Fully-coated coating agent for drilling fluid and preparation method of fully-coated coating agent

Abstract

The invention relates to the technical field of coating agents for drilling fluids, in particular to a fully-coated coating agent for drilling fluids and a preparation method thereof.The fully-coated coating agent for drilling fluids is obtained through the following steps that an acrylic acid solution, a sodium hydroxide solution, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide are mixed, and a first mixed material is obtained; a maleic anhydride solution, a sodium hydroxide solution and N-vinyl pyrrolidone are mixed to obtain a second mixed material, the first mixed material and the second mixed material are mixed, then 3-butene-1-ol, ammonium persulfate and azodiisobutyronitrile are added, and a polymerization reaction is carried out to obtain the high-temperature-resistant anti-aging agent. The fully-coated coating agent for the drilling fluid can be firmly adsorbed on the surface of clay in drilling cuttings through more adsorption groups, can be better stretched in fresh water or the drilling fluid containing saline water, tightly wraps the drilling cuttings and effectively inhibits rock debris dispersion, so that the purposes of keeping the integrity of the drilling cuttings and inhibiting slurry making are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of coating agents for drilling fluids, and is a fully coated coating agent for drilling fluids and a preparation method thereof. Background Art

[0002] As the demand for oil and gas resources increases, conventional oil and gas resources are exhausted, and the intensity of unconventional oil and gas resource exploitation is increasing year by year. In the process of unconventional drilling, mud shale is often encountered in easily hydrated formations. In this case, the inhibition of drilling fluid is crucial. At present, the inhibition of drilling fluid is mainly provided by coating agents and inhibitors. The coating agent has two main functions. One is to inhibit the dispersion of rock cuttings, prevent the performance of the drilling fluid system from changing, and maintain the stability of the drilling fluid; the other is to stabilize the well wall, preventing the well wall from collapsing due to long-term contact with the drilling fluid and hydration dispersion.

[0003] The ideal inhibitory drilling fluid technology can make the newly drilled cuttings be densely wrapped. The inhibitor in the drilling fluid can well inhibit the clay minerals in the newly drilled cuttings. The coating agent can well wrap the cuttings, form a hydration layer on the outer layer of the cuttings, and prevent the cuttings from hydrating again. The inhibition of drilling fluid is a common difficulty encountered by drilling fluid when drilling shale that is prone to collapse. Often, adding a sufficient amount of shale inhibitor or using brine drilling fluid still cannot well inhibit the formation. One of the important reasons is that the cuttings are not well wrapped. The cuttings are constantly dispersed during the return process with the drilling fluid, resulting in more inferior solid phases in the drilling fluid, more shale entering the drilling fluid, and the effective components in the drilling fluid are adsorbed by the inferior solid phase. The performance of the drilling fluid is getting worse and worse, and it is getting further and further away from the design requirements of the drilling fluid. To maintain the original drilling fluid performance, more treatment agents are needed to maintain the drilling fluid performance, which is sometimes more likely to cause downhole complexity. Therefore, there is an urgent need for drilling fluid coating agents with strong coating effects on cuttings.

[0004] The coating agents currently on the market are mainly polyacrylamide polymer potassium salts. The Chinese patent document with publication number CN104610938A discloses a high temperature and salt resistance coating agent and its preparation method. The coating agent contains structures such as sulfonic acid groups and benzene rings, has strong temperature and salt resistance, and is suitable for a variety of brine systems. The Chinese patent document with publication number CN106221680A discloses a preparation method of a hydrophobic associating polymer coating agent for drilling fluid. The patent introduces hydrophobic groups into polymer molecules to produce association in aqueous solution, so that the polymer has strong temperature and salt resistance and also enhances the inhibitory effect. However, the current research on coating agents mainly focuses on improving temperature and salt resistance, but there are also problems such as poor solubility of coating agents and insufficient coating inhibition performance. Summary of the invention

[0005] The present invention provides a fully coated coating agent for drilling fluid and a preparation method thereof, which overcomes the deficiencies of the above-mentioned prior art and can effectively solve the problems of poor solubility of the prior coating agent and insufficient coating inhibition performance.

