoxylated tridecyl alcohol; ethoxylated / propoxylated fatty alcohols; ethoxylated sorbitan esters (preferably having 20 molar equivalents of ethylene oxide); polyethoxylated sorbitan laurate (preferably having 20 molar equivalents of ethylene oxide); polyethoxylated castor oil (preferably having 40 molar equivalents of ethylene oxide); decaethoxylated oleyl alcohol; heptaoxyethyl lauryl alcohol; polyethoxylated sorbitan monostearate (preferably having 20 molar equivalents of ethylene oxide); polyethoxylated alkylphenols (preferably having 10 molar equivalents of ethylene oxide) cetyl ether; polyoxyethylene alkyl aryl ethers; N-hexadecyl-N-ethyl morpholine ethanesulfonate; sodium lauryl sulfate; condensation products of fatty alcohols with ethylene oxide (preferably having 10 molar equivalents of ethylene oxide); condensation products of alkylphenols with ethylene oxide (preferably having 12 molar equivalents of ethylene oxide); condensation products of fatty amines with 5 or more molar equivalents of ethylene oxide (preferably 5 to 50 molar equivalents); ethoxylated triphenylvinyl phenol; condensation products of ethylene oxide with partially esterified polyols with fatty chains and their anhydrous forms; amine oxides, preferably alkyl polyglucosides; glucamides; phosphate esters; alkyl benzene sulfonic acids and their salts; and surfactant water-soluble polymers. The oil-in-water emulsifier can also be a mixture of one or more oil-in-water emulsifiers. The alkyl group of the oil-in-water emulsifier refers to a straight-chain or branched-chain group, preferably having 1 to 20 carbon atoms, more preferably 3 to 15 carbon atoms. In addition, the aryl group of these oil-in-water emulsifiers preferably has 6 to 20 carbon atoms, more preferably 6 to 12 carbon atoms and their mixtures.

[0109] Generally, relative to the total weight of the inverse emulsion, the weight of the oil-in-water emulsifier in the inverse emulsion is between 0.01 and 10%.

[0110] Generally, relative to the total weight of the inverse emulsion, the concentration of the polymer microgel in the inverse emulsion is between 5 and 65%, preferably between 20 and 50%.

[0111] The polymerization of the monomer is a free radical polymerization. The so-called free radical polymerization includes polymerization using ultraviolet light initiators, azo initiators, redox initiators or thermal initiators.

[0112] The polymerization initiator can be selected from compounds that dissociate into free radicals under polymerization conditions, such as: organic peroxides, hydroperoxides, hydrogen peroxide, persulfates, azo compounds and redox catalysts. It is preferably to use water-soluble initiators. In some cases, it is preferably to use a mixture of various polymerization initiators, such as a mixture of redox catalysts and azo compounds.

[0113] In a preferred embodiment of the present invention, the polymer microgels are prepared by polymerizing monomers in a reversed micellar microemulsion.

[0114] The preparation method of the reversed micellar microemulsion can be the same as the method described in the literature "Application of the Cohesive Energy Ratio Concept (CER) in the Formation of Polymerizable Microemulsions" by C. Holtzscherer and F. Candau (Volume 29, Issue 4, pages 411 - 423, 1988).

[0115] The goal is to reach the thermodynamic stability critical value of the water phase / lipophilic phase / surfactant ternary system. In this way, a transparent and flowing microemulsion can be formed.

[0116] A microemulsion can also be obtained by providing mechanical energy to reduce the droplet size of the hydrophilic phase of the emulsion to between 20 nm and 500 nm, preferably between 50 nm and 250 nm, more preferably between 80 nm and 150 nm.

[0117] The particle size (microgel particle size) corresponds to the droplet size of the hydrophilic phase of the microemulsion. Therefore, the particle size of the microgels is between 20 nm and 500 nm, preferably between 50 nm and 250 nm, more preferably between 80 nm and 150 nm.

[0118] Generally, during the preparation process, the structured polymer of the microgels is saturated in water, and the swelling volume in the cement - based composition cannot exceed 20%, preferably does not exceed 10%, more preferably does not swell at all. For example, when the size of the prepared microgels is 100 nm, their size in the cement - based composition does not exceed 120 nm, preferably does not exceed 110 nm, and more preferably remains 100 nm.

