A high temperature resistant potassium calcium based organic drilling fluid and preparation method thereof

Abstract

The invention discloses a high temperature resistant potassium calcium based organic drilling fluid and a preparation method thereof, and belongs to the field of new material technology. The high temperature resistant potassium calcium based organic drilling fluid comprises clay, sodium carbonate, potassium hydroxide, potassium chloride, a fluid loss reducer, a coated flocculant, an organic salt, a low fluorescence lubricant, a cationic emulsified asphalt, calcium oxide, an organic salt weighting agent, modified peat soil and water, wherein the fluid loss reducer comprises a starch-based fluid loss reducer and a humic acid-based fluid loss reducer. The invention adds starch-based fluid loss reducer, humic acid-based fluid loss reducer, modified peat soil and other components on the basis of conventional drilling fluid, and while improving the high temperature resistance of the drilling fluid, it can optimize the rheological properties, lubrication properties, plugging properties and anti-loss ability of the drilling fluid, thereby improving the safety and efficiency of the drilling operation.

Description

Technical Field

[0001] The invention belongs to the technical field of new materials, and specifically relates to a high-temperature resistant potassium-calcium based organic drilling fluid and a preparation method thereof. Background Art

[0002] The development of deep and ultra-deep oil and gas reservoirs has become a future development trend. High-temperature deep well drilling operations are an important engineering guarantee for the development of deep oil and gas fields, and the high-temperature resistance of drilling fluid systems is becoming increasingly challenging.

[0003] As the depth of the well increases, the bottom temperature rises. High temperature can easily lead to the dispersion and passivation of clay in the drilling fluid and the failure of the drilling fluid treatment agent, which deteriorates the performance of the drilling fluid. Deep wells often drill through shale and coal rock formations. In addition, the open hole section is long, which can easily cause well collapse and drill stuck problems under the immersion of drilling fluid. The drilling time of the production layer is long, and the amount of drilling fluid invading the oil and gas layer is large, which is not conducive to protecting the oil and gas layer. In deep well drilling, salt-gypsum layers or other formations that are prone to pollution may be encountered. Clay, salt-gypsum, high-pressure oil and gas, and formation water in the formation may destroy the performance of the drilling fluid.

[0004] High bottom hole pressure requires high density of drilling fluid, and more weighting agents need to be added, which will increase the solid content and increase the viscosity and shear force of drilling fluid, and the problem of weighting agent sedimentation is prominent. Viscosity reducers are usually used to reduce viscosity, but viscosity reducers can generally only reduce the structural viscosity of drilling fluid. Subsequently, structural stabilizers are required to increase the shear force to suspend weighting agents, which will lead to poor rheological properties, so they often fall into a vicious cycle of "weighting-thickening-viscosity reduction-weighting agent sedimentation-density reduction-weighting again". High pressure will cause the pore pressure and fracture pressure values ​​to be very close, making the drilling fluid safe density window very small, which is easy to cause blowouts or well leakage. High drilling fluid density will not only increase the chance of differential pressure sticking, but also cause increased circulating pressure, pressure excitement, drill tool wear, and reduced drill bit service life. The degree of corrosion of drilling fluid to drilling tools will be more serious at high temperatures.

[0005] As oil and gas wells deepen, the formation temperature and pressure increase, and drilling fluids face the difficulties of high temperature and high pressure. Ordinary drilling fluids can no longer meet the requirements of drilling operations in the process of deep oil and gas exploration and development for the density, temperature, rheology, lubricity, inhibition, water loss and wall building properties of drilling fluids. In addition, well wall instability, drill bit sticking and breaking, drilling fluid leakage, reservoir creep and other conditions are also common, which has a great impact on drilling work, reducing efficiency and increasing costs. Summary of the invention

[0006] In view of the above-mentioned prior art, the present invention provides a high-temperature resistant potassium-calcium-based organic drilling fluid to solve the technical problem that the drilling fluid in the prior art has poor high-temperature resistance.

[0007] In order to achieve the above-mentioned object, the technical scheme adopted by the present invention is to provide a high temperature resistant potassium calcium based organic drilling fluid, comprising the following components in mass percentage: 4% of clay, 0.1-0.3% of sodium carbonate, 0.4-0.6% of potassium hydroxide, 6-8% of potassium chloride, 3-4% of filtrate reducer, 0.5-1% of coated flocculant, 14-16% of organic salt, 1% of low fluorescence lubricant, 2-5% of cationic emulsified asphalt, 0.3-0.5% of calcium oxide, 20-30% of organic salt weighting agent, 10-20% of modified peat soil and the balance of water;

[0008] The fluid loss reducer includes a starch-based fluid loss reducer and a humic acid-based fluid loss reducer; the starch-based fluid loss reducer is prepared by the following steps:

[0009] (1) Mix starch and water in a mass ratio of 8-12:75-85, and stir at 30-50° C. for 10-20 min to obtain a starch solution;

[0010] (2) adding diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to the starch solution, stirring at 30-50° C. for 10-20 min, and then adjusting the pH of the solution to 4-6 to obtain a polymerization base liquid; the mass ratio of diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to starch is 3-6:5-10:8-12:20-25;

