Density-adjustable high-temperature-resistant pure oil-based completion fluid and preparation method thereof

Abstract

The invention provides a density-adjustable high-temperature-resistant pure oil-based completion fluid and a preparation method thereof.The preparation method comprises the following steps that high-density chlorinated paraffin and n-hexadecane are selected and mixed to serve as a base oil phase, after mixing is conducted according to different proportions, a main emulsifier and an auxiliary emulsifier are added, and high-speed shearing dispersion is conducted; the defoaming agent, the high-temperature organic soil and the auxiliary additive are sequentially added, and all the components are uniformly mixed through high-speed shearing and stirring. By optimizing the synergistic effect of the base oil phase and the emulsifier component, the stability of the completion fluid in the high-temperature environment of 150 DEG C or above is remarkably improved, meanwhile, it is ensured that the density can be adjusted between 0.9 g / cm < 2 > and 1.2 g / cm < 2 >, and the well control requirements of deep wells and ultra-deep wells are met. The prepared pure oil-based completion fluid has the advantages of no free water phase, small damage to the reservoir, excellent chip carrying capacity and lubricating property, solves the problems of high-temperature sedimentation, out-of-control rheological property and the like of the traditional oil-based completion fluid, and provides reliable technical support for efficient development of high-temperature and high-pressure oil and gas reservoirs.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical technology, specifically relating to a high-temperature resistant, density-adjustable pure oil-based completion fluid and its preparation method. Background Technology

[0002] Deep and ultra-deep oil and gas reservoirs often exhibit dramatic changes in vertical pressure gradients. Different sections of the same well may require drilling fluids of varying densities to precisely balance formation pressure. Excessive density can easily fracturing the reservoir and leading to production losses, while insufficient density may trigger well kicks, blowouts, and other safety incidents. Traditional pure oil-based completion fluids, due to limitations in density adjustment, require frequent system replacements or significant additions or subtractions of weighting materials. This not only prolongs the operation cycle and increases costs but may also exacerbate reservoir contamination due to system fluctuations. In contrast, pure oil-based completion fluids with flexible density adjustment capabilities can achieve continuous and reversible density adjustments through simple formulation control. This allows them to adapt to the pressure requirements of formations at different depths, reduce the amount of solid weighting agents used (reducing the risk of sedimentation and contamination), and avoid disrupting the continuity of the oil phase and high-temperature stability due to density adjustments. This significantly improves the safety and economy of operations under complex well conditions.

[0003] Pure oil-based completion fluids are widely used in the development of deep wells, ultra-deep wells, and high-temperature, high-pressure oil and gas reservoirs due to their excellent lubricity, high-temperature resistance, and reservoir protection capabilities. However, traditional oil-based completion fluids are prone to problems such as base oil oxidation degradation and emulsifier thermal decomposition failure in high-temperature (>150℃) environments, leading to uncontrolled rheological properties, weighting agent sedimentation, and emulsion demulsification, which seriously affect wellbore stability and operational safety. In addition, traditional oil-based completion fluids rely on a single type of weighting agent (such as barite powder) to achieve high density, but high density easily leads to rheological deterioration (such as a sharp increase in plastic viscosity and insufficient dynamic shear force), and cannot adapt to changes in formation pressure gradients; low-density systems, due to the viscosity limitation of the base oil, find it difficult to maintain the suspension stability of the weighting agent.

[0004] In existing technologies, base oils are mostly selected from single conventional mineral oils or synthetic oils, but their high-temperature thermal stability is insufficient, and they are prone to viscosity abrupt changes under long-term high-temperature environments. Emulsifiers are mainly conventional fatty acid salts or polyethers, which are difficult to maintain interfacial film strength under high-temperature and high-salinity conditions, leading to decreased emulsion stability. Furthermore, research on the compatibility of base oils and emulsifiers is insufficient, and existing formulations often neglect the synergistic effect of the two on high-temperature rheology and dynamic sedimentation. Therefore, it is necessary to develop a density-adjustable pure oil-based completion fluid system based on the synergistic enhancement of low-viscosity, high-stability base oils and high-temperature resistant emulsifiers to meet the needs of efficient development of complex oil and gas reservoirs. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a high-temperature resistant, density-adjustable pure oil-based completion fluid. By optimizing the compatibility of the base oil and emulsifier and the preparation process, the density of the completion fluid can be adjusted between 0.9 and 1.23 g / cm³, and the stability and density performance of the completion fluid in high-temperature environments above 150°C are improved. At the same time, it takes into account low viscosity, low reservoir damage and excellent rheological properties, so as to meet the high-efficiency development needs of deep wells, ultra-deep wells and high-temperature and high-pressure oil and gas reservoirs.

