Green environmentally friendly temporary plugging agent and preparation method and application thereof

Abstract

The present invention relates to the technical field of oil and gas reservoir development, and specifically to a green and environmentally friendly temporary plugging agent and a preparation method and application thereof. The preparation method comprises: (1) first mixing a polymer, a mother solution of n-octyl triethoxysilane, nano-ceramic fibers and water to obtain a prepolymer system; (2) secondly mixing the prepolymer system, L-arginine, α-cyclodextrin and an auxiliary agent to obtain a pre-crosslinking system, and then crosslinking the pre-crosslinking system to obtain a temporary plugging agent; wherein the preparation raw materials comprise: 1-10% polymer, 0.05-0.5% mother solution of n-octyl triethoxysilane, 0.05-0.5% nano-ceramic fibers, 79-97% water, 0.5-5% L-arginine, 0.5-5% α-cyclodextrin and 0.005-0.05% auxiliary agent. The method has a high gelling temperature, the temporary plugging agent has excellent heat and salt resistance, and the residue rate after degradation is low, and can be used for the efficient development of high-temperature oil and gas reservoirs or heavy oil reservoirs.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas reservoir development, and in particular to a green and environmentally friendly temporary plugging agent and a preparation method and application thereof. Background Art

[0002] With the continuous exploitation and consumption of conventional crude oil, the importance of heavy oil reservoirs and deep / ultra-deep oil and gas reservoirs has become self-evident. As an important part of unconventional resources, heavy oil reservoirs and deep or ultra-deep oil and gas reservoirs are crucial to the long-term stable development of the oil industry and to ensuring energy security.

[0003] For deep oil and gas resources, due to the great burial depth, the reservoir temperature generally exceeds 150℃, and some wells can reach above 180℃. For heavy oil reservoirs, heat injection is usually used for development, which makes the reservoir temperature generally exceed 120℃. When deep oil and gas reservoirs and heavy oil reservoirs are developed to a certain stage, significant crossflow will occur along the dominant channel, which brings huge challenges to the long-term and efficient development of these oil and gas reservoirs. Temporary plugging agents (or profile control agents) can play a good role in plugging / temporarily plugging the dominant channel. However, the temperature resistance of the currently commonly used temporary plugging agent system is poor, generally not exceeding 120℃, and the stability is poor under high temperature conditions, and it is easy to break the gel. In addition, due to the shearing effect of the formation pore medium, the macromolecular polymer organic temporary plugging agent is easily damaged by shear before gelation, which makes its injection distance short and reduces the gelation performance in the target layer; while the inorganic plugging agent has the problems of poor toughness and large volume shrinkage, which makes its temporary plugging performance poor in high-temperature and high-salt oil and gas reservoirs, resulting in the phenomenon of not being able to block. In addition, due to the development characteristics of oil and gas reservoirs, after a certain period of temporary plugging, it may be necessary to reuse the dominant channel. For this reason, the plugging agent is required to be able to be released under certain conditions.

[0004] Therefore, for the development of high-temperature oil and gas reservoirs or heavy oil reservoirs, it is urgent to develop temporary plugging agent products with excellent temporary plugging performance and resistance to high temperature and high salt. Summary of the invention

[0005] Aiming at the problems that the existing gel plugging agent for oil and gas reservoir development has poor high temperature resistance and high salt resistance and unsatisfactory temporary plugging performance, the present invention provides a green and environmentally friendly temporary plugging agent and a preparation method and application thereof.

[0006] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a temporary plugging agent, the method comprising:

[0007] (1) first mixing a polymer, a mother solution of n-octyltriethoxysilane, nano-ceramic fibers and water to obtain a prepolymer system;

[0008] (2) the prepolymer system, L-arginine, α-cyclodextrin and the auxiliary agent are mixed for a second time to obtain a pre-crosslinked system, and then the pre-crosslinked system is subjected to a crosslinking reaction to obtain a temporary plugging agent;

[0009] Among them, based on the total weight of the raw materials for preparation, the raw materials for preparation include: 1-10% of the polymer, 0.05-0.5% of the mother liquor of n-octyltriethoxysilane, 0.05-0.5% of the nano-ceramic fiber, 79%-97% of water, 0.5-5% of L-arginine, 0.5-5% of α-cyclodextrin and 0.005-0.05% of the auxiliary agent.

[0010] The second aspect of the present invention provides a temporary plugging agent prepared by the preparation method described in the first aspect.

[0011] The third aspect of the present invention provides the use of the preparation method described in the first aspect or the temporary plugging agent described in the second aspect in the development of high-temperature oil and gas reservoirs or heavy oil reservoirs.

