High-temperature suspension additive for well treatment

Abstract

The method may include preparing a well treatment fluid, the well treatment fluid comprising water and a high-temperature suspension additive comprising a monomer, a thermally unstable crosslinking agent having the property of hydrolyzing at temperatures above 250°F (121°C) in the well treatment fluid, and a polymer product of a thermally stable crosslinking agent having the property of being hydrolyzably maintained for at least about 1 hour at temperatures in the range of 250°F (121°C) to 450°F (232°C) in the well treatment fluid, and using the well treatment fluid to discharge fluid placed in the well.

Description

[Background technology]

[0001] During the drilling and finishing of oil and gas wells, various well treatments are performed on the well for several purposes. For example, wells are typically drilled down to the subsurface while circulating drilling fluid within the well. After drilling is complete, a pipe string, such as a casing, is inserted into the well. Then, usually, primary cementing is performed, in which a cementing fluid containing water, cement, and particulate additives is pressurized through the pipe string into the annulus between the pipe and the well wall, where the cementing fluid condenses to form an impermeable cement column, thereby sealing the annulus. Subsequently, secondary cementing operations, i.e., any cementing operations after primary cementing, may also be performed. One example of secondary cementing is squeeze cementing, in which cementing fluid is pressed under pressure into defects in the annulus, sealing those areas.

[0002] Various fluids are used in both well drilling and finishing, as well as in resource recovery. Examples of fluids include drilling fluid, also known as drilling slurry, which is pumped into the well during drilling and similar operations; spacers, which help flush out residual drilling fluid from the well; cement, which typically covers at least a portion of the completed well and is placed after the spacers have flushed out; and fracturing fluids, which are used to facilitate the recovery of oil or natural gas. While some wells are near the surface, most are deep underground in harsh environments. In addition, if something goes wrong with the downhole fluid, it can be difficult to detect or correct the problem, especially in the case of cement, which has set and is no longer fluid once set, because the fluid may be far from the surface and relatively difficult to access.

[0003] As the well-bottom circulation temperature rises, the viscosity of the cementing fluid decreases. This viscosity decrease is known as thermal viscosity reduction and can result in the sedimentation of solids in the slurry. Undesirable consequences of solid sedimentation include a density gradient in free water and settled cement. To suppress sedimentation, cement suspenders, such as crosslinked polymers, can be added to the cementing fluid. As the temperature of the cementing fluid rises, it is thought that cement suspenders maintain or increase the viscosity of the cementing fluid by, for example, cleaving at least some of the crosslinks to ensure that the polymer remains extended and provides a stable viscosity. One important characteristic of cement suspenders is that they do not adversely affect the rheology at low temperatures. Existing cement suspending additives, such as borate-crosslinked guar or guar derivatives, sufficiently delay crosslink cleavage, enabling the mixing and pumping of cementing fluids without imparting excessively high viscosity. However, these existing suspending additives are known to decompose above 280°F. This temperature limitation makes these cement suspension additives impractical for use in higher-temperature applications.

[0004] These drawings illustrate certain aspects of some embodiments of the present disclosure and should not be used to limit or define the present disclosure. [Brief explanation of the drawing]

[0005] [Figure 1] This is a schematic diagram of ground equipment used in the injection of spacer fluid and / or cement composition according to some embodiments of the present disclosure. [Figure 2] This is a schematic diagram illustrating an example in which a spacer fluid containing a high-temperature suspension additive is used between a cement composition and an excavation fluid. [Figure 3] This is a schematic diagram illustrating an example of a spacer fluid containing a high-temperature suspension additive being used in a borehole. [Figure 4]This graph shows the results of on-off-on thickening time tests for slurries according to some embodiments of the present disclosure. [Figure 5] This graph shows the results of on-off-on thickening time tests for slurries according to some embodiments of the present disclosure. [Figure 6] This is a graph of viscosity tests for slurries according to some embodiments of the present disclosure. [Figure 7] This is a graph of viscosity tests for slurries according to some embodiments of the present disclosure. [Figure 8] This is a graph of polymer entanglement testing according to some embodiments of the present disclosure. [Modes for carrying out the invention]

[0006] This disclosure relates to well treatment fluids containing high-temperature suspension additives. More specifically, high-temperature suspension additives may be included in well treatment fluids such as spacer fluids and cement slurries, where thermal viscosity reduction can occur. High-temperature suspension additives may be advantageous in that they provide solid suspensions in subsoil with bottom static temperatures (BHST) of approximately 280°F (138°C) or higher, including subsoil with bottom static temperatures exceeding approximately 400°F (204°C). The high-temperature suspension additives of this disclosure can operate at significantly higher temperatures than conventional biopolymer-based suspension additives such as guar gum and xanthan gum. The high-temperature suspension additives of this disclosure are even more advantageous than biopolymer-based suspension additives because they do not adversely affect the low-temperature viscosity of the treatment fluid and enable suspension at high temperatures in addition to miscibility at low temperatures.

[0007] In embodiments, the high-temperature suspension additive comprises a monomer, a thermally unstable crosslinking agent, and a reaction product of a thermally stable crosslinking agent. Examples of monomers include, but are not limited to, one or more monomers selected from groups including acrylamide (Ac), methacrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid and its salts, N-vinylpyrrolidone (NVP), N-substituted acrylamide, N-substituted methacrylamide, N-methylacrylamide, N-ethylacrylamide, N-vinylcaprolactam, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, acrylic acid, methacrylic acid, acrylates (such as methyl acrylate and hydroxyethyl acrylate), methacrylates (such as methyl methacrylate, 2-hydroxyethyl methacrylate, and 2-dimethylaminoethyl methacrylate), and combinations thereof.

[0008] The thermally unstable crosslinking agents for use in this disclosure may be crosslinking agents having at least two acrylamide groups, methacrylamide groups, acrylate groups, methacrylate groups, vinyl or vinylidene ester groups, allyl ester groups, or combinations thereof, which are hydrolyzably stable at room temperature and hydrolyzably unstable at high temperatures, i.e., above 250°F (121°C), over well treatment timescales, e.g., over a period of one hour or more. As used herein, “hydrolyzably stable” and its derivatives indicate stability against hydrolysis over a selected period at a selected temperature. Preferred thermally unstable crosslinking agents may be hydrolyzable at temperatures within the range of 250°F (121°C) to 550°F (288°C). Alternatively, a suitable thermally unstable crosslinking agent may be hydrolyzable at some point within the ranges of 250°F (121°C) to 350°F (177°C), 350°F (177°C) to 400°F (204°C), 400°F (204°C) to 500°F (260°C), 500°F (260°C) to 550°F (288°C), or any range between these ranges.

[0009] The thermally unstable crosslinking agents used in the methods and compositions of this disclosure generally include one or more crosslinking agents from among acrylamide crosslinking agents, acrylate crosslinking agents, ester crosslinking agents, amide crosslinking agents, any derivatives thereof, and any combination thereof. These crosslinking agents are stable at room temperature but hydrolyze at high temperatures, resulting in cleavage of the crosslinks. In certain embodiments, the acrylamide crosslinking agent may be a monomer having at least one acrylamide or methacrylamide group, which may also include additional unsaturated groups such as vinyl, allyl, and / or acetylene groups. In certain embodiments, the acrylate crosslinking agent may be a monomer having at least one acrylate or methacrylate group, which may also include additional unsaturated groups such as vinyl, allyl, and / or acetylene groups.

[0010] Examples of acrylamide-based crosslinking agents that may be suitable in certain embodiments of this disclosure include, but are not limited to, N,N'-methylenebisacrylamide, N,N'-methylenebismethacrylamide, N,N'-ethylenebisacrylamide, N,N'-propylenebisacrylamide, and their higher derivatives, N,N'-(1,2-dihydroxyethylene)bisacrylamide, 1,4-diacryoylpiperazine, N,N-diallylcrylamide, and 1,3,5-triacryloylhexahydro-1,3,5-triazine.

[0011] Examples of acrylate-based crosslinking agents that may be suitable in certain embodiments of this disclosure include, but are not limited to, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,1,1-trimethylolpropane trimethacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, glycerol di(meth)acrylate, glycerol tri(meth)acrylate, triglycerol di(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, and tris[2-(acryloyloxy)ethyl]isocyanurate.

[0012] Examples of ester-based and amide-based crosslinking agents that may be suitable in certain embodiments of this disclosure include, but are not limited to, vinyl or allyl esters such as diallyl carbonate, divinyl adipate, divinyl sebacate, N,N′-diallyl tartardiamide, diallyl phthalate, diallyl maleate, and diallyl succinate.

[0013] In some embodiments, the thermally stable crosslinker may be a crosslinker having at least two vinyl groups, vinylidene groups, or allyl groups, or a combination thereof, and this crosslinker is hydrolytically stable in the well treatment fluid at high temperatures such as above 250°F (121°C) up to about 450°F (232°C) over a well treatment timescale, e.g., over a period of one hour or more. For example, the thermally stable crosslinker may not hydrolyze at all, or may only partially hydrolyze, in which case less than about 10% of the crosslinks hydrolyze in the treatment fluid at temperatures in the range of 250°F (93°C) to 450°F (232°C) for at least about one hour. Alternatively, it could be 200°F (93°C) to 300°F (149°C), 300°F (149°C) to 400°F (204°C), 400°F (204°C) to 450°F (232°C), or any range between those ranges.

[0014] Thermally stable crosslinking agents are typically ether-based and not amide- or ester-based. Unlike amide- and ester-based crosslinking agents, these crosslinking agents are more resistant to thermal hydrolysis or may not even hydrolyze at high temperatures. Non-limiting examples of thermally stable crosslinking agents include divinyl ether, diallyl ether, vinyl or allyl ethers of polyglycols or polyols (such as pentaerythritol allyl ether (PAE), allyl sucrose, ethylene glycol divinyl ether, triethylene glycol divinyl ether, diethylene glycol divinyl ether, glycerol diallyl ether, and polyethylene glycol divinyl ether, propylene glycol divinyl ether, and trimethylolpropane diallyl ether, etc.), divinylbenzene, 1,3-divinylimidazolidin-2-one (also known as 1,3-divinylethyleneurea or divinylimidazolidone), divinyltetrahydropyrimidin-2(1H)-one, dienes (such as 1,7-octadiene and 1,9-decadiene), allylamine (such as triallylamine and tetraallylethylenediamine), N-vinyl-3(E)-ethylidenepyrrolidone, ethylidenebis(N-vinylpyrrolidone), triallyl isocyanurate (TTT), and any combination of the foregoing may be mentioned.