[0006] One of the technical solutions of the present invention is achieved by the following measures: a fully coated coating agent for drilling fluid, the structural formula of which is:

[0007]

[0008] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions:

[0009] The above-mentioned fully coated coating agent for drilling fluid comprises, by weight, 30 to 70 parts of acrylic acid, 120 to 180 parts of acrylamide, 60 to 110 parts of 2-acrylamido-2-methylpropanesulfonic acid, 20 to 60 parts of maleic anhydride, 20 to 45 parts of N-vinyl pyrrolidone, 25 to 58 parts of 3-butene-1-ol, 56 to 93 parts of sodium hydroxide, 8 to 16 parts of ammonium persulfate, 4 to 12 parts of azobisisobutyronitrile and 330 to 700 parts of deionized water.

[0010] The above-mentioned fully coated coating agent for drilling fluid is obtained by the following method:

[0011] S1, dissolving a required amount of acrylic acid in deionized water with a total weight of 40% to 70% to obtain an acrylic acid solution, and dissolving a required amount of sodium hydroxide in deionized water with a total weight of 10% to 20% to obtain a sodium hydroxide solution;

[0012] S2, dropwise adding a portion of the sodium hydroxide solution to the acrylic acid solution, and then adding a required amount of 2-acrylamide-2-methylpropanesulfonic acid and stirring sufficiently to obtain a mixed solution a, adjusting the pH value of the mixed solution a, and then adding a required amount of acrylamide to the mixed solution a to dissolve, to obtain a mixed material 1;

[0013] S3, dissolving a required amount of maleic anhydride in the remaining amount of deionized water at 50° C. to 80° C. to obtain a maleic anhydride solution, adding the remaining amount of sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b, adding a required amount of N-vinyl pyrrolidone to the mixed solution b and stirring uniformly to obtain a mixed material 2;

[0014] S4, mixing the mixed material 1 and the mixed material 2 under stirring, and then sequentially adding the required amount of 3-butene-1-ol, ammonium persulfate and azobisisobutyronitrile to carry out polymerization reaction to obtain a reaction product, and drying and crushing the reaction product to obtain a fully coated coating agent for drilling fluid.

[0015] In the above step S2, a portion of the sodium hydroxide solution accounts for 40% to 65% of the total weight of the sodium hydroxide solution.

[0016] In the above step S2, the stirring time is 50 min to 120 min, and the pH value of the mixed solution a is adjusted to 8 to 10.

[0017] In the above step S3, the stirring time is 40 min to 80 min, and the pH value of the mixed solution b is adjusted to 8 to 10.

[0018] In the above step S4, the polymerization reaction time is 1 h to 3 h.

[0019] The second technical solution of the present invention is achieved by the following measures: a method for preparing a fully coated coating agent for drilling fluid, obtained by the following method:

[0020] S1, dissolving a required amount of acrylic acid in deionized water with a total weight of 40% to 70% to obtain an acrylic acid solution, and dissolving a required amount of sodium hydroxide in deionized water with a total weight of 10% to 20% to obtain a sodium hydroxide solution;

[0021] S2, dropwise adding a portion of the sodium hydroxide solution to the acrylic acid solution, and then adding a required amount of 2-acrylamide-2-methylpropanesulfonic acid and stirring sufficiently to obtain a mixed solution a, adjusting the pH value of the mixed solution a, and then adding a required amount of acrylamide to the mixed solution a to dissolve, to obtain a mixed material 1;

[0022] S3, dissolving a required amount of maleic anhydride in the remaining amount of deionized water at 50° C. to 80° C. to obtain a maleic anhydride solution, adding the remaining amount of sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b, adding a required amount of N-vinyl pyrrolidone to the mixed solution b and stirring uniformly to obtain a mixed material 2;

[0023] S4, mixing the mixed material 1 and the mixed material 2 under stirring, and then sequentially adding the required amount of 3-butene-1-ol, ammonium persulfate and azobisisobutyronitrile to carry out polymerization reaction to obtain a reaction product, and drying and crushing the reaction product to obtain a fully coated coating agent for drilling fluid.

[0024] The fully coated coating agent for drilling fluid of the present invention can firmly adsorb more adsorption groups on the clay surface in drill cuttings, better spread in fresh water or drilling fluid containing salt water, tightly wrap the drill cuttings, and effectively inhibit the dispersion of rock cuttings, thereby achieving the purpose of maintaining the integrity of drill cuttings and inhibiting pulping. DETAILED DESCRIPTION

[0025] The present invention is not limited by the following embodiments, and specific implementation methods can be determined according to the technical scheme of the present invention and actual conditions. The various chemical reagents and chemicals mentioned in the present invention are all known and commonly used chemical reagents and chemicals in the prior art unless otherwise specified; the percentages in the present invention are all mass percentages unless otherwise specified.

