Anti-pollution oil displacement spacer fluid and preparation method thereof

Abstract

This invention discloses an anti-fouling oil displacement and isolation fluid and its preparation method. The isolation fluid comprises, by weight, 100 parts water, 2-3 parts suspension stabilizer, 15-30 parts flushing agent, 1-5 parts anti-fouling agent, 0.2-0.6 parts first defoamer, and 60-300 parts weighting agent; the flushing agent comprises, by weight, 10-20 parts hydrophilic emulsifier, 2-5 parts lipophilic emulsifier, 2-5 parts penetrant, 3-6 parts mutual solvent, 0.5-1 part second defoamer, and water. The antifouling agent is at least one of aminotrimethylene phosphonic acid, 2-phospho-1,2,4-tricarboxylic acid butane, hydroxyethylidene diphosphonic acid, and lignin sulfonate. This antifouling-type oil displacement and isolation fluid has good compatibility with oil-based drilling fluids and cement slurries, good suspension stability, and good flushing effect on the well wall mud cake. It has high cementing displacement efficiency, simple preparation method, easy control of reaction conditions, and low cost. It has good application and promotion prospects in cementing construction of oil-based drilling fluid wells.

Description

Technical Field

[0001] This invention relates to the field of pre-flush fluid technology in oil well cementing engineering, and particularly to an anti-fouling oil displacement and isolation fluid and its preparation method. Background Technology

[0002] With the continuous deepening of exploration and development, unconventional wells such as deep wells, ultra-deep wells, extended-reach horizontal wells, and shale oil and shale gas wells are becoming increasingly common. Unconventional oil and gas reservoirs are characterized by large burial depths, thin gas layers, strong heterogeneity, low gas saturation, and complex gas-water relationships. Furthermore, they are generally developed using horizontal wells, resulting in the use of high-density drilling fluids, necessitating the use of suppressive oil-based drilling fluids. However, these drilling fluids, due to their high solids content, use of diesel or white oil as the continuous phase, and the variety of treatment agents, face difficulties in removing mud cake, poor compatibility with cement slurry, and challenges in fluid displacement and flushing, severely impacting cementing quality and interlayer sealing quality.

[0003] When oil-based drilling fluid is completed, a layer of oil-based drilling fluid and loose mud cake adheres to the well wall and casing. The general cementing pre-fluid system has poor compatibility with drilling fluid and cement slurry, and may even have a thick surface, resulting in low displacement efficiency, difficulty in completely displacing the drilling fluid, and poor bonding quality at the cement stone interface, which seriously affects the subsequent volumetric fracturing and oil and gas development. Summary of the Invention

[0004] The purpose of this invention is to provide a pollution-resistant oil displacement and isolation fluid that can effectively isolate oil-based drilling fluid from cement slurry under complex well conditions, ensuring construction safety.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned anti-fouling oil displacement and isolation fluid.

[0006] Therefore, the technical solution of the present invention is as follows:

[0007] An anti-fouling oil displacement and isolation fluid comprises, by weight, 100 parts water, 2-3 parts suspension stabilizer, 15-30 parts flushing agent, 1-5 parts anti-fouling agent, 0.2-0.6 parts primary defoamer, and 60-300 parts weighting agent.

[0008] In the anti-fouling oil displacement fluid, the suspension stabilizer is prepared by mixing 55-60 parts by weight of natural minerals, 15-20 parts by weight of modified stabilizer, 11-13 parts by weight of polymer, 8-13 parts by weight of inorganic salt, and 10-15 parts by weight of silica with a particle size of 50-80 nm. The natural minerals are a mixture of organobentonite and sepiolite. The modified stabilizer is prepared by graft polymerization of sodium p-styrene sulfonate and 2-acrylamide-2-methylpropanesulfonic acid monomers. The polymer is a copolymer of butyl acrylate and acrylonitrile with a molecular weight of 800,000-1,200,000. The inorganic salt is a mixture of sodium tripolyphosphate and water glass.

[0009] The specific formulation and preparation method of the modified precipitate and polymer are disclosed in the patent CN111807748A. In this application, the suspension stabilizer can be BH-S612S type suspension stabilizer produced by PetroChina Bohai Drilling Engineering Co., Ltd.

