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

Abstract

The invention belongs to the technical field of oil exploitation, and particularly relates to well cementation flushing fluid for oil-based drilling fluid as well as a preparation method and application of the well cementation flushing fluid. The well cementation flushing fluid for the oil-based drilling fluid comprises the following raw material components in parts by weight: 18-25 parts of a cosolvent, 15-20 parts of mineral oil, 5-10 parts of a nonionic emulsifier, 10-15 parts of an anionic emulsifier, 2-4 parts of a penetrant, 2-5 parts of inorganic salt, 0.5-1 part of a defoaming agent and the balance of water, the sum of the parts by weight of the raw materials is 100. The well cementation flushing fluid system for the oil-based drilling fluid is good in rheological property, high in stability, capable of rapidly and efficiently flushing a diesel oil-based drilling fluid and a white oil-based drilling fluid, good in flushing effect, good in compatibility with the drilling fluid and a cement paste system, free of a thickening phenomenon after being mixed, free of a pollution phenomenon to a well cementation fluid and capable of being used for well cementation. And the requirement of high-quality well cementation construction is met.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to a cementing and flushing fluid for oil-based drilling fluid, its preparation method, and its application. Background Technology

[0002] As exploration and development continue, drilling for unconventional oil and gas such as shale oil, shale gas, and tight gas is increasing, and encounters with ultra-deep and high-pressure salt-gypsum formations are becoming more frequent. Oil-based drilling fluids, due to their stable properties, are being used more extensively in complex formations such as shale and salt-gypsum layers, as well as in special structures such as extended reach wells, high-temperature deep wells, and ultra-deep wells, compensating for the weaknesses of water-based drilling fluids in terms of inhibition and lubrication.

[0003] Oil-based drilling fluids, as a non-aqueous fluid system, possess low friction coefficients, high lubricity, excellent fluid loss control, and good wellbore stability. However, the poor compatibility between oil-based drilling fluids and cement slurries is an unavoidable problem in the cementing process. The sensitivity of cement slurries to oil-based drilling fluids means this issue cannot be ignored.

[0004] In recent years, research on cementing technology has deepened both domestically and internationally. More and more researchers are focusing on the impact of oil-based drilling fluids on cementing, primarily on how to quickly clean oil-based drilling fluids adhering to the wellbore and casing walls, enabling the transition from an oil-wetting interface to a water-wetting interface, and further improving the bonding quality of the primary and secondary cementing interfaces. Therefore, before cementing operations, special flushing fluids are required to effectively address the difficulties in wellbore flushing and the cross-contamination between the separator fluid, cement slurry, and oil-based mud, meeting the demands of high-quality cementing.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a cementing flushing fluid for oil-based drilling fluids, its preparation method, and its application. This cementing flushing fluid for oil-based drilling fluids can effectively clean diesel-based and white oil-based drilling fluids adhering to the casing wall. It features good rheological properties and good compatibility with drilling fluids and cement slurries.

[0007] To overcome the shortcomings of the prior art, the present invention provides the following technical solution:

[0008] A cementing and flushing fluid for oil-based drilling fluid comprises, by weight, the following raw material components: 18-25 parts of co-solvent, 15-20 parts of mineral oil, 5-10 parts of nonionic emulsifier, 10-15 parts of anionic emulsifier, 2-4 parts of penetrant, 2-5 parts of inorganic salt, 0.5-1 part of defoamer, and the remainder being water; the total weight of the raw materials is 100.

[0009] Furthermore, the co-solvent includes one or more of ethylene glycol butyl ether, diethylene glycol butyl ether, n-butanol, and n-pentanol.

[0010] Furthermore, the co-solvent is a mixture of ethylene glycol butyl ether and n-pentanol; the mass ratio of ethylene glycol butyl ether to n-pentanol is 1:(0.5-1).

[0011] Furthermore, the mineral oil is a mixture of limonene and terpinene; the mass ratio of limonene to terpinene is 1:(0.8-1.5).

[0012] Furthermore, the nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE); the mass ratio of octylphenol polyoxyethylene ether to MAE is 1:(0.3-0.5).

[0013] And / or, the anionic emulsifier is a mixture of AES and sodium dodecyl sulfate; the mass ratio of the anionic emulsifier to sodium dodecyl sulfate is 1:(0.5-1).

[0014] Furthermore, the penetrant is a mixture of JFC-2 and rapid penetrant T; the mass ratio of JFC-2 to rapid penetrant T is 1:(0.5~1).

[0015] Furthermore, the inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate; the mass ratio of potassium chloride to sodium tripolyphosphate is 1:(0.1-0.2).

[0016] And / or, the defoamer is a mixture of tributyl phosphate and organosilane.

[0017] In addition, the present invention also provides a method for preparing the cementing and flushing fluid for oil-based drilling fluid as described above, comprising the following steps:

[0018] S1. Dissolve the nonionic emulsifier in water at 50-55℃ and stir at low speed until it is completely dissolved to form solution A;

[0019] S2. Add anionic emulsifier to solution A, stir evenly, and continue stirring at low speed for a period of time to form solution B;

[0020] S3. Then, the penetrant, co-solvent, and mineral oil are added to solution B in sequence and stirred thoroughly to form solution C.

