Solid-phase-free film-forming completion fluid suitable for loose sandstone and preparation method thereof
By using a solid-phase film-forming completion fluid containing composite salts, film-forming sealing agents, oxygen-destructing agents, corrosion inhibitors and polymer cutting agents in the horizontal well development of loose sandstone reservoirs, the problems of poor sealing, strong corrosiveness and insufficient suspension ability in the prior art were solved, and the completion effect of strong inhibitory, good sealing performance and corrosion resistance was achieved.
Patent Information
- Application Number
- CN202311453359.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-03
- Publication Date
- 2025-05-06
AI Technical Summary
In the development of horizontal wells in loose sandstone reservoirs, the clean brine completion fluid used has problems such as poor sealing, strong corrosiveness and insufficient suspension capacity, resulting in reduced effective oil drainage area of the screen pipe and reservoir damage.
A solid-phase film-forming completion fluid is used, and its components include 65-80 parts of water, 15-30 parts of composite salt, 2-5 parts of film-forming solid-phase sealing agent, 0.02-0.08 parts of oxygen deoxygenation, 0.02-0.06 parts of passivation film-forming corrosion inhibitor and 0.1-1.0 parts of polymer-based cutting agent. By combining the composite salt with the film-forming corrosion inhibitor, inhibition, sealing performance and corrosion resistance are balanced.
It achieves strong inhibitory properties, improves sealing performance and ensures good corrosion resistance, reduces screen pipe blockage and reservoir damage, and improves the replacement and replacement capabilities of drilling fluid in the wellbore.
Smart Images
Figure BDA0004529635910000071 
Figure BDA0004529635910000081 
Figure BDA0004529635910000082
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of oil and natural gas development, and in particular to a solid-phase film-forming completion fluid suitable for loose sandstone and a preparation method thereof. Background Art
[0002] Loose sandstone reservoirs have high production and are often developed using horizontal wells. However, during the screen run, although salt water solid-free drilling fluid is used, after passing through the shallow strong slurry section, the finely dispersed inferior solid phase is difficult to remove. This part of the solid phase and the polymer in the drilling fluid form a plug under the action of pressure difference, reducing the effective oil leakage area of the screen. Therefore, after drilling the footage and fully circulating the drilling fluid, before running the screen, the drilling fluid in the wellbore needs to be fully displaced.
[0003] At present, clean brine completion fluid is widely used at home and abroad. The main problems of this system are as follows: first, it fails to achieve good solid-free sealing, the completion fluid has a large filtration loss, and the density and crystallization point are difficult to control due to the influence of downhole temperature and pressure; second, some systems mainly use inorganic salts to increase the density of the system. Although it has strong inhibitory properties, it also has great corrosion to downhole tools. There is also a system that uses organic salts as weighting agents, but its cost is too high, which is not conducive to large-scale promotion. Summary of the invention
[0004] The main purpose of the present invention is to provide a solid-free film-forming completion fluid suitable for loose sandstone and a preparation method thereof, so as to solve the problems of poor plugging performance and strong corrosiveness of the slurry replacement protection fluid in the current reservoir screen completion.
[0005] According to one aspect of the present invention, a solid-free film-forming completion fluid suitable for loose sandstone is provided, which comprises, by weight: 65-80 parts of water, 15-30 parts of composite salt, 2-5 parts of film-forming solid-free plugging agent, 0.02-0.08 parts of deoxidizer, 0.02-0.06 parts of passivating film-forming corrosion inhibitor, and 0.1-1.0 parts of polymer shearing agent.
[0006] According to one embodiment of the present invention, the completion fluid comprises, by weight: 69-73 parts of water, 23-28 parts of composite salt, 2-4 parts of film-forming solid-free plugging agent, 0.02-0.06 parts of deoxidizer, 0.03-0.04 parts of passivating film-forming corrosion inhibitor, and 0.35-0.5 parts of polymer shearing agent.
[0007] According to one embodiment of the present invention, the composite salt comprises: sodium sulfate, potassium citrate, potassium tartrate and potassium formate.
[0008] According to one embodiment of the present invention, the mass ratio of sodium sulfate, potassium citrate, potassium tartrate and potassium formate is (2-4.5):(1.5-3):(1-3):(2-4).
[0009] According to one embodiment of the present invention, the film-forming solid-phase-free plugging agent is a polyacrylamide film-forming agent.
