Micro-crosslinking anti-gas-channeling agent as well as preparation method and application thereof

Abstract

The invention provides a micro-crosslinking anti-gas-channeling agent as well as a preparation method and application thereof. The micro-crosslinking anti-gas-channeling agent is prepared from the following raw materials: polybutadiene, styrene, a modified monomer and a crosslinking agent, the modified monomers comprise sulfonic acid group-containing unsaturated monomers and salts thereof, and carboxyl group-containing unsaturated monomers and salts thereof; based on 100% of the total molar weight of the polybutadiene, the styrene and the modified monomer, the molar percentage content of the modified monomer is 22-42%. The micro-crosslinking anti-gas-channeling agent has an excellent anti-gas-channeling effect, is resistant to high temperature and salt, and can obviously improve the anti-gas-channeling effect of cement paste under the condition of a small addition amount, so that the cement paste comprising the micro-crosslinking anti-gas-channeling agent is good in anti-gas-channeling effect, wide in applicable temperature range, and suitable for various types of well cementation; and for well cementation of a high-risk gas well with serious gas channeling potential, a good gas channeling prevention effect is also achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oilfield exploitation, and particularly relates to a micro-crosslinking gas channeling prevention agent, a preparation method and application thereof. BACKGROUND

[0002] In the process of oilfield development, oil well cement is a key material for plugging and fixing the wall of oil and gas well. However, due to the complexity and variability of formation conditions, the traditional cement often cannot meet all plugging requirements. Especially when the oil well depth is large, the formation pressure is uneven or the formation rock properties differ greatly, the plugging effect of the cement will be seriously affected, resulting in reduced sealing of the oil well. During the cement slurry construction process, gas channeling is a common problem. After gas channeling occurs, it will have many adverse effects on the exploitation of oil and gas fields, such as affecting the exploitation efficiency and production safety of the oil well, and even causing the oil well to be scrapped, so it is of great significance to strengthen the research on cement slurry gas channeling prevention.

[0003] There are many factors affecting gas channeling, such as formation and formation fluid characteristics, displacement efficiency, hydration of cement slurry, and cementing conditions of cement and formation and casing; uneven formation pressure, low displacement efficiency, poor cementing quality, and cement slurry weight loss can all cause gas channeling; especially in deep well cementing, due to high formation pressure, high temperature, and complex well structure, gas channeling is more likely to occur.

[0004] At present, the main measures to prevent gas channeling include improving cementing technology and using gas channeling prevention cement slurry; for example, using multi-stage setting cement slurry channeling prevention technology; using mechanical methods to block gas channeling, such as annulus back pressure, casing external packer, etc.; or obtaining gas channeling prevention cement slurry by externally adding gas channeling prevention agent. Traditional gas channeling prevention agents mainly include latex gas channeling prevention agent and polyvinyl alcohol. However, the latex gas channeling prevention agent has a large addition amount, and when the storage temperature is low, it will break emulsion, affecting the gas channeling prevention effect; and polyvinyl alcohol cannot be used in high temperature and high salt environments.

[0005] Therefore, developing a gas channeling prevention agent that can effectively prevent gas channeling and has good high temperature resistance and salt resistance, and is also applicable to high-risk gas well cementing with serious gas channeling potential, such as high temperature and ultra-high pressure gas wells, long open hole easy leakage wells, etc., is a problem to be solved in the field. SUMMARY

[0006] In view of the deficiencies in the prior art, the purpose of the present application is to provide a micro-crosslinking gas channeling prevention agent, a preparation method and application thereof. The micro-crosslinking gas channeling prevention agent has excellent gas channeling prevention effect, and is resistant to high temperature and salt. With less addition amount, the gas channeling prevention effect of the cement slurry can be significantly improved, so that the cement slurry containing the micro-crosslinking gas channeling prevention agent has good gas channeling prevention effect, wide applicable temperature range, and can be applied to various types of cementing. For high-risk gas well cementing with serious gas channeling potential, it also has good gas channeling prevention effect.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] In the first aspect, the present application provides a micro-crosslinking gas channeling prevention agent, raw materials for preparing the micro-crosslinking gas channeling prevention agent include polybutadiene, styrene, modified monomer and crosslinking agent; the modified monomer includes unsaturated monomer containing sulfonic acid group and its salt and unsaturated monomer containing carboxyl group and its salt; the mole percentage of the modified monomer is 22-42% based on the total mole of polybutadiene, styrene and modified monomer.