[0021] S4. Finally, add inorganic salts and defoamer to solution C, stir thoroughly, and cool to room temperature to obtain the cementing and flushing fluid for oil-based drilling fluid.

[0022] Furthermore, in step S1, the low-speed stirring conditions are: stirring rate 150-300 rpm; stirring time 30-40 min;

[0023] And / or, in step S2, the low-speed stirring conditions are: stirring rate 150-300 rpm; stirring time 30-40 min;

[0024] And / or, in step S3, the stirring time is 30 to 40 minutes.

[0025] In addition, the present invention also provides the application of the cementing flushing fluid for oil-based drilling fluid as described above and / or the cementing flushing fluid for oil-based drilling fluid prepared by the above preparation method in cementing engineering.

[0026] Compared with the prior art, the technical solution of the present invention has at least the following technical effects:

[0027] (1) The cementing flushing fluid for oil-based drilling fluid of the present invention can quickly and efficiently flush oil-based drilling fluid adhering to the casing wall, with a flushing efficiency of over 98%; it has good compatibility with oil-based drilling fluid, isolation fluid, and cement slurry system, and there is no thickening phenomenon after mixing, and it will not cause pollution to the cementing fluid. It can effectively dilute oil-based drilling fluid and cement slurry; it has good flushing, emulsification and wetting reversal effects on the annulus interface, ensuring the safety of cementing construction.

[0028] (2) The oil-based drilling fluid cementing flushing fluid system of the present invention is stable, has good rheological properties, and can be stored for a long time without stratification.

[0029] (3) The preparation process of the cementing flushing fluid for oil-based drilling fluid of the present invention is simple and suitable for large-scale production. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0031] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0032] According to a first aspect of the present invention, a cementing and flushing fluid for oil-based drilling fluid is provided, comprising, by weight, the following raw material components: 18-25 parts of cosolvent (e.g., 18, 19, 20, 21, 22, 23, 24, or 25 parts), 15-20 parts of mineral oil (e.g., 15, 16, 17, 18, 19, or 20 parts), and 5-10 parts of nonionic emulsifier (e.g., 5, 6, 7, or 8 parts). The ingredients are: 10-15 parts anionic emulsifier (e.g., 10, 11, 12, 13, 14, 15 parts), 2-4 parts penetrant (e.g., 2, 3, 4 parts), 2-5 parts inorganic salt (e.g., 2, 3, 4, 5 parts), 0.5-1 part defoamer (e.g., 0.5, 0.6, 0.7, 0.8, 0.9, 1 part), with the remainder being water; the total weight of the ingredients is 100.

[0033] The weight portions described in this invention mainly include the disclosed numerical range, any value (including integers and decimals) within the disclosed range, or an interval between any two values, or multiple discontinuous intervals. It also includes values ​​or numerical ranges whose effects are expected to be similar to the endpoints of the numerical range, such as 5-10 parts. This does not only include 5, 6, 7, 8, 9, 10 parts, or any interval between any two parts. Other numerical ranges, not listed individually, are all included in this invention. Therefore, this invention also includes sub-ranges of any directly disclosed numerical range or any specific value within that range.

[0034] The cementing flushing fluid system for oil-based drilling fluid of the present invention is stable, has good rheological properties, and can be stored for a long time without stratification. Under the synergistic effect of each component, it can quickly and efficiently flush the oil-based drilling fluid adhering to the casing wall. It has good compatibility with oil-based drilling fluid, isolation fluid, and cement slurry system, and can effectively dilute oil-based drilling fluid and cement slurry.

[0035] Specifically, the synergistic effects are as follows: The oil phase of a mineral oil microemulsion is a non-polar liquid, primarily serving as the internal phase of the microemulsion. In microemulsions used for flushing oil-based drilling fluids, limonene and terpinene can be selected as the oil phase to avoid contamination from benzene-containing solvents. Cosolvents can enhance the surface activity of surfactants, forming oil-soluble micromicelles together with them, reducing the polarity of the aqueous phase or enhancing the polarity of the oil phase, thus affecting the phase behavior and properties of the emulsion system. Short-chain alcohols are soluble in oil, increasing the polarity of the oil phase. Simultaneously, due to their short carbon chains, they have a certain solubility in water, thus also dissolving in water and reducing the polarity of water. Short-chain alcohols facilitate the extension of surfactant molecules and can form interfacial composite films with surfactants in the emulsion; for example, n-pentanol can be selected as a cosolvent. Furthermore, ethylene glycol butyl ether is also an excellent organic solvent, showing particularly outstanding effects in dissolving oil stains.

[0036] The aqueous phase of a microemulsion is generally a salt solution. KCl is a common inorganic salt shale inhibitor that has a strong ability to inhibit the hydration and swelling of water-sensitive formations such as shale. For example, if KCl is used as the inorganic salt and a small amount of sodium tripolyphosphate is added, the pH value can be adjusted to a slightly alkaline state. In addition, sodium tripolyphosphate has a certain flushing effect and anti-collapse effect.

[0037] Anionic surfactants have strong temperature resistance and cleaning ability, making them commonly used oil stain cleaners, but they have poor salt resistance. Nonionic surfactants also have good oil and stain removal ability and are less affected by other salt ions. They are also highly resistant to hard water, but the rinsing efficiency of nonionic surfactants deteriorates after reaching their cloud point temperature.

