A solid-free kill fluid and a preparation method thereof

Abstract

This invention relates to the field of oil and gas drilling engineering technology, specifically to a solids-free kill fluid and its preparation method, comprising the following raw materials by weight: 80-100 parts base fluid, 25-35 parts composite additives, 8-12 parts soluble thickener, 6-10 parts liquid phase anti-collapse agent, and 3-5 parts lubricant. In this invention, a high-density system is constructed through additive A of the composite additives, breaking through the specific gravity limit of traditional salt-based weighting agents. Combined with the solubilizing and stabilizing effect of triethanolamine, high-concentration components are prevented from salting out, effectively solving the problem of limited specific gravity increase in traditional solids-free kill fluids. Simultaneously, additive B constructs a liquid-phase cross-linked colloidal network, increasing the system viscosity and forming a liquid plug, effectively blocking the exchange and dilution between the kill fluid and residual wastewater in the wellbore, preventing performance degradation of the kill fluid due to dilution, and reducing material waste caused by replenishing the kill fluid.

Description

Technical Field

[0001] This invention relates to the field of oil and gas drilling engineering technology, specifically to a solid-free well control fluid and its preparation method. Background Technology

[0002] In petroleum engineering, traditional solid-containing kill fluids are prone to damaging reservoirs. Existing solid-free kill fluids use soluble salts as weighting agents, combined with polymer additives, and have both adjustable density and high viscosity. They can prevent blowouts, protect reservoirs, reduce stuck drill bit risks, and are suitable for various complex working conditions, covering multiple operational scenarios.

[0003] In existing technologies, such as the solid-free kill fluid and its preparation method described in Chinese patent CN118931510A, a compound system of solubilizer, organic salt, and inorganic salt is used, exhibiting good high-temperature stability, low corrosivity, and minimal formation damage. However, existing solid-free kill fluids rely on salt weighting agents to improve their effectiveness, but the solubility of salts is limited, resulting in limited potential for increasing specific gravity and thus affecting the performance of the solid-free kill fluid. Therefore, this invention provides a solid-free kill fluid and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a solid-free kill fluid and its preparation method. The solid-free kill fluid prepared by this invention not only has a high specific gravity but also good viscosity, effectively improving the performance of the solid-free kill fluid.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a solid-free well control fluid comprising the following raw materials in parts by weight: 80-100 parts base fluid, 25-35 parts composite additives, 8-12 parts soluble thickener, 6-10 parts liquid phase anti-collapse agent, and 0.5-2 parts pH adjuster.

[0007] Further, the preparation method of the composite additive is as follows: the additive solution A, the additive solution B, the composite stabilizer and the aqueous solution of hydroxypropyl guanidine gum are mixed in a mass ratio of (15-20):(10-15):(4-6):(5-8) and stirred at 1200-1600 rpm for 20-30 min.

[0008] Furthermore, the base solution is prepared by mixing potassium chloride, calcium chloride, sodium bromide and deionized water in a mass ratio of (25-35):(15-20):(10-15):100.

[0009] Further, the preparation method of the additive solution A is as follows: a 40-50% formamide aqueous solution and a 30-40% ethylene glycol monobutyl ether solution are mixed at a volume ratio of 1:(2-3) to obtain a mixture. Then, 15-20% of the mixture mass of soluble tungstate is added, and the mixture is stirred at 50-60℃ and 500-700rpm for 30-50 minutes. Next, 8-12% of the mixture mass of soluble borate is added, and the mixture is stirred at 50-60℃ and 500-700rpm for 20-30 minutes. Finally, 3-5% of the mixture mass of triethanolamine is added to obtain additive solution A. The soluble tungstate is potassium tungstate, and the soluble borate is sodium tetraborate.