[0009] In the present application, the micro-crosslinking gas channeling prevention agent has a space network structure, so that the cement slurry has a certain thixotropy, and is beneficial to shorten the static gel strength transition time of the cement slurry, thereby improving the gas channeling prevention effect; by using the modified monomer with a specific composition to modify the butadiene-styrene latex formed by polybutadiene and styrene, it is beneficial to reduce the fluid loss of the cement slurry, shorten the thickening time and static gel strength transition time of the cement slurry, and further improve the gas channeling prevention effect of the cement slurry; at the same time, the introduction of functional groups such as carboxyl and sulfonic acid groups in the molecular chain is beneficial to improve the high temperature resistance and salt resistance of the cement slurry, so that the cement slurry also has good gas channeling prevention effect in high temperature and high salt deep well cementing; in general, by selecting specific raw materials, the cement slurry including the micro-crosslinking gas channeling prevention agent has the advantages of moderate consistency, light thixotropy, low fluid loss, non-retarding, no inversion, leak-proof aid, gas channeling prevention, high strength, etc.

[0010] In the present application, the mole percentage of the modified monomer is 22-42%, for example, it can be 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, etc.

[0011] Preferably, the mass ratio of the unsaturated monomer containing sulfonic acid group and its salt and the unsaturated monomer containing carboxyl group and its salt is (0.2-2.5):1, wherein the specific value in (0.2-2) can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.4, 2.5, etc., and preferably (0.5-2):1.

[0012] In the present application, the unsaturated monomer containing sulfonic acid group and its salt includes unsaturated monomer containing sulfonic acid group and / or salt of unsaturated monomer containing sulfonic acid group; the unsaturated monomer containing carboxyl group and its salt includes unsaturated monomer containing carboxyl group and / or salt of unsaturated monomer containing carboxyl group.

[0013] Preferably, the sulfonic acid group-containing unsaturated monomer and salts thereof include any one or a combination of 2-acrylamido-2-methyl acrylate, sodium vinyl sulfonate or sodium p-styrene sulfonate, preferably a combination of 2-acrylamido-2-methyl acrylate and sodium p-styrene sulfonate.

[0014] Preferably, the mass ratio of 2-acrylamido-2-methyl acrylate and sodium p-styrene sulfonate is (0.8-2.5):1, wherein the specific value in (0.8-2.5) may be 0.8, 1, 1.2, 1.22, 1.24, 1.26, 1.28, 1.3, 1.32, 1.34, 1.36, 1.38, 1.4, 1.42, 1.44, 1.46, 1.48, 1.5, 1.52, 1.54, 1.56, 1.58, 1.6, 1.62, 1.64, 1.66, 1.68, 1.7, 1.72, 1.75, 1.78, 1.8, 1.82, 1.85, 1.88, 1.9, 1.92, 1.95, 1.98, 2, 2.1, 2.15, 2.2, 2.3, 2.4, 2.5, etc., and further preferably (1.2-2.2):1.

[0015] In the present application, the sulfonic acid group-containing unsaturated monomer and salts thereof are selected from a combination of 2-acrylamido-2-methyl acrylate and sodium p-styrene sulfonate, and the mass ratio of the two is within the above range, so that the cement slurry has good high-temperature resistance and salt resistance; and the problem of easy hydrolysis of amide groups at high temperature is reduced.

[0016] Preferably, the carboxyl group-containing unsaturated monomer and salts thereof include acrylic monomers and / or sodium humate.

[0017] Preferably, the mass ratio of the acrylic monomers and sodium humate is 1:(0.1-1.2), wherein the specific value in (0.1-1.2) may be 0.1, 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, 0.56, 0.58, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9, 0.92, 0.95, 0.98, 1, 1.1, 1.2, etc., and further preferably (0.3-0.8).

[0018] In the present application, it is further preferred that the acrylic monomers and sodium humate are compounded, and the mass ratio of the two is within the above range, which improves the anti-gas channeling effect of the cement slurry and improves its salt resistance.

[0019] Preferably, the acrylic monomer comprises acrylic acid and / or methacrylic acid.

[0020] Preferably, the mass percentage content of the crosslinking agent is 0.25-0.45%, for example, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, etc., based on the total mass of the polybutadiene, styrene and modified monomer being 100%.

[0021] Preferably, the crosslinking agent comprises N,N'-methylenebisacrylamide.

[0022] Preferably, the molar ratio of the polybutadiene to the styrene is 1:(2-9), wherein the specific value in (2-9) can be 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, etc.

[0023] Preferably, the main chain structure of the micro-crosslinking gas channeling prevention agent is a polybutadiene structural unit, the side chain structure is a copolymer structural unit formed by the styrene and the modified monomer, the styrene and the polybutadiene are connected by a chemical bond; and the micro-crosslinking gas channeling prevention agent has a crosslinking network structure.

[0024] In the present application, the micro-crosslinking gas channeling prevention agent has a core-shell structure, the styrene and the polybutadiene serve as a core layer, and the modified monomer serves as a shell layer.