[0038] In the aforementioned cementing and flushing fluid for oil-based drilling fluids, as a preferred embodiment, the co-solvent includes one or more of ethylene glycol butyl ether, diethylene glycol butyl ether, n-butanol, and n-pentanol. Preferably, the co-solvent is a mixture of ethylene glycol butyl ether and n-pentanol; the mass ratio of ethylene glycol butyl ether to n-pentanol is 1:(0.5-1). By testing the solubility of several solvents for surfactants, ethylene glycol butyl ether showed the best effect. Simultaneously, by testing the interaction with surfactants, alcohols were prepared as co-surfactants at this ratio. When the number of carbon atoms in the carbon chain decreases, the salt width increases, and the salinity required to form a medium-phase microemulsion increases. The effect is better when the carbon chain of the alcohol is longer. Considering the affinity relationship with water, n-pentanol was selected. Furthermore, at this ratio, it is easier to form a microemulsion solution.

[0039] In the above-mentioned cementing and flushing fluid for oil-based drilling fluids, as a preferred embodiment, the mineral oil is a mixture of limonene and terpinene; the mass ratio of limonene to terpinene is 1:

[0040] (0.8–1.5). By optimizing the mass ratio of limonene to terpinene at this ratio, a microemulsion state is easily formed.

[0041] In the above-mentioned cementing and flushing fluid for oil-based drilling fluids, as a preferred embodiment, the nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE); the mass ratio of octylphenol polyoxyethylene ether to MAE is 1:(0.3-0.5). A mass ratio of octylphenol polyoxyethylene ether to MAE within this range is preferred for better flushing efficiency.

[0042] Optionally, the anionic emulsifier is a mixture of sodium fatty alcohol polyoxyethylene ether sulfate (AES) and sodium dodecyl sulfate; the mass ratio of the anionic emulsifier AES to sodium dodecyl sulfate is 1:(0.5-1). This mass ratio of the anionic emulsifier AES to sodium dodecyl sulfate is preferably within this range for better rinsing efficiency.

[0043] In the above-mentioned cementing and flushing fluid for oil-based drilling fluids, as a preferred embodiment, the penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and rapid penetrant T (sodium dioctyl sulfonate, mass fraction 50%); the mass ratio of JFC-2 to rapid penetrant T is 1:(0.5~1). A mass ratio of JFC-2 to rapid penetrant T preferably falls within this range for better flushing efficiency.

[0044] In the above-mentioned cementing flushing fluid for oil-based drilling fluid, as a preferred embodiment, the inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate; the mass ratio of potassium chloride to sodium tripolyphosphate is 1:(0.1~0.2); KCl is a common inorganic salt shale inhibitor with a strong ability to inhibit the hydration and swelling of water-sensitive formations such as shale. Therefore, KCl is selected as the inorganic salt, and a small amount of sodium tripolyphosphate is added to adjust the pH value to alkaline, and sodium tripolyphosphate has a certain flushing effect.

[0045] Optionally, the defoamer is a mixture of tributyl phosphate and organosilane, wherein the mass ratio of the mixture of tributyl phosphate and organosilane is 1:1.

[0046] According to a second aspect of the present invention, a method for preparing the cementing and flushing fluid for oil-based drilling fluid as described above is provided, comprising the following steps:

[0047] S1. Dissolve the nonionic emulsifier in water at 50-55℃ and stir at low speed until it is completely dissolved to form solution A;

[0048] S2. Add anionic emulsifier to solution A, stir evenly, and continue stirring at low speed for a period of time to form solution B;

[0049] S3. Then, the penetrant, co-solvent, and mineral oil are added to solution B in sequence and stirred thoroughly to form solution C.

[0050] S4. Finally, add inorganic salts and defoamer to solution C, stir thoroughly, and cool to room temperature to obtain the cementing and flushing fluid for oil-based drilling fluid.

[0051] In the above preparation method, as a preferred embodiment, in step S1, the low-speed stirring conditions are: stirring rate 150-300 rpm; stirring time 30-40 min;

[0052] Optionally, in step S2, the low-speed stirring conditions are: stirring rate 150-300 rpm; stirring time 30-40 min.

[0053] Optionally, in step S3, the stirring time is 30 to 40 minutes.

[0054] According to a third aspect of the invention, the application of the oil-based drilling fluid cementing flushing fluid as described above and / or the oil-based drilling fluid cementing flushing fluid prepared by the above preparation method in cementing engineering is provided.

[0055] The present invention will now be described in detail with reference to embodiments thereof. These examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present invention encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0056] In the embodiments of the present invention, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0057] Example 1

[0058] This embodiment provides a cementing and flushing fluid for oil-based drilling fluid, with the following raw material components: 18 parts of co-solvent, 15 parts of mineral oil, 5 parts of nonionic emulsifier, 10 parts of anionic emulsifier, 2 parts of penetrant, 2 parts of inorganic salt, 0.5 parts of defoamer, and the remainder being water;

[0059] The cosolvent is a mixture of ethylene glycol butyl ether and n-pentanol at a mass ratio of 1:0.5; the mineral oil is a mixture of limonene and terpinene at a mass ratio of 1:0.8; the nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) at a mass ratio of 1:0.3; the anionic emulsifier is a mixture of AES and sodium dodecyl sulfate at a mass ratio of 1:0.5; the penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and QuickT (sodium dioctyl sulfosuccinate, 50% by mass) at a mass ratio of 1:0.5; the inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate at a mass ratio of 1:0.1; and the defoamer is tributyl phosphate and organosilane at a mass ratio of 1:1.

