A cementing flushing fluid and preparation method thereof

Abstract

The present invention provides a cementing flushing fluid comprising: 100 parts by weight of water; 1 to 5 parts by weight of a suspending agent; 0.1 to 3 parts by weight of a retarder; 5 to 20 parts by weight of an inhibitor; and 2 to 25 parts by weight of an oil-clearing agent. The oil-clearing agent comprises: a penetrant, an emulsifier, a complexing agent, a dispersant, and water. The penetrant is selected from a sulfosuccinate salt and / or a polyoxyethylene ether compound; the emulsifier is a polyoxyethylene ether nonionic surfactant; the complexing agent comprises sodium ethylenediaminetetraacetic acid; and the dispersant is a phosphate. Compared with the prior art, the cementing flushing fluid provided by the present invention utilizes specific components in specific amounts, each component having different functions, resulting in a cementing flushing fluid having excellent cleaning effectiveness. Furthermore, the cementing flushing fluid is simple to prepare, has a wide applicable temperature range, is heat-resistant up to 240°C, and exhibits excellent flushing effectiveness for oil-based drilling fluids with a low-density solids content of 15%.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemistry, and in particular relates to a cementing flushing fluid and a preparation method thereof. Background Art

[0002] In recent years, with the continuous advancement of oil and gas exploration and development, the geological conditions encountered have become increasingly complex. Simultaneously, the exploration and development of shale oil and gas resources has placed increasingly stringent requirements on drilling fluids. Oil-based drilling fluids have been widely used as an effective method for resolving complex and challenging drilling problems and ensuring smooth drilling in shale oil and gas formations. However, oil-based drilling fluids and their filter cakes can adhere to the wellbore wall and are difficult to remove, resulting in poor cementation between the cement slurry and the wellbore, thus compromising cementing quality. Therefore, effectively removing oil-based drilling fluid adhesion from the wellbore wall is a crucial technical measure to ensure cementing quality.

[0003] In existing technology, the main method for eliminating the adhesion of oil-based drilling fluid to the wellbore wall is to clean the wellbore wall with cementing flushing fluid. Flushing fluids currently used both domestically and internationally are formulated from a variety of materials, but all suffer from complex compositions and poor flushing efficiency. Furthermore, field application formulas are fixed and single, failing to consider the low-density solids content of actual oil-based drilling fluids, which significantly impacts flushing effectiveness. This results in incomplete flushing of the wellbore wall, preventing a good seal between the two interfaces. Therefore, research on cementing flushing fluids for oil-based drilling fluids with high flushing efficiency and a wide range of applications, as well as their application methods, provides technical support for oil drilling and is of great strategic significance. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a cementing flushing fluid with good flushing effect and a wide range of applications and a preparation method thereof.

[0005] The present invention provides a cementing flushing fluid, comprising:

[0006]

[0007] The oil clearing agent comprises a penetrant, an emulsifier, a complexing agent, a dispersant and water; the mass ratio of the penetrant, emulsifier, complexing agent, dispersant and water in the oil clearing agent is (2-15): (8-30): (5-20): (0.5-2): 100;

[0008] The penetrant is selected from sulfosuccinate salts and / or polyoxyethylene ether compounds;

[0009] The emulsifier is a polyoxyethylene ether nonionic surfactant;

[0010] The complexing agent includes ethylenediaminetetraacetic acid sodium salt;

[0011] The dispersant is phosphate.

[0012] Preferably, the suspending agent is a polysaccharide / inorganic clay composite super absorbent resin;

[0013] The retarder is selected from phosphate copolymers and / or inorganic-organic polymers;

[0014] The inhibitor is selected from alkali metal halides and / or alkali metal formates.

