High-temperature resistant and pollution resistant organic salt completion fluid and preparation method thereof

Abstract

The application provides an anti-high-temperature and anti-pollution organic salt well completion fluid and a preparation method thereof, and raw materials of the well completion fluid include, in terms of weight parts, 100 parts of water, 25-30 parts of potassium formate, 100-130 parts of potassium pyrophosphate, 0.3-0.7 parts of a high-temperature tackifying and filtrate-reducing agent, 1-3 parts of a high-temperature filtrate-reducing agent, 2-5 parts of a manganese powder plugging agent, 0.5-1.5 parts of triphosphite, 0.1-0.3 parts of tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester, 1-2 parts of polyethylene oxide-polypropylene oxide copolymer, 1-3 parts of nano silicon dioxide, 0.5-1.5 parts of sodium carboxymethyl cellulose and 0.3-0.8 parts of polyacrylamide. The anti-high-temperature and anti-pollution organic salt well completion fluid system has good plugging property, can reduce formation filtration and effectively protects a reservoir.

Description

Technical Field

[0001] This invention relates to the field of oil and gas drilling technology, specifically to a high-temperature resistant and pollution-resistant organic salt completion fluid and its preparation method. Background Technology

[0002] With the extraction of oil, conventional and shallow oil and gas reserves are becoming increasingly scarce. To meet the growing demand for oil, oil extraction is now increasingly focused on deep and ultra-deep wells, which is becoming more and more difficult. Exploration and development into deeper formations has become inevitable. As exploration and development continue to move into deeper formations, the formations encountered are becoming more and more complex, with higher bottom-hole temperatures and greater pressures. Selecting completion fluids with high-temperature treatment agents is becoming increasingly difficult. Under high-temperature conditions, the rheological properties, water loss and wall-building properties of completion fluids, as well as their poor resistance to calcium, CO2, and formation water intrusion, are becoming increasingly prominent. Maintenance of completion fluids often falls into a vicious cycle of "weighting - thickening - viscosity reduction - weighting agent sedimentation - density decrease - weighting again".

[0003] Currently used solid-free clean brine completion fluids do not contain bentonite or other solid phases. Their density is adjusted by adding different types and amounts of soluble inorganic salts. Commonly used inorganic salts include sodium chloride, calcium chloride, potassium chloride, sodium bromide, potassium bromide, calcium bromide, and zinc bromide, with densities ranging from 1.0 to 1.8 g / m³. 3 Adjustable within a certain range, it is suitable for fractured oil and gas reservoirs or highly water-sensitive oil and gas reservoirs where the casing extends down to the top of the reservoir and the reservoir is a single pressure layer. However, it has drawbacks such as high cost, complex process, easy leakage, severe corrosion, and the tendency of divalent calcium salts and zinc salts to scale and precipitate in the downhole formation, causing reservoir blockage and pollution. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a high-temperature resistant and pollution-resistant organic salt well completion fluid and its preparation method.

[0005] To achieve the above objectives, the present invention provides a high-temperature resistant and pollution-resistant organic salt completion fluid, the raw materials of which, by weight, include:

[0006] 100 parts water, 25-30 parts potassium formate, 100-130 parts potassium pyrophosphate, 0.3-0.7 parts high-temperature thickener and filtration loss reducer, 1-3 parts high-temperature filtration loss reducer, 2-5 parts manganese powder blocker, 0.5-1.5 parts triphosphite, 0.1-0.3 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], 1-2 parts polyethylene oxide-polypropylene oxide copolymer, 1-3 parts nano silica, 0.5-1.5 parts sodium carboxymethyl cellulose, and 0.3-0.8 parts polyacrylamide.

[0007] This invention primarily addresses the challenges posed by complex downhole geological conditions in high-temperature deep wells. During well completion, the completion fluid exhibits poor resistance to contamination from calcium, CO2, and formation water under high-temperature conditions, exhibiting poor rheological properties and water loss / wall-building properties. Furthermore, it addresses the severe corrosion of completion fluids without solid-phase clean brine and the tendency of divalent calcium and zinc salts to scale and precipitate in the formation, leading to reservoir blockage and contamination. This invention aims to achieve a completion fluid density of 1.7-2.0 g / m³ without using divalent salts. 3 Meanwhile, the completion fluid system of the present invention has the ability to resist high temperature of 180℃ and calcium and CO2 pollution, and exhibits good rheological properties and low water loss.

