阅读说明：本技术 无固相修井液及其制备方法与应用 (Solid-free workover fluid and preparation method and application thereof ) 是由 唐胜蓝 孟祥娟 彭建云 王茜 刘举 杨宪民 袁学芳 刘明球 吴红军 张晖 刘己全 于 2020-05-21 设计创作，主要内容包括：本发明提供一种无固相修井液及其制备方法与应用。该无固相修井液采用无固相加重剂、提切剂、缓蚀剂、防水锁剂分散剂和水,并限定各原料含量,利用各原料之间相互作用,协同增效,能保证无固相修井液的适用密度范围达到1.5g/cm～(3)-1.82g/cm～(3),最高密度可达1.80-1.82g/cm～(3),使本发明实施例所提供的无固相修井液具有密度高、腐蚀速率低、地层伤害小、携砂能力强、粘度可调等特点,可用于高温、高密度、低渗储层修井作业。该制备方法通过控制上述制备方法中各原料的加入顺序,有助于各原料之间混合均匀,提高无固相修井液的相应性能,例如抗温性能和沉降稳定性等。(The invention provides a solid-free workover fluid and a preparation method and application thereof. The solid-free workover fluid adopts a solid-free weighting agent, a shear enhancing agent, a corrosion inhibitor, a waterproof locking agent dispersant and water, limits the content of each raw material, utilizes the interaction and the synergistic effect among the raw materials, and can ensure that the applicable density range of the solid-free workover fluid reaches 1.5g/cm 3 ‑1.82g/cm 3 The highest density can reach 1.80-1.82g/cm 3 The solid-free workover fluid provided by the embodiment of the invention has the characteristics of high density, low corrosion rate, small formation damage, strong sand carrying capacity, adjustable viscosity and the like, and can be used for high-temperature, high-density and low-permeability reservoir workover operation. The preparation method is beneficial to uniformly mixing the raw materials by controlling the adding sequence of the raw materials in the preparation method, and improves the corresponding performances of the solid-free workover fluid, such as temperature resistance, sedimentation stability and the like.)

1. The solid-free workover fluid comprises the following raw materials in percentage by weight:

2. the solidless workover fluid of claim 1, wherein the shear enhancing agent is at least one of modified montmorillonite, inorganic electropositive dipolymer, bentonite;

the corrosion inhibitor is at least one of sodium tungstate, imidazoline compound, propiolic alcohol and pyrimidine compound.

3. The solidless workover fluid of claim 2, wherein the modified montmorillonite is a phosphonium quaternary modified montmorillonite;

the inorganic positive electricity double polymer is magnesium aluminum hydroxide, magnesium aluminum hydroxide hydrotalcite or modified layered magnesium aluminum hydroxide;

the imidazoline compound is imidazoline quaternary ammonium salt derivatives, alkenyl imidazoline quaternary ammonium salt, eleostearic acid imidazoline derivatives or imidazoline guanidine salt.

4. The solids free workover fluid of any one of claims 1 to 3, wherein the water and lock resistant agent is a fluorosurfactant;

the dispersing agent is at least one of sodium alginate, potassium metasilicate and sodium silicate.

5. The solids free workover fluid of claim 4, wherein the fluorosurfactant is a perfluoroalkyl sulfonate surfactant, a perfluoroalkyl carboxylic acid surfactant, or a quaternary ammonium fluoride surfactant.

6. A method of preparing the solids free workover fluid of any one of claims 1 to 5, comprising the steps of:

adding the cutting agent into water, and sequentially carrying out first stirring and standing maintenance to obtain a first mixed solution;

under the second stirring action, adding a waterproof locking agent, a corrosion inhibitor and a dispersing agent into the first mixed solution, and after the addition is finished, continuing to perform second stirring to obtain a second mixed solution;

and under the third stirring action, adding the solid-free weighting agent into the second mixed solution, and continuously stirring until the weighting agent is dissolved to prepare the solid-free workover fluid.

7. The preparation method according to claim 6, wherein the stirring speed of the first stirring is 11000r/min to 13000r/min, and the stirring time is 15min to 25 min;

the temperature of the standing and maintaining is 22-28 ℃, and the time is 20-28 h.

8. The production method according to claim 6 or 7, wherein the stirring speed of the second stirring is 2500r/min to 3500 r/min; the stirring time for continuing the second stirring is 18min-22 min;

the stirring speed of the third stirring is 2500r/min-3500 r/min.