[0012] The preparation method of the temporary plugging agent provided by the present invention is based on specific preparation raw materials and adopts the preparation idea of ​​first polycondensation and then crosslinking. The obtained pre-crosslinked system has good injectability and high gelling temperature (above 100°C). The gelling viscosity of the obtained gel temporary plugging agent after gelling is adjustable (8000-50000mPa·s), the temperature resistance is higher than 150°C (up to 300°C), the salt resistance is greater than 200,000 mg / L (mineralization, up to 300,000 mg / L), the degradation is controllable (the degradation time is 30-300 days under 120-300°C environment), the residue is low (the residue rate after degradation is not higher than 5%), and the temporary plugging agent can be used for temporary plugging (or oil and gas well profile adjustment, injection well drive adjustment, etc.) construction under high temperature and high salt working conditions. The method has excellent temporary plugging performance, realizes the efficient development of deep or ultra-deep oil and gas reservoirs and thermal recovery heavy oil reservoirs, and is environmentally friendly. DETAILED DESCRIPTION

[0013] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0014] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0015] A first aspect of the present invention provides a method for preparing a temporary plugging agent, the method comprising:

[0016] (1) first mixing a polymer, a mother solution of n-octyltriethoxysilane, nano-ceramic fibers and water to obtain a prepolymer system;

[0017] (2) the prepolymer system, L-arginine, α-cyclodextrin and the auxiliary agent are mixed for a second time to obtain a pre-crosslinked system, and then the pre-crosslinked system is subjected to a crosslinking reaction to obtain a temporary plugging agent;

[0018] Among them, based on the total weight of the preparation raw materials, the preparation raw materials include: 1-10% of the polymer, 0.05-0.5% of the n-octyltriethoxysilane mother liquor, 0.05-0.5% of the nano-ceramic fiber, 79-97% of water, 0.5-5% of L-arginine, 0.5-5% of α-cyclodextrin and 0.005-0.05% of the auxiliary agent.

[0019] According to the present invention, the sum of the weight percentages of the various components in the raw material for preparation is 100%.

[0020] According to the present invention, in the preparation method of the temporary plugging agent, in step (1), the polymer, n-octyltriethoxysilane mother liquor, nano-ceramic fiber and water are first mixed. During the first mixing process, the n-octyltriethoxysilane molecules are first hydrolyzed to form silanols, and then polycondensed to form long carbon chain oligomers, and then associated with the surface of the nano-ceramic fiber through hydrogen bonds to obtain a prepolymer system. The prepolymer system can protect the molecular chain of the polymer and delay its chain breaking at high temperature. On the other hand, it can also provide a bridging effect on the broken polymer molecules to improve their thermal stability.

[0021] According to the present invention, in the preparation method of the temporary plugging agent, in step (1), on the basis of satisfying the above-mentioned raw material feed ratio, preferably, the weight ratio of the n-octyltriethoxysilane mother liquor and the nano-ceramic fiber is 1: (0.5-2), which is more conducive to the association between the long carbon chain oligomer and the nano-ceramic fiber, thereby improving the performance of the prepolymer system.

[0022] According to the present invention, in the preparation method of the temporary plugging agent, the prepolymer system obtained in step (1) can undergo a cross-linking reaction with L-arginine and α-cyclodextrin to form a gel. In the present invention, the polymer is broadly defined, and any polymer that can undergo a cross-linking reaction with L-arginine and α-cyclodextrin can be selected. Preferably, the polymer includes polyacrylamide and a terpolymer; wherein the molar ratio of polyacrylamide: terpolymer is 1: (2-5), which can obtain better gel properties and facilitate the control of the cross-linking reaction rate.

[0023] According to the present invention, in the preparation method of the temporary plugging agent, the polyacrylamide is limited to a wide range. Preferably, the number average molecular weight of the polyacrylamide is in the range of 500,000-5,000,000 g / mol, and the degree of hydrolysis of the polyacrylamide is 10-15%, which is more conducive to the cross-linking reaction of the prepolymer system.

[0024] In the present invention, there is no particular limitation on the source of the polyacrylamide, which can be prepared by a known method or a commercially available product.

[0025] According to the present invention, preferably, the terpolymer contains structural unit A provided by acrylamide monomer, structural unit B provided by 2-acrylamide-2-methylpropanesulfonic acid monomer and structural unit C provided by vinyl pyrrolidone monomer; based on the total molar amount of each structural unit, in the terpolymer, the content of the structural unit B is 10-15 mol%, and the content of the structural unit C is 10-15 mol%. The use of the terpolymer having the above structural composition can enhance the temperature resistance and salt resistance of the terpolymer.

[0026] According to the present invention, preferably, the number average molecular weight of the terpolymer is in the range of 1 million to 8 million g / mol, and the degree of hydrolysis is 10-15%, which is more conducive to rapid dissolution and dispersion in water.