[0010] Further, the preparation method of the additive solution B is as follows: A 20-25% (w / w) aqueous solution of konjac glucomannan and a 15-20% (w / w) aqueous solution of sodium carboxymethyl cellulose are mixed at a volume ratio of 1:(3-4), and stirred at 60-70℃ and 600-800 rpm for 30-40 minutes to obtain a colloidal solution. A 30% (w / w) aqueous solution of acrylamide and a 5% (w / w) aqueous solution of N,N-methylenebisacrylamide are added to the colloidal solution, and the mixture is stirred at 60-70℃ and 600-800 rpm for a further [processing step]. Continue stirring for 10-20 minutes, add 10% (w / w) ammonium persulfate aqueous solution, continue stirring at 60-70℃ and 600-800 rpm for 5 minutes, then purge with nitrogen to remove oxygen for 10-20 minutes, finally raise the temperature to 65-75℃ and react for 2-3 hours to obtain additive solution B, wherein the volume of acrylamide aqueous solution is 8-12% of the volume of colloidal liquid, the volume of N,N-methylenebisacrylamide aqueous solution is 3-5% of the volume of colloidal liquid, and the mass of ammonium persulfate aqueous solution is 0.3-0.5% of the mass of colloidal liquid.

[0011] Further, the composite stabilizer is an aqueous solution with a mass fraction of 10-15% prepared by mixing sodium pyrophosphate, sodium citrate and disodium ethylenediaminetetraacetate and adding deionized water, wherein the mass ratio of sodium pyrophosphate, sodium citrate and disodium ethylenediaminetetraacetate is (4-6):(3-5):(2-3).

[0012] Furthermore, the mass fraction of the hydroxypropyl guanidine gum aqueous solution is 5-8%.

[0013] Furthermore, the soluble thickener is a xanthan gum aqueous solution with a mass fraction of 5-8%.

[0014] Furthermore, the liquid phase anti-collapse agent is a shale inhibitor complexed aluminum salt DLA-1 for drilling fluids.

[0015] Furthermore, the lubricant is a 10% by mass aqueous solution of polyether polyol.

[0016] Secondly, the present invention provides a method for preparing solids-free well-killing fluid, characterized by comprising the following steps:

[0017] (1) Mix the base fluid, soluble thickener, liquid phase anti-collapse agent and lubricant evenly, stir at 40-50℃ and 800rpm for 30-40min to obtain the basic kill fluid system;

[0018] (2) Add composite additives to the basic kill fluid system according to the mass ratio, stir at 35-45℃ and 800-1000rpm for 40-60min, and purge with nitrogen at a flow rate of 30-40mL / min throughout the process. Finally, adjust the pH of the system to 8-9 to obtain solid-free kill fluid.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. In this invention, a high-density soluble system is constructed by adding a composite additive solution A. The high molar mass of soluble tungstate and borate is compounded with a high-density liquid solvent, breaking through the specific gravity limit of traditional salt weighting agents. Combined with the solubilizing and stabilizing effect of triethanolamine, the salting out of high-concentration components is avoided. At the same time, the composite stabilizer and hydroxypropyl guar gum synergistically optimize the dispersibility, achieving a stable increase in specific gravity while ensuring the uniformity of the system, effectively solving the problem of limited specific gravity increase in traditional solid-free well control fluids.

[0021] 2. In this invention, a liquid-phase cross-linked colloidal network is constructed by adding the composite additive liquid B. Using konjac glucomannan and sodium carboxymethyl cellulose as the base material, a dense three-dimensional structure is formed by cross-linking polymerization with acrylamide, which enhances the viscosity of the system. Combined with the thickening synergistic effect of xanthan gum, the ability to carry cuttings and control filtration loss is improved, forming a liquid plug that effectively blocks the exchange and dilution between the kill fluid and the residual wastewater in the wellbore, avoiding performance degradation of the kill fluid due to dilution, and also reducing material waste caused by adding kill fluid. Attached Figure Description

[0022] Figure 1 The present invention provides a flowchart of a solid-free well control fluid and its preparation method. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that the raw materials used in the following embodiments are all commercially available.

[0025] Example 1:

[0026] (1) Preparation of base solution: potassium chloride, calcium chloride, sodium bromide and deionized water are mixed in a mass ratio of 25:15:10:100.

[0027] (2) Preparation of additive solution A: Mix 40% formamide aqueous solution and 30% ethylene glycol monobutyl ether solution at a volume ratio of 1:2 to obtain a mixture. Then add 15% soluble tungstate by mass of the mixture and stir at 50°C and 500 rpm for 30 min. Then add 8% soluble borate by mass of the mixture and continue stirring at 50°C and 500 rpm for 20 min. Finally, add 3% triethanolamine by mass of the mixture to obtain additive solution A. The soluble tungstate is potassium tungstate and the soluble borate is sodium tetraborate.

