Well cementation prepad fluid for oil-based drilling fluid as well as preparation method and application of well cementation prepad fluid

Abstract

The invention provides well cementation prepad fluid for oil-based drilling fluid as well as a preparation method and application of the well cementation prepad fluid. The well cementation prepad fluid comprises the following raw materials: water, an anionic surfactant accounting for 0.1%-10% of the total mass of the water, a nonionic surfactant accounting for 0.1%-15% of the total mass of the water, a coupling agent accounting for 0.1%-2.5% of the total mass of the water, a buffering agent and / or a chelating agent accounting for 0.2%-3% of the total mass of the water, and a suspending agent accounting for 0.1%-3.0% of the total mass of the water, a defoaming agent accounting for 0.1%-3.0% of the total mass of the water; wherein the coupling agent is an amino alkyl type silane coupling agent. The prepared well cementation prepad fluid can effectively remove oil-phase substances of a casing pipe and a well wall when an oil-based drilling fluid is used for drilling, the interface cementation quality is improved, and the cement sheath packing capacity and the well cementation quality are guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of well cementing in the oil and gas industry, and particularly relates to a well cementing preflush fluid for oil-based drilling fluids, a preparation method thereof, and a performance evaluation method thereof. Background Art

[0002] With the large-scale development of high-temperature deep wells, shale gas horizontal wells, etc., oil-based drilling fluids are widely used due to their many advantages such as strong inhibition, high temperature resistance, pollution resistance, and lubricity. However, when well cementing, the casing and the wellbore wall in the annulus are adhered with oil-based drilling fluids. When the cement slurry contacts the drilling fluid, problems such as a sharp increase in consistency, loss of fluidity, inability of the cement slurry to effectively bond with the casing and the wellbore wall, and difficulty in curing of the cement slurry mixed with oil-based drilling fluids easily occur, seriously threatening construction safety and well cementing quality. Therefore, it is necessary to use a preflush fluid to ensure construction safety and well cementing quality.

[0003] In the cementing operation, the preflush fluid separates the cement slurry and the drilling fluid, prevents contact pollution between the cement slurry and the drilling fluid, improves the displacement efficiency of the cement slurry, improves the bonding quality of the casing-cement sheath-wellbore wall / casing, and enhances the ability of the cement sheath to seal off formation fluids. The preflush fluid includes a flushing fluid and a spacer fluid, and there is no clear distinction standard. In terms of function, the flushing fluid focuses on diluting the drilling fluid, flushing the bonding interface, removing annulus residues such as mud cakes and oil stains, and improving the bonding quality; the function of the spacer fluid focuses on preventing contact pollution between the drilling fluid and the cement slurry, and also has functions such as suspending solid particles, preventing lost circulation, and wellbore collapse.

[0004] Currently, oil-based drilling fluids are widely used. When well cementing, it is necessary to use a preflush fluid specifically to prevent contact pollution, thereby improving the flushing efficiency and displacement efficiency, and effectively ensuring the tight bonding degree between the casing, wellbore wall interface and the cement sheath. Therefore, there is a current need for a well cementing preflush fluid for oil-based drilling fluids and a performance evaluation method for its performance indicators. Summary of the Invention

[0005] To solve the above technical problems, the object of the present invention is to provide a well cementing preflush fluid for oil-based drilling fluids, a preparation method thereof, and a performance evaluation method thereof. The well cementing preflush fluid prepared by simultaneously using an anionic surfactant and a non-ionic surfactant and adding a small amount of coupling agent can improve the flushing efficiency and the interfacial bonding quality during well cementing.

[0006] To achieve the above object, the present invention provides a preflush fluid for cementing in oil-based drilling fluids. The raw material composition of the preflush fluid includes: water, an anionic surfactant accounting for 0.1%-10% of the total mass of water, a nonionic surfactant accounting for 0.1%-15% of the total mass of water, a coupling agent accounting for 0.1%-2.5% of the total mass of water, a buffer and / or chelating agent accounting for 0.2%-3% of the total mass of water, a suspending agent accounting for 0.1%-3.0% of the total mass of water, and an antifoaming agent accounting for 0.1%-3.0% of the total mass of water.