[0027] In the present invention, there is no particular limitation on the source of the terpolymer, and it can be obtained by self-production using conventional methods or by using commercially available products. For the self-production method, for example, the preparation method may include: in the presence of a solvent and a catalyst, acrylamide monomer, 2-acrylamide-2-methylpropanesulfonic acid monomer and vinyl pyrrolidone monomer are polymerized to obtain the terpolymer. Preferably, the solvent may be selected from at least one of isopropanol, toluene and acetone. Preferably, the catalyst may be a nickel-based catalyst. Preferably, the conditions of the polymerization reaction include: a temperature of 45-75°C and a time of 2-7h. In addition to being obtained by self-production, the terpolymer can also be purchased from Aisen (China) Flocculant Co., Ltd.

[0028] According to the present invention, in the method for preparing the temporary plugging agent, in step (1), the n-octyltriethoxysilane mother liquor is an n-octyltriethoxysilane aqueous solution with a concentration of 0.5-1.5 wt %.

[0029] According to the present invention, the n-octyltriethoxysilane aqueous solution can be prepared by mixing n-octyltriethoxysilane with water. According to a preferred embodiment of the present invention, the method for preparing the n-octyltriethoxysilane mother liquor comprises: mixing an organic acid with water to obtain an acid solution with a pH value of 3.5-4.5, and then dissolving n-octyltriethoxysilane in the acid solution to obtain the n-octyltriethoxysilane mother liquor.

[0030] According to the present invention, the organic acid can promote the dissolution of n-octyltriethoxysilane in water. Preferably, the organic acid can be formic acid and / or acetic acid.

[0031] According to the present invention, in the preparation method of the temporary plugging agent, in step (1), the nano-ceramic fiber can react with the oligomer formed by hydrolysis and polycondensation of n-octyltriethoxysilane. Preferably, the nano-ceramic fiber can be selected from at least one of alumina nano-ceramic fiber, silicon nitride nano-ceramic fiber, silicon carbide nano-ceramic fiber and boron nitride nano-ceramic fiber, and more preferably silicon carbide nano-ceramic fiber.

[0032] According to the present invention, preferably, the length of the nano-ceramic fiber is 100-500 nm, which is more conducive to improving the reaction performance of the prepolymerization system.

[0033] According to the present invention, in the preparation method of the temporary plugging agent, in step (1), the auxiliary agent can control the degradation process of the temporary plugging agent and reduce the residue rate, thereby reducing damage to the reservoir. Preferably, the auxiliary agent can be selected from at least one of N,N-dimethylformamide, N,N-dimethylpropionamide, ‌N-methyl-2-pyrrolidone, N-ethylpyrrolidone and N-methylpyrrolidone, and more preferably N,N-dimethylformamide.

[0034] According to the present invention, in the preparation method of the temporary plugging agent, in step (1), the implementation method of the first mixing is not particularly limited, as long as the polymer, the mother solution of n-octyltriethoxysilane, the nano-ceramic fiber and water can be fully mixed to obtain a prepolymer system. According to a preferred embodiment of the present invention, the polymer, the mother solution of n-octyltriethoxysilane and the nano-ceramic fiber can be added to water, stirred and mixed evenly to obtain a prepolymer system. Preferably, the conditions of the first mixing include: a temperature of 20-80°C and a time of 10-60min.

[0035] According to the present invention, in the preparation method of the temporary plugging agent, in step (1), the polymer, the mother solution of n-octyltriethoxysilane, the nano-ceramic fiber and water are first mixed to obtain a prepolymer system; wherein the water (i.e., raw water) for the first mixing with the polymer, the mother solution of n-octyltriethoxysilane and the nano-ceramic fiber can be salt-free water or salt water with a certain mineralization degree (e.g., salt water with a NaCl content not exceeding 300,000 mg / L). In the case where the water involved in the first mixing is salt water, the salt water is regarded as raw water, that is, the weight of the salt water as raw water accounts for 79-97% of the total weight of the raw materials for preparation.

[0036] According to the present invention, in the method for preparing the temporary plugging agent, in step (2), the L-arginine and α-cyclodextrin can be conventional commercial products, and the present invention does not impose any particular limitation thereto.

[0037] According to the present invention, in the preparation method of the temporary plugging agent, in step (2), there is no particular limitation on the order of adding the prepolymer system, L-arginine, α-cyclodextrin and the auxiliary agent and the conditions of the second mixing, as long as the prepolymer system, L-arginine, α-cyclodextrin and the auxiliary agent can be fully mixed to obtain a pre-crosslinked system.

[0038] According to the present invention, the pre-crosslinking system has a relatively low viscosity, and thus has good injectability in the formation, which is conducive to reducing injection pressure and construction costs. Preferably, the viscosity of the pre-crosslinking system (at 30°C) is 30-150 mPa·s.

[0039] According to the present invention, in the method for preparing the temporary plugging agent, in step (2), the conditions of the cross-linking reaction include: temperature of 120-180° C. and time of 4-50 h.

