A cementing flush fluid for oil-based drilling fluids and a method of making the same

Abstract

This invention discloses a cementing flushing fluid for oil-based drilling fluid, the components and proportions of which are as follows by weight: In 100 parts by weight of water, it contains 1.4–2.9 parts of emulsifier, 0.7–2.1 parts of penetrant, 0.7–1.4 parts of mutual solvent, 0.5–1 part of cleaning agent, 0.07–0.14 parts of defoamer, and 1.5–3 parts of bio-polysaccharide suspending agent; wherein the bio-polysaccharide suspending agent includes 55–60 parts by weight of natural minerals, 15–20 parts by weight of modified sizing agent, and 11–13 parts by weight of high molecular weight polymer. This invention also discloses a method for preparing this cementing flushing fluid for oil-based drilling fluid. The cementing flushing fluid for oil-based drilling fluid of this invention can improve the flushing efficiency of residual oil-based drilling fluid on the casing, effectively clean diesel-based drilling fluid and white oil-based drilling fluid adhering to the casing wall, and has good rheological properties and good compatibility with drilling fluid and cement slurry.

Description

Technical Field

[0001] This invention belongs to the field of cementing engineering technology, and particularly relates to a cementing flushing fluid for oil-based drilling fluid and its preparation method. Background Technology

[0002] Tight gas and shale gas, as two important unconventional natural gas resources, have gradually become the main growth drivers of natural gas production, possessing significant reserves and production potential. Domestically, tight gas deposits are characterized by deep burial depths, thin gas layers, strong heterogeneity, low gas saturation, and complex gas-water relationships. This necessitates the use of relatively high-density drilling fluids during drilling, requiring the use of suppressive oil-based drilling fluids. Diesel-based and white oil-based drilling fluids are commonly used.

[0003] Inhibitory oil-based drilling fluids, due to their high solids content and diverse treatment agents, exhibit poor compatibility with cement slurry, making drilling fluid displacement and flushing difficult. Flushing fluid, a pre-cementing fluid, is used before cementing to clean oil and cement deposits from the wellbore. Oil-based drilling fluids can stagnate at the interface, forming oil slurry and films, which severely impacts the interfacial bonding strength of the cement sheath and reduces its sealing quality. During drilling fluid displacement in cementing operations, direct contact between cement slurry and drilling fluid leads to varying degrees of cross-contamination. Cement intrusion in the drilling fluid causes the slurry to thicken, become viscous, and even clump together, making it difficult to displace; in severe cases, this can result in a "sausage-like" blistering accident. Conversely, cement slurry contaminated by drilling fluid exhibits deteriorated rheological properties, prolonged setting time, weakened interfacial bonding strength, and decreased compressive strength of the cement stone, significantly affecting interlayer sealing quality.

[0004] Therefore, before cementing operations, special flushing fluids are required to effectively solve the problems of difficult wellbore flushing and cross-contamination between cement slurry and oil-based mud, thus meeting the requirements of high-quality cementing.

[0005] Based on the above, it is necessary to develop an oil-based flushing fluid that can improve the flushing efficiency of residual oil-based drilling fluid on the casing. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a cementing flushing fluid for oil-based drilling fluid and its preparation method. This cementing flushing fluid can improve the flushing efficiency of residual oil-based drilling fluid on the casing, effectively clean diesel-based drilling fluid and white oil-based drilling fluid adhering to the casing wall, and has the characteristics of good rheological properties and good compatibility with drilling fluid and cement slurry.

[0007] Based on this, the following technical solution is adopted:

[0008] This invention provides a cementing and flushing fluid for oil-based drilling fluid, the components and proportions of which are as follows by weight: in 100 parts by weight of water, it contains 1.4 to 2.9 parts of emulsifier, 0.7 to 2.1 parts of penetrant, 0.7 to 1.4 parts of mutual solvent, 0.5 to 1 part of cleaning agent, 0.07 to 0.14 parts of defoamer, and 1.5 to 3 parts of biological polysaccharide suspending agent;

[0009] The biopolysaccharide suspending agent comprises 55-60 parts by weight of natural minerals, 15-20 parts by weight of modified precipitate, and 11-13 parts by weight of high molecular weight polymer.