9. The preparation method according to any one of claims 6 to 8, characterized in that under the second stirring action, a waterproof locking agent, a corrosion inhibitor and a dispersant are added to the first mixed solution in sequence;

the adding speed of the solid-free weighting agent is 100g/min-500 g/min.

10. Use of the solids free workover fluid of any one of claims 1 to 5 in reservoir workover operations.

Technical Field

The invention belongs to the technical field of petroleum and natural gas and completion/workover fluid, and particularly relates to a solid-free workover fluid and a preparation method and application thereof.

Background

At present, the drilling and production of oil and gas on land and at sea in China are extending to the fields containing oil and gas such as deep layer (4500 m deep underground), ultra-deep layer (6000 m deep underground) and shale gas, such as oil areas such as Tarim, Sichuan and south China sea, and need to face special environments such as high pressure and high temperature in the operation process.

In the well repairing operation process, the solid phase fluid well repairing liquid is basically used at present, but the solid phase fluid well repairing liquid has the problems of long period, poor high-temperature sedimentation stability, great damage of a solid phase in the well repairing liquid to a reservoir stratum and the like in the reservoir stratum well repairing operation.

Therefore, chinese patent document CN105176506A discloses an acid salt solid-free medium-density workover fluid, which has no solid phase, thereby avoiding the problem of great damage of the solid phase to the reservoir, but when the workover fluid is used for ultrahigh pressure, ultrahigh temperature and ultra-low permeability stratum workover, the settlement stability, temperature resistance and corrosion rate of the workover fluid still need to be improved.

Disclosure of Invention

The invention provides a solid-free workover fluid and a preparation method and application thereof, which at least solve the problem that the existing workover fluid is still to be improved in the aspects of sedimentation stability, temperature resistance and corrosion rate when the existing workover fluid is used for workover operations of ultrahigh-pressure, ultrahigh-temperature and ultra-low-permeability stratums.

In order to achieve the above object, the embodiments of the present invention provide the following technical solutions:

the first aspect of the embodiment of the invention provides a solid-free workover fluid which comprises the following raw materials in percentage by weight:

the solid-free workover fluid provided by the embodiment of the invention adopts a solid-free weighting agent, a shear enhancing agent, a corrosion inhibitor, a waterproof locking agent dispersant and water, limits the content of each raw material, utilizes the interaction among the raw materials, realizes synergistic interaction, and can ensure that the applicable density range of the solid-free workover fluid reaches 1.5g/cm³-1.82g/cm³The highest density can reach 1.80-1.82g/cm³So that the solid-free workover fluid provided by the embodiment of the invention has high densityThe sand carrier has the characteristics of low corrosion rate, small formation damage, strong sand carrying capacity, adjustable viscosity and the like, and can be used for high-temperature, high-density and low-permeability reservoir workover operation. Meanwhile, the solid-free workover fluid can ensure the safety of workover construction, reduce the workover cost, improve the workover effect, obtain good economic benefit and social benefit, and is worthy of popularization and application.

The solid free weighting agent may be selected according to the actual need, for example, in an embodiment of the present invention, the solid free weighting agent may be HWJZ-1 weighting agent available from Kyowa oil, Wei technologies, Inc.

The shear-improving agent is at least one of modified montmorillonite, inorganic positive double polymer and bentonite; further, the modified montmorillonite is quaternary phosphonium salt modified montmorillonite; the inorganic positive electricity double polymer is magnesium aluminum hydroxide, magnesium aluminum hydroxide hydrotalcite and modified layered magnesium aluminum hydroxide;

the corrosion inhibitor is at least one of sodium tungstate, imidazoline compound, propiolic alcohol and pyrimidine compound; further, the imidazoline compound is an imidazoline quaternary ammonium salt derivative, an alkenyl imidazoline quaternary ammonium salt, a eleostearic acid imidazoline derivative or an imidazoline guanidine salt; the pyrimidine complex may be 2-hydroxypyrimidine;

in a specific embodiment of the invention, the water-blocking agent is a fluorine-containing surfactant; further, the fluorine-containing surfactant is a perfluoroalkyl sulfonate surfactant, a perfluoroalkyl carboxylic acid surfactant or a quaternary ammonium fluoride surfactant; for example the perfluoroalkane sulfonate surfactant may be Perfluorooctanesulfonate (PFOS), Perfluorohexanesulfonate (PFHS) or Perfluorobutanesulfonate (PFBS); the perfluoroalkylcarboxylic acid can be a trifluorocarboxylic acid;

the dispersing agent is at least one of sodium alginate, potassium metasilicate and sodium silicate.

