High-temperature-resistant low-damage high-density solid-free kill fluid and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant low-damage high-density solid-free well killing fluid which comprises 50-80 parts of water, 10-40 parts of calcium chloride, 10-40 parts of calcium bromide, 0.5-2 parts of a temperature-resistant tackifier, 1-3 parts of a temperature-resistant filtrate reducer, 0.5-2 parts of a high-temperature stabilizer, 0.5-3 parts of a high-temperature corrosion inhibitor, 0.5-2 parts of a salt crystallization inhibitor and 0.1-1 part of a waterproof locking agent. The technical problems that the saline water base fluid is unstable in density in a high-temperature environment, a reservoir is damaged, and a shaft is corroded are solved. The invention also discloses a preparation method of the high-temperature-resistant low-damage high-density solid-free kill fluid, which comprises the following steps: adding the water into a stirring kettle, then adding the calcium chloride, the temperature-resistant filtrate reducer, the temperature-resistant tackifier and the high-temperature corrosion inhibitor, uniformly stirring, and supplementing the calcium bromide during stirring to obtain a mixture; a salt crystallization inhibitor is injected into the stirring kettle, meanwhile, a high-temperature stabilizer is added, the stirring kettle is heated for full stirring, and the well killing fluid is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemistry and well repairing operations, and specifically relates to a high-temperature resistant, low-damage, high-density, solid-free well-killing fluid, and also relates to a preparation method of the high-temperature resistant, low-damage, high-density, solid-free well-killing fluid. Background Art

[0002] In the process of oil and gas field exploitation, well killing is mainly to prevent the formation fluid from flowing into the wellbore due to the pressure generated by the liquid in the wellbore, such as the well killing fluid, being lower than the pressure generated by the fluid in the formation during the well repair construction, causing dangerous accidents such as well kicks or blowouts. In recent years, my country's oil and gas development has gradually shifted from conventional oil and gas to deep wells and ultra-deep wells. During deep well drilling, the downhole temperature is high and the wellbore structure is complex. Conventional solid-phase well killing fluids in complex environments are difficult to meet the needs of well killing and will block the pore channels of the formation, reduce the formation permeability, and make the operation difficult, resulting in no increase in crude oil production. In severe cases, it will cause blowouts and cause huge economic and environmental losses. The application of solid-free well killing fluids at home and abroad is quite significant. There are also various well killing fluid formulas optimized for different reservoir conditions. The excellent performance of well killing fluids determines the production of oil and gas layers, so the optimization of well killing fluid systems is crucial. At present, the commonly used solid-free well killing fluids are mostly organic or inorganic brine-based fluids. These two types of brine-based fluids will have problems such as unstable density, damage to reservoirs, and corrosion of wellbores under high temperature environments. Considering the current situation that there are few high-temperature resistant, low-damage, solid-free well-killing fluid systems on the market, it is urgent to develop a high-temperature resistant, low-damage, high-density, solid-free well-killing fluid system. Summary of the invention

[0003] The first purpose of the present invention is to provide a high-temperature resistant, low-damage, high-density, solid-free well-killing fluid, which solves the technical problems in the prior art that the density of salt water-based fluids is unstable under high temperature environments and damages reservoirs and corrodes wellbores.

[0004] The second object of the present invention is to provide a method for preparing a high-temperature resistant, low-damage, high-density, solid-free well-killing fluid.

[0005] The first technical solution adopted by the present invention is that the high-temperature resistant, low-damage, high-density, solid-free well-killing fluid includes the following components by weight: 50-80 parts of water, 10-40 parts of calcium chloride, 10-40 parts of calcium bromide, 0.5-2 parts of temperature-resistant viscosity enhancer, 1-3 parts of temperature-resistant filtration reducer, 0.5-2 parts of high-temperature stabilizer, 0.5-3 parts of high-temperature corrosion inhibitor, 0.5-2 parts of salt crystallization inhibitor and 0.1-1 parts of waterproof lock agent.

