MTC leaking stoppage working fluid and preparation method thereof

Abstract

The invention relates to the technical field of leaking stoppage working solutions, in particular to an MTC leaking stoppage working solution and a preparation method thereof.The MTC leaking stoppage working solution is obtained through the following steps that a suspending agent, a compound activator, a density regulator and a retarder are added into water to be mixed, a mixed solution is obtained, drilling fluid and slag with the required amount are added into the mixed solution to be mixed, and the MTC leaking stoppage working solution is obtained. The MTC leaking stoppage working fluid which is good in compatibility, wide in density range, high in slurry suspension stability, flexible and adjustable in thickening time, enhanced in solidified body strength and stable for a long time is designed through the ground suspending agent, the density regulator, the activating agent and the retarder, the well cementation quality is guaranteed, and the MTC leaking stoppage working fluid is suitable for the well cementation. The problem that the strength of the solidified body of the MTC leaking stoppage working fluid is insufficient is effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of plugging working fluids, and specifically relates to an MTC plugging working fluid and a preparation method thereof. Background Art

[0002] When drilling into formations with well-developed fractures and pores or broken formations, well leakage often occurs. For the treatment of leakage, a variety of technologies have been developed in China. Traditional bridging plugging fluids and plugging technologies have low lamination capacity of the plugging layer formed because the slurry cannot solidify. After the circulation is re-established, the leaking layer may be reopened under the pressure of the drilling fluid column, requiring repeated plugging. Although cement, an inorganic gelling plugging material, can be solidified by itself, it has poor compatibility with drilling fluid, and seriously pollutes the formation, and there is uncertainty in operability, so safe construction cannot be guaranteed. Cement slurry cannot effectively stay in the leaking formation, and its strength is severely attenuated after mixing with the drilling fluid.

[0003] MTC technology is to add blast furnace slag to the drilling fluid and use a treatment agent to make it have the properties of cementing and plugging working fluid (it can solidify and reach the designed strength at a certain time) to perform cementing and plugging operations to achieve the purpose of casing cementing and solidification plugging. However, MTC cementing has the following disadvantages: (1) The strength decay rate of the solidified material formed after MTC solidifies is faster than that of cement stone, and this technology is rarely used in production layer cementing at present; (2) The brittleness problem of MTC solidified material is more serious than that of Portland cement, and the toughness of the solidified material needs to be improved; (3) The activator for preparing MTC slurry is strongly alkaline, which is seriously corrosive to the casing after cementing; (4) The strength of low-density MTC system is often low, and the scope of application is still very limited.

[0004] Zhang Ruihui, Shi Jun and others developed a WFGJ-1 plugging working fluid (Study on plugging working fluid with temperature-controlled composite adhesive function [D]. Xi'an Shiyou University, 2022), which is a composite system mainly composed of organic adhesive materials (E-51 / DICY / 2-MI) and supplemented by external additives such as bridge plug materials and suspension stabilizers. Its conventional density is 1.20g / cm 3 Nearby, the density is adjustable, the suspension ability and fluidity are good, it is resistant to high temperature, has strong mechanical properties, and the compressive strength can reach 3MPa. It can basically achieve plugging in the simulated leaking layer plugging experiment.

[0005] Li Yanming, Guo Xiaoyang and others proposed a kind of inorganic cementitious material drilling plugging fluid with curing function (Development of plugging fluid for coalbed methane drilling construction in coal mine goaf area [J]. Coal Science and Technology, 2019, (09): 152-157.). The plugging fluid has a fluidity of 21cm at 30°C, a thickening time of less than 61min, and a 1d compressive strength of more than 6MPa. Its performance indicators meet the requirements for plugging shallow wells of coalbed methane in coal mining areas. However, the strength performance of these MTC plugging working fluids with different densities is uneven, which cannot effectively meet the plugging design requirements. The high-temperature curing solid body is prone to cracking and is difficult to replace cement materials. Summary of the invention

[0006] The present invention provides an MTC plugging working fluid and a preparation method thereof, which overcomes the deficiencies of the above-mentioned prior art and can effectively solve the problem that the existing MTC plugging working fluid has poor strength performance and cannot effectively meet the plugging design requirements.

