Low solid phase high temperature resistant formate drilling and completion fluid and preparation method thereof

Abstract

The present invention belongs to the field of oil drilling exploration and development, and relates to a high-temperature resistant low-solid composite formate drilling and completion fluid and a preparation method thereof. The low-solid-phase high-temperature resistant formate drilling and completion fluid of the present invention comprises water, a high-temperature resistant shearing agent, a high-temperature resistant filtrate reducer, a buffer, a high-temperature resistant acid-soluble plugging agent and a weighting agent. The low-solid-phase high-temperature resistant drilling and completion fluid of the present invention has the characteristics of high density, low solid phase, high temperature resistance and a wide range of applications, and can be widely used in high-temperature and high-pressure deep well exploration and development where the production layer is blocked due to leakage.

Description

Technical Field

[0001] The invention belongs to the field of oil drilling exploration and development, and relates to a high-temperature resistant low-solid composite formate drilling and completion fluid and a preparation method thereof, and in particular to a low-solid-phase high-temperature resistant formate drilling and completion fluid suitable for the first area of ​​Shunbei, Xinjiang, and a preparation method thereof. Background Art

[0002] The Shuntuoguole area in Xinjiang has become an important oil and gas production successor block for Sinopec. The exploration resources of Shunbei Oilfield have reached 1.7 billion tons. However, the oil and gas reservoirs in this area are buried deep, generally more than 6500m deep, and the bottom hole temperature is as high as 170℃. Many wells that have been drilled have shown that the leakage rate of Shunbei District 1 is greater than 90%, with an average single well leakage of 1002 cubic meters. A large amount of solid phase weighting agents in the drilling fluid entering the reservoir can easily cause reservoir blockage. The pressure recovery of Shunbei 5 well at the beginning of production showed obvious blockage. After acidification, the production pressure difference dropped from 19 to 1.84MPa, and the output increased from 42m 3 / d increased to 81m 3 Therefore, there is an urgent need for a high-temperature resistant and low-solid drilling and completion fluid technology suitable for the Ordovician reservoir section in this area.

[0003] The existing low-solids drilling and completion fluid technology is mainly aimed at shallow bottom and low-pressure formations, and the system density is basically lower than 1.25g / cm 3 , the system's temperature resistance is less than 150°C, which cannot meet the construction requirements of the Shunbei District 1 reservoir. CN201110295975.8 involves a strongly inhibited solid-free polyamine-formate drilling fluid system, which is weighted with a single sodium formate or potassium formate, and has a maximum density of 1.25g / cm 3 , the temperature resistance is only 80°C. The low solid phase system involved in CN103275680A has a temperature resistance of only 140°C, and the inclined depth of the horizontal well does not exceed 5,000 meters. Although the high-temperature resistant and high-density solid-free formate drilling fluid system involved in CN105131915A meets the use requirements of the area in terms of temperature resistance and density, it uses expensive cesium formate for weighting, and its on-site feasibility is relatively low. The existing related low-solid phase drilling and completion fluid technologies mainly have problems such as low system density and low temperature resistance, and some systems use a single sodium formate, potassium formate or cesium formate for liquid phase weighting, resulting in poor system weighting performance and high cost, which cannot meet the requirements of economical and efficient development of deep high-temperature formations in Shunbei District 1. Summary of the invention

[0004] The technical problems to be solved by the present invention are: solving the blockage and pollution problem of the solid phase in the conventional drilling fluid system in the ultra-deep horizontal well reservoir that is easy to leak, and improving the production of the oil and gas reservoir; solving the well wall instability problem in the high-temperature mudstone formation, and improving the drilling and completion efficiency.

[0005] In order to solve the above problems, the present invention provides an economically feasible low-solid phase high-temperature resistant drilling and completion fluid which adopts sodium formate and potassium formate composite for liquid phase weighting and a preparation method thereof.

[0006] Specifically, the low-solid phase high-temperature resistant formate drilling and completion fluid of the present invention comprises water, a high-temperature resistant shear lift agent, a high-temperature resistant fluid loss reducer, a buffer, a high-temperature resistant acid-soluble plugging agent and a weighting agent.