[0010] According to one embodiment of the present invention, the oxygen scavenger is a complex of disodium stannous citrate and sodium D-ascorbate.
[0011] According to one embodiment of the present invention, the passivation film-forming corrosion inhibitor is a complex of diethylenetriamine, triethylenetetramine and ethylenediamine.
[0012] According to one embodiment of the present invention, the polymer-based shearing agent is a synthetic polymer-based shearing agent.
[0013] According to another aspect of the present invention, a method for preparing the completion fluid as described above is provided, comprising: adding a polymer-based shear enhancer, a film-forming solid-free plugging agent, a deoxidizer, a film-forming corrosion inhibitor and a composite salt into water and stirring the water to obtain the completion fluid;
[0014] Among them, the polymer shearing agent is added first and then the composite salt is added; after adding the polymer shearing agent, stirring is performed for a first predetermined time; after adding the film-forming solid-free plugging agent, stirring is performed for a second predetermined time; after adding the deoxidizer and the film-forming corrosion inhibitor, stirring is performed for a third predetermined time; after adding the composite salt, stirring is performed for a fourth predetermined time.
[0015] According to one embodiment of the present invention, a polymer shearing agent is slowly added at a rate of 0.1-0.2 g / min; and / or
[0016] The first scheduled time is 55-65 minutes, the second scheduled time is 10-20 minutes, the third scheduled time is 10-20 minutes, and the fourth scheduled time is 55-65 minutes.
[0017] In the solid-free film-forming completion fluid suitable for loose sandstone according to the embodiment of the present invention, the composite salt weighting and the film-forming corrosion inhibitor can be selected to balance the main problems of inhibition, solid-free weighting, corrosion inhibition and cost; the solid-free film-forming plugging agent can be selected to improve the plugging ability and reduce the reservoir damage caused by the residual solid phase in the wellbore invading the reservoir under the pressure difference during the operation process; the polymer shearing agent is selected to adjust the rheological parameters according to the requirements of the single well formation, solve the problem of poor displacement and carrying capacity, and efficiently displace the drilling fluid in the wellbore. The present invention can generally achieve strong inhibition, improve the plugging performance and ensure good corrosion resistance. DETAILED DESCRIPTION
[0018] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments.
[0019] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. The subsequent embodiments will not explain this one by one.
[0020] The present invention provides a solid-free film-forming completion fluid suitable for loose sandstone, which comprises, by weight: 65-80 parts of water, 15-30 parts of composite salt, 2-5 parts of film-forming solid-free plugging agent, 0.02-0.08 parts of deoxidizer, 0.02-0.06 parts of passivation film-forming corrosion inhibitor, and 0.1-1.0 parts of polymer shearing agent.
[0021] The solid-free slurry replacement protective fluid for screen completion of loose sandstone reservoir of the present invention is used after the drilling footage is completed and the drilling fluid is fully circulated and before the screen is lowered. The system has no solid phase components, and composite salt is selected for weighting and used in combination with a film-forming corrosion inhibitor to balance and solve four major problems of inhibition, no solid phase weighting, corrosion inhibition and cost; a solid-free film-forming plugging agent is selected to improve the plugging capacity on the basis of the mud cake in the early drilling fluid, and reduce the reservoir damage caused by the residual solid phase in the wellbore invading the reservoir under the pressure difference during the operation process; a polymer shearing agent is selected to adjust the rheological parameters according to the requirements of the single well formation, solve the problems of poor displacement and carrying capacity, and efficiently displace and replace the drilling fluid in the wellbore.
[0022] The functions of the components and their contents in the solid-free film-forming completion fluid of the present invention are described below:
[0023] (1) 65-80 parts of water: Water is a dispersion medium that ensures the flow of the fluid. If the content is too much, the overall effect will decline. If the content is less than 65 parts, it will lead to poor dissolution and dispersion of various substances, affecting product stability.
[0024] (2) 15-30 parts of composite salt: The composite salt plays an inhibitory role. If the content is too high, it cannot be completely dissolved and the cost is unaffordable. If the content is less than 15, the inhibitory effect is not enough to meet the product performance requirements.
[0025] (3) 2-5 parts of film-forming non-solid phase plugging agent: This material plays a film-forming plugging role. When its content is higher than 5 parts, it cannot be evenly dispersed in the system, and the synthesis cost is high and the cost is unaffordable. If it is lower than 2 parts, the plugging property is insufficient.