[0011] (3) Adding an initiator to the polymerization base liquid, mixing well, reacting at 40-50°C for 1-3 hours, and then drying and crushing to obtain the product; the initiator is sodium persulfate or potassium persulfate, and the amount added is 3-5% of the mass of starch;

[0012] Humic acid-based fluid loss additive is prepared by the following steps:

[0013] (1) mixing sodium humate with water at a solid-liquid ratio of 3-5 g:10 mL to obtain a sodium humate solution;

[0014] (2) adding sodium p-styrene sulfonate and an initiator to a sodium humate solution, adjusting the pH of the reaction system to 5-6, and then reacting at 65-75° C. for 2-5 hours, and then drying and crushing to obtain the product; the mass ratio of sodium p-styrene sulfonate and the initiator to sodium humate is 1-3:0.05-0.1:1-3, and the initiator is sodium persulfate or potassium persulfate;

[0015] Modified peat soil is prepared by the following steps:

[0016] S1: preparing potassium salt and calcium salt into solutions respectively;

[0017] S2: Spray the potassium salt solution into the peat soil 3 to 5 times. After each spraying, leave it to stand and cure at 20 to 40°C for 30 to 60 minutes.

[0018] S3: Spray the calcium salt solution into the peat soil treated by S2 for 3 to 5 times. After each spraying, leave it to stand and cure at 20 to 40°C for 30 to 60 minutes.

[0019] S4: Dry the peat soil treated by S3 at 20-30°C until the moisture content is less than 10%, and then crush it into particles with a particle size less than 100 mesh.

[0020] The beneficial effect of the technical solution of the present invention is that a special fluid loss reducer is added to conventional drilling fluid, and the fluid loss reducer in the present invention includes a starch-based fluid loss reducer and a humic acid-based fluid loss reducer. Among them, the starch-based fluid loss reducer is obtained by polymerizing starch with diallyldimethylammonium chloride (DMDAAC), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and acrylamide (AM). The introduction of DMDAAC makes the starch main chain carry cationic groups, which can effectively adsorb clay particles in drill cuttings, not only forming a stable filter cake on the well wall, but also preventing the deposit of drill cuttings in the wellbore, thereby improving drilling efficiency; after grafting AMPS, the sulfonic acid group in AMPS gives it strong anionicity, which enables the grafted copolymer to better interact with the cationic substances in the drilling fluid to form a stable hydration film, thereby improving the stability of the drilling fluid; and the amide group introduced by AM can make starch have good hydrolysis stability, and can maintain its performance stability under different pH values ​​and temperature conditions; in addition, the introduction of AMPS and AM makes starch show excellent salt resistance, and can maintain its fluid loss reduction effect in a high salinity environment. Humic acid-based fluid loss reducer is obtained by polymerization of sodium humate and sodium styrene sulfonate (SSS). SSS introduces benzene ring structure into the molecular structure of humic acid, which improves the rigidity of the molecule, effectively hinders the thermal motion of molecular chain segments, and weakens the dehydration ability of the molecule, thereby improving the temperature and salt resistance of the fluid loss reducer. In addition, the sulfonic acid group of SSS gives it strong anionicity. After grafting with sodium humate, the copolymer can more effectively interact with cationic substances (such as calcium ions, magnesium ions, etc.) in the drilling fluid to form a more stable adsorption hydration layer, thereby enhancing the stability of the drilling fluid and reducing the fluid loss.

[0021] The present invention also adds modified peat in the drilling fluid, and peat contains organic matter and humus, which can increase the viscosity and consistency of the drilling fluid, so that it can better suspend and carry drill cuttings, prevent drill cuttings from depositing in the borehole, and improve drilling efficiency; At the same time, the fine particles and organic matter in the peat can form a dense filter cake, which can effectively prevent the water and solid particles in the drilling fluid from penetrating into the stratum, thereby reducing the filtration loss and protecting the well wall stability; In addition, peat, as a natural organic material, has good biodegradability and will not cause long-term pollution to groundwater and soil. Compared with traditional chemical additives, peat has obvious advantages in environmental protection. The peat in the present invention is also modified by potassium salt and calcium salt, and potassium salt and calcium salt are formulated into solution during modification, and potassium salt and calcium salt solution are mixed into peat by spraying, and curing is carried out at a relatively low temperature at the same time, while fully ensuring that potassium ions and calcium ions enter peat, the organic matter of peat will not be destroyed, and the characteristics of peat itself are retained. Modified peat soil releases K during drilling + and Ca 2 + , K + It has a significant effect on inhibiting clay expansion and dispersion. The clay minerals in peat soil can be better absorbed by K + Ion stabilization reduces the instability of the wellbore caused by clay expansion. In addition, K + It helps to improve the dispersion of peat soil particles in the drilling fluid, increase the viscosity and shear force of the drilling fluid, enable the drilling fluid to carry rock cuttings better, and reduce the risk of sand settling and drilling. + It will also improve the charge distribution and hydration film thickness on the surface of peat soil particles, making peat soil have excellent high temperature stability, thereby improving the high temperature resistance of drilling fluid; 2+ It can increase the cohesion between peat soil particles and reduce the collapse of soil pores, thereby improving the physical stability of peat soil at high temperatures, thereby improving the high temperature resistance of drilling fluids; at the same time, Ca 2+ It helps the fine particles in peat soil to form a granular structure, which can form a dense structure on the well wall and effectively prevent the loss of water in the drilling fluid.

