High-temperature-resistant high-density drilling fluid and preparation method thereof

Abstract

The invention provides a high-density drilling fluid with high temperature resistance and a preparation method thereof, and the high-density drilling fluid comprises the following components in parts by weight: 100 parts of water; 0.5 to 4 parts of a clay substance; 1-6 parts of a non-differentiated functional long-acting treatment agent; 1-6 parts of a humic acid auxiliary material; 1-4 parts of a pH value regulator; 0 to 15 parts of salt; 200 to 250 parts of a weighting agent; the non-differentiated function long-acting treating agent is prepared by carrying out polymerization reaction on an esterified aconitic acid monomer, an itaconic acid monomer, an acrylic acid monomer and a 2-acrylamido-2-methylpropanesulfonic acid monomer according to a certain mass ratio. The high-density drilling fluid is simple in composition and preparation, the rheological property and high-temperature and high-pressure filter loss of the drilling fluid are easy to control, the long-term high-temperature stability is greatly improved, the high-density drilling fluid can be applied to drilling construction of high-temperature and high-pressure strata, the components and dosage of a treating agent are greatly reduced, and the long-term high-temperature stability of the high-temperature and high-density drilling fluid is improved; and well drilling construction is facilitated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of oil and gas exploration and development, and particularly relates to a high-density drilling fluid with simple components and high temperature resistance and a preparation method thereof. BACKGROUND

[0002] In order to achieve the properties of high temperature resistance and the like, a water-based drilling fluid system with a complex formula of multiple components is usually adopted. In some water-based drilling fluid systems, the types of treatment agents including a cut-adding agent, a fluid loss additive, a flow pattern regulator and the like are more than 10, and the total amount of the treatment agents is more than 20%, which leads to difficulty in determining which treatment agent is the key in the maintenance treatment. Especially for a high-density drilling fluid system with high temperature resistance, the total amount of the treatment agents is even more than 30%. Due to the large amount of the treatment agents, the cost of preparing the drilling fluid is high. In addition, the high-density drilling fluid system has poor high temperature stability, the maintenance treatment is frequent, and the comprehensive cost is difficult to reduce, which cannot meet the requirements of cost reduction and efficiency increase. A large amount of research and application have been carried out by researchers around the high-density drilling fluid with high temperature resistance. However, the long-term stability of the drilling fluid under the high temperature condition in the well has not been effectively solved, and the cost of the drilling fluid is difficult to reduce. Meanwhile, the types or amount of the treatment agents used are large, and there is a lack of low-cost and high-efficiency treatment agents, so that the drilling fluid with good suspension stability under the high temperature condition in the well, the marine deep water constant rheological drilling fluid, the green drilling fluid suitable for the environmentally sensitive areas and the water-based drilling fluid suitable for shale gas horizontal wells are still not perfect and mature.

[0003] Although the drilling fluid has a complex formula, a large amount of types of treatment agents, the high temperature stability of the drilling fluid, especially the long-term aging stability is still insufficient, and it is difficult to meet the needs of deep well drilling. It can be seen that, in view of the current problems, it is of great practical significance to carry out the exploration and research of the low-cost drilling fluid with simple components, good comprehensive performance and high efficiency, so as to break the current construction idea of the drilling fluid and promote the progress of the drilling fluid technology. SUMMARY

[0004] Therefore, the present application provides a high-density drilling fluid with high temperature resistance and a preparation method thereof, which can be applied to drilling construction under a high temperature and high pressure environment. The drilling fluid provided by the present application has simple composition and low cost, can improve the long-term high temperature stability of the high temperature and high density drilling fluid, solve the problems of poor rheological property and difficult control and maintenance, large high temperature and high pressure water loss and heavy spar settlement of the drilling fluid under the deep high temperature and high pressure formation environment, and avoid the occurrence of complex downhole conditions.