[0007] According to a specific embodiment of the present invention, preferably, the coupling agent is an aminoalkyl silane coupling agent. Aminoalkyl silane coupling agents have better solubility in an alkaline environment, and other types of coupling agents are prone to precipitation and precipitation.

[0008] According to a specific embodiment of the present invention, preferably, the anionic surfactant includes one or a combination of two or more of carboxylate type, sulfonate type, sulfate type, sulfate ester type, phosphate type, and phosphate ester type; more preferably, the anionic surfactant includes one or a combination of two or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, oleate, and triethanolamine oleate. Anionic surfactants have a wide variety, low price, and strong emulsifying ability.

[0009] In some specific embodiments, preferably, the addition amount of the anionic surfactant is 0.1%-3.5% of the total mass of water.

[0010] According to a specific embodiment of the present invention, preferably, the nonionic surfactant includes one or a combination of two or more of polyoxyethylene-based, fatty alcohol polyoxyethylene ethers (AEO series), and alkylphenol polyoxyethylene ethers (OP series); more preferably, the polyoxyethylene-based includes sorbitan monooleate polyoxyethylene ethers (Tween series). Nonionic surfactants have good salt tolerance, acid tolerance, and alkali tolerance.

[0011] In some specific embodiments, preferably, the addition amount of the nonionic surfactant is 0.2%-5.0% of the total mass of water.

[0012] For oil-based drilling fluids, surfactants need to be added to the pre-flush fluid for cementing. The main functions are as follows: (1) Surfactants have a penetration and emulsification effect on the oil stains, oil films and residual drilling fluids at the interface between the casing and the wellbore, making these attachments easy to peel off and easy to be displaced by the cement slurry. At the same time, the oil-phase substances are wrapped in the pre-flush fluid, forming an oil-in-water (O / W) type fluid and then displaced from the annulus to improve the displacement efficiency; (2) Surfactants significantly reduce the surface tension of the interface, making the interface water-wetting and improving the interfacial bonding strength. Since both the drilling fluid and the cement slurry are alkaline liquids, anionic surfactants and non-ionic surfactants are used in combination.

[0013] According to specific embodiments of the present invention, preferably, the aminoalkyl silane coupling agent includes one or a combination of two or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and N-aminoethyl-γ-aminopropyltriethoxysilane. To improve the mechanical properties of the cement stone, organic materials such as rubber, resin, and fiber are usually added to the cement slurry. Therefore, adding a small amount of coupling agent to the pre-flush fluid can improve the bonding quality between the cement stone and the casing and the wellbore.

[0014] In some specific embodiments, preferably, the addition amount of the aminoalkyl silane coupling agent is 0.2%-0.8% of the total mass of water.

[0015] According to specific embodiments of the present invention, preferably, the HLB values of the anionic surfactant and the non-ionic surfactant are 8-20, preferably 13-18.

[0016] According to specific embodiments of the present invention, preferably, the density of the pre-flush fluid is 1.00-2.30 g / cm 3 , and the density is adjusted by adding weighting agents.

[0017] According to specific embodiments of the present invention, preferably, the buffer includes one or a combination of two or more of carbonates, bicarbonates, phosphates, dihydrogen phosphates, ammonium salts, acetates, sodium tripolyphosphate, sodium hexametaphosphate, and sodium pyrophosphate; the chelating agent is ethylenediaminetetraacetic acid. Among them, the above phosphate substances can also be used as chelating agents.

[0018] According to specific embodiments of the present invention, preferably, the suspending agent is a thickening material, including one or a combination of two or more of xanthan gum, acrylamide polymers, and sodium carboxymethyl cellulose.