[0028] (3) Preparation of additive solution B: Mix 20% konjac glucomannan aqueous solution and 15% sodium carboxymethyl cellulose aqueous solution at a volume ratio of 1:3, stir at 60℃ and 600rpm for 30min to obtain a colloidal solution, add 30% acrylamide aqueous solution and 5% N,N-methylenebisacrylamide aqueous solution to the colloidal solution, continue stirring at 60℃ and 600rpm for 10min, add 10% ammonium persulfate aqueous solution, continue stirring at 60℃ and 600rpm for 5min, then purge with nitrogen for 10min, finally raise the temperature to 65℃ and react for 2h to obtain additive solution B, wherein the volume of acrylamide aqueous solution is 8% of the volume of colloidal solution, the volume of N,N-methylenebisacrylamide aqueous solution is 3% of the volume of colloidal solution, and the mass of ammonium persulfate aqueous solution is 0.3% of the mass of colloidal solution.

[0029] (4) Preparation of composite stabilizer: Sodium pyrophosphate, sodium citrate and disodium ethylenediaminetetraacetate are mixed in a mass ratio of 4:3:2 and then added to deionized water to prepare an aqueous solution with a mass fraction of 10% to obtain the composite stabilizer.

[0030] (5) Preparation of composite additive: Mix additive A, additive B, composite stabilizer and hydroxypropyl guar gum aqueous solution in a mass ratio of 15:10:4:5 and stir at 1200 rpm for 20 min to obtain composite additive, wherein the mass fraction of hydroxypropyl guar gum aqueous solution is 5%.

[0031] (6) Mix 80 parts of base fluid, 8 parts of soluble thickener, 6 parts of liquid phase anti-collapse agent and 3 parts of lubricating agent evenly, stir at 40℃ and 800rpm for 30min to obtain the basic kill fluid system. The soluble thickener is a xanthan gum aqueous solution with a mass fraction of 5%, the liquid phase anti-collapse agent is DLA-1 complex aluminum salt for drilling fluid shale inhibitor, and the lubricating agent is a polyether polyol aqueous solution with a mass fraction of 10%.

[0032] (7) Add 25 parts of composite additive to the basic kill fluid system, stir at 35°C and 800 rpm for 40 min, and purge with nitrogen at a flow rate of 30 mL / min throughout the process. Finally, adjust the pH of the system to 8 to obtain a solid-free kill fluid.

[0033] Example 2:

[0034] (1) Preparation of base solution: potassium chloride, calcium chloride, sodium bromide and deionized water are mixed in a mass ratio of 30:18:12:100.

[0035] (2) Preparation of additive solution A: Mix 45% formamide aqueous solution and 35% ethylene glycol monobutyl ether solution at a volume ratio of 1:2.5 to obtain a mixture. Then add 18% soluble tungstate by mass of the mixture and stir at 55°C and 600 rpm for 40 min. Then add 10% soluble borate by mass of the mixture and continue stirring at 55°C and 600 rpm for 25 min. Finally, add 4% triethanolamine by mass of the mixture to obtain additive solution A. The soluble tungstate is potassium tungstate and the soluble borate is sodium tetraborate.

[0036] (3) Preparation of additive solution B: Mix 22% konjac glucomannan aqueous solution and 18% sodium carboxymethyl cellulose aqueous solution at a volume ratio of 1:3.5, stir at 65℃ and 700rpm for 35min to obtain a colloidal solution, add 30% acrylamide aqueous solution and 5% N,N-methylenebisacrylamide aqueous solution to the colloidal solution, continue stirring at 65℃ and 700rpm for 15min, add 10% ammonium persulfate aqueous solution, continue stirring at 65℃ and 700rpm for 5min, then purge with nitrogen to remove oxygen for 15min, finally raise the temperature to 70℃ and react for 2.5h to obtain additive solution B, wherein the volume of acrylamide aqueous solution is 10% of the volume of colloidal solution, the volume of N,N-methylenebisacrylamide aqueous solution is 4% of the volume of colloidal solution, and the mass of ammonium persulfate aqueous solution is 0.4% of the mass of colloidal solution.

[0037] (4) Preparation of composite stabilizer: Sodium pyrophosphate, sodium citrate and disodium ethylenediaminetetraacetate are mixed in a mass ratio of 5:4:2.5 and then added to deionized water to prepare an aqueous solution with a mass fraction of 12% to obtain the composite stabilizer.