[0005] The present application provides a high-density drilling fluid with high temperature resistance, which comprises the following components in the weight parts based on 100 weight parts of water:

[0006] 100 parts of water;

[0007] 0.5-4 parts of clay substances;

[0008] 1-6 parts of non-discriminative function long-term treatment agent;

[0009] 1-6 parts of humic acid auxiliary material;

[0010] 1-4 parts of pH regulator;

[0011] 0-15 parts of salt;

[0012] 200-250 parts of weighting agent;

[0013] The non-discriminative function long-term treatment agent is an esterified aconitic acid monomer, an itaconic acid monomer, an acrylic acid monomer, and a 2-acrylamido-2-methylpropane sulfonic acid monomer, which are prepared by polymerization in a mass ratio of (70-80):(1-3):(10-20):(7-9).

[0014] Preferably, the preparation step of the non-discriminative function long-term treatment agent comprises: dissolving the esterified aconitic acid monomer, the itaconic acid monomer, the acrylic acid monomer, and the 2-acrylamido-2-methylpropane sulfonic acid monomer in water in a mass ratio, adjusting the pH value to 7-8, and performing polymerization in the presence of an initiator, with a reaction temperature of 20-60°C and a reaction time of 0.5-2h.

[0015] Preferably, the clay substance is at least one of bentonite, attapulgite, and sepiolite.

[0016] Preferably, the pH regulator is one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, and sodium carbonate.

[0017] Preferably, the salt is an optional component, and is at least one of sodium chloride and potassium chloride.

[0018] Preferably, the weighting agent is one or more of calcium carbonate, barite, and iron ore powder.

[0019] Preferably, the high-density drilling fluid has a density of 2.0-2.2g / cm 3 and a pH value of 9-11.

[0020] The application also provides a preparation method of the high-density drilling fluid with high temperature resistance as described above, comprising the following steps:

[0021] Mixing the clay substance with water to prepare a base slurry, and curing for at least 15h;

[0022] Mixing the base slurry obtained after curing with the non-discriminative function long-term treatment agent, the humic acid auxiliary material, the pH regulator, and optionally the salt to obtain a mixed slurry;

[0023] Mixing the mixed slurry with the weighting agent, and stirring to obtain the high-density drilling fluid with high temperature resistance.

[0024] The anti-high-temperature high-density drilling fluid system formula provided by the application takes a non-discriminative function long-term treatment agent as a core treatment agent, and cooperates with humic acid auxiliary materials, pH value regulators and clay substances, and the density can be 2.2 g / cm 3 , and the temperature resistance is above 220 DEG C; wherein the non-discriminative function long-term treatment agent is a reaction product of a partially esterified aconitic acid and monomers such as acrylic acid. The high-density drilling fluid composition provided by the application is simple in composition and preparation, the rheological property and high-temperature high-pressure filtration loss of the drilling fluid are easy to control, the long-term high-temperature stability is greatly improved compared with traditional high-temperature high-density drilling fluids, the drilling fluid can be applied to drilling construction of high-temperature high-pressure strata, the components and dosage of the treatment agent are greatly reduced, the long-term high-temperature stability of the high-temperature high-density drilling fluid is improved, and the drilling construction is facilitated. DETAILED DESCRIPTION

[0025] In order for those skilled in the art to better understand the technical solutions of the application, the application will be described in detail below with reference to specific embodiments, and the description in this part is only exemplary and explanatory, and should not have any limiting effect on the protection scope of the application.

[0026] One of the purposes of the embodiments of the application is to provide an anti-high-temperature high-density drilling fluid with simplified components, which comprises the following components in parts by weight:

[0027]

[0028] The non-discriminative function long-term treatment agent is a monomer of esterified aconitic acid, a monomer of itaconic acid, a monomer of acrylic acid and a monomer of 2-acrylamido-2-methylpropane sulfonic acid, and the mass ratio is (70-80):(1-3):(10-20):(7-9).

[0029] The non-discriminative function long-term treatment agent is obtained by polymerization reaction.

[0030] The high-density drilling fluid provided by the application has the advantages of high-temperature resistance, simplified formula composition, saving of comprehensive cost, high long-term high-temperature stability and the like, and is beneficial to meet the needs of deep well and ultra-deep well drilling.