[0015] The high-temperature suspension additive may have a polymer complexation concentration (P*) in the range of 0.001 g / dL to 0.1 g / dL. Alternatively, it is in the range of 0.001 g / dL to 0.005 g / dL, 0.005 g / dL to 0.01 g / dL, 0.01 g / dL to 0.05 g / dL, 0.05 g / dL to 0.1 g / dL, or any range therebetween.

[0016] One or more monomers may be present in the high-temperature suspension additive in amounts ranging from 0.1 mol% to 99.9 mol%, or any range in between, such as 0.1 mol% to 1 mol%, mol% to 5 mol%, 5 mol% to 10 mol%, 10 mol% to 25 mol%, 25 mol% to 50 mol%, 50 mol% to 75 mol%, 75 mol% to 90 mol%, 90 mol% to 99 mol%, 99 mol% to 99.9 mol%, or any range in between. The high-temperature suspension additive may contain a combination of two or more monomers. If present, two or more monomers may be included in molar ratios ranging from approximately 0.1:99.9, 1:99, 5:95, 10:90, 20:80, 25:75, 30:70, 40:60, or 50:50 to approximately 99.9:0.1, 99:1, 90:10, 80:20, 75:25, 70:30, 60:40, or 50:50, where the amounts may range from any lower limit to any upper limit, encompassing any subset between the upper and lower limits, and any lower limit may be combined with any other lower limit to describe ranges not explicitly stated. In some embodiments, acrylamide and N-vinylpyrrolidone are present in molar ratios of 80:20, 60:40, 50:50, or 40:60. In some embodiments, acrylamide and 2-acrylamido-2-methyl-1-propanesulfonic acid are present in molar ratios of 80:20, 60:40, 50:50, or 40:60. In other embodiments, 2-acrylamido-2-methyl-1-propanesulfonic acid and N-vinylpyrrolidone are present in molar ratios of 80:20, 60:40, 50:50, or 40:60.

[0017] The high-temperature suspension additive may contain a thermally unstable crosslinking agent in an amount with a lower limit in the range of approximately 0.1 mol% to 20 mol%, or any range in between, such as 0.1 mol% to 1 mol%, 1 mol% to 2 mol%, 2 mol% to 3 mol%, 3 mol% to 4 mol%, 4 mol% to 5 mol%, 5 mol% to 10 mol%, 10 mol% to 15 mol%, 15 mol% to 20 mol%, or any range in between. In one or more embodiments, N,N'-methylenebisacrylamide (MBA) is present in an amount of 0.5 mol% to 10 mol%, or 1.5 mol% to 2.5 mol%, or 2 mol%, or 1 mol%.

[0018] The high-temperature suspension additive may include a thermally stable cross-linking agent in an amount having a lower limit of about 0.1 mol% to 20 mol%. Alternatively, it is in the range of 0.1 mol% to 1 mol%, 1 mol% to 2 mol%, 2 mol% to 3 mol%, 3 mol% to 4 mol%, 4 mol% to 5 mol%, 5 mol% to 10 mol%, 10 mol% to 15 mol%, 15 mol% to 20 mol%, or any range therebetween.

[0019] In one or more embodiments, triallyl isocyanurate (TTT) is present in an amount in the range of 0.5 mol% to 10 mol%, or 1 mol% to 5 mol%, or 2 mol% to 4 mol%. In embodiments, pentaerythritol allyl ether (PEAE) is present in an amount in the range of 0.5 mol% to 10 mol%, or 1 mol% to 5 mol%, or 2 mol% to 4 mol%. In some embodiments, triethyl glycol divinyl ether (TEGDVE) is present in an amount in the range of 0.5 mol% to 10 mol%, or 1 mol% to 5 mol%, or 2 mol% to 4 mol%.

[0020] In some embodiments, the high-temperature suspension additive can be used in wells and / or subterranean formations having a bottom hole static temperature (BHST) from a lower limit of about 275°F (135°C), 300°F (149°C), 325°F (163°C), 350°F (177°C), 400°F (204°C), or 450°F to an upper limit of about 550°F (288°C), about 500°F (260°C), about 450°F (232°C), or about 400°F (204°C), and the temperature can be in the range from any lower limit to any upper limit and can include any subset between the upper and lower limits.

[0021] Once partially hydrolyzed under well conditions, the high-temperature crosslinking agent may provide viscosity to the fluid, resulting in a viscosity ranging from approximately 5 bc (where bc is the viadan consistency unit measured with a pressurized consistency meter according to API RP-10B-2 Recommended Practice for Testing Well Cements, 1st edition published July 2005) to approximately 120 bc. Alternatively, it may be 5 bc to 10 bc, 10 bc to 25 bc, 25 bc to 50 bc, 50 bc to 75 bc, 75 bc to 100 bc, 100 bc to 120 bc, or any range in between. Alternatively, a fluid containing a hydrolyzed high-temperature suspension additive may have a viscosity ranging from approximately 100 cP (centipoise) to approximately 600 cP, as measured by a viscometer according to API RP-10B-2 Recommended Practice for Testing Well Cements, 1st edition published July 2005. Alternatively, it could be in the range of 100cP-200cP, 200cP-300cP, 300cP-400cP, 400cP-500cP, 500cP-600cP, or somewhere in between.

[0022] In embodiments, the cement slurry may comprise a high-temperature suspension additive, cement, and water. The high-temperature suspension additive may be used with any well cement, including hydraulic cements such as Portland cement, slag cement, pozzolan cement, gypsum cement, alumina cement, silica cement, high-alkaline cement, and any combination thereof, including API classes A, B, C, G, and H. Suitable waters may include fresh water, brine (e.g., water with one or more salts dissolved in it), scalding water (e.g., saturated brine), seawater, and any combination thereof. Generally, the water may come from any source and should not contain any components that could adversely affect the stability and / or performance of the composition or method of this disclosure. The cement slurry may contain the high-temperature suspension additive in any amount, such as 0.1% to 5% bwoc relative to the weight of the cement (bwoc). Alternatively, it could be in the range of 0.1%bwoc~0.5%bwoc, 0.5%bwoc~1%bwoc, 1%bwoc~2%bwoc, 2%bwoc~3%bwoc, 3%bwoc~5%bwoc, or in between.

[0023] The cement slurry may further contain any suitable additives, such as any suitable particulate matter. Suitable particulate matter for use in the present invention may be any particulate matter suitable for use in subsurface layers, and may include, but is not limited to, cementitious particulate matter, weighting agents, propane, fine aggregate particulate matter, and any combination thereof. Suitable particulate matter for use in the present invention may have a diameter ranging from a lower limit of about 0.5 μm, 1 μm, 10 μm, 50 μm, 0.1 mm, or 1 mm to an upper limit of about 10 mm, 1 mm, 0.5 mm, 0.1 mm, or 50 μm, and its diameter may range from any lower limit to any upper limit and may encompass any subset between the upper and lower limits. Particulate matter may be present in the processing fluid in amounts ranging from approximately 1%, 5%, 10%, 20%, 30%, 40%, or 50% of the weight of the processing fluid to approximately 99%, 90%, 80%, 70%, 60%, 50%, or 40% of the weight of the processing fluid, and the amount may be within the range of any lower limit to any upper limit, and may encompass any subset between the upper and lower limits.

[0024] Suitable weighting agents for use in this disclosure may be any known weighting agent that is particulate matter, including but not limited to barite, iron oxide, iron hematite carbonate, manganese tetroxide, galena, silica, siderite, celestite, ilmenite, dolomite, calcium carbonate, and any combination thereof. Suitable propanes for use in this disclosure may be any known propane, including but not limited to sand, bauxite, ceramic materials, glass materials, polymer materials, polytetrafluoroethylene materials, nut shells, curable resin particulate matter containing nut shells, seed shells, curable resin particulate matter containing seed shells, fruit kernels, curable resin particulate matter containing fruit kernels, wood, particulate composite materials, and any combination thereof. Suitable composite material particulate matter may include a binder and a filler, and suitable fillers include silica, alumina, fumed carbon, carbon black, graphite, mica, titanium dioxide, metasilicate, calcium silicate, kaolin, talc, zirconia, boron, fly ash, hollow glass microspheres, solid glass, and any combination thereof.

[0025] Suitable fine aggregate particulate materials for use in this disclosure include, but are not limited to, fly ash, silica powder, fine sand, diatomaceous earth, lightweight aggregates, hollow spheres, and any combination thereof.

[0026] In some embodiments, the high-temperature suspension additive may be contained in a first fluid placed in the well and / or sublayer before and / or after a second fluid, the second fluid comprising a plurality of particulate matter and the high-temperature suspension additive. In some embodiments, the concentration of the high-temperature suspension additive may differ between the first fluid and the second fluid. In some embodiments, the first fluid may be a spacer fluid and the second fluid may be a processing fluid.

[0027] In some examples, cement slurry may further contain lightweight additives. Lightweight additives may be included to reduce the density of the cement slurry. For example, lightweight additives may be used to form a lightweight cement slurry having a density of less than approximately 13 ppg. Lightweight additives typically have a specific gravity of less than approximately 2.0. Examples of suitable lightweight additives include sodium silicate, hollow microspheres, gilsonite, perlite, and combinations thereof. When used, lightweight additives may be present in amounts ranging from approximately 0.1% to approximately 20% relative to the weight of dry solids. In alternative examples, lightweight additives may be present in amounts ranging from approximately 1% to approximately 10% relative to the weight of dry solids.