[0006] In a first aspect, the present invention provides a high-temperature resistant, density-adjustable pure oil-based completion fluid, comprising a base oil, wherein the base oil is composed of chlorinated paraffin and n-hexadecane in a volume ratio of (10-a):a, wherein a=3-7, and wherein each 200ml of base oil contains the following raw materials: Emulsifier: 3.5-14g, which is an acid ester compound, a metal soap emulsifier, or a fatty acid emulsifier; Defoamer: 1-2g, is an organosilicone oil compound; Organic soil: 2-8g, which is heat-resistant organic soil; pH adjuster: 5-7g.

[0007] Among the raw materials mentioned above, the emulsifier can be selected according to the requirements. Such emulsifier is more resistant to high temperature and has good compatibility with base oil. The defoamer is a common silicone oil defoamer, which can be purchased from the market. The high-temperature resistant organic clay can also be purchased from the market. The high-temperature resistant organic clay is mainly made by inserting some high-temperature resistant groups into the organic clay and needs to have good compatibility with base oil.

[0008] One embodiment of the present invention involves the following method for preparing the organic soil: Benzyl dimethyl octadecyl ammonium chloride is added to deionized water at 55-65°C and stirred until dissolved or dispersed. Sodium bentonite is then added to the dispersion and stirred for 1 hour. The solid phase is collected, washed several times with a 30% ethanol aqueous solution, dried, and sieved to obtain the final product. The amount of benzyl dimethyl octadecyl ammonium chloride added is 50-55% of the amount of sodium bentonite added. The organic soil prepared in this manner exhibits better temperature resistance and better compatibility with the base oil in this invention, making it more suitable for underground reservoirs.

[0009] One embodiment of the present invention is that the emulsifier is one of the following: a mixture of EMUL and CO-EMUL, a mixture of Span80 and calcium stearate, or a mixture of Span80 and oleic acid, wherein the mass ratio of the mixture is 4:3. The preparation method of EMUL is as follows: 1 part styrene and 1 part maleic anhydride are polymerized in the presence of an initiator. After polymerization, 1.2 parts octadecylamine are added, and the mixture is stirred at 60-80℃ for 35-50 hours. The initiator used in this process can be a common oil-soluble initiator, such as azobisisobutyronitrile (AIBN), with a reaction temperature of 50-70℃. The amount added is 0.05-1% of the total mass of styrene and maleic anhydride. Higher initiator dosage and higher initiation temperature result in a shorter reaction time. This is a conventional polymerization process in the field, therefore its specific operation will not be elaborated upon.

[0010] The preparation method of CO-EMUL is as follows: tall oil and triethanolamine are mixed in a molar ratio of 1.5:1, and xylylmethane of 20% of the total mass of tall oil and triethanolamine is introduced into the esterifier clamp, and the reaction is continued at 165~175℃ for 7 hours to obtain the product.

[0011] In one embodiment of the present invention, the pH adjuster is calcium oxide.

[0012] In one embodiment of the present invention, the defoamer is dimethyl silicone oil.

[0013] On the other hand, another object of the present invention is to provide a method for preparing the above-mentioned density-adjustable high-temperature resistant pure oil-based completion fluid, comprising the following steps: (1) Base oil pretreatment: Chlorinated paraffin and n-hexadecane are mixed in a fixed ratio and added to a beaker, and stirred until completely dissolved; (2) Emulsifier compounding: Add emulsifier to the prepared base oil and shear at high speed of 10000~12000rpm for 5-10min; (3) Stability adjustment: Add defoamer and shear at high speed of 10000~12000rpm for 5-10min; (4) Density adjustment: Add auxiliary additives and organic soil, shear at high speed of 10000~12000rpm for 15-30min, and stir evenly to obtain high-density completion fluid.