[0119] If necessary, those skilled in the art can refer to EP2802936 to understand how to produce microemulsions.

[0120] Generally, relative to the total weight of the reversed micellar microemulsion, the content of the structured polymer in the reversed micellar microemulsion is between 5% and 65%, preferably between 10% and 50%, more preferably between 15% and 40%.

[0121] Generally, during the polymerization process, the weight ratio of the hydrophilic phase to the lipophilic phase of the reversed micellar microemulsion is preferably between 80 / 20 and 20 / 80, more preferably between 70 / 30 and 30 / 70, and even more preferably between 60 / 40 and 40 / 60.

[0122] Preferably, the water-in-oil emulsifier in the reverse microemulsion is selected from sorbitan esters (such as sorbitan monooleate, sorbitan isostearate, sorbitan sesquioleate, sorbitan trioleate or a mixture thereof), oleyl diethanolamide, or a combination thereof.

[0123] Generally, the weight of the water-in-oil emulsifier in the reverse microemulsion accounts for 0.01 to 10% of the total weight of the reverse microemulsion, preferably between 0.1 and 5%.

[0124] Preferably, the oil-in-water emulsifier in the reverse microemulsion can be selected from the following group: ethoxylated sorbitol esters, such as ethoxylated sorbitol oleate containing 20 moles of ethylene oxide, ethoxylated sorbitol hexaoleate, decaethoxylated oleyl cetyl alcohol, nonylphenol (10EO) containing 10 moles of ethylene oxide, polyethoxylated sorbitol hexaoleate, or a combination thereof.

[0125] Generally, the weight of the oil-in-water emulsifier in the reverse microemulsion accounts for 0.1% to 20% of the total weight of the reverse microemulsion, preferably 0.5% to 15%.

[0126] According to the present invention, the size of the microemulsion droplets (hydrophilic phase) is between 20 nm and 500 nm, preferably between 50 nm and 250 nm, more preferably between 80 nm and 150 nm.

[0127] The so-called "size of the microemulsion droplets" refers to the average size of the droplet population. This size corresponds to the measured average diameter, preferably measured using a laser measuring device and conventional techniques that have become part of the knowledge of those skilled in the art. A Zetasizer Nano device from Malvern can be used.

[0128] Cementing process

[0129] The present invention also relates to a cementing process, which includes injecting a cement-based composition into a subterranean formation. In this process, the cement-based composition includes a polymer microgel containing at least one structured polymer, and the structured polymer is obtained by polymerizing monomers in a reverse microemulsion.

[0130] In other words, more specifically, the method according to the present invention includes the following steps:

[0131] - Preparing a cement-based composition containing a polymer microgel, wherein the polymer microgel contains:

[0132] (i) at least one structured polymer, wherein the structured polymer is obtained by polymerizing monomers in a reverse microemulsion,

[0133] (ii) cement,

[0134] (iii) water, and

[0135] (iv) optionally at least one cement additive;

[0136] - Inject the cement-based composition into a borehole containing a casing, with an annular space formed between the casing and the borehole, so as to perform cementing through the casing and / or in the annular space around the casing and / or in the open hole under the casing.

[0137] As described above, compared with the prior art, one of the advantages of the present invention is that it can perform cementing without being affected by temperature, while ensuring good performance and without the risk of cracks.

[0138] After the microgel is injected into the borehole, it still exists in the form of particles. It does not dissolve and does not solubilize. It remains undissolved, and its size changes within the borehole by no more than 20% of the volume, preferably no more than 10% of the volume, and more preferably it does not change in the cement-based composition or in the borehole. For example, when the size of the microgel after preparation is 100 nm, its size in the cement-based composition and in the borehole does not exceed 120 nm, preferably does not exceed 110 nm, and more preferably remains 100 nm.

[0139] The microgel does not hydrolyze in the borehole.

[0140] Generally, the temperature in the borehole is at least 50 °C, preferably at least 70 °C, more preferably at least 90 °C, and even more preferably at least 100 °C.