[0040] According to the present invention, in the preparation method of the temporary plugging agent, the pre-crosslinking system has the above-mentioned higher gelling temperature (crosslinking temperature), which is conducive to its gelling at the high-temperature position predetermined for temporary plugging, thereby improving the success rate of temporary plugging.

[0041] According to the present invention, the gel material (temporary plugging agent) obtained after the cross-linking reaction has a dense skeleton structure. By adjusting the proportion of each component in the raw material, the gel viscosity of the gel temporary plugging agent obtained after gelation can be adjusted (8000-50000 mPa·s). The temporary plugging agent has excellent temperature resistance (temperature resistance is higher than 150°C, up to 300°C) and salt resistance (salt resistance mineralization is greater than 200,000 mg / L, up to 300,000 mg / L). The degradation time of the temporary plugging agent under an environment of 120-300°C is 30-300 days, and the residue after degradation is not higher than 5%, preferably lower than 1%. It has excellent temporary plugging performance under high temperature and high salt working conditions, and can be used for the efficient development of deep or ultra-deep oil and gas reservoirs and thermal recovery heavy oil reservoirs. While increasing oil and gas production capacity, it has little damage to the reservoir and is environmentally friendly.

[0042] The second aspect of the present invention provides a temporary plugging agent prepared by the preparation method described in the first aspect.

[0043] The temporary plugging agent provided by the present invention is a gel plugging material, the gel viscosity is adjustable in the range of 8000-50000 mPa·s, has excellent temperature resistance, can withstand temperatures higher than 150°C, and can reach up to 300°C), and has excellent salt resistance, with a salt resistance mineralization greater than 200,000 mg / L, and can reach up to 300,000 mg / L. The temporary plugging agent has a degradation time of 30-300 days in an environment of 120-300°C, and the residue after degradation is not higher than 5%. It has excellent temporary plugging performance in the development of deep or ultra-deep oil and gas reservoirs and thermal recovery heavy oil reservoirs, thereby increasing oil and gas production capacity. The temporary plugging agent is adaptable to a wide range of formation conditions, has little damage to the reservoir, and is environmentally friendly.

[0044] The third aspect of the present invention provides the use of the preparation method described in the first aspect or the temporary plugging agent described in the second aspect in the development of high-temperature oil and gas reservoirs or heavy oil reservoirs.

[0045] The present invention will be described in detail below by way of examples. In the following examples and comparative examples,

[0046] Polyacrylamide: number average molecular weight is 1.5 million g / mol, degree of hydrolysis is 12%, purchased from Aisen (China) Flocculant Co., Ltd.

[0047] Terpolymer: number average molecular weight is 3.5 million g / mol, degree of hydrolysis is 10%, purchased from Aisen (China) Flocculant Co., Ltd.; the terpolymer contains structural unit A provided by acrylamide monomer, structural unit B provided by 2-acrylamide-2-methylpropanesulfonic acid monomer and structural unit C provided by vinyl pyrrolidone monomer; based on the total molar amount of each structural unit, the content of structural unit B is 15 mol%, and the content of structural unit C is 15 mol%.

[0048] n-Octyltriethoxysilane mother liquor: Formic acid was added to water and mixed thoroughly to obtain an acid solution with a pH value of 4, and then n-octyltriethoxysilane was added to the acid solution and stirred thoroughly until it was completely dissolved to obtain n-octyltriethoxysilane mother liquor (the concentration of n-octyltriethoxysilane was 1 wt %).

[0049] Silicon carbide nano-ceramic fibers with an average length of 150 nm were purchased from Almei (Suzhou) Technology Co., Ltd.

[0050] L-arginine: purchased from Aladdin Biochemical Technology Co., Ltd.

[0051] α-Cyclodextrin: purchased from Aladdin Biochemical Technology Co., Ltd.

[0052] N,N-Dimethylformamide: purchased from Aladdin Biochemical Technology Co., Ltd.

[0053] Water: Brine with a NaCl concentration of 300,000 mg / L was used to simulate high mineralization conditions.

[0054] Viscosity of prepolymer system (30°C): measured using a rheometer (model: HAAKE MARS 40).

[0055] Gelation viscosity: measured at gelation temperature using a rheometer (model: HAAKE MARS 40).

[0056] Unless otherwise specified, other materials used are common commercially available products.

[0057] Example 1

[0058] Preparation raw materials: polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:2) 4 wt%, n-octyltriethoxysilane mother liquor 0.2 wt%, silicon carbide nano-ceramic fiber 0.2 wt%, L-arginine 2 wt%, α-cyclodextrin 2 wt%, N,N-dimethylformamide 0.02 wt% and water 91.58 wt%.