[0007] Preferably, based on 100 parts by weight of water, the anti-high temperature shearing agent is 0.5-3 parts, the anti-high temperature filtration reducer is 0.3-2 parts, the buffer is 1-3 parts, the anti-high temperature acid-soluble plugging agent is 2-5 parts, and the weighting agent is 22-134 parts.

[0008] Further preferably, based on 100 parts by weight of water, the anti-high temperature shearing agent is 1-2 parts, the anti-high temperature filtration reducer is 0.5-1.5 parts, the buffer is 1.5-2.5 parts, the anti-high temperature acid-soluble plugging agent is 3-4 parts, and the weighting agent is 54-134 parts.

[0009] Preferably, the anti-high temperature shearing agent includes at least one of a shearing agent for gas stagnation, xanthan gum and sodium hydroxyethyl cellulose.

[0010] Preferably, the high temperature resistant fluid loss reducer comprises at least one of lignite graft copolymer fluid loss reducer, hydroxyethyl cellulose, polyanionic cellulose, sulfonated phenolic resin, sulfonated lignite, and lignite resin.

[0011] Further preferably, the high temperature resistant fluid loss reducer further comprises a random copolymer, and the general structural formula is as follows:

[0012]

[0013] Where M is Na + or K + ; R is H or CH3; n = 0-2; when n = 0, R is H; a:b:c = (2-8): 1: (0.5-5.0), the relative molecular mass of the random copolymer is (500,000-700,000).

[0014] Preferably, the buffer comprises at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide and potassium hydroxide.

[0015] Preferably, the acid-soluble plugging agent includes at least one of ultrafine calcium carbonate, ilmenite powder, and manganese tetraoxide.

[0016] Preferably, the weighting agent includes at least one of sodium formate and potassium formate.

[0017] On the other hand, the preparation method of the low solid phase high temperature resistant formate drilling and completion fluid of the present invention comprises uniformly mixing the water, high temperature resistant shear lift agent, high temperature resistant fluid loss reducer, buffer, high temperature resistant acid soluble plugging agent and weighting agent.

[0018] The technical solution of the present invention has the following beneficial effects:

[0019] (1) The low solid phase high temperature resistant drilling and completion fluid of the present invention has a temperature resistance of 170°C and a density of 1.20-1.40 g / cm 3 , wherein the solid volume content is less than 3%;

[0020] (2) The low-solid phase high-temperature resistant drilling and completion fluid of the present invention has the characteristics of high density, low solid phase, high temperature resistance, and a wide range of applications. It can be widely used in high-temperature and high-pressure deep well exploration and development where the production layer is blocked due to leakage, effectively preventing the solid phase in the drilling and completion fluid from blocking and contaminating the reservoir, which is beneficial to increasing the oil and gas production of the reservoir;

[0021] (3) The extreme pressure lubrication coefficient of the low-solid phase high-temperature resistant drilling and completion fluid of the present invention is less than 0.08, the core permeability recovery value after contamination is greater than 90%, and the mudstone rolling recovery rate is greater than 90%, which meets the drilling construction requirements of the deep high-temperature horizontal reservoir section in Shunbei District 1, Xinjiang. DETAILED DESCRIPTION

[0022] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments. Except for the following contents, the process method of the present invention adopts conventional methods or devices in the art. Unless otherwise specified, the following terms have the meanings commonly understood by those skilled in the art.

[0023] The present invention is mainly used in high-temperature and high-pressure deep well exploration and development where the production layer is blocked due to leakage, to prevent the solid phase in the drilling and completion fluid from blocking and contaminating the reservoir, which is beneficial to increasing the oil and gas production of the reservoir. In particular, Xinjiang Shunbei Oilfield is currently an important oil and gas production successor block of Sinopec. The oilfield exploration resources have reached 1.7 billion tons. The oil and gas reservoirs in the area are buried deep, generally more than 6500m deep, and the bottom hole temperature is as high as 170°C. However, at present, the reservoir section of Shunbei District 1 has frequent leakage, with a leakage rate of >90%, and an average single well leakage of 1002 cubic meters. According to the specific gravity of 1.4g / cm 3 The solid content of the polysulfone well slurry is 10%, and the solid phase leaking into the reservoir is as high as 100 cubic meters. The pressure recovery of Shunbei 5 well at the beginning of production showed obvious blockage. After acidification, the production pressure difference dropped from 19 to 1.84 MPa, and the production increased from 42m 3 / d increased to 81m 3 / d. Therefore, how to reduce solid phase contamination during drilling in the reservoir section of this area is of great significance to increasing the oil and gas production in Shunbei area, and has broad application prospects.