[0031] The high-density, high-temperature resistant drilling fluid of this invention comprises: 100 parts by weight (W / V) of water; and 0.5-4 parts by weight of clay. Preferably, the amount of clay is 1-3.5 parts, for example, 2-3 parts. The clay can be selected from at least one of bentonite (sodium bentonite and / or calcium bentonite), attapulgite, and sepiolite; more preferably, sodium bentonite. The sodium bentonite can be obtained by sodiumification of natural sodium bentonite or calcium-based bentonite, and can be commercially available (compliant with SY / T 5490 drilling fluid test soil). The clay can form a basic colloidal stable system for the drilling fluid, and due to shear force suspension, it can improve the suspension stability of the drilling fluid.

[0032] Based on 100 parts of water, the preferred high-density drilling fluid contains 2-5 parts of a non-functional long-lasting treatment agent, 2-5 parts of humic acid auxiliary materials, and 1-2 parts of a pH adjuster.

[0033] The non-discriminating long-lasting treatment agent is a reaction product of partially esterified aconitic acid and monomers such as acrylic acid polymerized in a certain proportion. Its functions include adjusting the rheological properties of high-temperature, high-density drilling fluids, reducing API filtration loss and high-temperature, high-pressure filtration loss, and improving long-term high-temperature stability.

[0034] In specific embodiments of the present invention, the amount of the non-discriminating long-lasting treatment agent can be 2 parts, 2.5 parts, 3 parts, 4 parts, etc. The non-discriminating long-lasting treatment agent is prepared by polymerization reaction of esterified aconitic acid monomer, itaconic acid monomer, acrylic acid monomer, and 2-acrylamido-2-methylpropanesulfonic acid monomer in a mass ratio of (70-80):(1-3):(10-20):(7-9). In the monomer raw materials, aconitic acid (also known as propylene-1,2,3-tricarboxylic acid) is partially esterified; itaconic acid, chemically known as methylene succinic acid or methylene succinic acid, is an unsaturated dicarboxylic acid. The reaction structural formulas of the non-discriminating long-lasting treatment agent in some embodiments are as follows:

[0035]

[0036] The above synthesis steps are as follows: Esterified aconitic acid monomer, itaconic acid monomer, acrylic acid monomer, and 2-acrylamido-2-methylpropanesulfonic acid monomer are dissolved in an appropriate amount of water in a mass ratio of (70-80):(1-3):(10-20):(7-9). The pH value is preferably adjusted to 7-8 by using 40% potassium hydroxide solution. An appropriate amount of initiator is slowly added while stirring continuously. The initiation temperature is 20-60℃, preferably 30-50℃, and the reaction time can be 0.5-2h to obtain the target product. The apparent viscosity of its 1% mass concentration aqueous solution can be 40-45 mPa·s.

[0037] Furthermore, the high-density drilling fluid system resistant to high temperatures includes a certain amount of humic acid-based auxiliary materials, preferably 2-4 parts by weight. The humic acid-based auxiliary materials described in this invention are humic acid-modified materials, specifically existing sulfonated lignite materials; their functions include assisting non-discriminatory long-acting treatment agents in improving rheology and reducing high-temperature, high-pressure filtration loss. Specifically, sulfonated lignite (SMC) is a derivative of lignite humic acid, synthesized from lignite under conditions such as sulfonation agents and appropriate temperatures. Its appearance can be a brownish-black or dark brown powder, with a dry basis humic acid content ≥45%, no dry basis total chromium, and a sulfonation degree ≥10.0%. In this invention, the auxiliary material is preferably sulfonated lignite, which is beneficial for drilling fluid dispersion, assists in improving rheology, and reduces high-temperature, high-pressure filtration loss.

[0038] According to some embodiments of the present invention, the pH adjuster can maintain the pH of the drilling fluid at 9 to 11. The pH adjusters commonly used in the art are applicable, specifically sodium carbonate or potassium carbonate, sodium hydroxide or potassium hydroxide; sodium hydroxide or potassium hydroxide is preferred.