[0022] The present invention can significantly improve the high temperature resistance of the drilling fluid by combining modified peat soil and a fluid loss reducer with clay, sodium carbonate, potassium hydroxide, potassium chloride, a coated flocculant, calcium oxide, a low-fluorescence lubricant, an organic salt weighting agent and other components, and can also optimize the rheological properties, lubrication properties, plugging properties and anti-loss ability of the drilling fluid, thereby improving the safety and efficiency of the drilling operation.

[0023] Based on the above technical solution, the present invention can also be improved as follows.

[0024] Furthermore, the mass ratio of the starch-based fluid loss additive to the humic acid-based fluid loss additive is 3-5:15-20.

[0025] Furthermore, the starch is corn starch.

[0026] Furthermore, the coated flocculant is polyacrylamide.

[0027] Furthermore, the organic salt is OS-100.

[0028] Further, the organic salt weighting agent includes the following components in weight percentage:

[0029] 2.5-5% organic salt, 0.05-0.1% surfactant, 0.5-1.5% modified attapulgite, 0.5-1.0% corrosion inhibitor, and the balance is sodium sulfate, potassium silicate and potassium citrate in a weight ratio of 0.5-1:0.5-1:1.5-1.8; the organic salt is sodium acetate;

[0030] The preparation method of the modified attapulgite is as follows:

[0031] (1) crushing and dissolving the attapulgite, adding a silane coupling agent at 35-50° C., stirring evenly, and ultrasonicating for 5-20 min;

[0032] (2) After the ultrasonic treatment, coconut oil diethanolamide was added, and the reaction was continued for 10 to 15 hours, and then the mixture was dried and crushed to obtain a modified attapulgite; the amount of coconut oil diethanolamide added was 30 to 50% of the weight of the attapulgite.

[0033] Furthermore, the corrosion inhibitor is sodium gluconate; and the surfactant is sodium dodecyl sulfate.

[0034] Furthermore, the potassium salt in S1 is potassium carbonate, and the concentration of the potassium salt solution prepared therefrom is 0.9-1.1 g / mL; the calcium salt is calcium bicarbonate, and the concentration of the calcium salt solution prepared therefrom is 0.1-0.3 g / mL.

[0035] Furthermore, the liquid-to-material ratio of the potassium salt solution sprayed in S2 to the peat soil is 1 mL:2-5 g; the liquid-to-material ratio of the calcium salt solution sprayed in S3 to the peat soil is 1 mL:5-10 g.

[0036] The present invention also discloses a method for preparing the high temperature resistant potassium calcium based organic drilling fluid, comprising the following steps:

[0037] S1: Dissolve the formulated amount of sodium carbonate and potassium hydroxide in water, then add the formulated amount of sakanoka, cationic emulsified asphalt and modified peat soil, mix well and soak for 16-24 hours to obtain the base liquid;

[0038] S2: Add the formulated amount of potassium chloride, fluid loss reducer, coated flocculant, organic salt, low fluorescence lubricant, calcium oxide and organic salt weighting agent into the base liquid and mix well.

[0039] The beneficial effects of the present invention are:

[0040] 1. The present invention adds starch-based fluid loss reducer, humic acid-based fluid loss reducer, modified peat soil and other components to conventional drilling fluid, which can improve the high temperature resistance of the drilling fluid while optimizing the rheological properties, lubrication properties, plugging properties and anti-loss ability of the drilling fluid, thereby improving the safety and efficiency of drilling operations.

[0041] 2. In the present invention, potassium salt and calcium salt are used to modify peat soil. The modification method is simple and does not introduce impurity ions. Introducing potassium ions and calcium ions into peat soil can improve the high temperature resistance of peat soil, thereby improving the high temperature resistance and other properties of drilling fluid. DETAILED DESCRIPTION

[0042] The peat soil used in the present invention comes from the Bosten Lake peat deposit.

[0043] The organic salt used may be an organic salt commonly used in the art. The organic salt used in the embodiment of the present invention is OS-100. OS-100 is described in detail in "Indoor Research on New Clay-Free Low-Solid Phase Organic Salt Drilling Fluid" (Zhou Changhong et al., Drilling Fluids and Completion Fluids, November 2007, Vol. 24, No. 6, pp. 22-24), so it will not be described in detail in the present invention.

[0044] All existing cationic emulsified asphalts are suitable for the present invention. The cationic emulsified asphalt used in the embodiments of the present invention is a product of Karamay Yien Technology Service Co., Ltd. The specific composition of the product refers to the patent "A Cationic Emulsified Asphalt for Drilling Fluid and Its Preparation Method" (Patent No.: ZL 202410021657.X, Authorization Announcement No.: CN 117534967B).

[0045] All existing low-fluorescence lubricants are suitable for the present invention. The low-fluorescence lubricant used in the embodiment of the present invention is JY polyol, a low-fluorescence lubricant for drilling fluid from Nanjing Changjiang Jiangyu Energy Technology Co., Ltd.