[0026] The present invention will be further described below in conjunction with embodiments:

[0027] Embodiment 1: The fully coated coating agent for the drilling fluid has the structural formula:

[0028]

[0029] Embodiment 2: The fully coated coating agent for the drilling fluid comprises 30 to 70 parts of acrylic acid, 120 to 180 parts of acrylamide, 60 to 110 parts of 2-acrylamido-2-methylpropanesulfonic acid, 20 to 60 parts of maleic anhydride, 20 to 45 parts of N-vinyl pyrrolidone, 25 to 58 parts of 3-butene-1-ol, 56 to 93 parts of sodium hydroxide, 8 to 16 parts of ammonium persulfate, 4 to 12 parts of azobisisobutyronitrile and 330 to 700 parts of deionized water, and is obtained by the following method:

[0030] S1, dissolving a required amount of acrylic acid in deionized water with a total weight of 40% to 70% to obtain an acrylic acid solution, and dissolving a required amount of sodium hydroxide in deionized water with a total weight of 10% to 20% to obtain a sodium hydroxide solution;

[0031] S2, dropwise adding a portion of the sodium hydroxide solution to the acrylic acid solution, and then adding a required amount of 2-acrylamide-2-methylpropanesulfonic acid and stirring sufficiently to obtain a mixed solution a, adjusting the pH value of the mixed solution a, and then adding a required amount of acrylamide to the mixed solution a to dissolve, to obtain a mixed material 1;

[0032] S3, dissolving a required amount of maleic anhydride in the remaining amount of deionized water at 50° C. to 80° C. to obtain a maleic anhydride solution, adding the remaining amount of sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b, adding a required amount of N-vinyl pyrrolidone to the mixed solution b and stirring uniformly to obtain a mixed material 2;

[0033] S4, mixing the mixed material 1 and the mixed material 2 under stirring, and then sequentially adding the required amount of 3-butene-1-ol, ammonium persulfate and azobisisobutyronitrile to carry out polymerization reaction to obtain a reaction product, and drying and crushing the reaction product to obtain a fully coated coating agent for drilling fluid.

[0034] Embodiment 3: As an optimization of the above embodiment, in step S2, a portion of the sodium hydroxide solution accounts for 40% to 65% of the total weight of the sodium hydroxide solution.

[0035] Example 4: As an optimization of the above example, in step S2, the stirring time is 50 min to 120 min, and the pH value of the mixed solution a is adjusted to 8 to 10.

[0036] Example 5: As an optimization of the above example, in step S3, the stirring time is 40 min to 80 min, and the pH value of the mixed solution b is adjusted to 8 to 10.

[0037] Embodiment 6: As an optimization of the above embodiment, in step S4, the polymerization reaction time is 1 h to 3 h.

[0038] At present, improving the coating capacity of existing drilling fluid coating agents for drilling cuttings can more effectively improve the inhibition of drilling fluid, reduce the dispersion of drilling cuttings during the return process, and maintain the inhibition of drilling fluid. Especially for the Ji 28 and Ji 36 blocks of Tuha Oilfield, the clay content in the mudstone of the upper formation is mainly illite-montmorillonite mixed layer. The biggest problem of this formation is not only easy to collapse, but also easy to mud-pack the drill bit, which seriously affects the drilling speed, and the drilling fluid is easily affected by the formation cuttings, and the rheology becomes worse.

[0039] The fully-encapsulated coating agent for drilling fluid of the present invention can maintain the integrity of drill cuttings and stabilize the rheological properties of drilling fluid during use. That is, after adopting the fully-encapsulated coating agent for drilling fluid of the present invention, more adsorption groups can be firmly adsorbed on the clay surface in drill cuttings, and can be better spread in fresh water or drilling fluid containing salt water, tightly wrapping drill cuttings, and effectively inhibiting the dispersion of rock cuttings, thereby achieving the purpose of maintaining the integrity of drill cuttings and inhibiting slurrying.