[0038] (5) Preparation of composite additive: Mix additive A, additive B, composite stabilizer and hydroxypropyl guar gum aqueous solution in a mass ratio of 18:12:5:6 and stir at 1400 rpm for 25 min to obtain composite additive, wherein the mass fraction of hydroxypropyl guar gum aqueous solution is 6%.

[0039] (6) Mix 90 parts of base fluid, 10 parts of soluble thickener, 8 parts of liquid phase anti-collapse agent and 4 parts of lubricating agent evenly, stir at 45℃ and 800rpm for 35min to obtain the basic kill fluid system. The soluble thickener is a xanthan gum aqueous solution with a mass fraction of 6%, the liquid phase anti-collapse agent is DLA-1 complex aluminum salt for drilling fluid shale inhibitor, and the lubricating agent is a polyether polyol aqueous solution with a mass fraction of 10%.

[0040] (7) Add 30 parts of composite additive to the basic kill fluid system, stir at 40°C and 900 rpm for 50 min, and purge with nitrogen at a flow rate of 35 mL / min throughout the process. Finally, adjust the pH of the system to 8.5 to obtain a solid-free kill fluid.

[0041] Example 3:

[0042] (1) Preparation of base solution: potassium chloride, calcium chloride, sodium bromide and deionized water are mixed in a mass ratio of 35:20:15:100.

[0043] (2) Preparation of additive solution A: Mix 50% formamide aqueous solution and 40% ethylene glycol monobutyl ether solution at a volume ratio of 1:3 to obtain a mixture. Then add 20% soluble tungstate by mass of the mixture and stir at 60°C and 700 rpm for 50 min. Then add 12% soluble borate by mass of the mixture and continue stirring at 60°C and 700 rpm for 30 min. Finally, add 5% triethanolamine by mass of the mixture to obtain additive solution A. The soluble tungstate is potassium tungstate and the soluble borate is sodium tetraborate.

[0044] (3) Preparation of additive solution B: Mix 25% konjac glucomannan aqueous solution and 20% sodium carboxymethyl cellulose aqueous solution at a volume ratio of 1:4, stir at 70℃ and 800rpm for 40min to obtain a colloidal solution, add 30% acrylamide aqueous solution and 5% N,N-methylenebisacrylamide aqueous solution to the colloidal solution, continue stirring at 70℃ and 800rpm for 20min, add 10% ammonium persulfate aqueous solution, continue stirring at 70℃ and 800rpm for 5min, then purge with nitrogen to remove oxygen for 20min, finally raise the temperature to 75℃ and react for 3h to obtain additive solution B, wherein the volume of acrylamide aqueous solution is 12% of the volume of colloidal solution, the volume of N,N-methylenebisacrylamide aqueous solution is 5% of the volume of colloidal solution, and the mass of ammonium persulfate aqueous solution is 0.5% of the mass of colloidal solution.

[0045] (4) Preparation of composite stabilizer: Sodium pyrophosphate, sodium citrate and disodium ethylenediaminetetraacetate are mixed in a mass ratio of 6:5:3 and then added to deionized water to prepare an aqueous solution with a mass fraction of 15% to obtain the composite stabilizer.

[0046] (5) Preparation of composite additive: Mix additive A, additive B, composite stabilizer and hydroxypropyl guar gum aqueous solution in a mass ratio of 20:15:6:8 and stir at 1600 rpm for 30 min to obtain composite additive, wherein the mass fraction of hydroxypropyl guar gum aqueous solution is 8%.

[0047] (6) Mix 100 parts of base fluid, 12 parts of soluble thickener, 10 parts of liquid phase anti-collapse agent and 5 parts of lubricating agent evenly, stir at 50℃ and 800rpm for 40min to obtain the basic kill fluid system. The soluble thickener is an aqueous solution of xanthan gum with a mass fraction of 8%, the liquid phase anti-collapse agent is DLA-1 complex aluminum salt for drilling fluid shale inhibitor, and the lubricating agent is an aqueous solution of polyether polyol with a mass fraction of 10%.

[0048] (7) Add 35 parts of composite additive to the basic kill fluid system, stir at 45°C and 1000 rpm for 60 min, and purge with nitrogen at a flow rate of 40 mL / min throughout the process. Finally, adjust the pH of the system to 9 to obtain a solid-free kill fluid.

