Solid-free high-density acid-resistant completion fluid and preparation method and application thereof

Abstract

This invention provides a solid-free, high-density, acid-resistant completion fluid, its preparation method, and its application. The density of the solid-free, high-density, acid-resistant completion fluid ranges from 1.60 to 2.11 g / cm³. 3 The fluid comprises a weighting agent and water, wherein the weighting agent includes potassium formate and cesium formate, and the mass ratio of potassium formate to water is 32:10-33:10. The solid-free, high-density, acid-resistant completion fluid provided by this invention has a density range of 1.60-2.11 g / cm³. 3 It is adjustable and can be mixed with acid at a volume ratio of not less than 1:1. It can remain stable for 72 hours at 180℃ without precipitation and has good compatibility.

Description

Technical Field

[0001] This invention relates to a solid-free, high-density, acid-resistant completion fluid, its preparation method, and its application, belonging to the field of completion technology in oil and gas extraction. Background Technology

[0002] As drilling depth increases, more complex formations with high temperature and high pressure are encountered, making development increasingly difficult. In order to develop deep oil and gas reservoirs, new requirements are placed on the performance of completion fluids.

[0003] Currently, depending on the weighting agent, solid-free completion fluids are generally classified into clean brine completion fluids, formate completion fluids, organic polymer completion fluids, and weak gel completion fluids.

[0004] Among them, clean brine completion fluid is currently the most widely used completion fluid. Low-density brine completion fluid can be used in oil and gas fields with normal pressure systems, while high-density brine completion fluid can be used in oil and gas fields with abnormally high pressure systems. It has the characteristics of low solid content, high mineralization, strong inhibition ability, good salt resistance, and good water-locking effect. However, the salts commonly used in clean brine completion fluid, such as zinc bromide and calcium bromide, are expensive, highly corrosive, and toxic to the environment and humans, and are not suitable for widespread use.

[0005] Formate completion fluid is a solid-free, clean completion fluid that can improve gas layer permeability and overcome water lock and liquid phase damage after entering the producing formation. It can be used as both drilling and completion fluid and has received widespread attention due to its good field application results. It is widely used in the drilling and completion of "high-temperature, high-volume, and high-efficiency" wells.

[0006] High-molecular-weight organic salt completion fluids have advantages in well completion operations, including good compatibility, wide density adjustment range, good rheological properties, low solid content, strong shale inhibition, and low environmental pollution, and are widely used in oil and gas field development both domestically and internationally. However, in the high-temperature downhole operating environment, they can significantly exacerbate the corrosion of oil well casing, directly affecting the production capacity and economic life of the oil well, and even the rational development of the entire oil field.

[0007] Weak gel completion fluid is a type of completion fluid that has been introduced in recent years. Its most significant characteristic is its network-like molecular structure. This type of completion fluid also exhibits very strong rheological properties and can provide lubrication for drilling equipment during use. Its toxicity is relatively low, meeting the basic environmental requirements for drilling operations. However, this type of completion fluid also has certain drawbacks. Firstly, it is prone to foaming during use, and this foam is difficult to remove. Secondly, it is also very prone to leakage problems during use.

[0008] It is evident that conventional solids-free well control fluids (also known as completion fluids) currently in use typically employ formate or inorganic salts as weighting agents. However, when these completion fluids are mixed with residual acid in the wellbore during reservoir stimulation operations, blockages occur, clogging the bottom of the well and affecting the progress of the project.

[0009] Therefore, providing a novel solid-free, high-density, acid-resistant completion fluid, its preparation method, and its application has become a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0010] To address the problem that existing conventional solid-free completion fluids are incompatible with acid solutions, causing blockages when in contact with residual acid at the bottom of the well, thus affecting reservoir stimulation and production, the present invention aims to provide a solid-free, high-density, acid-resistant completion fluid, its preparation method, and its application.

[0011] To achieve the above objectives, on the one hand, the present invention provides a solid-free, high-density, acid-resistant completion fluid, wherein the density of the solid-free, high-density, acid-resistant completion fluid ranges from 1.60 to 2.11 g / cm³. 3 It contains a weighting agent and water, wherein the weighting agent includes potassium formate and cesium formate, and the mass ratio of potassium formate to water is 32:10-33:10.