[0040] Embodiment 7:

[0041] The fully coated coating agent for drilling fluid comprises 30 parts of acrylic acid, 120 parts of acrylamide, 60 parts of 2-acrylamido-2-methylpropanesulfonic acid, 20 parts of maleic anhydride, 20 parts of N-vinyl pyrrolidone, 25 parts of 3-butene-1-ol, 56 parts of sodium hydroxide, 8 parts of ammonium persulfate, 4 parts of azobisisobutyronitrile and 330 parts of deionized water, and is obtained by the following method:

[0042] S1, dissolving a required amount of acrylic acid in a total amount of 40% deionized water to obtain an acrylic acid solution, and dissolving a required amount of sodium hydroxide in a total amount of 10% deionized water to obtain a sodium hydroxide solution;

[0043] S2, adding a total amount of 40% sodium hydroxide solution to the acrylic acid solution, and then adding a required amount of 2-acrylamide-2-methylpropanesulfonic acid and stirring for 50 minutes to obtain a mixed solution a, adjusting the pH value of the mixed solution a to 8, and adding a required amount of acrylamide to the mixed solution a to dissolve, to obtain a mixed material 1;

[0044] S3, dissolving a required amount of maleic anhydride in the remaining amount of deionized water at 50° C. to obtain a maleic anhydride solution, adding the remaining amount of sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b to 8, adding a required amount of N-vinyl pyrrolidone to the mixed solution b and stirring for 40 minutes to obtain a mixed material 2;

[0045] S4, mixing the mixed material 1 and the mixed material 2 under stirring, and then adding the required amount of 3-butene-1-ol, ammonium persulfate and azobisisobutyronitrile in sequence to polymerize for 1 hour to obtain a reaction product, and drying and crushing the reaction product to obtain a fully coated coating agent for drilling fluid.

[0046] Embodiment 8:

[0047] The fully coated coating agent for drilling fluid comprises 70 parts of acrylic acid, 180 parts of acrylamide, 110 parts of 2-acrylamido-2-methylpropanesulfonic acid, 60 parts of maleic anhydride, 45 parts of N-vinyl pyrrolidone, 58 parts of 3-butene-1-ol, 93 parts of sodium hydroxide, 16 parts of ammonium persulfate, 12 parts of azobisisobutyronitrile and 700 parts of deionized water, and is obtained by the following method:

[0048] S1, dissolving a required amount of acrylic acid in 70% of deionized water to obtain an acrylic acid solution, and dissolving a required amount of sodium hydroxide in 20% of deionized water to obtain a sodium hydroxide solution;

[0049] S2, adding a total amount of 65% sodium hydroxide solution to the acrylic acid solution, and then adding a required amount of 2-acrylamide-2-methylpropanesulfonic acid and stirring for 120 minutes to obtain a mixed solution a, adjusting the pH value of the mixed solution a to 10, and adding a required amount of acrylamide to the mixed solution a to dissolve, to obtain a mixed material 1;

[0050] S3, dissolving a required amount of maleic anhydride in the remaining amount of deionized water at 50° C. to 80° C. to obtain a maleic anhydride solution, adding the remaining amount of sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b to 10, adding a required amount of N-vinyl pyrrolidone to the mixed solution b and stirring for 80 minutes to obtain a mixed material 2;

[0051] S4, mixing the mixed material 1 and the mixed material 2 under stirring, and then adding the required amount of 3-butene-1-ol, ammonium persulfate and azobisisobutyronitrile in sequence to carry out polymerization reaction for 3 hours to obtain a reaction product, and drying and crushing the reaction product to obtain a fully coated coating agent for drilling fluid.

[0052] Embodiment 9:

[0053] The fully coated coating agent for drilling fluid comprises 50 parts of acrylic acid, 160 parts of acrylamide, 90 parts of 2-acrylamido-2-methylpropanesulfonic acid, 40 parts of maleic anhydride, 30 parts of N-vinyl pyrrolidone, 40 parts of 3-butene-1-ol, 80 parts of sodium hydroxide, 12 parts of ammonium persulfate, 8 parts of azobisisobutyronitrile and 500 parts of deionized water, and is obtained by the following method:

[0054] S1, dissolving a required amount of acrylic acid in a total amount of 55% deionized water to obtain an acrylic acid solution, and dissolving a required amount of sodium hydroxide in a total amount of 15% deionized water to obtain a sodium hydroxide solution;