[0007] One of the technical solutions of the present invention is achieved through the following measures: an MTC plugging working fluid, the raw materials include slag, the weight of the slag is 100%, and the raw materials also include 85% drilling fluid, 15% water, 2.0% to 3.2% suspending agent, 5.0% to 8.0% compound activator, 0% to 160% density regulator and 0% to 3.0% retarder by weight percentage; wherein the suspending agent includes 1.5% to 2.0% suspending agent polymer and 0.5% to 1.2% sodium bentonite.

[0008] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions: The above-mentioned suspending agent polymer is obtained by the following method: S1, under a nitrogen atmosphere, adjusting the pH of deionized water, and sequentially adding 2 to 3 parts of acrylamide, 12 to 13 parts of 2-acrylamido-2-methylpropanesulfonic acid, and 1 to 2 parts of N-isopropylmethacrylamide to 60 parts of deionized water after the pH is adjusted, and stirring evenly to obtain a mixed material; S2, adding 0.5 to 0.6 parts of ammonium persulfate and 0.2 to 0.3 parts of N,N-methylenebisacrylamide dropwise to the mixed material to react to obtain a reaction product, and then washing, drying and crushing the reaction product to obtain a suspension polymer.

[0009] In the above step S1, the pH value of the deionized water is adjusted to 7 to 9 using sodium hydroxide.

[0010] In the above step S2, the reaction temperature is 65° C. to 75° C., and the reaction product is washed with ethanol 2 to 3 times.

[0011] The above-mentioned compound activator is a mixture of activator JHJ-A and activator JHJ-B in a mass ratio of 1.5:6.0.

[0012] The compound activator JHJ-A is a mixture of sodium hydroxide, sodium carbonate and triethanolamine in a mass ratio of 23:8:0.8, and the compound activator JHJ-B is a mixture of sodium silicate and calcium sulfate in a mass ratio of 2:1.

[0013] The above-mentioned density regulator is one of a lightening agent and a weighting agent.

[0014] The lightening agent is floating beads, and the weighting agent is one of barite and hematite powder.

[0015] The above retarder is retarder XZ-HN1.

[0016] The MTC plugging working fluid is obtained by the following method: adding a required amount of suspending agent, compound activator, density regulator and retarder to a required amount of water to obtain a mixed solution, adding a required amount of drilling fluid and slag to the mixed solution to obtain the MTC plugging working fluid.

[0017] The second technical solution of the present invention is achieved through the following measures: a method for preparing an MTC plugging working fluid, which is carried out as follows: adding a required amount of suspending agent, a compound activator, a density regulator and a retarder to a required amount of water to obtain a mixed solution, adding a required amount of drilling fluid and slag to the mixed solution to obtain an MTC plugging working fluid.

[0018] The present invention designs an MTC plugging working fluid with good compatibility, wide density range, strong slurry suspension stability, flexible and adjustable thickening time, enhanced solidified body strength and long-term stability through the selected suspending agent, density regulator, activator and retarder components, thereby ensuring the cementing quality and effectively solving the problem of insufficient solidified body strength of the MTC plugging working fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a thickening performance diagram of the MTC plugging working fluid prepared in Example 21 of the present invention and the water-based drilling fluid at a volume ratio of 1:3 at 90°C.

[0020] Figure 2 This is a thickening performance diagram of the MTC plugging working fluid prepared in Example 21 of the present invention and the water-based drilling fluid at a volume ratio of 1:1 at 90°C.