[0015] Preferably, the suspending agent is a xanthan gum / sodium bentonite composite super absorbent resin;

[0016] The phosphate copolymer includes monomer units formed by organic phosphonate, monomer units formed by itaconic acid and monomer units formed by 2-acrylamido-2-methylpropanesulfonic acid;

[0017] The inorganic-organic polymer includes an organic polymer and an inorganic non-metallic material coupled to the organic polymer via a silane coupling agent; the organic polymer includes a monomer unit formed by itaconic acid and a monomer unit formed by 2-acrylamido-2-methylpropanesulfonic acid;

[0018] The inhibitor is selected from one or more of sodium chloride, potassium chloride, sodium formate and sodium formate.

[0019] Preferably, it further comprises 0.1 to 1 parts by weight of a defoaming agent and 0 to 2 parts by weight of an oxygen scavenger;

[0020] The defoaming agent is selected from one or more of n-butanol, n-octanol and emulsified silicone oil;

[0021] The deoxidizer is selected from sodium sulfate and / or sodium sulfite.

[0022] Preferably, it further comprises 0 to 252 parts by weight of a weighting agent; the weighting agent is barite; the density of the barite is 4.2 to 4.5 g / cm 3 .

[0023] Preferably, the penetrant is selected from sodium salt of di-secondary octyl sulfosuccinate and / or polyoxyethylene ether;

[0024] The emulsifier is selected from alkylphenol polyoxyethylene ether and / or polyoxyethylene sorbitan monooleate;

[0025] The sodium salt of EDTA is selected from tetrasodium EDTA and / or disodium EDTA;

[0026] The complexing agent further comprises one or more of citric acid, sodium gluconate, sodium ethylenediaminetetramethylenephosphate and diethylenetriaminepenta(methylenephosphonate);

[0027] The dispersant is selected from sodium pyrophosphate and / or sodium metaphosphate.

[0028] Preferably, the cementing flushing fluid is suitable for oil-based drilling fluid with a low-density solid content of 2% to 15%.

[0029] The present invention also provides a method for preparing the above-mentioned cementing flushing fluid, comprising the following steps:

[0030] Mixing water, suspending agent, retarder, inhibitor and oil clearing agent to obtain cementing flushing fluid;

[0031] The oil clearing agent comprises: a penetrant, an emulsifier, a complexing agent, a dispersant and water; the mass ratio of the penetrant, emulsifier, complexing agent, dispersant and water in the oil clearing agent is (2-15): (8-30): (5-20): (0.5-2): 100;

[0032] The penetrant is selected from sulfosuccinate salts and / or polyoxyethylene ether compounds;

[0033] The emulsifier is a polyoxyethylene ether nonionic surfactant;

[0034] The complexing agent includes ethylenediaminetetraacetic acid sodium salt;

[0035] The dispersant is phosphate.

[0036] Preferably, the oil clearing agent is prepared according to the following method: the penetrant is mixed with water and stirred for the first time, then the emulsifier is added and stirred for the second time, the complexing agent is added and stirred for the third time, and the dispersant is added and stirred for the fourth time. After heating and reaction, the oil clearing agent for oil-based drilling fluid is obtained.

[0037] Preferably, the rotation speeds of the first stirring, the second stirring, the third stirring and the fourth stirring are each independently 300 to 1000 r / min; the time of the first stirring, the second stirring, the third stirring and the fourth stirring are each independently 5 to 20 min;

[0038] The temperature of the heating reaction is 30° C. to 50° C.; the time of the heating reaction is 0.5 to 2 hours.

[0039] The present invention provides a cementing flushing fluid, comprising: 100 parts by weight of water; 1 to 5 parts by weight of a suspending agent; 0.1 to 3 parts by weight of a retarder; 5 to 20 parts by weight of an inhibitor; and 2 to 25 parts by weight of an oil clearing agent. The oil clearing agent comprises: a penetrant, an emulsifier, a complexing agent, a dispersant, and water. The mass ratio of the penetrant, emulsifier, complexing agent, dispersant, and water in the oil clearing agent is (2 to 15): (8 to 30): (5 to 20): (0.5 to 2): 100. The penetrant is selected from sulfosuccinate salts and / or polyoxyethylene ether compounds. The emulsifier is a polyoxyethylene ether nonionic surfactant. The complexing agent comprises sodium salt of ethylenediaminetetraacetic acid. The dispersant is a phosphate. Compared with the prior art, the cementing flushing fluid provided by the present invention adopts components with specific contents, and each component has different functions, so that the obtained cementing flushing fluid has a good cleaning effect; in addition, the cementing flushing fluid has a simple preparation method, a wide applicable temperature range, and a temperature resistance of up to 240°C. It has a good flushing effect on actual drilling oil-based drilling fluid with a low-density solid phase content of 15%.