[0039] Furthermore, the high-density drilling fluid described in some embodiments of the present invention includes up to 15 parts of salt, such as 6-15 parts of salt, or may not include salt (0 parts of salt); the salt may be at least one of sodium chloride or potassium chloride. That is, the salt is an optional component, and the formulation of fresh water or brine drilling fluid is determined according to the salinity of the formation encountered during drilling. If the formation does not contain salt deposits or brine layers, fresh water drilling fluid can be used; if it contains salt deposits or is a formation prone to collapse, polysulfonated potassium salt drilling fluid can be selected.

[0040] The high-density drilling fluid formulation also includes 200-250 parts of a weighting agent, which is selected from at least one of barite, iron ore powder, and calcium carbonate; barite is preferred. Barite is the most common mineral of barium, and its main component is barium sulfate; iron ore powder is a mineral powder produced by processing iron ore (ore containing iron elements or iron compounds) through beneficiation, crushing, sorting, grinding, etc., including magnetite powder, hematite powder, limonite powder, etc.

[0041] The weighting agent described in this embodiment of the invention is determined based on the required formation pressure and drilling fluid density. Specifically, as is known to those skilled in the art, higher formation pressure necessitates a higher drilling fluid density to balance it during drilling. For example, if the formation pressure coefficient is 2.0, the required drilling fluid density is generally between 2.0 and 2.2 g / cm³. 3 Then it is necessary to add an amount with a density of 4.1–4.3 g / cm³. 3 The amount of barite is 140-160 parts per 100 parts of water. If there are large sections of salt deposits, saturated brine drilling fluid is required, which means adding 35 parts of salt per 100 parts of water.

[0042] The second objective of this invention is to provide a method for preparing a high-density drilling fluid with simplified components and high temperature resistance.

[0043] In an embodiment of the present invention, the method for preparing the high-temperature resistant high-density drilling fluid includes the following steps:

[0044] (1) Preparation of base slurry: The clay material is added to water to prepare the base slurry, which is generally cured at 25℃±3℃. Sodium carbonate or potassium carbonate may also be added to disperse the moisture in the clay material. The amount of sodium carbonate or potassium carbonate can be 1 to 10% (wt) of the amount of clay material, preferably 3 to 6% (wt). Specifically, it may include: adding water to a container, adding sodium carbonate or potassium carbonate while stirring, and slowly adding the clay material while stirring, stirring at high speed for 15-20 minutes, sealing, and preferably curing at room temperature for 20-24 hours.

[0045] (2) Drilling fluid preparation: The multifunctional treatment agent and humic acid-based auxiliary materials are added to the cured base slurry under stirring. Under high-speed stirring, components including a pH adjuster (and salt if present) are added. After addition, the mixture is stirred at high speed. A weighting agent is then added, and the mixture is stirred at high speed again to obtain a simplified, high-density, high-temperature resistant drilling fluid system. The high-density drilling fluid prepared by this method has good temperature resistance and high-temperature stability, meeting the needs of drilling in high-temperature and high-pressure formations.

[0046] Further, the preparation method may specifically include: adding a non-functional long-lasting treatment agent sequentially to the cured base slurry under stirring, stirring at high speed for 10-30 minutes, then adding components including humic acid auxiliary materials, pH adjusters, and salts under stirring, stirring at high speed for 10-30 minutes after addition, adding a weighting agent, and stirring at high speed for about 10-20 minutes to obtain a simplified high-density, high-temperature resistant drilling fluid. Here, "high-speed stirring" is a shorthand for high-velocity stirring, specifically a stirring speed of 8000-11000 r / min.

[0047] This invention provides a high-temperature, high-density drilling fluid (which may be referred to as a high-temperature resistant high-density drilling fluid system, etc.) applicable to drilling operations under high-temperature and high-pressure environments. It incorporates a non-discriminatory, long-lasting treatment agent to achieve high temperature (greater than 220°C) and high density (e.g., 2.2 g / cm³). 3 The drilling fluid composition is controlled to two types, with the total usage controlled to 10%, while simultaneously meeting the requirements for rheological control, API filtration loss and HTHP filtration loss control, and high-temperature stability control. This significantly reduces the composition and usage of high-temperature and high-density components, saving on the overall cost of drilling fluid. It also significantly improves the long-term high stability of high-temperature and high-density drilling fluid, which can solve the problems commonly found in drilling fluids under deep, high-temperature and high-pressure formations, such as poor rheological properties, difficulty in control and maintenance, large water loss under high temperature and pressure, and barite sedimentation, thus avoiding complex downhole occurrences.