[0021] Figure 3 This is a thickening performance diagram of the MTC plugging working fluid prepared in Example 21 of the present invention and the water-based drilling fluid at a volume ratio of 3:1 at 90°C. DETAILED DESCRIPTION

[0022] The present invention is not limited by the following embodiments, and the specific implementation method can be determined according to the technical scheme of the present invention and the actual situation. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all chemical reagents and chemicals known and used in the prior art; unless otherwise specified, the percentages in the present invention are all mass percentages; unless otherwise specified, the solutions in the present invention are all aqueous solutions with water as the solvent, for example, hydrochloric acid solution is a hydrochloric acid aqueous solution; the normal temperature and room temperature in the present invention generally refer to a temperature of 15°C to 25°C, and are generally defined as 25°C.

[0023] The present invention will be further described below in conjunction with embodiments: Example 1: The MTC plugging working fluid, the raw materials include slag, based on the weight of the slag as 100%, the raw materials also include 85% drilling fluid, 15% water, 2.0% to 3.2% suspending agent, 5.0% to 8.0% compound activator, 0% to 160% density regulator and 0% to 3.0% retarder by weight percentage; wherein the suspending agent includes 1.5% to 2.0% suspending agent polymer and 0.5% to 1.2% sodium bentonite.

[0024] In the present invention, the main particle component of the drilling fluid is clay, which is taken from an oil well in the Tarim Basin and has a density of 1.20 g / cm 3 , viscosity 45S, API water loss 3.6mL, dynamic shear force 5P, plastic viscosity 17mPa·s; slag is S95 grade slag from Jinan Iron and Steel Group Luxin Building Materials Co., Ltd., density 2.80g / cm 3 .

[0025] Example 2: As an optimization of the above example, the suspending agent polymer is obtained by the following method: S1, in a nitrogen atmosphere, adjusting the pH of deionized water, and sequentially adding 2 to 3 parts of acrylamide (AA), 12 to 13 parts of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and 1 to 2 parts of N-isopropylmethacrylamide to 60 parts of deionized water after the pH is adjusted, and stirring evenly to obtain a mixed material; S2, adding 0.5 to 0.6 parts of ammonium persulfate and 0.2 to 0.3 parts of N,N-methylenebisacrylamide dropwise to the mixed material to react to obtain a reaction product, and then washing, drying and crushing the reaction product to obtain a suspension polymer.

[0026] Embodiment 3: As an optimization of the above embodiment, in step S1, the pH value of deionized water is adjusted to 7 to 9 with sodium hydroxide.

[0027] Example 4: As an optimization of the above example, in step S2, the reaction temperature is 65°C to 75°C, and the reaction product is rinsed with ethanol (ethanol aqueous solution with a mass concentration of 95%) for 2 to 3 times.

[0028] In the MTC plugging working fluid of the present invention, the suspending agent is composed of a suspending agent polymer and sodium bentonite, wherein the suspending agent polymer is obtained by the preparation method of the present invention, and its main chain adopts a covalent bond with high stability, and the side chain functional group is designed to have an ionic group with high hydration ability, such as a sulfonic acid group, which can promote the room temperature dissolution rate of the suspending agent in the MTC plugging working fluid and reduce the impact on the rheological properties of the slurry; at the same time, an adsorption group amide group with strong adsorption ability is also introduced to enhance the adsorption capacity of the suspending agent polymer on a large number of clay particles.

[0029] Compared with conventional clays such as calcium bentonite (calcium clay) and natural bleaching earth, the sodium bentonite selected in the present invention has better dispersibility and higher slurrying rate. The sodium bentonite is composed of granular materials with different particle size distributions, which can effectively block formation pores or micropores to form a thin and dense filter cake, which can improve the stability and water loss reduction capacity of the drilling fluid, and is the basis for ensuring that the drilling fluid can achieve high-quality performance.

[0030] In the suspending agent of the present invention, different polymer addition amounts can better change the fluidity of the MTC plugging working fluid base fluid (the base fluid is composed of 85% drilling fluid and 15% water). As the amount of polymer increases, the network structure in the MTC plugging working fluid base fluid increases, the rheology becomes worse, and the suspension stability of the base fluid improves. When the amount of the suspending agent polymer is 1.5%, the rheology of the MTC plugging working fluid base fluid meets the suspension requirements.