[0046] All existing organic salt weighting agents are suitable for the present invention. However, in order to make the performance of the drilling fluid better, the present invention preferably uses the product of Karamay Yien Technology Service Co., Ltd. The specific composition of the product refers to the patent "A water-soluble organic salt weighting agent for drilling fluid and its preparation method" (patent number: ZL 202410191996.2, authorization announcement number: CN117736706 B). Specifically, the organic salt weighting agent includes the following components in weight percentage:

[0047] 2.5-5% organic salt, 0.05-0.1% surfactant, 0.5-1.5% modified attapulgite, 0.5-1.0% corrosion inhibitor, and the balance is sodium sulfate, potassium silicate and potassium citrate in a weight ratio of 0.5-1:0.5-1:1.5-1.8; the organic salt is sodium acetate; wherein the corrosion inhibitor is sodium gluconate; the surfactant is sodium dodecyl sulfate; the preparation method of the modified attapulgite is:

[0048] (1) crushing and dissolving the attapulgite, adding a silane coupling agent at 35-50° C., stirring evenly, and ultrasonicating for 5-20 min;

[0049] (2) After the ultrasonic treatment, coconut oil diethanolamide was added, and the reaction was continued for 10 to 15 hours, and then the mixture was dried and crushed to obtain a modified attapulgite; the amount of coconut oil diethanolamide added was 30 to 50% of the weight of the attapulgite.

[0050] The remaining raw materials used in the examples are conventional raw materials and are not specifically limited thereto.

[0051] The specific implementation modes of the present invention are described in detail below with reference to the embodiments.

[0052] Example 1

[0053] A high temperature resistant potassium calcium based organic drilling fluid, comprising the following components in percentage by mass: 4% of clay, 0.2% of sodium carbonate, 0.5% of potassium hydroxide, 7% of potassium chloride, 3.8% of fluid loss reducer, 0.8% of polyacrylamide, 15% of OS-100, 1% of JY polymer alcohol, 3% of cationic emulsified asphalt, 0.4% of calcium oxide, 25% of organic salt weighting agent, 15% of modified peat soil and the balance of water;

[0054] The fluid loss reducer used in this embodiment is prepared by mixing a starch-based fluid loss reducer and a humic acid-based fluid loss reducer in a mass ratio of 4:15; the starch-based fluid loss reducer is prepared by the following steps:

[0055] (1) corn starch and water were mixed in a mass ratio of 10:80, and stirred at 40° C. for 15 min to obtain a starch solution;

[0056] (2) adding diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to the starch solution, stirring at 40° C. for 15 minutes, and then adjusting the pH of the solution to 5 to obtain a polymerization base liquid; the mass ratio of diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to starch is 5:8:10:24;

[0057] (3) adding sodium persulfate to the polymer base liquid in an amount of 4% of the mass of the starch, mixing well, reacting at 45° C. for 2 h, drying at 80° C., and then crushing into particles with a particle size of less than 100 mesh, to obtain;

[0058] Humic acid-based fluid loss additive is prepared by the following steps:

[0059] (1) mixing sodium humate with water at a solid-liquid ratio of 4 g:10 mL to obtain a sodium humate solution;

[0060] (2) adding sodium p-styrene sulfonate and sodium persulfate to the sodium humate solution, adjusting the pH of the reaction system to 6, reacting at 70° C. for 4 h, drying at 70° C., and then crushing into particles with a particle size of less than 100 mesh, to obtain; the mass ratio of sodium p-styrene sulfonate and sodium persulfate to sodium humate is 2:0.08:2;

[0061] Modified peat soil is prepared by the following steps:

[0062] S1: Dissolve potassium carbonate in water to prepare a potassium salt solution with a concentration of 1 g / mL; dissolve calcium bicarbonate in water to prepare a calcium salt solution with a concentration of 0.2 g / mL;

[0063] S2: Mix the potassium salt solution with peat soil at a solid-liquid ratio of 3g:1mL; spray the potassium salt solution into the peat soil in 4 times, and keep it at 25°C for 45 minutes after each spraying of the potassium salt solution;

[0064] S3: Mix the calcium salt solution with peat soil at a solid-liquid ratio of 8g:1mL; the calcium salt solution is sprayed into the peat soil treated by S2, and the spraying is carried out 4 times. Each time the calcium salt solution is sprayed, it is left to stand and cured at 25°C for 45 minutes;

[0065] S4: Dry the peat soil treated by S3 at 25°C until the moisture content is less than 10%, and then crush it into particles with a particle size less than 100 mesh.

[0066] The high temperature resistant potassium calcium based organic drilling fluid in this embodiment is prepared by the following steps:

[0067] S1: Dissolve the formulated amount of sodium carbonate and potassium hydroxide in water, then add the formulated amount of sakanoka, cationic emulsified asphalt and modified peat soil, mix well and soak for 20 hours to obtain the base liquid;

[0068] S2: Add the formulated amount of potassium chloride, fluid loss reducer, polyacrylamide, OS-100, JY polyol, calcium oxide and organic salt weighting agent into the base liquid and mix well to obtain.