[0012] As a specific embodiment of the solid-free high-density acid-resistant completion fluid described above in this invention, the solid-free high-density acid-resistant completion fluid further comprises an anti-precipitant, which includes N,N-[1,6-hexanediolbis[oxy[2-sulfonylmethyl-2,1-ethane]]]bis[N,N-dimethyl-1-decaamino]-chloro, sodium salt, N,N-[1,6-hexanediolbis[oxy[2-sulfonylmethyl-2,1-ethane]]]bis[N,N-dimethyl-1-undecylamine]-chloro, sodium salt, N, Sodium N-[1,6-hexadiylbis[oxo[2-sulfonylmethyl-2,1-ethane]]] bis[N,N-dimethyl-1-dodecylamine]-chloro, sodium N-[1,6-hexadiylbis[oxo[2-sulfonylmethyl-2,1-ethane]]] bis[N,N-dimethyl-1-tetra ...

[0013] As a specific embodiment of the solid-free high-density acid-resistant completion fluid described above in this invention, the mass ratio of the anti-precipitant to water is 0.5-2:1000, preferably 1:1000.

[0014] The precipitant used in this invention is a conventional substance, and the molecular structure of N,N-[1,6-hexamethylenedi[oxo[2-sulfonylmethyl-2,1-ethane]]]bis[N,N-dimethyl-1-dodecylamine]-chloro sodium salt is shown below:

[0015]

[0016] Taking N,N-[1,6-hexadiylbis[oxo[2-sulfonylmethyl-2,1-ethane]]]bis[N,N-dimethyl-1-dodecylamine]-chloro sodium salt as an example, it can be prepared by a method including the following specific steps:

[0017] First, water, isopropanol, sodium 3-chloro-2-hydroxypropanesulfonate, and N,N-dimethyldodecylamine were added sequentially to a reactor equipped with a reflux condenser. The mixture was reacted at 90°C for 6 hours, while maintaining the pH of the system at 9.

[0018] Then, the reaction product obtained in the previous step was mixed with dibromohexane, sodium hydroxide, ethylene glycol dimethyl ether, and tetrabutylammonium bromide, and reacted at 90°C for 48 h; wherein the molar ratio of sodium 3-chloro-2-hydroxypropanesulfonate, N,N-dimethyldodecylamine and dibromohexane was 2:2:1.

[0019] After the reaction was completed, the solvent was removed by vacuum distillation, the inorganic salt was removed by methanol, and the crude product was recrystallized from acetone to obtain a white solid, which is N,N-[1,6-hexadiylbis[oxo[2-sulfomethyl-2,1-ethane]]]bis[N,N-dimethyl-1-dodecylamine]-chloro, sodium salt.

[0020] As a specific embodiment of the solid-free high-density acid-resistant completion fluid described above in this invention, the weighting agent further includes sodium formate.

[0021] In this invention, the sodium formate and the cesium formate are used for weight replenishment, and their dosage can be reasonably adjusted according to the target density of the solid-free high-density acid-resistant completion fluid.

[0022] As a specific embodiment of the solid-free high-density acid-resistant completion fluid described above in this invention, the solid-free high-density acid-resistant completion fluid further includes a fluid loss reducing agent, which includes carboxymethyl cellulose (CMC).

[0023] As a specific embodiment of the solid-free high-density acid-resistant completion fluid described above in this invention, the mass ratio of the fluid loss reducing agent to water is 0.5-2:100, preferably 1:100.

[0024] As a specific embodiment of the solid-free high-density acid-resistant completion fluid described above in this invention, the solid-free high-density acid-resistant completion fluid further includes a viscosifier, the viscosifier including xanthan gum (XC).

[0025] As a specific embodiment of the solid-free high-density acid-resistant completion fluid of the present invention, the mass ratio of the thickener to water is 0.5-2:100, preferably 1:100.

[0026] On the other hand, the present invention also provides a method for preparing the above-mentioned solid-free high-density acid-resistant completion fluid, wherein the preparation method includes:

[0027] After adding a weighting agent to the water, heat it to above 50°C and stir until the weighting agent is completely dissolved to obtain the solid-free high-density acid-resistant completion fluid.