[0059] Preparation process:

[0060] (1) Add the polymer, n-octyltriethoxysilane mother liquor and silicon carbide nano-ceramic fiber into water according to the above ratio, and stir and mix them at 30° C. for 0.5 h to obtain a uniform prepolymer system;

[0061] (2) L-arginine, α-cyclodextrin and N,N-dimethylformamide are added to the above prepolymerization system and stirred and mixed to obtain a pre-crosslinking system. The obtained pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as S1).

[0062] Among them, the viscosity of the pre-crosslinking system, the gelling temperature (the temperature of the crosslinking reaction), the gelling time (the time of the crosslinking reaction), and the gelling viscosity (the viscosity of S1 at the gelling temperature) are shown in Table 1.

[0063] S1 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0064] Example 2

[0065] Preparation raw materials: polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:4) 8% by weight, n-octyltriethoxysilane mother liquor 0.4% by weight, silicon carbide nano-ceramic fiber 0.4% by weight, L-arginine 4% by weight, α-cyclodextrin 4% by weight, N,N-dimethylformamide 0.04% by weight and water 83.16% by weight.

[0066] Preparation process:

[0067] (1) Add the polymer, n-octyltriethoxysilane mother liquor and silicon carbide nano-ceramic fiber into water according to the above-mentioned proportions, and stir and mix them thoroughly at 30° C. for 1 hour to obtain a uniform prepolymer system;

[0068] (2) L-arginine, α-cyclodextrin and N,N-dimethylformamide are added to the above prepolymerization system and stirred thoroughly to obtain a pre-crosslinking system. The pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as S2).

[0069] Among them, the viscosity of the pre-crosslinking system, the gelling temperature (the temperature of the crosslinking reaction), the gelling time (the time of the crosslinking reaction), and the gelling viscosity (the viscosity of S2 at the gelling temperature) are shown in Table 1.

[0070] S2 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0071] Example 3

[0072] Preparation raw materials: polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:2) 2% by weight, n-octyltriethoxysilane mother liquor 0.1% by weight, silicon carbide nano-ceramic fiber 0.1% by weight, L-arginine 1% by weight, α-cyclodextrin 1% by weight, N,N-dimethylformamide 0.01% by weight and water 95.79% by weight.

[0073] Preparation process:

[0074] (1) Add the polymer, n-octyltriethoxysilane mother liquor and silicon carbide nano-ceramic fiber into water according to the above ratio, and stir and mix them at 30° C. for 0.5 h to obtain a uniform prepolymer system;

[0075] (2) L-arginine, α-cyclodextrin and N,N-dimethylformamide are added to the above prepolymerization system and the mixture is stirred and mixed to obtain a pre-crosslinking system. The pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as S3).

[0076] The viscosity of the pre-crosslinking system, the gelling temperature (the temperature of the crosslinking reaction), the gelling time (the time of the crosslinking reaction), and the gelling viscosity (the viscosity of S3 at the gelling temperature) are shown in Table 1.

[0077] S3 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0078] Example 4

[0079] Preparation raw materials: 1 wt% of polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:2), 0.05 wt% of n-octyltriethoxysilane mother liquor, 0.05 wt% of silicon carbide nanoceramic fiber, 0.5 wt% of L-arginine, 0.5 wt% of α-cyclodextrin, 0.005 wt% of N,N-dimethylformamide and 97.895 wt% of water.

[0080] Preparation process:

[0081] (1) Add the polymer, n-octyltriethoxysilane mother liquor and silicon carbide nano-ceramic fiber into water according to the above ratio, and stir and mix them at 30° C. for 0.5 h to obtain a uniform prepolymer system;

[0082] (2) L-arginine, α-cyclodextrin and N,N-dimethylformamide are added to the above prepolymerization system and the mixture is stirred and mixed to obtain a pre-crosslinking system. The pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as S4).

[0083] The viscosity of the pre-crosslinking system, the gelling temperature (the temperature of the crosslinking reaction), the gelling time (the time of the crosslinking reaction), and the gelling viscosity (the viscosity of S4 at the gelling temperature) are shown in Table 1.

[0084] S4 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0085] Example 5

[0086] Preparation raw materials: polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:2) 4 wt%, n-octyltriethoxysilane mother liquor 0.2 wt%, silicon carbide nano-ceramic fiber 0.2 wt%, L-arginine 2 wt%, α-cyclodextrin 2 wt%, N,N-dimethylformamide 0.01 wt% and water 91.59 wt%.

[0087] Preparation process:

[0088] (1) Add the polymer, n-octyltriethoxysilane mother liquor and silicon carbide nano-ceramic fiber into water according to the above ratio, and stir and mix them at 30° C. for 0.5 h to obtain a uniform prepolymer system;

[0089] (2) L-arginine, α-cyclodextrin and N,N-dimethylformamide are added to the above prepolymerization system and stirred thoroughly to obtain a pre-crosslinking system. The pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as S5).

[0090] The viscosity, gelation temperature (temperature of the cross-linking reaction), gelation time (time of the cross-linking reaction), and gelation viscosity (viscosity of S5 at the gelation temperature) of the pre-cross-linking system are shown in Table 1.