[0010] Furthermore, the emulsifier is a mixture of alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether, wherein the mass fraction ratio of alkylphenol polyoxyethylene ether to fatty alcohol polyoxyethylene ether is 1:(0.4-0.8).

[0011] Furthermore, the alkylphenol polyoxyethylene ether is octylphenol polyoxyethylene ether; the fatty alcohol polyoxyethylene ether is lauryl alcohol polyoxyethylene ether.

[0012] Further, the penetrant is a mixture of succinate sulfonate and potassium salt of alcohol ether phosphate, wherein the mass fraction ratio of succinate sulfonate to potassium salt of alcohol ether phosphate is 2:(0.8-1.5).

[0013] Furthermore, the succinate sulfonate is sodium dioctyl succinate sulfonate; and the potassium salt of the alcohol ether phosphate is potassium laureth phosphate.

[0014] Furthermore, the mutual solvent is tea tree oil, the cleaning agent is polyethylene glycol 400 dioleate, and the defoamer is isooctanol.

[0015] Furthermore, the biopolysaccharide suspending agent also includes 8-13 parts by weight of inorganic salt and 10-15 parts of silica with a particle size of 50-80 nm; wherein the inorganic salt is a mixture of sodium tripolyphosphate and water glass.

[0016] Furthermore, the natural mineral is a mixture of organobentonite and sepiolite; the modified sizing agent is prepared by graft polymerization of styrene sulfonate and 2-acrylamide-2-methylpropanesulfonic acid monomers.

[0017] Furthermore, the polymer is a copolymer of butyl acrylate and acrylonitrile, and the molecular weight of the copolymer is 800,000 to 1,200,000.

[0018] The present invention also provides a method for preparing the cementing and flushing fluid for oil-based drilling fluid as described above, characterized by comprising the following steps:

[0019] S1. Heat water and add emulsifier, stir until fully dissolved and set aside; stir penetrant at room temperature until homogeneous, add to the above mixed solution and stir until homogeneous; then add mutual solvent, mutual solvent and defoamer in sequence, stir thoroughly and cool to room temperature before discharging to obtain the rinsing agent aqueous solution;

[0020] S2. Slowly add the biological polysaccharide suspending agent to the water and continue stirring until the biological polysaccharide suspending agent is evenly dispersed in the water. Stop stirring and hydrate to obtain the suspending agent dispersion.

[0021] S3. Pour the flushing agent aqueous solution prepared in step S1 into the suspension dispersion in step S2, and stir to obtain the cementing flushing fluid for oil-based drilling fluid.

[0022] Further, in step S2, the biological polysaccharide suspending agent is slowly added to the water at a speed of 4000 r / min, and the mixture is stirred for 2 to 3 minutes until the biological polysaccharide suspending agent is evenly dispersed in the water. Then, the stirring is stopped and the hydration process is carried out for 5 to 10 minutes.

[0023] The present invention has the following beneficial technical effects:

[0024] The oil-based drilling fluid cementing flushing fluid system of this invention is stable, has good rheological properties and settling properties, and does not separate after two days of standing. It can quickly and efficiently flush oil-based drilling fluid adhering to the casing wall, and has good compatibility with oil-based drilling fluid and cement slurry systems, effectively diluting oil-based drilling fluid and cement slurry. It has good flushing, penetration and scouring effects on the annulus interface, ensuring the quality of cementing operations. The production process is simple and the use is safe and convenient. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples.

[0026] In a first aspect, embodiments of the present invention relate to a cementing and flushing fluid for oil-based drilling fluids, wherein the components and proportions by weight are as follows: in 100 parts by weight of water, it contains 1.4 to 2.9 parts of emulsifier, 0.7 to 2.1 parts of penetrant, 0.7 to 1.4 parts of mutual solvent, 0.5 to 1 part of cleaning agent, 0.07 to 0.14 parts of defoamer, and 1.5 to 3 parts of bio-polysaccharide suspending agent. Preferably, the water is purified water. More preferably, the water can be deionized water or distilled water.