[0028] As a specific embodiment of the preparation method described above in this invention, when the solid-free high-density acid-resistant completion fluid also contains a fluid loss reducing agent, the preparation method further includes: keeping the temperature of the product obtained after the weighting agent is completely dissolved constant above 50°C, then adding the fluid loss reducing agent and stirring until completely dissolved.

[0029] As a specific embodiment of the preparation method described above in this invention, when the solid-free high-density acid-resistant completion fluid also contains a viscosifier, the preparation method further includes: keeping the temperature of the product obtained after the weighting agent is completely dissolved constant above 50°C, then adding the viscosifier and stirring until completely dissolved.

[0030] As a specific embodiment of the preparation method described above in this invention, when the solid-free high-density acid-resistant completion fluid also contains an anti-precipitant, the preparation method further includes: keeping the temperature of the product obtained after the weighting agent is completely dissolved constant above 50°C, then adding the anti-precipitant and stirring until completely dissolved.

[0031] When the solid-free high-density acid-resistant completion fluid contains any two or three of the following: fluid loss reducer, viscosity modifier, and anti-settling agent, the present invention does not specify the order in which the fluid loss reducer, viscosity modifier, and anti-settling agent are added during the preparation of the solid-free high-density acid-resistant completion fluid. They can be added in a reasonable order according to the actual on-site operation conditions.

[0032] In another aspect, the present invention also provides the application of the above-described solid-free high-density acid-resistant completion fluid in well completion operations during oil or natural gas extraction.

[0033] The solid-free, high-density, acid-resistant completion fluid provided by this invention has a density range of 1.60-2.11 g / cm³. 3It is adjustable and can be mixed with acid (e.g., 20wt% hydrochloric acid) at a volume ratio of not less than 1:1. It can remain stable for 72 hours at 180°C without precipitation and has good compatibility. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is the stratification of four different densities of completion fluid after hot rolling at 180°C for 72 hours, as shown in Test Example 1 of this invention.

[0036] Figure 2 This is a linear expansion rate curve of shale in clear water in Test Example 2 of the present invention.

[0037] Figure 3 In Test Example 2 of this invention, the shale had a density of 1.10 g / cm³. 3 Linear expansion rate curve in solid-free completion fluid.

[0038] Figure 4 In Test Example 2 of this invention, the shale had a density of 1.80 g / cm³. 3 Linear expansion rate curve in solid-free completion fluid.

[0039] Figure 5 This is the evaluation result of the rolling recovery rate of the solid-free high-density acid-resistant completion fluid in Test Example 3 of the present invention. Detailed Implementation

[0040] It should be noted that the term "comprising" and any variations thereof in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method / workshop, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods / workshops, products, or devices.

[0041] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0042] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0043] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0044] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying tables, drawings, and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0046] Example 1

[0047] This embodiment provides a series of solid-free, high-density, acid-resistant completion fluids of different densities, which contain weighting agents and water. In this embodiment, the solid-free, high-density, acid-resistant completion fluid can be prepared according to a preparation method including the following specific steps:

[0048] After adding a weighting agent to the water, heat it to above 50°C and stir until the weighting agent is completely dissolved to obtain the solid-free high-density acid-resistant completion fluid.

[0049] The relevant weighting agent formulations and compatibility properties of the completion fluid and acid are shown in Table 1 below. The acid used in the compatibility test was 20wt% hydrochloric acid. In each group of experiments, the amount of acid used was 100mL, and the amounts of completion fluid used were 100mL, 200mL, and 300mL, respectively.

[0050] Table 1. Formulation and compatibility properties of solid-free high-density acid-resistant completion fluids of different densities.

[0051]

[0052] Comparative Example 1

[0053] This comparative example provides a series of completion fluids of different densities, which contain weighting agents and water. In this comparative example, the completion fluids can be prepared according to a preparation method including the following specific steps:

[0054] After adding a weighting agent to the water, heat it to above 50°C and stir until the weighting agent is completely dissolved to obtain the well completion fluid.