[0006] The second technical solution adopted by the present invention is a method for preparing a high-temperature resistant, low-damage, high-density, solid-free well killing fluid, which is specifically implemented according to the following steps:

[0007] Step 1, adding 50 to 80 parts of water into a stirring tank, then adding 10 to 40 parts of calcium chloride, 1 to 3 parts of temperature-resistant fluid loss reducer, 0.5 to 2 parts of temperature-resistant viscosity enhancer and 0.5 to 3 parts of high-temperature corrosion inhibitor and stirring evenly, and adding 10 to 40 parts of calcium bromide during stirring to obtain a mixture;

[0008] Step 2, inject 0.5 to 2 parts of salt crystallization inhibitor into the stirring tank, add 0.5 to 2 parts of high temperature stabilizer at the same time, heat the stirring tank and stir it thoroughly, and then obtain a well killing fluid with a density of 1.4 g / cm3 to 1.6 g / cm3.

[0009] The second technical solution of the present invention is also characterized in that:

[0010] In step 2, the heating temperature of the stirring tank is 55° C. to 70° C., and the stirring time is 20 min to 35 min.

[0011] The water is deionized water from which impurities in the form of ions have been removed.

[0012] The temperature-resistant viscosity increasing agent is PAC-HV or XC.

[0013] The temperature-resistant fluid loss reducer is starch FLO-HT.

[0014] The high temperature stabilizer is sodium sulfite.

[0015] The high temperature corrosion inhibitor is a quaternary ammonium salt of bisimidazolyl.

[0016] The salt crystallization inhibitor was PF-NTA-1.

[0017] The waterproof lock agent is hexadecyltrimethylammonium chloride.

[0018] The beneficial effects of the present invention are:

[0019] The high-temperature resistant, low-damage, high-density, solid-free well-killing fluid prepared by the preparation method of the high-temperature resistant, low-damage, high-density, solid-free well-killing fluid of the present invention uses CaBr2-CaCl2 composite brine as the base fluid, and the density of the well-killing fluid can be adjusted within the range of 1.4g / cm3-1.6g / cm3. In the process of preparing the well-killing fluid, a treatment agent with temperature resistance is preferably selected, and the preferred treatment agent still maintains stable performance under a high-temperature environment of 150°C. The well-killing fluid constructed by the present invention has low damage and weak corrosion, and can effectively reduce damage to the reservoir and corrosion of the wellbore. At the same time, the well-killing fluid has good stability in a high-temperature formation environment and good compatibility with formation water. The present invention can meet the demand for well killing in the process of oil and gas field exploitation, and its application cost is low and the use effect is good. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0021] Example 1

[0022] The embodiment of the present invention provides a high-temperature resistant, low-damage, high-density, solid-free well-killing fluid with a density of 1.4 g / cm3, comprising the following substances in parts by weight: 60 parts of water, 35 parts of calcium chloride, 0.5 parts of a temperature-resistant viscosity enhancer, 1 part of a temperature-resistant fluid loss reducer, 0.5 parts of a high-temperature stabilizer, 0.5 parts of a high-temperature corrosion inhibitor, 1 part of a salt crystallization inhibitor, and 0.5 parts of a waterproof lock agent;

[0023] Among the above raw materials, water is deionized water from which ionized impurities are removed. The temperature-resistant viscosity enhancer is PAC-HV, the temperature-resistant fluid loss reducer is starch FLO-HT, the high-temperature stabilizer is sodium sulfite, the high-temperature corrosion inhibitor is diimidazole quaternary ammonium salt, the salt crystallization inhibitor is PF-NTA-1, and the waterproof lock agent is hexadecyl trimethyl ammonium chloride.

[0024] The embodiment of the present invention also provides a method for preparing the high temperature resistant, low damage, high density, solid-free well killing fluid, which is specifically implemented according to the following steps:

[0025] Step 1, after preparing the raw materials according to weight parts, add water into a stirring tank, and then add calcium chloride, temperature-resistant filtrate reducer FLO-HT, temperature-resistant viscosity enhancer XC and high-temperature corrosion inhibitor bisimidazolyl quaternary ammonium salt and stir evenly to obtain a mixture;

[0026] Step 2, injecting the salt crystallization inhibitor PF-NTA-1 into the stirring tank, adding the high temperature stabilizer sodium citrate at the same time, heating the stirring tank for sufficient stirring, and then obtaining the finished well killing fluid;

[0027] Step 3, placing the finished well killing fluid into a sealed barrel for packaging and storage.