[0031] The sodium-based bentonite in the raw material suspension agent can effectively avoid the sedimentation problem of the MTC plugging working fluid base fluid. When the suspension agent polymer dosage is 1.5% to 2.0%, adding sodium-based bentonite can improve the stability of the slurry. When the sodium-based bentonite addition amount is 0.5% to 1.2%, the slurry has good stability.

[0032] Example 5: As an optimization of the above example, the compound activator is a mixture of activator JHJ-A and activator JHJ-B in a mass ratio of 1.5:6.0.

[0033] Example 6: As an optimization of the above example, the compound activator JHJ-A is a mixture of sodium hydroxide, sodium carbonate and triethanolamine in a mass ratio of 23:8:0.8, and the compound activator JHJ-B is a mixture of sodium silicate and calcium sulfate in a mass ratio of 2:1.

[0034] In the present invention, the performance and selection of the activator play a key role in the hydration rate of the slag and the strength of the solidified product. Different activators have different reaction processes and hydration products. Generally, an activator is required to promote the destruction of the surface film of the slag glass and the growth of the crystal nucleus, and is beneficial to the formation of hydrates and the formation of a network after the slag is activated.

[0035] In the present invention, the activator is a compound activator, which is a mixture of activator JHJ-A and activator JHJ-B. Experiments have shown that when activator JHJ-A is used alone, its activity is too high, which destroys the stability of the slurry and causes cracking of the solidified material at high temperature; and when activator JHJ-B is used alone, the alkaline substance is relatively weak and cannot well activate the slag to generate strength. After the two activators are compounded, the rheology of the MTC plugging working fluid of the present invention and the compressive strength after solidification and condensation can be better guaranteed. At the same time, compared with the existing NaOH activator, the compound activator selected as the raw material of the present invention can also reduce the corrosion of the casing.

[0036] Embodiment 7: As an optimization of the above embodiment, the density regulator is one of a lightening agent and a weighting agent.

[0037] Example 8: As an optimization of the above example, the lightening agent is floating beads, and the weighting agent is one of barite and hematite powder.

[0038] In the present invention, the density regulator is a lightening agent or a weighting agent. The lightening agent can reduce the density of the MTC plugging working fluid, reduce the static liquid column pressure of the slurry, and prevent the low-pressure formation from leaking during the pumping and waiting process. The weighting agent is used to increase the density of the base fluid. However, the density difference between the weighting agent and the various material components in the slurry is large, and the density or dosage of the weighting agent is large, which can easily lead to the instability of the slurry suspension. The lightening agent of the present invention uses floating beads, whose compressive strength increases with the decrease of density, 0.60g / cm 3 The compressive strength can reach 70MPa, and it has strong formation pressure bearing capacity. The weighting agent of the present invention is barite or hematite powder, which can increase the density of the MTC plugging working fluid and ensure the slurry stability.

[0039] In the present invention, the density of the floating beads is 0.60 g / cm 3 , compressive strength 60MPa; barite density 4.35g / cm 3 , 80% particle size <45μm; hematite powder density is 7.20g / cm 3 , average particle size is 10μm to 150μm.

[0040] Example 9: As an optimization of the above example, the retarder is retarder XZ-HN1 (purchased from the cementing company of Western Drilling Engineering Co., Ltd.).

[0041] In the present invention, the retarder is selected as retarder XZ-HN1, and its retarding mechanism is to use 2-acrylamido-2-methylpropanesulfonic acid (AMPS) in the MTC plugging working fluid to preferentially adsorb on tricalcium aluminate (C3A), preventing the fastest hydration component from being combined with water molecules, while its adsorption on tricalcium silicate (C3S) is relatively weak, ensuring the strength of the solidified material. Since the MTC plugging working fluid contains sulfonate groups, the retarder XZ-HN1 is more stable in the MTC plugging working fluid containing a large amount of saline-alkali activator. After the retarder XZ-HN1 is added to the MTC plugging working fluid, the fluidity of the slurry becomes better and the thickening time is significantly prolonged. At the same time, while the retarder XZ-HN1 effectively adjusts the thickening time of the working fluid, it has a low effect on the water loss of the slurry and a small effect on the strength development of the solidified material.