[0055] S2, adding a total amount of 50% sodium hydroxide solution to the acrylic acid solution, and then adding a required amount of 2-acrylamide-2-methylpropanesulfonic acid and stirring for 80 minutes to obtain a mixed solution a, adjusting the pH value of the mixed solution a to 9, and then adding a required amount of acrylamide to the mixed solution a to dissolve, to obtain a mixed material 1;

[0056] S3, dissolving a required amount of maleic anhydride in the remaining amount of deionized water at 60° C. to obtain a maleic anhydride solution, adding the remaining amount of sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b to 9, adding a required amount of N-vinyl pyrrolidone to the mixed solution b and stirring for 60 minutes to obtain a mixed material 2;

[0057] S4, mixing the mixed material 1 and the mixed material 2 under stirring, and then adding the required amount of 3-butene-1-ol, ammonium persulfate and azobisisobutyronitrile in sequence to carry out polymerization reaction for 2 hours to obtain a reaction product, and drying and crushing the reaction product to obtain a fully coated coating agent for drilling fluid.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The fully coated coating agent for drilling fluid of the present invention can fully coat the drill cuttings in fresh water or salt water, that is, it can be well adsorbed on the surface of the drill cuttings in fresh water or salt water, can better form a hydration film, and fully coat the surface of the drill cuttings to maintain the integrity of the drill cuttings.

[0060] At present, the adsorption group of the conventional coating agent for drilling fluid is an amide group (-CONH2), and the hydration group is a carboxyl group (-COOH). On this basis, the present invention introduces the raw material 3-butene-1-ol. The hydroxyl (-OH) group in the raw material can be used as both an adsorption group and a hydration group, and is connected in a hydrogen bond manner, so that the adsorption and hydration are more firm. The present invention also introduces the raw materials 2-acrylamide-2-methylpropane sulfonic acid and N-vinyl pyrrolidone, that is, the sulfonic acid group (-SO3H) and pyrrolidone (-NC4H6O) with large steric hindrance effect are introduced to improve the steric hindrance effect of the molecular chain, so that the temperature and salt resistance of the fully coated coating agent for drilling fluid is greatly improved, and the purpose of tightly coating the drill cuttings is achieved.

[0061] Embodiment 10:

[0062] The drilling fluid full-coating coating agent is obtained by the following method:

[0063] S1, dissolving 30 g of acrylic acid in 150 mL of deionized water to obtain an acrylic acid solution, and dissolving 56 g of sodium hydroxide in 50 mL of deionized water to obtain a sodium hydroxide solution;

[0064] S2, adding a total amount of 40% sodium hydroxide solution to the acrylic acid solution, and then adding 60g of 2-acrylamide-2-methylpropanesulfonic acid and stirring for 80min to obtain a mixed solution a, adjusting the pH value of the mixed solution a to 9, and adding 120g of acrylamide to the mixed solution a to fully dissolve, to obtain a mixed material 1;

[0065] S3, dissolving 20 g of maleic anhydride in 130 mL of water at 60° C. to obtain a maleic anhydride solution, adding the remaining amount of sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b to 9, adding 20 g of N-vinyl pyrrolidone to the mixed solution b and stirring for 60 min to obtain a mixed material 2;

[0066] S4, under stirring, after mixing the mixed material 1 and the mixed material 2, 25g of 3-butene-1-ol, 8g of ammonium persulfate and 4g of azobisisobutyronitrile were added in sequence to carry out polymerization reaction for 2h to obtain a reaction product, and the reaction product was dried and crushed to obtain a fully coated coating agent for drilling fluid.

[0067] Embodiment 11:

[0068] The drilling fluid full-coating coating agent is obtained by the following method:

[0069] S1, dissolving 38 g of acrylic acid in 170 mL of deionized water to obtain an acrylic acid solution, and dissolving 60 g of sodium hydroxide in 60 mL of deionized water to obtain a sodium hydroxide solution;

[0070] S2, adding a total amount of 45% sodium hydroxide solution to the acrylic acid solution, adding 75g of 2-acrylamide-2-methylpropanesulfonic acid and stirring for 80min to obtain a mixed solution a, adjusting the pH value of the mixed solution a to 9, adding 135g of acrylamide to the mixed solution a and fully dissolving it to obtain a mixed material 1;

[0071] S3, dissolving 38 g of maleic anhydride in 150 mL of deionized water at 60° C. to obtain a maleic anhydride solution, adding the remaining amount of sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b to 9, adding 25 g of N-vinyl pyrrolidone to the mixed solution b and stirring for 60 min to obtain a mixed material 2;

[0072] S4, after mixing the mixed material 1 and the mixed material 2 under stirring, 30g of 3-butene-1-ol, 9g of ammonium persulfate and 5g of azobisisobutyronitrile were added in sequence to carry out polymerization reaction for 2h to obtain a reaction product, and the reaction product was dried and crushed to obtain a fully coated coating agent for drilling fluid.