[0060] The preparation method of the cementing flushing fluid for oil-based drilling fluid in this embodiment is as follows:

[0061] Add water to the reactor and heat to 50°C. Add octylphenol polyoxyethylene ether and lauryl phosphate (MAE) sequentially, and stir at low speed for 0.5 hours until fully dissolved. Stir AES and sodium dodecyl sulfate evenly at room temperature, then pour into the reactor and stir at low speed for 0.5 hours. Then add the condensate of JFC-2 fatty alcohol and ethylene oxide, fast T, ethylene glycol butyl ether, n-pentanol, limonene, and terpinene sequentially, and stir thoroughly for 0.5 hours. Finally, add potassium chloride, sodium tripolyphosphate, and defoamer sequentially, stir evenly, and cool to room temperature before discharging to obtain the cementing and flushing fluid for oil-based drilling fluid in this embodiment.

[0062] Example 2

[0063] This embodiment provides a cementing and flushing fluid for oil-based drilling fluid, with the following raw material components: 20 parts of co-solvent, 16 parts of mineral oil, 6 parts of nonionic emulsifier, 11 parts of anionic emulsifier, 2.5 parts of penetrant, 2.5 parts of inorganic salt, 0.6 parts of defoamer, and the remainder being water;

[0064] The cosolvent is a mixture of ethylene glycol butyl ether and n-pentanol at a mass ratio of 1:0.5; the mineral oil is a mixture of limonene and terpinene at a mass ratio of 1:1; the nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) at a mass ratio of 1:0.3; the anionic emulsifier is a mixture of AES and sodium dodecyl sulfate at a mass ratio of 1:0.5; the penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and QuickT (sodium dioctyl sulfosuccinate, 50% by mass) at a mass ratio of 1:0.5; the inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate at a mass ratio of 1:0.2; and the defoamer is a mixture of tributyl phosphate and organosilane at a mass ratio of 1:1.

[0065] The preparation method of the cementing flushing fluid for oil-based drilling fluid in this embodiment is the same as that in Embodiment 1.

[0066] Example 3

[0067] This embodiment provides a cementing and flushing fluid for oil-based drilling fluid, with the following raw material components: 22 parts of co-solvent, 17 parts of mineral oil, 7 parts of nonionic emulsifier, 12 parts of anionic emulsifier, 3 parts of penetrant, 3 parts of inorganic salt, 0.6 parts of defoamer, and the remainder being water;

[0068] The cosolvent is a mixture of ethylene glycol butyl ether and n-pentanol at a mass ratio of 1:0.5; the mineral oil is a mixture of limonene and terpinene at a mass ratio of 1:1; the nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) at a mass ratio of 1:0.4; the anionic emulsifier is a mixture of AES and sodium dodecyl sulfate at a mass ratio of 1:0.6; the penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and QuickT (sodium dioctyl sulfosuccinate, 50% by mass) at a mass ratio of 1:0.8; the inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate at a mass ratio of 1:0.2; and the defoamer is a mixture of tributyl phosphate and organosilane at a mass ratio of 1:1.

[0069] The preparation method of the cementing flushing fluid for oil-based drilling fluid in this embodiment is the same as that in Embodiment 1.

[0070] Example 4

[0071] This embodiment provides a cementing and flushing fluid for oil-based drilling fluid, with the following raw material components: 24 parts of co-solvent, 18 parts of mineral oil, 8 parts of nonionic emulsifier, 13 parts of anionic emulsifier, 3 parts of penetrant, 3 parts of inorganic salt, 0.6 parts of defoamer, and the remainder being water;

[0072] The cosolvent is a mixture of ethylene glycol butyl ether and n-pentanol at a mass ratio of 1:0.6; the mineral oil is a mixture of limonene and terpinene at a mass ratio of 1:1.0; the nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) at a mass ratio of 1:0.4; the anionic emulsifier is a mixture of AES and sodium dodecyl sulfate at a mass ratio of 1:0.7; the penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and FastT (sodium dioctyl sulfosuccinate, 50% by mass) at a mass ratio of 1:0.7; the inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate at a mass ratio of 1:0.2; and the defoamer is a mixture of tributyl phosphate and organosilane at a mass ratio of 1:1.

[0073] The preparation method of the cementing flushing fluid for oil-based drilling fluid in this embodiment is the same as that in Embodiment 1.

