A high-temperature resistant weak gel anti-gas invasion drilling fluid and its preparation method

Abstract

The present application provides a high-temperature resistant weak gel anti-gas intrusion drilling fluid and a preparation method thereof, which relates to the field of drilling engineering oilfield chemical technology. The high-temperature resistant weak gel anti-gas intrusion drilling fluid comprises the following components: water, formate, pH regulator, high-temperature stabilizer, viscosity enhancer, high-temperature resistant flow pattern regulator, high-temperature resistant filtration reducer, heat-resistant plugging agent, temporary plugging agent, lubricant, defoamer and barite. The high-temperature resistant weak gel anti-gas intrusion drilling fluid provided by the present application can overcome the problem that conventional weak gel drilling fluid has low viscosity at a low shear rate of 160°C, low viscosity shear force, and cannot suppress gas intrusion, thereby realizing the high-temperature resistant weak gel drilling fluid system to prevent and control gas intrusion, reduce drilling non-effective production time, improve drilling efficiency, and accelerate oil and gas exploration and development.

Description

Technical Field

[0001] The present application relates to the technical field of oilfield chemistry in drilling engineering, and in particular to a high-temperature resistant weak gel anti-gas intrusion drilling fluid and a preparation method thereof. Background Art

[0002] During drilling, gases such as CH4 and CO2, which have low density, strong diffusion, and easy displacement characteristics, can enter the wellbore and cause gas invasion. This can lead to rapid, frequent, and severe oil and gas surges, accompanied by leaks and inrush. Underbalanced gas invasion in some operating wells can be mitigated by increasing the drilling fluid density. However, some wells experience both gravity displacement and underbalanced gas invasion. Increasing the drilling fluid density can exacerbate gas invasion and cause leakage, which can easily lead to complex downhole accidents such as blowouts and overflows. On-site gas invasion prevention primarily relies on the proper control of drilling fluid density and pressure differential. Techniques such as precision managed pressure drilling, throttling and circulating exhaust, heavy slurry capping or gas stagnation plugging, and seam sealing are commonly used to control gas invasion and maximize safe operating time. However, reducing the density of drilling fluid can effectively solve the problem of underbalanced gas invasion, but it cannot suppress gravity displacement gas invasion; managed pressure drilling can effectively control the amount of gas invasion, but it requires the establishment of an accurate pressure prediction model; the exhaust time of throttling circulation exhaust is long, which affects the drilling time, and it cannot avoid the impact of gases such as CO2 on mud properties; the use of heavy slurry caps or gas plugs has problems such as difficulty in quickly replacing the gas plug gel and the heavy slurry cap easily leaking out of the formation, causing reservoir pollution; reservoir sealing and gas blocking is suitable for blocking gas in micro-fracture reservoirs, but it has high requirements on material strength and temperature resistance.

[0003] The weak gel structure of the weak gel drilling fluid system has unique rheological properties, including low apparent viscosity, high dynamic-plastic ratio, high viscosity at low shear rates, rapid shear recovery, no time dependence, strong resistance to temperature, salt-calcium invasion, and reservoir protection. It is widely used in offshore extended-reach wells, facilitating the suspension of drill cuttings, improving wellbore purification capabilities, and reservoir protection. The weak gel drilling fluid system has a low solids content, which helps reduce reservoir contamination and increase production. The system has a high LSRV value, effectively reducing the crossflow velocity of gas in fractures and wellbores, and shortening the cycle exhaust time. The polymer macromolecules in the weak gel drilling fluid adhere to the wellbore wall, forming a dense mud cake to seal microcracks and reduce the rate of gas and liquid entering the wellbore. The polymer macromolecules adsorb on the pores of the reservoir and microcracks, blocking the pore throats and increasing the resistance to gas and liquid flow. The polymer macromolecules form bridges with the temporary plugging agent particles, enhancing the gas Jamin effect and inhibiting gas invasion.

[0004] Patent No. ZL201410197739.6 discloses a weak gel, solid-free, water-based drilling fluid suitable for extended reach and horizontal wells. The drilling fluid provided by the invention is composed of a coating agent, a flow pattern modifier, a fluid loss control agent, an inhibitor, a lubricant, a pH adjuster, a corrosion inhibitor, salt, and fresh water. The weight percentages of the components used to prepare the weak gel, solid-free, water-based drilling fluid are as follows: coating agent: 0.5%-1%; flow pattern modifier: 0.5-1%; fluid loss control agent: 2%-6%; inhibitor: 0.5%-1%; lubricant: 1%-6%; pH adjuster: 0.2%-1%; corrosion inhibitor: 0.2%-0.5%; salt: 5%-40%, with the balance being water. The invention also discloses a preparation method. This weak gel, solid-free, water-based drilling fluid exhibits high viscosity at low shear rates, good temperature resistance, strong inhibitory properties, and lubricity. The system has a temperature resistance of 140°C.

[0005] Patent No. ZL201410198623.4 discloses an organic-inorganic composite weak gel flow pattern modifier for drilling fluids and its preparation method. This high-temperature-resistant flow pattern modifier is prepared from hydroxyethyl cellulose, polyanionic cellulose, carboxymethyl cellulose, xanthan gum, hydroxypropyl guar gum, serpentine asbestos fiber, fatty acid methyl ester, sodium tetraborate decahydrate, sodium sulfite, and water through kneading, crosslinking, exfoliation, and compounding. This flow pattern modifier exhibits excellent chemical stability, temperature and salt resistance, and easy degradation. It is fully compatible with solid-free water-based drilling fluids, improving their low-shear viscosity and preventing complex drilling accidents such as well collapse, stuck pipe, and lost circulation. It is also heat-resistant to 120°C.

[0006] Patent No. ZL201310644139.5 discloses a weak gelling agent for drilling fluid and its preparation method. The method is characterized by adding natural modified plant gum, acrylamide, N,N-dimethylacrylamide, a nonionic fluorocarbon surfactant, diacetone acrylamide, and soda ash to a reactor in a proportional order at room temperature. The pH is adjusted to 8-9, and after deoxygenation with nitrogen, an initiator is added. A polymerization reaction is carried out under ultraviolet irradiation, and the product is then dried to obtain the finished product. The product obtained by this method has excellent temperature resistance and viscosity-enhancing and shear-reducing effects. It can be used in horizontal wells to improve the drilling fluid's ability to carry cuttings, solving the problems of static suspended sand and dynamic sand carryover in horizontal well sections. It also has good compatibility and is suitable for both light and salt slurries, protecting reservoirs from damage.

[0007] The paper "High-Temperature-Resistant, Solid-Free, Weak-Gel Drilling and Completion Fluid Technology" (Wen Fei et al., Drilling Fluids and Completion Fluids, July 2016) describes a solid-free, weak-gel drilling and completion fluid system with a temperature resistance of 150°C. It features high viscosity, low shear rate viscosity, high temperature resistance, strong corrosion resistance, and readily degradable main agent materials. It is suitable for low-density, low-permeability, and poorly diagenetic formations. Field trials have demonstrated the system's strong leak and collapse prevention capabilities, as well as its excellent reservoir and environmental protection. The well's production exceeded that of adjacent wells by over 30%, achieving both safe drilling and increased oil production.