[0025] Preferably, the preparation raw material further comprises an initiator and / or an emulsifier.

[0026] Preferably, the mass percentage content of the initiator and the emulsifier is independently 1-5%, for example, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, etc., based on the total mass of the polybutadiene, styrene and modified monomer being 100%.

[0027] In the present application, the initiator comprises at least one of an azo initiator, a peroxide initiator or an oxidation-reduction initiation system; the azo initiator comprises but is not limited to azobisdimethylamidinum hydrochloride (AIBA), azobisdimethylimidazoline hydrochloride (AIBI), etc.; the peroxide initiator comprises but is not limited to hydrogen peroxide, ammonium persulfate, potassium persulfate, etc.

[0028] In the present application, the emulsifier includes but is not limited to alkyl sulfate (such as sodium dodecyl sulfate SDS), alkyl sulfonate, stearate, quaternary ammonium salt, polyoxyethylene ether, polyoxypropylene ether, etc.

[0029] In a second aspect, the present application provides a preparation method of the micro-crosslinking gas channeling prevention agent according to the first aspect, the preparation method comprising:

[0030] (1) reacting styrene with a formula amount of 40-60% (for example, it can be 40%, 45%, 50%, 55%, 60%, etc.) with modified monomer with a formula amount of 40-60% (for example, it can be 40%, 45%, 50%, 55%, 60%, etc.) to obtain a seed emulsion;

[0031] (2) mixing and dispersing the remaining styrene with polybutadiene to obtain a monomer microdroplet emulsion; then mixing and reacting the monomer microdroplet emulsion, the remaining modified monomer, the crosslinking agent, and the seed emulsion obtained in step (1) to obtain the micro-crosslinking gas channeling prevention agent.

[0032] Preferably, the raw materials of the reaction in step (1) further include an aqueous emulsifier solution and an initiator.

[0033] In the present application, the content of the emulsifier and the initiator in step (1) is independently 20-50% of the formula amount, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0034] Preferably, the temperature of the reaction in step (1) is 60-80°C, for example, it can be 60°C, 65°C, 70°C, 75°C, 80°C, etc.; the time is 0.5-2h, for example, it can be 0.5h, 0.6h, 0.8h, 1h, 1.5h, 2h, etc.

[0035] Preferably, the raw materials of the mixing and dispersing in step (2) further include an aqueous emulsifier solution.

[0036] In the present application, the content of the emulsifier in step (2) is 50-80% of the formula amount, for example, it can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc.

[0037] Preferably, the mixing and dispersing in step (2) is carried out under the condition of a high-pressure homogenizer or ultrasonic, the power of the ultrasonic is 500-1500W, for example, it can be 500W, 550W, 600W, 650W, 700W, 750W, 800W, 850W, 900W, 950W, 1000W, 1100W, 1200W, 1300W, 1400W, 1500W, etc.; the time is 30-60min, for example, it can be 30min, 35min, 40min, 45min, 50min, 55min, 60min, etc.

[0038] Preferably, the raw material of the reaction in step (2) further comprises an initiator.

[0039] In the present application, the content of the initiator in step (2) is 50-80% of the formula amount, for example, it can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc.

[0040] Preferably, the temperature of the reaction in step (2) is 60-80℃, for example, it can be 60℃, 65℃, 70℃, 75℃, 80℃, etc.; the time is 3-8h, for example, it can be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.7h, 7h, 7.5h, 8h, etc.

[0041] In the present application, the reaction in step (2) comprises adding the monomer microemulsion, the mixture of the remaining modified monomer and the crosslinking agent into the seed emulsion respectively, the dropping time is 1-3h, and the reaction continues for 2-5h after the dropping is completed.

[0042] In the present application, the reactions in steps (1) and (2) are both carried out under weak alkaline conditions, and the pH value of the solution can be adjusted by adding alkali (such as sodium hydroxide).

[0043] In a third aspect, the present application provides an oil well cement, which comprises cement, the micro-crosslinking gas channeling prevention agent according to the first aspect, and water.

[0044] Preferably, the mass of the micro-crosslinking gas channeling prevention agent in the oil well cement is 3-5% BWOC, for example, it can be 3% BWOC, 3.1% BWOC, 3.2% BWOC, 3.3% BWOC, 3.4% BWOC, 3.5% BWOC, 3.6% BWOC, 3.7% BWOC, 3.8% BWOC, 3.9% BWOC, 4% BWOC, 4.1% BWOC, 4.2% BWOC, 4.3% BWOC, 4.4% BWOC, 4.5% BWOC, 4.6% BWOC, 4.7% BWOC, 4.8% BWOC, 4.9% BWOC, 5% BWOC, etc.