[0042] Example 10: As an optimization of the above example, the MTC plugging working fluid is obtained by the following method: add the required amount of suspending agent, compound activator, density regulator and retarder to the required amount of water to obtain a mixed solution, add the required amount of drilling fluid and slag to the mixed solution to obtain the MTC plugging working fluid.

[0043] Example 11: The MTC plugging working fluid, the raw materials include 100g of slag, and the raw materials also include 85g of drilling fluid, 15g of water, 2.5g of suspending agent (1.5g of suspending agent polymer and 1.0g of sodium bentonite), 7.5g of compound activator (1.5g of activator JHJ-A and 6.0g of activator JHJ-B), 23g of density regulator (floating beads) and 3.0g of retarder, is obtained by the following method: add the required amount of suspending agent, compound activator, density regulator and retarder to the required amount of water to obtain a mixed solution, add the required amount of drilling fluid and slag to the mixed solution to obtain the MTC plugging working fluid. Among them, the suspending agent polymer is obtained by the following method: S1, under a nitrogen atmosphere, adjusting the pH value of deionized water to 8, and sequentially adding 2 g of acrylamide (AM), 12 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and 1 g of N-isopropylmethacrylamide to 60 g of the deionized water after the pH adjustment, stirring evenly to obtain a mixed material; S2, slowly drop 0.5g of ammonium persulfate and 0.2g of N,N-methylenebisacrylamide into the mixture, react at a temperature of 65°C to 75°C to obtain a reaction product, wash the reaction product with ethanol 2 to 3 times, and then dry and grind it to obtain a suspension polymer.

[0044] Example 12: The difference from Example 11 of the present invention is that the density regulator (floating beads) in the raw material formula is changed from 23% to 10%, and the other steps are the same.

[0045] Example 13: The difference from Example 11 of the present invention is that no density regulator is added to the raw material formula, and the remaining steps are the same.

[0046] Example 14: The difference from Example 11 of the present invention is that the density regulator (baryte) in the raw material formula is changed from 23% to 25%, and the other steps are the same.

[0047] Example 15: The difference from Example 11 of the present invention is that the density regulator (baryte) in the raw material formula is changed from 23% to 50%, and the other steps are the same.

[0048] Example 16: The difference from Example 11 of the present invention is that the density regulator (baryte) in the raw material formula is changed from 23% to 75%, and the other steps are the same.

[0049] Example 17: The difference from Example 11 of the present invention is that the density regulator (hematite powder) in the raw material formula is changed from 23% to 72%, and the remaining steps are the same.

[0050] Example 18: The difference from Example 11 of the present invention is that the density regulator (hematite powder) in the raw material formula is changed from 23% to 92%, and the other steps are the same.

[0051] Example 19: The difference from Example 11 of the present invention is that the density regulator (hematite powder) in the raw material formula is changed from 23% to 113%, and the remaining steps are the same.

[0052] Example 20: The difference from Example 11 of the present invention is that the density regulator (hematite powder) in the raw material formula is changed from 23% to 134%, and the remaining steps are the same.

[0053] Example 21: The difference from Example 11 of the present invention is that the density regulator (hematite powder) in the raw material formula is changed from 23% to 157%, and the remaining steps are the same.

[0054] Example 22: The difference from Example 11 of the present invention is that the retarder in the raw material formula is changed from 3.0% to 0.5%, and the other steps are the same.

[0055] Example 23: The difference from Example 15 of the present invention is that the retarder in the raw material formula is changed from 3.0% to 0.5%, and the other steps are the same.