[0008] The paper "Research on High-Temperature Resistant Solid-Free Weak Gel Drilling Fluid System (Xu Mingbiao et al., Oilfield Chemistry, June 2012)" introduces a high-temperature resistant solid-free weak gel drilling fluid system used in reservoir drilling. It can withstand temperatures of 160°C and has excellent suspended sand-carrying properties. The weak gel formed has unique rheological properties, with low apparent viscosity, high dynamic-plastic ratio, high viscosity at low shear rates, and strong suspended sand-carrying capacity. It can effectively overcome the problems of difficult sand carrying and easy formation of sand beds in horizontal wells or highly deviated well sections, ensuring wellbore cleanliness.

[0009] Currently, published patents and scientific papers have reported on numerous indoor tests and field applications of weak-gel drilling fluid systems and core additives such as flow pattern modifiers and weak gelling agents. However, the systems' high-temperature resistance is generally less than 150°C. However, the bottomhole temperature of some operating wells exceeds 160°C, necessitating the development of a high-temperature-resistant, weak-gel anti-gas intrusion drilling fluid that maintains excellent weak-gel properties above 160°C to prevent and control gas intrusion. Summary of the Invention

[0010] Based on the deficiencies in the prior art, the present application aims to solve the problem of using weak gel drilling fluids with temperature resistance exceeding 160°C to prevent and control gas invasion, and provides a high-temperature resistant weak gel anti-gas invasion drilling fluid and a preparation method thereof, which overcomes the problem that conventional weak gel drilling fluids have low viscosity at a low shear rate of 160°C and low viscosity shear force, and are unable to inhibit gas invasion. The application realizes the high-temperature resistant weak gel drilling fluid system to prevent and control gas invasion, reduces the non-effective production time of drilling, improves drilling efficiency, and accelerates the speed of oil and gas exploration and development.

[0011] In order to achieve the above objectives, this application adopts the following technical solutions:

[0012] A high-temperature resistant weak gel anti-gas invasion drilling fluid, comprising the following components: water, formate, pH regulator, high-temperature stabilizer, viscosity enhancer, high-temperature resistant flow pattern regulator, high-temperature resistant fluid loss reducer, temperature-resistant plugging agent, temporary plugging agent, lubricant, defoamer and barite;

[0013] The weight percentage of each component in water is:

[0014]

[0015] in,

[0016] The water is fresh water.

[0017] The formate is selected from sodium formate and / or potassium formate;

[0018] Preferably, the formate is a mixture of 15%-65% sodium formate and 0-300% potassium formate.

[0019] The pH regulator is selected from sodium hydroxide and / or sodium carbonate.

[0020] Preferably, the pH regulator is a mixture of 0.6%-1.2% sodium hydroxide and 0.6% sodium carbonate.

[0021] The high temperature stabilizer is prepared by compounding a water-in-oil polymer emulsion with sodium thiosulfate and ethanolamine;

[0022] The mass ratio of the water-in-oil polymer emulsion, sodium thiosulfate and ethanolamine is 3:1:6.

[0023] The method for preparing the water-in-oil polymer emulsion comprises the following steps:

[0024] (1) First, add 100 parts by mass of kerosene and 3-6 parts by mass of Span 60 into a four-necked flask, heat it to 50-60°C, and stir to dissolve evenly to obtain the oil phase of the reaction;

[0025] (2) Add 50 parts by mass of deionized water, 1-2 parts by mass of sodium hydroxide, 12-16 parts by mass of acrylamide, 4-6 parts by mass of acrylic acid, 4-6 parts by mass of 2-acrylamide-2-methylpropanesulfonic acid, 1-2 parts by mass of N,N-methylenebisacrylamide and 2-4 parts by mass of Tween 80 to another flask, and stir thoroughly to obtain the aqueous phase of the reaction;

[0026] (3) adding the aqueous phase material prepared in step (2) to the oil phase flask in step (1), stirring thoroughly for 20-40 minutes, introducing nitrogen for 10 minutes to remove oxygen in the reaction, and raising the temperature to 40-60° C.; adding 0.2-0.4 parts by weight of ammonium persulfate (concentration 20%) and 0.2-0.4 parts by weight of sodium bisulfite (concentration 20%) as redox initiators, respectively, and keeping the temperature for reaction for 4-6 hours to obtain a white emulsion, namely, a water-in-oil polymer emulsion.

[0027] The thickener is a cellulose ether polymer derivative, which is composed of hydroxypropyl methylcellulose (HPMC), hydroxyethyl cellulose (HEC) and carboxymethyl cellulose (CMC).

[0028] One or more of the following are compounded;

[0029] Preferably, the cellulose ether polymer derivative is compounded by 80-90 parts of hydroxyethyl cellulose (HEC) and 10-20 parts of carboxymethyl cellulose (CMC).

[0030] The compounding described here is obtained by direct mixing.

[0031] The cellulose ether polymer derivative has good properties of thickening, suspending, dispersing, emulsifying, bonding, film forming, protecting moisture and providing protective colloid, and has good synergistic thickening and temperature resistance effects with biopolymers.

[0032] The high temperature resistant flow pattern regulator is a modified xanthan gum product obtained by modifying xanthan gum with epichlorohydrin, acetic acid and lauryl amide propyl dimethyl tertiary amine;

[0033] The preparation method of the high temperature resistant flow pattern regulator comprises the following steps:

[0034] (1) First, 100 parts by mass of ethanol solution (mass fraction 60%) and 50-60 parts by mass of lauryl amide propyl dimethyl tertiary amine were added to a flask, stirred evenly, and then 10-15 parts by mass of acetic acid were added dropwise. The temperature was raised to 55-65° C. and kept constant. 5 parts by mass of epichlorohydrin were added every 30 minutes, and a total of 15-25 parts by mass of epichlorohydrin were added. After reacting for 3-4 hours, a hydrophobic cationic modifier was obtained, which was stored for later use.

[0035] (2) Take 100 parts by mass of ethanol aqueous solution (mass fraction 80%), add 5-10 parts by mass of xanthan gum and 1-2 parts by mass of NaOH solution (mass fraction 20%), stir evenly, heat to 30-40°C, slowly add 8-12 parts by mass of hydrophobic cationic modifier epoxypropyl dodecyl quaternary ammonium salt, raise the temperature to 80-90°C, react for 4-6 hours, filter after the reaction, wash with ethanol 3 times, and dry in an oven at 80°C for 4 hours to obtain a modified xanthan gum product.

[0036] The high temperature resistant fluid loss reducer is prepared by graft copolymerization of natural starch modified with 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamide (AM) and N-vinylpyrrolidone (NVP);

[0037] The preparation method of the high temperature resistant fluid loss reducer comprises the following steps:

[0038] (1) First, 35-45 parts by weight of soluble starch and 100 parts by weight of deionized water were added to a flask, heated to 90° C. and stirred for 30 minutes to pregelatinize the starch until it became a transparent gelatinous state, thereby obtaining a pregelatinized starch solution;

[0039] (2) 8-12 parts by weight of AM, 36-48 parts by weight of AMPS, 6-10 parts by weight of NVP, and 50 parts by weight of deionized water were added to another flask, and the pH value of the solution was adjusted to 6-7 with NaOH to obtain a monomer solution;

[0040] (3) The monomer solution is added to the pregelatinized starch solution, nitrogen is introduced for 20 minutes, 0.05-0.1 parts by mass of sodium thiosulfate is added, the temperature is raised to 70-80°C, 0.6-1 parts by mass of potassium persulfate is added, the reaction is continued for 200-240 minutes, the reaction is stopped, the product is allowed to cool, the cooled product is washed with ethanol 2-3 times, and the white powder after drying and crushing is a high temperature resistant fluid loss reducer.