[0069] Example 2

[0070] A high temperature resistant potassium calcium based organic drilling fluid, comprising the following components in percentage by mass: 4% of clay, 0.1% of sodium carbonate, 0.6% of potassium hydroxide, 6% of potassium chloride, 4% of fluid loss reducer, 0.5% of polyacrylamide, 15% of OS-100, 1% of JY polymer alcohol, 2% of cationic emulsified asphalt, 0.5% of calcium oxide, 30% of organic salt weighting agent, 10% of modified peat soil and the balance of water;

[0071] The fluid loss reducer used in this embodiment is prepared by mixing a starch-based fluid loss reducer and a humic acid-based fluid loss reducer in a mass ratio of 5:20; the starch-based fluid loss reducer is prepared by the following steps:

[0072] (1) corn starch and water were mixed in a mass ratio of 8:75, and stirred at 30° C. for 20 min to obtain a starch solution;

[0073] (2) adding diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to the starch solution, stirring at 50° C. for 10 min, and then adjusting the pH of the solution to 4 to obtain a polymerization base liquid; the mass ratio of diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to starch is 3:10:8:25;

[0074] (3) adding potassium persulfate to the polymer base liquid in an amount of 3% of the mass of the starch, mixing well, reacting at 40° C. for 3 h, drying at 80° C., and then crushing into particles with a particle size of less than 100 mesh, to obtain;

[0075] Humic acid-based fluid loss additive is prepared by the following steps:

[0076] (1) mixing sodium humate with water at a solid-liquid ratio of 3 g:10 mL to obtain a sodium humate solution;

[0077] (2) adding sodium p-styrene sulfonate and sodium persulfate to the sodium humate solution, adjusting the pH of the reaction system to 5, reacting at 65° C. for 5 h, drying at 70° C., and then crushing into particles with a particle size of less than 100 mesh, to obtain; the mass ratio of sodium p-styrene sulfonate and sodium persulfate to sodium humate is 1:0.05:3;

[0078] Modified peat soil is prepared by the following steps:

[0079] S1: Dissolve potassium carbonate in water to prepare a potassium salt solution with a concentration of 1.1 g / mL; dissolve calcium bicarbonate in water to prepare a calcium salt solution with a concentration of 0.1 g / mL;

[0080] S2: Mix the potassium salt solution with peat soil at a solid-liquid ratio of 2g:1mL; spray the potassium salt solution into the peat soil in three times, and keep it at 20°C for 60 minutes after each spraying of the potassium salt solution;

[0081] S3: Mix the calcium salt solution with peat soil at a solid-liquid ratio of 5g:1mL; the calcium salt solution is sprayed into the peat soil treated by S2, and the spraying is carried out 5 times. Each time the calcium salt solution is sprayed, it is left to stand and cured at 30°C for 30 minutes;

[0082] S4: Dry the peat soil treated by S3 at 20°C until the moisture content is less than 10%, and then crush it into particles with a particle size less than 100 mesh.

[0083] The high temperature resistant potassium calcium based organic drilling fluid in this embodiment is prepared by the following steps:

[0084] S1: Dissolve the formulated amount of sodium carbonate and potassium hydroxide in water, then add the formulated amount of sakanoka, cationic emulsified asphalt and modified peat soil, mix well and soak for 16 hours to obtain the base liquid;

[0085] S2: Add the formulated amount of potassium chloride, fluid loss reducer, polyacrylamide, OS-100, JY polyol, calcium oxide and organic salt weighting agent into the base liquid and mix well to obtain.

[0086] Example 3

[0087] A high temperature resistant potassium calcium based organic drilling fluid, comprising the following components in percentage by mass: 4% of clay, 0.3% of sodium carbonate, 0.4% of potassium hydroxide, 8% of potassium chloride, 3% of fluid loss reducer, 1% of polyacrylamide, 15% of OS-100, 1% of JY polymer alcohol, 5% of cationic emulsified asphalt, 0.3% of calcium oxide, 20% of organic salt weighting agent, 20% of modified peat soil and the balance of water;

[0088] The fluid loss reducer used in this embodiment is prepared by mixing a starch-based fluid loss reducer and a humic acid-based fluid loss reducer in a mass ratio of 3:15; the starch-based fluid loss reducer is prepared by the following steps:

[0089] (1) corn starch and water were mixed in a mass ratio of 12:85, and stirred at 50° C. for 10 min to obtain a starch solution;

[0090] (2) adding diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to the starch solution, stirring at 30° C. for 20 min, and then adjusting the pH of the solution to 6 to obtain a polymerization base liquid; the mass ratio of diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to starch is 6:5:12:20;

[0091] (3) adding potassium persulfate to the polymer base liquid in an amount of 5% of the mass of the starch, mixing well, reacting at 50° C. for 1 hour, drying at 80° C., and then crushing into particles with a particle size of less than 100 mesh, to obtain;

[0092] Humic acid-based fluid loss additive is prepared by the following steps:

[0093] (1) mixing sodium humate with water at a solid-liquid ratio of 5 g:10 mL to obtain a sodium humate solution;

[0094] (2) adding sodium p-styrene sulfonate and sodium persulfate to the sodium humate solution, adjusting the pH of the reaction system to 6, reacting at 75° C. for 2 h, drying at 70° C., and then crushing into particles with a particle size of less than 100 mesh, to obtain; the mass ratio of sodium p-styrene sulfonate and sodium persulfate to sodium humate is 3:0.1:3;