[0048] The present invention will be further illustrated below with reference to the embodiments. However, the present invention is not limited to the embodiments described below. The evaluation method for the high-temperature resistant, high-density drilling fluid performance refers to the People's Republic of China industry standard ZB / TE13004-90 (Drilling Fluid Testing Procedures).

[0049] Source of experimental materials

[0050] Sodium bentonite: Bentonite for drilling fluid test preparation at Bohai Drilling Mud Technology Service Branch, in accordance with standard SY / T5490-2016;

[0051] Non-differentiated long-lasting treatment agent: self-made by the Drilling Engineering Technology Research Institute of Sinopec Zhongyuan Petroleum Engineering Company;

[0052] Humic acid auxiliary materials (sulfonated lignite): Drilling Engineering Technology Research Institute of Sinopec Zhongyuan Petroleum Engineering Company. Appearance: dark brown powder, water-soluble matter ≤10%, humic acid content ≥50%, no dry basis total chromium, sulfonation degree ≥10.0%.

[0053] Barium sulfate (barite, specific gravity 4.0-4.6): Jiaxinyuan Petroleum Technology Service Co., Ltd.

[0054] Sodium hydroxide: Inner Mongolia Junzheng Energy & Chemical Group Co., Ltd.;

[0055] Potassium chloride: Qingdao Chengxin Hongfeng Chemical Co., Ltd.;

[0056] Sodium chloride: Shanghai Jiechang Industry & Trade Co., Ltd.;

[0057] Sodium carbonate: Henan Forest Environmental Protection Technology Co., Ltd.;

[0058] All other raw materials are commercially available.

[0059] The reaction structure of the non-functional long-acting treatment agent is as follows:

[0060]

[0061] The above synthesis steps are as follows: Esterified aconitic acid monomer, itaconic acid monomer, acrylic acid monomer, and 2-acrylamido-2-methylpropanesulfonic acid monomer are dissolved in an appropriate amount of water at a mass ratio of 70:1:20:8. The pH value is adjusted to 7-8 by using 40% potassium hydroxide solution. An appropriate amount of initiator is slowly added while stirring continuously. The initiation temperature is 30-50℃ and the reaction time is 2 hours to obtain the target product with an apparent viscosity of 40-45 mPa·s in a 1% mass concentration aqueous solution.

[0062] Example 1

[0063] Add 0.42g of sodium carbonate to 400g of water. After complete dissolution, add 12g of sodium bentonite. Stir at high speed for 20min, then seal and let stand at room temperature for 24h. Add 12g of non-functional long-lasting treatment agent, 12g of humic acid auxiliary material, and 2g of sodium hydroxide sequentially under high stirring. Stir for 20min, then add 1000g of barite. Stir at high speed for 20min, and measure rheological properties and medium-pressure filtration loss. Roll at 220℃ for 16h, cool to room temperature, and stir at high speed for 5min (stirring speed 8000~11000r / min). Measure rheological properties, medium-pressure water loss, and high-temperature high-pressure water loss at 180℃.

[0064] Drilling fluid properties before aging: plastic viscosity 102.0 mPa·s, dynamic shear stress 33.0 Pa, medium pressure fluid loss 0.6 mL. Drilling fluid pH value 9.5–10, density 2.2 g / cm³. 3 .

[0065] After being rolled at 220℃ for 16 hours, the drilling fluid properties are as follows: plastic viscosity 82.0 mPa·s, dynamic shear force 46.0 Pa, medium pressure water loss 0.5 mL; filtration loss at 180℃ high temperature and high pressure (HTHP) 11.0 mL.