[0041] The heat-resistant plugging agent is prepared by drying a core-shell structure acrylic copolymer emulsion obtained by polymerizing methyl methacrylate (MMA), butyl acrylate (BA) and vinyltrimethoxysilane (A-171).

[0042] The preparation method of the heat-resistant plugging agent comprises the following steps:

[0043] (1) adding 85 parts by mass of deionized water, 0.1-0.15 parts by mass of sodium ethoxyphenol ether sulfate and 0.1-0.15 parts by mass of nonylphenol polyoxyethylene ether into a three-necked flask, stirring and dissolving them uniformly; then slowly adding 18-23 parts by mass of methyl methacrylate (MMA) and 15-20 parts by mass of butyl acrylate (BA) monomer mixture into the three-necked flask, stirring and dissolving them uniformly, and obtaining a pre-emulsified shell monomer solution;

[0044] (2) Add 15 parts by mass of deionized water, 0.2-0.3 parts by mass of sodium ethoxyphenol ether sulfate and 0.2-0.3 parts by mass of nonylphenol polyoxyethylene ether to a four-necked flask, stir and dissolve evenly, then add 3-5 parts by mass of methyl methacrylate (MMA), 2-4 parts by mass of butyl acrylate (BA), and 4-6 parts by mass of vinyltrimethoxysilane (A-171) monomers to the four-necked flask, stir and mix evenly, and emulsify for 30-40 minutes, then heat to 80-90° C., add 0.2-0.3 parts by mass of potassium persulfate (concentration 20%), wait until the emulsion appears a blue phase, and keep the temperature for reaction for 30 minutes to prepare a seed emulsion;

[0045] (3) uniformly adding the shell monomer solution prepared in step (1) and 0.5-0.7 parts by mass of potassium persulfate (concentration 20%) to the seed emulsion at 80-90° C., and adding equal amounts of sodium carbonate and sodium bicarbonate as pH regulators to adjust the pH to neutral; maintaining the reaction temperature, the system maintains a blue phase, and after the addition is completed, the temperature is kept for 30 minutes, and then cooled to 60-70° C., 0.04-0.06 parts by mass of tert-butyl hydroperoxide and 0.04-0.06 parts by mass of bleaching agent are added twice at intervals of 30 minutes to carry out residual monomer elimination reaction, stop the reaction, and let the product stand to cool. After the cooled product is washed with ethanol 2-3 times, the white powder after drying and crushing is the heat-resistant plugging agent.

[0046] The temporary plugging agent is calcium carbonate powder; preferably, the calcium carbonate powder has a particle size of 200-800 mesh and an acid solubility rate of >96%.

[0047] The lubricant is one or more of modified vegetable oil lubricants, polyol fatty acid esters, silicone emulsions and polymeric alcohol lubricants.

[0048] Preferably, the modified vegetable oil is selected from one or more of BIOLUBE, RH-B and BZ-BL; the polyol fatty acid ester lubricant is SYT-2; the silicone emulsion lubricant is JMR and / or NSR-1; and the polyol lubricant is JXL.

[0049] The defoaming agent is a polyether defoaming agent or an organosilicon defoaming agent.

[0050] Preferably, the polyether defoamer is a nonionic surfactant formed by ring-opening polymerization of ethylene oxide (EO) and propylene oxide (PO), and is selected from one or more of SD-1, HFX101 and RXJ; the silicone defoamer is a defoamer emulsified with water using silicone grease, emulsifier, thickener, etc., and is selected from LS or / and HXP-3.

[0051] The barite is commercially available barite with a mesh size of 200-1000 meshes.

[0052] The present application also provides a method for preparing the above-mentioned high-temperature resistant weak gel anti-gas invasion drilling fluid, comprising the following steps:

[0053] Add the formulated amount of tap water, formate and pH regulator to the high-stirring cup in sequence, and stir at high speed for 10 minutes; then add the viscosity enhancer and stir for 10 minutes; then add the high-temperature resistant flow pattern regulator and defoamer and stir at high speed for 10 minutes; then add the high-temperature resistant fluid loss reducer and the temperature-resistant plugging agent and stir at high speed for 10 minutes; then add the high-temperature stabilizer and stir at high speed for 10 minutes; then add the temporary plugging agent and stir at high speed for 10 minutes; then add the lubricant and stir at high speed for 10 minutes; then add the barite and stir at high speed for 20 minutes to obtain the high-temperature resistant weak gel anti-gas intrusion drilling fluid.

[0054] The speed of the high-speed stirring is 10000 rpm.

[0055] Compared with the prior art, the present invention has the following advantages:

[0056] 1. The high-temperature resistant weak gel drilling fluid technology provided by the present invention has a simple formulation and configuration process and is highly applicable on site;

[0057] 2. The high temperature resistant weak gel drilling fluid technology provided by the present invention has a high density and temperature application range, with a density of up to 1.8g / cm 3 , the temperature can reach 180℃;

[0058] 3. The high-temperature resistant weak gel drilling fluid technology provided by the present invention has good rheological properties and reservoir protection performance. The system has high viscosity shear force and low shear rate viscosity, which can effectively reduce the upward speed of gas. The plugging layer formed by the system is dense, and the drilling fluid and its filtrate in the wellbore are difficult to flow into the formation. The gas in the reservoir is also difficult to invade the wellbore, and the anti-gas invasion effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a schematic diagram of the anti-gas intrusion evaluation device for the bubble simulation experiment;

[0060] Reference numerals: 1- one-way throttle valve; 2- liquid pump; 3- exhaust hole; 4- pressure gauge; 5- simulated wellbore; 6- nozzle; 7- discharge valve; 8- liquid storage tank; 9- pressure gauge; 10- pressure reducing valve; 11- high-pressure gas cylinder;

[0061] Figure 2 This is a schematic diagram of the gas invasion prevention evaluation device for core flooding and plugging experiments;

[0062] Figure numerals: a-injection pump; b-flow meter; c-simulated wellbore with confining pressure pump; c-1 simulated core with fracture; c-2 core holder with heating jacket; c-3 confining pressure gauge; d-pressure regulating valve; e-high-pressure gas cylinder; f-liquid storage bottle. DETAILED DESCRIPTION

[0063] The composition and properties of the high-temperature resistant weak gel anti-gas invasion drilling fluid provided by the present invention are further illustrated below with reference to examples, but the present invention is not limited thereto.