[0056] Example 24: The difference from Example 18 of the present invention is that the retarder in the raw material formula is changed from 3.0% to 0.5%, and the other steps are the same.

[0057] Example 25: The difference from Example 21 of the present invention is that the retarder in the raw material formula is changed from 3.0% to 0.5%, and the other steps are the same.

[0058] Example 26: The comprehensive performance of the MTC plugging fluid of the present invention was investigated with reference to the method specified in GB / T 19139 "Test Methods for Oil Well Cement". The comprehensive performance includes rheological properties, suspension stability, thickening properties, compatibility evaluation and solidified strength evaluation.

[0059] Test 1: Rheological properties Test method: The rheological properties of the MTC plugging working fluids prepared in Examples 11 to 21 of the present invention were tested.

[0060] Test results: The raw material formulas of the MTC plugging working fluids prepared in Examples 11 to 21 of the present invention are shown in Table 1, and the rheological properties results are shown in Table 2. It can be seen from Table 2 that with the increase of the density of the MTC plugging working fluid system of the present invention, the fluidity index of the MTC plugging working fluid of the present invention first decreases and then increases, and the slurry has a large initial shear force and strong thixotropy, which is conducive to the retention of the working fluid in the leakage channel, indicating that the MTC plugging working fluid of the present invention has good rheological properties and strong thixotropic properties.

[0061] Test 2: Suspension stability performance Test method: Under high temperature conditions of 70° C. and 90° C. at the bottom of the well, the suspension stability test was performed on the MTC plugging working fluids prepared in Examples 11 to 21 of the present invention, respectively.

[0062] Test results: The results are shown in Tables 3 and 4. It can be seen from Tables 3 and 4 that at lower densities, as the temperature increases, the density difference of the MTC plugging working fluid system of the present invention increases, but at 90°C, the maximum upper and lower density difference of the slurry does not exceed 0.02 g / cm 3 , indicating that the MTC plugging working fluid of the present invention has good suspension stability. At higher density, more solid phase particles in the slurry support each other, a cementing structure is generated between the barite particles, the intermolecular viscosity increases, and the heavy particles are prevented from settling in the slurry, thereby improving the suspension stability. As the density increases, the water loss of the working fluid gradually decreases. Therefore, the MTC plugging working fluid system of the present invention has good filtration control ability. It shows that the MTC plugging working fluid of the present invention has good suspension stability at high temperature.

[0063] Test 3: Thickening performance Test method: Since the hydration reaction process of MTC plugging working fluid is affected by temperature, when the deep formation is under pressure plugging, due to the high temperature, it is investigated whether the MTC plugging working fluid of the present invention can adjust the thickening time of the MTC plugging working fluid by adjusting the amount of retarder added to meet the on-site needs. The specific method is as follows: Example 11 of the present invention (density is 1.30 g / cm 3 )、Example 15(density is 1.70g / cm 3)、Example 18(density is 2.00g / cm 3 ) and Example 21 (density 2.30 g / cm 3 ) in which the amount of the raw material retarder is 3.0%, Example 22 of the present invention (density is 1.30 g / cm 3 )、Example 23(density is 1.70g / cm 3 )、Example 24(density is 2.00g / cm 3 ) and Example 25 (density 2.30 g / cm 3 ) in an amount of 0.5% of the raw material retarder. The thickening performance test was carried out on the MTC plugging working fluids prepared in Examples 22 to 25 of the present invention at low temperatures of 30°C and 50°C. The thickening performance test was carried out on the MTC plugging working fluids prepared in Examples 11, 15, 18 and 21 of the present invention at high temperatures of 70°C and 80°C.

[0064] Test results: The raw material formulas of each embodiment are shown in Table 5, and the thickening performance results are shown in Table 6. It can be seen from Table 6 that under low temperature conditions, the activity of slag is weak and the hydrolysis and hydration speed is slow. By reducing the amount of retarder, the thickening time of the system can be flexibly adjusted; under high temperature and high density conditions, the solid content increases, and increasing the amount of retarder can delay the hydration reaction effect. This shows that the thickening time of the MTC plugging working fluid of the present invention is adjustable and is suitable for deeper and higher temperature formations.