[0014] The beneficial effects of this invention are as follows: This invention provides a pure oil-based completion fluid with adjustable density, which is synergistically enhanced by a low-viscosity, high-stability base oil and a high-temperature resistant emulsifier. It is suitable for high temperatures up to 150°C and its density can be adjusted according to the actual reservoir conditions. Furthermore, the completion fluid of this invention causes minimal damage to the reservoir and has excellent cuttings carrying capacity and lubrication performance. It solves the problems of high-temperature sedimentation and rheological runaway of traditional oil-based completion fluids, providing reliable technical support for the efficient development of high-temperature and high-pressure oil and gas reservoirs. Detailed Implementation

[0015] The specific embodiments of the present invention will be clearly and completely described below with reference to examples. Obviously, the described examples are only some embodiments of the present invention, and not all embodiments.

[0016] Unless otherwise specified, the experimental procedures used in the following examples are all conventional methods.

[0017] Unless otherwise specified, the pharmaceutical agents used in the following embodiments are all conventional commercial products in the art.

[0018] In the following examples, the chlorinated paraffin used is designated as 52#.

[0019] In the following examples, the organic soil was prepared as follows: 10.28 g of benzyl dimethyl octadecyl ammonium chloride was added to 400 mL of deionized water at 60 °C and stirred to dissolve or disperse it. Then, 20 g of sodium bentonite was added to the above dispersion and stirred for 1 h. The mixture was washed several times with a 30% ethanol aqueous solution, and then dried and sieved to obtain the final product.

[0020] In the following embodiments, the EMUL is prepared as follows: 1 mole of styrene and 1 mole of maleic anhydride are polymerized in the presence of azobisisobutyronitrile (AIBN) at a polymerization temperature of 65°C for 3 hours. The amount of initiator added is 0.3% of the total mass of styrene and maleic anhydride. After polymerization, 1.2 moles of octadecylamine are added, and the mixture is stirred at 60-80°C for 35-50 hours to obtain the final product.

[0021] In the following examples, the CO-EMUL is prepared as follows: tall oil and triethanolamine are mixed at a molar ratio of 1.5:1, and xylylmethane of 20% of the total mass of tall oil and triethanolamine is introduced into the esterifier clamp, and the mixture is reacted at 165°C for 7 hours to obtain the CO-EMUL.

[0022] Example 1: A high-density, high-temperature resistant pure oil-based completion fluid, with the following composition: 200ml of base oil composed of chlorinated paraffin and n-hexadecane in a volume ratio of 7:3, 4g of emulsifier EMUL, 3g of emulsifier CO-EMUL, 2g of defoamer dimethyl silicone oil, 4g of organo-earth, and 14g of calcium oxide.

[0023] The preparation method of this high-density, high-temperature resistant, pure oil-based completion fluid is as follows: S1: Add 140 mL of chlorinated paraffin to a beaker, heat to 40 °C, then add 60 mL of n-hexadecane and continue stirring until completely mixed; S2: Add 200mL of high-density oil, 4g of EMUL, and 3g of CO-EMUL to the shearing cup, and shear at high speed for 8 minutes at 10000~12000rpm. S3: After stopping stirring, observe whether a large number of bubbles are generated, add 2g of dimethyl silicone oil, and stir again for 6 minutes; S4: Add 4g of organic soil and 14g of calcium oxide to the stirred slurry, and shear it again at 10000~12000rpm for 20min. Stir evenly to obtain a high-density completion fluid.

[0024] Example 2: A high-density, high-temperature resistant pure oil-based completion fluid, composed of the following: 200ml of base oil consisting of chlorinated paraffin and n-hexadecane in a volume ratio of 7:3, 8g of emulsifier Span80, 6g of emulsifier oleic acid, 2g of defoamer dimethyl silicone oil, 8g of organo-earth, and 14g of calcium oxide.

[0025] The preparation method of this high-density, high-temperature resistant, pure oil-based completion fluid is as follows: S1: Add 140 mL of chlorinated paraffin to a beaker, heat to 40 °C, then add 60 mL of n-hexadecane and continue stirring until completely mixed; S2: Add 200mL of the prepared high-density oil, 8g of Span80, and 6g of oleic acid to the shearing cup, and shear at high speed for 8 minutes at 10000~12000rpm; S3: After stopping stirring, observe whether a large number of bubbles are generated, add 2g of dimethyl silicone oil, and stir again for 5 minutes; S4: Add 8g of organic soil and 14g of calcium oxide to the stirred slurry, and stir again at 10000~12000 rpm for 20 minutes until uniformly mixed to obtain high-density completion fluid.