[0074] Example 5

[0075] This embodiment provides a cementing and flushing fluid for oil-based drilling fluid, with the following raw material components: 25 parts of co-solvent, 19 parts of mineral oil, 9 parts of nonionic emulsifier, 14 parts of anionic emulsifier, 3 parts of penetrant, 4 parts of inorganic salt, 0.8 parts of defoamer, and the remainder being water;

[0076] The cosolvent is a mixture of ethylene glycol butyl ether and n-pentanol at a mass ratio of 1:0.6; the mineral oil is a mixture of limonene and terpinene at a mass ratio of 1:1.2; the nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) at a mass ratio of 1:0.4; the anionic emulsifier is a mixture of AES and sodium dodecyl sulfate at a mass ratio of 1:0.8; the penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and QuickT (sodium dioctyl sulfosuccinate, 50% by mass) at a mass ratio of 1:0.8; the inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate at a mass ratio of 1:0.2; and the defoamer is a mixture of tributyl phosphate and organosilane at a mass ratio of 1:1.

[0077] The preparation method of the cementing flushing fluid for oil-based drilling fluid in this embodiment is the same as that in Embodiment 1.

[0078] Example 6

[0079] This embodiment provides a cementing and flushing fluid for oil-based drilling fluid, with the following raw material components: 25 parts of co-solvent, 20 parts of mineral oil, 10 parts of nonionic emulsifier, 15 parts of anionic emulsifier, 4 parts of penetrant, 5 parts of inorganic salt, 1 part of defoamer, and the remainder being water.

[0080] The cosolvent is a mixture of ethylene glycol butyl ether and n-pentanol at a mass ratio of 1:0.8; the mineral oil is a mixture of limonene and terpinene at a mass ratio of 1:1.3; the nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) at a mass ratio of 1:0.4; the anionic emulsifier is a mixture of AES and sodium dodecyl sulfate at a mass ratio of 1:0.9; the penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and QuickT (sodium dioctyl sulfosuccinate, 50% by mass) at a mass ratio of 1:0.9; the inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate at a mass ratio of 1:0.2; and the defoamer is a mixture of tributyl phosphate and organosilane at a mass ratio of 1:1.

[0081] The preparation method of the cementing flushing fluid for oil-based drilling fluid in this embodiment is the same as that in Embodiment 1.

[0082] Example 7

[0083] This embodiment provides a cementing and flushing fluid for oil-based drilling fluid, with the following raw material components: 25 parts of co-solvent, 20 parts of mineral oil, 10 parts of nonionic emulsifier, 15 parts of anionic emulsifier, 4 parts of penetrant, 5 parts of inorganic salt, 1 part of defoamer, and the remainder being water.

[0084] The cosolvent is a mixture of ethylene glycol butyl ether and n-pentanol at a mass ratio of 1:0.8; the mineral oil is a mixture of limonene and terpinene at a mass ratio of 1:1.5; the nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) at a mass ratio of 1:0.5; the anionic emulsifier is a mixture of AES and sodium dodecyl sulfate at a mass ratio of 1:1; the penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and QuickT (sodium dioctyl sulfosuccinate, 50% by mass) at a mass ratio of 1:1; the inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate at a mass ratio of 1:0.2; and the defoamer is a mixture of tributyl phosphate and organosilane at a mass ratio of 1:1.

[0085] The preparation method of the cementing flushing fluid for oil-based drilling fluid in this embodiment is the same as that in Embodiment 1.

[0086] Comparative Example 1

[0087] This comparative example provides a cementing and flushing fluid for oil-based drilling fluid (without added co-solvents), with the following raw material components: 20 parts mineral oil, 10 parts nonionic emulsifier, 15 parts anionic emulsifier, 4 parts penetrant, 5 parts inorganic salt, 1 part defoamer, and the remainder being water.

[0088] The mineral oil is a mixture of limonene and terpinene in a mass ratio of 1:1.5; the nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) in a mass ratio of 1:0.5; the anionic emulsifier is a mixture of AES and sodium dodecyl sulfate in a mass ratio of 1:1; the penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and FastT (sodium dioctyl sulfosuccinate, 50% by mass) in a mass ratio of 1:1; the inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate in a mass ratio of 1:0.2; and the defoamer is a mixture of tributyl phosphate and organosilane in a mass ratio of 1:1.

[0089] The preparation method of the cementing and flushing fluid for oil-based drilling fluid in this comparative example is as follows:

[0090] Add water to the reactor and heat to 50°C. Add octylphenol polyoxyethylene ether and lauryl phosphate (MAE) sequentially, and stir at low speed for 0.5 hours until fully dissolved. Stir AES and sodium dodecyl sulfate evenly at room temperature, then pour into the reactor and stir at low speed for 0.5 hours. Then add the condensate of JFC-2 fatty alcohol and ethylene oxide, fast T, limonene, and terpinene sequentially, and stir thoroughly for 0.5 hours. Finally, add potassium chloride, sodium tripolyphosphate, and defoamer sequentially, stir evenly, and cool to room temperature before discharging to obtain the oil-based drilling fluid cementing and flushing fluid of this comparative example.

[0091] Comparative Example 2

[0092] This comparative example provides a cementing and flushing fluid for oil-based drilling fluid (without added mineral oil), with the following raw material components: 25 parts of cosolvent, 10 parts of nonionic emulsifier, 15 parts of anionic emulsifier, 4 parts of penetrant, 5 parts of inorganic salt, 1 part of defoamer, and the remainder being water.