[0055] The relevant weighting agent formulations and the compatibility performance of the completion fluid and acid are shown in Table 2 below. The acid used in the compatibility performance test was 20wt% hydrochloric acid. In each group of experiments, the amount of acid used was 100mL, and the amount of completion fluid used was 100mL, 200mL, and 300mL, respectively.

[0056] Table 2. Formulation and compatibility properties of completion fluids with different densities

[0057]

[0058]

[0059] Comparing the experimental data in Table 1 of Example 1 and Table 2 of Comparative Example 1, it can be seen that after the completion fluid and acid provided in Comparative Example 1 were mixed, white precipitate (most of the precipitate was potassium chloride) was formed. Compared with Comparative Example 1, in Example 1 of the present invention, by controlling the mass ratio of potassium formate, a weighting agent, to water in the solid-free high-density acid-resistant completion fluid to 32:10-33:10, no precipitate was formed after the solid-free high-density acid-resistant completion fluid and acid were mixed at a volume ratio of not less than 1:1, indicating that the completion fluid and acid have good compatibility.

[0060] Example 2

[0061] This embodiment provides a series of densities of 1.80 g / cm³. 3The solid-free, high-density, acid-resistant completion fluid, including the one with a density of 1.80 g / cm³ provided in Example 1. 3 The solid-free, high-density, acid-resistant completion fluid and the fluid with a density of 1.80 g / cm³ provided in Example 1. 3 The completion fluid obtained by adding anti-precipitation agent, fluid loss reducer and viscosifier to solid-free high-density acid-resistant completion fluid;

[0062] The anti-precipitating agent is N,N-[1,6-hexamethylenedi[oxy[2-sulfomethyl-2,1-ethane]]]bis[N,N-dimethyl-1-dodecylamine]-chloro, sodium salt; the water loss reducing agent includes carboxymethyl cellulose; and the thickening agent includes xanthan gum.

[0063] In this embodiment, when no anti-settling agent, fluid loss reducer, or viscosifier is added to the completion fluid, its preparation method includes:

[0064] After adding a weighting agent to water, heat it to above 50°C and stir until the weighting agent is completely dissolved to obtain the solid-free high-density acid-resistant completion fluid.

[0065] When only an anti-settling agent is added to the completion fluid, its preparation method includes:

[0066] After adding a weighting agent to the water, heat it to above 50°C and stir until the weighting agent is completely dissolved to obtain the completion fluid-based slurry.

[0067] The temperature of the completion fluid base slurry is kept constant above 50°C. Then, an anti-precipitation agent is added and stirred until completely dissolved to obtain the solid-free, high-density, acid-resistant completion fluid.

[0068] When only fluid loss reducers and viscosifiers are added to the completion fluid, its preparation method includes:

[0069] After adding a weighting agent to the water, heat it to above 50°C and stir until the weighting agent is completely dissolved to obtain the completion fluid-based slurry.

[0070] The temperature of the completion fluid base slurry is kept constant above 50°C. Then, a fluid loss reducer and a viscosity modifier are added and stirred until completely dissolved to obtain the solid-free, high-density, acid-resistant completion fluid.

[0071] When anti-settling agent, fluid loss reducer, and viscosifier are added to the completion fluid simultaneously, the preparation method includes:

[0072] After adding a weighting agent to the water, heat it to above 50°C and stir until the weighting agent is completely dissolved to obtain the first completion fluid-based slurry.

[0073] Keep the temperature of the first completion fluid-based slurry constant above 50°C, then add a fluid loss reducer and a viscosity modifier, and stir until completely dissolved to obtain the second completion fluid-based slurry.

[0074] The temperature of the second completion fluid base slurry is kept constant above 50°C. Then, an anti-settling agent is added and stirred until completely dissolved to obtain the solid-free, high-density, acid-resistant completion fluid.

[0075] The composition information of the completion fluid and its compatibility with acid, i.e., its tolerance to acid, provided in this embodiment are shown in Table 3 below. The acid used in the compatibility test was 20wt% hydrochloric acid. In each group of experiments, the amount of acid used was 100mL, and the amount of completion fluid used was 100mL, 200mL, and 300mL, respectively. That is, for each type of solid-free high-density acid-resistant completion fluid, three groups of experiments were conducted according to the volume ratio of completion fluid to acid of 1:1, 1:2, and 1:3.