[0026] Example 3: A medium-density, high-temperature resistant pure oil-based completion fluid, with the following composition: 200ml of base oil composed of chlorinated paraffin and n-hexadecane in a volume ratio of 6:4, 4g of emulsifier Span80, 3g of emulsifier calcium stearate, 2g of defoamer dimethyl silicone oil, 6g of organo-earth, and 14g of calcium oxide.

[0027] The preparation method of this medium-density, high-temperature resistant, pure oil-based completion fluid is as follows: S1: Add 120 mL of chlorinated paraffin to a beaker, heat to 40°C, then add 80 mL of n-hexadecane and stir continuously until completely mixed; S2: Add 200 mL of the prepared high-density oil, 4 g of Span80, and 3 g of calcium stearate to the shearing cup, and shear at high speed for 7 min at 10000~12000 rpm; S3: After stopping stirring, observe whether a large number of bubbles are generated, add 2 g of dimethyl silicone oil, and stir again for 6 min; S4: Add 6 g of organic soil and 14 g of calcium oxide to the stirred slurry, and stir again at 10000~12000 rpm for 25 min until uniformly mixed to obtain medium-density completion fluid.

[0028] Example 4: A low-density, high-temperature resistant pure oil-based completion fluid, with the following composition: 200ml of base oil composed of chlorinated paraffin and n-hexadecane in a volume ratio of 3:7, 4g of emulsifier Span80, 3g of emulsifier calcium stearate, 2g of defoamer dimethyl silicone oil, 8g of organo-earth, and 14g of calcium oxide.

[0029] The preparation method of this high-density, high-temperature resistant, pure oil-based completion fluid is as follows: S1: Add 60 mL of chlorinated paraffin to a beaker, heat to 40°C, then add 140 mL of n-hexadecane and stir continuously until completely mixed; S2: Add 200 mL of the prepared high-density oil, 4 g of Span80, and 3 g of calcium stearate to the shearing cup, and shear at high speed for 7 min at 10000~12000 rpm; S3: After stopping stirring, observe whether a large number of bubbles are generated, add 2 g of dimethyl silicone oil, and stir again for 5 minutes; S4: Add 8 g of organic soil and 14 g of calcium oxide to the stirred slurry, and stir again at 10000~12000 rpm for 25 min until uniformly mixed to obtain a low-density completion fluid.

[0030] Comparative Example 1: A high-density, high-temperature resistant pure oil-based completion fluid, composed of the following: 200 ml of base oil consisting of chlorinated paraffin and n-octane in a volume ratio of 7:3, 4 g of emulsifier EMUL, 3 g of emulsifier CO-EMUL, 2 g of defoamer dimethyl silicone oil, 4 g of organo-earth, and 14 g of calcium oxide.

[0031] S1: Add 140 mL of chlorinated paraffin to a beaker, heat to 40°C, then add 60 mL of n-octane and stir continuously until completely mixed; S2: Add 200 mL of the prepared high-density oil, 4 g EMUL, and 3 g CO-EMUL to the shearing cup, and shear at high speed of 10000 ~12000 rpm for 8 min; S3: After stopping stirring, observe whether a large number of bubbles are generated, add 2 g of dimethyl silicone oil, and stir again for 6 minutes; S4: Add 4 g of organic soil and 14 g of calcium oxide to the stirred slurry, and stir again at high speed of 10000 ~12000 rpm for 20 min until uniformly mixed to obtain high-density completion fluid.

[0032] Comparative Example 2, a high-density, high-temperature resistant pure oil-based completion fluid, has the following composition: 200 ml of base oil composed of chlorinated paraffin and n-dodecane in a volume ratio of 7:3, 4 g of emulsifier EMUL, 3 g of emulsifier CO-EMUL, 2 g of defoamer dimethyl silicone oil, 4 g of organo-earth, and 14 g of calcium oxide.

[0033] S1: Add 140 mL of chlorinated paraffin to a beaker, heat to 40°C, then add 60 mL of n-dodecane and stir continuously until completely mixed; S2: Add 200 mL of the prepared high-density oil, 4 g EMUL, and 3 g CO--EMUL to the shearing cup, and shear at high speed for 8 min at 10000 ~12000 rpm; S3: After stopping stirring, observe whether a large number of bubbles are generated, add 2 g of dimethyl silicone oil, and stir again for 5 minutes; S4: Add 4 g of organic soil and 14 g of calcium oxide to the stirred slurry, and stir again at 10000~12000 rpm for 20 minutes until uniformly mixed to obtain a high-density completion fluid.