[0091] S5 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0092] Example 6

[0093] Preparation raw materials: polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:2) 4 wt%, n-octyltriethoxysilane mother liquor 0.2 wt%, silicon carbide nano-ceramic fiber 0.2 wt%, L-arginine 2 wt%, α-cyclodextrin 2 wt%, N,N-dimethylformamide 0.04 wt% and water 91.56 wt%.

[0094] Preparation process:

[0095] (1) Add the polymer, n-octyltriethoxysilane mother liquor and silicon carbide nano-ceramic fiber into water according to the above ratio, and stir and mix them at 30° C. for 0.5 h to obtain a uniform prepolymer system;

[0096] (2) L-arginine, α-cyclodextrin and N,N-dimethylformamide are added to the above prepolymerization system and stirred and mixed to obtain a pre-crosslinking system. The obtained pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as S6).

[0097] The viscosity, gelling temperature (temperature of cross-linking reaction), gelling time (time of cross-linking reaction), and gelling viscosity (viscosity of S6 at gelling temperature) of the pre-cross-linking system are shown in Table 1.

[0098] S6 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0099] Example 7

[0100] Preparation raw materials: polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:2) 4 wt%, n-octyltriethoxysilane mother liquor 0.2 wt%, silicon carbide nano-ceramic fiber 0.2 wt%, L-arginine 2 wt%, α-cyclodextrin 2 wt%, N,N-dimethylformamide 0.05 wt% and water 91.55 wt%.

[0101] Preparation process:

[0102] (1) Add the polymer, n-octyltriethoxysilane mother liquor and silicon carbide nano-ceramic fiber into water according to the above ratio, and stir and mix them at 30° C. for 0.5 h to obtain a uniform prepolymer system;

[0103] (2) L-arginine, α-cyclodextrin and N,N-dimethylformamide are added to the above prepolymerization system and the mixture is stirred and mixed to obtain a pre-crosslinking system. The pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as S7).

[0104] The viscosity, gelation temperature (crosslinking reaction temperature), gelation time (crosslinking reaction time), and gelation viscosity (S7 viscosity) of the pre-crosslinking system are shown in Table 1.

[0105] S7 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0106] Example 8

[0107] Preparation materials: the same as those in Example 1.

[0108] Preparation process: According to the method of the embodiment, the difference is that only the temperature of the cross-linking reaction is changed, and the other steps and conditions are the same as those in Example 1, to obtain a temporary plugging agent (denoted as S8).

[0109] The viscosity, gelling temperature (temperature of cross-linking reaction), gelling time (time of cross-linking reaction), and gelling viscosity (viscosity of S8 at gelling temperature) of the pre-cross-linking system are shown in Table 1.

[0110] S8 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0111] Example 9

[0112] Preparation materials: the same as those in Example 1.

[0113] Preparation process: According to the method of the embodiment, the difference is that only the temperature of the cross-linking reaction is changed, and the other steps and conditions are the same as those in Example 1, to obtain a temporary plugging agent (denoted as S9).

[0114] The viscosity, gelling temperature (temperature of cross-linking reaction), gelling time (time of cross-linking reaction), and gelling viscosity (viscosity of S9 at gelling temperature) of the pre-cross-linking system are shown in Table 1.

[0115] S9 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0116] Comparative Example 1

[0117] Preparation raw materials: polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:2) 4 wt%, silicon carbide nano-ceramic fiber 0.2 wt%, L-arginine 2 wt%, α-cyclodextrin 2 wt%, N,N-dimethylformamide 0.02 wt% and water 91.78 wt%.

[0118] Preparation process:

[0119] (1) Add the polymer and silicon carbide nano-ceramic fiber into water according to the above ratio, and stir and mix them at 30°C for 0.5h to obtain a uniform prepolymer system;

[0120] (2) L-arginine, α-cyclodextrin and N,N-dimethylformamide are added to the above prepolymerization system and stirred thoroughly to obtain a pre-crosslinking system. The obtained pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as D1).

[0121] The viscosity, gelation temperature (temperature of the cross-linking reaction), gelation time (time of the cross-linking reaction), and gelation viscosity (viscosity of D1 at the gelation temperature) of the pre-cross-linking system are shown in Table 1.

[0122] D1 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0123] Comparative Example 2

[0124] Preparation raw materials: 4 wt % of polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:2), 0.2 wt % of n-octyltriethoxysilane mother liquor, 2 wt % of L-arginine, 2 wt % of α-cyclodextrin, 0.02 wt % of N,N-dimethylformamide and 91.78 wt % of water.