[0076] Table 3. Formulation and compatibility properties of solid-free high-density acid-resistant completion fluid

[0077]

[0078] As can be seen from the experimental data in Table 3, the anti-settling agent is beneficial to further increase the completion fluid's tolerance to acid, that is, the anti-settling agent can further improve the compatibility between the completion fluid and the acid. Its preferred addition amount is 0.1%, while the fluid loss reducer and viscosity enhancer have no substantial effect on the compatibility between the completion fluid and the acid.

[0079] Test Example 1

[0080] This test example evaluates the rheological properties and thermal stability of completion fluid No. 6 in Table 3 above. The rheological evaluation includes:

[0081] After the completion fluid was poured into a high-temperature aging tank and sealed, it was placed in a roller furnace and the temperature was adjusted to 120℃ for aging for 16 hours. The changes in the rheological properties of the completion fluid before and after aging were compared. The thermal stability data of the system before and after aging of the completion fluid are shown in Table 4-1 and Table 4-2 below.

[0082] Table 4-1 Thermal stability data of the completion fluid system before aging

[0083]

[0084] Table 4-2 Thermal stability data of the system after well completion fluid aging

[0085]

[0086] Note: The parameters such as plastic viscosity, dynamic shear force, initial shear force, final shear force, HTHP filtration loss, and pH value in Tables 4-1 and 4-2 were all measured using conventional methods currently available in the field.

[0087] As can be seen from the experimental data in Tables 4-1 and 4-2 above, after the completion fluid system was aged at 120℃ for 16 hours, the plastic viscosity, dynamic shear force, initial shear force, and final shear force all decreased slightly compared with those before aging, proving that the completion fluid formulation has good temperature resistance.

[0088] The settlement stability assessment includes:

[0089] Four different density completion fluids, as shown in Table 5 below, were thoroughly stirred and poured into an aging tube. The tube was then placed in a roller heating furnace, and the temperature was adjusted to 180℃ for 72 hours of hot rolling. After hot rolling, the fluids were cooled to room temperature, and then poured into beakers to observe whether the fluids separated into layers. The layering of the four different density completion fluids after hot rolling at 180℃ for 72 hours is shown below. Figure 1 As shown.

[0090] Table 5. Formulations of completion fluids with different densities

[0091]

[0092] from Figure 1 It can be seen that the solid-free high-density acid-resistant completion fluids of different densities prepared according to the formula in Table 1 were uniformly distributed after being hot rolled at 180℃ for 72 hours without stratification, indicating that these solid-free high-density acid-resistant completion fluids all have good settling stability.

[0093] Test Example 2

[0094] This test example uses a shale expansion tester to test the density of shale in 350 mL of water and 350 mL of sodium hydroxide solution, as shown in Table 5, which is 1.10 g / cm³. 3 Solid-free completion fluid, 350 mL, density 1.80 g / cm³ 3 The linear expansion rate of the solid-free completion fluid system (Completion Fluid No. 2 in Table 3) is shown in the experimental results. Figure 2 , Figure 3 and Figure 4 As shown.

[0095] from Figure 2 , Figure 3 and Figure 4 The experimental data show that, compared to pure water and a density of 1.10 g / cm³, 3 The solid-free completion fluid provided in this embodiment of the invention has an ideal ability to prevent clay hydration and swelling, and can avoid the dispersion and transfer of fine particles, which is very important for protecting the reservoir and stabilizing the wellbore.

[0096] Test Example 3

[0097] This test example measures solid-free, high-density, acid-resistant completion fluids of different densities, including those shown in Table 5 with densities of 1.1 g / cm³. 3 1.3g / cm 3 1.5g / cm 3 The rolling recovery rate of the completion fluid and completion fluid No. 2 in Table 3 was measured using the following methods:

[0098] Take 50g of rock sample with a mesh size of 6-10 and add it to the completion fluid. Then pour the resulting mixture into a high-temperature tank and heat-roll it at 120℃ for 16 hours. After the heat-rolling is completed, remove the high-temperature tank and cool it to room temperature.

[0099] Then pour all the liquid and rock sample from the high-temperature tank onto a 40-mesh sieve and wet screen it in a tank filled with tap water for 1 minute.