[0028] Cement slurry should generally have a density suitable for its specific application. In some embodiments, the cement slurry is approximately 4 pounds per gallon ("lb / gal") (480 kg / m³). 3 ) ~ approx. 24lb / gal (2900kg / m 3 In other embodiments, the cement slurry may have a density in the range of 4 lb / gal (480 kg / m³). 3 ) ~ approx. 17lb / gal (2040kg / m 3 In yet another embodiment, the cement slurry may have a density in the range of ). 3 ) ~ approx. 13lb / gal (1600kg / m 3 ), approx. 13lb / gal (1600kg / m 3 The density can range from approximately 20 lb / gal (2396 kg / m³). In some examples, the cement slurry may be foamed and may contain water, high-temperature suspension additives, foaming agents, and gases. Optionally, to provide a cement slurry with a lower density and more stable foam, the foamed cement slurry may further contain, for example, lightweight additives. By using lightweight additives, a base slurry can be prepared and foamed to provide an even lower density. In some embodiments, the foaming spacer fluid is approximately 4 ppg (479 kg / m³). 3 ) ~ approx. 13ppg (1558kg / m3 ) Instead, it may have a density in the range of about 7 ppg (839 kg / m 3 ) to about 9 ppg (839 kg / m 3 ). In certain examples, the base slurry is from about 9 ppg (839 kg / m 3 ) to about 13 ppg (1558 kg / m 3 ) and can be foamed to a lower density, for example, in the range of about 7 ppg (839 kg / m 3 ) to about 9 ppg (839 kg / m 3 ).

[0029] The gas used in embodiments of the foamed cement slurry can be any gas suitable for foaming the cement slurry, including but not limited to air, nitrogen, and combinations thereof. Generally, the gas should be present in an amount sufficient to form the desired bubbles in an example of the foamed cement slurry. In certain embodiments, the gas can be present in an amount in the range of about 5% to about 80% by volume of the foaming spacer fluid at atmospheric pressure, alternatively, in the range of about 5% to about 55%, and alternatively, in the range of about 15% to about 30% by volume.

[0030] Where foaming occurs, the embodiments of cement slurry may include a foaming agent to provide suitable foam. As used herein, the term “foaming agent” refers to a material or combination of materials that promotes foam formation in a liquid. In embodiments of cement slurry, any suitable foaming agent for forming foam in an aqueous liquid may be used. Examples of suitable foaming agents include, but are not limited to, anionic, nonionic, amphoteric (including zwitterionic surfactants), cationic surfactants, or mixtures thereof; anionic surfactants such as betaine and hydrolyzed keratin; amine oxides such as alkyl or alkene dimethylamine oxide; alkyl or alkene amide betaine such as cocoamidopropyl dimethylamine oxide, methyl ester sulfonate, and cocoamidopropyl betaine; quaternary surfactants such as alpha-olefin sulfonate, trimethyl taloammonium chloride and trimethyl cocoammonium chloride; C8-C22 alkyl ethoxylate sulfates; and combinations thereof. Specific examples of suitable foaming additives include, but are not limited to, mixtures of ammonium salts of alkyl ether sulfates, cocoamidopropyl betaine surfactants, cocoamidopropyl dimethylamine oxide surfactants, sodium chloride, and water; mixtures of ammonium salts of alkyl ether sulfate surfactants, cocoamidopropyl hydroxysultaine surfactants, cocoamidopropyl dimethylamine oxide surfactants, sodium chloride, and water; hydrolyzed keratin, ethoxylated alcohol ether sulfate surfactants, alkyl or alkeneamidopropyl betaine surfactants, and mixtures of alkyl or alkene dimethylamine oxide surfactants; aqueous solutions of alpha-olefin sulfonate surfactants and betaine surfactants; mixtures of ammonium salts of alkyl ether sulfates; and combinations thereof. Generally, in embodiments for foamed cement slurry, the foaming agent may be present in an amount sufficient to provide suitable foam. In some embodiments, the foaming agent may be present in an amount ranging from about 0.8% to about 5% by volume % of water ("bvow").

[0031] The cement slurry may contain natural pozzolans such as fly ash, silica fume, or metakaolin, or combinations thereof. A suitable example of a pozzolan is fly ash. Various types of fly ash may be suitable, including those classified as Class C and Class F fly ash according to the American Petroleum Institute's API Specification for Materials and Testing for Well Cements, API Specification 10, 5th edition, July 1, 1990. Class C fly ash contains both silica and lime and can therefore coagulate and form solidified lumps when mixed with water. Generally, Class F fly ash does not contain enough lime to induce a cementitious reaction; therefore, embodiments for agglomerating cement slurry containing Class F fly ash require an additional source of calcium ions. In some examples, lime may be mixed with Class F fly ash in an amount ranging from about 0.1% to about 100% relative to the weight of the fly ash. In some cases, lime may be slaked lime. A suitable example of a pozzolanc is metakaolin. Generally, metakaolin is a white pozzolanc and can be prepared by heating kaolin clay to a temperature in the range of about 600°C to about 800°C. When used, metakaolin may be present in an amount ranging from about 0.1% to about 40% of the weight of the cement slurry. For example, metakaolin may be present in an amount in the range of about 0.1%, 10%, about 20%, about 30%, or about 40% of the weight of the cement slurry, and / or an amount including any of these. Additional examples of suitable pozzolancs include natural pozzolancs. Natural pozzolancs generally exist on the surface of the earth and set and solidify in the presence of slaked lime and water. Examples of natural pozzolancs include natural glass, diatomaceous earth, volcanic ash, opaline shale, tuff, and combinations thereof. Natural pozzolanic oil can be crushed or not.

[0032] The cement slurry may further contain slaked lime. As used herein, the term “slaked lime” should be understood to mean calcium hydroxide. In some examples, slaked lime may be provided as quicklime (calcium oxide), which, when mixed with water, hydrates to form slaked lime. Slaked lime may be included, for example, in embodiments for the agglomeration of spacer fluids, to form a hydraulic composition together with high-temperature suspension additives. For example, slaked lime may be included in a weight ratio of pozzolann to slaked lime of about 10:1 to about 1:1, or about 3:1 to about 5:1. If present, slaked lime may be included in the cement slurry in an amount at a single point ranging from about 1% to about 40% of the weight of the cement slurry, for example. In some examples, slaked lime may be present in an amount ranging from and / or including any of the following: about 1%, about 10%, about 20%, about 30%, or about 40% of the weight of the cement slurry.

[0033] In some examples of cement slurries, in addition to high-temperature suspension additives, a silica source, such as crystalline silica and / or amorphous silica, may be included. Amorphous silica is a powder that may be included in examples of cement slurries as a lightweight filler. Amorphous silica is generally a byproduct of the ferrosilicon manufacturing process, in which case amorphous silica may be formed by the oxidation and condensation of gaseous silicon dioxide, SiO, which is formed as an intermediate during the process. In examples including an additional silica source, the additional silica source may be utilized as needed, and in embodiments for agglomeration of the cementing slurry, it may improve the compressive strength or setting time.

[0034] In the example of cement slurry solidification, the cement slurry may solidify to form a mass that resists deformation. Examples of cement slurry solidification may include water, high-temperature suspension additives, and sources of calcium ions and hydroxide ions, such as lime. Generally, pozzolanes can participate in the pozzolanic reaction through the reaction of the silicon and / or aluminum components of the pozzolanes with calcium ions and hydroxide ions in water. The pozzolanic reaction can cause the cement slurry to develop compressive strength. Compressive strength is generally the ability of a material or structure to withstand axially applied compressive forces. Compressive strength can be measured according to the techniques described in the second edition of API RP-10B-2 Recommended Practice for Testing Well Cements, published in April 2013. Compressive strength is generally measured at a predetermined time after the cement slurry is prepared, and the resulting composition is maintained under predetermined temperature and pressure conditions. Compressive strength can be measured by either a destructive or non-destructive method. The destructive method physically tests the strength of the solidified cement slurry at various points in time by crushing the sample in a compression testing machine. Compressive strength is calculated by dividing the breaking load by the cross-sectional area that can withstand the load and is reported in pounds per square inch (psi). For the non-destructive method, the USA™ Ultrasonic Cement Analyzer, available from Fann™ Instrument Company (Houston, Texas), may be used. Compressive strength values ​​may be determined according to the API RP-10B-2 Recommended Practice for Testing Well Cements, 2nd edition, published April 2013.

[0035] For example, embodiments for the agglomeration of cement slurry can achieve 24-hour compressive strengths in the range of approximately 10 psi to approximately 2000 psi, alternatively, approximately 10 psi to approximately 100 psi, alternatively, approximately 100 psi to approximately 1000 psi, alternatively, approximately 1000 psi to approximately 1500 psi, or alternatively, approximately 1500 psi to approximately 2000 psi. In some examples, the compressive strength value can be determined using a destructive or non-destructive method at a temperature in the range of 100°F to 200°F.

[0036] Cement slurry may contain kiln dust. As used herein, “kiln dust” refers to a solid substance that is produced as a by-product when certain materials are heated in a kiln. As used herein, the term “kiln dust” is intended to include kiln dust manufactured as described herein and equivalent forms of kiln dust. Depending on its source, kiln dust may exhibit cementitious properties in that it can set or solidify in the presence of water. Examples of suitable kiln dust include cement kiln dust, lime kiln dust, and combinations thereof. Cement kiln dust may be produced as a by-product of cement production, which is removed and recovered from the gas stream, for example, in a dust collector. Typically, large amounts of cement kiln dust are recovered in cement production and generally disposed of as waste. Chemical analysis of cement kiln dust from various cement manufacturers varies depending on many factors, including the specific kiln feed, the efficiency of the cement production operation, and the associated dust collection system. Cement kiln dust can generally contain various oxides such as SiO2, A12O3, Fe2O3, CaO, MgO, SO3, Na2O, and K2O. Disposal of lime kiln dust can also be problematic, as it can be produced as a by-product of lime calcination. Chemical analysis of lime kiln dust from various lime manufacturers varies depending on several factors, including the supply of specific limestone or dolomitic limestone, the type of kiln, the kiln's operation, the efficiency of the lime production process, and the associated dust collection system. Lime kiln dust can generally contain varying amounts of free lime and free magnesium, limestone, and / or dolomitic limestone, as well as various oxides such as SiO2, A12O3, Fe2O3, CaO, MgO, SO3, Na2O, and K2O, and other components such as chlorides.