[0010] In the anti-fouling oil displacement and isolation fluid, the flushing agent comprises, by weight, 10-20 parts of a hydrophilic emulsifier, 2-5 parts of a lipophilic emulsifier, 2-5 parts of a penetrant, 3-6 parts of a mutual solvent, 0.5-1 parts of a secondary defoamer, and water, with the total weight of all components being 100 parts; the hydrophilic emulsifier is a mixture of isomeric alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether, with a weight ratio of 1:(0.4-0.8); the lipophilic emulsifier is a mixture of Span 60 and Span 80, with a weight ratio of 1:(0.5-1); the penetrant is a mixture of succinate sulfonate and a high-temperature penetrant, with a weight ratio of 1:(0.5-1); the mutual solvent is ethylene glycol monobutyl ether; and the secondary defoamer is isooctanol.

[0011] This flushing agent can effectively flush away loose mud cake on the well wall, and with the help of weighting agents and suspension stabilizers, it cleans the loose mud cake through chemical flushing and physical scouring, making the well wall change from oleophilic to hydrophilic, thus improving the bonding quality between cement slurry and the well wall in cementing.

[0012] Preferably, in the rinsing agent, the isomeric alcohol polyoxyethylene ether in the hydrophilic emulsifier is isomeric tridecyl alcohol polyoxyethylene ether, with the structural formula: C 13 H 27 O(CH2CH2O) n H, n = 3~10; alkylphenol polyoxyethylene ether is octylphenol polyoxyethylene ether, its structural formula is: C8H4O(CH2CH2O). n H, n = 10~20.

[0013] Preferably, in the rinsing agent, the succinate sulfonate in the penetrant is sodium dioctyl succinate sulfonate, with the molecular formula: C 20 H 36O7SNa; JFC-M type penetrant is used as the high-temperature penetrant.

[0014] In the antifouling oil displacement and isolation fluid, the antifouling agent is at least one of aminotrimethylene phosphonic acid (ATMP), 2-phospho-1,2,4-tricarboxylic acid butane (PBTCA), hydroxyethylidene diphosphonic acid (HEDP), and lignin sulfonate.

[0015] Preferably, the antifouling agent is a mixture of aminotrimethylenephosphonic acid, 2-phospho-1,2,4-tricarboxylate butane and lignin sulfonate, with a weight ratio of 1:(1-2):(0.5-1).

[0016] Preferably, the first defoamer is a mixture of dimethyl silicone oil and isooctanol, with a weight ratio of 1:0.4 to 1.5. More preferably, the first defoamer is a mixture of dimethyl silicone oil and isooctanol with a weight ratio of 1:0.8.

[0017] Preferably, the weighting agent is at least one of silica powder, barite, and iron ore powder.

[0018] More preferably, the weighting agent is selected from particles with an average particle size of 75 μm and a density of 2.6 g / cm³. 3 The silica powder has an average particle size of 20 μm and a density of 4.2 g / cm³. 3 The barite has an average grain size of 100 μm and a density of 5.0 g / cm³. 3 The average particle size is 45 μm and the density is 7.0 g / cm³. 3 The iron ore powder contains at least two types. The above-mentioned weighting agent combination, through different particle sizes and weighting agent ratios, can achieve a density of the separating liquid ranging from 1.35 to 2.40 g / cm³. 3 It is adjustable within a certain range and also has the effects of low water absorption, good lubricity and stable suspension.

[0019] A method for preparing the above-mentioned anti-fouling oil displacement and isolation fluid, the specific preparation steps of which are as follows:

[0020] S1. Preparation of cleaning agent: Add water to the reaction vessel and heat to 50°C. Add hydrophilic emulsifier to the reaction vessel and stir at 200 r / min for 1 h to fully dissolve the emulsifier in the water. Then, add penetrant to the reaction vessel and stir at 200 r / min for 1 h. Next, add lipophilic emulsifier, mutual solvent and second defoamer in sequence, stir thoroughly for 0.5 h, cool to room temperature and discharge.