[0024] Specifically, according to one aspect of the present invention, the present invention provides a low-solid phase high-temperature resistant formate drilling and completion fluid, including water, a high-temperature resistant shear lift agent, a high-temperature resistant filtrate reducer, a buffer, a high-temperature resistant acid-soluble plugging agent and a weighting agent.

[0025] In the low-solid phase high-temperature resistant formate drilling and completion fluid of the present invention, the high-temperature resistant shearing agent is used to improve the structural strength of the low-solid phase system, including at least one of a shearing agent for gas stagnation plugs, xanthan gum and sodium hydroxyethyl cellulose (HEC). The shearing agent for gas stagnation plugs is made by grafting a polymerized monomer onto the surface of an organically modified layered chain clay mineral. For a specific preparation method, see the content disclosed in application number 201810057876.8.

[0026] Based on 100 parts by weight of water, the amount of the high temperature resistant shearing agent is 0.5-3 parts. When the amount of the high temperature resistant shearing agent is less than 0.5 parts, the system dynamic shear force and dynamic plasticity ratio are low, and the rock carrying requirements are not met. When the amount of the high temperature resistant shearing agent is higher than 3 parts, the system fluidity is poor, and the risk of excitation pressure and suction is increased. When the amount of the high temperature resistant shearing agent is 1-2 parts, the high temperature resistant low solid phase composite formate drilling and completion fluid of the present invention has the best performance.

[0027] In the low-solid phase high-temperature resistant formate drilling and completion fluid of the present invention, the high-temperature resistant fluid loss reducer is used to reduce water loss in the low-solid phase system and prevent wellbore instability, and includes at least one of lignite graft copolymer fluid loss reducer, hydroxyethyl cellulose, polyanionic cellulose, sulfonated phenolic resin, sulfonated lignite, and lignite resin.

[0028] The lignite graft copolymer fluid loss reducer is obtained by reacting the following raw materials: lignite 10-70, aldehyde 0.5-20, sulfonate polymer 2-30, water 100 parts. The preparation method is: the components are mixed evenly, reacted at 180-220°C for 6-10 hours, dried and crushed. The lignite graft fluid loss reducer has good fluid loss reduction effect and low viscosity effect in ultra-high density drilling fluid containing high solid phase weighting material, can improve the rheology of drilling fluid, and has the characteristics of temperature resistance and salt resistance.

[0029] In some embodiments, the high temperature resistant fluid loss reducer is a random copolymer, and the general structural formula is as follows:

[0030]

[0031] Where M is Na + or K +; R is H or CH3; n = 0-2; when n = 0, R is H; a: b: c = (2-8): 1: (0.5-5.0), the relative molecular mass of the random copolymer is (500,000-700,000). The fluid loss reducer is obtained by copolymerization of acrylamide, acrylic acid, and alkyl sulfonate containing acryloxy. The fluid loss reducer is easily dispersed and dissolved in water, and is very convenient to use; when it is applied to drilling fluid, it is easy to form a low-permeability, thin and dense filter cake, has good fluid loss reduction characteristics, and can control the thickening of drilling fluid under high temperature conditions above 200°C, even up to 250°C, and high salt (saturated brine) conditions.

[0032] Based on 100 parts by weight of water, the content of the high temperature resistant fluid loss reducer is 0.3-2 parts. When the content of the high temperature resistant fluid loss reducer is lower than 0.3 parts, the system fluid loss is large and the filter cake is thick; when the content of the high temperature resistant fluid loss reducer is higher than 2 parts, the rheological property of the system deteriorates. A large number of experiments have shown that when the content of the high temperature resistant fluid loss reducer is 0.5-1.5 parts, the high temperature resistant low solid phase composite formate drilling and completion fluid of the present invention has the best performance.