[0037] The cement slurry may further contain barite. In some cases, barite may be present in the cement slurry in amounts ranging from about 1% to about 60% (e.g., about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, etc.) relative to the weight of the cement slurry. In some cases, barite may be present in the cement slurry in amounts ranging from about 1% to about 35% relative to the weight of the cement slurry. In some cases, barite may be present in the cement slurry in amounts ranging from about 1% to about 10% relative to the weight of the cement slurry. Alternatively, the amount of barite may be expressed in terms of the weight of dry solids. For example, barite may be present in amounts ranging from approximately 1% to approximately 99% (e.g., approximately 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 99%, etc.) relative to the weight of dry solids. In some examples, barite may be present in amounts ranging from approximately 1% to approximately 20% and, alternatively, approximately 1% to approximately 10% relative to the weight of dry solids.

[0038] In some embodiments, the cement slurry may further contain one or more of slag, perlite, shale, amorphous silica, or metakaolin. These additives may be included in the cement slurry to improve one or more properties of the cement slurry. The cement slurry may further contain slag. Slag is generally a granular blast furnace by-product resulting from the production of cast iron containing oxidized impurities found in iron ore. When used, slag may be present in an amount ranging from about 0.1% to about 40% of the weight of the cement slurry. The cement slurry may further contain perlite. Perlite is an ore and generally refers to naturally occurring volcanic amorphous siliceous rock containing primarily silicon dioxide and aluminum oxide. Perlite may be expanded and / or unexpanded to suit specific applications. Expanded or unexpanded perlite may also be crushed, for example. When used, perlite may be present in an amount ranging from about 0.1% to about 40% of the weight of the cement slurry. For example, perlite may be present in amounts ranging from about 0.1%, 10%, 20%, 30%, or 40% of the weight of the cement slurry, and / or in amounts including any of these. The cement slurry may also contain shale. Various types of shale are suitable, including those containing silicon, aluminum, calcium, and / or magnesium. Examples of suitable shale include vitrified shale and / or calcined shale. When used, shale may be present in amounts ranging from about 0.1% to about 40% of the weight of the cement slurry. For example, shale may be present in amounts ranging from about 0.1% by weight, 10% by weight, 20% by weight, 30% by weight, or 40% by weight, and / or in amounts including any of these.

[0039] The cement slurry may further contain a free water control additive. As used herein, the term “free water control additive” refers, among other things, to an additive contained in a liquid to reduce or prevent the presence of free water in the liquid. Free water control additives may also reduce or prevent the settling of solids. Examples of suitable free water control additives include, but are not limited to, bentonite, amorphous silica, hydroxyethyl cellulose, and combinations thereof. In some embodiments, the free water control additive may be provided as a dry solid. When used, the free water control additive may be present, for example, in an amount ranging from about 0.1% to about 16% based on the weight of the dry solids. In alternative embodiments, the free water control additive may be present in an amount ranging from about 0.1% to about 2% based on the weight of the dry solids.

[0040] Optionally, fluid loss-reducing additives may be included in the cement slurry to reduce, for example, the amount of fluid lost into the subsurface. Examples of suitable fluid loss-reducing additives include, but are not limited to, certain polymers such as hydroxyethylcellulose and carboxymethylhydroxyethylcellulose, copolymers of 2-acrylamido-2-methylpropanesulfonic acid with acrylamide or N,N-dimethylacrylamide, and graft copolymers comprising a lignin or lignite main chain and a pendant group containing at least one group selected from the group including 2-acrylamido-2-methylpropanesulfonic acid, acrylonitrile, and N,N-dimethylacrylamide.

[0041] Optionally, cement slurry may contain sludge inhibitors, for example, to help prevent fluid circulation from being lost into subsurface layers. Examples of sludge inhibitors include, but are not limited to, cedar bark, shredded sugarcane stalks, mineral fibers, mica flakes, cellophane, calcium carbonate, crushed rubber, polymer materials, plastic fragments, crushed marble, wood, nut shells, formica, corn cobs, cotton husks, and combinations thereof.

[0042] Optionally, setting accelerators may be included in the cement slurry to increase the setting reaction rate. Controlling the setting time may allow for adjustment of the wellhead condition or customization of the setting time to suit individual operations. Suitable setting accelerators may include, but are not limited to, aluminum sulfate, alum, calcium chloride, calcium sulfate, hemihydrate gypsum, sodium aluminate, sodium carbonate, sodium chloride, sodium silicate, sodium sulfate, ferric chloride, or combinations thereof.

[0043] Optionally, setting retarders may be included in the cement slurry agglomeration method, for example, to extend the thickening time of the cement slurry. Suitable setting retarders include, but are not limited to, ammonium, alkali metals, alkaline earth metals, borax, metal salts of calcium lignosulfonates, carboxymethyl hydroxyethyl cellulose, sulfoalkylated lignin, hydroxycarboxylic acids, mixtures of 5-chloro-2-methyl-3(2H)-isothiazolone and 2-methyl-3(2H)-isothiazolone, copolymers of 2-acrylamido-2-methylpropanesulfonate and acrylic acid or maleic acid, saturated salts, or combinations thereof. A suitable example of sulfoalkylated lignin is sulfomethylated lignin.

[0044] As mentioned above, cement slurry can solidify after being injected into a well. For example, cement slurry can develop gel strength and / or compressive strength when deposited in a well. As a specific example of solidification, when deposited in the well annulus (e.g., between a subsurface and a pipe string located within the subsurface, or between a pipe string and a larger conduit located within the subsurface), cement slurry can solidify and develop static gel strength and / or compressive strength. The solidified mass formed in the well annulus can support and position the pipe string within the well and adhere the pipe string's surface to the well wall or the larger conduit. The solidified mass formed in the well annulus can also provide a substantially impermeable barrier, blocking formation fluids and gases and consequently mitigating potential fluid movement. The solidified mass formed in the well annulus can further protect the pipe string or other conduits from corrosion.

[0045] The cement slurry can be prepared according to any preferred technique. In some examples, a desired amount of water may be added to a mixer (e.g., a cement blender), followed by a dry mixture of spacer fluid components. The dry mixture may contain high-temperature suspension additives and additional solid additives as described above. If additional liquid additives are present, they may be added to the water as desired, either before or after mixing with the dry mixture. The mixture may be stirred for a sufficient amount of time to form a pumpable slurry. As an example, this pumpable slurry may be delivered into the well using a pump.

[0046] In some embodiments, the high-temperature suspension additive may be provided in a wet or dry state. In some embodiments, the high-temperature suspension additive may be added to the treatment fluid in-situ or out-of-situ at the well site.

[0047] The components of a cement composition can be combined in any desired order to form a cement composition that can be introduced into a subsurface. In addition, the components of a cement composition can be combined using any mixing device suitable for the composition, including, for example, a bulk mixer. In a particular example, a cement composition may be prepared, for example, by dry mixing the solid components of the cement composition in a bulk plant, and then combining this dry mixture with water at the desired time of use. For example, a dry mixture containing high-temperature suspension additives and other dry cement components may be prepared. Liquid additives (if any) may be combined with water before the water is combined with the dry components, or added directly to the mixer tank. In some examples, a jet mixer may be used to continuously mix, for example, a dry mixture containing a cement composition with water as it is pumped, for example, into a well.

[0048] In some cases, high-temperature suspension additives may be included in the spacer fluid. Spacers, also called displacement fluids, washing fluids, or inverter fluids, are introduced into the well after drilling and before cementing. Spacers prepare the well to receive cement. For example, spacers can completely drain the drilling fluid from the well annulus and / or prepare the casing and well surface to bond with the cement. Drilling fluid can contaminate the cement, which can ultimately cause problems such as mismatch and poor bonding, in addition to suppression of compressive strength development. The presence of a filtration cake of drilling fluid on the casing can affect the bonding between the casing and cement and cause the formation of microchannels. Therefore, spacers often remove any cake from the drilling fluid and wet the casing and annulus with water to receive cement. Spacer fluids may include water and high-temperature suspension additives. Spacer fluids can be prepared by mixing a spacer dry mixture containing high-temperature suspension additives with water. Spacer dry mixtures may include high-temperature suspension additives and other dry components for specific applications. In the example, the spacer fluid may contain any amount of high-temperature suspension additive, ranging from 0.01% bwob (relative to the weight of the spacer dry mixture) to 50% bwob. Alternatively, it may be in the range of 0.01% bwob to 0.05% bwob, 0.05% bwob to 0.1% bwob, 0.1% bwob to 0.5% bwob, 0.5% bwob to 1% bwob, 1% bwob to 2% bwob, 2% bwob to 3% bwob, 3% bwob to 5% bwob, 5% bwob to 15% bwob, 15% bwob to 25% bwob, 25% bwob to 50% bwob, or any range in between.

[0049] To be effective, a spacer can possess certain properties. For example, a spacer can be compatible with the discharged fluid and cement. This compatibility can also exist in terms of temperature and pressure within the downhole. In some cases, it is desirable for the spacer to wet the surface within the well, thereby promoting bonding with the cement. In spacer design, several different rheological properties can be important, including yield point, plastic viscosity, gel strength, and shear stress. While rheology can be important in spacer design, conventional spacers may not have the desired rheology at the temperatures within the downhole. For example, conventional spacers may experience an undesirable viscosity reduction at high temperatures. As a result, conventional spacers may not provide the desired substitution in some cases, and may lead to insufficient suspension in others.

[0050] In some examples, the spacer dry mixture may contain a solid refining agent, for example, to scrape off and facilitate the removal of solid filtration cake from the well surface. Suitable solid refining agents include, but are not limited to, pumice, perlite, other volcanic glass, fumed silica, and fly ash. The solid refining agent may be present in the spacer dry mixture in any suitable amount, ranging from about 1% bwob to about 99.9% bwob, but is not limited to this amount. In specific embodiments, the solid refining agent may be present in amounts ranging from about 1% bwob to 25% bwob, 25% bwob to 50% bwob, 50% bwob to 75% bwob, 90% to about 99%, or any range in between.

[0051] In some cases, the spacer dry mixture may contain a biopolymer gum. Examples of suitable biopolymer gums include, but are not limited to, polysaccharides such as xanthan gum, dieutan gum, welan gum, scleroglucan gum, and combinations thereof. The biopolymer gum may be present in the spacer dry mixture in any suitable amount, including, but not limited to, amounts from 0.01% bwob (relative to the weight of the spacer dry mixture) to 5% bwob. Alternatively, it may be in the range of 0.01% bwob to 0.05% bwob, 0.05% bwob to 0.1% bwob, 0.1% bwob to 0.5% bwob, 0.5% bwob to 1% bwob, 1% bwob to 2% bwob, 2% bwob to 3% bwob, 3% bwob to 5% bwob, or any range in between.