The second aspect of the embodiments of the present invention provides a method for preparing the above solid-free workover fluid, including the following steps:

adding the cutting agent into water, and sequentially carrying out first stirring and standing maintenance to obtain a first mixed solution;

under the second stirring action, adding a waterproof locking agent, a corrosion inhibitor and a dispersing agent into the first mixed solution, and after the addition is finished, continuing to perform second stirring to obtain a second mixed solution;

and under the third stirring action, adding the solid-free weighting agent into the second mixed solution, and continuously stirring until the weighting agent is dissolved to prepare the solid-free workover fluid.

By controlling the adding sequence of the raw materials in the preparation method, the raw materials are uniformly mixed, and the corresponding properties of the solid-free workover fluid, such as temperature resistance, sedimentation stability and the like, are improved;

in the specific embodiment of the invention, the stirring speed of the first stirring is 11000r/min-13000r/min, and the stirring time is 15min-25 min; further, the stirring speed of the first stirring is 12000r/min, and the stirring time is 20 min;

the temperature of the standing maintenance is 22-28 ℃, and the time is 20-28 h; further, the temperature of standing and curing is 25 ℃, and the time is 24 hours.

In a specific embodiment of the invention, the stirring speed of the second stirring is 2500r/min-3500 r/min; the stirring time for continuing the second stirring is 18min-22 min; further, the stirring speed of the second stirring is 3000 r/min; the stirring time for continuing the second stirring is 20 min;

the stirring speed of the third stirring is 2500r/min-3500 r/min; further, the stirring speed of the third stirring was 3000 r/min.

In a specific embodiment, under the second stirring action, sequentially adding a waterproof locking agent, a corrosion inhibitor and a dispersing agent into the first mixed solution; by sequentially adding corresponding raw materials into the first mixed solution, the compatibility of the first mixed solution and the raw materials can be better matched, the waterproof locking agent, the corrosion inhibitor and the dispersing agent are fully dissolved or dispersed in the first mixed solution, and the corresponding performances of the solid-free workover fluid, such as temperature resistance, sedimentation stability and the like, are improved;

the adding speed of the HWJZ-1 weighting agent is 100g/min-500 g/min; and slowly adding the HWJZ-1 weighting agent into the second mixed solution by limiting the adding speed, so as to ensure the compatibility of the HWJZ-1 weighting agent and the second mixed solution.

In a third aspect of the embodiments of the present invention, an application of the above-mentioned solidless workover fluid in reservoir workover operation is provided.

Compared with the prior art, the invention has at least the following beneficial effects: the solid-free workover fluid provided by the embodiment of the invention has wide density range (1.5 g/cm)³-1.82g/cm³) The method has the characteristics of no solid phase, high viscosity-shear rate (good sand carrying property), low corrosion rate, good reservoir protection property and the like. The solid-free workover fluid has the characteristics that the problems of low permeability, high pressure (higher than 70MPa) and poor temperature resistance, sedimentation stability, great damage to stratum, poor sand carrying and the like of the workover fluid in high-temperature gas well (more than or equal to 150 ℃) workover operation can be well solved, and the solid-free workover fluid can be applied to the density requirement (1.5 g/cm)³-1.82g/cm³) Workover operations under different geological characteristics.

Through a large number of experimental researches, the applicant prepares a high-temperature-resistant high-density solid-free workover fluid formula system which has the characteristics of high density, low corrosion rate, small formation damage, strong sand carrying capacity, adjustable viscosity and the like, can be used for workover operations of high-temperature, high-density and low-permeability reservoirs, and mainly solves the problems of poor sedimentation stability, no temperature resistance, high corrosion rate, large formation damage and the like of the conventional workover fluid when the conventional workover fluid is used for workover operations of ultrahigh-pressure, ultrahigh-temperature and ultra-low-permeability formations.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

FIG. 1 is a macro-topography of the corrosion of tap water on super 13Cr steel sheets in the invention;

FIG. 2 is a scanning electron microscope image of the corrosion of tap water on super 13Cr steel sheets amplified 5000 times in the present invention;

FIG. 3 is a macro topography diagram of corrosion of a common composite salt solution to a super 13Cr steel sheet in the invention;