[0034] Comparative Example 3: A high-density, high-temperature resistant pure oil-based completion fluid, with the following composition: 200 ml of base oil composed of chlorinated paraffin and n-octane in a volume ratio of 7:3, 8 g of emulsifier Span80, 6 g of emulsifier oleic acid, 2 g of defoamer dimethyl silicone oil, 8 g of organo-earth, and 14 g of calcium oxide.

[0035] S1: Add 140 mL of chlorinated paraffin to a beaker, heat to 40°C, then add 60 mL of n-octane and stir continuously until completely mixed; S2: Add 200 mL of the prepared high-density oil, 8 g of Span80, and 6 g of oleic acid to the shearing cup, and shear at high speed for 7 min at 10000 ~12000 rpm; S3: After stopping stirring, observe whether a large number of bubbles are generated, add 2 g of dimethyl silicone oil, and stir again for 6 minutes; S4: Add 8 g of organic soil and 14 g of calcium oxide to the stirred slurry, and stir again at 10000~12000 rpm for 20 minutes until uniformly mixed to obtain high-density completion fluid.

[0036] Comparative Example 4: A high-density, high-temperature resistant pure oil-based completion fluid, composed of the following: 200 ml of base oil consisting of chlorinated paraffin and n-dodecane in a volume ratio of 7:3, 8 g of emulsifier Span80, 6 g of emulsifier oleic acid, 2 g of defoamer dimethyl silicone oil, 8 g of organo-earth, and 14 g of calcium oxide.

[0037] S1: Add 140 mL of chlorinated paraffin to a beaker, heat to 40°C, then add 60 mL of n-dodecane and stir continuously until completely mixed; S2: Add 200 mL of the prepared high-density oil, 8 g of Span80, and 6 g of oleic acid to the shearing cup, and shear at high speed for 8 min at 10000 ~12000 rpm; S3: After stopping stirring, observe whether a large number of bubbles are generated, add 2 g of dimethyl silicone oil, and stir again for 5 min; S4: Add 8 g of organic soil and 14 g of calcium oxide to the stirred slurry, and stir again at 10000~12000 rpm for 20 minutes until uniformly mixed to obtain high-density completion fluid.

[0038] Comparative Example 5: A high-density, high-temperature resistant pure oil-based completion fluid, composed of the following: 200 ml of base oil consisting of chlorinated paraffin and cyclohexane in a volume ratio of 7:3, 8 g of emulsifier Span80, 6 g of emulsifier oleic acid, 2 g of defoamer dimethyl silicone oil, 8 g of organo-earth, and 14 g of calcium oxide.

[0039] S1: Add 140 mL of chlorinated paraffin to a beaker, heat to 40°C, then add 60 mL of cyclohexane and stir continuously until completely mixed; S2: Add 200 mL of the prepared high-density oil, 8 g of Span80, and 6 g of oleic acid to the shearing cup, and shear at high speed for 7 min at 10000 ~12000 rpm; S3: After stopping stirring, observe whether a large number of bubbles are generated, add 2 g of dimethyl silicone oil, and stir again for 6 minutes; S4: Add 8 g of organic soil and 14 g of calcium oxide to the stirred slurry, and stir again at 10000~12000 rpm for 20 minutes until uniformly mixed to obtain high-density completion fluid.

[0040] Comparative Example 6: A high-density, high-temperature resistant pure oil-based completion fluid, composed of the following: 200ml of base oil consisting of chlorinated paraffin and white oil in a volume ratio of 7:3, 8g of emulsifier Span80, 6g of emulsifier oleic acid, 2g of defoamer dimethyl silicone oil, 8g of organo-earth, and 14g of calcium oxide.

[0041] S1: Add 140 mL of chlorinated paraffin to a beaker, heat to 40°C, then add 60 mL of No. 3 white oil and stir continuously until completely mixed; S2: Add 200 mL of the prepared high-density oil, 8 g of Span80, and 6 g of oleic acid to the shearing cup, and shear at high speed for 7 min at 10000 ~12000 rpm; S3: After stopping stirring, observe whether a large number of bubbles are generated, add 2 g of dimethyl silicone oil, and stir again for 6 minutes; S4: Add 8 g of organic soil and 14 g of calcium oxide to the stirred slurry, and stir again at 10000~12000 rpm for 20 minutes until uniformly mixed to obtain high-density completion fluid.