[0026] (4) 0.02-0.08 parts of deoxidizer: This agent mainly plays the role of deoxidation and corrosion inhibition. Due to the addition of a large amount of composite salt, there is a risk of corrosion to the drilling tools, so deoxidation and corrosion inhibition are required; when the content is higher than 0.08 parts, its deoxidation and corrosion inhibition effect tends to be stable, so there is no need to increase the amount to increase the cost burden; when the content is lower than 0.02 parts, there is no deoxidation and corrosion inhibition effect in the system.
[0027] (5) 0.02-0.06 parts of passivating film-forming corrosion inhibitor: This agent mainly protects drill bits from corrosion. It is different from the deoxidizer in principle. Here, it works synergistically with the deoxidizer, and the film formed mainly plays a preventive role. When the content is higher than 0.08 parts, its film-forming anti-corrosion effect tends to be stable, so there is no need to increase the amount to increase the cost burden. When the content is lower than 0.02 parts, the film-forming anti-corrosion effect in the system is very small and cannot play a good role.
[0028] (6) 0.1-1.0 parts, polymer cutting agent: This agent is used to suspend the drill cuttings formed during drilling. The density of drill cuttings is generally 2.2-2.7 g / cm 3 The protective fluid has a certain shear force, which is carried out through the circulation process to ensure the cleanliness of the wellbore; the agent is a polymer treatment agent. If too much is added, it is easy to form fish-eye agglomerates, which is not conducive to its function. If it is less than 0.1 parts, the adhesion and cuttings are too low and cannot be suspended to remove the cuttings.
[0029] In some embodiments, the completion fluid comprises, by weight: 69-73 parts of water, 23-28 parts of composite salt, 2-4 parts of film-forming solid-free plugging agent, 0.02-0.06 parts of deoxidizer, 0.03-0.04 parts of passivating film-forming corrosion inhibitor, and 0.35-0.5 parts of polymer shearing agent.
[0030] In some embodiments, the composite salt comprises: sodium sulfate, potassium citrate, potassium tartrate and potassium formate, and further, the mass ratio of sodium sulfate, potassium citrate, potassium tartrate and potassium formate is (2-4.5):(1.5-3):(1-3):(2-4). The composite salt using this combination can be applied to loose sandstone screen completion. In some schemes of the prior art, inorganic phosphates and organic phosphates are used, both of which will act on the surface of drill cuttings, resulting in fine dispersion of drill cuttings, which is not conducive to wellbore cleaning. Different from the prior art, the above-mentioned composite salt selected by the present invention does not contain dispersing substances, so it will have good inhibition while not having a dispersing effect.
[0031] In some embodiments, the film-forming solid-free plugging agent is a polyacrylamide film-forming agent. The use of polyacrylamide film-forming agents can be applicable to loose sandstone. In some solutions of the prior art, asphalt film-forming agents are used. However, asphalt materials need to soften at a certain temperature to form an oil film, and for loose sandstone, the temperature is generally low. Even if an asphalt film-forming material of an appropriate temperature is selected, after returning, the asphalt material returns to a solid state due to the decrease in temperature. At this time, the vibration screen is easily blocked, which is not conducive to later processing. Therefore, the present invention selects a polyacrylamide film-forming agent to avoid this problem.
[0032] In some embodiments, the deoxidizer is a complex of disodium stannous citrate and sodium D-ascorbate. In some embodiments, the passivation film-forming corrosion inhibitor is a complex of diethylenetriamine, triethylenetetramine and ethylenediamine. The use of disodium stannous citrate and sodium D-ascorbate complex as a deoxidizer and the selection of diethylenetriamine, triethylenetetramine and ethylenediamine as passivation corrosion inhibitors is because, on the one hand, the above materials have good compatibility, while other materials are prone to performance changes when compounded, and on the other hand, because the protective liquid requires a neutral or alkaline environment, the above materials can achieve this effect.
[0033] In some embodiments, the polymer shearing agent is a synthetic polymer shearing agent. The selection of synthetic polymer shearing agents is mainly based on the following considerations: on the one hand, wells completed with loose sandstone screens are generally drilled in clusters, and if biopolymers are used, bacteria fermentation is easy to occur, resulting in bacterial contamination of the reservoir; on the other hand, synthetic polymers can achieve the reuse of protective fluids, which is cost-effective.