[0027] This embodiment studies the flushing mechanism of cementing flushing fluid for oil-based drilling fluids:

[0028] The emulsifiers, penetrants, and cleaning agents in the rinsing solution are all high-performance surfactants. Their combined use exhibits excellent penetrating emulsification and wetting / reversal effects.

[0029] (1) The oil-based drilling fluid is first diluted by the flushing agent solution, which reduces its viscosity;

[0030] (2) Subsequently, the composite surfactant rapidly penetrates and destroys the water-in-oil state of the oil-based drilling fluid. The hydrophilic chain of the surfactant is adsorbed on the oil phase at the interface, and the hydrophilic group surrounds it, turning the mineral oil and oily additives in the oil-based drilling fluid into an oil-in-water state, and then dissolving them in the water-based system. Due to the addition of the biopolysaccharide suspending agent in the flushing fluid, the flushing agent has a certain viscosity, so that other mineral components dispersed in the oil-based drilling fluid will not settle after being separated from the oil-based phase, but will be suspended in the system and discharged with the flushing fluid.

[0031] (3) The oil film and oil-based drilling fluid on the cemented surface can be quickly removed through dissolution, penetration, emulsification and wetting reversal, and the cemented surface will be changed from oil wetting to water wetting.

[0032] The emulsifier is a mixture of alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether, with a mass fraction ratio of alkylphenol polyoxyethylene ether to fatty alcohol polyoxyethylene ether of 1:(0.4-0.8). In other embodiments, the emulsifier of the present invention may also be other emulsifiers commonly used in the art, and the above-mentioned emulsifiers are also included within the scope of this application.

[0033] Alkylphenol polyoxyethylene ether is octylphenol polyoxyethylene ether; fatty alcohol polyoxyethylene ether is lauryl alcohol polyoxyethylene ether.

[0034] The molecular formula of octylphenol polyoxyethylene ether is C8H4O(CH2CH2O). n H (n = 10~15), the molecular formula of lauryl alcohol polyoxyethylene ether is: C 12 H 25 O(CH2CH2O) n H(n=8~15).

[0035] The penetrant is a mixture of succinate sulfonate and potassium salt of alcohol ether phosphate, wherein the mass fraction ratio of succinate sulfonate to potassium salt of alcohol ether phosphate is 2:(0.8-1.5). In other embodiments, the penetrant of the present invention may also be other penetrants commonly used in the art, and the above-mentioned penetrants are also included within the scope of this application.

[0036] The succinate sulfonate is sodium dioctyl succinate sulfonate; the potassium salt of alcohol ether phosphate is potassium laureth phosphate.

[0037] The molecular formula of sodium dioctyl succinate sulfonate is: C 20 H 36 The molecular formula of potassium lauryl ether phosphate (O7SNa) is: C 12 H 25 O(CH2CH2O)PO3K2.

[0038] The miscible solvent is tea tree oil, whose molecular formula is: C 28 H 60 O4P2S4Zn. In other embodiments, the mutual solvents of the present invention can also be other commonly used mutual solvents in the art, and the aforementioned mutual solvents are also included within the scope of this application.

[0039] The cleaning agent is polyethylene glycol 400 dioleate, and its molecular formula is: C 38 H 70 O4. In another embodiment, the cleaning agent of the present invention may also be other cleaning agents commonly used in the art, and the above-mentioned cleaning agents are also included within the scope of this application.

[0040] The defoamer is isooctanol, with the molecular formula C8H12H2O. 18 O. In other embodiments, the defoamer of the present invention may also be other defoamers commonly used in the art, and such defoamers are also included within the scope of this application.

[0041] The bio-polysaccharide suspending agent is a mixture composed of natural minerals, modified stabilizers, and high molecular weight polymers. The suspending stabilizer comprises 55–60 parts by weight of natural minerals, 15–20 parts by weight of modified stabilizers, 11–13 parts by weight of high molecular weight polymers, 8–13 parts by weight of inorganic salts, and 10–15 parts of silica with a particle size of 50–80 nm. The natural minerals are a mixture of organobentonite and sepiolite; the modified stabilizers are obtained by graft polymerization of sodium p-styrene sulfonate and 2-acrylamide-2-methylpropanesulfonic acid monomers; the high molecular weight polymer is a copolymer of butyl acrylate and acrylonitrile with a molecular weight of 800,000–1,200,000; and the inorganic salt is a mixture of sodium tripolyphosphate and water glass.