[0125] Preparation process:

[0126] (1) Add the polymer and n-octyltriethoxysilane mother liquor into water according to the above ratio, and stir and mix them thoroughly at 30°C for 0.5h to obtain a uniform prepolymer system;

[0127] (2) L-arginine, α-cyclodextrin and N,N-dimethylformamide are added to the above prepolymerization system and stirred thoroughly to obtain a pre-crosslinking system. The obtained pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as D2).

[0128] The viscosity, gelling temperature (temperature of cross-linking reaction), gelling time (time of cross-linking reaction), and gelling viscosity (viscosity of D2 at gelling temperature) of the pre-cross-linking system are shown in Table 1.

[0129] D2 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0130] Comparative Example 3

[0131] Preparation raw materials: polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:2) 4 wt%, n-octyltriethoxysilane mother liquor 0.2 wt%, silicon carbide nanoceramic fiber 0.2 wt%, α-cyclodextrin 2 wt%, N,N-dimethylformamide 0.02 wt% and water 93.58 wt%.

[0132] Preparation process:

[0133] (1) Add the polymer, n-octyltriethoxysilane mother liquor and silicon carbide nano-ceramic fiber into water according to the above ratio, and stir and mix them at 30° C. for 0.5 h to obtain a uniform prepolymer system;

[0134] (2) α-cyclodextrin and N,N-dimethylformamide are added to the above prepolymerization system and stirred thoroughly to obtain a pre-crosslinking system. The pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as D3).

[0135] The viscosity, gelling temperature (temperature of cross-linking reaction), gelling time (time of cross-linking reaction), and gelling viscosity (viscosity of D3 at gelling temperature) of the pre-cross-linking system are shown in Table 1.

[0136] D3 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0137] Comparative Example 4

[0138] Preparation raw materials: polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:2) 12% by weight, n-octyltriethoxysilane mother liquor 1.0% by weight, silicon carbide nanoceramic fiber 1.0% by weight, L-arginine 8% by weight, α-cyclodextrin 8% by weight, N,N-dimethylformamide 0.1% by weight and water 69.9% by weight.

[0139] Preparation process:

[0140] (1) Add the polymer, n-octyltriethoxysilane mother liquor and silicon carbide nano-ceramic fiber into water according to the above ratio, and stir and mix them at 30° C. for 0.5 h to obtain a uniform prepolymer system;

[0141] (2) L-arginine, α-cyclodextrin and N,N-dimethylformamide are added to the above prepolymerization system and stirred thoroughly to obtain a pre-crosslinking system. The obtained pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as D4).

[0142] The viscosity, gelling temperature (temperature of cross-linking reaction), gelling time (time of cross-linking reaction), and gelling viscosity (viscosity of D4 at gelling temperature) of the pre-cross-linking system are shown in Table 1.

[0143] D4 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0144] Comparative Example 5

[0145] Preparation materials: the same as those in Example 1.

[0146] Preparation process:

[0147] The method of Example 1 is followed, except that the polymer, n-octyltriethoxysilane mother liquor, silicon carbide nano-ceramic fiber, L-arginine, α-cyclodextrin and N,N-dimethylformamide are added into water, and the mixture is stirred and mixed at 30° C. for 0.5 h to obtain a mixed system, and then the obtained mixed system is subjected to a cross-linking reaction (reaction conditions are the same as those in Example 1), and other conditions are the same as those in Example 1 to obtain a temporary plugging agent (denoted as D5).

[0148] The viscosity, gelation temperature (crosslinking reaction temperature), gelation time (crosslinking reaction time), and gelation viscosity (viscosity of D5 at the gelation temperature) of the mixed system are shown in Table 1.

[0149] D5 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0150] Comparative Example 6

[0151] Preparation raw materials: polymer (polyacrylamide and terpolymer mixed in a molar ratio of 1:2) 4 wt%, n-octyltriethoxysilane mother liquor 0.2 wt%, silicon carbide nano-ceramic fiber 0.2 wt%, L-arginine 2 wt%, N,N-dimethylformamide 0.02 wt% and water 93.58 wt%.

[0152] Preparation process:

[0153] (1) Add the polymer, n-octyltriethoxysilane mother liquor and silicon carbide nano-ceramic fiber into water according to the above ratio, and stir and mix them at 30° C. for 0.5 h to obtain a uniform prepolymer system;

[0154] (2) L-arginine and N,N-dimethylformamide are added to the above prepolymerization system and the mixture is stirred and mixed to obtain a pre-crosslinking system. The pre-crosslinking system is then subjected to a crosslinking reaction to obtain a temporary plugging agent (denoted as D6).

[0155] The viscosity, gelling temperature (temperature of cross-linking reaction), gelling time (time of cross-linking reaction), and gelling viscosity (viscosity of D6 at gelling temperature) of the pre-cross-linking system are shown in Table 1.

[0156] D6 was stored under high temperature conditions, and the degradation time and residue rate after degradation were tested. The results of storage temperature, degradation time and residue rate are shown in Table 1.