[0040] Experiments show that the cementing flushing fluid provided by the present invention has a good flushing effect and is suitable for wells with a density of 0.94 to 2.2 g / cm 3 It is suitable for oil-based drilling fluids and formations with temperatures ranging from 15 to 240°C, and has good environmental performance. DETAILED DESCRIPTION

[0041] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0042] The present invention provides a cementing flushing fluid, comprising: 100 parts by weight of water; 1 to 5 parts by weight of a suspending agent; 0.1 to 3 parts by weight of a retarder; 5 to 20 parts by weight of an inhibitor; and 2 to 25 parts by weight of an oil clearing agent. The oil clearing agent comprises: a penetrant, an emulsifier, a complexing agent, a dispersant, and water. The mass ratio of the penetrant, emulsifier, complexing agent, dispersant, and water in the oil clearing agent is (2 to 15): (8 to 30): (5 to 20): (0.5 to 2): 100. The penetrant is selected from sulfosuccinate salts and / or polyoxyethylene ether compounds. The emulsifier is a polyoxyethylene ether nonionic surfactant. The complexing agent comprises sodium salt of ethylenediaminetetraacetic acid. The dispersant is a phosphate.

[0043] The content of the suspending agent in the cementing flushing fluid provided by the present invention is preferably 1 to 4 parts by weight; in the embodiments provided by the present invention, the content of the suspending agent in the cementing flushing fluid is specifically 4 parts by weight, 2 parts by weight, 3 parts by weight, 1 part by weight or 2 parts by weight; the suspending agent is preferably a polysaccharide / inorganic clay composite superabsorbent resin, more preferably a xanthan gum / sodium bentonite composite superabsorbent resin; the addition of the suspending agent to the cementing flushing fluid has the effect of suspending barite and increasing the density of the flushing fluid.