[0008] This invention, through the research and screening of indoor treatment agents, preferentially selects high-temperature resistant polymers as viscosity improvers and filtration loss reducers to increase the viscosity of the completion fluid system and reduce its filtration loss; it also incorporates monovalent alkali metal organic salts as weighting agents and inhibitors to formulate a solution with a density of 1.7-2.0 g / cm³. 3 This high-density completion fluid exhibits excellent water solubility and a wide operating temperature range. Its monovalent alkali metals do not produce chemical precipitation or fouling in the downhole formation, resulting in minimal reservoir contamination and damage. It will not clog the reservoir and has strong resistance to contamination from calcium, CO2, and oil, gas, and water intrusion. Furthermore, this completion fluid has minimal corrosiveness and will not cause corrosion or hardening to metal equipment or rubber components during use.

[0009] In this invention, the self-responsive material can automatically adjust its properties according to changes in the external environment. Under high temperature and high pressure conditions, it can effectively improve the temperature resistance and pollution resistance of the completion fluid.

[0010] Compared to other inorganic salts, potassium formate has better solubility and lower corrosivity, making it more suitable for drilling equipment; potassium pyrophosphate has good thermal stability and is not easily decomposed, maintaining the chemical stability of the completion fluid under high temperature and high pressure conditions; sodium sulfite has excellent antioxidant properties, delaying the oxidative degradation of various chemical components in the completion fluid. The inorganic salts in this invention exhibit good solubility at both high and low temperatures and do not exhibit low-temperature crystallization.

[0011] As a heat stabilizer, triterpenoids can reduce the oxidation reaction that occurs when completion fluid comes into contact with metal equipment at high temperatures, thereby protecting the metal equipment from corrosion and also helping to improve the stability of the completion fluid.

[0012] Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] can significantly improve the antioxidant properties of completion fluids as an antioxidant. Under high-temperature environments, it can effectively delay the oxidative degradation of various chemical components in the completion fluid, thereby extending its service life.

[0013] Polyethylene oxide-polypropylene oxide copolymers can improve the rheological properties of completion fluids, making them easier to pump and inject into formations, while also enhancing the salt resistance and contamination resistance of completion fluids.

[0014] Nano-silica can effectively seal tiny pores and cracks in the formation, preventing formation fluids from entering the wellbore.

[0015] Sodium carboxymethyl cellulose can significantly increase the viscosity of completion fluids, reduce their filtration loss in the formation, and improve the rheological properties of completion fluids.

[0016] Polyacrylamide can effectively absorb moisture in the formation and form a stable gel layer, thereby preventing the intrusion of formation fluids and improving the sand-carrying capacity of the completion fluid.

[0017] In the above-mentioned high-temperature resistant and pollution-resistant organic salt completion fluid, preferably, the raw materials of the completion fluid also include 0.5-2 parts of an autoresponsive material; the autoresponsive material is obtained by the polymerization reaction of N-isopropylacrylamide and acrylic acid under the action of an initiator.

[0018] In the above-mentioned high-temperature and pollution-resistant organic salt completion fluid, preferably, in the preparation of the self-responsive material, the weight ratio of N-isopropylacrylamide to acrylic acid is 1-2:1-2, more preferably 1-2:1.

[0019] In the above-mentioned high-temperature and pollution-resistant organic salt completion fluid, preferably, in the preparation of the self-responsive material, the initiator is azobisisobutyronitrile (AIBN); the amount of the initiator is 0.1-1% of the total weight of the monomers.

[0020] In the above-mentioned high-temperature and pollution-resistant organic salt completion fluid, preferably, in the preparation of the self-responsive material, the polymerization reaction temperature is 60-90℃ and the reaction time is 2-6h.