[0093] The cosolvent is a mixture of ethylene glycol butyl ether and n-pentanol in a mass ratio of 1:1; the nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) in a mass ratio of 1:0.5; the anionic emulsifier is a mixture of AES and sodium dodecyl sulfate in a mass ratio of 1:1; the penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and FastT (sodium dioctyl sulfonate, mass fraction 50%) in a mass ratio of 1:1; the inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate in a mass ratio of 1:0.2; and the defoamer is a mixture of tributyl phosphate and organosilane in a mass ratio of 1:1.

[0094] The preparation method of the cementing and flushing fluid for oil-based drilling fluid in this comparative example is as follows:

[0095] Add water to the reactor and heat to 50°C. Add octylphenol polyoxyethylene ether and lauryl phosphate (MAE) sequentially, and stir at low speed for 0.5 hours until fully dissolved. Stir AES and sodium dodecyl sulfate evenly at room temperature, then pour into the reactor and stir at low speed for 0.5 hours. Then add the condensate of JFC-2 fatty alcohol and ethylene oxide, fast T, ethylene glycol butyl ether, and n-pentanol sequentially, and stir thoroughly for 0.5 hours. Finally, add potassium chloride, sodium tripolyphosphate, and defoamer sequentially, stir evenly, and cool to room temperature before discharging to obtain the oil-based drilling fluid cementing and flushing fluid of this comparative example.

[0096] Comparative Example 3

[0097] This comparative example provides a cementing and flushing fluid for oil-based drilling fluid. All other raw materials are the same as those in Example 1, except that the nonionic emulsifier is only octylphenol polyoxyethylene ether.

[0098] Comparative Example 4

[0099] This comparative example provides a cementing and flushing fluid for oil-based drilling fluid. All other raw materials are the same as those in Example 1, except that the anionic emulsifier is AES.

[0100] Comparative Example 5

[0101] This comparative example provides a cementing and flushing fluid for oil-based drilling fluid. All other raw materials are the same as those in Example 1, except that the co-solvent is only ethylene glycol butyl ether.

[0102] Comparative Example 6

[0103] This comparative example provides a cementing and flushing fluid for oil-based drilling fluid. All other raw materials are the same as those in Example 1, except that the mineral oil is only terpene oil.

[0104] Performance testing:

[0105] (1) Flushing efficiency evaluation experiment:

[0106] A diesel-based drilling fluid was selected, with the following formulation: diesel oil + 3.0% main co-solvent + 2.0% organic clay + 3.0% water-in-oil filtration reducer + 1.5% plugging agent type I + 1.0% plugging agent type II + 20% CaCl2 aqueous solution + 2.0% CaO + 0.2% wetting agent + 2.0% ultrafine calcium carbonate, with a density of 1.70 g / cm³. 3 White oil-based drilling fluid was selected. The white oil-based drilling fluid formula is as follows: white oil + 2.5% organic clay + 3.0% main co-solvent + 2.5% auxiliary solvent + 2.5% filtration loss reducer + 1.0% nano plugging agent + 0.4% flow pattern modifier + 3.0% CaO + barite + 20% CaCl2 aqueous solution.

[0107] Experimental methods:

[0108] Remove the rotating outer barrel of the rotational viscometer and weigh its mass W0 (g);

[0109] Immerse the lower 2 / 3 of the outer barrel of the rotational viscometer in white oil-based drilling fluid, apply the fluid at 100 r / min for 1 min, then soak for 20 min, let it drip for 3 min, and then remove it and weigh its mass W1 (g).

[0110] A washing solution at a certain temperature is filled into the sample cup of the rotational viscometer, with the liquid level reaching the graduation line of the sample cup;

[0111] Place the rotating outer barrel into the viscometer sample cup containing the rinsing solution, so that the scale line of the sample barrel is parallel to the liquid surface of the rinsing solution in the viscometer sample cup. Start the rotational viscometer and rotate it at 200 r / min for 5 min. After dripping for 3 min, remove the sample barrel and weigh its mass W2 (g).

[0112] Flushing efficiency calculation formula:

[0113]

[0114] In the formula: η—flushing efficiency, %

[0115] W0 — Mass of the rotating outer barrel (g);

[0116] W1 — Mass of the mixed sample and rotating outer barrel before rinsing (g);

[0117] W2 — Mass of the mixed sample after rinsing and the rotating outer barrel (g).

[0118] Table 1: Data on the flushing effect of flushing fluid at 60℃

[0119]

[0120]

[0121]

[0122] Table 1 shows that the cementing flushing fluid achieves a flushing efficiency of up to 90% for white oil-based drilling fluids, demonstrating a strong flushing effect. Comparative Examples 1-2 show that without the addition of mineral oil or co-solvent, a microemulsion cannot be formed in the system, resulting in a significant reduction in flushing efficiency. Comparative Examples 5-6 show that using a single component of mineral oil or co-solvent provides a certain flushing effect, but it is not optimal. Similarly, Comparative Examples 3-4 show that using a single nonionic or anionic emulsifier also leads to a substantial reduction in flushing efficiency.

[0123] (2) Rheological test of rinsing fluid:

[0124] The cementing flushing fluid prepared in Example 5 was selected for rheological compatibility testing, and its density was 1.02 g / cm³. 3 .