[0042] Secondly, embodiments of the present invention provide a method for preparing the cementing flushing fluid for oil-based drilling fluid, comprising the following steps:

[0043] S1. Heat water and add emulsifier, stir until fully dissolved and set aside; stir penetrant at room temperature until homogeneous, add to the above mixed solution and stir until homogeneous; then add mutual solvent, mutual solvent and defoamer in sequence, stir thoroughly and cool to room temperature before discharging to obtain the rinsing agent aqueous solution;

[0044] S2. Slowly add the biological polysaccharide suspending agent to the water and continue stirring until the biological polysaccharide suspending agent is evenly dispersed in the water. Stop stirring and hydrate to obtain the suspending agent dispersion.

[0045] S3. Pour the flushing agent aqueous solution prepared in step S1 into the suspension dispersion in step S2, and stir to obtain the cementing flushing fluid for oil-based drilling fluid.

[0046] Preferably, in step S2, the biological polysaccharide suspending agent is slowly added to the water at a rotation speed of 4000 r / min, and the mixture is stirred continuously for 2 to 3 minutes until the biological polysaccharide suspending agent is evenly dispersed in the water. Then, the stirring is stopped and the hydration process is carried out for 5 to 10 minutes.

[0047] Preferably, the above steps can be specifically as follows:

[0048] S1. Add water to the reaction vessel and heat to 50°C. Add octylphenol polyoxyethylene ether and lauryl alcohol polyoxyethylene ether in sequence and stir at low speed for 1 hour to fully dissolve and set aside. Stir sodium dioctyl succinate sulfonate and potassium lauryl ether phosphate at room temperature until homogeneous, then pour into the reaction vessel and stir at low speed for 1 hour. Then add tea tree oil, polyethylene glycol 400 dioleate and isooctanol in sequence and stir thoroughly for 0.5 hours. Cool to room temperature and discharge to obtain the rinsing agent aqueous solution.

[0049] S2. Add clean water to the reactor, slowly add the suspending agent to the water at a speed of 4000 r / min, and continue stirring for 2 to 3 minutes until the suspending agent is evenly dispersed in the water. Stop stirring and hydrate for 5 to 10 minutes.

[0050] S3. Pour the flushing agent solution prepared in step S1 into the suspension dispersion in step S2, and stir at 1500 r / min for 2 min to obtain the cementing flushing fluid for oil-based drilling fluid.

[0051] Example 1

[0052] Add 100 parts by weight of water to a reaction vessel and heat to 50°C. Then, add 1.56 parts by weight of octylphenol polyoxyethylene ether and 0.94 parts by weight of lauryl alcohol polyoxyethylene ether, stirring at low speed for 1 hour until fully dissolved. Next, add 1.2 parts by weight of sodium dioctyl succinate sulfonate and 0.6 parts by weight of potassium lauryl ether phosphate at room temperature, stirring until homogeneous. Then, pour this mixture into the reaction vessel and stir at low speed for 1 hour. Next, add 1 part by weight of tea tree oil, 0.6 parts by weight of polyethylene glycol 400 dioleate, and 0.1 parts by weight of isooctanol, stirring thoroughly for 0.5 hours. Cool to room temperature and discharge to obtain the rinsing agent aqueous solution. Slowly add 2 parts by weight of suspending agent to water at 4000 rpm, stirring continuously for 2–3 minutes until the suspending agent is evenly dispersed in the water. Stop stirring and hydrate for 5–10 minutes to obtain the suspension. Pour the prepared flushing agent aqueous solution into the suspension and stir at 1500 r / min for 2 min to obtain the oil-based drilling fluid cementing flushing fluid.