[0021] According to a specific embodiment of the present invention, preferably, the preparation method of the autoresponsive material is as follows: N-isopropylacrylamide (NIPAM) and acrylic acid (AAc) are dissolved in deionized water in proportion to form a homogeneous mixed solution; an initiator is added to the mixed solution, and the reaction temperature is heated and maintained for a certain time to allow the monomers to undergo a polymerization reaction; after the reaction is completed, the polymer is separated from the solution by steps such as precipitation, filtration, washing and drying to obtain the autoresponsive material.

[0022] In the above-mentioned high-temperature and pollution-resistant organic salt completion fluid, preferably, the high-temperature viscosity-enhancing and filtration-reducing agent is sulfonated phenolic resin and / or polyanionic cellulose; the high-temperature filtration-reducing agent is montmorillonite-reinforced polyurethane and / or cyclodextrin.

[0023] Preferably, the raw materials of the above-mentioned high-temperature resistant and pollution-resistant organic salt completion fluid also include 0.2-0.4 parts sodium sulfite and 0.4-1 parts NaOH.

[0024] In the above-mentioned high-temperature and pollution-resistant organic salt completion fluid, preferably, the manganese powder plugging agent is an ultrafine manganese powder plugging agent.

[0025] Preferably, in the above-mentioned high-temperature resistant and pollution-resistant organic salt completion fluid, the density of the organic salt completion fluid is 1.7-2.0 g / cm³. 3 .

[0026] This invention also provides a method for preparing the above-mentioned high-temperature resistant and pollution-resistant organic salt completion fluid, comprising:

[0027] Add high-temperature thickener and filtration loss reducer, potassium pyrophosphate, potassium formate, and sodium sulfite to water and mix well. Then add NaOH to adjust the pH of the solution to obtain an alkaline solution.

[0028] Add triphosphite, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], polyethylene oxide-polypropylene oxide copolymer, autoresponsive material and ultrafine manganese powder plugging agent to the alkaline solution, mix evenly to obtain the high-temperature resistant and pollution-resistant organic salt completion fluid.

[0029] In the above-mentioned method for preparing high-temperature resistant and pollution-resistant organic salt completion fluid, preferably, the pH value of the alkaline solution is 8.5-9; and the stirring speed during the mixing process is 600-6000 r / min.

[0030] According to a specific embodiment of the present invention, preferably, the preparation method of the above-mentioned high-temperature resistant and pollution-resistant organic salt completion fluid specifically includes the following steps:

[0031] According to the above weight proportions, pour clean water into a clean mixer. While stirring at 6000 rpm, slowly add the high-temperature thickener and filtration loss reducer to the beaker, stirring for 30 minutes until completely dissolved. Once completely dissolved, add the high-temperature filtration loss reducer to the mixing container while stirring at 1000 rpm. Then, slowly add potassium pyrophosphate to the water while stirring at 600 rpm, continuing to stir until completely dissolved. Subsequently, add potassium formate at the same stirring speed, stirring until completely dissolved. Add sodium sulfite and NaOH to adjust the pH to 8.5-9, ensuring the mixture has a suitable alkalinity. While maintaining a stirring speed of 1000 r / min, the following components are added to the mixing container: triphosphite, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and polyethylene oxide-polypropylene oxide copolymer, along with an appropriate amount of autoresponsive material. After all components are added, stirring continues at 1000 r / min. Finally, ultrafine manganese powder plugging agent is added, and stirring is again at 1000 r / min for 30 minutes to ensure that the plugging agent is fully dispersed and evenly distributed in the completion fluid. After the above steps, the high-temperature resistant and pollution-resistant organic salt completion fluid is prepared.

[0032] The technical solution provided by this invention has the following beneficial effects:

[0033] (1) The high-temperature and pollution-resistant organic salt completion fluid system of the present invention has good sealing properties, can reduce formation filtration loss, effectively protect the reservoir, and effectively solve the problem of insufficient completion fluid sealing capacity, causing reservoir water lock damage and reducing oil and gas production.