[0073] Embodiment 12:

[0074] The drilling fluid full-coating coating agent is obtained by the following method:

[0075] S1, dissolving 50 g of acrylic acid in 350 mL of deionized water to obtain an acrylic acid solution, and dissolving 65 g of sodium hydroxide in 80 mL of deionized water to obtain a sodium hydroxide solution;

[0076] S2, adding a total amount of 55% sodium hydroxide solution to the acrylic acid solution, and then adding 85g of 2-acrylamide-2-methylpropanesulfonic acid and stirring for 80min to obtain a mixed solution a, adjusting the pH value of the mixed solution a to 9, and then adding 165g of acrylamide to the mixed solution a and fully dissolving it to obtain a mixed material 1;

[0077] S3, dissolving 45 g of maleic anhydride in 165 mL of deionized water at 60° C. to obtain a maleic anhydride solution, adding the remaining amount of sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b to 9, adding 35 g of N-vinyl pyrrolidone to the mixed solution b and stirring for 60 min to obtain a mixed material 2;

[0078] S4, after mixing the mixed material 1 and the mixed material 2 under stirring, 38g of 3-butene-1-ol, 13g of ammonium persulfate and 10g of azobisisobutyronitrile were added in sequence to carry out polymerization reaction for 2h to obtain a reaction product, and the reaction product was dried and crushed to obtain a fully coated coating agent for drilling fluid.

[0079] Embodiment 13:

[0080] The drilling fluid full-coating coating agent is obtained by the following method:

[0081] S1, dissolving 65 g of acrylic acid in 390 mL of deionized water to obtain an acrylic acid solution, and dissolving 80 g of sodium hydroxide in 90 mL of deionized water to obtain a sodium hydroxide solution;

[0082] S2, dropwise adding a total amount of 60% sodium hydroxide solution to the acrylic acid solution, then adding 95g of 2-acrylamide-2-methylpropanesulfonic acid and stirring for 80min to obtain a mixed solution a, adjusting the pH value of the mixed solution a to 9, adding 170g of acrylamide to the mixed solution a and fully dissolving it to obtain a mixed material 1;

[0083] S3, dissolving 55 g of maleic anhydride in 170 mL of deionized water at 60° C. to obtain a maleic anhydride solution, adding the remaining amount of sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b to 9, adding 40 g of N-vinyl pyrrolidone to the mixed solution b and stirring for 60 min to obtain a mixed material 2;

[0084] S4, after mixing the mixed material 1 and the mixed material 2 under stirring, 50g of 3-butene-1-ol, 15g of ammonium persulfate and 11g of azobisisobutyronitrile were added in sequence to carry out polymerization reaction for 2h to obtain a reaction product, and the reaction product was dried and crushed to obtain a fully coated coating agent for drilling fluid.

[0085] Embodiment 14:

[0086] The drilling fluid full-coating coating agent is obtained by the following method:

[0087] S1, dissolving 70 g of acrylic acid in 420 mL of deionized water to obtain an acrylic acid solution, and dissolving 93 g of sodium hydroxide in 100 mL of deionized water to obtain a sodium hydroxide solution;

[0088] S2, adding a total amount of 65% sodium hydroxide solution to the acrylic acid solution, and then adding 110g of 2-acrylamide-2-methylpropanesulfonic acid and stirring for 80min to obtain a mixed solution a, adjusting the pH value of the mixed solution a to 9, and then adding 180g of acrylamide to the mixed solution a and fully dissolving it to obtain a mixed material 1;

[0089] S3, dissolving 60 g of maleic anhydride in 180 mL of deionized water at 60° C. to obtain a maleic anhydride solution, adding the remaining amount of sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b to 9, adding 45 g of N-vinyl pyrrolidone to the mixed solution b and stirring for 60 min to obtain a mixed material 2;

[0090] S4, after mixing the mixed material 1 and the mixed material 2 under stirring, 58g of 3-butene-1-ol, 16g of ammonium persulfate and 12g of azobisisobutyronitrile were added in sequence to carry out polymerization reaction for 2h to obtain a reaction product, and the reaction product was dried and crushed to obtain a fully coated coating agent for drilling fluid.