[0100] The remaining rock samples were then placed in a constant temperature drying oven at 105±3℃ and dried for 4 hours. After drying, the rock samples were removed and cooled. Finally, the weight of the rock samples was measured and the recovery rate was calculated. The experimental results are shown in [Figure number missing]. Figure 5 As shown.

[0101] Generally, a rolling recovery rate of less than 10% indicates extremely strong dispersion of the rock sample in the completion fluid; 30% indicates strong dispersion; 30%-70% indicates moderate dispersion; 70%-90% indicates weak dispersion; and greater than 90% indicates extremely weak dispersion. Figure 5 The experimental data shows that the solid-free high-density acid-resistant completion fluid provided in this embodiment of the invention has a very high recovery rate, and the shale has very weak dispersion in the completion fluid, indicating that the solid-free high-density acid-resistant completion fluid provided in this embodiment of the invention has a good effect on stabilizing shale.

[0102] In summary, the density range of the solid-free, high-density acid-resistant completion fluid provided in the embodiments of the present invention is 1.60-2.11 g / cm³. 3 It is adjustable and can be mixed with acid at a volume ratio of not less than 1:1. It can remain stable for 72 hours at 180℃ without precipitation and has good compatibility.

[0103] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, substitutions of equivalent components, or equivalent changes and modifications made within the scope of protection of this patent, should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A solid-free, high-density, acid-resistant completion fluid, characterized in that, The density range of the solid-free, high-density, acid-resistant completion fluid is 1.60-2.11 g / cm³. 3 It contains a weighting agent, an anti-precipitating agent and water, wherein the weighting agent includes potassium formate and cesium formate, and the mass ratio of potassium formate to water is 32:10-33:10; The anti-precipitating agent includes sodium salts of N,N-[1,6-hexanediylbis[oxo[2-sulfonylmethyl-2,1-ethane]]]bis[N,N-dimethyl-1-decaamino]-chloro, N,N-[1,6-hexanediylbis[oxo[2-sulfonylmethyl-2,1-ethane]]]bis[N,N-dimethyl-1-undecylamino]-chloro, N,N-[1,6-hexanediylbis[oxo[2-sulfonylmethyl-2,1-ethane]]]bis[N,N-dimethyl-1-dodecylamino]-chloro, and N,N-[1,6-hexanediylbis[oxo[2-sulfonylmethyl-2,1-ethane]]]bis[N,N-dimethyl-1-tetrideamine]-chloro. Sodium salt and one or a combination of several of the following: N,N-[1,6-hexadiylbis[oxo[2-sulfonyl-2,1-ethane]]]bis[N,N-dimethyl-1-tetradecylamine]-chloro, sodium salt.

2. The solid-free, high-density, acid-resistant completion fluid according to claim 1, characterized in that, The mass ratio of the anti-precipitating agent to water is 0.5-2:1000.

3. The solid-free, high-density, acid-resistant completion fluid according to claim 1 or 2, characterized in that, The weighting agent also includes sodium formate.

4. The solid-free, high-density, acid-resistant completion fluid according to claim 1 or 2, characterized in that, The solid-free, high-density, acid-resistant completion fluid also contains a fluid loss reducing agent, which includes carboxymethyl cellulose.

5. The solid-free, high-density, acid-resistant completion fluid according to claim 4, characterized in that, The mass ratio of the water loss reducing agent to water is 0.5-2:

100.

6. The solid-free, high-density, acid-resistant completion fluid according to claim 1 or 2, characterized in that, The solid-free, high-density, acid-resistant completion fluid also contains a viscosifier, which includes xanthan gum.

7. The solid-free, high-density, acid-resistant completion fluid according to claim 6, characterized in that, The mass ratio of the thickener to water is 0.5-2:

100.

8. The method for preparing the solid-free, high-density, acid-resistant completion fluid according to any one of claims 1-7, characterized in that, include: After adding a weighting agent to the water, heat it to above 50°C and stir until the weighting agent is completely dissolved to obtain the solid-free high-density acid-resistant completion fluid.

9. The application of the solid-free, high-density, acid-resistant completion fluid according to any one of claims 1-7 in well completion operations during oil or natural gas extraction.

Images