[0095] Modified peat soil is prepared by the following steps:

[0096] S1: Dissolve potassium carbonate in water to prepare a potassium salt solution with a concentration of 0.9 g / mL; dissolve calcium bicarbonate in water to prepare a calcium salt solution with a concentration of 0.3 g / mL;

[0097] S2: Mix the potassium salt solution with peat soil at a solid-liquid ratio of 5g:1mL; spray the potassium salt solution into the peat soil in 5 times, and keep it at 30°C for 30 minutes after each spraying of the potassium salt solution;

[0098] S3: Mix the calcium salt solution with peat soil at a solid-liquid ratio of 10 g:1 mL; the calcium salt solution is sprayed into the peat soil treated by S2, and the spraying is carried out 3 times. Each time the calcium salt solution is sprayed, it is left to stand and cured at 20°C for 60 minutes;

[0099] S4: Dry the peat soil treated by S3 at 30°C until the moisture content is less than 10%, and then crush it into particles with a particle size less than 100 mesh.

[0100] The high temperature resistant potassium calcium based organic drilling fluid in this embodiment is prepared by the following steps:

[0101] S1: Dissolve the formulated amount of sodium carbonate and potassium hydroxide in water, then add the formulated amount of sakanoka, cationic emulsified asphalt and modified peat soil, mix well and soak for 24 hours to obtain the base liquid;

[0102] S2: Add the formulated amount of potassium chloride, fluid loss reducer, polyacrylamide, OS-100, JY polyol, calcium oxide and organic salt weighting agent into the base liquid and mix well to obtain.

[0103] Comparative Example 1

[0104] A high temperature resistant potassium calcium based organic drilling fluid, comprising the following components in percentage by mass: 4% of clay, 0.2% of sodium carbonate, 0.5% of potassium hydroxide, 7% of potassium chloride, 3.8% of fluid loss reducer, 0.8% of polyacrylamide, 0.5% of OS-100, 1% of JY polymer alcohol, 3% of cationic emulsified asphalt, 0.2% of calcium oxide, 25% of organic salt weighting agent, 15% of modified peat soil and the balance of water;

[0105] The fluid loss reducer used in this comparative example is WHITETROL from Shak (Tianjin) Petroleum Technology Service Co., Ltd. ® X ultra-high temperature fluid loss reducer;

[0106] Modified peat soil is prepared by the following steps:

[0107] S1: Dissolve potassium carbonate in water to prepare a potassium salt solution with a concentration of 1 g / mL; dissolve calcium bicarbonate in water to prepare a calcium salt solution with a concentration of 0.2 g / mL;

[0108] S2: Mix the potassium salt solution with peat soil at a solid-liquid ratio of 3g:1mL; spray the potassium salt solution into the peat soil in 4 times, and keep it at 25°C for 45 minutes after each spraying of the potassium salt solution;

[0109] S3: Mix the calcium salt solution with peat soil at a solid-liquid ratio of 8g:1mL; the calcium salt solution is sprayed into the peat soil treated by S2, and the spraying is carried out 4 times. Each time the calcium salt solution is sprayed, it is left to stand and cured at 25°C for 45 minutes;

[0110] S4: Dry the peat soil treated by S3 at 25°C until the moisture content is less than 10%, and then crush it into particles with a particle size less than 100 mesh.

[0111] The high temperature resistant potassium calcium based organic drilling fluid in this comparative example is prepared by the following steps:

[0112] S1: Dissolve the formulated amount of sodium carbonate and potassium hydroxide in water, then add the formulated amount of sakanoka, cationic emulsified asphalt and modified peat soil, mix well and soak for 20 hours to obtain the base liquid;

[0113] S2: Add the formulated amount of potassium chloride, fluid loss reducer, polyacrylamide, OS-100, JY polyol, calcium oxide and organic salt weighting agent into the base liquid and mix well to obtain.

[0114] Comparative Example 2

[0115] A high temperature resistant potassium calcium based organic drilling fluid, comprising the following components in percentage by mass: 4% sakazoite, 0.2% sodium carbonate, 0.5% potassium hydroxide, 7% potassium chloride, 3.8% fluid loss reducer, 0.8% polyacrylamide, 0.5% OS-100, 1% JY polyol, 3% cationic emulsified asphalt, 0.2% calcium oxide, 25% organic salt weighting agent, 15% peat soil and the balance water;

[0116] The fluid loss reducer used in this comparative example is prepared by mixing a starch-based fluid loss reducer and a humic acid-based fluid loss reducer in a mass ratio of 4:15; the starch-based fluid loss reducer is prepared by the following steps:

[0117] (1) corn starch and water were mixed in a mass ratio of 10:80, and stirred at 40° C. for 15 min to obtain a starch solution;

[0118] (2) adding diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to the starch solution, stirring at 40° C. for 15 minutes, and then adjusting the pH of the solution to 5 to obtain a polymerization base liquid; the mass ratio of diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to starch is 5:8:10:24;

[0119] (3) adding sodium persulfate to the polymer base liquid in an amount of 4% of the mass of the starch, mixing well, reacting at 45° C. for 2 h, drying at 80° C., and then crushing into particles with a particle size of less than 100 mesh, to obtain;

[0120] Humic acid-based fluid loss additive is prepared by the following steps:

[0121] (1) mixing sodium humate with water at a solid-liquid ratio of 4 g:10 mL to obtain a sodium humate solution;

[0122] (2) adding sodium p-styrene sulfonate and sodium persulfate to the sodium humate solution, adjusting the pH of the reaction system to 6, and then reacting at 70° C. for 4 hours, and then drying at 70° C., and then crushing into particles with a particle size of less than 100 mesh, to obtain; the mass ratio of sodium p-styrene sulfonate and sodium persulfate to sodium humate is 2:0.08:2.