[0019] According to specific embodiments of the present invention, preferably, the weighting agents include one or a combination of two or more of manganese oxide, iron ore powder, magnetite, barite, calcium carbonate, microsilica, and slag.

[0020] According to the specific embodiments of the present invention, preferably, the defoamer is tributyl phosphate and / or silicone; more preferably, the silicone is dimethyl silicone oil.

[0021] According to the specific embodiments of the present invention, preferably, the raw material composition of the preflush fluid for cementing further includes a dispersant accounting for 0.1%-2.0% of the total mass of water; more preferably, the dispersant is a ketone-aldehyde condensate.

[0022] According to the specific embodiments of the present invention, preferably, the flushing efficiency of the preflush fluid for cementing on the oil-based drilling fluid is greater than 90%.

[0023] According to the specific embodiments of the present invention, preferably, after the preflush fluid for cementing flushes the surface of the N80 steel sheet adhered with the oil-based drilling fluid, the contact angle of the surface of the N80 steel sheet is less than 10°.

[0024] According to the specific embodiments of the present invention, preferably, after the preflush fluid for cementing and the oil-based drilling fluid are mixed evenly at a volume ratio of 1:9, the demulsification voltage of the obtained mixed solution is less than or equal to 200V. When the preflush fluid for cementing is used for the oil-based drilling fluid, it is necessary to quickly destroy the water-in-oil (W / O) form and stability of the oil-based drilling fluid. Since the higher the demulsification voltage of the oil-based drilling fluid, the better its stability, therefore, it is necessary to reduce the demulsification voltage of the mixed solution, which is used as an index to evaluate the performance effect of the preflush fluid for cementing.

[0025] The present invention also provides a preparation method of the above-mentioned preflush fluid for cementing, wherein the preparation method includes:

[0026] S1. Completely dissolve the mixture of the anionic surfactant and the non-ionic surfactant in water to obtain a surfactant solution;

[0027] S2. After fully dissolving the suspending agent in water, first add the surfactant solution, then add the buffer and / or chelating agent for mixing. After the pH value of the mixed solution is stable, add the coupling agent, stir evenly, and then add the weighting agent to the appropriate density of the preflush fluid. During the weighting process, add the defoamer at the same time, and finally obtain the preflush fluid for cementing. The addition order of the raw materials is very important and needs to be added according to the order in step S2. In particular, it is necessary to first add the surfactant solution and the buffer, and then add the coupling agent after the pH value in the solution is stable to prevent the coupling agent from precipitating due to pH changes.

[0028] According to the specific embodiments of the present invention, preferably, the preparation method further includes adding the dispersant after adding the coupling agent.

[0029] In the above preparation method, preferably, the preparation method includes:

[0030] (1) Dissolve a mixture of an anionic surfactant accounting for 0.1% - 10% (preferably 0.1% - 3.5%) of the total mass of water and a non-ionic surfactant accounting for 0.1% - 15% (preferably 0.2% - 5.0%) of the total mass of water in water for 2 - 3 min until completely dissolved to prepare a surfactant solution;

[0031] (2) After fully dissolving a suspending agent accounting for 0.1% - 3.0% of the total mass of water in water, sequentially add the prepared surfactant solution, a buffer and / or chelating agent accounting for 0.2% - 3% of the total mass of water for mixing. After the pH value of the mixed solution is stable, add a coupling agent accounting for 0.1% - 2.5% (preferably 0.2% - 0.8%) of the total mass of water, and then add a dispersant accounting for 0.1% - 2.0% of the total mass of water. Stir evenly and then add a weighting agent until the density of the preflush fluid is 1.00 - 2.30 g / cm 3 , and add an antifoaming agent accounting for 0.1% - 3.0% of the total mass of water during the weighting process to finally obtain a preflush fluid for well cementing.