[0064] Basic Example 1 Preparation Method of High-Temperature Stabilizer

[0065] The following steps are involved:

[0066] (1) First, add 100 parts by mass of kerosene and 5 parts by mass of Span 60 into a four-necked flask, heat it to 55°C, and stir until uniformly dissolved to obtain the oil phase of the reaction;

[0067] (2) Add 50 parts by mass of deionized water, 1 part by mass of sodium hydroxide, 14 parts by mass of acrylamide, 5 parts by mass of acrylic acid, 5 parts by mass of 2-acrylamide-2-methylpropanesulfonic acid, 1.5 parts by mass of N,N-methylenebisacrylamide and 3 parts by mass of Tween 80 to another flask and stir thoroughly to obtain the aqueous phase of the reaction;

[0068] (3) adding the aqueous phase material prepared in step (2) to the oil phase flask in step (1), stirring thoroughly for 30 minutes, introducing nitrogen for 10 minutes to remove oxygen in the reaction, and raising the temperature to 50° C.; adding 0.2 parts by mass of ammonium persulfate (concentration 20%) and 0.2 parts by mass of sodium bisulfite (concentration 20%) as redox initiators, respectively, and keeping the temperature for reaction for 4-6 hours to obtain a white emulsion, which is a water-in-oil polymer emulsion;

[0069] The prepared water-in-oil polymer emulsion, sodium thiosulfate and ethanolamine were mixed in a mass ratio of 3:1:6, the temperature was raised to 50° C., and the mixture was stirred for 10 minutes until uniform to obtain a high-temperature stabilizer.

[0070] Basic Example 2 Preparation Method of High-Temperature Resistant Flow Regulator

[0071] The following steps are involved:

[0072] (1) First, 100 parts by mass of ethanol solution (60% by mass) and 55 parts by mass of lauryl amide propyl dimethyl tertiary amine were added to a flask, stirred evenly, and then 12 parts by mass of acetic acid were added dropwise. The temperature was raised to 60°C and kept constant. 5 parts by mass of epichlorohydrin were added every 30 minutes, and a total of 20 parts by mass of epichlorohydrin were added. After reacting for 3 hours, a hydrophobic cationic modifier was obtained, which was stored for later use.

[0073] (2) Take 100 parts by mass of ethanol aqueous solution (mass fraction 80%), add 6 parts by mass of xanthan gum and 1 part by mass of NaOH solution (mass fraction 20%), stir evenly, heat to 30°C and slowly add 10 parts by mass of hydrophobic cationic modifier epoxypropyl dodecyl quaternary ammonium salt, raise the temperature to 90°C and react for 4 hours. After the reaction is completed, filter and wash with ethanol 3 times, dry in an oven at 80°C for 4 hours to obtain a modified xanthan gum product.

[0074] Basic Example 3 Preparation Method of High-Temperature Resistant Fluid Loss Reducer

[0075] The following steps are involved:

[0076] (1) First, 40 parts by weight of soluble starch and 100 parts by weight of deionized water were added to a flask, heated to 90°C and stirred for 30 minutes to pregelatinize the starch until it became a transparent gelatinous state, thereby obtaining a pregelatinized starch solution;

[0077] (2) 10 parts by mass of AM, 40 parts by mass of AMPS, 8 parts by mass of NVP, and 50 parts by mass of deionized water were added to another flask, and the pH value of the solution was adjusted to 7 with NaOH to obtain a monomer solution;

[0078] (3) The monomer solution was added to the pregelatinized starch solution, nitrogen was introduced for 20 minutes, 0.1 parts by mass of sodium thiosulfate was added, the temperature was raised to 80°C, 0.8 parts by mass of potassium persulfate was added, the reaction was stopped, the product was allowed to cool, the cooled product was washed with ethanol three times, and the white powder after drying and crushing was obtained as a high temperature resistant fluid loss reducer.

[0079] Basic Example 4 Preparation Method of Heat-Resistant Plugging Agent

[0080] The following steps are involved:

[0081] (1) 85 parts by mass of deionized water, 0.1 parts by mass of sodium ethoxyphenol ether sulfate, and 0.1 parts by mass of nonylphenol polyoxyethylene ether were added to a three-necked flask and stirred to dissolve uniformly; then 20 parts by mass of methyl methacrylate (MMA) and 18 parts by mass of butyl acrylate (BA) monomer mixture were slowly added to the three-necked flask, and stirred to obtain a pre-emulsified shell monomer solution;

[0082] (2) Add 15 parts by mass of deionized water, 0.2 parts by mass of sodium ethoxyphenol ether sulfate and 0.2 parts by mass of nonylphenol polyoxyethylene ether to a four-necked flask, stir and dissolve evenly, then add 3 parts by mass of methyl methacrylate (MMA), 3 parts by mass of butyl acrylate (BA) and 5 parts by mass of vinyltrimethoxysilane (A-171) monomers which are evenly mixed into the four-necked flask, stir and mix evenly, and emulsify for 30 minutes, then heat to 85° C., add 0.3 parts by mass of potassium persulfate (concentration 20%), wait until the emulsion shows a blue phase, and keep the temperature for reaction for 30 minutes to prepare a seed emulsion;

[0083] (3) uniformly adding the shell monomer solution prepared in step (1) and 0.6 parts by mass of potassium persulfate (concentration 20%) to the seed emulsion at 85° C., and adding equal amounts of sodium carbonate and sodium bicarbonate as pH regulators to adjust the pH to neutral; maintaining the reaction temperature, the system maintains a blue phase, and after the addition is completed, the temperature is kept for 30 minutes, and then cooled to 65° C., 0.05 parts by mass of tert-butyl hydroperoxide and 0.05 parts by mass of bleaching agent are added twice at intervals of 30 minutes to carry out residual monomer elimination reaction, stop the reaction, and let the product stand to cool. After the cooled product is washed with ethanol three times, the white powder after drying and crushing is the heat-resistant plugging agent.

[0084] Example 1 A high-temperature resistant weak gel anti-gas invasion drilling fluid and its preparation method

[0085] The weight percentage of each component in water is:

[0086]

[0087] The viscosity enhancer is a mixture of 90 parts of hydroxyethyl cellulose (HEC) and 10 parts of carboxymethyl cellulose (CMC);

[0088] Preparation method: comprising the following steps:

[0089] Add the formulated amount of tap water, formate and pH regulator to the high-stirring cup in sequence, and stir at high speed for 10 minutes; then add the viscosity enhancer and stir for 10 minutes; then add the high-temperature resistant flow pattern regulator and defoamer and stir at high speed for 10 minutes; then add the high-temperature resistant fluid loss reducer and the heat-resistant plugging agent and stir at high speed for 10 minutes; then add the high-temperature stabilizer and stir at high speed for 10 minutes; then add the temporary plugging agent and stir at high speed for 10 minutes; then add the lubricant and stir at high speed for 10 minutes; then add the barite and stir at high speed for 20 minutes to obtain the high-temperature resistant weak gel anti-gas intrusion drilling fluid;

[0090] The speed of the high-speed stirring is 10000 rpm.

[0091] The drilling fluid system prepared in this example has a density of 1.2 g / cm 3The hot rolling temperature of the drilling fluid system is 180℃.

[0092] Example 2 A high-temperature resistant weak gel anti-gas invasion drilling fluid and its preparation method

[0093] The weight percentage of each component in water is:

[0094]

[0095] The viscosity increasing agent is a mixture of 85 parts of hydroxyethyl cellulose (HEC) and 15 parts of carboxymethyl cellulose (CMC).