[0033] In the low solid phase high temperature resistant formate drilling and completion fluid of the present invention, the buffer is used to adjust the pH value of the drilling and completion fluid, including at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide. Based on 100 parts by weight of water, the buffer is 1-3 parts, preferably 1.5-2.5 parts

[0034] In the low-solid phase high-temperature resistant formate drilling and completion fluid of the present invention, the high-temperature resistant acid-soluble plugging agent is used to enhance the plugging performance of the system and reduce the water loss of the system, including: at least one of ultrafine calcium carbonate, ilmenite powder, and manganese tetraoxide. Based on 100 parts by weight of water, the high-temperature resistant acid-soluble plugging agent is 2-5 parts. When the content of the high-temperature resistant acid-soluble plugging agent is less than 2 parts, the system filtration loss is large and the filter cake quality is poor; when the content of the high-temperature resistant acid-soluble plugging agent is greater than 5 parts, the solid phase content of the system increases, and the difficulty of rheological coordination increases. A large number of experiments have shown that when the content of the high-temperature resistant acid-soluble plugging agent is 3-4 parts, the high-temperature resistant low-solid phase composite formate drilling and completion fluid of the present invention has the best performance.

[0035] In the low-solid-phase high-temperature resistant formate drilling and completion fluid of the present invention, the weighting agent is used to increase the liquid phase density of the system and reduce the content of inert weighting materials, wherein the weighting agent includes at least one of sodium formate and potassium formate. Based on 100 parts by weight of water, the weighting agent is 0-134 parts, and the amount of the weighting agent added should be appropriately adjusted according to the density of the drilling and completion fluid.

[0036] In the low-solid-phase high-temperature resistant formate drilling and completion fluid of the present invention, the high-temperature resistant shearing agent and the high-temperature resistant fluid loss reducer are combined to increase viscosity and reduce fluid loss, while improving the structural viscosity and dynamic plastic ratio, and enhancing the rock carrying performance of the system; the high-temperature resistant acid-soluble plugging agent and the formate weighting agent are compounded with solid and liquid to further reduce the system fluid loss and cost. The components work together to achieve the low-solid-phase high-temperature resistant formate drilling and completion fluid of the present invention with a temperature resistance of 170°C and a density of 1.20-1.40g / cm 3 , the solid volume content is less than 3%, the extreme pressure lubrication coefficient is less than 0.08, the core permeability recovery rate after pollution is greater than 90%, and the mudstone rolling recovery rate is greater than 90%.

[0037] On the other hand, the present invention provides a method for preparing a low-solid phase high-temperature resistant formate drilling and completion fluid, comprising uniformly mixing the water, high-temperature resistant shear lift agent, high-temperature resistant filtrate reducer, buffer, high-temperature resistant acid-soluble plugging agent and weighting agent.

[0038] Preferably, the amount of water is added to a high-stirring cup for drilling fluid, which is then placed on a high-speed stirrer dedicated to drilling fluid, the speed is adjusted to 8000-10000 rpm, and while stirring, the high-temperature resistant shearing agent, high-temperature resistant filtrate reducer, buffer and high-temperature resistant acid-soluble plugging agent are added, and a weighting agent is added as needed, and stirred at high speed for 20-25 minutes to fully disperse and dissolve the components to obtain the high-temperature resistant low-solid drilling and completion fluid system.

[0039] Example

[0040] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are based on conventional methods and conditions. The names and sources of the raw materials used in the examples are specifically shown in Table 1:

[0041] Table 1 Raw materials used in Examples 1-6 and their sources

[0042]

[0043] Among them, the preparation methods of high temperature resistant fluid loss reducer I and gas stagnation plugging agent are as follows:

[0044] High temperature resistant fluid loss reducer I: Add water to a reaction bottle, and evenly dissolve 50g (0.70mol) of water-soluble monomer acrylamide, 10g (0.14mol) of acrylic acid, 70g (0.28mol) of potassium (2-acryloyloxy)butyl sulfonate, and 0.7g of molecular weight regulator tert-dodecyl mercaptan in water under stirring, adjust the pH value of the polymerization system to 9.5 with 40% potassium hydroxide aqueous solution, add an aqueous solution of initiator (1.0g potassium persulfate and 1.0g sodium sulfite dissolved in 5mL water, respectively) to initiate the reaction at 34°C, and the polymerization reaction is completed after 22min to obtain an elastic colloid, which is granulated, dried, and crushed to obtain a high temperature resistant fluid loss reducer with a relative molecular mass of 680,000 for standby use.