[0021] S2. Preparation of anti-fouling oil displacement isolation fluid: Slowly add the suspension stabilizer to the water and mix evenly. Then stir at 4000 r / min for 1-2 min and stop stirring to hydrate for 5-10 min. Then slowly add the weighting agent, anti-fouling agent, cleaning agent and defoamer in sequence. After mixing evenly, stir at 2000 r / min for 1-2 min. Finally, add the defoamer and stir evenly to obtain the anti-fouling oil-based drilling fluid isolation fluid.

[0022] Compared with existing technologies, this anti-fouling oil displacement and isolation fluid has good compatibility with oil-based drilling fluids and cement slurries, good suspension stability, and a good effect on flushing mud cake from the well wall, resulting in high cementing displacement efficiency. At the same time, the preparation method of this anti-fouling oil displacement and isolation fluid is simple, the reaction conditions are easy to control, and the cost is low, making it a promising candidate for application and promotion in cementing operations of oil-based drilling fluid wells. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments, but the following embodiments are not intended to limit the present invention in any way. In the following embodiments and comparative examples, the amounts of each component are parts by weight.

[0024] Example 1

[0025] A substance with a density of 1.35 g / cm³ 3 The anti-fouling oil displacement and isolation fluid is prepared by the following method: 3 parts of a suspending stabilizer are slowly added to 100 parts of water, and after thorough mixing, the mixture is stirred at 4000 rpm for 2 minutes in a Warlin stirrer. Stirring is then stopped, and the mixture is allowed to hydrate for 10 minutes. Next, 60 parts of a weighting agent are slowly added, followed by 1 part of an anti-fouling agent and 15 parts of a flushing agent. After thorough mixing, the mixture is stirred at 2000 rpm for 1 minute. Finally, 0.2 parts of a first defoamer are added, and the mixture is stirred until homogeneous.

[0026] The suspension stabilizer is BH-S612S type suspension stabilizer produced by PetroChina Bohai Drilling Engineering Co., Ltd.

[0027] The weighting agent consists of 40 parts with an average particle size of 20 μm and a density of 4.2 g / cm³. 3 Barite and 20 parts with an average particle size of 75 μm and a density of 2.6 g / cm³ 3 It is made from a mixture of silica powder;

[0028] The antifouling agent is a mixture of aminotrimethylenephosphonic acid, 2-phospho-1,2,4-tricarboxylate butane, and lignin sulfonate in a ratio of 1:1:0.5. The specific preparation method is as follows: aminotrimethylenephosphonic acid, 2-phospho-1,2,4-tricarboxylate butane, and lignin sulfonate are added to a reaction vessel and stirred at 200 r / min for 1 to 1.5 h until the lignin sulfonate is completely dissolved, and then the product is discharged.

[0029] The rinsing agent is composed of 10 parts hydrophilic emulsifier, 2 parts lipophilic emulsifier, 2 parts penetrant, 3 parts miscible solvent, 0.5 parts defoamer, and 82.5 parts water. The hydrophilic emulsifier is a mixture of isomeric alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether in a weight ratio of 1:0.4; the lipophilic emulsifier is a mixture of Span 60 and Span 80 in a weight ratio of 1:0.5; the penetrant is a mixture of succinate sulfonate and high-temperature penetrant JFC-M in a weight ratio of 1:0.5; and the second defoamer is isooctanol. The specific preparation method is as follows: water is added to a reaction vessel and heated to 50°C. The hydrophilic emulsifier is added to the reaction vessel and stirred at 200 r / min for 1 hour to fully dissolve the emulsifier in the water. Then, the penetrant is added to the reaction vessel and stirred at 200 r / min... Stir for 1 hour; then, add the lipophilic emulsifier, the mutual solvent, and the second defoamer in sequence, stir thoroughly for 0.5 hours, cool to room temperature, and discharge.

[0030] The first defoamer is a mixture of dimethyl silicone oil and isooctanol in a weight ratio of 1:0.4.

[0031] Example 2

[0032] A substance with a density of 1.70 g / cm³ 3 The anti-fouling oil displacement and isolation fluid is prepared by the following method: 2.6 parts of a suspending stabilizer are slowly added to 100 parts of water, and after thorough mixing, the mixture is stirred at 4000 rpm for 2 minutes in a Warlin stirrer. Stirring is then stopped, and the mixture is allowed to hydrate for 10 minutes. Next, 150 parts of a weighting agent are slowly added, followed by 2 parts of an anti-fouling agent and 20 parts of a flushing agent. After thorough mixing, the mixture is stirred at 2000 rpm for 1 minute. Finally, 0.2 parts of a first defoamer are added, and the mixture is stirred until homogeneous.