[0053] Example 2

[0054] Add 100 parts by weight of water to a reaction vessel and heat to 50°C. Then, add 1.73 parts by weight of octylphenol polyoxyethylene ether and 0.87 parts by weight of lauryl alcohol polyoxyethylene ether, stirring at low speed for 1 hour until fully dissolved. Next, add 1.25 parts by weight of sodium dioctyl succinate sulfonate and 0.75 parts by weight of potassium lauryl ether phosphate at room temperature, stirring until homogeneous. Then, pour this mixture into the reaction vessel and stir at low speed for 1 hour. Next, add 1.2 parts by weight of tea tree oil, 0.7 parts by weight of polyethylene glycol 400 dioleate, and 0.14 parts by weight of isooctanol, stirring thoroughly for 0.5 hours. Cool to room temperature and discharge to obtain the rinsing agent aqueous solution. Slowly add 2.8 parts by weight of suspending agent to water at 4000 rpm, stirring continuously for 2–3 minutes until the suspending agent is evenly dispersed in the aqueous solution. Stop stirring and hydrate for 5–10 minutes to obtain the suspension. Pour the prepared flushing agent aqueous solution into the suspension and stir at 1500 r / min for 2 min to obtain the oil-based drilling fluid cementing flushing fluid.

[0055] Example 3

[0056] Add 100 parts by weight of water to a reaction vessel and heat to 50°C. Then, add 1.1 parts by weight of octylphenol polyoxyethylene ether and 1.2 parts by weight of lauryl alcohol polyoxyethylene ether, stirring at low speed for 1 hour until fully dissolved. Next, add 0.91 parts by weight of sodium dioctyl succinate sulfonate and 0.59 parts by weight of potassium lauryl ether phosphate at room temperature, stirring until homogeneous. Pour this mixture into the reaction vessel and stir at low speed for 1 hour. Then, add 0.7 parts by weight of tea tree oil, 0.5 parts by weight of polyethylene glycol 400 dioleate, and 0.08 parts by weight of isooctanol, stirring thoroughly for 0.5 hours. Cool to room temperature and discharge to obtain the rinsing agent aqueous solution. Slowly add 1.5 parts by weight of suspending agent to the rinsing agent aqueous solution at 4000 rpm, stirring continuously for 2–3 minutes until the suspending agent is evenly dispersed in the aqueous solution. Stop stirring and hydrate for 5–10 minutes to obtain the suspension. Pour the prepared flushing agent aqueous solution into the suspension and stir at 1500 r / min for 2 min to obtain the oil-based drilling fluid cementing flushing fluid.

[0057] Comparative Example 1

[0058] Add 100 parts by weight of water to the reactor and heat to 50°C. Then add 1.1 parts by weight of octylphenol polyoxyethylene ether and 0.2 parts by weight of lauryl alcohol polyoxyethylene ether, and stir at low speed for 1 hour until fully dissolved. Stir 0.91 parts by weight of sodium dioctyl succinate sulfonate and 0.59 parts by weight of potassium lauryl ether phosphate at room temperature until homogeneous, then pour into the reactor and stir at low speed for 1 hour. Then add 0.7 parts by weight of tea tree oil, 0.5 parts by weight of polyethylene glycol 400 dioleate, and 0.08 parts by weight of isooctanol, and stir thoroughly for 0.5 hours. Cool to room temperature and discharge to obtain the rinsing agent aqueous solution.

[0059] Evaluation of beneficial effects:

[0060] The evaluation method used is to test the flushing efficiency, rheological properties, and compatibility of the flushing fluids prepared in Examples 1-3 and Comparative Example 1, thereby judging the performance of the cementing flushing fluid for oil-based drilling fluid of the present invention.

[0061] (1) Flushing efficiency evaluation experiment:

[0062] Experimental methods:

[0063] Remove the rotating outer barrel of the rotational viscometer and weigh its mass W0 (g);

[0064] 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).

[0065] Fill the sample cup of the rotational viscometer with the rinsing solution that has been aged at 60°C for 30 minutes, with the liquid level reaching the graduation line of the sample cup.

[0066] Place the rotating outer barrel into the viscometer sample cup containing the rinsing solution, making the scale line of the sample barrel parallel to the liquid level of the rinsing solution in the viscometer sample cup, and start the rotational viscometer to rotate at 300 r / min for 8 minutes.