[0028] Preferably, in step 2, the heating temperature of the stirring tank is controlled at 55-70° C., and the stirring time is 20-35 min.

[0029] Example 2

[0030] The embodiment of the present invention provides a high-temperature resistant, low-damage, high-density, solid-free well-killing fluid with a density of 1.5 g / cm3, comprising the following substances in parts by weight: 50 parts of water, 35 parts of calcium chloride, 10 parts of calcium bromide, 0.5 parts of a temperature-resistant viscosity enhancer, 1 part of a temperature-resistant fluid loss reducer, 0.5 parts of a high-temperature stabilizer, 0.5 parts of a high-temperature corrosion inhibitor, 1 part of a salt crystallization inhibitor, and 0.5 parts of a waterproof lock agent;

[0031] Among the above raw materials, water is deionized water from which ionized impurities are removed. The temperature-resistant viscosity enhancer is XC, the temperature-resistant fluid loss reducer is starch FLO-HT, the high-temperature stabilizer is sodium sulfite, the high-temperature corrosion inhibitor is bisimidazolyl quaternary ammonium salt, the salt crystallization inhibitor is PF-NTA-1, and the waterproof lock agent is hexadecyltrimethylammonium chloride.

[0032] The embodiment of the present invention also provides a method for preparing the high temperature resistant, low damage, high density, solid-free well killing fluid, which is specifically implemented according to the following steps:

[0033] Step 1, after preparing the raw materials according to weight parts, add water into a stirring tank, then add calcium chloride, temperature-resistant filtrate reducer FLO-HT, temperature-resistant viscosity enhancer PAC-HV and high-temperature corrosion inhibitor bisimidazolyl quaternary ammonium salt and stir evenly, during which calcium bromide is added to obtain a mixture;

[0034] Step 2, injecting the salt crystallization inhibitor PF-NTA-1 into the stirring tank, adding the high temperature stabilizer sodium citrate at the same time, heating the stirring tank for sufficient stirring, and then obtaining the finished well killing fluid;

[0035] Step 3, placing the finished well killing fluid into a sealed barrel for packaging and storage.

[0036] Preferably, in step 2, the heating temperature of the stirring tank is controlled at 55-70° C., and the stirring time is 20-35 min.

[0037] Example 3

[0038] The embodiment of the present invention provides a high-temperature resistant, low-damage, high-density, solid-free well-killing fluid with a density of 1.6 g / cm3, comprising the following substances in parts by weight: 50 parts of water, 25 parts of calcium chloride, 20 parts of calcium bromide, 0.5 parts of a temperature-resistant viscosity enhancer, 1 part of a temperature-resistant fluid loss reducer, 0.5 parts of a high-temperature stabilizer, 0.5 parts of a high-temperature corrosion inhibitor, 1 part of a salt crystallization inhibitor, and 0.5 parts of a waterproof lock agent;

[0039] Among the above raw materials, water is deionized water from which ionized impurities are removed. The temperature-resistant viscosity enhancer is XC, the temperature-resistant fluid loss reducer is starch FLO-HT, the high-temperature stabilizer is sodium sulfite, the high-temperature corrosion inhibitor is bisimidazolyl quaternary ammonium salt, the salt crystallization inhibitor is PF-NTA-1, and the waterproof lock agent is hexadecyltrimethylammonium chloride.