[0065] Test 4: Compatibility evaluation Test method: Investigate the compatibility of the MTC plugging working fluid of the present invention with water-based drilling fluid at different ratios. Investigate the compatibility of the MTC plugging working fluid prepared in Example 21 of the present invention and the water-based drilling fluid after mixing at a volume ratio of 1:3, 1:1 and 3:1 at 90°C. At the same time, the water-based drilling fluid (formula: 100 parts of water, 4 parts of sodium bentonite, 2 parts of potassium polyacrylate, 0.15 parts of hydrolyzed polyacrylonitrile HPAN, 0.1 parts of medium molecular polymer MAN-101, 5 parts of sulfonated asphalt SAS, 2 parts of ultrafine calcium carbonate QS-2, 0.5 parts of lubricant RH-3 and 0.5 parts of detergent RH-4) was used as a control. The compatibility test indicators include viscosity, rheological parameters and thickening test.

[0066] Test results: The test results of viscosity and rheological parameters are shown in Table 7. As shown in Table 7, the mixed slurry obtained by mixing the MTC plugging working fluid of the present invention with the water-based drilling fluid in various proportions does not show flocculation, thickening and false coagulation. At the same time, as the proportion of the MTC plugging working fluid increases, the rheological properties of the mixed slurry are better, which is more conducive to stabilizing the colloidal properties of the water-based drilling fluid.

[0067] Thickening test results Table 8, Figures 1 to 3As shown, Figures 1 to 3 The thickening performance diagrams of the MTC plugging working fluid prepared in Example 21 of the present invention and the water-based drilling fluid at a volume ratio of 1:3, 1:1 and 3:1 at 90°C are shown in Table 8. Figures 1 to 3 It can be seen that the slurry obtained by mixing the MTC plugging working fluid of the present invention with the water-based drilling fluid in various proportions has an increased initial consistency, but the thickening time of the slurry is greater than the thickening time of the MTC plugging working fluid of the present invention, that is, the thickening time of the slurry is later than that of the MTC plugging working fluid, which is sufficient to meet the requirements of on-site construction. Therefore, the combination of viscosity, rheological parameters and thickening test data is sufficient to show that the compatibility of the MTC plugging working fluid of the present invention with the water-based drilling fluid is good.

[0068] Test 5: Evaluation of cured product strength Test method: The compressive strength of the solidified product after curing of the MTC plugging working fluid prepared in Examples 11, 15, 18 and 21 of the present invention was examined. The examination of the solidified product strength includes: the effect of curing temperature on the solidified product strength and the effect of curing time on the solidified product strength.

[0069] Effect of curing temperature on the strength of the solidified product: The strength of the solidified product obtained by curing the MTC plugging working fluids prepared in Examples 11, 15, 18 and 21 of the present invention at different curing temperatures of 30°C, 50°C, 70°C and 90°C for 24 hours was investigated.

[0070] Test results: The effect of curing temperature on the strength of the solidified product is shown in Table 9. It can be seen from Table 9 that the MTC plugging working fluid of the present invention can form a solidified product with strong compressive strength within 24 hours at a curing temperature above 50°C. Moreover, as the temperature rises, the strength shows a trend of first increasing and then decreasing. When the curing temperature of the MTC plugging working fluid of the present invention is within the range of 50°C to 90°C, its compressive strength is above 6MPa to 7MPa, which meets the on-site requirements.

[0071] Effect of curing time on the strength of the solidified product: The strength of the solidified product obtained by the MTC plugging working fluid prepared in Examples 11, 15, 18 and 21 of the present invention at different curing times of 1d, 2d, 3d, 4d, 5d, 6d, 8d, 10d, 20d and 30d and at a curing temperature of 70°C was investigated.