[0067] Pour out the rinsing solution after rinsing, and add 60℃ clean water to the mark. Rinse off the residual rinsing solution on the rotating cylinder at a speed of 6r / min. After dripping for 3 minutes, take out the sample rotating cylinder and weigh its mass W2 (g).

[0068] Flushing efficiency calculation formula:

[0069]

[0070]

[0071] In the formula: η—flushing efficiency, %

[0072] W0 — Mass of the rotating outer barrel (g);

[0073] W1 — Mass of the mixed sample and rotating outer barrel before rinsing (g);

[0074] W2 — Mass of the mixed sample after rinsing and the rotating outer barrel (g).

[0075] Table 1. Flushing effect data of flushing fluid at 60℃

[0076]

[0077] As shown in Table 1, the cementing flushing fluids for oil-based drilling fluids in Examples 1-3 all achieved flushing efficiencies of over 97% for both white oil-based and diesel-based drilling fluids, with an efficiency exceeding 99% for diesel-based drilling fluids. Therefore, the cementing flushing fluids for oil-based drilling fluids in Examples 1-3 exhibit strong flushing effects. Comparative Example 1 shows that without the addition of a bio-polysaccharide suspending agent, the system viscosity is relatively low, resulting in a significant reduction in flushing efficiency.

[0078] (2) Rheological test of rinsing fluid:

[0079] The oil-based drilling fluid cementing flushing fluid prepared in Example 1 (hereinafter referred to as flushing fluid in Table 2) was selected for rheological compatibility testing. Its density was 1.02 g / cm³. 3 .

[0080] A white oil-based drilling fluid was selected. The formulation of the white oil-based drilling fluid is as follows: white oil + 2.5 wt% organic clay + 3.0 wt% primary emulsifier + 2.5 wt% co-emulsifier + 2.5 wt% filtration reducer + 1.0 wt% nano-plugging agent + 0.4 wt% flow pattern modifier + 3.0 wt% CaO + barite + 20 wt% CaCl2 aqueous solution, with a density of 1.85 g / cm³. 3 ;

[0081] The selected cement slurry system has the following formula: Grade G cement + 3wt% expansion agent BH-P801S + 0.25wt% drag reducer BZGF-1 + 2wt% water loss reducer BH-F202S + 0.35wt% retarder BH-R102L + water, with a density of 1.90 g / cm³. 3 .

[0082] Table 2. Rheological properties of the slurry

[0083]

[0084] Where PV (mPa.s) is the plastic viscosity and YP (Pa) is the dynamic shear force.

[0085] 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 (the viscometer reading decreased). This indicates that the flushing fluid has good rheological compatibility with drilling fluid and cement slurry.

[0086] (3) Rinse fluid compatibility test:

[0087] The oil-based drilling fluid cementing flushing fluid prepared in Example 1 (hereinafter referred to as flushing fluid in Table 3) was selected for a flushing fluid compatibility test. Its density was 1.02 g / cm³. 3 .

[0088] A diesel-based drilling fluid was selected, with the following formulation: diesel oil + 3.0 wt% primary emulsifier + 2.0 wt% organic clay + 3.0 wt% water-in-oil filtration reducer + 1.5 wt% plugging agent type I + 1.0 wt% plugging agent type II + 20 wt% CaCl2 aqueous solution + 2.0 wt% CaO + 0.2% wetting agent + 2.0 wt% ultrafine calcium carbonate, with a density of 1.70 g / cm³. 3 ;

[0089] White oil-based drilling fluid was selected. The white oil-based drilling fluid formula is as follows: white oil + 2.5 wt% organic clay + 3.0 wt% primary emulsifier + 2.5 wt% secondary emulsifier + 2.5 wt% filtration loss reducer + 1.0 wt% nano plugging agent + 0.4 wt% flow pattern modifier + 3.0 wt% CaO + barite + 20 wt% CaCl2 aqueous solution;

[0090] The selected cement slurry system has the following formula: Grade G cement + 3wt% expansion agent BH-P801S + 0.25wt% drag reducer BZGF-1 + 2wt% water loss reducer BH-F202S + 0.35wt% retarder BH-R102L + water, with a density of 1.90 g / cm³. 3 .