[0040] The embodiment of the present invention also provides a method for preparing the high temperature resistant, low damage, high density, solid-free well killing fluid, which is specifically implemented according to the following steps:

[0041] Step 1, after preparing the raw materials according to weight parts, add water into a stirring tank, then add calcium chloride, temperature-resistant filtrate reducer FLO-HT, temperature-resistant viscosity enhancer XC and high-temperature corrosion inhibitor bisimidazolyl quaternary ammonium salt and stir evenly, during which calcium bromide is added to obtain a mixture;

[0042] Step 2, injecting the salt crystallization inhibitor PF-NTA-1 into the stirring tank, adding the high temperature stabilizer sodium citrate at the same time, heating the stirring tank for sufficient stirring, and then obtaining the finished well killing fluid;

[0043] Step 3, placing the finished well killing fluid into a sealed barrel for packaging and storage.

[0044] Preferably, in step 2, the heating temperature of the stirring tank is controlled at 55-70° C., and the stirring time is 20-35 min.

[0045] Example 4

[0046] The embodiment of the present invention provides a high-temperature resistant, low-damage, high-density, solid-free well killing fluid, comprising the following substances in parts by weight: 50 parts of water, 10 parts of calcium chloride, 0.5 parts of a temperature-resistant viscosity enhancer, 1 part of a temperature-resistant fluid loss reducer, 0.5 parts of a high-temperature stabilizer, 0.5 parts of a high-temperature corrosion inhibitor, 0.5 parts of a salt crystallization inhibitor, and 0.1 parts of a waterproof lock agent;

[0047] Among the above raw materials, water is deionized water from which ionized impurities are removed. The temperature-resistant viscosity enhancer is PAC-HV, the temperature-resistant fluid loss reducer is starch FLO-HT, the high-temperature stabilizer is sodium sulfite, the high-temperature corrosion inhibitor is diimidazole quaternary ammonium salt, the salt crystallization inhibitor is PF-NTA-1, and the waterproof lock agent is hexadecyl trimethyl ammonium chloride.

[0048] The embodiment of the present invention also provides a method for preparing the high temperature resistant, low damage, high density, solid-free well killing fluid, which is specifically implemented according to the following steps:

[0049] Step 1, after preparing the raw materials according to weight parts, add water into a stirring tank, and then add calcium chloride, temperature-resistant filtrate reducer FLO-HT, temperature-resistant viscosity enhancer XC and high-temperature corrosion inhibitor bisimidazolyl quaternary ammonium salt and stir evenly to obtain a mixture;

[0050] Step 2, injecting the salt crystallization inhibitor PF-NTA-1 into the stirring tank, adding the high temperature stabilizer sodium citrate at the same time, heating the stirring tank for sufficient stirring, and then obtaining the finished well killing fluid;

[0051] Step 3, placing the finished well killing fluid into a sealed barrel for packaging and storage.

[0052] Preferably, in step 2, the heating temperature of the stirring tank is controlled at 55° C., and the stirring time is 20 min.

[0053] Example 5

[0054] The embodiment of the present invention provides a high-temperature resistant, low-damage, high-density, solid-free well killing fluid, comprising the following substances in parts by weight: 65 parts of water, 25 parts of calcium chloride, 1.25 parts of a temperature-resistant viscosity enhancer, 2 parts of a temperature-resistant fluid loss reducer, 1.25 parts of a high-temperature stabilizer, 1.7 parts of a high-temperature corrosion inhibitor, 1.25 parts of a salt crystallization inhibitor, and 0.5 parts of a waterproof lock agent;

[0055] Among the above raw materials, water is deionized water from which ionized impurities are removed. The temperature-resistant viscosity enhancer is PAC-HV, the temperature-resistant fluid loss reducer is starch FLO-HT, the high-temperature stabilizer is sodium sulfite, the high-temperature corrosion inhibitor is diimidazole quaternary ammonium salt, the salt crystallization inhibitor is PF-NTA-1, and the waterproof lock agent is hexadecyl trimethyl ammonium chloride.