[0044] The content of the retarder in the cementing flushing fluid provided by the present invention is preferably 0.5 to 3 parts by weight, more preferably 0.5 to 2.5 parts by weight; in the embodiments provided by the present invention, the content of the retarder in the cementing flushing fluid is specifically 0.5 parts by weight, 1 part by weight, 2 parts by weight, 1.5 parts by weight or 2.5 parts by weight; the retarder is preferably a phosphate copolymer and / or an inorganic-organic polymer, which has a wide applicable temperature range and has the effect of prolonging the setting time of the mixed slurry when the cementing flushing fluid contacts the cementing cement slurry; the phosphate copolymer preferably includes monomer units formed by organic phosphonates, monomer units formed by itaconic acid and monomer units formed by 2-acrylamido-2-methylpropanesulfonic acid; the organic phosphonates are organic phosphonates well known to those skilled in the art and are not particularly limited. In the present invention, ethylenediaminetetramethylene phosphate is preferred; in the present invention, preferably, the phosphate copolymer also includes monomer units formed by acrylic acid; the phosphate copolymer is preferably prepared according to the following method: in the presence of an organic phosphonate and an initiator Under the following conditions, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid are polymerized in water, preferably itaconic acid, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid are polymerized in water to obtain a phosphate copolymer; the mass ratio of itaconic acid to 2-acrylamido-2-methylpropanesulfonic acid is preferably (2-8): (3-10); the mass ratio of itaconic acid to acrylic acid is preferably (2-8): (1-5); the initiator is preferably ammonium persulfate and / or potassium persulfate; the temperature of the polymerization reaction is preferably 55° C. to 65° C.; the time of the polymerization reaction is preferably 6 to 8 hours; in the present invention, most preferably, the phosphate copolymer is preferably disclosed in Chinese Patent Publication No. CN109503760A The medium and high temperature oil well cement retarder; the inorganic-organic polymer includes an organic polymer and an inorganic non-metallic material coupled to the organic polymer via a silane coupling agent; the organic polymer includes a monomer unit formed by itaconic acid and a monomer unit formed by 2-acrylamido-2-methylpropanesulfonic acid, and preferably also includes a monomer unit formed by acrylic acid; the inorganic non-metallic material is preferably one or more of silicon carbide, silicon nitride, silicon dioxide and aluminum oxide; the particle size of the inorganic non-metallic material is preferably 1 to 30 microns; the silane coupling agent is a silane coupling agent well known to those skilled in the art, and there is no special limitation. In the present invention, aminopropyltriethoxysilane, 3-methacryloxypropyltrimethylsilane, vinyltrimethoxysilane and One or more of vinyltriethoxysilane; the organic-inorganic polymer is preferably prepared according to the following method: mixing the monomer aqueous solution with an inorganic non-metallic material and a silane coupling agent, and reacting in the presence of an initiator to obtain an organic-inorganic polymer; the monomer aqueous solution comprises itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid and water, and preferably also comprises acrylic acid; the mass ratio of itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid is preferably (2-10): (14-25): (0-2); the mass ratio of itaconic acid to inorganic non-metallic material is preferably (2-10): (0.2-5); the mass ratio of itaconic acid to silane coupling agent is preferably (2-10): (0.02-0.5); the pH value of the monomer aqueous solution is preferably 4-6; the initiator is preferably ammonium persulfate and / or potassium persulfate; the reaction temperature is preferably 60°C-65°C; the reaction time is preferably 6-8 hours; in the present invention, most preferably, the inorganic-organic polymer is the inorganic-organic polymer oil well cement retarder disclosed in publication number CN109503781A.

[0045] The content of the inhibitor in the cementing flushing fluid provided by the present invention is preferably 7 to 20 parts by weight, more preferably 7 to 15 parts by weight; in the embodiments provided by the present invention, the content of the inhibitor in the cementing flushing fluid is specifically 15 parts by weight, 7 parts by weight or 10 parts by weight; the inhibitor is preferably an alkali metal halide and / or an alkali metal formates, more preferably one or more of sodium chloride, potassium chloride, sodium formate and sodium formate; the inhibitor has the effect of inhibiting the dispersion and hydration of shale and improving the stability of the wellbore.