[0033] The suspension stabilizer is BH-S612S type suspension stabilizer produced by PetroChina Bohai Drilling Engineering Co., Ltd.

[0034] The weighting agent consists of 120 parts with an average particle size of 20 μm and a density of 4.2 g / cm³. 3 Barite and 30 parts with an average particle size of 75 μm and a density of 2.6 g / cm³ 3 A mixture of silica powder;

[0035] The antifouling agent is a mixture of aminotrimethylenephosphonic acid, 2-phospho-1,2,4-tricarboxylate butane, and lignin sulfonate in a ratio of 1:1.2:0.6; its preparation method is the same as in Example 1.

[0036] The rinsing agent is composed of 12 parts hydrophilic emulsifier, 3 parts lipophilic emulsifier, 3 parts penetrant, 4 parts miscible solvent, 0.8 parts defoamer, and 77.2 parts water. The hydrophilic emulsifier is a mixture of isomeric alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether in a weight ratio of 1:0.5. The lipophilic emulsifier is a mixture of Span 60 and Span 80 in a weight ratio of 1:0.6. The penetrant is a mixture of succinate sulfonate and high-temperature penetrant JFC-M in a weight ratio of 1:0.6. The second defoamer is isooctanol. Its preparation method is the same as in Example 1.

[0037] The first defoamer is a mixture of dimethyl silicone oil and isooctanol in a weight ratio of 1:0.8.

[0038] Example 3

[0039] A substance with a density of 2.0 g / cm³ 3 The anti-fouling oil displacement and isolation fluid is prepared by the following method: 2.4 parts of a suspending stabilizer are slowly added to 100 parts of water, and after thorough mixing, the mixture is stirred at 4000 rpm for 2 minutes in a Warlin stirrer. Stirring is then stopped, and the mixture is allowed to hydrate for 10 minutes. Next, 200 parts of a weighting agent are slowly added, followed by 3 parts of an anti-fouling agent and 25 parts of a flushing agent. After thorough mixing, the mixture is stirred at 2000 rpm for 1 minute. Finally, 0.2 parts of a first defoamer are added, and the mixture is stirred until homogeneous.

[0040] The suspension stabilizer is BH-S612S type suspension stabilizer produced by PetroChina Bohai Drilling Engineering Co., Ltd.

[0041] The weighting agent consists of 100 parts with an average particle size of 20 μm and a density of 4.2 g / cm³. 3 Barite and 120 parts with an average particle size of 100 μm and a density of 5.0 g / cm³ 3 A mixture of iron ore powder;

[0042] The antifouling agent is a mixture of aminotrimethylenephosphonic acid, 2-phospho-1,2,4-tricarboxylate butane, and lignin sulfonate in a ratio of 1:1.5:0.8; its preparation method is the same as in Example 1.

[0043] The rinsing agent is composed of 16 parts hydrophilic emulsifier, 4 parts lipophilic emulsifier, 4 parts penetrant, 5 parts miscible solvent, 0.8 parts defoamer, and 70.2 parts water. The hydrophilic emulsifier is a mixture of isomeric alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether in a weight ratio of 1:0.6. The lipophilic emulsifier is a mixture of Span 60 and Span 80 in a weight ratio of 1:0.8. The penetrant is a mixture of succinate sulfonate and high-temperature penetrant JFC-M in a weight ratio of 1:0.8. The second defoamer is isooctanol. Its preparation method is the same as in Example 1.

[0044] The first defoamer is a mixture of dimethyl silicone oil and isooctanol in a weight ratio of 1:1.

[0045] Example 4

[0046] A substance with a density of 2.40 g / cm³ 3 The anti-fouling oil displacement and isolation fluid is prepared by the following method: 2.0 parts of a suspending stabilizer are slowly added to 100 parts of water, and after thorough mixing, the mixture is stirred at 4000 rpm for 2 minutes in a Warlin stirrer. Stirring is then stopped, and the mixture is allowed to hydrate for 10 minutes. Next, 300 parts of a weighting agent are slowly added, followed by 5 parts of an anti-fouling agent and 30 parts of a flushing agent. After thorough mixing, the mixture is stirred at 2000 rpm for 1 minute. Finally, 0.2 parts of a first defoamer are added, and the mixture is stirred until homogeneous.