[0125] A white oil-based drilling fluid was selected. The formulation of the white oil-based drilling fluid is as follows: white oil + 2.5% organic clay + 3.0% primary co-solvent + 2.5% auxiliary solvent + 2.5% filtration reducer + 1.0% nano-plugging agent + 0.4% flow pattern modifier + 3.0% CaO + 120% barite + 20% CaCl2 aqueous solution, with a density of 1.60 g / cm³. 3 The cement slurry system selected for on-site use has the following formula: Grade G cement + 2.5% water loss reducer BH-F202S + 0.2% retarder BH-R102L + water, with a density of 1.90 g / cm³. 3 .

[0126] Table 2: Rheological properties of the slurry

[0127]

[0128] Table 2 shows that after the flushing fluid was mixed with drilling fluid and cement slurry in different proportions, the slurry became thinner, and no thickening or flocculation occurred. This indicates that the flushing fluid has good rheological compatibility with drilling fluid and cement slurry.

[0129] (3) Rinse fluid compatibility test:

[0130] The cementing flushing fluid prepared in Example 5 was selected for rheological compatibility testing, and its density was 1.02 g / cm³. 3 Diesel-based drilling fluid was selected. The formulation of the diesel-based drilling fluid is as follows: diesel oil + 3.0% main co-solvent + 2.0% organic clay + 3.0% water-in-oil filtration reducer + 1.5% plugging agent type I + 1.0% plugging agent type II + 20% CaCl2 aqueous solution + 2.0% CaO + 0.2% wetting agent + 2.0% ultrafine calcium carbonate, with a density of 1.70 g / cm³. 3 The selected drilling fluid is a white oil-based fluid with the following formulation: white oil + 2.5% organic clay + 3.0% primary co-solvent + 2.5% auxiliary solvent + 2.5% filtration loss reducer + 1.0% nano-plugging agent + 0.4% flow pattern modifier + 3.0% CaO + barite + 20% CaCl2 aqueous solution. The selected cement slurry system is a cement slurry with the following formulation: Grade G cement + 3% expansion agent BH-P801S + 0.25% drag reducer BZGF-1 + 2% fluid loss reducer BH-F202S + 0.35% retarder BH-R102L + water, with a density of 1.90 g / cm³. 3 The compatibility of cementing flushing fluid, oil-based drilling fluid, and cement slurry with different proportions was investigated by thickening experiments at 60°C. The experimental results are shown in Table 3.

[0131] Table 3 Thickening experiments of oil-based drilling fluids, cement slurries, and flushing fluids at different proportions.

[0132]

[0133] As shown in Table 3, the flushing fluid, cement slurry, and oil-based drilling fluid do not exhibit gelation or flocculation after mixing. The initial consistency is ≤30 Bc, the linear abrupt change value of thickening is ≤10, and the thickening time is not shortened, demonstrating good compatibility.

[0134] In summary, the above evaluation experimental data show that the cementing flushing fluid of the present invention has excellent flushing effect, good compatibility with diesel-based drilling fluid, white oil-based drilling fluid and cement slurry, and can effectively improve cementing quality.

[0135] Comparing the above examples and comparative examples, it can be seen that in Examples 1-7, a cementing flushing fluid has the following components and proportions by weight: 18-25 parts of co-solvent, 15-20 parts of mineral oil, 5-10 parts of nonionic emulsifier, 10-15 parts of anionic emulsifier, 2-4 parts of penetrant, 2-5 parts of inorganic salt, 0.5-1 part of defoamer, and the remainder is water. The co-solvent is ethylene glycol butyl ether: n-pentanol in a mass fraction ratio of 1:0.5-1.0. The mineral oil is a mixture of limonene and terpinene in a mass fraction ratio of 1:0.8-1.5. The nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) in a mass fraction ratio of 1:0.3-0.5. The anionic emulsifier is a mixture of sodium fatty alcohol polyoxyethylene ether sulfate and sodium dodecyl sulfate in a mass fraction ratio of 1:0.5-1. The penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and QuickT (sodium dioctyl sulfonate, 50% by mass), with a mass ratio of 1:0.5-1. The inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate, with a mass ratio of 1:0.1-0.2. The defoamer is tributyl phosphate and organosilicon, with a mass ratio of 1:1. For both diesel-based and white oil-based drilling fluids, the flushing efficiency is greater than 90%, and it exhibits good compatibility with cement-based and drilling fluids.

[0136] Furthermore, from Examples 4-7, it can be concluded that a cementing flushing fluid comprises the following components and proportions by weight: 24-25 parts of co-solvent, 18-20 parts of mineral oil, 8-10 parts of nonionic emulsifier, 13-15 parts of anionic emulsifier, 3-4 parts of penetrant, 3-5 parts of inorganic salt, 0.6-1 parts of defoamer, and the remainder being water. The co-solvent is ethylene glycol butyl ether: n-pentanol in a mass fraction ratio of 1:0.6-1.0. The mineral oil is a mixture of limonene and terpinene in a mass fraction ratio of 1:1.0-1.5. The nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) in a mass fraction ratio of 1:0.4-0.5. The anionic emulsifier is a mixture of sodium fatty alcohol polyoxyethylene ether sulfate and sodium dodecyl sulfate in a mass fraction ratio of 1:0.7-1. The penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and Quick T (sodium dioctyl sulfonate, 50% by mass), with a mass ratio of 1:0.7-1. The inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate, with a mass ratio of 1:0.2. The defoamer is tributyl phosphate and organosilicon, with a mass ratio of 1:1. For both diesel-based and white oil-based drilling fluids, the flushing efficiency is greater than 95%, and it exhibits good compatibility with cement-based and drilling fluids.