[0056] The embodiment of the present invention also provides a method for preparing the high temperature resistant, low damage, high density, solid-free well killing fluid, which is specifically implemented according to the following steps:

[0057] Step 1, after preparing the raw materials according to weight parts, add water into a stirring tank, and then add calcium chloride, temperature-resistant filtrate reducer FLO-HT, temperature-resistant viscosity enhancer XC and high-temperature corrosion inhibitor bisimidazolyl quaternary ammonium salt and stir evenly to obtain a mixture;

[0058] Step 2, injecting the salt crystallization inhibitor PF-NTA-1 into the stirring tank, adding the high temperature stabilizer sodium citrate at the same time, heating the stirring tank for sufficient stirring, and then obtaining the finished well killing fluid;

[0059] Step 3, placing the finished well killing fluid into a sealed barrel for packaging and storage.

[0060] Preferably, in step 2, the heating temperature of the stirring tank is controlled at 62° C., and the stirring time is 27 min.

[0061] Example 6

[0062] The embodiment of the present invention provides a high-temperature resistant, low-damage, high-density, solid-free well killing fluid, comprising the following substances in parts by weight: 80 parts of water, 40 parts of calcium chloride, 2 parts of a temperature-resistant viscosity enhancer, 3 parts of a temperature-resistant fluid loss reducer, 2 parts of a high-temperature stabilizer, 3 parts of a high-temperature corrosion inhibitor, 2 parts of a salt crystallization inhibitor, and 1 part of a waterproof lock agent;

[0063] Among the above raw materials, water is deionized water from which ionized impurities are removed. The temperature-resistant viscosity enhancer is PAC-HV, the temperature-resistant fluid loss reducer is starch FLO-HT, the high-temperature stabilizer is sodium sulfite, the high-temperature corrosion inhibitor is diimidazole quaternary ammonium salt, the salt crystallization inhibitor is PF-NTA-1, and the waterproof lock agent is hexadecyl trimethyl ammonium chloride.

[0064] The embodiment of the present invention also provides a method for preparing the high temperature resistant, low damage, high density, solid-free well killing fluid, which is specifically implemented according to the following steps:

[0065] Step 1, after preparing the raw materials according to weight parts, add water into a stirring tank, and then add calcium chloride, temperature-resistant filtrate reducer FLO-HT, temperature-resistant viscosity enhancer XC and high-temperature corrosion inhibitor bisimidazolyl quaternary ammonium salt and stir evenly to obtain a mixture;

[0066] Step 2, injecting the salt crystallization inhibitor PF-NTA-1 into the stirring tank, adding the high temperature stabilizer sodium citrate at the same time, heating the stirring tank for sufficient stirring, and then obtaining the finished well killing fluid;

[0067] Step 3, placing the finished well killing fluid into a sealed barrel for packaging and storage.

[0068] Preferably, in step 2, the heating temperature of the stirring tank is controlled at 70° C., and the stirring time is 35 min.

[0069] The density of the well-killing fluid obtained in Examples 4-6 is in the range of 1.4 g / cm3 to 1.6 g / cm3.

[0070] The density of the well-killing fluid prepared by the present invention is adjustable within the range of 1.4g / cm3-1.6g / cm3, the damage to the reservoir and the wellbore meets the industry requirements and can withstand a high temperature of 150°C, it has good compatibility with formation water, and no crystals are generated after 57 days of static. The prepared well-killing fluid can meet the requirements of underground pressure control operations with a well depth of more than 2000m.

[0071] Comparative Example 1

[0072] The comparative example of the present invention provides a conventional solid-free salt water well-killing fluid with a density of 1.4 g / cm3, comprising the following substances in parts by weight: 62 parts of water, 38 parts of calcium chloride;

[0073] Among the above raw materials, water is deionized water from which impurities in the form of ions have been removed.

[0074] Step 1, after preparing the raw materials according to weight parts, water is added into a stirring tank, and then calcium chloride is added to obtain a mixture;

[0075] Step 2, heating the stirring kettle to fully stir, and then obtaining a finished well killing fluid;

[0076] Step 3, placing the finished well killing fluid into a sealed barrel for packaging and storage.

[0077] Preferably, in step 2, the heating temperature of the stirring tank is controlled at 55-70° C., and the stirring time is 20-35 min.