[0034] The present invention also provides a method for preparing the completion fluid as described above, comprising (wherein the amount of each component added is determined according to the formula as described above): adding a polymer-based shearing agent, a film-forming solid-free plugging agent, a deoxidizer, a film-forming corrosion inhibitor and a composite salt into water and stirring the water to obtain the completion fluid;
[0035] Among them, the polymer shearing agent is added first and then the composite salt is added (except for this limitation, the order of adding each reagent can be selected arbitrarily); after adding the polymer shearing agent, stir for a first predetermined time; after adding the film-forming solid-free plugging agent, stir for a second predetermined time; after adding the deoxidizer and the film-forming corrosion inhibitor, stir for a third predetermined time; after adding the composite salt, stir for a fourth predetermined time.
[0036] The reason why salts cannot be added first is to ensure the full dissolution of the polymer shearing agent, because the solubility state of the polymer shearing agent is different in salt water and in fresh water.
[0037] In some embodiments, the polymer-based shearing agent is slowly added at a rate of 0.1-0.2 g / min. The reason for controlling the slow addition of the polymer-based shearing agent is to avoid the formation of fish-eye-like agglomerates due to excessive acceleration, which is not conducive to the dissolution of the polymer.
[0038] In some embodiments, the first predetermined time is 55-65 minutes, the second predetermined time is 10-20 minutes, the third predetermined time is 10-20 minutes, and the fourth predetermined time is 55-65 minutes. For example, the first predetermined time is 60 minutes, the second predetermined time is 15 minutes, the third predetermined time is 15 minutes, and the fourth predetermined time is 60 minutes. The different addition times are to ensure the full dissolution and mixing of each agent. Taking polymer shearing agents as an example, the agent needs sufficient dissolution time to form a solution with the required shear force; taking composite salts as an example, the agent has a large amount and a long dissolution time, so the predetermined time is for full dissolution.
[0039] In summary, the present invention aims at the problems of poor plugging, strong corrosion, insufficient suspension capacity, etc. of the slurry replacement protection fluid in the current reservoir screen completion, and provides a non-solid phase film-forming completion fluid suitable for loose sandstone and its preparation method, and selects film-forming non-solid phase plugging agent, deoxidizer, passivation film-forming corrosion inhibitor, polymer shearing agent and composite salt weighting agent to solve the above problems, so as to achieve safe completion and reservoir protection. After the drilling footage is fully circulated, before the screen is lowered, the completion fluid of the present invention is used to fully displace the drilling fluid in the wellbore to solve the problems of screen blockage and reservoir damage caused by the drilling fluid.
[0040] Compared with the conventional slurry replacement protection fluid, the solid-free slurry replacement protection fluid for loose sandstone reservoir screen completion of the present invention has the following advantages:
[0041] 1. The present invention provides a solid-free film-forming completion fluid suitable for loose sandstone and a preparation method thereof. The technical performance is stable, the rheological parameters are adjustable, and the density can be adjusted within the range of 1.00-1.35 g / cm by using composite salt for weighting. 3 , the system has strong inhibition, and its shale expansion reduction rate can reach more than 60%;
[0042] 2. The present invention provides a solid-free film-forming completion fluid suitable for loose sandstone and a preparation method thereof. The system has no solid phase, which reduces the risk of screen clogging. The increase rate of the flow rate through the screen is controlled within 20%, which is much lower than the increase rate of the screen passage time of other slurry replacement protection fluids (325%). At the same time, it also reduces the damage of the solid phase to the loose sandstone reservoir, and the core permeability recovery value reaches more than 90%.
[0043] 3. The present invention provides a solid-free film-forming completion fluid suitable for loose sandstone and a preparation method thereof, which adopts a solid-free film-forming plugging material and has good plugging performance. The mud cake loss on the experimental medium with a pore size of 2.7μm-20μm is less than 10mL.
[0044] 4. The present invention provides a solid-free film-forming completion fluid suitable for loose sandstone and a preparation method thereof, which has good corrosion resistance, and its corrosion rate meets the requirement of 0.076 mm / a, and meets the corrosion resistance requirements of the whole well replacement fluid for casing and downhole tools.
[0045] The following is a description based on specific embodiments.