[0034] (2) The high-temperature resistant and pollution-resistant organic salt completion fluid of this invention creatively achieves a density of 1.7-2.0 g / cm³ using only monovalent salts without using divalent salts. 3 The preferred compound is a high-temperature viscosity-increasing and filtration-reducing agent, a high-temperature filtration-reducing agent, and high-density ultrafine manganese powder as a plugging agent, which further reduces the damage to the oil layer by the completion fluid of the present invention, while enabling the completion fluid to withstand high temperatures up to 180°C.

[0035] (3) The high-temperature and pollution-resistant organic salt completion fluid system of the present invention has slight corrosiveness and will not cause corrosion and hardening to metal equipment, downhole tubing and rubber devices during use.

[0036] (4) The high-temperature and pollution-resistant organic salt completion fluid system formulation of this invention includes triphosphite as a heat stabilizer and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] as an antioxidant. These components can effectively improve the stability of the completion fluid at high temperatures and prevent its performance from declining sharply due to temperature increases. The heat stabilizer can protect other components in the completion fluid from high-temperature decomposition or deterioration, while the antioxidant can resist the erosion of oxygen at high temperatures and extend the service life of the completion fluid. Detailed Implementation

[0037] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0038] In the embodiments of the present invention, the commercial model of the high-temperature thickening and filtration loss reducing agent is HFL-T, and the manufacturer is Hubei Hanko New Technology Co., Ltd.; the high-temperature filtration loss reducing agent is BPL-308, and the manufacturer is Tianjin Binpu Technology Development Co., Ltd.

[0039] Example 1

[0040] This embodiment provides a high-temperature resistant and pollution-resistant organic salt completion fluid, the preparation method of which is as follows:

[0041] The high-temperature and pollution-resistant organic salt completion fluid comprises the following components in parts by weight: 100 parts water, 25 parts potassium formate, 100 parts potassium pyrophosphate, 0.4 parts sodium sulfite, 0.3 parts high-temperature viscosity enhancer and filtration loss reducer, 2 parts high-temperature filtration loss reducer, 0.6 parts NaOH, 1.5 parts ultrafine manganese powder plugging agent, 0.5 parts triphosphite, 0.1 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], 1 part polyethylene oxide-polypropylene oxide copolymer, 1 part nano silica, 0.5 parts sodium carboxymethyl cellulose, 0.3 parts polyacrylamide, and 0.5 parts auto-responsive material;

[0042] The raw materials for the autoresponsive material include 50 parts of N-isopropylacrylamide, 30 parts of acrylic acid, 1 part of initiator (AIBN), and an appropriate amount of deionized water;

[0043] The preparation method of the autoresponsive material is as follows: weigh N-isopropylacrylamide, acrylic acid, and initiator according to the above ratio, dissolve N-isopropylacrylamide and acrylic acid in deionized water to form a homogeneous mixed solution, add initiator to the mixed solution, heat to 60°C and maintain for 2 hours to allow the monomers to polymerize. After the reaction is completed, separate the polymer from the solution through precipitation, filtration, washing and drying to obtain the autoresponsive material.

[0044] The preparation method of high-temperature resistant and pollution-resistant organic salt completion fluid is as follows:

[0045] Pour 100 parts of water into a clean mixing container. While stirring at 6000 rpm, slowly add 0.3 parts of a high-temperature thickener and filtration loss reducer to the beaker, stirring continuously for 30 minutes to ensure complete dissolution. Then, while stirring at 1000 rpm, add 2 parts of the high-temperature filtration loss reducer. Next, while stirring at 600 rpm, slowly add 100 parts of potassium pyrophosphate to the water, stirring continuously until completely dissolved. Then, while stirring at the same speed, add 25 parts of potassium formate, continuing to stir until completely dissolved. Finally, add 0.4 parts of sodium sulfite and 0.6 parts of NaOH to adjust the pH to 8.5-9. To ensure the mixture exhibits appropriate alkalinity, while maintaining a stirring speed of 1000 rpm, add the following components to the mixing container in the following proportions: triphosphite, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and polyethylene oxide-polypropylene oxide copolymer, along with an autoresponsive material. After all components are added, continue stirring at 1000 rpm. Finally, add 1.5 parts of ultrafine manganese powder plugging agent and stir again at 1000 rpm for 30 minutes to ensure the plugging agent is fully dispersed and evenly distributed in the completion fluid. After the above steps, the high-temperature resistant and pollution-resistant organic salt completion fluid system is prepared.