[0137] Furthermore, from Examples 4-5, it can be seen that a cementing flushing fluid comprises the following components and proportions by weight: 24-25 parts of co-solvent, 18-19 parts of mineral oil, 8-9 parts of nonionic emulsifier, 13-14 parts of anionic emulsifier, 3 parts of penetrant, 3-4 parts of inorganic salt, 0.6-0.8 parts of defoamer, and the remainder being water. The co-solvent is ethylene glycol butyl ether: n-pentanol in a mass fraction ratio of 1:0.6. The mineral oil is a mixture of limonene and terpinene in a mass fraction ratio of 1:1.0-1.2. The nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE) in a mass fraction ratio of 1:0.4. The anionic emulsifier is a mixture of sodium fatty alcohol polyoxyethylene ether sulfate and sodium dodecyl sulfate in a mass fraction ratio of 1:0.7-0.8. The penetrant is a mixture of JFC-2 (a condensate of fatty alcohol and ethylene oxide) and Quick T (sodium dioctyl sulfonate, 50% by mass), with a mass ratio of 1:0.7-0.8. The inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate, with a mass ratio of 1:0.2. The defoamer is tributyl phosphate and organosilicon, with a mass ratio of 1:1. For both diesel-based and white oil-based drilling fluids, the flushing efficiency is greater than 98%, and it exhibits good compatibility with cement-based and drilling fluids.

[0138] The foregoing has described and evaluated some embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, still fall within the protection scope of the present invention.

Claims

1. A cementing and flushing fluid for oil-based drilling fluids, characterized in that, By weight, it includes the following raw material components: 18-25 parts of cosolvent, 15-20 parts of mineral oil, 5-10 parts of nonionic emulsifier, 10-15 parts of anionic emulsifier, 2-4 parts of penetrant, 2-5 parts of inorganic salt, 0.5-1 part of defoamer, and the remainder is water; The total weight of the raw materials is 100.

2. The cementing and flushing fluid for oil-based drilling fluid according to claim 1, characterized in that, The co-solvent includes one or more of ethylene glycol butyl ether, diethylene glycol butyl ether, n-butanol, and n-pentanol.

3. The cementing and flushing fluid for oil-based drilling fluid according to claim 2, characterized in that, The co-solvent is a mixture of ethylene glycol butyl ether and n-pentanol; the mass ratio of ethylene glycol butyl ether to n-pentanol is 1:(0.5-1).

4. The cementing and flushing fluid for oil-based drilling fluid according to any one of claims 1-3, characterized in that, The mineral oil is a mixture of limonene and terpinene; the mass ratio of limonene to terpinene is 1:(0.8-1.5).

5. The cementing and flushing fluid for oil-based drilling fluid according to claim 1, characterized in that, The nonionic emulsifier is a mixture of octylphenol polyoxyethylene ether and lauryl phosphate (MAE); the mass ratio of octylphenol polyoxyethylene ether to MAE is 1:(0.3-0.5). And / or, the anionic emulsifier is a mixture of AES and sodium dodecyl sulfate; the mass ratio of the anionic emulsifier to sodium dodecyl sulfate is 1:(0.5-1).

6. The cementing and flushing fluid for oil-based drilling fluid according to claim 1, characterized in that, The penetrant is a mixture of JFC-2 and rapid penetrant T; the mass ratio of JFC-2 to rapid penetrant T is 1:(0.5~1).

7. The cementing and flushing fluid for oil-based drilling fluid according to claim 5 or 6, characterized in that, The inorganic salt is a mixture of potassium chloride and sodium tripolyphosphate; the mass ratio of potassium chloride to sodium tripolyphosphate is 1:(0.1-0.2). And / or, the defoamer is a mixture of tributyl phosphate and organosilane.

8. A method for preparing a cementing and flushing fluid for oil-based drilling fluid as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Dissolve the nonionic emulsifier in water at 50-55℃ and stir at low speed until it is completely dissolved to form solution A; S2. Add anionic emulsifier to solution A, stir evenly, and continue stirring at low speed for a period of time to form solution B; S3. Then, the penetrant, co-solvent, and mineral oil are added to solution B in sequence and stirred thoroughly to form solution C. S4. Finally, add inorganic salts and defoamer to solution C, stir thoroughly, and cool to room temperature to obtain the cementing and flushing fluid for oil-based drilling fluid.

9. The preparation method according to claim 8, characterized in that, In step S1, the low-speed stirring conditions are: stirring rate 150-300 rpm; stirring time 30-40 min; And / or, in step S2, the low-speed stirring conditions are: stirring rate 150-300 rpm; stirring time 30-40 min; And / or, in step S3, the stirring time is 30 to 40 minutes.

10. The application of the cementing flushing fluid for oil-based drilling fluid as described in any one of claims 1-7 and / or the cementing flushing fluid for oil-based drilling fluid prepared by the preparation method described in claim 8 or 9 in cementing engineering.

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