[0046] Example 1 (For medium to high porosity and medium to high permeability reservoirs)
[0047] Weigh 80 parts of tap water, slowly add 1.0 part of synthetic polymer shearing agent under stirring, fully dissolve for 60 minutes, add 3.96 parts of polyacrylamide film-forming agent and stir for 15 minutes, then add 0.02 parts of deoxidizer (specifically: disodium stannous citrate and D-sodium ascorbate complex), 0.02 parts of passivating film-forming corrosion inhibitor (specifically: diethylenetriamine, triethylenetetramine and ethylenediamine complex) and stir for 15 minutes, then continue to add 15 parts of composite salt (specifically: sodium sulfate + potassium citrate + sodium tartrate + potassium formate, mass ratio is 4:2.5:1.5:2), mix well and test various properties.
[0048] The solid-free film-forming completion fluid suitable for loose sandstone prepared in this embodiment has adjustable basic properties, does not block the screen, has good inhibition, and has a low corrosion rate. It has a good plugging effect when applied to medium-high porosity and medium-high permeability reservoirs. The plugging filtration loss is only 6.0 mL when the pore size is 10 μm, and the permeability recovery value on the core with a porosity of 22.5 and a permeability of 515 mD can reach 95.1%, which has a good reservoir protection effect.
[0049] Table 1 Conventional performance evaluation of this embodiment
[0050]
[0051]
[0052] As shown in Table 1, the conventional performance of the slurry replacement protection fluid prepared in this example meets the requirements of field application.
[0053] Table 2 Evaluation of the blocking condition of the screen mesh by the present invention
[0054]
[0055] As shown in Table 2, under the conditions of 0.69 MPa and 60°C, the flow rates through the screen for four times in this embodiment are relatively consistent. Compared with the flow rate for the first time, the increase rate of the flow rate through the screen for the fourth time is 17.4%. The screen is taken out for observation, and no obvious solid phase accumulation phenomenon is found on the surface of the screen.
[0056] Table 3 Evaluation of plugging filtration loss in this example
[0057]
[0058] As shown in Table 3, the filter loss of API (filter paper pore size 2.7 μm) mud cake is 0.2 mL higher than that of well slurry, and the filter loss of sand disk (pore size 10 μm) mud cake is 0.4 mL higher than that of well slurry. This shows that this embodiment can achieve good plugging on experimental media with different pore sizes.
[0059] Table 4 Inhibitory evaluation of this example
[0060]
[0061] As shown in Table 4, compared with well slurry and its filtrate, this embodiment has stronger inhibition, which is conducive to application in water-sensitive reservoirs.
[0062] Table 5 Corrosion evaluation of this example
[0063]
[0064] As shown in Table 5, the corrosion evaluation of this embodiment complies with the requirements of the industry standard SY / T 0026-1999, and the test results meet the requirement of the index of 0.076 mm / a.
[0065] Table 6 Effect of protecting oil and gas layers in this embodiment
[0066]
[0067] As shown in Table 6, the core permeability recovery value of this embodiment is 95.1, and the dynamic filtration loss is only 3.5 mL, which has a good reservoir protection effect.
[0068] Example 2 (For high porosity and high permeability reservoirs)
[0069] Weigh 65 parts of tap water, slowly add 0.1 parts of synthetic polymer shearing agent under stirring, fully dissolve for 60 minutes, add 4.76 parts of polyacrylamide film-forming agent and stir for 15 minutes, then add 0.08 parts of deoxidizer (specifically: disodium stannous citrate and D-sodium ascorbate complex), 0.06 parts of passivating film-forming corrosion inhibitor (specifically: diethylenetriamine, triethylenetetramine and ethylenediamine complex) and stir for 15 minutes, then continue to add 30 parts of composite salt (specifically: sodium sulfate + potassium citrate + sodium tartrate + potassium formate, mass ratio is 2.5:1.5:1:4), mix well and test various properties.
[0070] The solid-free film-forming completion fluid suitable for loose sandstone and the preparation method thereof of the present invention have adjustable basic properties, no clogging of the screen, good inhibition, low corrosion rate, and good plugging effect when applied to high-porosity and high-permeability reservoirs. The plugging filtration loss is only 8.6 mL when the pore diameter is 20 μm, and the permeability recovery value on the core with a porosity of 30.5 and a permeability of 1800 mD can reach 91.3%, which has a good reservoir protection effect.
[0071] Table 7 Conventional performance evaluation of this embodiment
[0072]
[0073] As shown in Table 7, the conventional performance of the slurry replacement protection fluid prepared in this embodiment meets the requirements of field application.