[0096] Preparation method: comprising the following steps:

[0097] Add the formulated amount of tap water, formate and pH regulator to the high-stirring cup in sequence, and stir at high speed for 10 minutes; then add the viscosity enhancer and stir for 10 minutes; then add the high-temperature resistant flow pattern regulator and defoamer and stir at high speed for 10 minutes; then add the high-temperature resistant fluid loss reducer and the heat-resistant plugging agent and stir at high speed for 10 minutes; then add the high-temperature stabilizer and stir at high speed for 10 minutes; then add the temporary plugging agent and stir at high speed for 10 minutes; then add the lubricant and stir at high speed for 10 minutes; then add the barite and stir at high speed for 20 minutes to obtain the high-temperature resistant weak gel anti-gas intrusion drilling fluid;

[0098] The speed of the high-speed stirring is 10000 rpm.

[0099] The drilling fluid system prepared in this example has a density of 1.4 g / cm 3 The hot rolling temperature of the drilling fluid system is 180℃.

[0100] Example 3 A high-temperature resistant weak gel anti-gas invasion drilling fluid and its preparation method

[0101] The weight percentage of each component in water is:

[0102]

[0103] The viscosity increasing agent is a mixture of 80 parts of hydroxyethyl cellulose (HEC) and 20 parts of carboxymethyl cellulose (CMC).

[0104] Preparation method: comprising the following steps:

[0105] Add the formulated amount of tap water, formate and pH regulator to the high-stirring cup in sequence, and stir at high speed for 10 minutes; then add the viscosity enhancer and stir for 10 minutes; then add the high-temperature resistant flow pattern regulator and defoamer and stir at high speed for 10 minutes; then add the high-temperature resistant fluid loss reducer and the heat-resistant plugging agent and stir at high speed for 10 minutes; then add the high-temperature stabilizer and stir at high speed for 10 minutes; then add the temporary plugging agent and stir at high speed for 10 minutes; then add the lubricant and stir at high speed for 10 minutes; then add the barite and stir at high speed for 20 minutes to obtain the high-temperature resistant weak gel anti-gas intrusion drilling fluid;

[0106] The speed of the high-speed stirring is 10000 rpm.

[0107] The drilling fluid system prepared in this example has a density of 1.6 g / cm 3 The hot rolling temperature of the drilling fluid system is 180℃.

[0108] Example 4 A high-temperature resistant weak gel anti-gas invasion drilling fluid and its preparation method

[0109] The weight percentage of each component in water is:

[0110]

[0111] The viscosity increasing agent is a mixture of 80 parts of hydroxyethyl cellulose (HEC) and 20 parts of carboxymethyl cellulose (CMC).

[0112] Preparation method: comprising the following steps:

[0113] Add the formulated amount of tap water, formate and pH regulator to the high-stirring cup in sequence, and stir at high speed for 10 minutes; then add the viscosity enhancer and stir for 10 minutes; then add the high-temperature resistant flow pattern regulator and defoamer and stir at high speed for 10 minutes; then add the high-temperature resistant fluid loss reducer and the heat-resistant plugging agent and stir at high speed for 10 minutes; then add the high-temperature stabilizer and stir at high speed for 10 minutes; then add the temporary plugging agent and stir at high speed for 10 minutes; then add the lubricant and stir at high speed for 10 minutes; then add the barite and stir at high speed for 20 minutes to obtain the high-temperature resistant weak gel anti-gas intrusion drilling fluid;

[0114] The speed of the high-speed stirring is 10000 rpm.

[0115] The density of the drilling fluid system prepared in this application is 1.8 g / cm 3 The hot rolling temperature of the drilling fluid system is 180℃.

[0116] Example 5 A high-temperature resistant weak gel anti-gas invasion drilling fluid and its preparation method

[0117] The weight percentage of each component in water is:

[0118]

[0119] The viscosity increasing agent is a mixture of 80 parts of hydroxyethyl cellulose (HEC) and 20 parts of carboxymethyl cellulose (CMC).

[0120] Preparation method: comprising the following steps:

[0121] Add the formulated amount of tap water, formate and pH regulator to the high-stirring cup in sequence, and stir at high speed for 10 minutes; then add the viscosity enhancer and stir for 10 minutes; then add the high-temperature resistant flow pattern regulator and defoamer and stir at high speed for 10 minutes; then add the high-temperature resistant fluid loss reducer and the heat-resistant plugging agent and stir at high speed for 10 minutes; then add the high-temperature stabilizer and stir at high speed for 10 minutes; then add the temporary plugging agent and stir at high speed for 10 minutes; then add the lubricant and stir at high speed for 10 minutes; then add the barite and stir at high speed for 20 minutes to obtain the high-temperature resistant weak gel anti-gas intrusion drilling fluid;

[0122] The speed of the high-speed stirring is 10000 rpm.

[0123] The drilling fluid system prepared in this example has a density of 1.6 g / cm 3 The hot rolling temperature of the drilling fluid system is 140℃.

[0124] Example 6 A high-temperature resistant weak gel anti-gas invasion drilling fluid and its preparation method

[0125] The weight percentage of each component in water is:

[0126]

[0127] The viscosity increasing agent is a mixture of 80 parts of hydroxyethyl cellulose (HEC) and 20 parts of carboxymethyl cellulose (CMC).

[0128] Preparation method: comprising the following steps:

[0129] Add the formulated amount of tap water, formate and pH regulator to the high-stirring cup in sequence, and stir at high speed for 10 minutes; then add the viscosity enhancer and stir for 10 minutes; then add the high-temperature resistant flow pattern regulator and defoamer and stir at high speed for 10 minutes; then add the high-temperature resistant fluid loss reducer and the heat-resistant plugging agent and stir at high speed for 10 minutes; then add the high-temperature stabilizer and stir at high speed for 10 minutes; then add the temporary plugging agent and stir at high speed for 10 minutes; then add the lubricant and stir at high speed for 10 minutes; then add the barite and stir at high speed for 20 minutes to obtain the high-temperature resistant weak gel anti-gas intrusion drilling fluid;

[0130] The speed of the high-speed stirring is 10000 rpm.

[0131] The drilling fluid system prepared in this example has a density of 1.6 g / cm 3 , the hot rolling temperature of the drilling fluid system is 160℃.

[0132] Example 7 A high-temperature resistant weak gel anti-gas invasion drilling fluid and its preparation method

[0133] The weight percentage of each component in water is:

[0134]

[0135] The viscosity increasing agent is a mixture of 80 parts of hydroxyethyl cellulose (HEC) and 20 parts of carboxymethyl cellulose (CMC).

[0136] Preparation method: comprising the following steps:

[0137] Add the formulated amount of tap water, formate and pH regulator to the high-stirring cup in sequence, and stir at high speed for 10 minutes; then add the viscosity enhancer and stir for 10 minutes; then add the high-temperature resistant flow pattern regulator and defoamer and stir at high speed for 10 minutes; then add the high-temperature resistant fluid loss reducer and the heat-resistant plugging agent and stir at high speed for 10 minutes; then add the high-temperature stabilizer and stir at high speed for 10 minutes; then add the temporary plugging agent and stir at high speed for 10 minutes; then add the lubricant and stir at high speed for 10 minutes; then add the barite and stir at high speed for 20 minutes to obtain the high-temperature resistant weak gel anti-gas intrusion drilling fluid;

[0138] The speed of the high-speed stirring is 10000 rpm.