[0047] The suspension stabilizer is BH-S612S type suspension stabilizer produced by PetroChina Bohai Drilling Engineering Co., Ltd.

[0048] The weighting agent consists of 100 parts of an average particle size of 100 μm and a density of 5.0 g / cm³. 3 Iron ore powder, 200 parts, with an average particle size of 45μm and a density of 7.0g / cm³. 3 A mixture of iron ore powder;

[0049] The antifouling agent is a mixture of aminotrimethylenephosphonic acid, 2-phospho-1,2,4-tricarboxylate butane, and lignin sulfonate in a ratio of 1:2:1; its preparation method is the same as in Example 1.

[0050] The rinsing agent is composed of 20 parts hydrophilic emulsifier, 5 parts lipophilic emulsifier, 5 parts penetrant, 6 parts miscible solvent, 1 part defoamer, and 63 parts water. The hydrophilic emulsifier is a mixture of isomeric alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether in a weight ratio of 1:0.8. The lipophilic emulsifier is a mixture of Span 60 and Span 80 in a weight ratio of 1:1. The penetrant is a mixture of succinate sulfonate and high-temperature penetrant JFC-M in a weight ratio of 1:1. The second defoamer is isooctanol. Its preparation method is the same as in Example 1.

[0051] The first defoamer is a mixture of dimethyl silicone oil and isooctanol in a weight ratio of 1:1.5.

[0052] Comparative Example 1

[0053] A substance with a density of 1.70 g / cm³ 3 The anti-fouling oil displacement and isolation fluid is prepared by the following method:

[0054] Slowly add 2.6 parts of suspension stabilizer to 100 parts of water, mix evenly, and then stir at 4000 r / min for 2 min in a Waring mixer. Stop stirring and hydrate for 10 min. Then slowly add 150 parts of weighting agent, followed by 2 parts of antifouling agent and 20 parts of water-based isolation fluid flushing agent. Mix evenly and stir at 2000 r / min for 1 min. Finally, add 0.2 parts of the first defoamer and stir evenly to obtain the solution. The only difference between Comparative Example 1 and Example 2 is that the water-based isolation fluid flushing agent is used instead of the original cleaning agent. Specifically, the water-based isolation fluid flushing agent is BH-Q812L produced by PetroChina Bohai Drilling Second Cementing Company.

[0055] Comparative Example 2

[0056] A substance with a density of 1.70 g / cm³ 3 The anti-fouling oil displacement and isolation fluid is prepared by the following method: 2.6 parts of suspension stabilizer are slowly added to 100 parts of water, mixed evenly, and then stirred at 4000 r / min for 2 min in a Waring agitator. After stirring, the mixture is hydrated for 10 min, then 150 parts of weighting agent are slowly added, followed by 2 parts of antifouling agent and 20 parts of flushing agent. After mixing evenly, the mixture is stirred at 2000 r / min for 1 min, and finally 0.2 parts of the first defoamer are added and stirred evenly to obtain the solution. The only difference between Comparative Example 2 and Example 2 is that a retarder is used instead of the original antifouling agent. Specifically, the retarder used is BH-R102L produced by PetroChina Bohai Drilling Second Cementing Company.

[0057] Performance testing:

[0058] First, the relevant properties of the isolation fluids prepared in Examples 1-4 and Comparative Examples 1-2 were tested, including: density, free liquid volume, density difference, PV, YP, and rinsing efficiency; the specific test results are shown in Table 1 below.

[0059] The prepared isolation solution was loaded into a high-temperature and high-pressure thickener, and the temperature was increased by program. The solution was stirred at 120°C for 0.5 hours. The solution was then poured into a 500 mL graduated cylinder and allowed to stand for 2 hours to measure the density difference and free liquid.