[0052] The spacer fluid may further contain surfactants. These may include any of a variety of surfactants capable of wetting well surfaces, such as well walls and casing surfaces (e.g., water-wetting or oil-wetting). In some embodiments, the spacer fluid may contain both water-wetting and oil-wetting surfactants. Examples of suitable wetting surfactants include alcohol ethoxylates, alcohol ethoxysulfates, alkylphenol ethoxylates (e.g., nonylphenol ethoxylate), glycol ethers, and combinations thereof. Certain wetting surfactants may be used as water-soluble salts. For example, the wetting surfactant may be selected from alkali metals, alkaline earth metals, ammonium, and alkanolammonium salts of alcohol ethoxylates, alcohol ethoxysulfates, and alkylphenol ethoxylates. This surfactant may be present in any suitable amount in the spacer dry mixture, ranging from 0.01% bwob (relative to the weight of the spacer dry mixture) to 5% bwob by weight, but is not limited to these amounts. Alternatively, it could be any of the following ranges: 0.01%bwob to 0.05%bwob, 0.05%bwob to 0.1%bwob, 0.1%bwob to 0.5%bwob, 0.5%bwob to 1%bwob, 1%bwob to 2%bwob, 2%bwob to 3%bwob, 3%bwob to 5%bwob, or any of these ranges.

[0053] The spacer fluid may further contain a dispersant. Suitable dispersants may include, but are not limited to, any of the various commonly used cement dispersants, such as sulfonated dispersants, sulfonated polymer dispersants, naphthalene sulfonates, melamine sulfonates, sulfonated melamine formaldehyde condensates, sulfonated naphthalene formaldehyde condensates, sulfonated acetone formaldehyde condensates, ethoxylated polyacrylates, or combinations thereof. The dispersant may be present in the spacer dry mixture in any suitable amount, ranging from 0.01% bwob (relative to the weight of the spacer dry mixture) to 5% bwob, but is not limited to these amounts. Alternatively, it could be any of the following ranges: 0.01%bwob to 0.05%bwob, 0.05%bwob to 0.1%bwob, 0.1%bwob to 0.5%bwob, 0.5%bwob to 1%bwob, 1%bwob to 2%bwob, 2%bwob to 3%bwob, 3%bwob to 5%bwob, or any of these ranges.

[0054] The spacer fluid may further contain a weighting agent. For example, the weighting agent may be included in the spacer dry mixture to impart a desired density to the spacer fluid. Examples of suitable weighting agents include, for example, barite, manganese tetroxide, iron oxide, calcium carbonate, and iron carbonate. The weighting agent may be included in any suitable amount, including, but not limited to, about 1% bwob to about 99% bwob, about 50% bwob to about 99% bwob, or about 75% bwob to about 99% bwob, based on the total weight of the spacer dry mixture.

[0055] Spacer fluids should generally have a density suitable for their specific application. In some embodiments, the spacer fluid has a density of approximately 4 pounds per gallon ("lb / gal") (480 kg / m³). 3 ) ~ approx. 24lb / gal (2900kg / m 3 The density may be in the range of ). In other embodiments, the spacer fluid may be about 4 lb / gal (480 kg / m³). 3 ) ~ approx. 17lb / gal (2040kg / m 3The density can be in the range of ). In yet another embodiment, the spacer fluid may be about 8 lb / gal (960 kg / m³). 3 ) ~ approx. 13lb / gal (1600kg / m 3 ), approx. 13lb / gal (1600kg / m 3 The density may range from approximately 20 lb / gal (2396 kg / m³). Embodiments of the spacer fluid may be foamed or non-foamed, or may include other means known in the art for reducing density, such as lightweight additives. Those skilled in the art who benefit from this disclosure will recognize an appropriate density for a particular application.

[0056] As previously mentioned, the spacer dry mixture can be mixed with water to form a spacer fluid, which can then be injected into the well. The water used in one embodiment of the spacer fluid may include, for example, fresh water, brine (e.g., water containing one or more salts dissolved in it), brackish water, seawater, or any combination thereof. In general, the water may come from any source, as long as it does not contain in excess compounds that could have an undesirable effect on the other components in the spacer fluid. The water is included in an amount sufficient to form a pumpable spacer fluid. In some embodiments, water may be included in the spacer fluid in an amount ranging from about 15% to about 95% by weight, based on the total weight of the spacer fluid. In other embodiments, water may be included in the spacer fluid in an amount ranging from about 25% to about 85% by weight or about 50% to about 75% by weight, based on the total weight of the spacer fluid. The spacer dry mixture may be included in the spacer fluid in any suitable amount, based on the total weight of the spacer fluid, including about 5% to about 50% by weight, about 10% to about 60% by weight, or about 20% to about 50% by weight.

[0057] A suitable spacer fluid can be prepared according to any suitable technique. A desired amount of water may be added to a mixer (e.g., a cement blender), followed by the dry spacer mixture, but is not limited thereto. If additional liquid and / or dry additives are present, they may be added to the water as desired, either before or after mixing with the dry mixture. The mixture may be stirred for a sufficient amount of time to form a pumpable slurry. As an example, this pumpable slurry may be delivered into the well using a pump. As is understood, the spacer fluid and / or dry spacer mixture may be prepared at the well site or prepared off-site and then transported to the well site. If prepared off-site, the dry spacer mixture and / or spacer fluid may be transported to the well site using any suitable means of transport, including but not limited to trucks, railcars, or barges. Alternatively, the spacer fluid and / or spacer dry mixture may be prepared at the well site, for example, by supplying the components of the spacer fluid and / or spacer dry mixture from a means of transport (e.g., a vehicle or pipeline) and then mixing them before injection into the downhole. As will be understood by those skilled in the art, other suitable techniques for preparing the spacer fluid may be used in accordance with embodiments, in the interest of the present disclosure.

[0058] The spacer may have sufficient viscosity at surface temperature and pressure to suspend any particulate additive, such as barite, while being able to be pumped into the downhole. Within the well, the spacer may maintain sufficient viscosity to suspend any particulate additive, while still being able to circulate through the well and be discharged from the well. The spacer may further maintain sufficient viscosity upon returning to surface pressure or surface temperature to allow for discharge from the well. The spacer may further maintain its viscosity, thereby allowing it to continue suspending any particulate additive, such as barite, through any cleaning or testing processes, or until it reaches a retention tank, where applicable, or is returned to the well.

[0059] Exemplary methods may include methods for discharging a first fluid from a well penetrating a subsurface layer. This method may include providing a spacer fluid containing a high-temperature suspension additive and water. As discussed herein, one or more additives may also be included in the spacer fluid. The method may further include introducing the spacer fluid into the well to discharge at least a portion of the first fluid from the well. In some examples, the spacer fluid may discharge the first fluid from a well annulus, such as an annulus between a pipestring and a subsurface layer, or an annulus between a pipestring and a larger conduit. In some examples, the first fluid discharged by the spacer fluid includes drilling fluid. For example, the spacer fluid may be used to discharge drilling fluid from a well. In addition to discharging drilling fluid from a well, the spacer fluid can also remove drilling fluid from the well wall. In one embodiment, an additional step in the example of this method may include introducing a pipe string into the well and introducing the cement composition into the well using a spacer fluid that separates the cement composition from the first fluid, thereby allowing the cement composition to set in the well. The cement composition may include, for example, cement, a high-temperature suspension additive, and water.

[0060] Figure 1 shows an exemplary ground installation 10 that may be used for injecting spacer fluid and / or cement composition. While Figure 1 generally illustrates onshore operations, it should be noted that the principles described herein are equally applicable to underwater operations employing floating or offshore platforms and rigs without departing from the scope of this disclosure. As shown in Figure 1, the ground installation 10 may include a cementing device 12, which may include one or more cement trucks. The cementing device 12 may comprise a mixing device 4 and a pumping device 6. The cementing device 12 can pump the spacer fluid and / or cement composition through a supply pipe 16 in the direction indicated by the arrow 14, and also pump this fluid to a cementing head 18 that transports it into the downhole. Any embodiment of the spacer fluid described herein may be applied with respect to the spacer fluid in the situation shown in Figure 1. For example, the spacer fluid may include a high-temperature suspension additive, water, and one or more optional additives.

[0061] Here, an example of the use of the spacer fluid 20, including a high-temperature suspension additive, is described with reference to Figure 2. Any embodiment of the spacer fluid described herein may be applied to the spacer fluid 20 in the situation shown in Figure 2. For example, the spacer fluid 20 may include a high-temperature suspension additive, water, and one or more optional additives. Figure 2 depicts one or more subsurface layers 22 penetrated by a well 24, in which a drilling fluid 26 is placed. The drilling fluid 26 may include exemplary drilling fluids disclosed herein. Although the well 24 is shown extending substantially vertically through one or more subsurface layers 22, the principles described herein are also applicable to wells that extend diagonally through one or more subsurface layers 22, such as horizontal wells and inclined wells. As shown, the well 24 comprises a wall 28. In the illustrated embodiment, a surface casing 30 is cemented to the wall 28 of the well 24 by a cement sheath 32. In the illustrated embodiment, one or more additional conduits (e.g., intermediate casing, production casing, liner, etc.) are shown here as casing 34 and may also be located within the well 24. As shown, a well annulus 36 is formed between casing 34 and the wall 28 of the well 24 (and / or surface casing 30). Although not shown, one or more centralizers may be attached to the surface casing 30 to center casing 34 within the well 24, for example, before and during cementing operations.

[0062] As illustrated, a cement composition 38 containing a high-temperature suspension additive can be introduced into the well 24. For example, the cement composition 38 can be pumped downward through the casing 34. The pump 6 shown in Figure 1 may be used to introduce the cement composition 38 containing the high-temperature suspension additive into the well 24. It may also be desirable to circulate the cement composition 38 within the well 24 until it enters the well annulus 36. The cement composition 38 may include the exemplary cement compositions disclosed herein. Although not illustrated, other techniques may also be used for introducing the cement composition 38. For example, a reverse circulation technique may be used, which involves introducing the cement composition 38 into the well 24 via the well annulus 36 instead of through the casing 34.