[0091] Comparative Example 1: The polymer coating agent FA367 commonly used in existing oil fields was used.

[0092] Comparative Example 2: The polymer coating agent K-PAM commonly used in existing oil fields was used.

[0093] Example 15: The inhibition performance and swelling performance of the fully coated coating agent for drilling fluid of the present invention were evaluated.

[0094] The inhibition performance is mainly evaluated by the cuttings rolling recovery rate experiment to evaluate the ability of the fully coated coating agent for drilling fluid of the present invention to inhibit the hydration and dispersion of cuttings. The higher the rolling recovery rate, the stronger the ability of the coating agent to inhibit the hydration and dispersion of cuttings. At the same time, Comparative Examples 1 and 2 are used as controls.

[0095] Evaluation method of inhibition performance: 50 g of 6-10 mesh rock chips were added to 500 mL of 0.5% (wt) aqueous solution of the fully coated inhibitor for drilling fluid prepared in Examples 10 to 14 of the present invention, and then hot rolled at 160°C for 16 hours, passed through a 40 mesh sieve, and washed with clean water. The rock chips were dried in a constant temperature drying oven at 105°C ± 3°C, weighed, and the first rolling recovery rate was calculated. The rock chips after one rolling were added to 500 mL of 0.5% (wt) aqueous solution of the fully coated inhibitor for drilling fluid prepared in Examples 10 to 14 of the present invention, and hot rolled at 150°C for 16 hours, passed through a 40 mesh sieve, and washed with clean water. The rock chips were dried, weighed, and the second rolling recovery rate was calculated.

[0096] The expansion performance is evaluated by using on-site rock cuttings powder to press artificial cores according to the requirements of the shale expansion test standard, and conducting experiments on a shale expansion tester according to the shale expansion test standard to evaluate the ability of the fully coated coating agent for drilling fluid of the present invention to inhibit the expansion of shale. The expansion test can reflect the ability of the product to inhibit the hydration expansion of clay minerals. The greater the expansion, the worse the ability to inhibit clay expansion, the greater the impact on the formation, and the unfavorable for the stability of the well wall.

[0097] Swelling performance evaluation method: 0.5% (wt) of the aqueous solution of the fully coated inhibitor for drilling fluid prepared in Examples 10 to 14 of the present invention was added to a 20% sodium chloride and 7% potassium chloride brine system, respectively, the swelling amount was measured for 2h and 16h, and the linear expansion rate of the shale at the corresponding time was calculated.

[0098] The inhibition performance results are shown in Table 1, and the expansion performance results are shown in Table 2. It can be seen from Table 1 and Table 2 that, compared with Comparative Examples 1 and 2, at a dosage of 0.5%, the fully coated coated inhibitors for drilling fluid prepared in Examples 10 to 14 of the present invention have a higher secondary rolling recovery rate and a lower 16h linear expansion rate, indicating that the fully coated coated inhibitors for drilling fluid of the present invention can not only effectively play a coating role, effectively inhibit the dispersion of cuttings, but also increase the rolling recovery rate of cuttings.

[0099] In summary, the fully coated coating agent for drilling fluid of the present invention can firmly adsorb more adsorption groups on the clay surface in drill cuttings, better spread in fresh water or drilling fluid containing salt water, tightly wrap the drill cuttings, and effectively inhibit the dispersion of rock cuttings, thereby achieving the purpose of maintaining the integrity of drill cuttings and inhibiting slurrying.