[0032] The present invention also provides the application of the above-mentioned preflush fluid for well cementing in the technical field of well cementing, which is used for oil-based drilling fluids.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The preflush fluid for well cementing prepared by the present invention can effectively remove the oil-phase substances on the casing and wellbore wall during drilling with oil-based drilling fluids, improve the interfacial bonding quality, and ensure the cement sheath sealing ability and well cementing quality.

[0035] (2) The flushing efficiency of the preflush fluid for well cementing prepared by the present invention is greater than 90%, the surface contact angle after flushing an N80 steel sheet is less than 10°, and the demulsification voltage after mixing with the oil-based drilling fluid is less than or equal to 200 V. Detailed Embodiments

[0036] For a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the implementable scope of the present invention.

[0037] In the examples and comparative examples of the present invention, sodium dodecyl sulfate was selected as the anionic surfactant; Tween 80 in sorbitan monooleate polyoxyethylene ether (Tween series) and AEO-9 in fatty alcohol polyoxyethylene ether (AEO series) were selected as the non-ionic surfactants; sodium carboxymethyl cellulose (CMC-Na) with medium viscosity was selected as the suspending agent; γ-aminopropyltrimethoxysilane was selected as the coupling agent; sodium carbonate was selected as the buffer; dimethyl silicone oil (SD52) was selected as the defoaming agent; weighting agents included microsilica, slag, magnetite and barite; ketone-aldehyde condensate (SXY) was selected as the dispersant.

[0038] The raw material compositions of the preflush fluids for cementing in Examples 1-5 are shown in Table 1, and the preparation process of the preflush fluids for cementing includes:

[0039] (1) According to the raw material composition ratio in Table 1, the mixture of the anionic surfactant and the non-ionic surfactant was dissolved in water for 2-3 minutes until completely dissolved to prepare a surfactant solution;

[0040] (2) According to the raw material composition ratio in Table 1, after the suspending agent was fully dissolved in water, the prepared surfactant solution and the buffer were added in sequence for mixing. After the pH value of the mixed solution was stabilized, the coupling agent was added, and after stirring evenly, the weighting agent was added to an appropriate density of the preflush fluid. The defoaming agent was added simultaneously during the weighting process to finally obtain the preflush fluid for cementing;

[0041] Among them, in Examples 2-5, a dispersant was further added after the coupling agent was added.

[0042] Table 1. Raw material compositions of the preflush fluids for cementing in Examples 1-5

[0043]

[0044]

[0045] The raw material compositions of the preflush fluids for cementing in Comparative Examples 1-3 are shown in Table 2. The preparation process of the preflush fluids for cementing is the same as that of the examples except for the difference in the ratio of the raw material composition;

[0046] Among them, the anionic surfactant was not added in Comparative Examples 1-2; the coupling agent was not added in Comparative Example 3.

[0047] Table 2. Raw material compositions of the preflush fluids for cementing in Comparative Examples 1-3

[0048]

[0049] Next, the performances of the preflush fluids for cementing prepared in Examples 1-5 and Comparative Examples 1-3 were tested, and the test process and results are as follows:

[0050] (1) Flushing efficiency: Using a rotational viscometer, completely immerse the rotor in the oil-based drilling fluid and weigh the rotor before and after immersion. Then, fill the cup with the preflush fluids prepared in Examples 1-5 and Comparative Examples 1-3 respectively, and use them as flushing fluids to measure the flushing efficiency. Set the speed at 600 r / min. After flushing for 10 min, weigh the mass of the rotor after flushing respectively. By observing the flushing effect, the flushing efficiencies of the preflush fluids prepared in Examples 1-5 and Comparative Examples 1-3 can be calculated respectively. The results are shown in Table 3.