[0046] Example 2

[0047] This embodiment provides a high-temperature resistant and pollution-resistant organic salt completion fluid, the preparation method of which is as follows:

[0048] The high-temperature and pollution-resistant organic salt completion fluid comprises the following components in parts by weight: 100 parts water, 30 parts potassium formate, 130 parts potassium pyrophosphate, 0.4 parts sodium sulfite, 0.3 parts high-temperature viscosity enhancer and filtration loss reducer, 2 parts high-temperature filtration loss reducer, 1 part NaOH, 2 parts ultrafine manganese powder plugging agent, 1.5 parts triphosphite, 0.3 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], 2 parts polyethylene oxide-polypropylene oxide copolymer, 3 parts nano silica, 1.5 parts carboxymethyl cellulose, 0.8 parts polyacrylamide, and 2 parts auto-responsive material;

[0049] The raw materials for the autoresponsive material include 50 parts of N-isopropylacrylamide, 30 parts of acrylic acid, 2 parts of initiator (AIBN), and an appropriate amount of deionized water;

[0050] The preparation method of the autoresponsive material is as follows: weigh N-isopropylacrylamide, acrylic acid, and initiator according to the above ratio, dissolve N-isopropylacrylamide and acrylic acid in deionized water to form a homogeneous mixed solution; add initiator to the mixed solution, heat to 90°C, and maintain for 6 hours to allow the monomers to polymerize. After the reaction is completed, separate the polymer from the solution through precipitation, filtration, washing, and drying to obtain the autoresponsive material.

[0051] The preparation method of high-temperature resistant and pollution-resistant organic salt completion fluid is as follows:

[0052] Pour 100 parts of water into a clean mixing container. While stirring at 6000 rpm, slowly add 0.3 parts of a high-temperature thickener and filtration loss reducer to the beaker, stirring continuously for 30 minutes to ensure complete dissolution. Then, while stirring at 1000 rpm, add 2 parts of the high-temperature filtration loss reducer. Reduce the stirring speed to 600 rpm and slowly add 130 parts of potassium pyrophosphate to the water, stirring continuously until completely dissolved. Next, while stirring at the same speed, add 30 parts of potassium formate, continuing to stir until completely dissolved. Finally, adjust the pH to 8.5-9 with 0.4 parts of sodium sulfite and 1 part of NaOH. To ensure the mixture exhibits appropriate alkalinity, while maintaining a stirring speed of 1000 rpm, add the following components to the mixing container in the following proportions: triphosphite, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and polyethylene oxide-polypropylene oxide copolymer, along with an autoresponsive material. After all components are added, continue stirring at 1000 rpm. Finally, add 2 parts of ultrafine manganese powder plugging agent and stir again at 1000 rpm for 30 minutes to ensure the plugging agent is fully dispersed and evenly distributed in the completion fluid. After the above steps, the high-temperature resistant and pollution-resistant organic salt completion fluid system is prepared.

[0053] Example 3

[0054] This embodiment provides a high-temperature resistant and pollution-resistant organic salt completion fluid, the preparation method of which is as follows:

[0055] The high-temperature and pollution-resistant organic salt completion fluid comprises the following components in parts by weight: 100 parts water, 25 parts potassium formate, 150 parts potassium pyrophosphate, 0.4 parts sodium sulfite, 0.4 parts high-temperature viscosity enhancer and filtration loss reducer, 1.5 parts high-temperature filtration loss reducer, 0.8 parts NaOH, 5 parts ultrafine manganese powder plugging agent, 1 part triphosphite, 0.2 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1.4 parts polyethylene oxide-polypropylene oxide copolymer, 2.1 parts nano silica, 1.2 parts sodium carboxymethyl cellulose, 0.4 parts polyacrylamide, and 1.7 parts autoresponsive material;