[0141] The present invention and the above advantages will be better reflected from the following non-limiting examples given to illustrate the present invention. Examples

[0142] The following abbreviations used in the following examples are listed below:

[0143] AMD: acrylamide

[0144] ATBS: 2-acrylamido-2-methylpropanesulfonic acid

[0145] PVA: polyvinyl alcohol

[0146] SB rubber: styrene-butadiene rubber

[0147] MBA: methylenebisacrylamide

[0148] MBS: sodium metabisulfite

[0149] Synthesize polymer microgels by inverse emulsion polymerization

[0150] The aqueous phase is prepared from 680 g of ATBS.Na (sodium 2 - acrylamido - 2 - methylpropanesulfonate, 50% by weight in water), 0.2 g of MBA, and 0.2 g of Versenex 80.

[0151] The oil phase is prepared from 234.5 g of oil ( D100 S) and 25 g of tall oil fatty acid diethanolamine as a water - in - oil emulsifier.

[0152] While stirring, the aqueous phase is added to the oil phase to form an emulsion. With the temperature stabilized at 25 °C, nitrogen is bubbled through the resulting dispersion for 30 minutes, then 0.1 g of tert - butyl hydroperoxide is added to the emulsion, and a solution containing 0.75 g of MBS is added to the dispersion at a rate of 0.1 mL per minute. The polymerization reaction is carried out at a temperature of 38 °C to 42 °C for about 90 minutes. A solution containing 0.3 g of MBS is added at a flow rate of 1.0 mL per minute to capture residual monomers. A water - in - oil polymer emulsion is obtained, in which the weight content of polymer 1 is 20%.

[0153] 50 g of an oil - in - water emulsifier ( NP 8, nonylphenol ethoxylate and polyethylene glycol 8OE) is added to the water - in - oil polymer emulsion for use of the emulsion (percentage by weight relative to the weight of the inverse emulsion). The resulting water - in - oil polymer emulsion contains 34% (by weight) of polymer 1.

[0154] Polymer microgels are synthesized by precipitation polymerization

[0155] The reactor used for this polymerization reaction is a 2 L jacketed stirred vessel equipped with a distillation column, a pH probe, a thermometer, a powerful stirrer, a nitrogen bubbling nozzle, and an ammonia inlet.

[0156] First, 1570 g of pure tert - butanol (2 - methyl - 2 - propanol) and 65 g of water are added to the reactor. Then 112 g of acid ATBS is added under stirring. Then the monomer is completely neutralized by a gaseous ammonia stream flowing through the suspension until the pH value reaches 8. Then the ammonia gas supply is stopped, and 1.3 g of MBA is added. Then the solution is sprayed with nitrogen for one hour while raising the temperature to 55 °C.

[0157] When the temperature is stabilized at 55 °C, 1.6 g of benzoyl peroxide is added to the solution to initiate the reaction and precipitate the formed polymer. After the temperature stops rising, the solvent is evaporated under vacuum to directly obtain a dry powder, which is polymer 2.

[0158] Polymer microgels are synthesized by inverse microemulsion polymerization.

[0159] In a 1 L reactor, 440 g of ATBS (50 wt% in water) and 0.22 g of MBA were mixed. The pH of the solution was adjusted to 6.5 with a few drops of concentrated sulfuric acid. Then, 440 g of isoparaffinic oil, 12.3 g of sorbitan oleate, and 107.7 g of ethoxylated sorbitan hexoate were added. The mixture was then stirred until it became transparent and homogeneous. The stirring speed was maintained at 200 rpm for 25 minutes while degassing with nitrogen. Then, concentrated cumene hydroperoxide was added to the medium, followed by 1 ml of sodium metabisulfite (10 wt% in water). The mixture was placed under a nitrogen atmosphere for polymerization. The reaction was exothermic, and the temperature rose to 50 °C within 1 minute. After polymerization was complete, 0.2 g of MBS (40 wt% in water) was added to remove residual monomers. The resulting product was transparent and had a low viscosity (24 cP), corresponding to Polymer 3.

[0160] As shown in Table 2, using the same method, different polymers (4 - 7) were synthesized by changing different parameters (the composition and size of the polymer microgels).