[0060] The rheological properties of the release fluid were determined using a Van denso six-speed rotational viscometer. Specifically, the prepared release fluid was pre-set at 120°C for 1 hour, and then its rheological properties were measured. The cement slurry used in this test had a density of 1.90 g / cm³. 3 The cement grout used was a release agent prepared in Example 2 with a density of 1.70 g / cm³. 3 The isolation fluid used is a drilling fluid with a density of 1.60 g / cm³. 3 White oil-based drilling fluid;

[0061] The test method for flushing efficiency of the flushing fluid is as follows: The specific test results of the above-mentioned properties are shown in Table 1 below.

[0062] The rotating outer barrel of the rotational viscometer is weighed, and its mass W0 (g) is recorded. Two-thirds of the rotating outer barrel, below the scale mark, is immersed in white oil-based drilling fluid and stirred at 100 rpm for 1 minute, followed by immersion for 20 minutes. The drilling fluid tank is then lowered to expose the rotating outer barrel, which is allowed to drip for 3 minutes before being removed and weighed, and its mass W1 (g) is recorded. A flushing solution at a specific temperature is filled into the sample cup of the rotational viscometer, with the liquid level reaching the scale mark. The rotating outer barrel is then placed into the sample cup containing the flushing solution, ensuring the scale mark of the rotating barrel is aligned with the viscosity. The rinsing solution in the sample cup is level. The rotational viscometer is started and rotated at 200 r / min for 3 min. The rinsing solution is poured out, and water is added to the mark. The sample is rinsed at 200 r / min for 1 min to remove the residual isolation liquid on the rotating drum. After dripping for 3 min, the sample rotating drum is removed and its mass W2 (g) is weighed. The rinsing efficiency is calculated using the formula: η=(W1-W2) / (W1-W0)*100%, where η is the rinsing efficiency, %, W0 is the mass of the rotating outer drum, g; W1 is the mass of the mixed sample and the rotating outer drum before rinsing, g; and W2 is the mass of the mixed sample and the rotating outer drum after rinsing, g.

[0063] Table 1:

[0064]

[0065]

[0066] As can be seen from the test results in Table 1, at 120℃, the density range of the isolation fluids prepared in Examples 1-4 is 1.30-2.40 g / cm³. 3Between these samples, the density difference between the upper and lower layers and the free fluid, measured after standing for 2 hours, remained within a small range, and the rheological properties were good. The flushing efficiency of the oil-based drilling fluid was tested to be greater than 95%. In contrast, in Comparative Example 1, when the oil-based flushing fluid was replaced with a water-based flushing fluid, the flushing efficiency was only 33.2%. In the flushing efficiency experiment of the oil-based drilling fluid, the flushing efficiency of the isolation fluid increased with increasing temperature and remained above 95%, demonstrating high flushing efficiency that was not affected by temperature.

[0067] In addition, to verify the effect of adding the release agent on the compatibility of cement slurry and mud, the compatibility performance of cement slurry, release agent and mud was tested. The specific test results are shown in Table 2 below.

[0068] Table 2: Compatibility test performance of cement slurry, release fluid and mud (test temperature 150℃)

[0069]

[0070] The results shown in Table 2 indicate that when cement slurry and drilling fluid are mixed in a 1:1 ratio, flocculation occurs, making it impossible to measure rheological data. However, when using the isolating fluid prepared in Example 2, and mixing cement slurry, isolating fluid, and drilling fluid in ratios of 1:1:1 and 7:2:1 respectively, the cement slurry also exhibits varying degrees of thickening, but the slurry remains fluid. In contrast, using the isolating fluid prepared in Comparative Example 2, severe thickening occurs at ratios of cement slurry:isolating fluid:drilling fluid of 1:1:1 and 7:2:1, making rheological data unmeasurable. Only when only 5% drilling fluid is added can rheological data be measured, but the dynamic shear force of the mixed slurry is also relatively high, seriously affecting construction safety.

[0071] Furthermore, considering that drilling fluid, release fluid, and mud may mix simultaneously and in a certain proportion when displacement is insufficient, it is necessary to conduct experiments on the rheological compatibility of cement slurry, release fluid, and mud to fully ensure the safety of downhole operations and in accordance with industry standards. Specifically, the rheological compatibility test method was to measure the thickening time of cement slurry, release fluid, and mud after mixing at 120°C. The specific test results are shown in Table 3.