[0066] Example 2

[0067] Add 0.42g of sodium carbonate to 400g of water. After complete dissolution, add 12g of sodium bentonite. Stir at high speed for 20 minutes, then seal and let stand at room temperature for 24 hours. Add 8g of non-functional long-lasting treatment agent, 12g of humic acid auxiliary material, and 2g of sodium hydroxide sequentially while stirring at high speed. Stir for 20 minutes, then add 28.0g of potassium chloride and 1000g of barite. Stir at high speed for 20 minutes. Measure rheological properties and medium-pressure filtration loss. Roll at 220℃ for 16 hours, cool to room temperature, stir at high speed for 5 minutes, and measure rheological properties, medium-pressure water loss, and high-temperature and high-pressure water loss at 180℃.

[0068] Drilling fluid properties before aging: plastic viscosity 57.0 mPa·s, dynamic shear force 45.0 Pa, medium pressure water loss 1.0 mL.

[0069] After being rolled at 220℃ for 16 hours, the drilling fluid properties are as follows: plastic viscosity 40.0 mPa·s, dynamic shear force 45.0 Pa, medium pressure water loss 0.8 mL; high temperature and high pressure filtration loss at 180℃ 15.0 mL.

[0070] Example 3

[0071] Add 0.42g of sodium carbonate to 400g of water. After complete dissolution, add 12g of sodium bentonite. Stir at high speed for 20 minutes, then seal and let stand at room temperature for 24 hours. Add 8g of non-functional long-lasting treatment agent, 16g of humic acid auxiliary material, and 2g of sodium hydroxide sequentially while stirring at high speed. Adjust and stir for 20 minutes. Add 60g of sodium chloride and 800g of barite. Stir at high speed for 20 minutes. Measure rheological properties and medium-pressure filtration loss. Roll at 220℃ for 16 hours. Cool to room temperature and stir at high speed for 5 minutes. Measure rheological properties, medium-pressure water loss, and high-temperature and high-pressure water loss at 180℃.

[0072] Drilling fluid properties before aging: plastic viscosity 53.0 mPa·s, dynamic shear force 38.5 Pa, medium pressure water loss 0.6 mL.

[0073] After being rolled at 220℃ for 16 hours, the drilling fluid properties are as follows: plastic viscosity 40.0 mPa·s, dynamic shear force 45.0 Pa, medium pressure water loss 0.6 mL, and high temperature and high pressure filtration loss at 180℃ 18.0 mL.

[0074] Example 4

[0075] Add 0.42g of sodium carbonate to 400g of water. After complete dissolution, add 12g of sodium bentonite. Stir at high speed for 20 minutes, then seal and let stand at room temperature for 24 hours. Under high stirring, add 12g of non-functional long-lasting treatment agent, 8g of humic acid auxiliary material, and 2g of sodium hydroxide in sequence. Adjust and stir for 20 minutes. Add 1400g of barite. Stir at high speed for 20 minutes. Measure rheological properties and medium-pressure filtration loss. Roll at 220℃ for 16 hours. Cool to room temperature and stir at high speed for 5 minutes. Measure rheological properties, medium-pressure water loss, and high-temperature and high-pressure water loss at 180℃.

[0076] Drilling fluid properties before aging: plastic viscosity 98.0 mPa·s, dynamic shear force 41.0 Pa, medium pressure water loss 1.0 mL.

[0077] After being rolled at 220℃ for 16 hours, the drilling fluid properties are as follows: plastic viscosity 35.0 mPa·s, dynamic shear force 48.2 Pa, medium pressure water loss 2.0 mL, and high temperature and high pressure filtration loss at 180℃ 20.0.

[0078] In this field, existing high-density drilling fluids with high temperature resistance generally contain no fewer than 10 components, including viscosity improvers and shear enhancers to control drilling fluid rheology; medium and high molecular weight polymer filtration reducers to control API filtration loss; sulfonated phenolic resin and sulfonated lignite to control filtration loss under high temperature and pressure; asphalt-based plugging materials with different softening points, ultrafine calcium carbonate, and other plugging materials. In particular, the dosage of sulfonated phenolic resin and sulfonated lignite in drilling fluids with temperatures above 200°C is generally higher than 12% (with on-site additions reaching over 15%). Moreover, the high-temperature stability of the drilling fluid is insufficient, and there is sedimentation at the bottom. High-temperature, high-density brine drilling fluids often exhibit a "sinking and dying" phenomenon. It is difficult to balance rheology and high-temperature, high-pressure filtration loss. The filtration loss at 180°C is greater than 50 mL, or even completely lost, which seriously affects drilling operations. Based on the test results of the above embodiments of the present invention, after being rolled at a high temperature of 220°C, the high-density drilling fluid of the present invention, which is resistant to high temperature, still has good rheological properties and does not show sedimentation. Moreover, the high-temperature and high-pressure water loss measured at 180°C is small.