[0042] To further illustrate the performance of the completion fluid prepared in the embodiments of the present invention, it is tested below.

[0043] The test methods were based on those in GB / T 16783.2-2012 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 2: Oil-based Drilling Fluids". The final test results are shown in Table 1.

[0044] Table 1 Performance parameters of completion fluid

[0045] Based on the above experiments, while the completion fluids prepared with dodecane in Comparative Examples 2 and 4 showed good performance, dodecane's low flash point makes it unsuitable as a raw material for preparing completion fluids. Comparative Example 1 exhibited poor stability due to a sharp drop in ES (expiratory value) at high densities. Comparative Examples 5 and 6 showed kinematic and plastic viscosities exceeding their ranges, indicating poor rheological properties. Hexadecane was chosen as the base oil for mixing with chlorinated paraffin because the resulting completion fluid maintains extremely high emulsification stability (ES=2048V) after high-temperature aging, and its density is adjustable. With appropriate formulation design, suitable dynamic shear strength and gel strength can be obtained, meeting the requirements of the completion fluid.

[0046] The present invention has been disclosed above with preferred embodiments. However, those skilled in the art should understand that these embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Further improvements can be made without departing from the principles of the invention, and these improvements should also be considered as protections of the present invention.

Claims

1. A density-adjustable, high-temperature resistant pure oil-based completion fluid, characterized in that, The base oil comprises chlorinated paraffin and n-hexadecane in a volume ratio of (10-a):a, where a = 3-7, and each 200 ml of the base oil contains the following raw materials: Emulsifier: 3.5-14g, which is an acid ester compound, a metal soap emulsifier, or a fatty acid emulsifier; Defoamer: 1-2g, is an organosilicone oil compound; Organic soil: 2-8g, which is heat-resistant organic soil; pH adjuster: 5-7g.

2. The density-adjustable, high-temperature resistant pure oil-based completion fluid according to claim 1, characterized in that, The method for preparing the organic soil is as follows: benzyl dimethyl octadecyl ammonium chloride is added to deionized water at 55-65°C and stirred to dissolve or disperse it. Then, sodium bentonite is added to the above dispersion and stirred for 1 hour. The solid phase is taken, washed several times with a 30% ethanol aqueous solution, and then dried and sieved to obtain the product. The amount of benzyl dimethyl octadecyl ammonium chloride added is 50-55% of the amount of sodium bentonite added.

3. The density-adjustable, high-temperature resistant pure oil-based completion fluid according to claim 1, characterized in that, The emulsifier is one of the following: a mixture of EMUL and CO-EMUL, a mixture of Span80 and calcium stearate, or a mixture of Span80 and oleic acid, with a compounding mass ratio of 4:

3. The preparation method of the EMUL is as follows: 1 part styrene and 1 part maleic anhydride are polymerized under the action of an initiator. After the polymerization is completed, 1.2 parts octadecylamine are added and stirred at 60-80℃ for 35-50h to obtain the EMUL. The preparation method of CO-EMUL is as follows: tall oil and triethanolamine are mixed in a molar ratio of 1.5:1, and xylylmethane of 20% of the total mass of tall oil and triethanolamine is introduced into the esterifier clamp, and the reaction is continued at 165~175℃ for 7 hours to obtain the product.

4. The density-adjustable, high-temperature resistant pure oil-based completion fluid according to claim 1, characterized in that, The pH adjuster is calcium oxide.

5. The density-adjustable, high-temperature resistant pure oil-based completion fluid according to claim 1, characterized in that, The defoamer is dimethyl silicone oil.

6. A method for preparing a density-adjustable, high-temperature resistant pure oil-based completion fluid according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Base oil pretreatment: Chlorinated paraffin and n-hexadecane are mixed in a fixed ratio and added to a beaker, and stirred until completely dissolved; (2) Emulsifier compounding: Add emulsifier to the prepared base oil and shear at high speed of 10000~12000rpm for 5-10min; (3) Stability adjustment: Add defoamer and shear at high speed of 10000~12000rpm for 5-10min; (4) Density adjustment: Add auxiliary additives and organic soil, shear at high speed of 10000~12000rpm for 15-30min, and stir evenly to obtain high-density completion fluid.

Images