[0049] Comparative Example 1: The difference between this comparative example and Example 1 is that this comparative example does not contain any compound additives.

[0050] Comparative Example 2 differs from Example 1 in that additive solution A was not added during the preparation of the composite additive in this comparative example.

[0051] Comparative Example 3 differs from Example 1 in that additive solution B was not added during the preparation of the composite additive in this comparative example.

[0052] Performance testing: The solid-free kill fluids prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance testing, and the test data are recorded in the table below:

[0053] Table 1

[0054]

[0055] In the performance testing, the specific gravity and viscosity tests were conducted in accordance with Q SY XJ 0641-2014_GC.

[0056] The specific gravity test results of the solid-free kill fluids prepared in Examples 1-3 and Comparative Examples 1-3 were 1.92 g / cm³, 2.05 g / cm³, 2.11 g / cm³, 1.23 g / cm³, 1.47 g / cm³, and 1.78 g / cm³, respectively.

[0057] The viscosity test results of the solid-free kill fluids prepared in Examples 1-3 and Comparative Examples 1-3 were 59 mPa·s, 63 mPa·s, 68 mPa·s, 28 mPa·s, 49 mPa·s, and 37 mPa·s, respectively.

[0058] As can be seen from the comparison:

[0059] In the composite additive, additive A, with its high molar mass soluble salts potassium tungstate and sodium tetraborate, is combined with high-density liquid phase solvents formamide and ethylene glycol monobutyl ether. This increases the upper limit of the specific gravity of traditional salts while the solubilizing and dispersing effects of triethanolamine effectively prevent salting out and crystallizing of high-concentration soluble components, ensuring a stable high-specific-gravity system. Additive B, based on konjac glucomannan and sodium carboxymethyl cellulose, forms a dense colloid through the polymerization reaction of acrylamide and crosslinking agent. This effectively enhances the cohesion of the system and increases viscosity. This high-viscosity system can form a liquid plug effect, preventing the kill fluid from being exchanged and diluted with residual wastewater in the wellbore. This avoids performance degradation of the kill fluid due to dilution and waste caused by additional usage. At the same time, this colloidal network has excellent compatibility with the high-specific-gravity components of additive A, preventing viscosity decay. Combined with the synergistic dispersing effect of composite stabilizers and hydroxypropyl guar gum, it promotes the formation of a stable interfacial bond between the components in the liquid phase system, ultimately increasing the specific gravity and viscosity of the system.

[0060] In Comparative Example 1, there was no composite additive, so it lacked both the specific gravity-boosting effect of additive A and the viscosity-enhancing effect of additive B. Relying solely on the basic properties of the base liquid and a single thickener, both the specific gravity and viscosity were significantly reduced. In Comparative Example 2, there was no additive A, so the synergistic weight-boosting effect of high molar mass soluble salt and high density solvent was missing. Relying solely on the base liquid salt, the specific gravity-boosting effect was limited. In Comparative Example 3, there was no additive B, so no reaction to form a dense colloidal network occurred. Relying solely on the thickening effect of xanthan gum, high viscosity could not be achieved, leading to performance fluctuations and increased material waste.

[0061] By comparing and analyzing the relevant data in the table, it can be seen that the solid-free kill fluid prepared by this invention not only has a high specific gravity but also good viscosity. This indicates that the specific gravity and viscosity of the solid-free kill fluids prepared in Comparative Examples 1-3 provided by this invention are lower than those in Examples 1-3, suggesting that the solid-free kill fluid proposed in this invention has a broader market prospect and is more suitable for promotion.