[0045] In the present application, if the addition amount of the micro-crosslinking gas channeling prevention agent is too small, the fluid loss is high, and the gas channeling prevention effect is poor; if the addition amount is too high, the consistency of the cement slurry is high.

[0046] In the present application, “% BWOC” refers to the percentage of the dry cement ash weight.

[0047] Preferably, the cement comprises G-grade cement.

[0048] In the present application, the water content accounts for 30-60% of the mass of the cement, for example, can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc.

[0049] In the present application, the oil well cement further comprises other additives; the other additives include but are not limited to density adjuster, dispersant, fluid loss additive, retarder, defoaming agent, etc.; the density adjuster is a weighting agent, and the weighting agent includes at least one of barite, iron ore powder, activated iron ore powder, manganese ore powder, calcium carbonate, barium carbonate or galena powder; the dispersant includes but is not limited to one or more of polyether type polycarboxylic acid, polyester type polycarboxylic acid, ester ether complex polycarboxylic acid, melamine formaldehyde resin, calcium lignosulfonate, sodium lignosulfonate, sodium hexametaphosphate; the fluid loss additive includes but is not limited to at least one of carboxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl hydroxyethyl cellulose; the retarder includes but is not limited to at least one of organic phosphate, lignosulfonate, sulfonated tannin, sodium tannate or tartaric acid; the defoaming agent includes but is not limited to at least one of silicone defoaming agent and high molecular polyether defoaming agent.

[0050] In the present application, the mass of the other additives accounts for 0.5-10% of the mass of the cement, for example, can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0051] The numerical range in the present application not only includes the point values listed above, but also includes any point values between the above numerical ranges that are not listed, and the specific point values included in the range are not listed due to the length and for the sake of simplicity.

[0052] Compared with the prior art, the present application has the following beneficial effects:

[0053] The micro-crosslinking gas channeling prevention agent provided by the present application has excellent gas channeling prevention effect and is resistant to high temperature and salt; the oil well cement slurry including the same has appropriate consistency and certain thixotropy, which is beneficial to prevent leakage; the slurry has small water loss, adjustable thickening time, good gas channeling prevention effect, good high temperature and salt resistance, stable slurry body, no free liquid, no inverted thickening, and high strength, and can be applied to various types of well cementing. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 The water loss curve of the cement slurry including the gas channeling prevention agent provided by Example 1 with the increase of the content of the gas channeling prevention agent is shown in the figure. DETAILED DESCRIPTION

[0055] The technical solutions of the present application will be further described by specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0056] Example 1

[0057] The present example provides a micro-crosslinking gas channeling prevention agent, the preparation raw materials of which include 12% of polybutadiene, 56% of styrene and 32% of modified monomers, based on 100% of the total moles of polybutadiene, styrene and modified monomers; the modified monomers include unsaturated monomers containing sulfonic acid groups and their salts and unsaturated monomers containing carboxyl groups and their salts in a mass ratio of 1:1; the unsaturated monomers containing sulfonic acid groups and their salts include 2-acrylamido-2-methyl acrylate sulfonic acid and sodium p-styrene sulfonate in a mass ratio of 1.6:1; the unsaturated monomers containing carboxyl groups and their salts include acrylic acid and sodium humate in a mass ratio of 1:0.5; the preparation raw materials further include a crosslinking agent (N,N'-methylene bisacrylamide, with a mass of 0.32% of the total mass of polybutadiene, styrene and modified monomers), an initiator (ammonium persulfate, with a mass of 1% of the total mass of polybutadiene, styrene and modified monomers) and an emulsifier (SDS, with a mass of 2% of the total mass of polybutadiene, styrene and modified monomers).

[0058] The present example provides a preparation method of the micro-crosslinking gas channeling prevention agent, which specifically includes the following steps:

[0059] (1) Mix the modified monomers in a formula amount of 45% with an aqueous SDS solution in a formula amount of 40%, then add the styrene in a formula amount of 50% and the initiator in a formula amount of 40% to the mixture, and react at 70°C for 1h to obtain a seed emulsion;

[0060] (2) Mix the remaining styrene with polybutadiene, and add the remaining aqueous SDS solution to the mixture and stir at high speed to disperse the mixture uniformly to obtain a monomer microdroplet emulsion; then add the monomer microdroplet emulsion, the remaining modified monomers and the crosslinking agent to the seed emulsion obtained in step (1) respectively under constant temperature conditions at 70°C, the dropping time is 2h, and after the dropping is completed, continue to react for 3h to obtain the micro-crosslinking gas channeling prevention agent.