[0046] The content of the oil clearing agent in the cementing flushing fluid provided by the present invention is preferably 5 to 25 parts by weight, more preferably 5 to 20 parts by weight; in the embodiments provided by the present invention, the content of the oil clearing agent in the cementing flushing fluid is specifically 5 parts by weight, 10 parts by weight, 15 parts by weight or 20 parts by weight; the oil clearing agent includes a penetrant, an emulsifier, a complexing agent, a dispersant and water; the mass ratio of the penetrant, emulsifier, complexing agent, dispersant and water in the oil clearing agent is (2 to 15): (8 to 30): (5 to 20): (0.5 to 2): 100, preferably (5 to 15): (8 to 25): (8 to 20): (1 to 2): 100, more preferably (5 to 15): (8 to 25): (8 to 20): (1 to 2): 100, Preferably, it is (5-12):(10-20):(8-18):(1-2):100, and more preferably (5-10):(10-20):(8-15):(1-2):100; in the embodiments provided by the present invention, the mass ratio of the penetrant, emulsifier, complexing agent, dispersant and water in the oil clearing agent is specifically 10:12:15:1:100, 7:14:12:1.5:100, 5:15:15:1:100, 6:20:10:1.5:100, 10:10:12:2:100, 9:20:8:1:100 or 8:16:15:2:100. The penetrant is a sulfosuccinate salt and / or a polyoxyethylene ether compound, which is a nonionic or anionic surfactant with rapid penetration, facilitating the destruction of the oil film and filter cake on the wellbore wall. In the present invention, the sulfosuccinate salt is preferably sodium di-sec-octyl succinate; the polyoxyethylene ether compound is preferably polyoxyethylene ether. The emulsifier is a polyoxyethylene ether nonionic surfactant, which creates an oil-in-water structure and emulsifies the oil film and filter cake destroyed by the penetrant. In the present invention, the polyoxyethylene ether nonionic surfactant is preferably alkylphenol polyoxyethylene ether and / or polyoxyethylene sorbitan monooleate. The complexing agent includes sodium salt of ethylenediaminetetraacetic acid; the sodium salt of ethylenediaminetetraacetic acid is preferably tetrasodium ethylenediaminetetraacetic acid and / or disodium ethylenediaminetetraacetic acid; the complexing agent preferably also includes one or more of citric acid, sodium gluconate, sodium ethylenediaminetetra (methylene phosphate) and diethylenetriamine penta (methylene phosphonate); the mass of the sodium salt of ethylenediaminetetraacetic acid is preferably 20% to 100% of the mass of the complexing agent, more preferably 25% to 100%; in the embodiments provided by the present invention, the mass of the sodium salt of ethylenediaminetetraacetic acid is specifically 100%, 41%, 60%, 50% or 25% of the mass of the complexing agent. In the present invention, the complexing agent can combine with metal ions in the oil-based drilling fluid, promote the separation of the emulsified oil film and filter cake from the well wall, and prevent them from re-adhering to the well wall, thereby improving the cleaning effect. The dispersant is a phosphate, which can make the emulsified oil film and filter cake uniformly dispersed in the flushing liquid and has the effect of stabilizing the emulsion droplets; the phosphate is preferably sodium pyrophosphate and / or sodium metaphosphate; the sodium metaphosphate is (NaPO3) n; In the present invention, n is preferably 1 or 6.

[0047] According to the present invention, the cementing flushing fluid preferably also includes 0.1 to 1 parts by weight of a defoaming agent, more preferably 0.5 to 1 parts by weight of a defoaming agent. The defoaming agent is any defoaming agent known to those skilled in the art and is not particularly limited. In the present invention, one or more of n-butanol, n-octanol, and emulsified silicone oil are preferred. The defoaming agent reduces foaming during the preparation of the cementing flushing fluid, thereby stabilizing the density of the cementing flushing fluid.

[0048] According to the present invention, the cementing flushing fluid preferably further includes 0 to 2 parts by weight of a deoxidizer, more preferably 0 to 1.5 parts by weight of a deoxidizer; in the embodiments provided by the present invention, the content of the deoxidizer in the cementing flushing fluid is specifically 0 parts by weight, 0.8 parts by weight, 1.5 parts by weight, 1 part by weight or 0.3 parts by weight; the deoxidizer is any deoxidizer well known to those skilled in the art and is not particularly limited. In the present invention, sodium sulfate and / or sodium sulfite are preferred; the deoxidizer has the function of removing oxygen in the cementing flushing fluid under high temperature conditions and improving the temperature resistance of the cementing flushing fluid.

[0049] According to the present invention, the cementing flushing fluid preferably further includes 0 to 252 parts by weight of a weighting agent, more preferably further includes 20 to 252 parts by weight of a weighting agent, and more preferably further includes 28 to 252 parts by weight of a weighting agent; in the embodiments provided by the present invention, the content of the weighting agent in the cementing flushing fluid is specifically 28 parts by weight, 60 parts by weight, 117 parts by weight, 191.25 parts by weight, 252 parts by weight or 117.5 parts by weight; the weighting agent is a weighting agent well known to those skilled in the art, and there is no special limitation. In the present invention, it is preferably barite; the density of the barite is preferably 4.2 to 4.5 g / cm 3 , more preferably 4.2 to 4.3 g / cm 3 .