[0123] The high temperature resistant potassium calcium based organic drilling fluid in this comparative example is prepared by the following steps:

[0124] S1: Dissolve the formulated amount of sodium carbonate and potassium hydroxide in water, then add the formulated amount of sakanoka, cationic emulsified asphalt and peat soil, mix well and soak for 20 hours to obtain the base liquid;

[0125] S2: Add the formulated amount of potassium chloride, fluid loss reducer, polyacrylamide, OS-100, JY polyol, calcium oxide and organic salt weighting agent into the base liquid and mix well to obtain.

[0126] Comparative Example 3

[0127] A high temperature resistant potassium calcium based organic drilling fluid, comprising the following components in percentage by mass: 4% of sakanoclay, 0.2% of sodium carbonate, 0.5% of potassium hydroxide, 7% of potassium chloride, 3.8% of fluid loss reducer, 0.8% of polyacrylamide, 0.5% of OS-100, 1% of JY polymer alcohol, 3% of cationic emulsified asphalt, 0.2% of calcium oxide, 25% of organic salt weighting agent and the balance of water;

[0128] The fluid loss reducer used in this comparative example is prepared by mixing a starch-based fluid loss reducer and a humic acid-based fluid loss reducer in a mass ratio of 4:15; the starch-based fluid loss reducer is prepared by the following steps:

[0129] (1) corn starch and water were mixed in a mass ratio of 10:80, and stirred at 40° C. for 15 min to obtain a starch solution;

[0130] (2) adding diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to the starch solution, stirring at 40° C. for 15 minutes, and then adjusting the pH of the solution to 5 to obtain a polymerization base liquid; the mass ratio of diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to starch is 5:8:10:24;

[0131] (3) adding sodium persulfate to the polymer base liquid in an amount of 4% of the mass of the starch, mixing well, reacting at 45° C. for 2 h, drying at 80° C., and then crushing into particles with a particle size of less than 100 mesh, to obtain;

[0132] Humic acid-based fluid loss additive is prepared by the following steps:

[0133] (1) mixing sodium humate with water at a solid-liquid ratio of 4 g:10 mL to obtain a sodium humate solution;

[0134] (2) adding sodium p-styrene sulfonate and sodium persulfate to the sodium humate solution, adjusting the pH of the reaction system to 6, and then reacting at 70° C. for 4 hours, and then drying at 70° C., and then crushing into particles with a particle size of less than 100 mesh, to obtain; the mass ratio of sodium p-styrene sulfonate and sodium persulfate to sodium humate is 2:0.08:2.

[0135] The high temperature resistant potassium calcium based organic drilling fluid in this comparative example is prepared by the following steps:

[0136] S1: Dissolve the formulated amount of sodium carbonate and potassium hydroxide in water, then add the formulated amount of clay and cationic emulsified asphalt, mix well and soak for 20 hours to obtain the base liquid;

[0137] S2: Add the formulated amount of potassium chloride, fluid loss reducer, polyacrylamide, OS-100, JY polyol, calcium oxide and organic salt weighting agent into the base liquid and mix well to obtain.

[0138] Experimental example

[0139] The room temperature performance of the high temperature resistant potassium calcium based organic drilling fluids in the above embodiments and comparative examples was tested using the detection method described in GB / T 29170-2012 Laboratory Test of Drilling Fluids in the Petroleum and Natural Gas Industry. The results are shown in Table 1.

[0140] Table 1 Performance test results of high temperature resistant potassium calcium based organic drilling fluid

[0141]

[0142]

[0143] As can be seen from Table 1, the high temperature resistant potassium calcium based organic drilling fluid (Examples 1 to 3) of the present invention has a suitable viscosity, can better suspend and carry drill cuttings, prevent drill cuttings from depositing in the wellbore, and improve drilling efficiency. It also has a good lubrication coefficient, can effectively reduce the friction resistance between the drill tool and the well wall, and reduce the wear of the drill bit. At the same time, after aging at 120°C and 150°C, the medium pressure water loss and high temperature and high pressure water loss of the drilling fluid are only a small amount, which meets the requirements; and, compared with the drilling fluid before aging at 120°C and 150°C, although the viscosity of the drilling fluid in the present invention is reduced and the filtration loss is increased, the changes are not large, indicating that the well fluid in the present invention has excellent high temperature resistance.