FIG. 4 is a scanning electron microscope image of the corrosion condition of the common composite salt solution to the super 13Cr steel sheet amplified 5000 times;

FIG. 5 is a macro topography of corrosion of a super 13Cr steel plate by a solid-free workover fluid in example 2 of the present invention;

FIG. 6 is a scanning electron microscope image of the corrosion condition of the non-solid phase workover fluid on the super 13Cr steel sheet amplified by 5000 times.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings and the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the following examples, unless otherwise specified, the steps may be carried out by methods, apparatuses, devices, structures, components, etc. conventional in the art, and reagents, etc. used therein may be commercially available or prepared by methods conventional in the art.

The HWJZ-1 weighting agents used in the examples and comparative examples described below were HWJZ-1 weighting agents available from Kyoxi Youwei science, Inc.

Example 1

The embodiment provides a solid-free workover fluid and a preparation method thereof. The solid-free workover fluid comprises 440g of HWJZ-1 weighting agent, 22g of lifting and cutting agent, 5g of corrosion inhibitor, 7g of waterproof locking agent, 17g of dispersing agent and 510g of clear water; wherein the extracting and cutting agent is quaternary phosphonium salt modified montmorillonite; the corrosion inhibitor is imidazoline; the waterproof locking agent is perfluorooctane sulfonate; the dispersant is sodium silicate;

the preparation method of the solid-free workover fluid comprises the following steps:

(1) weighing clear water, adding the clear water into a high-stirring cup, adding a cutting extraction agent into the high-stirring cup, stirring at a high speed of 12000r/min for 20min, standing and maintaining at room temperature of 25 ℃ for 24h after stirring, and obtaining a first mixed solution;

(2) under the stirring action of 3000r/min, sequentially adding a waterproof locking agent, a corrosion inhibitor and a dispersing agent into the first mixed solution, and after the addition is finished, continuously stirring for 20min to obtain a second mixed solution;

(3) and adding an HWJZ-1 weighting agent into the second mixed solution under the stirring action of 3000r/min, wherein the adding speed of the HWJZ-1 weighting agent is 100g/min, and continuously stirring until the HWJZ-1 weighting agent is completely dissolved to prepare the solid-free workover fluid.

Example 2

The embodiment provides a solid-free workover fluid and a preparation method thereof. The solid-free workover fluid comprises 369g of HWJZ-1 weighting agent, 9g of stripping agent, 3.2g of corrosion inhibitor, 3g of waterproof locking agent, 10g of dispersing agent and 200g of clear water; wherein the extracting and cutting agent is bentonite; the corrosion inhibitor is sodium tungstate; the waterproof locking agent is trifluoroacetic acid; the dispersing agent is sodium alginate;

the preparation method of the solid-free workover fluid comprises the following steps:

(1) weighing clear water, adding the clear water into a high-stirring cup, adding a cutting extraction agent into the high-stirring cup, stirring at a high speed of 12000r/min for 20min, standing and maintaining at room temperature of 25 ℃ for 24h after stirring, and obtaining a first mixed solution;

(2) under the stirring action of 3000r/min, sequentially adding a waterproof locking agent, a corrosion inhibitor and a dispersing agent into the first mixed solution, and after the addition is finished, continuously stirring for 20min to obtain a second mixed solution;

(3) and adding an HWJZ-1 weighting agent into the second mixed solution under the stirring action of 3000r/min, wherein the adding speed of the HWJZ-1 weighting agent is 300g/min, and continuously stirring until the HWJZ-1 weighting agent is completely dissolved to prepare the solid-free workover fluid.

Example 3

The embodiment provides a solid-free workover fluid and a preparation method thereof. The solid-free workover fluid comprises 630g of HWJZ-1 weighting agent, 15g of lifting and cutting agent, 10g of corrosion inhibitor, 3g of waterproof locking agent, 13g of dispersing agent and 330g of clear water; wherein the extracting and cutting agent is magnesium aluminum hydroxide hydrotalcite; the corrosion inhibitor is propiolic alcohol; the waterproof locking agent is a fluorinated quaternary ammonium salt surfactant; the dispersant is potassium metasilicate;

the preparation method of the solid-free workover fluid comprises the following steps:

(1) weighing clear water, adding the clear water into a high-stirring cup, adding a cutting agent into the high-stirring cup, stirring at a high speed of 11000r/min for 25min, standing and maintaining at room temperature of 22 ℃ for 28h after stirring, and obtaining a first mixed solution;

(2) under the stirring action of 2500r/min, sequentially adding a waterproof locking agent, a corrosion inhibitor and a dispersing agent into the first mixed solution, and after the addition is finished, continuously stirring for 22min to obtain a second mixed solution;

(3) and adding the HWJZ-1 weighting agent into the second mixed solution under the stirring action of 3500r/min, wherein the adding speed of the HWJZ-1 weighting agent is 500g/min, and continuously stirring until the HWJZ-1 weighting agent is completely dissolved to prepare the solid-free workover fluid.

Example 4

The embodiment provides a solid-free workover fluid and a preparation method thereof. The solid-free workover fluid comprises 550g of HWJZ-1 weighting agent, 20g of lifting and cutting agent, 8g of corrosion inhibitor, 6g of waterproof locking agent, 15g of dispersing agent and 400g of clear water; wherein the extracting and cutting agent is bentonite; the corrosion inhibitor is 2-hydroxypyrimidine; the waterproof locking agent is a fluorinated quaternary ammonium salt surfactant; the dispersant is potassium metasilicate;

the preparation method of the solid-free workover fluid comprises the following steps:

(1) weighing clear water, adding the clear water into a high-stirring cup, adding a cutting extraction agent into the high-stirring cup, stirring at a high speed of 13000r/min for 15min, standing and maintaining at room temperature of 28 ℃ for 20h after stirring, and obtaining a first mixed solution;

(2) under the stirring action of 3500r/min, sequentially adding a waterproof locking agent, a corrosion inhibitor and a dispersing agent into the first mixed solution, and after the addition is finished, continuously stirring for 18min to obtain a second mixed solution;

(3) and adding an HWJZ-1 weighting agent into the second mixed solution under the stirring action of 2500r/min, wherein the adding speed of the HWJZ-1 weighting agent is 400g/min, and continuously stirring until the HWJZ-1 weighting agent is completely dissolved to prepare the solid-free workover fluid.

Example 5

The embodiment provides a solid-free workover fluid and a preparation method thereof. The solid-free workover fluid comprises 550g of HWJZ-1 weighting agent, 20g of lifting and cutting agent, 8g of corrosion inhibitor, 6g of waterproof locking agent, 15g of dispersing agent and 400g of clear water; wherein the extracting and cutting agent is bentonite; the corrosion inhibitor is imidazoline and propiolic alcohol, and the mass ratio of the imidazoline to the propiolic alcohol is 1: 1; the waterproof locking agent is perfluorohexane sulfonate (PFHS); the dispersing agent is sodium alginate and potassium metasilicate, and the mass ratio of the sodium alginate to the potassium metasilicate is 1: 1;

the preparation method of the solid-free workover fluid comprises the following steps:

(1) weighing clear water, adding the clear water into a high-stirring cup, adding a cutting extraction agent into the high-stirring cup, stirring at a high speed of 13000r/min for 15min, standing and maintaining at room temperature of 28 ℃ for 20h after stirring, and obtaining a first mixed solution;

(2) under the stirring action of 3500r/min, sequentially adding a waterproof locking agent, a corrosion inhibitor and a dispersing agent into the first mixed solution, and after the addition is finished, continuously stirring for 18min to obtain a second mixed solution;

(3) and adding an HWJZ-1 weighting agent into the second mixed solution under the stirring action of 2500r/min, wherein the adding speed of the HWJZ-1 weighting agent is 200g/min, and continuously stirring until the HWJZ-1 weighting agent is completely dissolved to prepare the solid-free workover fluid.

Test example 1

The rheology of the solid-free workover fluid prepared in example 1-2 was measured at 25 ℃. + -. 1 ℃ as specified in GB/T16783.1 at different temperatures after allowing the fluid to stand at constant temperature, and the corresponding test results are shown in tables 1 and 2 below:

TABLE 1 Properties of the solid-free workover fluid aged at different densities

TABLE 2 Properties of the solid-free workover fluid at different temperatures after aging

Test example 2

And (3) simultaneously measuring the core swelling capacity of different media at room temperature by using an NP-1D multi-connection shale dilatometer. The smaller the core expansion, the better the inhibition of the medium. The corresponding test method is to measure the core expansion amount of the solid-free workover fluid according to the specification of 4.2.8 in the enterprise standard Q/SHCG 56 of the China petrochemical group company, and the specific test method is as follows:

weighing 10.00g of test calcium bentonite which is baked for 4 hours at the temperature of (105 soil 3), putting the test calcium bentonite into a measuring cylinder of a shale expansion tester, and adding 4MPa pressure and keeping the pressure for 5 minutes to prepare a test core. And (3) mounting the measuring cylinder with the rock core on a shale expansion tester, injecting a sample solution into the measuring cylinder, measuring the rock core expansion amount for 8 hours, simultaneously using distilled water as a blank test, and calculating the shale expansion reduction rate according to the following formula.