[0061] Example 2

[0062] The embodiment provides a micro-crosslinking gas channeling prevention agent, raw materials for preparing the micro-crosslinking gas channeling prevention agent including 15% of polybutadiene, 60% of styrene and 25% of modified monomers, with the total mole amount of the polybutadiene, the styrene and the modified monomers being 100%; the modified monomers including 0.5:1 of unsaturated monomers containing sulfonic acid groups and salts thereof and unsaturated monomers containing carboxyl groups and salts thereof by mass ratio; the unsaturated monomers containing sulfonic acid groups and salts thereof including 1.3:1 of 2-acrylamido-2-methyl acrylate sulfonic acid and sodium p-styrene sulfonate by mass ratio; the unsaturated monomers containing carboxyl groups and salts thereof including 1:0.3 of acrylic acid and sodium humate by mass ratio; and the raw materials further including a crosslinking agent (N,N'-methylene bisacrylamide, with the mass of the crosslinking agent being 0.26% of the total mass of the polybutadiene, the styrene and the modified monomers), an initiator (ammonium persulfate, with the mass of the initiator being 1.5% of the total mass of the polybutadiene, the styrene and the modified monomers) and an emulsifier (SDS, with the mass of the emulsifier being 2.5% of the total mass of the polybutadiene, the styrene and the modified monomers).

[0063] The embodiment provides a preparation method of the micro-crosslinking gas channeling prevention agent, and specific steps are the same as those in the embodiment 1.

[0064] Embodiment 3

[0065] The embodiment provides a micro-crosslinking gas channeling prevention agent, raw materials for preparing the micro-crosslinking gas channeling prevention agent including 15% of polybutadiene, 60% of styrene and 25% of modified monomers, with the total mole amount of the polybutadiene, the styrene and the modified monomers being 100%; the modified monomers including 0.5:1 of unsaturated monomers containing sulfonic acid groups and salts thereof and unsaturated monomers containing carboxyl groups and salts thereof by mass ratio; the unsaturated monomers containing sulfonic acid groups and salts thereof including 1.3:1 of 2-acrylamido-2-methyl acrylate sulfonic acid and sodium p-styrene sulfonate by mass ratio; the unsaturated monomers containing carboxyl groups and salts thereof including 1:0.3 of acrylic acid and sodium humate by mass ratio; and the raw materials further including a crosslinking agent (N,N'-methylene bisacrylamide, with the mass of the crosslinking agent being 0.26% of the total mass of the polybutadiene, the styrene and the modified monomers), an initiator (ammonium persulfate, with the mass of the initiator being 1.5% of the total mass of the polybutadiene, the styrene and the modified monomers) and an emulsifier (SDS, with the mass of the emulsifier being 2.5% of the total mass of the polybutadiene, the styrene and the modified monomers).

[0066] The embodiment provides a preparation method of the micro-crosslinking gas channeling prevention agent, and specific steps are the same as those in the embodiment 1.

[0067] Embodiment 4

[0068] The embodiment provides a micro-crosslinking gas channeling prevention agent, which is different from the embodiment 1 only in that the total mass of the unsaturated monomers containing sulfonic acid groups and salts thereof and the unsaturated monomers containing carboxyl groups and salts thereof is unchanged, the mass ratio is 0.2:1, and the other raw materials, the ratio, the amount and the preparation method are the same as those in the embodiment 1.

[0069] Example 5

[0070] The present example provides a micro-crosslinking gas channeling prevention agent, which is different from Example 1 only in that the total mass of the unsaturated monomer containing sulfonic acid group and its salt and the unsaturated monomer containing carboxyl group and its salt is unchanged, the mass ratio is 2.5:1, and the other raw materials, the ratio, the amount, and the preparation method are the same as those of Example 1.

[0071] Example 6

[0072] The present example provides a micro-crosslinking gas channeling prevention agent, which is different from Example 1 only in that the total mass of the 2-acrylamido-2-methyl acrylate sulfonic acid and sodium p-styrene sulfonate is unchanged, the mass ratio is 0.8:1, and the other raw materials, the amount, and the preparation method are the same as those of Example 1.

[0073] Example 7

[0074] The present example provides a micro-crosslinking gas channeling prevention agent, which is different from Example 1 only in that the total mass of the 2-acrylamido-2-methyl acrylate sulfonic acid and sodium p-styrene sulfonate is unchanged, the mass ratio is 2.5:1, and the other raw materials, the amount, and the preparation method are the same as those of Example 1.

[0075] Example 8

[0076] The present example provides a micro-crosslinking gas channeling prevention agent, which is different from Example 1 only in that the total mass of the acrylic acid and sodium humate is unchanged, the mass ratio is 1:1.2, and the other raw materials, the amount, and the preparation method are the same as those of Example 1.