[0063] The drilling fluid 26 can be separated from the cement composition 38 containing the high-temperature suspension additive using a spacer fluid 20 containing a high-temperature suspension additive. The spacer fluid 20 can be introduced into the well 24 using the previous embodiment described with reference to Figure 1 for the preparation of the spacer fluid. Furthermore, the spacer fluid 20 can be introduced into the well 24 using the pump 6 shown in Figure 1. The spacer fluid 20 can be used together with the cement composition 38 to prepare the well 24 for the cement composition 38, in addition to discharging the drilling fluid 26 from the well 24. For example, the spacer fluid 20 may function to remove the drilling fluid 26, dewatered / gelled drilling fluid 26, and / or filtered cake solids from the well 24 prior to the cement composition 38. Although not shown, the drilling fluid 26 can be physically separated from the spacer fluid 20 and / or the spacer fluid 20 from the cement composition 38 using one or more plugs or other suitable devices.

[0064] Referring now to Figure 3, the drilling fluid 26 is discharged from the well annulus 36 according to a particular embodiment. As illustrated, the spacer fluid 20 containing a high-temperature suspension additive and the cement composition 38 containing a high-temperature suspension additive may flow down through the bottom of the casing 34 (e.g., the casing shoe 40), up around the casing 34, and into the well annulus 36, thus discharging the drilling fluid 26. At least a portion of the discharged drilling fluid 26 is discharged from the well annulus 36 via the channel 42 and may accumulate, for example, in one or more retaining pits 44 (e.g., mud pits), as shown in Figure 1. Returning to Figure 3, the cement composition 38 may continue to circulate until it reaches a desired location within the well annulus 36. The spacer fluid 20 and / or cement composition 38 may remain in the well annulus 36. As illustrated, the spacer fluid 20 may be located in the well annulus 36 above or above the cement composition 38. The cement composition 38 may set within the well annular 36 to form a solidified, substantially impermeable annular sheath (i.e., cement sheath) of material capable of supporting and positioning the casing 34 within the well 24. As previously stated, embodiments of the spacer fluid 20 may solidify within the well annular 36. Thus, the spacer fluid 20 may help stabilize the casing 34 and also serve to provide a barrier that protects a portion of the casing 34 from the corrosive effects of water and / or aqueous drilling fluids that would otherwise remain in the well annular 36 above the cement composition 38.

[0065] Exemplary cement compositions comprising high-temperature suspension additives disclosed herein may directly or indirectly affect one or more components or equipment related to the preparation, delivery, recovery, recycling, reuse, and / or disposal of the cement composition and related cement compositions. For example, the cement composition may directly or indirectly affect one or more mixers, associated mixing equipment, mud pits, storage facilities or equipment, composition separators, heat exchangers, sensors, gauges, pumps, and compressors, etc., used to produce, store, monitor, adjust, and / or re-adjust the cement composition. The disclosed cement composition may also directly or indirectly affect transport or delivery equipment used to transport the cement composition to a drilling site or downhole, such as transport containers, conduits, pipelines, trucks, tubes, and / or pipes used to compositionally move the cement composition from one place to another, any pumps, compressors, or motors (e.g., on the surface or in a downhole) used to flow the suspension additive or fluid containing it, any valves or associated fittings used to regulate the pressure or flow rate of the cement composition, and any sensors (i.e., pressure sensors and temperature sensors), gauges, and / or combinations thereof.The disclosed cement composition includes well casings, well liners, completion strings, insert strings, drill strings, coiled tubing, slick lines, wire lines, drill pipes, drill collars, slurry motors, downhole motors and / or pumps, cement pumps, surface-mounted motors and / or pumps, centralizers, tillers, scratchers, floats (e.g., shoes, collars, valves, etc.), logging tools and associated telemetry equipment, actuators (e.g., electromechanical devices, hydraulic mechanical devices, etc.), sliding sleeves, Production sleeves, plugs, screens, filters, flow control devices (e.g., inflow control devices, autonomous inflow control devices, outflow control devices, etc.), couplings (e.g., electro-hydraulic wet connects, dry connects, inductive couplers, etc.), control lines (electric, fiber optic, hydraulic, etc.), monitoring lines, drill bits and reamers, sensors or distributed sensors, downhole heat exchangers, valves and corresponding operating devices, tool seals, packers, cement plugs, bridge plugs, and other well isolation devices or components may be directly or indirectly affected. [Examples]

[0066] To facilitate understanding of this disclosure, several embodiments are described below. Such embodiments should not be construed as limiting or defining the scope of this disclosure.

[0067] Example 1 In this example, a high-temperature suspension additive was tested in cement. The high-temperature suspension additive was a polymer containing a mixture of acrylamide / N-vinylpyrrolidone (Ac / NVP) in a 60:40 molar ratio, crosslinked with 2% N,N′-methylenebisacrylamide (MBA) and 2% triallyl isocyanurate (TTT). In one or more embodiments, Figure 4 shows how to calculate the critical concentration (C*) of the polymer mixture Ac / NVP in a 60:40 molar ratio, crosslinked with 2% MBA and 2% TTT, based on titration data. Furthermore, cement was prepared according to Table 1 below. The thickening time of the cement slurry was then evaluated at 350°F (178°C) using a pressurized consistency meter. It was confirmed that a 3.75 g load passed through both shutdowns. [Table 1]

[0068] Example 2 In this example, high-temperature suspension additives were tested in a spacer fluid. The first high-temperature suspension additive was prepared using acrylamide and 2% triallyl isocyanurate. The first spacer fluid was prepared with 4 grams of the first high-temperature suspension additive, 1 gram of polysaccharide-based suspension additive, 695.9 grams of barite, 34.24 grams of volcanic rock, and 701.73 grams of water. The rheology of the first spacer fluid was tested at 80°F using a Fann 35 viscometer. The results of the rheology test are shown in Table 2. In this table, the measurements on the first dial are the measurements taken when the RPM was increased, and the measurements on the second dial are the measurements taken when the RPM was decreased. The second spacer fluid was prepared with 1 gram of polysaccharide-based suspension additive, 695.9 grams of barite, 34.24 grams of volcanic rock, and 701.73 grams of water. The results of the rheology test are shown in Table 3.

[0069] The first spacer fluid was aged in a convergetometer at 350°F for 30 minutes and then at 350°F for 3.5 hours. The rheology of the first spacer fluid was measured at 80°F after 30 minutes and 3.5 hours, and the data are shown in Tables 4 and 5. [Table 2] [Table 3] [Table 4] [Table 5]

[0070] Example 3 A second high-temperature suspension additive was prepared using acrylamide and N-vinylpyrrolidone in a 60:40 ratio, with 2% N,N'-methylenebisacrylamide crosslinking agent and 2% triallyl isocyanurate crosslinking agent. A third spacer fluid was prepared using 5 grams of the second high-temperature suspension additive, 695.9 grams of barite, 34.24 grams of volcanic rock, and 701.73 grams of water. The third spacer fluid was prepared at 350°F, and its rheology was tested at 80°F using a Fann 35 viscometer. The results of the rheology test are shown in Table 6. A graph of the rheology test results is shown in Figure 5.

[0071] The third spacer fluid was further adjusted to 400°F, and its rheology was measured again. The results of the adjustments are shown in Table 7 and Figure 6. [Table 6] [Table 7]

[0072] Example 4 A third high-temperature suspension additive was prepared using acrylamide with 2% N,N′-methylenebisacrylamide crosslinking agent and 2% triallyl isocyanurate crosslinking agent. A fourth spacer fluid was prepared using 4 grams of the third high-temperature suspension additive, 1 gram of polysaccharide suspension additive, 695.9 grams of barite, 34.24 grams of volcanic rock, and 701.7 grams of water. The rheology of the fourth spacer fluid was evaluated, and the results are shown in Table 8. The fourth spacer fluid was set at 350°F for 3 hours, and its rheology was tested at 80°F using a Fann 35 viscometer. The results of the rheology test are shown in Table 9. [Table 8] [Table 9]

[0073] Example 5 A fourth high-temperature suspension additive was prepared using acrylamide with 2% N,N′-methylenebisacrylamide crosslinking agent and 2% triethylene glycol divinyl ether crosslinking agent. A fifth spacer fluid was prepared using 2.92 lb / bbl of the fourth high-temperature suspension additive, 0.29 lb / bbl of a polysaccharide suspension additive, and 20 lb / bbl of volcanic rock, which were mixed to a density of 16 lbs / gallon. The fifth spacer fluid was tested in a convergetometer with a 350°F sweep. The test results are shown in Figure 7. It was observed that the viscosity of the spacer fluid increased with increasing temperature.

[0074] Example 6 In this example, several high-temperature suspension additives were prepared and tested. The prepared high-temperature suspension additives were tested in a contamination-free spacer fluid using the formulations in Table 10, a cement-contaminated spacer fluid using the formulations from Table 11, a spacer fluid for long-term testing using the formulations in Table 12, and a fishery output fluid using the formulations in Table 13. The formulations of the high-temperature suspension additives are shown in Table 14. Examples of high-temperature suspension additives include polyacrylamide (PAc), polyacrylamide / 2-acrylamide-2-methyl-1-propanesulfonic acid (PAc / AMPS), 2-acrylamide-2-methyl-1-propanesulfonic acid / N-vinylpyrrolidone (AMPS / NVP), acrylamide / N-vinylpyrrolidone (Ac / NVP), and N-vinylpyrrolidone (NVP). The test results are shown in Table 15. [Table 10] [Table 11] [Table 12] [Table 13]

[0075] To facilitate understanding of this disclosure, several embodiments are described below. Such embodiments should not be construed as limiting or defining the scope of this disclosure. [Table 14-1] JPEG2026524756000016.jpg82164 [Table 14-2] [Table 15]

[0076] Example 7 In this example, the polymer entanglement concentration (P*) was measured for the Ac / NVP(60:40)2%MBA 2%TTT polymer. 1 g of the polymer was dispersed in 50 g of deionized water. This solution was placed in a Chandler 5550 rheometer of R1B5X shape and sheared at 100 rpm during the experiment. The solution was heated to 400°F over 20 minutes while maintaining a constant N2 pressure of 1000 psi. The solution was held at 400°F for 40 minutes and then cooled to room temperature. Subsequently, the apparent viscosity (AVIS) was measured using the resulting polymer-containing solution. Four replicates of sequentially diluted solutions of the polymer Ac / NVP(60:40)2%MBA 2%TTT were measured at a shear rate of 3 rpm. The AVIS measurement results are shown in Table 16. For AVIS / concentration and Ln(AVIS) / concentration, the best-fitting straight line was calculated using the linear least squares method, and the intercept polymer entanglement concentration (P*) was calculated. Figure 8 is a visual plot of the data from Table 16 and the P* calculations. [Table 16]

[0077] Therefore, this disclosure relates to high-temperature suspension additives and methods for using high-temperature suspension additives in well-hole operations. The methods may include any of the various features disclosed herein, including one or more of the following descriptions.