[0050] The density of the cementing flushing fluid provided by the present invention is preferably 1.2 to 2.2 g / cm 3 In the embodiment provided by the present invention, the density of the cementing flushing fluid is specifically 1.2g / cm 3 , 1.4g / cm 3 , 2.0g / cm 3 , 2.2g / cm 3 or 1.7 g / cm 3 .

[0051] The cementing flushing fluid provided by the present invention is preferably suitable for oil-based drilling fluid with a low-density solid phase content of 2% to 15%.

[0052] The cementing flushing fluid provided by the present invention is preferably suitable for a density of 0.94 to 2.2 g / cm3 oil-based drilling fluid.

[0053] The cementing flushing fluid provided by the present invention is preferably suitable for formations with a temperature of 15°C to 240°C.

[0054] The cementing flushing fluid provided by the present invention can select the type of retarder according to the actual drilling bottom temperature on site; and can also determine the amount of oil clearing agent added according to the low-density solid phase content of the oil-based drilling fluid.

[0055] The cementing flushing fluid provided by the present invention adopts components in specific contents, and each component has different functions, so that the obtained cementing flushing fluid has good cleaning effect and compatibility with oil-based drilling fluid and cement slurry. It is suitable for removing oil film and oily filter cake on the well wall after drilling with oil-based drilling fluid, provides good well wall conditions for cementing construction, and significantly improves the two-interface bonding strength during cementing. In addition, the cementing flushing fluid has a simple preparation method, a wide applicable temperature range, and a temperature resistance of up to 240°C. It has a good flushing effect on actual drilling oil-based drilling fluid with a low-density solid phase content of 15%.

[0056] The present invention also provides a method for preparing the above-mentioned cementing flushing fluid, comprising the following steps: mixing water, a suspending agent, a retarder, an inhibitor and an oil clearing agent to obtain a cementing flushing fluid; the oil clearing agent comprises: a penetrant, an emulsifier, a complexing agent, a dispersant and water; the mass ratio of the penetrant, emulsifier, complexing agent, dispersant and water in the oil clearing agent is (2-15): (8-30): (5-20): (0.5-2): 100; the penetrant is selected from sulfosuccinate salts and / or polyoxyethylene ether compounds; the emulsifier is a polyoxyethylene ether nonionic surfactant; the complexing agent comprises sodium salt of ethylenediaminetetraacetic acid; and the dispersant is a phosphate.

[0057] The present invention has no particular limitation on the sources of all raw materials, and any raw materials available on the market can be used. The suspending agent, retarder, inhibitor, oil clearing agent, penetrant, emulsifier, complexing agent and dispersant are all as described above and will not be described in detail here.

[0058] In the present invention, the oil clearing agent is preferably prepared according to the following method: a penetrant, an emulsifier, a complexing agent, a dispersant and water are mixed, and the mixture is heated for reaction to obtain an oil clearing agent for oil-based drilling fluid.

[0059] The penetrant, emulsifier, complexing agent, dispersant and water are mixed; the mixing method is a method well known to those skilled in the art and is not particularly limited. In the present invention, it is preferably as follows: the penetrant and water are mixed for the first stirring, and then the emulsifier is added for the second stirring, the complexing agent is added for the third stirring, and the dispersant is added for the fourth stirring; the rotation speeds of the first stirring, the second stirring, the third stirring and the fourth stirring are each independently preferably 300-1000 r / min, more preferably 400-800 r / min, more preferably 500-700 r / min, and most preferably 600 r / min; the time of the first stirring, the second stirring, the third stirring and the fourth stirring are each independently preferably 5-20 min, more preferably 8-15 min, more preferably 8-12 min, and most preferably 10 min.

[0060] Then, a heating reaction is carried out to obtain an oil clearing agent; the temperature of the heating reaction is preferably 30°C to 50°C; the time of the heating reaction is preferably 0.5 to 2 hours, more preferably 0.8 to 1.5 hours, and even more preferably 1 to 1.2 hours; the heating reaction is preferably carried out under stirring conditions; the stirring speed is preferably 300 to 1000 r / min, more preferably 400 to 800 r / min, even more preferably 500 to 700 r / min, and most preferably 500 to 600 r / min.