[0056] The raw materials for the autoresponsive material include 50 parts of N-isopropylacrylamide, 30 parts of acrylic acid, 1 part of initiator (AIBN), and an appropriate amount of deionized water;

[0057] The preparation method of the autoresponsive material is as follows: weigh N-isopropylacrylamide, acrylic acid, and initiator according to the above ratio, dissolve N-isopropylacrylamide and acrylic acid in deionized water to form a homogeneous mixed solution; add initiator to the mixed solution, heat to 75°C and maintain for 4 hours to allow the monomers to polymerize; after the reaction is completed, separate the polymer from the solution through precipitation, filtration, washing and drying to obtain the autoresponsive material.

[0058] The preparation method of high-temperature resistant and pollution-resistant organic salt completion fluid is as follows:

[0059] Pour 100 parts of clean water into a clean mixing container. While stirring at 6000 rpm, slowly add 0.4 parts of the high-temperature thickener and filtration loss reducer to the beaker, stirring continuously for 30 minutes to ensure complete dissolution. Then, while stirring at 1000 rpm, add 1.5 parts of the high-temperature filtration loss reducer. Reduce the stirring speed to 600 rpm and slowly add 150 parts of potassium pyrophosphate to the water, stirring continuously until completely dissolved. Next, while stirring at the same speed, add 20 parts of potassium formate, continuing to stir until completely dissolved. Finally, adjust the pH to 8.5-9 with 0.4 parts of sodium sulfite and 1 part of NaOH. To ensure the mixture exhibits appropriate alkalinity, while maintaining a stirring speed of 1000 rpm, add the following components to the mixing container in the following proportions: triphosphite, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and polyethylene oxide-polypropylene oxide copolymer, along with an autoresponsive material. After all components are added, continue stirring at 1000 rpm. Finally, add 2 parts of ultrafine manganese powder plugging agent and stir again at 1000 rpm for 30 minutes to ensure the plugging agent is fully dispersed and evenly distributed in the completion fluid. After the above steps, the high-temperature resistant and pollution-resistant organic salt completion fluid system is prepared.

[0060] Comparative Example 1

[0061] Prepare 1.80g / cm 3 The brine completion fluid comprises: 100 parts clean water, 130 parts sodium pyrophosphate, 30 parts potassium acetate, 1 part high-temperature salt-resistant polymer, 0.5 parts zwitterionic surfactant, 0.6 parts sodium bisulfite, 5 parts nano-silica plugging agent, and an appropriate amount of sodium hydroxide. The pH value of this completion fluid is 8.5.

[0062] Application Test Case 1

[0063] The density of Examples 1-3 was tested respectively, and the rheological properties and API filtration loss after high-temperature hot rolling (temperature 180℃, time 16h) are detailed in Table 1 below.

[0064] Table 1. Results of Conventional Performance Tests of Completion Fluid System

[0065]

[0066] As shown in Table 1 above, the density of the completion fluid provided in Example 1 is 1.71 g / cm³, based on the evaluation test. 3 After hot rolling, the apparent viscosity was 37 mPa·s, the plastic viscosity was 30 mPa·s, the dynamic shear stress was 7 Pa, and the API filtration loss was 4.9 mL. The density of the completion fluid provided in Example 2 was 1.84 g / cm³. 3 After hot rolling, the apparent viscosity was 40 mPa·s, the plastic viscosity was 34 mPa·s, the dynamic shear stress was 6 Pa, and the API filtration loss was 3.7 mL. The density of the completion fluid provided in Example 3 was 2.01 g / cm³. 3 After hot rolling, the apparent viscosity is 45 mPa·s, the plastic viscosity is 37 mPa·s, the dynamic shear stress is 8 Pa, and the API filtration loss is 3.0 mL. The density of the high-temperature resistant and pollution-resistant organic salt completion fluid provided in this embodiment of the invention is 1.71-2.01 g / cm³. 3 After hot rolling, the apparent viscosity was 37-45 mPa·s, the plastic viscosity was 30-37 mPa·s, the dynamic shear stress was 6-8 Pa, and the AP filtration loss was 3.0-4.9 mL. The density and viscosity did not change significantly after hot rolling. Therefore, this completion fluid system has a temperature resistance of up to 180℃, which meets the construction requirements for high-temperature well completion operations. In contrast, the composite brine completion fluid in Comparative Example 1 showed significant performance changes before and after hot rolling, and could not meet the operational requirements for high-temperature wells at 180℃.