[0045] Shearing agent (SMRM) for gas stagnation plug: 20g of attapulgite and 0.3g of KH570 are added to 100mL of distilled water, and the stirring speed is 300 rpm. After stirring for 30 minutes, 2g of 2-acrylamide-2-methylpropanesulfonic acid is added under stirring, and the pH value is adjusted to 6-7 with sodium hydroxide, and then 0.02g of ammonium persulfate and 0.02g of sodium bisulfite are added. The heating temperature is 60°C, and the stirring speed is maintained for 4 hours. The obtained mixture is dried and crushed to obtain the high temperature resistant shearing agent SMRM for standby use.

[0046] Examples 1-6

[0047] According to the following component proportions, water is added to a high-stirring cup for drilling fluid, and then placed on a high-speed stirrer for drilling fluid, the speed is adjusted to 8000 rpm, and sodium formate, high-temperature resistant shearing agent, high-temperature resistant fluid loss reducer, sodium hydroxide and ultrafine calcium carbonate are added while stirring, and stirred at high speed for 20 minutes to fully disperse and dissolve the components to obtain a formate drilling and completion fluid system of the density. The system has low solid content, good rheological water loss performance, and high high-temperature resistant reservoir permeability recovery value, and can meet the requirements of reservoir drilling and completion integration.

[0048] Table 2 Drilling and completion fluid system composition

[0049]

[0050] Physical and chemical properties test

[0051] 1. Routine performance evaluation test of drilling fluid

[0052] The evaluation method of the performance of the drilling and completion fluid system is carried out in accordance with GB / T 16783.1-2014 (Field test of drilling fluids in the petroleum and natural gas industry Part 1: Water-based drilling fluids), and the extreme pressure lubrication coefficient is tested using a Fann 212 extreme pressure lubrication instrument.

[0053] Table 3 Evaluation of conventional drilling fluid performance

[0054]

[0055] 2. Mudstone rolling recovery rate evaluation test

[0056] Method: Weigh 50g of 10-20 mesh mudstone cuttings respectively, put them into a high-temperature aging tank containing 400mL of sample, seal them and roll them at 170℃ for 16 hours, cool them to room temperature, sieve them with a 40-mesh standard sieve, transfer the sieve residue to a watch glass, dry them at (105±3)℃ for 4 hours, take them out and place them in the air for 24 hours, then weigh them, and calculate the rolling recovery rate by the ratio of the mass of the dried sieve residue to the mass of the cuttings before rolling.

[0057] Results: The test was conducted using brown mudstone with strong dispersibility. After hot rolling at 170°C, the rolling recovery rate of the mudstone in the embodiment was greater than 86.55%, which was much higher than the commonly used polysulfone system, showing excellent inhibition performance and meeting the construction needs of high-temperature mudstone well sections.

[0058] Table 4 Evaluation of different fluid inhibition

[0059] Samples Quality before hot rolling Quality after hot rolling Rolling recovery rate Shimizu 50.34 5.68 11.28 Polysulfone drilling fluid (Shunbei 1-20) 50.12 32.24 64.32 Example 1 50.08 43.94 87.74 Example 2 51.12 45.68 89.36 Example 3 50.08 45.91 91.67 Example 4 50.33 43.56 86.55 Example 5 50.76 45.24 89.13 Example 6 51.32 46.33 90.28

[0060] 3. Anti-oil pollution ability evaluation test

[0061] The low solid phase system formed by the present invention was evaluated for contamination using crude oil from Shunbei 1-1H well. 4%, 8% and 12% crude oil were added to the system prepared in Example 3, respectively. After high stirring at 8000 rpm for 20 minutes, the system was rolled and aged at 170°C for 16 hours, and then the system was taken out and cooled to room temperature for performance testing. After the amount of crude oil was gradually increased from 4% to 12%, the viscosity and water loss of the system were basically not affected, showing a strong ability to resist oil pollution.

[0062] Table 5 Evaluation of Anti-Oil Pollution Capability

[0063]

[0064] Note: After hot rolling at 170℃ for 16h, rheological test was carried out using Fann35 six-speed viscometer at a test temperature of 50℃.