[0100] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

[0101] Table 1

[0102]

[0103]

[0104] Table 2

[0105] name 2h linear expansion rate / % 16h linear expansion rate / % Example 10 3.23 7.56 Embodiment 11 3.58 7.79 Example 12 3.06 7.29 Example 13 3.44 7.68 Embodiment 14 2.96 7.06 Comparative Example 1 4.42 8.55 Comparative Example 2 5.58 10.26

Claims

1. A fully coated coating agent for drilling fluid, characterized in that Its structural formula is:

2. A fully coated coating agent for drilling fluid, characterized in that The raw materials include, by weight, 30 to 70 parts of acrylic acid, 120 to 180 parts of acrylamide, 60 to 110 parts of 2-acrylamido-2-methylpropanesulfonic acid, 20 to 60 parts of maleic anhydride, 20 to 45 parts of N-vinyl pyrrolidone, 25 to 58 parts of 3-butene-1-ol, 56 to 93 parts of sodium hydroxide, 8 to 16 parts of ammonium persulfate, 4 to 12 parts of azobisisobutyronitrile and 330 to 700 parts of deionized water.

3. The fully coated coating agent for drilling fluid according to claim 2, wherein Obtained as follows: S1, dissolving a required amount of acrylic acid in deionized water having a total weight of 40% to 70% to obtain an acrylic acid solution, and dissolving a required amount of sodium hydroxide in deionized water having a total weight of 10% to 20% to obtain a sodium hydroxide solution; S2, adding a portion of the sodium hydroxide solution dropwise to the acrylic acid solution, and then adding a required amount of 2-acrylamido-2-methylpropanesulfonic acid and stirring thoroughly to obtain a mixed solution a, adjusting the pH value of the mixed solution a, and then adding a required amount of acrylamide to the mixed solution a to dissolve it, to obtain a mixed material 1; S3, dissolving a required amount of maleic anhydride in the remainder of deionized water at 50° C. to 80° C. to obtain a maleic anhydride solution, adding the remainder of the sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b, and then adding a required amount of N-vinyl pyrrolidone to the mixed solution b and stirring uniformly to obtain a mixed material 2; S4, mixing the mixed material 1 and the mixed material 2 under stirring, and then sequentially adding the required amounts of 3-butene-1-ol, ammonium persulfate and azobisisobutyronitrile to carry out polymerization reaction to obtain a reaction product, and drying and crushing the reaction product to obtain a fully coated coating agent for drilling fluid.

4. The fully coated coating agent for drilling fluid according to claim 3, characterized in that In step S2, a portion of the sodium hydroxide solution accounts for 40% to 65% of the total weight of the sodium hydroxide solution.

5. The fully coated coating agent for drilling fluid according to claim 3 or 4, characterized in that In step S2, the stirring time is 50 min to 120 min, and the pH value of the mixed solution a is adjusted to 8 to 10.

6. The fully coated coating agent for drilling fluid according to claim 3, 4 or 5, characterized in that In step S3, the stirring time is 40 min to 80 min, and the pH value of the mixed solution b is adjusted to 8 to 10.

7. The fully coated coating agent for drilling fluid according to any one of claims 3 to 6, characterized in that In step S4, the polymerization reaction time is 1 h to 3 h.

8. A method for preparing a fully coated coating agent for drilling fluid according to any one of claims 1, 3 to 7, characterized in that Proceed as follows: S1, dissolving a required amount of acrylic acid in deionized water having a total weight of 40% to 70% to obtain an acrylic acid solution, and dissolving a required amount of sodium hydroxide in deionized water having a total weight of 10% to 20% to obtain a sodium hydroxide solution; S2, adding a portion of the sodium hydroxide solution dropwise to the acrylic acid solution, and then adding a required amount of 2-acrylamido-2-methylpropanesulfonic acid and stirring thoroughly to obtain a mixed solution a, adjusting the pH value of the mixed solution a, and then adding a required amount of acrylamide to the mixed solution a to dissolve it, to obtain a mixed material 1; S3, dissolving a required amount of maleic anhydride in the remainder of deionized water at 50° C. to 80° C. to obtain a maleic anhydride solution, adding the remainder of the sodium hydroxide solution to the maleic anhydride solution to obtain a mixed solution b, adjusting the pH value of the mixed solution b, and then adding a required amount of N-vinyl pyrrolidone to the mixed solution b and stirring uniformly to obtain a mixed material 2; S4, mixing the mixed material 1 and the mixed material 2 under stirring, and then sequentially adding the required amounts of 3-butene-1-ol, ammonium persulfate and azobisisobutyronitrile to carry out polymerization reaction to obtain a reaction product, and drying and crushing the reaction product to obtain a fully coated coating agent for drilling fluid.

Images