[0091] The compatibility of the oil-based drilling fluid with cementing and flushing fluid, oil-based drilling fluid and cement slurry prepared in different proportions in Example 1 was investigated by thickening experiments at 60°C. The experimental results are shown in Table 3.

[0092] Table 3. Thickening experiments of oil-based drilling fluids, cement slurries, and flushing fluids at different proportions

[0093]

[0094] 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.

[0095] In summary, the evaluation experimental data show that the oil-based drilling fluid of this invention has excellent flushing effect in cementing, good compatibility with diesel-based drilling fluid, white oil-based drilling fluid, and cement slurry, and can effectively improve cementing quality. There is no thickening phenomenon after mixing, and it will not contaminate the cementing fluid, ensuring the requirements of high-quality cementing operations.

[0096] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. Although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0097] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A cementing and flushing fluid for oil-based drilling fluids, characterized in that, The components and proportions by weight are as follows: In 100 parts by weight of water, there are 1.4 to 2.9 parts of emulsifier, 0.7 to 2.1 parts of penetrant, 0.7 to 1.4 parts of miscible solvent, 0.5 to 1 part of cleaning agent, 0.07 to 0.14 parts of defoamer, and 1.5 to 3 parts of biological polysaccharide suspending agent; The bio-polysaccharide suspending agent comprises 55-60 parts by weight of natural minerals, 15-20 parts by weight of modified sizing agent, 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; wherein the inorganic salt is a mixture of sodium tripolyphosphate and water glass; the natural mineral is a mixture of organobentonite and sepiolite; the modified sizing agent is obtained by modifying and grafting the sizing agent with sodium p-styrene sulfonate and 2-acrylamide-2-methylpropanesulfonic acid monomer; and the polymer is a copolymer of butyl acrylate and acrylonitrile with a molecular weight of 800,000-1,200,000. The emulsifier is a mixture of alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether, with a mass fraction ratio of alkylphenol polyoxyethylene ether to fatty alcohol polyoxyethylene ether of 1:(0.4-0.8); the penetrant is a mixture of succinate sulfonate and potassium salt of alcohol ether phosphate, with a mass fraction ratio of succinate sulfonate to potassium salt of alcohol ether phosphate of 2:(0.8-1.5); and the cleaning agent is polyethylene glycol 400 dioleate.

2. The cementing and flushing fluid for oil-based drilling fluid according to claim 1, characterized in that, The alkylphenol polyoxyethylene ether is octylphenol polyoxyethylene ether; the fatty alcohol polyoxyethylene ether is lauryl alcohol polyoxyethylene ether.

3. The cementing and flushing fluid for oil-based drilling fluid according to claim 1, characterized in that, The succinate sulfonate is sodium dioctyl succinate sulfonate; the potassium salt of the alcohol ether phosphate is potassium laureth phosphate.

4. The cementing and flushing fluid for oil-based drilling fluid according to claim 1, characterized in that, The mutual solvent is tea tree oil, and the defoamer is isooctanol.

5. A method for preparing a cementing and flushing fluid for oil-based drilling fluid as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Heat water and add emulsifier, stir until fully dissolved and set aside; stir penetrant at room temperature until homogeneous, add to the above mixed solution and stir until homogeneous; then add mutual solvent, mutual solvent and defoamer in sequence, stir thoroughly and cool to room temperature before discharging to obtain the rinsing agent aqueous solution; S2. Slowly add the biological polysaccharide suspending agent to the water and continue stirring until the biological polysaccharide suspending agent is evenly dispersed in the water. Stop stirring and hydrate to obtain the suspending agent dispersion. S3. Pour the flushing agent aqueous solution prepared in step S1 into the suspension dispersion in step S2, and stir to obtain the cementing flushing fluid for oil-based drilling fluid.

6. The preparation method according to claim 5, characterized in that, In step S2, the biological polysaccharide suspending agent is slowly added to the water at a speed of 4000 r / min, and the mixture is stirred for 2 to 3 minutes until the biological polysaccharide suspending agent is evenly dispersed in the water. Then, the stirring is stopped and the hydration process is carried out for 5 to 10 minutes.

Images