[0161] Preparation of Cement - Based Compositions

[0162] The components listed in Table 1 were mixed in a 1 L capacity stirring bowl equipped with blades to prepare the cement - based composition. These components were added within 15 seconds at a rotational speed of 4000 rpm, and then stirred at 12000 rpm for 35 seconds.

[0163] A retarder (sodium lignosulfonate) and a dispersant (sodium naphthalene sulfonate) were used in formulating the slag cement.

[0164]

[0165] Table 1: Slag Cement Formulation (44% / cement means 44 weight parts per 100 weight parts of cement).

[0166] As described above, the Static Gel Strength Analyzer (SGSA) uses acoustic attenuation to evaluate the gelation process of cement slurries under specified temperature and pressure conditions. The device measures the static gel strength (SGS) and the compressibility as a function of time. In other words, the device can evaluate the gelation during the dehydration of the cement, which occurs after the cement slurry is placed in the well. At this stage, the aim is to ensure that the setting time is as short as possible to prevent gas migration through the cement column. The time between the start of gelation (when the SGS reaches 100 lb / 100 ft 2 ) and the end of the gas migration risk (exceeding 500 lb / 100 ft 2 ) must be less than 45 minutes. Therefore, the transition period measured in the following example was between 100 and 500 lb / 100 ft 2Between. When the setting time exceeds 60 minutes, the test stops.

[0167] The equipment used is of Chandler Engineering brand and can particularly measure the fluid transition period in the presence or absence of gas migration inhibitors.

[0168] The adjustment of the cement slurry lasts for 30 minutes at ambient temperature, 70 °C or 90 °C, with a pressure of 3,000 PSI applied. The formulation used is the same as in Table 1, and the weight percentage of the polymer component is 0.42%.

[0169]

[0170]

[0171] Table 2: Compositions (EMI: inverse emulsion; μ-EMI: inverse microemulsion; PP: precipitation) illustrating the invention (INV) or comparative tests (CE)

[0172] In Table 2, the particle size corresponds to the droplet size of the hydrophilic phase in the emulsion or microemulsion.

[0173] The structured polymers (polymers 3 - 4 and 6 - 7) and microgels obtained by the inverse microemulsion method have better properties than the polymers (polymers 1 and 2) obtained by another synthesis method. Compared with the microgels (polymers 4 and 6 compared to polymers 1 and 5) prepared from microemulsions with hydrophilic phase droplets exceeding 500 nm, they have a shorter transition period.

[0174] The concentration of the polymers of the present invention is greatly reduced. The amount of styrene - butadiene rubber must be multiplied by more than 7.5 times to obtain properties comparable to those of the microgels of the present invention (polymer 6 compared to comparative example CE6), while for polyvinyl alcohol latex compounds, it must be multiplied by more than 4.5 times (polymer 5 compared to comparative example CE7).

[0175] The polyvinyl alcohol latex compound shows insufficient properties even at high concentrations when the temperature exceeds 90 °C, while the microgels of the present invention are not affected by temperature.

Claims

1. A cement-based composition, which comprises - polymer microgels; - cement; - water; and - optionally at least one cement additive; Among them, The polymer microgels contain at least one polymer structured by at least one crosslinking agent, wherein the structured polymer is obtained by polymerization in an inverse microemulsion of at least one monomer, wherein the microemulsion comprises hydrophilic phase droplets with a size between 20 and 500 nm.

2. The cementitious composition according to claim 1, characterized in that, The structured polymer comprises at least one anionic monomer and optionally at least one nonionic monomer.

3. The cementitious composition according to claim 2, wherein At least one of the anionic monomers has a functional group selected from acrylic acid, maleic acid, fumaric acid, malonic acid, itaconic acid, allyl functional groups.

4. The cementitious composition according to claim 2, wherein The anionic monomer is 2-acrylamido-2-methylpropanesulfonic acid and / or its salt form.

5. The cement-based composition according to claim 3, characterized in that, The anionic monomer is 2-acrylamido-2-methylpropanesulfonic acid and / or its salt form.