[0139] The drilling fluid system prepared in this example has a density of 1.6 g / cm 3 The hot rolling temperature of the drilling fluid system is 190℃.

[0140] Comparative Example 1 A high-temperature resistant weak gel anti-gas invasion drilling fluid and its preparation method

[0141] The weight percentage of each component in water is:

[0142]

[0143]

[0144] The viscosity increasing agent is a mixture of 80 parts of hydroxyethyl cellulose (HEC) and 20 parts of carboxymethyl cellulose (CMC).

[0145] Preparation method: comprising the following steps:

[0146] Add the formulated amount of tap water, formate and pH regulator to the high-stirring cup in sequence, and stir at high speed for 10 minutes; then add the viscosity enhancer and stir for 10 minutes; then add the high-temperature resistant flow pattern regulator and defoamer and stir at high speed for 10 minutes; then add the high-temperature resistant fluid loss reducer and the heat-resistant plugging agent and stir at high speed for 10 minutes; then add the high-temperature stabilizer and stir at high speed for 10 minutes; then add the temporary plugging agent and stir at high speed for 10 minutes; then add the lubricant and stir at high speed for 10 minutes; then add the barite and stir at high speed for 20 minutes to obtain the high-temperature resistant weak gel anti-gas intrusion drilling fluid;

[0147] The speed of the high-speed stirring is 10000 rpm.

[0148] The drilling fluid system prepared in this example has a density of 1.6 g / cm 3 , the hot rolling temperature of the drilling fluid system is 160℃.

[0149] Comparative Example 2 A high-temperature resistant weak gel anti-gas invasion drilling fluid and its preparation method

[0150] The weight percentage of each component in water is:

[0151]

[0152]

[0153] The viscosity increasing agent is a mixture of 80 parts of hydroxyethyl cellulose (HEC) and 20 parts of carboxymethyl cellulose (CMC).

[0154] Preparation method: comprising the following steps:

[0155] Add the formulated amount of tap water, formate and pH regulator to the high-stirring cup in sequence, and stir at high speed for 10 minutes; then add the viscosity enhancer and stir for 10 minutes; then add the high-temperature resistant flow pattern regulator and defoamer and stir at high speed for 10 minutes; then add the high-temperature resistant fluid loss reducer and the heat-resistant plugging agent and stir at high speed for 10 minutes; then add the high-temperature stabilizer and stir at high speed for 10 minutes; then add the temporary plugging agent and stir at high speed for 10 minutes; then add the lubricant and stir at high speed for 10 minutes; then add the barite and stir at high speed for 20 minutes to obtain the high-temperature resistant weak gel anti-gas intrusion drilling fluid;

[0156] The speed of the high-speed stirring is 10000 rpm.

[0157] The drilling fluid system prepared in this example has a density of 1.6 g / cm 3 , the hot rolling temperature of the drilling fluid system is 160℃.

[0158] Comparative Example 3

[0159] Polysulfone water-based drilling fluid: 100 parts by mass of freshwater soil slurry (soil slurry mass fraction 2%), 0.2 parts by mass of sodium carbonate, 0.15 parts by mass of sodium hydroxide, 0.2 parts by mass of KPAM, 0.3 parts by mass of PAC-LV, 1.5 parts by mass of CMC-HV, 2 parts by mass of SMP-1, 2 parts by mass of SPNH, 2 parts by mass of FT-1, 5 parts by mass of potassium chloride, and 90 parts by mass of barite are fully mixed to obtain a polysulfone water-based drilling fluid.

[0160] The density of the prepared drilling fluid system is 1.6 g / cm 3 , the hot rolling temperature of the drilling fluid system is 160℃.

[0161] Comparative Example 4

[0162] Deionized water.

[0163] Effect experiment

[0164] The rheological properties and filtration properties of Examples 1-7 and Comparative Examples 1-3 were evaluated according to GB / T 16783.1-2012 "Field Testing of Drilling Fluids in the Petroleum and Natural Gas Industry Part 1: Water-Based Drilling Fluids". The experimental results are shown in Table 1.

[0165] The viscosity of Examples 1-7 and Comparative Examples 1-3 was measured using a Brookfield viscometer at a rotation speed of 0.3 r / min. The experimental results are shown in Table 1.

[0166] Attachment Figure 1 This is a schematic diagram of a bubble simulation test and evaluation device for preventing gas intrusion. It consists of a simulated wellbore and a simulated formation. The simulated formation primarily comprises a high-pressure gas cylinder, a pressure reducing valve, a pressure gauge, and a nozzle. The simulated wellbore is made of glass, connected to the simulated formation at the bottom and equipped with a vent at the top, with a scale engraved on the surface. Gas intrudes into the wellbore through the nozzle under the influence of a pressure differential. The migration velocity of the bubbles in the experimental solution can be used to evaluate the gas migration velocity in the drilling fluid systems of Examples 1-3, 5-7, Comparative Examples 1-2, and Comparative Example 3, which was not weighted with barite. The results are shown in Table 2.

[0167] Attachment Figure 2 It is a schematic diagram of the core displacement plugging experiment anti-gas intrusion evaluation device, which consists of an injection pump, a flow meter, a core clamp, a simulated wellbore with a confining pressure pump, a simulated core with cracks, a confining pressure gauge, and a high-pressure gas cylinder component. The plugging and anti-gas intrusion effect of the drilling fluid can be evaluated by a pressure test. The higher the pressure bearing capacity of the forward pressure bearing test of the drilling fluid, the smaller the filtration loss, which means that the denser the plugging layer, the more difficult it is for the drilling fluid and its filtrate in the wellbore to invade the reservoir; the higher the pressure value of the reverse pressure bearing test, the greater the resistance of the reservoir gas to invading the wellbore, and the better the plugging effect. The leakage before complete plugging, the forward gas drive pressure and the reverse gas drive pressure of Examples 1-7 and Comparative Examples 1-3 were measured, and the experimental results are shown in Table 3.

[0168] Table 1 Basic properties of drilling fluid

[0169]

[0170]

[0171] Note: T: drilling fluid aging temperature, °C; ρ: drilling fluid density, g / cm 3 ; AV: apparent viscosity of drilling fluid, mPa·s; PV: plastic viscosity of drilling fluid, mPa·s; YP: dynamic shear force of drilling fluid, Pa; YP / PV: dynamic plastic ratio of drilling fluid, dimensionless; Φ6: reading of 6 revolutions of six-speed rotary viscometer, dimensionless; Φ3: reading of 3 revolutions of six-speed rotary viscometer, dimensionless; API: medium-pressure water loss of drilling fluid (0.7 MPa, T, 30 min), mL; HTHP: high-temperature and high-pressure water loss of drilling fluid (3.5 MPa, T, 30 min), mL; LSRV value: low shear rate viscosity of drilling fluid, mPa·s.