[0077] Example 9

[0078] The present example provides a micro-crosslinking gas channeling prevention agent, which is different from Example 1 only in that the total mass of the acrylic acid and sodium humate is unchanged, the mass ratio is 1:0.1, and the other raw materials, the amount, and the preparation method are the same as those of Example 1.

[0079] Example 10

[0080] The present example provides a micro-crosslinking gas channeling prevention agent, which is different from Example 1 only in that the mass of the unsaturated monomer containing sulfonic acid group and its salt is unchanged, and there is no sodium p-styrene sulfonate; the mass of the unsaturated monomer containing carboxyl group and its salt is unchanged, and there is no sodium humate, and the other raw materials, the amount, and the preparation method are the same as those of Example 1.

[0081] Example 11

[0082] This example provides a micro-crosslinking gas channeling preventing agent, which is different from Example 1 only in that the amount of the crosslinking agent is reduced so that the mass of the crosslinking agent is 0.2% of the total mass of the polybutadiene, styrene and modified monomer, and the other raw materials, amounts and preparation method are the same as in Example 1.

[0083] Example 12

[0084] This example provides a micro-crosslinking gas channeling preventing agent, which is different from Example 1 only in that the amount of the crosslinking agent is reduced so that the mass of the crosslinking agent is 0.5% of the total mass of the polybutadiene, styrene and modified monomer, and the other raw materials, amounts and preparation method are the same as in Example 1.

[0085] Comparative Example 1

[0086] This comparative example provides a gas channeling preventing agent, which is different from Example 1 only in that the crosslinking agent is not included in the preparation raw materials, and the other raw materials, amounts and preparation method are the same as in Example 1.

[0087] Comparative Example 2

[0088] This comparative example provides a micro-crosslinking gas channeling preventing agent, which is different from Example 1 only in that the mole percentage content of the modified monomer is 15% based on 100% of the total mole amount of the polybutadiene, styrene and modified monomer, and the other raw material types, proportions, amounts and preparation method are the same as in Example 1.

[0089] Comparative Example 3

[0090] This comparative example provides a micro-crosslinking gas channeling preventing agent, which is different from Example 1 only in that the mole percentage content of the modified monomer is 48% based on 100% of the total mole amount of the polybutadiene, styrene and modified monomer, and the other raw material types, proportions, amounts and preparation method are the same as in Example 1.

[0091] Comparative Example 4

[0092] This comparative example provides a micro-crosslinking gas channeling preventing agent, which is different from Example 1 only in that the acrylic acid and sodium humate with a mass ratio of 1:0.5 are replaced by acrylamide and N,N'-dimethylacrylamide with a mass ratio of 1:0.5, and the other raw material types, proportions, amounts and preparation method are the same as in Example 1.

[0093] Performance test

[0094] 1. Test the effect of the gas channeling preventing agent on the fluid loss of oil well cement slurry

[0095] Oil well cement slurry formula: G-grade cement, anti-gas channeling agent and water, the total mass of the anti-gas channeling agent and water is 44% of the mass of the G-grade cement; the anti-gas channeling agent is the anti-gas channeling agent provided in Examples 1-12 and Comparative Examples 1-4, and the water loss of the cement slurry at 80℃ is tested; the testing method comprises: referring to GB / T 19139 (10.1-10.10);

[0096] As shown in FIG. 1, the change curve of the water loss of the cement slurry containing the anti-gas channeling agent provided in Example 1 with the increase of the content of the anti-gas channeling agent is Figure 1 Figure 1 It can be seen that the anti-gas channeling agent provided in the application can effectively reduce the water loss of the cement slurry, and when the addition amount is about 3% BWOC, the water loss of the cement slurry can be controlled to be less than 50 mL, the anti-gas channeling effect is good, and when the addition amount is less than 2% BWOC, the water loss is large, and the anti-gas channeling effect is poor.

[0097] 2, Test the effect of the anti-gas channeling agent on the rheological property of the cement slurry

[0098] Oil well cement slurry formula: G-grade cement, anti-gas channeling agent and water, the total mass of the anti-gas channeling agent and water is 44% of the mass of the G-grade cement; the anti-gas channeling agent is the anti-gas channeling agent provided in Examples 1-12 and Comparative Examples 1-4, and the shear value of the cement slurry at 80℃ and different rotation speeds (3rpm, 6rpm, 100rpm, 200rpm, 300rpm in turn) is tested by using a rotary viscometer, and the consistency coefficient K and the rheological index n of the cement slurry are calculated;

[0099] Wherein, n = 2.096 x lg (θ 300 / θ 100 ); K = 0.511 x θ 300 / 511 n , θ is the viscometer reading;

[0100] The plastic viscosity, dynamic shear force and static shear force at different times are tested according to GB / T 19139;

[0101] Taking the anti-gas channeling agent provided in Example 1 as an example, the rheological property parameters of the oil well cement under different anti-gas channeling agent contents are shown in Table 1 (wherein, Φ represents the shear value at different rotation speeds, for example, Φ3 represents the shear value at a rotation speed of 3rpm).