[0067] Application Test Example 2

[0068] The reservoir protection performance of the completion fluid systems provided in Examples 1-3 and Comparative Example 1 was determined. The specific evaluation method was as follows: Six core samples with similar physical properties were selected. The original forward permeability of the core samples was measured using kerosene. The six completion fluid systems were then used to dynamically contaminate the six core samples in reverse. The permeability of the contaminated core samples was then measured, and the permeability recovery value after dynamic damage was calculated. Specific parameters are detailed in Table 2 below.

[0069] Table 2. Dynamic Core Damage Evaluation for Different Completion Fluids

[0070]

[0071] As can be seen from the experimental data in the table above, the permeability recovery values ​​of the completion fluid systems provided in Examples 1-3 after dynamic damage to the core are all greater than 99%, which is significantly higher than that of the composite brine completion fluid in Comparative Example 1. It can be seen that the completion fluids provided in the embodiments of the present invention cause less damage to the reservoir, have a high reservoir permeability recovery value, and have a good reservoir protection effect.

[0072] Application Test Example 3

[0073] The corrosion degree of the completion fluids in Examples 1-3 and Comparative Example 1 on downhole tools was tested respectively. According to the method provided in "SY / T0026-1999 Water Corrosion Test Method", the mass and corrosion rate of steel samples immersed in the three completion fluids before and after corrosion were tested. When the corrosion rate is less than 0.075 mm / a, it can be identified as slight corrosion. The test temperature was 180℃, the immersion time of the steel samples was 72h, and the steel used was N80. The specific parameters are detailed in Table 3 below.

[0074] Table 3 Evaluation of Corrosion Degrees of Different Completion Fluids

[0075]

[0076]

[0077] At high temperatures, increased molecular activity intensifies the contact reaction between salt and metal, leading to a significantly higher corrosion inhibition rate in the completion fluid compared to low-temperature conditions. This results in the corrosion inhibition rate failing to meet the requirements of well completion operations. As shown in the experimental data in the table above, the completion fluid systems provided in Examples 1-3 exhibit corrosion rates of less than 0.075 mm / a on steel at 180℃, indicating only slight corrosion. These rates are significantly superior to the composite brine completion fluid in Comparative Example 1. All embodiments of this invention can meet the requirements of on-site well completion operations.

[0078] Application Test Example 4

[0079] Different concentrations of CaCl2 and CO2 were added to the completion fluid system provided in Example 3 above, and the system's anti-pollution test was conducted. The rheology of the completion fluid sample before and after pollution and the HTHP filtration loss at 180℃ were measured. The test conditions were measured after hot rolling at 180℃. Specific parameters are detailed in Table 4 below.

[0080] Table 4. Results of anti-fouling tests for different completion fluids

[0081]

[0082] The test results above show that the rheological properties and HTHP filtration loss of the completion fluid system provided in Example 3 did not change significantly after the addition of 1%, 3%, and 5% CaCl2 contamination. This demonstrates that the high-temperature and pollution-resistant organic salt completion fluid system of the present invention is resistant to CaCl2 contamination. 2+The system exhibits strong contamination resistance. In Example 3, the rheological properties and HTHP filtration loss of the completion fluid system after CO2 gas induction showed no significant changes, indicating that the high-temperature resistant and contamination-resistant organic salt completion fluid system of this invention is not easily contaminated by CO2 gas. After adding crude oil, the performance of the completion fluid provided in Example 3 remained essentially unchanged, demonstrating that the embodiments of this invention have a strong ability to resist crude oil contamination. In contrast, after adding crude oil to Comparative Example 1, its viscosity changed significantly, and the viscosity gradually increased with increasing crude oil content, indicating that Comparative Example 1 has a weaker ability to resist crude oil contamination.