[0144] Although the specific implementation of the present invention is described in detail in conjunction with the embodiments, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A high temperature resistant potassium calcium based organic drilling fluid, characterized in that: The invention comprises the following components in percentage by weight: 4% sakado soil, 0.1-0.3% sodium carbonate, 0.4-0.6% potassium hydroxide, 6-8% potassium chloride, 3-4% fluid loss reducer, 0.5-1% coated flocculant, 14-16% OS-100, 1% low fluorescence lubricant, 2-5% cationic emulsified asphalt, 0.3-0.5% calcium oxide, 20-30% organic salt weighting agent, 10-20% modified peat soil and the balance water; The fluid loss reducer includes a starch-based fluid loss reducer and a humic acid-based fluid loss reducer; the starch-based fluid loss reducer is prepared by the following steps: (1) Mix starch and water in a mass ratio of 8-12:75-85, and stir at 30-50° C. for 10-20 min to obtain a starch solution; (2) adding diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to the starch solution, stirring at 30-50° C. for 10-20 min, and then adjusting the pH of the solution to 4-6 to obtain a polymer base liquid; the mass ratio of diallyldimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and acrylamide to starch is 3-6:5-10:8-12:20-25; (3) adding an initiator to the polymerization base liquid, mixing well, reacting at 40-50° C. for 1-3 hours, and then drying and crushing to obtain the starch; the initiator is sodium persulfate or potassium persulfate, and the amount thereof added is 3-5% of the mass of the starch; The humic acid-based fluid loss additive is prepared by the following steps: (1) mixing sodium humate with water at a solid-liquid ratio of 3-5 g:10 mL to obtain a sodium humate solution; (2) adding sodium p-styrene sulfonate and an initiator to a sodium humate solution, adjusting the pH of the reaction system to 5-6, and then reacting at 65-75° C. for 2-5 hours, and then drying and crushing to obtain the product; the mass ratio of the sodium p-styrene sulfonate and the initiator to the sodium humate is 1-3:0.05-0.1:1-3, and the initiator is sodium persulfate or potassium persulfate; The modified peat soil is prepared by the following steps: S1: preparing potassium salt and calcium salt into solutions respectively; S2: Spray the potassium salt solution into the peat soil 3 to 5 times. After each spraying, leave it to stand and cure at 20 to 40°C for 30 to 60 minutes. S3: Spray the calcium salt solution into the peat soil treated by S2 for 3 to 5 times. After each spraying, leave it to stand and cure at 20 to 40°C for 30 to 60 minutes. S4: Dry the peat soil treated by S3 at 20-30°C until the moisture content is less than 10%, and then crush it into particles with a particle size less than 100 mesh.

2. The high temperature resistant potassium calcium based organic drilling fluid according to claim 1, characterized in that: The mass ratio of the starch-based fluid loss agent to the humic acid-based fluid loss agent is 3-5:15-20.

3. The high temperature resistant potassium calcium based organic drilling fluid according to claim 1, characterized in that: The starch is corn starch.

4. The high temperature resistant potassium calcium based organic drilling fluid according to claim 1, characterized in that: The coated flocculant is polyacrylamide.

5. The high temperature resistant potassium calcium based organic drilling fluid according to claim 1, characterized in that: The organic salt weighting agent comprises the following components in weight percentage: 2.5-5% organic salt, 0.05-0.1% surfactant, 0.5-1.5% modified attapulgite, 0.5-1.0% corrosion inhibitor, and the balance is sodium sulfate, potassium silicate and potassium citrate in a weight ratio of 0.5-1:0.5-1:1.5-1.8; the organic salt is sodium acetate; The preparation method of the modified attapulgite is: (1) crushing and dissolving the attapulgite, adding a silane coupling agent at 35-50° C., stirring evenly, and ultrasonicating for 5-20 min; (2) After the ultrasonic treatment, add coconut oil diethanolamide, continue the reaction for 10 to 15 hours, and then dry and grind to obtain a modified attapulgite; The added amount of coconut oil diethanolamide is 30-50% of the weight of the attapulgite.

6. The high temperature resistant potassium calcium based organic drilling fluid according to claim 5, characterized in that: The corrosion inhibitor is sodium gluconate; and the surfactant is sodium dodecyl sulfate.

7. The high temperature resistant potassium calcium based organic drilling fluid according to claim 1, characterized in that: The potassium salt in S1 is potassium carbonate, and the concentration of the potassium salt solution prepared therefrom is 0.9-1.1 g / mL; the calcium salt is calcium bicarbonate, and the concentration of the calcium salt solution prepared therefrom is 0.1-0.3 g / mL.

8. The high temperature resistant potassium calcium based organic drilling fluid according to claim 7, characterized in that: The liquid-to-material ratio of the potassium salt solution sprayed in S2 to the peat soil is 1 mL:2~5 g; the liquid-to-material ratio of the calcium salt solution sprayed in S3 to the peat soil is 1 mL:5~10 g.

9. The method for preparing the high temperature resistant potassium calcium based organic drilling fluid according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1: Dissolve the formulated amount of sodium carbonate and potassium hydroxide in water, then add the formulated amount of sakanoka, cationic emulsified asphalt and modified peat soil, mix well and soak for 16-24 hours to obtain the base liquid; S2: Add the formulated amount of potassium chloride, fluid loss reducer, coated flocculant, organic salt, low fluorescence lubricant, calcium oxide and organic salt weighting agent into the base liquid and mix well.

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