[0051] (2) Surface contact angle: Take 9 N80 steel sheets (S0, S1, S2, S3, S4, S5, S6, S7, S8) of the same material and immerse them in the oil-based drilling fluid for 4 h respectively. Take out the steel sheet S0 from the drilling fluid, blow away the excess mud on the surface of the steel sheet with compressed air, place the steel sheet on the contact angle analyzer, drop clear water on the surface of the steel sheet, and measure the contact angle of the steel sheet S0. After taking out the steel sheets S1, S2, S3, S4, S5, S6, S7, S8 in turn, flush the corresponding steel sheets with the preflush fluids prepared in Examples 1-5 and Comparative Examples 1-3 respectively for 10 min, then blow away the excess liquid on the surface of the steel sheet with compressed air, and drop clear water on the surface of the steel sheet in the same way to measure the contact angles of the steel sheets S1, S2, S3, S4, S5, S6, S7, S8. The results are shown in Table 3.

[0052] (3) Demulsification voltage: After mixing the preflush fluids prepared in Examples 1-5 and Comparative Examples 1-3 with the oil-based drilling fluid evenly at a volume ratio of 1:9 respectively, test the demulsification voltages of their respective mixtures. The results are shown in Table 3.

[0053] Table 3. Performance of the preflush fluids prepared in Examples 1-5 and Comparative Examples 1-3

[0054]

[0055] It can be seen from the results in Table 3 that by adopting the technical solution of the present invention, the preflush fluid prepared by the method of compounding anionic and nonionic surfactants and adding an aminoalkyl coupling agent has a higher (greater than 90%) flushing efficiency, a smaller surface contact angle (<10°) on the N80 steel sheet, and a lower demulsification voltage (less than or equal to 200 V), and can quickly destroy the water-in-oil (W / O) form and stability of the oil-based drilling fluid.

[0056] Next, the interfacial bond strength after flushing with the preflush fluids prepared in Examples 1-2 and Comparative Examples 1-2 was tested. The test process and results are as follows:

[0057] The mold of the simulated casing was taken out after being soaked in drilling fluid at room temperature for 4 hours, and then rinsed in the preflush fluid for cementing prepared in Examples 1-2 and Comparative Examples 1-2 at a rotation speed of 600 r / min for 10 min. Then, cement slurry was injected into the mold. After curing in a water bath at 80 °C for 72 h, a cement stone was obtained. Then, the interfacial bonding strength test of simulated cementing was carried out on a strength press. The specifications of the cement stone were cylinders with a diameter of 25 mm and a height of 50 mm. The test results are shown in Table 4, and the results are the average values of three groups of parallel specimens.

[0058] Among them, the formula of the cement slurry was: G-class cement + 3% microsilica + 0.5% dispersant SXY + 1.2% fluid loss reducer SD18 (Sichuan Chuanqing Downhole Technology Co., Ltd.) + 2.2% expansive agent SDP-1 (Sichuan Chuanqing Downhole Technology Co., Ltd.), water-cement ratio (W / C) = 0.45, and the density was 1.88 g / cm 3 .

[0059] Table 4. Test results of bonding strength

[0060]

[0061] It can be seen from the results in Table 4 that higher interfacial bonding strength can be obtained after rinsing with the preflush fluid for cementing prepared by using the technical solution of the present invention. The system obtained by compounding an anionic surfactant and a nonionic surfactant is more suitable for alkaline liquids such as drilling fluid and cement slurry, can reduce the surface tension of the interface, and thus improve the interfacial bonding strength. At the same time, adding a small amount of aminoalkyl silane coupling agent to the preflush fluid can also improve the bonding quality between the cement stone and the casing and the wellbore.

Claims

1. A pre-flush fluid for cementing in oil-based drilling fluids, wherein, The raw material composition of the preflush fluid for cementing includes: water, an anionic surfactant accounting for 0.1%-10% of the total mass of water, a nonionic surfactant accounting for 0.1%-15% of the total mass of water, a coupling agent accounting for 0.1%-2.5% of the total mass of water, a buffer and / or chelating agent accounting for 0.2%-3% of the total mass of water, a suspending agent accounting for 0.1%-3.0% of the total mass of water, and an antifoaming agent accounting for 0.1%-3.0% of the total mass of water; Among them, the coupling agent is an aminoalkyl silane coupling agent.