[0102] 3, Test the effect of the anti-gas channeling agent on the thickening property of the cement slurry

[0103] The thickening time of the oil well cement slurry with different formulas at different temperatures is tested according to the method of GB / T 19139, and the specific test results are shown in Table 2.

[0104] Wherein, the formulas of different cement slurries are as follows, and the anti-gas channeling agent is provided in Example 1 (marked as GWT-200L).​

[0105] GWY-500S, GWR-200L, GWR-300L are products of Well Cementing Company of China Great Wall Drilling Engineering Co., Ltd., wherein GWY-500S is a high-temperature-resistant strength-decay material, and the standard number executed is Q / GWC 0019-2021; GWR-200L and GWR-300L are oil well cement high-temperature-resistant retarders, and the standard number executed is Q / GWC 0015-2020.

[0106] 1#: G-grade cement + 3.5% GWT-200L + 40.5% water;

[0107] 2#: G-grade cement + 3.5% GWT-200L + 40.3% water + 0.2% GWR-200L;

[0108] 3#: G-grade cement + 35% GWY-500S + 5% GWT-200L + 53.7% water + 0.7% GWR-200L;

[0109] 4#: G-grade cement + 35% GWY-500S + 5% GWT-200L + 53.4% water + 1.0% GWR-200L;

[0110] 5#: G-grade cement + 35% GWY-500S + 5% GWT-200L + 52.4% water + 2.0% GWR-300L;

[0111] 6#: G-grade cement + 35% GWY-500S + 5% GWT-200L + 51.9% water + 2.5% GWR-300L;

[0112] 7#: G-grade cement + 35% GWY-500S + 5% GWT-200L + 51.4% water + 3.0% GWR-300L.

[0113] 4, Test of cement slurry strength

[0114] The above 1# cement slurry is cured at low temperature for 24h and 48h, and the strength of the cement slurry is tested according to the method of GB / T 19139(7.5), and the test results are shown in Table 3.

[0115] 5, Anti-gas channeling performance of cement slurry

[0116] According to the 1# cement slurry formula, the anti-gas channeling agents are respectively the anti-gas channeling agents provided by the examples 1-12 and the comparative examples 1-4 of the present application, the anti-gas channeling performance of the cement slurry at different temperatures is tested according to the method of SY / T 5504.5 Appendix D, and the performance coefficient SPN of the cement slurry is calculated;

[0117] The calculation formula is SPN = QAPI X A; wherein, Q represents API fluid loss, mL; A = 0.1826 x [(T 100Bc ) 1 / 2 -(T 30Bc ) 1 / 2 ], T 100Bc is the time for the consistency to reach 100Bc, min; T 30Bc is the time for the consistency to reach 30Bc, min.

[0118] The lower the SPN value, the better the anti-gas channeling effect, wherein, the SPN value less than 5 has strong anti-gas channeling capacity; greater than or equal to 5 has general anti-gas channeling capacity, and the level is medium; the test results are shown in Table 4 (the test temperature is 50℃) and Table 5 (the test temperature is 80℃) respectively.

[0119] Table 1

[0120]

[0121] It can be seen from Table 1 that the amount of the anti-gas channeling agent should not be more than 4%, otherwise the viscosity of the cement slurry is too high, which is not conducive to pumping.

[0122] Table 2

[0123]

[0124] It can be seen from the results in Table 2 that the cement slurry including the micro-crosslinking anti-gas channeling agent provided by the application has adjustable thickening time, and does not have the phenomenon of inversion.

[0125] Table 3

[0126] Curing temperature (°C) 24h strength (MPa) 48h strength (MPa) 50 21.9 26.1 80 30.5 31.1

[0127] It can be seen from Table 3 that the micro-crosslinking anti-gas channeling agent including the application has normal strength development when cured at low temperature, and has a high compressive strength after curing for 24h, which is greater than 20MPa.

[0128] Table 4

[0129]

[0130]

[0131] Table 5

[0132] T 30Bc (min)]]> T 100Bc (min)]]> Q API (mL)]]> A SPN Example 1 98 107 41 0.081 3.32

[0133] It can be seen from Table 4 that the micro-crosslinking anti-gas channeling agent provided by the application has a short thickening transition time, wherein, T 100Bc ≤165min, T 30Bc≤ 154 min; API fluid loss ≤ 54 mL, SPN value < 5, minimum even lower than 3, with strong gas channeling prevention ability.