6. The cementitious composition according to any one of claims 1 to 5, characterized in that, The structured polymer contains at least 30 mol% of at least one anionic monomer.

7. The cement-based composition according to claim 2, wherein The nonionic monomers are selected from the group consisting of acrylamide, methacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-hydroxymethylacrylamide, N-vinylformamide (NVF), N-vinylacetamide, N-vinylpyridine and N-vinylpyrrolidone (NVP), N-vinylimidazole, N-vinylcaprolactam, N-vinylsuccinimide, acryloylmorpholine (ACMO), acryloyl chloride, glycidyl methacrylate, glycerol methacrylate, diacetone acrylamide, hydroxyalkyl acrylates of C1-C3 alkyls, hydroxyalkyl methacrylates of C1-C3 alkyls, aminoalkyl acrylates of C1-C3 alkyls, aminoalkyl methacrylates of C1-C3 alkyls, thioalkyl acrylates of C1-C3 alkyls, thioalkyl methacrylates of C1-C3 alkyls, or combinations thereof.

8. The cementitious composition according to any one of claims 1 to 5, characterized in that, The crosslinking agent is a monomer having at least two unsaturated olefinic bonds.

9. The cement-based composition according to claim 6, wherein The crosslinking agent is a monomer having at least two unsaturated olefinic bonds.

10. The cement-based composition according to claim 7, characterized in that, The crosslinking agent is a monomer having at least two unsaturated olefinic bonds.

11. The cement-based composition according to any one of claims 1 to 5, characterized in that, The structured polymer contains less than 5% wt of the crosslinking agent relative to the weight of the monomer.

12. The cementitious composition according to claim 6, wherein, The structured polymer contains less than 5% wt of the crosslinking agent relative to the weight of the monomer.

13. The cementitious composition according to claim 8, characterized in that, The structured polymer contains less than 5% wt of the crosslinking agent relative to the weight of the monomer.

14. The cementitious composition according to claim 7 or 9 or 10, characterized in that, The structured polymer contains less than 5% wt of the crosslinking agent relative to the weight of the monomer.

15. The cementitious composition according to any one of claims 1 to 5, characterized in that, By weight, the cement-based composition contains 100 to 100,000 ppm of polymer microgels.

16. The cementitious composition according to claim 6, characterized in that, By weight, the cement-based composition contains 100 to 100,000 ppm of polymer microgels.

17. The cementitious composition according to claim 8, wherein By weight, the cement-based composition contains 100 to 100,000 ppm of polymer microgels.

18. The cementitious composition according to claim 7 or 9 or 10, characterized in that, By weight, the cement-based composition contains 100 to 100,000 ppm of polymer microgels.

19. The cement-based composition according to claim 11, characterized in that, By weight, the cement-based composition contains 100 to 100,000 ppm of polymer microgels.

20. The cement-based composition according to claim 12 or 13, characterized in that, By weight, the cement-based composition comprises from 100 to 100,000 ppm of polymer microgel.

21. The cementitious composition according to claim 14, wherein By weight, the cement-based composition comprises from 100 to 100,000 ppm of polymer microgel.

22. A well cementing process, comprising the steps of: - preparing a cement-based composition according to any one of claims 1 to 21; - injecting the cement-based composition into a borehole equipped with a casing, the casing defining an annular space between the casing and the borehole so as to perform well cementing through the casing and / or in the annular space around the casing and / or in the openings under the casing.

23. Use of a polymer microgel, characterized in that, For forming a cement-based composition, the polymer microgel comprises at least one polymer structured by at least one crosslinking agent; The structured polymer is obtained by polymerization in an inverse microemulsion of at least one monomer; wherein the microemulsion comprises hydrophilic phase droplets having a size between 20 and 500 nm.

24. A method for preparing a cement-based composition, characterized in that, The composition contains a mixture of the following compounds: - polymer microgel; - cement; - water; and - optionally at least one cement additive; wherein the polymer microgel contains at least one polymer structured by at least one crosslinking agent, wherein the structured polymer is obtained by polymerization in an inverse microemulsion of at least one monomer, wherein the microemulsion contains hydrophilic phase droplets having a size between 20 and 500 nm.

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