[0078] Description 1. A method comprising: preparing a well treatment fluid, wherein the well treatment fluid comprises water and a high-temperature suspension additive comprising a monomer, a thermally unstable crosslinking agent having the property of being hydrolyzed at temperatures above 250°F (121°C) in the well treatment fluid, and a thermally stable crosslinking agent polymer product having the property of being hydrolyzably maintained for at least about 1 hour at temperatures in the range of 250°F (121°C) to 450°F (232°C) in the well treatment fluid; and using the well treatment fluid to discharge a fluid placed in a well.

[0079] Description 2. The method according to Description 1, wherein the monomer comprises at least one monomer selected from the group consisting of acrylamide (Ac), methacrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and its salts, N-vinylpyrrolidone (NVP), N-substituted acrylamide, N-substituted methacrylamide, N-methylacrylamide, N-ethylacrylamide, N-vinylcaprolactam, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, acrylic acid, methacrylic acid, acrylate (such as methyl acrylate and hydroxyethyl acrylate), methacrylate (such as methyl methacrylate, 2-hydroxyethyl methacrylate, and 2-dimethylaminoethyl methacrylate), and combinations thereof.

[0080] Description 3. Thermally unstable crosslinking agents include N,N'-methylenebisacrylamide, N,N'-methylenebismethacrylamide, N,N'-ethylenebisacrylamide, N,N'-propylenebisacrylamide, N,N'-(1,2-dihydroxyethylene)bisacrylamide, 1,4-diacrylpiperazine, N,N-diallylcrylamide, 1,3,5-triacryloylhexahydro-1,3,5-triazine, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,6-hexanediol The method according to any one of descriptions 1 to 2, comprising at least one crosslinking agent selected from the group consisting of di(meth)acrylate, 1,1,1-trimethylolpropane trimethacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, glycerol di(meth)acrylate, glycerol tri(meth)acrylate, triglycerol di(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, tris[2-(acryloyloxy)ethyl]isocyanurate, diallyl carbonate, divinyl adipate, divinyl sebacate, N,N′-diallyl tartardiamide, diallyl phthalate, diallyl maleate, diallyl succinate, and combinations thereof.

[0081] Description 4. The method according to any one of Descriptions 1 to 3, wherein the thermally stable crosslinking agent comprises at least one crosslinking agent selected from the group consisting of divinyl ether, diallyl ether, pentaerythritol allyl ether (PAE), allyl sucrose, ethylene glycol divinyl ether, triethylene glycol divinyl ether, diethylene glycol divinyl ether, glycerol diallyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, trimethylolpropane diallyl ether, divinylbenzene, 1,3-divinylinimidazolidine-2-one, divinyltetrahydropyrimidine-2(1H)-one, 1,7-octadiene, 1,9-decadien, triallylamine, tetraallylethylenediamine, N-vinyl-3(E)-ethylidenepyrrolidone, ethylidenebis(N-vinylpyrrolidone), triallyl isocyanurate (TTT), and combinations thereof.

[0082] Description 5. The method according to any of Description 1, wherein the high-temperature suspension additive contains acrylamide and N,N'-methylenebisacrylamide in an amount of about 1 mol% to about 6 mol%.

[0083] Description 6. The method according to Description 5, wherein the high-temperature suspension additive further comprises about 1 mol% to about 3 mol% of tri(ethyl glycol) divinyl ether.

[0084] Description 7. The method according to Description 1, wherein the high-temperature suspension additive contains acrylamide and triallyl isocyanurate in amounts of approximately 1 mol% to approximately 6 mol%.

[0085] Description 8. The method according to Description 7, wherein the high-temperature suspension additive further comprises about 1 mol% to about 3 mol% of N,N'-methylenebisacrylamide.

[0086] Description 9. The method according to Description 1, wherein the high-temperature suspension additive comprises acrylamide and 2-acrylamido-2-methyl-1-propanesulfonic acid in a molar ratio of about 60:40 to about 40:60, and about 1 mol% to about 5 mol% of triethylene glycol divinyl ether.

[0087] Description 10. The method according to Description 9, wherein the high-temperature suspension additive further comprises about 1 mol% to about 3 mol% of N,N'-methylenebisacrylamide.

[0088] Description 11. The method according to Description 1, wherein the high-temperature suspension additive contains 2-acrylamido-2-methyl-1-propanesulfonic acid and n-vinylpyrrolidone in a molar ratio of approximately 90:10 to approximately 50:50.

[0089] Description 12. The method according to Description 11, wherein the high-temperature suspension additive further comprises at least one of about 0.5 mol% to about 3 mol% of methylenebisacrylamide, about 1 mol% to about 6 mol% of triallyl isocyanurate, and combinations thereof.

[0090] Description 13. The method according to Description 1, wherein the high-temperature suspension additive contains acrylamide and N-vinylpyrrolidone in a molar ratio of approximately 90:10 to approximately 50:50.

[0091] Description 14. The method according to Description 13, wherein the high-temperature suspension additive further comprises at least one of the following: methylenebisacrylamide in an amount of about 0.5 mol% to about 3 mol%, triallyl isocyanurate in an amount of about 0.5 mol% to about 3 mol%, pentaerythritol allyl ether in an amount of about 1 mol% to about 3 mol%, and combinations thereof.

[0092] Description 15. The method according to Description 1, wherein the high-temperature suspension additive has a polymer entanglement concentration (P*) in the range of approximately 0.001 g / dL to approximately 0.1 g / dL.

[0093] Description 16. A well treatment fluid comprising water, a high-temperature suspension additive containing a monomer, a thermally unstable crosslinking agent having the property of hydrolyzing at temperatures above 250°F (121°C) in the well treatment fluid, and a polymer product of a thermally stable crosslinking agent having the property of being hydrolyzably maintained for at least about 1 hour at temperatures in the range of 250°F (121°C) to 450°F (232°C) in the well treatment fluid.

[0094] Description 17. A well treatment fluid according to Description 16, wherein the monomer comprises at least one monomer selected from the group consisting of acrylamide (Ac), methacrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and its salts, N-vinylpyrrolidone (NVP), N-substituted acrylamide, N-substituted methacrylamide, N-methylacrylamide, N-ethylacrylamide, N-vinylcaprolactam, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, acrylic acid, methacrylic acid, acrylate (such as methyl acrylate and hydroxyethyl acrylate), methacrylate (such as methyl methacrylate, 2-hydroxyethyl methacrylate, and 2-dimethylaminoethyl methacrylate), and combinations thereof.

[0095] Description 18. Thermally unstable crosslinking agents include N,N'-methylenebisacrylamide, N,N'-methylenebismethacrylamide, N,N'-ethylenebisacrylamide, N,N'-propylenebisacrylamide, N,N'-(1,2-dihydroxyethylene)bisacrylamide, 1,4-diacrylpiperazine, N,N-diallylcrylamide, 1,3,5-triacryloylhexahydro-1,3,5-triazine, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di( A well treatment fluid according to any one of descriptions 16 to 17, comprising at least one crosslinking agent selected from the group consisting of meth)acrylate, 1,1,1-trimethylolpropane trimethacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, glycerol di(meth)acrylate, glycerol tri(meth)acrylate, triglycerol di(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, tris[2-(acryloyloxy)ethyl]isocyanurate, diallyl carbonate, divinyl adipate, divinyl sebacate, N,N′-diallyl tartardiamide, diallyl phthalate, diallyl maleate, diallyl succinate, and combinations thereof.

[0096] Description 19. A well treatment fluid according to any one of Descriptions 16 to 18, wherein the thermally stable crosslinking agent comprises at least one crosslinking agent selected from the group consisting of divinyl ether, diallyl ether, pentaerythritol allyl ether (PAE), allyl sucrose, ethylene glycol divinyl ether, triethylene glycol divinyl ether, diethylene glycol divinyl ether, glycerol diallyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, trimethylolpropane diallyl ether, divinylbenzene, 1,3-divinylinimidazolidine-2-one, divinyltetrahydropyrimidine-2(1H)-one, 1,7-octadiene, 1,9-decadien, triallylamine, tetraallylethylenediamine, N-vinyl-3(E)-ethylidenepyrrolidone, ethylidenebis(N-vinylpyrrolidone), triallyl isocyanurate (TTT), and combinations thereof.

[0097] Description 20. A well treatment fluid according to any one of Descriptions 16 to 19, further comprising cement selected from the group consisting of Portland cement, slag cement, pozzolanic cement, gypsum cement, alumina cement, silica cement, and combinations thereof.

[0098] Description 21. A well treatment fluid according to any one of Descriptions 16 to 19, further comprising an acidifying material selected from the group consisting of pumice, perlite, volcanic glass, fumed silica, fly ash, and combinations thereof.

[0099] Description 22. The well treatment fluid described in Description 16, wherein the high-temperature suspension additive has a polymer entanglement concentration (P*) in the range of approximately 0.001 g / dL to approximately 0.1 g / dL.

[0100] Although the compositions and methods described herein are described as “comprising,” “containing,” or “including” various components or steps, it should be understood that the compositions and methods may also “consist essentially of” or “consist of” various components and steps. Furthermore, the indefinite articles “a” or “an” used in the claims are defined herein as meaning that there is one or more elements to which the indefinite article is taken.