[0172] According to the above table 1, examples 1, 2, 3, 4 and examples 3, 5, 6, 7, it can be seen that the high temperature resistant weak gel anti-gas invasion drilling fluid system is 1.80g / cm 3 and below 160°C, the rheological properties, fluid loss properties and low shear rate viscosity parameters are good and remain stable. When the temperature rises to 180°C, the dynamic shear force and dynamic plastic ratio decrease, but are still within the control range. When the temperature rises to 190°C, the shear force and dynamic plastic ratio of the system further decrease, and the low shear rate viscosity also decreases significantly. It can be seen from Example 3 and Comparative Example 1 that when the system does not add a high-temperature stabilizer, the shear force, dynamic plastic ratio and low shear rate viscosity decrease significantly, and the API and high-temperature and high-pressure fluid loss increase, which is not conducive to performance stability. From Example 3 and Comparative Example 2, when the system does not add a high-temperature resistant flow pattern modifier, the shear force, dynamic plastic ratio and low shear rate viscosity also decrease significantly, and the API and high-temperature and high-pressure fluid loss also increase. From Example 3 and Comparative Example 3, the rheological properties and fluid loss properties of the high-temperature resistant weak gel anti-gas intrusion drilling fluid system are slightly better than those of the water-based polysulfone system, especially the low shear rate viscosity is much higher than that of the water-based polysulfone system.

[0173] Table 2. Anti-gas invasion performance of drilling fluid measured by bubble simulation experiment anti-gas invasion evaluation device

[0174] drilling fluid <![CDATA[T 泡 ]]> <![CDATA[V 泡 ]]> Example 1 9.40 0.085 Example 2 9.52 0.084 Example 3 9.58 0.084 Example 5 9.66 0.083 Example 6 9.80 0.082 Example 7 9.46 0,085 Comparative Example 1 8.26 0.097 Comparative Example 2 8.38 0.095 Comparative Example 3 8.08 0.099 Comparative Example 4 3.40 0.235

[0175] Note: T 泡 : time it takes for bubbles in the drilling fluid to reach the liquid surface from the bottom of the simulated wellbore, s; V 泡 : Rising velocity of bubbles in drilling fluid, m / s.

[0176] As shown in Table 2 above, Examples 1-7 have relatively large dynamic-to-plastic ratios and low-shear-rate viscosities, resulting in a longer time for bubbles to reach the liquid surface from the bottom of the simulated wellbore, and a slower gas rise rate. Comparative Examples 1, 2, and 3 have lower dynamic-to-plastic ratios and low-shear-rate viscosities, resulting in a faster gas rise rate within the system. This lower gas rise rate within the system allows for more safe working time.

[0177] Table 3 Core displacement plugging experiment gas invasion prevention evaluation device measuring drilling fluid gas invasion prevention performance

[0178] drilling fluid <![CDATA[FL 封 ]]> <![CDATA[P 正 ]]> <![CDATA[P 反 ]]> Example 1 0.4 3.2 1.2 Example 2 0.4 3.4 1.2 Example 3 0.4 3.2 1.1 Example 4 0.4 3.4 1.1 Example 5 0.2 3.6 1.4 Example 6 0.4 3.6 1.3 Example 7 0.6 3.0 1.0 Comparative Example 1 0.8 2.4 0.8 Comparative Example 2 1.0 2.4 0.6 Comparative Example 3 0.6 2.0 0.6

[0179] Note: FL 封 : Loss of simulated core before complete plugging, ml; P 正 : Forward gas drive pressure, MPa; P 反 : Reverse gas drive pressure, MPa.

[0180] As can be seen in Table 3 above, in Examples 1-7 and Comparative Examples 1-3, the simulated core loss before complete plugging is small, and the forward and reverse gas drive pressures are large. The high-temperature-resistant weak gel drilling fluid system can form a plugging zone on the core surface and at the fracture entrance, and the temporary plugging particles can prevent drilling fluid from invading the fracture. The system exhibits a high forward pressure and low fluid loss at different fracture widths, while also exhibiting a high reverse pressure. This makes it difficult for wellbore drilling fluid to invade the formation, increasing the resistance to reservoir gas invading the wellbore and making displacement gas invasion more difficult.

[0181] In summary, the seven groups of drilling fluids provided by the present invention, after aging at different densities and temperatures: have good rheological properties, low API and high-temperature and high-pressure fluid loss, can withstand high temperatures of 180°C, and have a density of up to 1.8 g / cm3; the dynamic plastic ratio and the 6-turn and 3-turn readings are large, and the low shear rate viscosity is large, which is beneficial to reducing the upward speed of gas in the system; the system has a forward pressure of >3 MPa, a fluid loss of <1 ml, and a reverse pressure of >1 MPa, and the wellbore drilling fluid is difficult to invade the formation, the reservoir gas has a large resistance to invading the wellbore, and displacement gas invasion is difficult to occur.

Claims

1. A high-temperature resistant weak gel anti-gas invasion drilling fluid, characterized by: The composition includes the following components: water, formate, pH regulator, high temperature stabilizer, viscosity enhancer, high temperature resistant flow pattern regulator, high temperature resistant fluid loss reducer, temperature resistant plugging agent, temporary plugging agent, lubricant, defoamer and barite; The weight percentage of each component in water is: Water: 100%; Formate: 15%-300%; pH adjuster: 1.2%-1.8%; High temperature stabilizer: 0.8%-1.6%; Tackifier: 0.4%-0.8%; High temperature resistance flow pattern regulator: 0.6%-1.0% High temperature resistant fluid loss reducer: 2.0%-3.0%; Heat-resistant plugging agent: 1.0%-3.0%; Temporary plugging agent: 0%-8.0%; Lubricant: 0-3.0%; Defoaming agent: 0%-1.0%; Barite: balance; The high-temperature stabilizer is prepared by compounding a water-in-oil polymer emulsion with sodium thiosulfate and ethanolamine; the mass ratio of the water-in-oil polymer emulsion, sodium thiosulfate and ethanolamine is 3:1:6; The high temperature resistant flow pattern regulator is a modified xanthan gum product obtained by modifying xanthan gum with epichlorohydrin, acetic acid and lauryl amide propyl dimethyl tertiary amine; The high temperature resistant fluid loss reducer is prepared by modifying natural starch with 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamide (AM) and N-vinylpyrrolidone (NVP) through graft copolymerization.

2. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 1, characterized in that: The formate is selected from sodium formate and / or potassium formate.

3. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 2, characterized in that: The formate is a mixture of 15%-65% sodium formate and 0-300% potassium formate.

4. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 1, characterized in that: The pH regulator is selected from sodium hydroxide and / or sodium carbonate.

5. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 4, characterized in that: The pH regulator is a mixture of 0.6%-1.2% sodium hydroxide and 0.6% sodium carbonate.

6. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 1, characterized in that: The method for preparing the water-in-oil polymer emulsion comprises the following steps: (1) First, add 100 parts by mass of kerosene and 3-6 parts by mass of Span 60 into a four-necked flask, heat it to 50-60°C, and stir to dissolve evenly to obtain the oil phase of the reaction; (2) Add 50 parts by mass of deionized water, 1-2 parts by mass of sodium hydroxide, 12-16 parts by mass of acrylamide, 4-6 parts by mass of acrylic acid, 4-6 parts by mass of 2-acrylamide-2-methylpropanesulfonic acid, 1-2 parts by mass of N,N-methylenebisacrylamide and 2-4 parts by mass of Tween 80 to another flask, and stir thoroughly to obtain the aqueous phase of the reaction; (3) adding the aqueous phase material prepared in step (2) to the oil phase flask in step (1), stirring thoroughly for 20-40 minutes, introducing nitrogen for 10 minutes to remove oxygen in the reaction, and raising the temperature to 40-60° C.; adding 0.2-0.4 parts by weight of 20% ammonium persulfate and 0.2-0.4 parts by weight of 20% sodium bisulfite as redox initiators, respectively, and keeping the temperature for reaction for 4-6 hours to obtain a white emulsion, namely, a water-in-oil polymer emulsion.

7. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 1, characterized in that: The viscosity enhancer is a cellulose ether polymer derivative, which is prepared by compounding one or more of hydroxypropyl methylcellulose (HPMC), hydroxyethyl cellulose (HEC) and carboxymethyl cellulose (CMC).

8. The high temperature resistant weak gel anti-gas invasion drilling fluid according to claim 7, characterized in that: The cellulose ether polymer derivative is compounded by 80-90 parts of hydroxyethyl cellulose (HEC) and 10-20 parts of carboxymethyl cellulose (CMC).

9. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 1, characterized in that: The preparation method of the high temperature resistant flow pattern regulator comprises the following steps: (1) First, 100 parts by mass of a 60% ethanol solution and 50-60 parts by mass of lauryl amide propyl dimethyl tertiary amine were added to a flask, stirred evenly, and then 10-15 parts by mass of acetic acid were added dropwise. The temperature was raised to 55-65° C. and kept constant. 5 parts by mass of epichlorohydrin were added every 30 minutes, and a total of 15-25 parts by mass of epichlorohydrin were added. After reacting for 3-4 hours, a hydrophobic cationic modifier was obtained, which was stored for later use. (2) Take 100 parts by mass of 80% ethanol aqueous solution, add 5-10 parts by mass of xanthan gum and 1-2 parts by mass of 20% NaOH solution, stir evenly, heat to 30-40°C, slowly add 8-12 parts by mass of hydrophobic cationic modifier epoxypropyl dodecyl quaternary ammonium salt, raise the temperature to 80-90°C, react for 4-6 hours, filter after the reaction, wash with ethanol 3 times, and dry in an oven at 80°C for 4 hours to obtain a modified xanthan gum product.

10. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 1, characterized in that: The preparation method of the high temperature resistant fluid loss reducer comprises the following steps: (1) First, 35-45 parts by weight of soluble starch and 100 parts by weight of deionized water were added to a flask, heated to 90° C. and stirred for 30 minutes to pregelatinize the starch until it became a transparent gelatinous state, thereby obtaining a pregelatinized starch solution; (2) 8-12 parts by weight of AM, 36-48 parts by weight of AMPS, 6-10 parts by weight of NVP, and 50 parts by weight of deionized water were added to another flask, and the pH value of the solution was adjusted to 6-7 with NaOH to obtain a monomer solution; (3) The monomer solution is added to the pregelatinized starch solution, nitrogen is introduced for 20 minutes, 0.05-0.1 parts by mass of sodium thiosulfate is added, the temperature is raised to 70-80°C, 0.6-1 parts by mass of potassium persulfate is added, the reaction is continued for 200-240 minutes, the reaction is stopped, the product is allowed to cool, the cooled product is washed with ethanol 2-3 times, and the white powder after drying and crushing is a high temperature resistant fluid loss reducer.

11. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 1, characterized in that: The heat-resistant plugging agent is prepared by drying a core-shell structure acrylic copolymer emulsion obtained by polymerizing methyl methacrylate (MMA), butyl acrylate (BA) and vinyltrimethoxysilane (A-171).

12. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 11, characterized in that: The preparation method of the heat-resistant plugging agent comprises the following steps: (1) adding 85 parts by mass of deionized water, 0.1-0.15 parts by mass of sodium ethoxyphenol ether sulfate and 0.1-0.15 parts by mass of nonylphenol polyoxyethylene ether into a three-necked flask, stirring and dissolving them uniformly; then slowly adding 18-23 parts by mass of methyl methacrylate (MMA) and 15-20 parts by mass of butyl acrylate (BA) monomer mixture into the three-necked flask, stirring and dissolving them uniformly, and obtaining a pre-emulsified shell monomer solution; (2) adding 15 parts by mass of deionized water, 0.2-0.3 parts by mass of sodium ethoxyphenol ether sulfate and 0.2-0.3 parts by mass of nonylphenol polyoxyethylene ether to a four-necked flask, stirring and dissolving them uniformly, then adding 3-5 parts by mass of methyl methacrylate (MMA), 2-4 parts by mass of butyl acrylate (BA), and 4-6 parts by mass of vinyltrimethoxysilane (A-171) monomers, stirring and mixing them uniformly, and emulsifying for 30-40 minutes, heating to 80-90° C., adding 0.2-0.3 parts by mass of 20% potassium persulfate, and after the emulsion shows a blue phase, keeping the temperature for reaction for 30 minutes to prepare a seed emulsion; (3) uniformly adding the shell monomer solution prepared in step (1) and 0.5-0.7 parts by mass of 20% potassium persulfate to the seed emulsion at 80-90° C., and adding equal amounts of sodium carbonate and sodium bicarbonate as pH regulators to adjust the pH to neutral; maintaining the reaction temperature, the system maintains a blue phase, and after the addition is completed, the temperature is kept for 30 minutes, and then cooled to 60-70° C., 0.04-0.06 parts by mass of tert-butyl hydroperoxide and 0.04-0.06 parts by mass of bleaching agent are added twice at intervals of 30 minutes to carry out residual monomer elimination reaction, stop the reaction, and let the product stand to cool. After the cooled product is washed with ethanol 2-3 times, the white powder obtained by drying and crushing is a heat-resistant plugging agent.

13. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 1, characterized in that: The temporary plugging agent is calcium carbonate powder; the particle size of the calcium carbonate powder is 200-800 meshes, and the acid solubility is greater than 96%.

14. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 1, characterized in that: The lubricant is one or more of modified vegetable oil lubricants, polyol fatty acid esters, silicone emulsions and polymeric alcohol lubricants.

15. The high temperature resistant weak gel anti-gas intrusion drilling fluid according to claim 1, characterized in that: The defoaming agent is a polyether defoaming agent or an organosilicon defoaming agent.

16. The method for preparing the high-temperature resistant weak gel anti-gas intrusion drilling fluid according to any one of claims 1 to 15, characterized in that: The following steps are involved: Add the formulated amount of tap water, formate and pH regulator to the high-stirring cup in sequence, and stir at high speed for 10 minutes; then add the viscosity enhancer and stir for 10 minutes; then add the high-temperature resistant flow pattern regulator and defoamer and stir at high speed for 10 minutes; then add the high-temperature resistant fluid loss reducer and the temperature-resistant plugging agent and stir at high speed for 10 minutes; then add the high-temperature stabilizer and stir at high speed for 10 minutes; then add the temporary plugging agent and stir at high speed for 10 minutes; then add the lubricant and stir at high speed for 10 minutes; then add the barite and stir at high speed for 20 minutes to obtain the high-temperature resistant weak gel anti-gas intrusion drilling fluid.

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