[0074] Table 8 Evaluation of the blocking condition of the screen mesh by the present invention
[0075]
[0076] As shown in Table 8, under the conditions of 0.69 MPa and 60°C, the flow rates through the screen for four times in this embodiment are relatively consistent. Compared with the flow rate for the first time, the increase rate of the flow rate through the screen for the fourth time is 3.7%. The screen is taken out for observation, and no obvious solid phase accumulation phenomenon is found on the surface of the screen.
[0077] Table 9 Evaluation of plugging filtration loss in this example
[0078]
[0079] As shown in Table 9, the filter loss of API (filter paper pore size 2.7 μm) mud cake is 0.4 mL lower than that of well slurry, and the filter loss of sand disk (pore size 20 μm) mud cake is 0.2 mL higher than that of well slurry. This shows that this embodiment can achieve good plugging on experimental media with different pore sizes.
[0080] Table 10 Inhibitory evaluation of this example
[0081]
[0082]
[0083] As shown in Table 10, compared with well slurry and its filtrate, this embodiment has stronger inhibition, which is conducive to application in water-sensitive reservoirs.
[0084] Table 11 Corrosion evaluation of this example
[0085]
[0086] As shown in Table 11, the corrosion evaluation of this embodiment complies with the requirements of the industry standard SY / T 0026-1999, and the test results meet the requirement of the index of 0.076 mm / a.
[0087] Table 12 Effect of protecting oil and gas layers in this embodiment
[0088]
[0089] As shown in Table 12, the core permeability recovery value of this embodiment is 91.3, and the dynamic filtration loss is only 4.2 mL, which has a good reservoir protection effect.
[0090] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.
Claims
1. A solid-free film-forming completion fluid suitable for loose sandstone, characterized in that: Calculated by weight, it contains: 65-80 parts of water, 15-30 parts of composite salt, 2-5 parts of film-forming solid-free plugging agent, 0.02-0.08 parts of deoxidizer, 0.02-0.06 parts of passivation film-forming corrosion inhibitor, and 0.1-1.0 parts of polymer shearing agent.
2. The completion fluid according to claim 1, characterized in that: In terms of weight, the completion fluid comprises: 69-73 parts of water, 23-28 parts of composite salt, 2-4 parts of film-forming solid-free plugging agent, 0.02-0.06 parts of deoxidizer, 0.03-0.04 parts of passivating film-forming corrosion inhibitor, and 0.35-0.5 parts of polymer shearing agent.
3. The completion fluid according to claim 1, characterized in that: The composite salt comprises sodium sulfate, potassium citrate, potassium tartrate and potassium formate.
4. The completion fluid according to claim 3, characterized in that: The mass ratio of sodium sulfate, potassium citrate, potassium tartrate and potassium formate is (2-4.5):(1.5-3):(1-3):(2-4).
5. The completion fluid according to claim 1, characterized in that: The film-forming solid-phase-free plugging agent is a polyacrylamide film-forming agent.
6. The completion fluid according to claim 1, characterized in that: The deoxidizer is a complex of disodium stannous citrate and sodium D-ascorbate.
7. The completion fluid according to claim 1, characterized in that: The passivation film-forming corrosion inhibitor is a compound of diethylenetriamine, triethylenetetramine and ethylenediamine.
8. The completion fluid according to claim 1, characterized in that: The polymer shearing agent is a synthetic polymer shearing agent.
9. A method for preparing a completion fluid according to any one of claims 1 to 8, characterized in that: include: Adding a polymer-based shearing agent, a film-forming solid-free plugging agent, a deoxidizer, a film-forming corrosion inhibitor, and a composite salt into water and stirring the water to obtain the completion fluid; wherein, the polymer-based shearing agent is added first and then the composite salt is added; after adding the polymer-based shearing agent, stirring is performed for a first predetermined time; After adding the film-forming solid-free plugging agent, stirring is performed for a second predetermined time; after adding the deoxidizer and the film-forming corrosion inhibitor, stirring is performed for a third predetermined time; after adding the composite salt, stirring is performed for a fourth predetermined time.
10. The method according to claim 9, characterized in that Slowly add a polymer shearing agent at a rate of 0.1-0.2 g / min; and / or The first scheduled time is 55-65 minutes, the second scheduled time is 10-20 minutes, the third scheduled time is 10-20 minutes, and the fourth scheduled time is 55-65 minutes.