[0072] Table 3: Thickening test performance of cement slurry, release fluid and mud mixture (120℃)

[0073] Cement grout (%) mud(%) Isolation fluid (%) Thickening time (min) 100 0 0 202 95 0 5 252 75 0 25 ＞300 50 0 50 ＞300 70 10 20 ＞300

[0074] As shown in Table 3, the thickening time of pure cement is 202 min. When the ratio of cement slurry to release agent is 95:5, the thickening time of the mixture is 252 min. However, when the ratios of cement slurry to release agent are 3:1, 1:1, and 7:2:1, the corresponding thickening times are all greater than 300 min. It can be seen that the release agent can effectively slow down the setting of cement slurry and meet the requirements for safe on-site construction.

Claims

1. A pollution-resistant oil displacement and isolation fluid, characterized in that, The mixture comprises, by weight, 100 parts water, 2-3 parts suspension stabilizer, 15-30 parts flushing agent, 1-5 parts antifoaming agent, 0.2-0.6 parts primary defoamer, and 60-300 parts weighting agent; wherein, the suspension stabilizer is BH-S612S type suspension stabilizer produced by PetroChina Bohai Drilling Engineering Co., Ltd.; the flushing agent comprises, by weight, 10-20 parts hydrophilic emulsifier, 2-5 parts lipophilic emulsifier, 2-5 parts penetrant, 3-6 parts mutual solvent, 0.5-1 part secondary defoamer, and water, with the sum of the weights of all components being 100 parts; the hydrophilic emulsifier is a mixture of isomeric alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether, with a weight ratio of 1:(0.4-0.8); the lipophilic emulsifier is a mixture of Span 60 and Span 80, with a weight ratio of 1: (0.5~1); the penetrant is a mixture of succinate sulfonate and high-temperature penetrant, with a weight ratio of 1:(0.5~1); the succinate sulfonate is sodium dioctyl succinate sulfonate, and the high-temperature penetrant is JFC-M type penetrant; the miscible solvent is ethylene glycol monobutyl ether; the antifoaming agent is at least one of aminotrimethylenephosphonic acid, 2-phospho-1,2,4-tricarboxylate butane, hydroxyethylidene diphosphonic acid, and lignin sulfonate; the antifoaming agent is a mixture of aminotrimethylenephosphonic acid, 2-phospho-1,2,4-tricarboxylate butane and lignin sulfonate, with a weight ratio of 1:(1~2):(0.5~1); the first defoamer is a mixture of dimethyl silicone oil and isooctanol, with a weight ratio of 1:(0.4~1.5); the second defoamer is isooctanol.

2. The anti-fouling oil displacement and isolation fluid according to claim 1, characterized in that, In hydrophilic emulsifiers, the isomeric alcohol polyoxyethylene ether is isomeric tridecyl alcohol polyoxyethylene ether, and its structural formula is: C 13 H 27 O(CH2CH2O) n H, n=3~10; alkylphenol polyoxyethylene ether is octylphenol polyoxyethylene ether, its structural formula is: C8H4O(CH2CH2O). n H, n=10~20.

3. The pollution-resistant oil displacement spacer fluid of claim 1, wherein, The weighting agent is at least one of silica powder, barite, and iron ore powder.

4. A method for preparing the anti-pollution oil displacement spacer fluid according to any one of claims 1 to 3, characterized in that, The specific steps are as follows: S1. Preparation of cleaning agent: Add water to the reaction vessel and heat to 50°C. Add hydrophilic emulsifier to the reaction vessel and stir at 200 r / min for 1 h to fully dissolve the emulsifier in the water. Then, a penetrant was added to the reactor and stirred at 200 r / min for 1 h; next, the lipophilic emulsifier, the mutual solvent, and the second defoamer were added in sequence, stirred thoroughly for 0.5 h, cooled to room temperature, and then discharged. S2. Preparation of anti-fouling oil displacement isolation fluid: Slowly add the suspension stabilizer to the water and mix evenly. Then stir at 4000 r / min for 1-2 min and stop stirring to hydrate for 5-10 min. Then slowly add the weighting agent, anti-fouling agent, cleaning agent and defoamer in sequence. After mixing evenly, stir at 2000 r / min for 1-2 min. Finally, add the defoamer and stir evenly to obtain the anti-fouling oil-based drilling fluid isolation fluid.

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