[0072] Test results: The effect of curing time on the strength of the solidified material is shown in Table 10. It can be seen from Table 10 that within 3 days of curing of the MTC plugging working fluid of the present invention, the compressive strength of the solidified material increases rapidly. From 3 to 4 days of curing, the rate of increase of the compressive strength slows down significantly. After 30 days of curing, the solidified material remains basically stable, and its compressive performance does not decline significantly.

[0073] Combining the effects of curing temperature and curing time on the strength of the solidified material, it can be seen that the MTC plugging working fluid of the present invention can maintain long-term plugging of the leakage channel.

[0074] In summary, the present invention has designed an MTC plugging working fluid with good compatibility, wide density range, strong slurry suspension stability, flexible and adjustable thickening time, enhanced solidified body strength and long-term stability through the selected suspending agent, density regulator, activator and retarder components, which ensures the cementing quality and effectively solves the problem of insufficient solidified body strength of the MTC plugging working fluid.

[0075] 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.

Claims

1. A MTC plugging working fluid, characterized in that The raw materials include slag. Taking the weight of the slag as 100%, the raw materials also include 85% drilling fluid, 15% water, 2.0% to 3.2% suspending agent, 5.0% to 8.0% compound activator, 0% to 160% density regulator and 0% to 3.0% retarder by weight; wherein the suspending agent includes 1.5% to 2.0% suspending agent polymer and 0.5% to 1.2% sodium bentonite.

2. The MTC plugging working fluid according to claim 1, characterized in that Suspending agent polymer, obtained by the following method: S1, under a nitrogen atmosphere, adjusting the pH of deionized water, and sequentially adding 2 to 3 parts of acrylamide, 12 to 13 parts of 2-acrylamido-2-methylpropanesulfonic acid, and 1 to 2 parts of N-isopropylmethacrylamide to 60 parts of deionized water after the pH is adjusted, and stirring evenly to obtain a mixed material; S2, adding 0.5 to 0.6 parts of ammonium persulfate and 0.2 to 0.3 parts of N,N-methylenebisacrylamide dropwise to the mixed material to react to obtain a reaction product, and then washing, drying and crushing the reaction product to obtain a suspension polymer.

3. The MTC plugging working fluid according to claim 2, characterized in that Step S1, adjusting the pH value of deionized water to 7 to 9 with sodium hydroxide; or / and, step S2, the reaction temperature is 65° C. to 75° C., and the reaction product is rinsed with ethanol 2 to 3 times.

4. The MTC plugging working fluid according to any one of claims 1 to 3, characterized in that The compound activator is a mixture of activator JHJ-A and activator JHJ-B in a mass ratio of 1.5:6.

0.

5. The MTC plugging working fluid according to claim 4, characterized in that The compound activator JHJ-A is a mixture of sodium hydroxide, sodium carbonate and triethanolamine in a mass ratio of 23:8:0.8, and the compound activator JHJ-B is a mixture of sodium silicate and calcium sulfate in a mass ratio of 2:

1.

6. The MTC plugging working fluid according to any one of claims 1 to 5, characterized in that Density modifier is a kind of lightening agent and weighting agent.

7. The MTC plugging working fluid according to claim 6, characterized in that The lightening agent is floating beads, and the weighting agent is one of barite and hematite powder.

8. The MTC plugging working fluid according to any one of claims 1 to 7, characterized in that The retarder is retarder XZ-HN1.

9. The MTC plugging working fluid according to any one of claims 1 to 8, characterized in that The method is as follows: add a required amount of suspending agent, compound activator, density regulator and retarder to a required amount of water to obtain a mixed solution, add a required amount of drilling fluid and slag to the mixed solution to obtain an MTC plugging working fluid.

10. A method for preparing the MTC plugging working fluid according to any one of claims 1 to 8, characterized in that The method is as follows: add the required amount of suspending agent, compound activator, density regulator and retarder to the required amount of water to obtain a mixed solution, add the required amount of drilling fluid and slag to the mixed solution to obtain an MTC plugging working fluid.

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