[0134] As can be seen from Comparative Examples 1-4, the anti-gas channeling agent with the specific micro-crosslinking structure of the present application, or the content or composition of the modified monomer is not within the range defined by the present application, the thickening transition time of the obtained anti-gas channeling agent is prolonged, and / or the API fluid loss is increased, eventually resulting in an increase in the SPN coefficient and a decrease in the anti-gas channeling ability.

[0135] In addition, as can be seen from Tables 4 and 5, the cement slurry including the micro-crosslinking anti-gas channeling agent provided by the present application has strong anti-gas channeling ability at different temperatures.

[0136] The applicant states that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by any person skilled in the art, and all such changes or replacements fall within the protection scope and disclosure scope of the present application.

Claims

1. A micro-crosslinking gas channeling prevention agent, characterized by comprising: The preparation raw materials of the micro-crosslinking gas channeling prevention agent include polybutadiene, styrene, modified monomer and crosslinking agent; The modified monomer includes unsaturated monomer containing sulfonic acid group and its salt and unsaturated monomer containing carboxyl group and its salt; The mole percentage of the modified monomer is 22-42% based on 100% of the total mole amount of polybutadiene, styrene and modified monomer.

2. The micro-crosslinking gas channeling preventive agent according to claim 1, wherein The mass ratio of the unsaturated monomer containing sulfonic acid group and its salt and the unsaturated monomer containing carboxyl group and its salt is (0.2-2.5):1, preferably (0.5-2):1; Preferably, the unsaturated monomer containing sulfonic acid group and its salt includes any one or combination of at least two of 2-acrylamido-2-methyl acrylate sulfonic acid, sodium vinyl sulfonate or sodium p-styrene sulfonate, preferably the combination of 2-acrylamido-2-methyl acrylate sulfonic acid and sodium p-styrene sulfonate; Preferably, the mass ratio of 2-acrylamido-2-methyl acrylate sulfonic acid and sodium p-styrene sulfonate is (0.8-2.5):1, further preferably (1.2-2.2):

1.

3. The micro-crosslinking gas channeling preventive agent according to claim 1 or 2, characterized by, The unsaturated monomer containing carboxyl group and its salt includes acrylic monomer and / or sodium humate; Preferably, the mass ratio of the acrylic monomer and sodium humate is 1:(0.1-1.2), further preferably (0.3-0.8); Preferably, the acrylic monomer includes acrylic acid and / or methacrylic acid.

4. The micro-crosslinking gas channeling preventive agent according to any one of claims 1 to 3, characterized by, The mass of the crosslinking agent is 0.25-0.45% of the total mass of polybutadiene, styrene and modified monomer; Preferably, the crosslinking agent includes N,N'-methylene bisacrylamide; Preferably, the mole ratio of polybutadiene to styrene is 1:(2-9); Preferably, the main chain structure of the micro-crosslinking gas channeling prevention agent is polybutadiene structural unit, the side chain structure is copolymer structural unit formed by styrene and modified monomer, the styrene and polybutadiene are connected by chemical bond; and the micro-crosslinking gas channeling prevention agent has crosslinking network structure.

5. The micro-crosslinking gas channeling preventive agent according to any one of claims 1 to 4, characterized by, The preparation raw materials further include initiator and / or emulsifier; Preferably, the mass of the initiator and emulsifier is independently 1-5% of the total mass of polybutadiene, styrene and modified monomer.

6. A method for preparing the micro-crosslinking gas channeling preventive agent according to any one of claims 1 to 5, characterized by, The preparation method includes: (1) reacting formula amount 40-60% of styrene with formula amount 40-60% of modified monomer to obtain seed emulsion; (2) mixing and dispersing the remaining styrene and polybutadiene to obtain monomer microdroplet emulsion; then mixing and reacting the monomer microdroplet emulsion, the remaining modified monomer, the crosslinking agent and the seed emulsion obtained in step (1) to obtain the micro-crosslinking gas channeling prevention agent.

7. The production method according to claim 6, wherein The raw materials of the reaction in step (1) further include aqueous emulsifier solution and initiator; Preferably, the temperature of the reaction in step (1) is 60-80℃, and the time is 0.5-2h.

8. The production method according to claim 6 or 7, characterized by, The raw materials of the mixing and dispersing in step (2) further include aqueous emulsifier solution; Preferably, the raw materials of the reaction in step (2) further include initiator; Preferably, the temperature of the reaction in step (2) is 60-80℃, and the time is 3-8h.

9. An oil well cement characterized by, The oil well cement includes cement, the micro-crosslinking gas channeling prevention agent according to any one of claims 1-5 and water.

10. The oil well cement of claim 9, wherein, The mass of the micro-crosslinking gas channeling preventing agent in the oil well cement is 3-5% BWOC.

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