2. The preflush fluid for cementing according to claim 1, wherein, The anionic surfactant includes one or a combination of two or more of carboxylate type, sulfonate type, sulfate type, sulfate ester type, phosphate type, and phosphate ester type; Preferably, the anionic surfactant includes one or a combination of two or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, oleate, and triethanolamine oleate; Preferably, the addition amount of the anionic surfactant is 0.1%-3.5% of the total mass of water.

3. The preflush fluid for well cementing according to claim 1, wherein, The nonionic surfactant includes one or a combination of two or more of polyoxyethylene group, fatty alcohol polyoxyethylene ether, and alkylphenol polyoxyethylene ether; Preferably, the polyoxyethylene group includes polyoxyethylene sorbitan monooleate; Preferably, the addition amount of the nonionic surfactant is 0.2%-5.0% of the total mass of water.

4. The pre-flushing fluid for well cementing according to claim 1, wherein, The aminoalkyl silane coupling agent includes one or a combination of two or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and N-aminoethyl-γ-aminopropyltriethoxysilane; Preferably, the addition amount of the aminoalkyl silane coupling agent is 0.2%-0.8% of the total mass of water.

5. The pre-flushing fluid for well cementing according to any one of claims 1 to 3, wherein, The HLB value of the anionic surfactant and the nonionic surfactant is 8-20, preferably 13-18.

6. The preflush fluid for cementing according to claim 1, wherein, The density of the pre-flush fluid for well cementing is 1.00 - 2.30 g / cm 3 , and the density is adjusted by adding weighting agents.

7. The pre-flushing fluid for well cementing according to claim 1, wherein, The buffer includes one or a combination of two or more of carbonate, bicarbonate, phosphate, dihydrogen phosphate, ammonium salt, acetate, sodium tripolyphosphate, sodium hexametaphosphate, and sodium pyrophosphate; The chelating agent is ethylenediaminetetraacetic acid.

8. The preflush fluid for well cementing according to claim 1, wherein, The suspending agent includes one or a combination of two or more of xanthan gum, acrylamide polymer, and sodium carboxymethyl cellulose.

9. The preflush fluid for cementing according to claim 1, wherein, The antifoaming agent is tributyl phosphate and / or silicone; preferably, the silicone is dimethyl silicone oil.

10. The pre-flushing fluid for cementing according to claim 1, wherein, The raw material composition of the preflush fluid for cementing further includes a dispersant accounting for 0.1%-2.0% of the total mass of water; preferably, the dispersant is a ketone-aldehyde condensate.

11. The pre-flushing fluid for cementing according to claim 1, wherein, The flushing efficiency of the preflush fluid for cementing against oil-based drilling fluid is greater than 90%; Preferably, after flushing the surface of the N80 steel sheet adhered with oil-based drilling fluid by the preflush fluid for cementing, the surface contact angle of the N80 steel sheet is less than 10°; Preferably, after mixing the preflush fluid for cementing and the oil-based drilling fluid evenly at a volume ratio of 1:9, the demulsification voltage of the obtained mixed liquid is less than or equal to 200V.

12. The preparation method of the preflush fluid for cementing according to any one of claims 1-11, wherein, The preparation method includes: S1. Completely dissolve the mixture of the anionic surfactant and the nonionic surfactant in water to obtain a surfactant solution; S2. After fully dissolving the suspending agent in water, first add the surfactant solution, then add a buffer and / or a chelating agent for mixing. After the pH value of the mixed solution is stabilized, add a coupling agent. After stirring evenly, add a weighting agent to an appropriate density of the preflush fluid. Add an antifoaming agent during the weighting process to finally obtain a cementing preflush fluid; Preferably, the preparation method further includes adding a dispersant after adding the coupling agent.

13. Application of the cementing preflush fluid according to any one of claims 1-11 in the field of cementing technology, for oil-based drilling fluids.

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