[0079] As can be seen from the above embodiments, the high-density drilling fluid system formulation for high temperature resistance of the present invention relies heavily on the multiple functions of a specific, non-discriminatory, long-lasting treatment agent, combined with humic acid-based auxiliary materials, pH adjusters, and clay-based substances, achieving a density of up to 2.2 g / cm³. 3 It has a temperature resistance of over 220℃. The high-density drilling fluid of this invention has a simple composition and preparation method (no more than 4 types of treatment agents, and the amount of treatment agents is reduced by 30%). The rheological properties and high-temperature and high-pressure filtration loss of the drilling fluid are easy to control. The long-term high-temperature suspension stability is significantly improved compared with traditional high-temperature and high-density drilling fluids. It can be applied to drilling operations in high-temperature and high-pressure formations, significantly reducing the composition and amount of treatment agents, improving the long-term high-temperature stability of high-temperature and high-density drilling fluids, and facilitating drilling operations.

[0080] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the spirit of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make other modifications or additions to the described embodiments and use similar methods to substitute them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A high-density drilling fluid resistant to high temperatures, characterized in that, The high-density drilling fluid comprises the following components in parts by weight, based on water as 100 parts: 100 parts water; 0.5-4 parts of clay-based materials; 1-6 parts of non-distinguishing long-lasting treatment agent; 1-6 parts of humic acid-based auxiliary materials; 1-4 parts pH adjuster; 0-15 parts salt; 200-250 parts of weighting agent; The non-distinguishing long-lasting treatment agent is prepared by polymerization reaction of esterified aconitic acid monomer, itaconic acid monomer, acrylic acid monomer, and 2-acrylamido-2-methylpropanesulfonic acid monomer in a mass ratio of (70-80):(1-3):(10-20):(7-9).

2. The high-density drilling fluid resistant to high temperatures according to claim 1, characterized in that, The preparation steps of the non-distinguishing long-lasting treatment agent include: dissolving esterified aconitic acid monomer, itaconic acid monomer, acrylic acid monomer, and 2-acrylamido-2-methylpropanesulfonic acid monomer in water according to the mass ratio, adjusting the pH value to 7-8, carrying out the polymerization reaction in the presence of an initiator, the reaction temperature to 20-60℃, and the reaction time to 0.5-2h.

3. The high-density drilling fluid resistant to high temperatures according to claim 1, characterized in that, The clay-like material is at least one of bentonite, attapulgite, and sepiolite.

4. The high-density drilling fluid resistant to high temperatures according to claim 1, characterized in that, The pH adjuster is one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, and sodium carbonate.

5. The high-density drilling fluid resistant to high temperatures according to claim 1, characterized in that, The salt is an optional component, and is at least one of sodium chloride and potassium chloride.

6. The high-density drilling fluid resistant to high temperatures according to claim 1, characterized in that, The weighting agent is one or more of calcium carbonate, barite, and iron ore powder.

7. The high-density drilling fluid resistant to high temperatures according to any one of claims 1-6, characterized in that, The density of the high-density drilling fluid is 2.0–2.2 g / cm³. 3 The pH value is 9-11.

8. The method for preparing high-density drilling fluid resistant to high temperatures as described in any one of claims 1-7, characterized in that, Includes the following steps: Mix clay-based materials with water to make a base slurry, and cure for at least 15 hours; The base slurry obtained from the curing process is mixed with a non-discriminatory long-lasting treatment agent, humic acid auxiliary materials, pH adjuster and optional soil salt to obtain a mixed slurry. The mixture is mixed with a weighting agent and stirred to obtain the high-density drilling fluid resistant to high temperatures.

Images