[0078] Comparative Example 2

[0079] The comparative example of the present invention provides a high-density solid-free well-killing fluid with a density of 1.5 g / cm3, which is resistant to high temperature and low in damage, and includes the following substances in parts by weight: 53 parts of water, 37 parts of calcium chloride, and 10 parts of calcium bromide.

[0080] Among the above raw materials, water is deionized water from which impurities in the form of ions have been removed.

[0081] Step 1, after preparing the raw materials according to weight parts, add water into a stirring tank, then add calcium chloride and stir evenly, during which calcium bromide is added to obtain a mixture;

[0082] Step 2, heating the stirring kettle to fully stir, and then obtaining a finished well killing fluid;

[0083] Step 3, placing the finished well killing fluid into a sealed barrel for packaging and storage.

[0084] Preferably, in step 2, the heating temperature of the stirring tank is controlled at 55-70° C., and the stirring time is 20-35 min.

[0085] Comparative Example 3

[0086] The comparative example of the present invention provides a high-temperature-resistant, low-damage, high-density, solid-free well-killing fluid with a density of 1.6 g / cm3, comprising the following substances in parts by weight: 53 parts of water, 26 parts of calcium chloride, and 21 parts of calcium bromide;

[0087] Among the above raw materials, water is deionized water from which impurities in the form of ions have been removed.

[0088] Step 1, after preparing the raw materials according to weight parts, add water into a stirring tank, then add calcium chloride and stir evenly, during which calcium bromide is added to obtain a mixture;

[0089] Step 2, heating the stirring kettle to fully stir, and then obtaining a finished well killing fluid;

[0090] Step 3, placing the finished well killing fluid into a sealed barrel for packaging and storage.

[0091] Preferably, in step 2, the heating temperature of the stirring tank is controlled at 55-70° C., and the stirring time is 20-35 min.

[0092] In combination with Examples 1-3 and Comparative Examples 1-3, the performance of the well killing fluid prepared above was tested, and the specific test items and test data are as follows:

[0093] The first item, corrosion degree test: The high temperature and high pressure corrosion performance test at a temperature of 150° C. was performed on the well killing fluids of Examples 1-3 and Comparative Examples 1-3 by the hanging plate weight loss method. The corrosion performance test results are shown in Table 1.

[0094] Table 1

[0095] Serial number Corrosion rate (mm·a-1) Example 1 0.0114 Example 2 0.0112 Example 3 0.0128 Comparative Example 1 2.7651 Comparative Example 2 3.0245 Comparative Example 3 3.7221

[0096] Second item, static shear force evaluation: The well killing fluids of Examples 1-3 and Comparative Examples 1-3 were placed in a rotational viscometer after aging at 150°C / 16h to measure their static shear forces. The rheological properties test results are shown in Table 2.

[0097] Table 2

[0098]

[0099]

[0100] The third project, reservoir protection performance evaluation: the killing fluids of Examples 1-3 and Comparative Examples 1-3 were passed through the YBH-1 reservoir protection tester, and 6 cores were selected to test the permeability values ​​before and after the killing fluid contamination, and the reservoir protection performance of different completion fluid systems was evaluated. The reservoir protection performance test results are shown in Table 3.

[0101] Table 3

[0102]

[0103]

[0104] Fourth item, fluid loss test: The killing fluids of Examples 1-3 and Comparative Examples 1-3 were hot-rolled for 16 hours at 150°C, and then their API fluid loss at room temperature and HTHP fluid loss at 150°C and 3.5 MPa were measured. The fluid loss performance test results are shown in Table 4.

[0105] Table 4

[0106] Serial number API filtration loss / mL HTHP filtration loss / mL Example 1 0 8.5 Example 2 0 8.1 Example 3 0 8.2 Comparative Example 1 117 Total filtration loss Comparative Example 2 120 Total filtration loss Comparative Example 3 109 Total filtration loss

[0107] Fifth item, compatibility performance evaluation: In order to prevent the well-killing fluid system from reacting with formation water to produce precipitation and block pores after entering the reservoir, it is necessary to evaluate the compatibility of the well-killing fluid and formation water. The well-killing fluids of Examples 1-3 and Comparative Examples 1-3 were mixed with simulated formation water at a ratio of 1:1, and the compatibility was observed after standing for 2 hours. The compatibility performance test results are shown in Table 5.