[0157] Table 1

[0158]

[0159] Table 1

[0160]

[0161] As can be seen from Table 1, the gelling temperature of the temporary plugging agent prepared by the preparation method of the present invention is above 100°C, which is conducive to gelling at high-temperature positions in the formation. Under the conditions of high mineralization and the above-mentioned gelling temperature, the gelling viscosity of the obtained gel temporary plugging agent is adjustable in the range of 8000mPa·s to 50000mPa·s. Under the above-mentioned storage temperature conditions, the degradation time is suitable, showing excellent high temperature resistance, high salt resistance and temporary plugging performance. The residue rate after degradation is not higher than 5%, and can be as low as 0.5%, which is environmentally friendly. In particular, the polymer concentration in the preparation raw materials of Example 1 and Comparative Examples 1 to Comparative Examples 6 is the same (all 4 weight %). Under the same polymer concentration and the same gelling temperature conditions, the raw materials used in Comparative Example 1 do not contain n-octyltriethoxysilane mother liquor, and the raw materials used in Comparative Example 2 do not contain nano-ceramic fibers. The viscosity of the pre-crosslinked system formed is lower than that of Example 1, and the gelling viscosities of D1 and D2 are worse than S1, and the temporary plugging effect under high temperature and high mineralization is not as good as S1; Comparative Examples 3, 4 and 6 do not use the preparation raw material components or raw material component ratios in the method of the present invention, and the gelling viscosities of D3, D4 and D6 are worse than S1, and the temporary plugging effect under high temperature and high mineralization is not as good as S1; Comparative Example 5 does not use the preparation method of polycondensation first and then crosslinking, the gelling time is too short, and the gelling viscosity is worse than S1, and the temporary plugging effect under high temperature and high mineralization is not as good as S1.

[0162] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a temporary plugging agent, characterized in that: The method comprises: (1) first mixing a polymer, a mother solution of n-octyltriethoxysilane, nano-ceramic fibers and water to obtain a prepolymer system; (2) performing a second mixing of the prepolymer system, L-arginine, α-cyclodextrin and an auxiliary agent to obtain a pre-crosslinked system, and then performing a crosslinking reaction on the pre-crosslinked system to obtain a temporary plugging agent; Wherein, based on the total weight of the raw materials, the raw materials include: 1-10% of the polymer, 0.05-0.5% of the n-octyltriethoxysilane mother solution, 0.05-0.5% of the nano-ceramic fiber, 79-97% of water, 0.5-5% of L-arginine, 0.5-5% of α-cyclodextrin and 0.005-0.05% of the additive; The polymer includes polyacrylamide and a terpolymer; the terpolymer contains a structural unit A provided by an acrylamide monomer, a structural unit B provided by a 2-acrylamide-2-methylpropanesulfonic acid monomer, and a structural unit C provided by a vinyl pyrrolidone monomer; based on the total molar amount of each structural unit, in the terpolymer, the content of the structural unit B is 10-15 mol%, and the content of the structural unit C is 10-15 mol%; The conditions of the cross-linking reaction include: temperature of 120-180° C. and time of 4-50 hours.

2. The preparation method according to claim 1, wherein The weight ratio of the n-octyltriethoxysilane mother solution to the nano-ceramic fiber is 1:(0.5-2).

3. The preparation method according to claim 1 or 2, wherein The molar ratio of polyacrylamide: terpolymer is 1:(2-5).

4. The preparation method according to claim 3, wherein The number average molecular weight of the polyacrylamide is 500,000-5,000,000 g / mol, and the degree of hydrolysis is 10-15%; And / or, the number average molecular weight of the terpolymer is 1 million to 8 million g / mol, and the degree of hydrolysis is 10 to 15%.

5. The preparation method according to claim 1 or 2, wherein: The n-octyltriethoxysilane mother solution is an n-octyltriethoxysilane aqueous solution with a concentration of 0.5-1.5% by weight.

6. The preparation method according to claim 1 or 2, wherein: The nano-ceramic fiber is selected from at least one of alumina nano-ceramic fiber, silicon nitride nano-ceramic fiber, silicon carbide nano-ceramic fiber and boron nitride nano-ceramic fiber; And / or, the length of the nano ceramic fiber is 100-500 nm.

7. The preparation method according to claim 1 or 2, wherein: The auxiliary agent is selected from at least one of N,N-dimethylformamide, N,N-dimethylpropionamide, N-methyl-2-pyrrolidone, N-ethylpyrrolidone and N-methylpyrrolidone.

8. The preparation method according to claim 1 or 2, wherein: The first mixing conditions include: temperature of 20-80° C. and time of 10-60 min.

9. A temporary plugging agent prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the preparation method according to any one of claims 1 to 8 or the temporary plugging agent according to claim 9 in the development of high-temperature oil and gas reservoirs or heavy oil reservoirs.

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