[0065] 4. Evaluation test of anti-polysulfone slurry pollution ability

[0066] Method: The anti-pollution ability of Examples 1-6 of the present invention was evaluated by using the polysulfone slurry from Shunbei 1-20H well. 4%, 8% and 12% slurry were added to the systems prepared in Examples 1-6, respectively. The slurry density was 1.27 g / cm 3 After high stirring at 8000 rpm for 20 minutes, the steel was rolled and aged at 170℃ for 16 hours, and then taken out and cooled to room temperature for performance testing.

[0067] Results: With the increase of well slurry pollution, the viscosity of the low solid phase system remained basically stable, and the water loss was controlled within 6 mL, showing good resistance to well slurry pollution.

[0068] Table 6 Evaluation of anti-polysulfone slurry pollution ability

[0069]

[0070] Note: After hot rolling at 170℃ for 16h, rheological test was carried out using Fann35 six-speed viscometer at a test temperature of 50℃.

[0071] 5. Evaluation of core permeability recovery value after contamination

[0072] Method and steps: ① vacuum the core, saturate it with simulated formation water, and age it for 40 hours before use; ② use a core permeability tester (Core Lab-UltraaPerm50) to positively measure the gas permeability K0 of the core; ③ use a drilling fluid pollution evaluation device to pollute the low solid phase system prepared in Example 1-6, with a confining pressure of 15 MPa, a pressure difference of 3 MPa, and a pollution time of 2 hours; ④ clean the contaminated surface with 15% hydrochloric acid, and then use a gas permeability meter to test its permeability K d , and calculate K d / K0.

[0073] Results: The permeability test of three types of permeability cores after contamination was carried out using the low solid phase system prepared in Examples 1-6, showing that the permeability recovery value was greater than 91%, indicating that it has a good storage and conservation effect.

[0074] Table 7 Evaluation of core permeability recovery value after contamination

[0075]

[0076] The present invention has been disclosed above with preferred embodiments, but those skilled in the art should understand that these embodiments are only used to describe the present invention and should not be understood as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to these embodiments should be included in the scope of the claims of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined in the claims.

Claims

1. A low solid phase high temperature resistant formate drilling and completion fluid, characterized in that: Including water, high temperature resistant shearing agent, high temperature resistant fluid loss reducer, buffer, high temperature resistant acid soluble plugging agent and weighting agent; Wherein, based on 100 parts by weight of water, the anti-high temperature shearing agent is 1-2 parts, the anti-high temperature fluid loss reducer is 0.5-1.5 parts, the buffer is 1.5-2.5 parts, the anti-high temperature acid-soluble plugging agent is 3-4 parts, and the weighting agent is 54-134 parts; The anti-high temperature shearing agent is a shearing agent for gas stagnation; The buffer comprises at least one of sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate; The acid-soluble plugging agent includes at least one of ilmenite powder and manganese tetraoxide; The weighting agents are sodium formate and potassium formate; The low solid phase high temperature resistant formate drilling and completion fluid has a temperature resistance of 170°C and a density of 1.20-1.40 g / cm 3 , the solid volume content is less than 3%, the extreme pressure lubrication coefficient is less than 0.08, the core permeability recovery rate after contamination is greater than 90%, and the mudstone rolling recovery rate is greater than 90%; The preparation method of the shearing agent for gas stagnation plug is as follows: 20 g of attapulgite and 0.3 g of KH570 are added to 100 mL of distilled water, and the stirring speed is 300 rpm. After stirring for 30 minutes, 2 g of 2-acrylamide-2-methylpropanesulfonic acid is added under stirring, and the pH value is adjusted to 6-7 with sodium hydroxide, and then 0.02 g of ammonium persulfate and 0.02 g of sodium bisulfite are added, the heating temperature is 60° C., the stirring speed is maintained for reaction for 4 hours, and the obtained mixture is dried and crushed to obtain the high temperature resistant shearing agent; The high temperature resistant fluid loss reducer is a random copolymer, and the general structural formula is as follows: Where M is Na + or K + ; R is H or CH3; n=0-2; when n=0, R is H; a:b:c=(2-8):1:(0.5-5.0), the relative molecular mass of the random copolymer is (500,000-700,000).

2. The method for preparing the low solid phase high temperature resistant formate drilling and completion fluid according to claim 1, characterized in that: The method comprises uniformly mixing the water, the high temperature resistant shearing agent, the high temperature resistant filtration loss reducing agent, the buffer, the high temperature resistant acid soluble plugging agent and the weighting agent.

Images