[0108] Table 5

[0109] Serial number Mixing ratio / (V / V) Experimental phenomenon in conclusion Example 1 1：1 No precipitation Combination Example 2 1：1 No precipitation Combination Example 3 1：1 No precipitation Combination Comparative Example 1 1：1 White precipitate Incompatible Comparative Example 2 1：1 White precipitate Incompatible Comparative Example 3 1：1 White precipitate Incompatible

[0110] It can be seen from Tables 1 to 5 that the well-killing fluid prepared by the method for preparing the high-temperature resistant, low-damage, high-density, solid-free well-killing fluid of the present invention has a low corrosion rate, strong rheological properties, high permeability recovery value, small filtration loss and good compatibility compared with the prior art.

[0111] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. High temperature resistant, low damage, high density, solid-free well killing fluid, characterized by: In terms of weight proportions, the composition includes: 50-80 parts of water, 10-40 parts of calcium chloride, 10-40 parts of calcium bromide, 0.5-2 parts of temperature-resistant viscosity enhancer, 1-3 parts of temperature-resistant filtration reducer, 0.5-2 parts of high-temperature stabilizer, 0.5-3 parts of high-temperature corrosion inhibitor, 0.5-2 parts of salt crystallization inhibitor and 0.1-1 parts of waterproof lock agent.

2. A method for preparing a high-temperature resistant, low-damage, high-density, solid-free well-killing fluid, characterized in that: Follow the steps below to implement it: Step 1, adding 50 to 80 parts of water into a stirring tank, then adding 10 to 40 parts of calcium chloride, 1 to 3 parts of temperature-resistant fluid loss reducer, 0.5 to 2 parts of temperature-resistant viscosity enhancer and 0.5 to 3 parts of high-temperature corrosion inhibitor and stirring evenly, and adding 10 to 40 parts of calcium bromide during stirring to obtain a mixture; Step 2, inject 0.5 to 2 parts of salt crystallization inhibitor into the stirring tank, add 0.5 to 2 parts of high temperature stabilizer at the same time, heat the stirring tank and stir it thoroughly, and then obtain a well killing fluid with a density of 1.4 g / cm3 to 1.6 g / cm3.

3. The method for preparing a high-temperature resistant, low-damage, high-density, solid-free well killing fluid according to claim 2, characterized in that: In step 2, the heating temperature of the stirring tank is 55° C. to 70° C., and the stirring time is 20 min to 35 min.

4. The method for preparing a high-temperature resistant, low-damage, high-density, solid-free well killing fluid according to claim 2, characterized in that: The water is deionized water from which impurities in the form of ions have been removed.

5. The method for preparing a high-temperature resistant, low-damage, high-density, solid-free well killing fluid according to claim 2, characterized in that: The temperature-resistant tackifier is PAC-HV or XC.

6. The method for preparing a high-temperature resistant, low-damage, high-density, solid-free well killing fluid according to claim 2, characterized in that: The temperature-resistant fluid loss reducer is starch FLO-HT.

7. The method for preparing high temperature resistant, low damage, high density, solid-free well killing fluid according to claim 2, characterized in that: The high temperature stabilizer is sodium sulfite.

8. The method for preparing high temperature resistant, low damage, high density, solid-free well killing fluid according to claim 2, characterized in that: The high temperature corrosion inhibitor is a quaternary ammonium salt of bisimidazolyl.

9. The method for preparing high temperature resistant, low damage, high density, solid-free well killing fluid according to claim 2, characterized in that: The salt crystallization inhibitor is PF-NTA-1.

10. The method for preparing high temperature resistant, low damage, high density, solid-free well killing fluid according to claim 2, characterized in that: The waterproof lock agent is hexadecyltrimethylammonium chloride.

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