[0101] For the sake of brevity, only certain ranges are explicitly disclosed in this specification. However, a range from any lower limit may be combined with any upper limit to describe ranges not explicitly stated, and similarly, a range from any lower limit may be combined with any other lower limit to describe ranges not explicitly stated, and similarly, a range from any upper limit may be combined with any other upper limit to describe ranges not explicitly stated. In addition, whenever a numerical range is disclosed with lower and upper limits, any numerical values ​​and ranges included within that range shall be specifically disclosed. In particular, all ranges of values ​​disclosed in this specification (expressed in the form of "approximately a to approximately b," or equivalently "approximately a to b," or equivalently "approximately a to b") should be understood to define all numbers and ranges that are included within a broader range of values, even if not explicitly stated. Thus, every point or individual value functions as its own lower or upper limit, and can be combined with other points or individual values, or other lower or upper limits, to describe ranges not explicitly stated.

[0102] Accordingly, this disclosure is well adapted to achieve the purposes and benefits mentioned, as well as those inherent therein. The specific embodiments disclosed above are illustrative only, for this disclosure can be modified and implemented in different but equivalent ways, which will be obvious to those skilled in the art who have the merits of the teachings herein. Although individual embodiments have been described, this disclosure covers all combinations of all these embodiments. Furthermore, no limitation is intended to the structural or design details shown herein, except those set forth in the following claims. Also, terms in the claims have their plain, ordinary meanings unless expressly and clearly defined by the patentee. Accordingly, it is obvious that specific exemplary embodiments disclosed above can be modified or altered, and all such modifications are considered to be within the scope and spirit of this disclosure. Where there is a difference between the usage of a word or term herein and its usage in one or more patents or other documents incorporated herein by reference, the definition consistent with this specification should be adopted.

Claims

1. It is a method, The process involves preparing a well treatment fluid, wherein the well treatment fluid is Water and, The preparation comprises a high-temperature suspension additive containing a monomer, a thermally unstable crosslinking agent having the property of hydrolyzing at temperatures above 250°F (121°C) in the well treatment fluid, and a polymer product of a thermally stable crosslinking agent having the property of being hydrolyzably maintained for at least about 1 hour at temperatures in the range of 250°F (121°C) to 450°F (232°C) in the well treatment fluid, A method comprising using a well treatment fluid to discharge fluid located inside a well.

2. The method according to claim 1, wherein the monomer comprises at least one monomer selected from the group consisting of acrylamide (Ac), methacrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and its salts, N-vinylpyrrolidone (NVP), N-substituted acrylamide, N-substituted methacrylamide, N-methylacrylamide, N-ethylacrylamide, N-vinylcaprolactam, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, acrylic acid, methacrylic acid, acrylate (methyl acrylate, hydroxyethyl acrylate, etc.), methacrylate (methyl methacrylate, 2-hydroxyethyl methacrylate, and 2-dimethylaminoethyl methacrylate, etc.), and combinations thereof.

3. The thermally unstable crosslinking agent is N,N'-methylenebisacrylamide, N,N'-methylenebismethacrylamide, N,N'-ethylenebisacrylamide, N,N'-propylenebisacrylamide, N,N'-(1,2-dihydroxyethylene)bisacrylamide, 1,4-diacryoylpiperazine, N,N-diallylcrylamide, 1,3,5-triacryloylhexahydro-1,3,5-triazine, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol The method according to claim 2, comprising at least one crosslinking agent selected from the group consisting of di(meth)acrylate, 1,1,1-trimethylolpropane trimethacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, glycerol di(meth)acrylate, glycerol tri(meth)acrylate, triglycerol di(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, tris[2-(acryloyloxy)ethyl]isocyanurate, diallyl carbonate, divinyl adipate, divinyl sebacate, N,N'-diallyl tartardiamide, diallyl phthalate, diallyl maleate, diallyl succinate, and combinations thereof.

4. The method according to claim 2, wherein the thermally stable crosslinking agent comprises at least one crosslinking agent selected from the group consisting of divinyl ether, diallyl ether, pentaerythritol allyl ether (PAE), allyl sucrose, ethylene glycol divinyl ether, triethylene glycol divinyl ether, diethylene glycol divinyl ether, glycerol diallyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, trimethylolpropane diallyl ether, divinylbenzene, 1,3-divinylinimidazolidine-2-one, divinyltetrahydropyrimidine-2(1H)-one, 1,7-octadiene, 1,9-decadien, triallylamine, tetraallylethylenediamine, N-vinyl-3(E)-ethylidenepyrrolidone, ethylidenebis(N-vinylpyrrolidone), triallyl isocyanurate (TTT), and combinations thereof.

5. The method according to claim 1, wherein the high-temperature suspension additive contains acrylamide and N,N'-methylenebisacrylamide in an amount of about 1 mol% to about 6 mol%.

6. The method according to claim 5, wherein the high-temperature suspension additive further comprises about 1 mol% to about 3 mol% of triethylene glycol divinyl ether.

7. The method according to claim 1, wherein the high-temperature suspension additive contains acrylamide and triallyl isocyanurate in an amount of about 1 mol% to about 6 mol%.

8. The method according to claim 7, wherein the high-temperature suspension additive further comprises N,N'-methylenebisacrylamide in an amount of about 1 mol% to about 3 mol%.

9. The method according to claim 1, wherein the high-temperature suspension additive comprises acrylamide and 2-acrylamido-2-methyl-1-propanesulfonic acid in a molar ratio of about 60:40 to about 40:60, and triethylene glycol divinyl ether in an amount of about 1 mol% to about 5 mol%.

10. The method according to claim 9, wherein the high-temperature suspension additive further comprises N,N'-methylenebisacrylamide in an amount of about 1 mol% to about 3 mol%.

11. The method according to claim 1, wherein the high-temperature suspension additive comprises 2-acrylamido-2-methyl-1-propanesulfonic acid and N-vinylpyrrolidone in a molar ratio of about 90:10 to about 50:

50.

12. The method according to claim 11, wherein the high-temperature suspension additive further comprises at least one of about 0.5 mol% to about 3 mol% of N,N'-methylenebisacrylamide, about 1 mol% to about 6 mol% of triallyl isocyanurate, and combinations thereof.

13. The method according to claim 1, wherein the high-temperature suspension additive comprises acrylamide and N-vinylpyrrolidone in a molar ratio of about 90:10 to about 50:

50.

14. The method according to claim 13, wherein the high-temperature suspension additive further comprises at least one of the following: N,N'-methylenebisacrylamide in an amount of about 0.5 mol% to about 3 mol%, triallyl isocyanurate in an amount of about 0.5 mol% to about 3 mol%, pentaerythritol allyl ether in an amount of about 1 mol% to about 3 mol%, and combinations thereof.

15. The method according to claim 1, wherein the high-temperature suspension additive has a polymer entanglement concentration (P*) in the range of about 0.001 g / dL to about 0.1 g / dL.

16. A well treatment fluid, Water and, A well treatment fluid comprising a monomer, a thermally unstable crosslinking agent having the property of hydrolyzing at temperatures exceeding 250°F (121°C) in the well treatment fluid, and a high-temperature suspension additive containing a polymer product of a thermally stable crosslinking agent having the property of being hydrolyzably maintained for at least about 1 hour at temperatures in the range of 250°F (121°C) to 450°F (232°C) in the well treatment fluid.

17. The well treatment fluid according to claim 16, wherein the monomer comprises at least one monomer selected from the group consisting of acrylamide (Ac), methacrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and its salts, N-vinylpyrrolidone (NVP), N-substituted acrylamide, N-substituted methacrylamide, N-methylacrylamide, N-ethylacrylamide, N-vinylcaprolactam, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, acrylic acid, methacrylic acid, acrylate (such as methyl acrylate and hydroxyethyl acrylate), methacrylate (such as methyl methacrylate, 2-hydroxyethyl methacrylate, and 2-dimethylaminoethyl methacrylate), and combinations thereof.

18. The thermally unstable crosslinking agent is N,N'-methylenebisacrylamide, N,N'-methylenebismethacrylamide, N,N'-ethylenebisacrylamide, N,N'-propylenebisacrylamide, N,N'-(1,2-dihydroxyethylene)bisacrylamide, 1,4-diacryoylpiperazine, N,N-diallylcrylamide, 1,3,5-triacryloylhexahydro-1,3,5-triazine, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol The well treatment fluid according to claim 17, comprising at least one crosslinking agent selected from the group consisting of di(meth)acrylate, 1,1,1-trimethylolpropane trimethacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, glycerol di(meth)acrylate, glycerol tri(meth)acrylate, triglycerol di(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, tris[2-(acryloyloxy)ethyl]isocyanurate, diallyl carbonate, divinyl adipate, divinyl sebacate, N,N'-diallyl tartardiamide, diallyl phthalate, diallyl maleate, diallyl succinate, and combinations thereof.

19. The well treatment fluid according to claim 17, wherein the thermally stable crosslinking agent comprises at least one crosslinking agent selected from the group consisting of divinyl ether, diallyl ether, pentaerythritol allyl ether (PAE), allyl sucrose, ethylene glycol divinyl ether, triethylene glycol divinyl ether, diethylene glycol divinyl ether, glycerol diallyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, trimethylolpropane diallyl ether, divinylbenzene, 1,3-divinylinimidazolidine-2-one, divinyltetrahydropyrimidine-2(1H)-one, 1,7-octadiene, 1,9-decadien, triallylamine, tetraallylethylenediamine, N-vinyl-3(E)-ethylidenepyrrolidone, ethylidenebis(N-vinylpyrrolidone), triallyl isocyanurate (TTT), and combinations thereof.

20. The well treatment fluid according to claim 16, further comprising cement selected from the group including Portland cement, slag cement, pozzolanic cement, gypsum cement, alumina cement, silica cement, and combinations thereof.

21. The well treatment fluid according to claim 16, further comprising an acidifying material selected from the group consisting of pumice, perlite, volcanic glass, fumed silica, fly ash, and combinations thereof.

22. The well treatment fluid according to claim 16, wherein the high-temperature suspension additive has a polymer entanglement concentration (P*) in the range of about 0.001 g / dL to about 0.1 g / dL.

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