[0061] Mix water, suspending agent, retarder, inhibitor and oil clearing agent; in the present invention, preferably, water and suspending agent are first mixed for the first time, and then retarder, inhibitor and oil clearing agent are added for the second mixing; the first mixing and the second mixing are preferably carried out under stirring; the stirring speed is preferably 5000-10000 r / min, more preferably 6000-9000 r / min, and more preferably 8000 r / min; the time of the first mixing and the second mixing is each independently preferably 5-20 min, more preferably 8-15 min, more preferably 8-12 min, and most preferably 10 min.

[0062] In order to further illustrate the present invention, the following describes in detail a cementing flushing fluid and a preparation method thereof in conjunction with examples.

[0063] The reagents used in the following examples are all commercially available. The suspending agent used in the examples is M71S from Puyang Minghua Chemical Co., Ltd.; the retarder is provided by Sinopec Zhongyuan Petroleum Engineering Company; the inhibitor sodium chloride complies with the requirements of HG3255 "Industrial Sodium Chloride", potassium chloride complies with the requirements of GB / T 7118 "Industrial Potassium Chloride", potassium formate complies with Q / CDH 16 "Potassium Formate for Drilling Fluids", and sodium formate complies with the requirements of HG / T 5390 "Industrial Sodium Formate"; the defoaming agent n-butanol complies with GB / T 6027 "Industrial n-butanol", and n-octanol complies with GB / T 6818 "Industrial Octanol" requires that the emulsified silicone oil be provided by Shandong Dayi Chemical Co., Ltd.; the penetrant be A1 sodium salt of dioctyl sulfosuccinate or A2 polyoxyethylene ether compound E-1310 provided by Nantong Yixun Chemical Technology Co., Ltd.; the emulsifier be B1 alkylphenol polyoxyethylene ether NP-10 or B2 polyoxyethylene sorbitan monooleate provided by Xingtai Xinlanxing Technology Co., Ltd.; the complexing agent be C1 tetrasodium ethylenediaminetetraacetic acid, C2 disodium ethylenediaminetetraacetic acid, C3 citric acid, C4 sodium gluconate provided by Suzhou Changhong Chemical Co., Ltd., and C5 sodium ethylenediaminetetramethylenephosphate and C6 sodium diethylenetriaminepenta(methylenephosphonate) provided by Zaozhuang Ziyang Environmental Protection Technology Co., Ltd.; the dispersant be D1 sodium pyrophosphate (Changzhou Chuanlin Chemical Co., Ltd.), D2 sodium hexametaphosphate (Suzhou Changhong Chemical Co., Ltd.), and D3 sodium metaphosphate (provided by Hubei Wonder Chemical Co., Ltd.); the density of the barite used in the examples is 4.2 g / cm 3 .

[0064] Example 1

[0065] (1) Add 10 g of Al to 100 g of water and stir at a stirring rate of 600 r / min for 10 min.

[0066] (2) 12 g of B1 was added to the liquid obtained in step (1), and the mixture was stirred at a stirring rate of 600 r / min for 10 min.

[0067] (3) 15 g of C1 was added to the liquid obtained in step (2), and the mixture was stirred at a stirring rate of 600 r / min for 10 min.

[0068] (4) Add 1 g of D1 to the liquid obtained in step (3) and stir at a stirring rate of 600 r / min for 10 min.

[0069] (5) The solution obtained in step (4) was heated to 30° C., the reaction stirring rate was 500 r / min, and the reaction time was 1.0 h to obtain an oil-based drilling fluid clearing agent MOD-1.

[0070] Example 2

[0071] (1) Add 7 g of Al to 100 g of water and stir at a stirring rate of 600 r / min for 10 min.

[0072] (2) 14 g of B2 was added to the liquid obtained in step (1), and the mixture was stirred at a stirring rate of 600 r / min for 10 min.