[0083] Application Test Example 5

[0084] The solubility of Examples 1, 2, 3, and Comparative Example 1 at both room temperature and low temperature was tested. The test conditions were room temperature (25°C) and low temperature (-25°C) with stirring for 2-4 hours. The properties of the samples and whether salt precipitation occurred were observed. The specific test results are shown in Table 5.

[0085] Table 5 Solubility Tests at Room and Low Temperatures

[0086]

[0087] As can be seen from the above test results, the completion fluid of the present invention can still maintain good fluidity and solubility at a low temperature of -25℃, and no salt precipitation was observed. The completion fluid of the present invention can meet the requirements for low-temperature preparation in areas such as Daqing and Xinjiang, and will not produce precipitation caused by salt precipitation, thus affecting the density of the completion fluid entering the well.

Claims

1. A high-temperature resistant and pollution-resistant organic salt completion fluid, comprising, by weight, the following raw materials: 100 parts water, 25-30 parts potassium formate, 100-130 parts potassium pyrophosphate, 0.3-0.7 parts high-temperature thickener and filtration loss reducer, 1-3 parts high-temperature filtration loss reducer, 2-5 parts manganese powder blocker, 0.5-1.5 parts triphosphite, 0.1-0.3 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], 1-2 parts polyethylene oxide-polypropylene oxide copolymer, 1-3 parts nano silica, 0.5-1.5 parts sodium carboxymethyl cellulose, and 0.3-0.8 parts polyacrylamide.

2. The high-temperature resistant and pollution-resistant organic salt completion fluid according to claim 1, wherein, The raw materials for the completion fluid also include 0.5-2 parts of an autoresponsive material; the autoresponsive material is obtained by the polymerization reaction of N-isopropylacrylamide and acrylic acid under the action of an initiator.

3. The high-temperature resistant and pollution-resistant organic salt completion fluid according to claim 2, wherein, The weight ratio of N-isopropylacrylamide to acrylic acid is 1-2:1-2.

4. The high-temperature resistant and pollution-resistant organic salt completion fluid according to claim 2, wherein, The initiator is azobisisobutyronitrile; the amount of the initiator is 0.1-1% of the total weight of the monomers.

5. The high-temperature resistant and pollution-resistant organic salt completion fluid according to claim 2, wherein, The polymerization reaction temperature is 60-90℃, and the reaction time is 2-6 hours.

6. The high-temperature resistant and pollution-resistant organic salt completion fluid according to claim 1, wherein, The high-temperature thickening and filtration loss reducing agent is sulfonated phenolic resin and / or polyanionic cellulose; the high-temperature filtration loss reducing agent is montmorillonite-reinforced polyurethane and / or cyclodextrin.

7. The high-temperature resistant and pollution-resistant organic salt completion fluid according to claim 1, wherein, The raw materials for the completion fluid also include 0.2-0.4 parts sodium sulfite and 0.4-1 parts NaOH.

8. The high-temperature resistant and pollution-resistant organic salt completion fluid according to claim 1, wherein, The density of organic salt completion fluid is 1.7-2.0 g / cm³. 3 .

9. A method for preparing the high-temperature resistant and pollution-resistant organic salt completion fluid according to any one of claims 1-8, comprising: Add high-temperature thickener and filtration loss reducer, potassium pyrophosphate, potassium formate, and sodium sulfite to water and mix well. Then add NaOH to adjust the pH of the solution to obtain an alkaline solution. Add triphosphite, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], polyethylene oxide-polypropylene oxide copolymer, autoresponsive material and ultrafine manganese powder plugging agent to the alkaline solution, mix evenly to obtain the high-temperature resistant and pollution-resistant organic salt completion fluid.

10. The method for preparing the high-temperature resistant and pollution-resistant organic salt completion fluid according to claim 9, wherein, The pH value of the alkaline solution is 8.5-9; the stirring speed during the mixing process is 600-6000 r / min.

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