H＝(△H₁-△H)/△H₁×100

In the formula: h-shale expansion reduction,%; delta H₁Distilled water core swell in millimeters (mm); delta H-core swell of the sample solution in millimeters (mm).

The corresponding test results are shown in table 3 below:

TABLE 3 inhibition of cores by different media

From table 3, it can be seen that: the solid-free workover fluid disclosed by the invention has a 24-hour linear expansion rate of less than 2% on a rock core.

Test example 3

The shale rolling recovery rate of the solid-phase-free workover fluid is determined, and the test method comprises the following steps:

(1) in the experiment, 350ml of solid-free workover fluid or distilled water is mixed with 50.00g of shale waste (5-10 meshes, the shale waste is outcrop variegated shale from Gongda Anzhai group (J1 z)), the mixture is aged at 100 ℃ for 16 hours, cleaned, sieved by a 40-mesh sieve, dried at 120 ℃ for 3 hours and weighed, and the primary shale recovery rate is calculated;

(2) and mixing 350ml of solid-free workover fluid or distilled water with the primary rock debris, aging at 160 ℃ for 16 hours, cleaning, sieving with a 40-mesh sieve, drying at 120 ℃ for 3 hours, weighing, and calculating to obtain the recovery rate of the secondary shale. The test results are shown in table 4.

TABLE 4 rock debris rolling recovery experiment of solid-phase-free workover fluid

Item	Tap water	Example 3	Example 2
				The recovery rate of the sample by one-time rolling%	18.4	100.06	100.04
Recovery increase rate%	/	443.80	443.70
				The secondary rolling recovery rate of the sample%	/	78.82	82.28
Recovery increase rate%	/	328.37	347.17

From table 4, it can be seen that: the one-time shale rolling recovery rate of the solid-free workover fluid is more than 99%.

Test example 4

The damage condition of the high-temperature-resistant high-density solid-free workover fluid to the rock core is tested by referring to a method in Chinese journal literature (Leili army, Kangyili, Chenyijian, compact sandstone water saturation establishing new method-capillary self-priming method [ J ]. proceedings of the southwest college of Petroleum institute, 2005,27(1):28-31.), and the specific test method is as follows:

selecting a rock core of a big north 307 well for carrying out an experiment; establishing water saturation (simulating formation water) for the rock core by using a capillary self-absorption method [4-5 ]; carrying out a gas drive water phase flowback experiment on the self-absorbed experimental rock sample, and monitoring the pressure and the flow by using a computer; the pressure setting is consistent with the standard permeability test, and the flow-back time is about 7-24 h. And taking out and weighing every 20min within 2h before flowback, taking out and weighing every 1h after 2h, measuring the weight of the experimental rock sample after flowback is finished, and measuring the permeability recovery rate of the core after flowback.

The corresponding test results are shown in table 5 below:

TABLE 5 damage to rock core by solid-free workover fluid

Test example 5

The test method refers to the test method in part 5 of SY/T0026-1999 Water corrosivity test method. Compared with the common compound salt solution (namely HWJZ-1 weighting agent), the high-temperature-resistant high-density solid-free workover fluid is tested for the corrosion rate to the super 13Cr steel sheet under the condition of 160 ℃, and the corresponding test results are shown in the following table 6 and figures 1-6:

TABLE 6 Corrosion of super 13Cr steel plates by non-solid phase workover fluid

Sample numbering	Tap water	Comparative example	Example 2
				Formulation of	-	Ordinary complex salt solution	Solid-free workover fluid
Average corrosion rate/mm/a	0.00431	0.257935	0.0056822

As can be seen from table 6 and fig. 1-6: the corrosion rate of the solid-free workover fluid in the embodiment of the invention is low.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are still within the scope of the technical solution of the present invention.