[0062] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A solids-free well-killing fluid, characterized in that, It includes the following raw materials by weight: 80-100 parts base liquid, 25-35 parts compound additives, 8-12 parts soluble thickener, 6-10 parts liquid phase anti-collapse agent, and 3-5 parts lubricant; The raw materials for the base liquid include potassium chloride, calcium chloride, sodium bromide and deionized water; The soluble thickener is a xanthan gum aqueous solution; The liquid phase anti-collapse agent is the drilling fluid shale inhibitor complexed aluminum salt DLA-1; The lubricating agent is selected from an aqueous solution of polyether polyol. The preparation method of the composite additive is as follows: mix the additive A, additive B, composite stabilizer and hydroxypropyl guanidine gum aqueous solution in a mass ratio of (15-20):(10-15):(4-6):(5-8) and stir at 1200-1600 rpm for 20-30 min; The raw materials for additive solution A include formamide aqueous solution, ethylene glycol monobutyl ether solution, soluble tungstate, soluble borate and triethanolamine; The preparation method of the additive solution A is as follows: a 40-50% formamide aqueous solution and a 30-40% ethylene glycol monobutyl ether solution are mixed at a volume ratio of 1:(2-3) to obtain a mixture. Then, 15-20% of soluble tungstate is added to the mixture, and the mixture is stirred at 50-60℃ and 500-700rpm for 30-50 minutes. Next, 8-12% of soluble borate is added to the mixture, and the mixture is stirred at 50-60℃ and 500-700rpm for 20-30 minutes. Finally, 3-5% of triethanolamine is added to the mixture to obtain additive solution A. The soluble tungstate is potassium tungstate, and the soluble borate is sodium tetraborate. The raw materials for additive solution B include konjac glucomannan aqueous solution, sodium carboxymethyl cellulose aqueous solution, acrylamide aqueous solution, N,N-methylenebisacrylamide aqueous solution and ammonium persulfate aqueous solution; The preparation method of the additive solution B is as follows: A 20-25% (w / w) aqueous solution of konjac glucomannan and a 15-20% (w / w) aqueous solution of sodium carboxymethyl cellulose are mixed at a volume ratio of 1:(3-4), and stirred at 60-70℃ and 600-800 rpm for 30-40 minutes to obtain a colloidal solution. A 30% (w / w) aqueous solution of acrylamide and a 5% (w / w) aqueous solution of N,N-methylenebisacrylamide are added to the colloidal solution, and stirring is continued at 60-70℃ and 600-800 rpm. Stir for 10-20 minutes, add 10% (w / w) ammonium persulfate aqueous solution, continue stirring at 60-70℃ and 600-800 rpm for 5 minutes, then purge with nitrogen to remove oxygen for 10-20 minutes. Finally, raise the temperature to 65-75℃ and react for 2-3 hours to obtain additive solution B, in which the volume of acrylamide aqueous solution is 8-12% of the volume of colloidal liquid, the volume of N,N-methylenebisacrylamide aqueous solution is 3-5% of the volume of colloidal liquid, and the mass of ammonium persulfate aqueous solution is 0.3-0.5% of the mass of colloidal liquid. The raw materials for the composite stabilizer include sodium pyrophosphate, sodium citrate, disodium ethylenediaminetetraacetate, and deionized water.

2. The solids-free kill fluid according to claim 1, characterized in that, The base solution is prepared by mixing potassium chloride, calcium chloride, sodium bromide and deionized water in a mass ratio of (25-35):(15-20):(10-15):

100.

3. The solid-free kill fluid according to claim 1, characterized in that, The composite stabilizer is an aqueous solution with a mass fraction of 10-15% prepared by mixing sodium pyrophosphate, sodium citrate and disodium ethylenediaminetetraacetate and adding deionized water, wherein the mass ratio of sodium pyrophosphate, sodium citrate and disodium ethylenediaminetetraacetate is (4-6):(3-5):(2-3).

4. The solid-free kill fluid according to claim 1, characterized in that, The mass fraction of the hydroxypropyl guanidine gum aqueous solution is 5-8%.

5. The solid-free kill fluid according to claim 1, characterized in that, The soluble thickener is a xanthan gum aqueous solution with a mass fraction of 5-8%.

6. The solid-free kill fluid according to claim 1, characterized in that, The lubricant is a 10% (w / w) aqueous solution of polyether polyol.

7. The method for preparing solid-free kill fluid according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Mix the base fluid, soluble thickener, liquid phase anti-collapse agent and lubricant evenly, stir at 40-50℃ and 800rpm for 30-40min to obtain the basic kill fluid system; (2) Add composite additives to the basic kill fluid system according to the mass ratio, stir at 35-45℃ and 800-1000rpm for 40-60min, and purge with nitrogen at a flow rate of 30-40mL / min throughout the process. Finally, adjust the pH of the system to 8-9 to obtain solid-free kill fluid.

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