[0073] (3) Add 5 g of C1 and 7 g of C5 to the liquid obtained in step (2), and stir at a stirring rate of 600 r / min for 10 min.

[0074] (4) 1.5 g of D2 was added to the liquid obtained in step (3), and the mixture was stirred at a stirring rate of 600 r / min for 10 min.

[0075] (5) The obtained solution was heated to 40° C., the reaction stirring rate was 500 r / min, and the reaction time was 1.0 h to obtain the oil-based drilling fluid clearing agent MOD-2.

[0076] Example 3

[0077] (1) Add 5 g of A2 to 100 g of water and stir at a stirring rate of 600 r / min for 10 min.

[0078] (2) 15 g of B2 was added to the liquid obtained in step (1), and the mixture was stirred at a stirring rate of 600 r / min for 10 min.

[0079] (3) Add 9 g of C2 and 6 g of C3 to the liquid obtained in step (2), and stir at a stirring rate of 600 r / min for 10 min.

[0080] (4) 1 g of D3 was added to the liquid obtained in step (3), and the mixture was stirred at a stirring rate of 600 r / min for 10 min.

[0081] (5) The solution obtained in step (4) was heated to 50° C., the reaction stirring rate was 500 r / min, and the reaction time was 1.0 h to obtain an oil-based drilling fluid clearing agent MOD-3.

[0082] Example 4

[0083] (1) Add 6 g of A2 to 100 g of water and stir at a stirring rate of 600 r / min for 10 min.

[0084] (2) Add 20 g of B1 to the liquid obtained in step (1), and stir at a stirring rate of 600 r / min for 10 min.

[0085] (3) Add 5 g of C1 and 5 g of C4 to the liquid obtained in step (2), and stir at a stirring rate of 600 r / min for 10 min.

[0086] (4) 1.5 g of D1 was added to the liquid obtained in step (3), and the mixture was stirred at a stirring rate of 600 r / min for 10 min.

[0087] (5) The solution obtained in step (4) was heated to 45° C., the reaction stirring rate was 500 r / min, and the reaction time was 1.0 h to obtain an oil-based drilling fluid clearing agent MOD-4.

[0088] Example 5

[0089] (1) Add 10 g of Al to 100 g of water and stir at a stirring rate of 600 r / min for 10 min.

[0090] (2) Add 10 g of B1 to the liquid obtained in step (1), and stir at a stirring rate of 600 r / min for 10 min.

[0091] (3) Add 3 g of C1 and 9 g of C6 to the liquid obtained in step (2), and stir at a stirring rate of 600 r / min for 10 min.

[0092] (4) Add 2 g of D2 to the liquid obtained in step (3) and stir at a stirring rate of 600 r / min for 10 min.

[0093] (5) The solution obtained in step (4) was heated to 30° C., the reaction stirring rate was 500 r / min, and the reaction time was 1.0 h to obtain an oil-based drilling fluid clearing agent MOD-5.

[0094] Example 6

[0095] (1) Add 9 g of A2 to 100 g of water and stir at a stirring rate of 600 r / min for 10 min.

[0096] (2) Add 20 g of B2 to the liquid obtained in step (1), and stir at a stirring rate of 600 r / min for 10 min.

[0097] (3) 4 g of C2 and 4 g of C5 were added to the liquid obtained in step (2), and stirred at a stirring rate of 600 r / min for 10 min.

[0098] (4) Add 1 g of D1 to the liquid obtained in step (3) and stir at a stirring rate of 600 r / min for 10 min.

[0099] (5) The solution obtained in step (4) was heated to 35° C., the reaction stirring rate was 500 r / min, and the reaction time was 1.0 h to obtain an oil-based drilling fluid clearing agent MOD-6.

[0100] Example 7

[0101] (1) Add 8 g of A2 to 100 g of water and stir at a stirring rate of 600 r / min for 10 min.

[0102] (2) 16 g of B1 was added to the liquid obtained in step (1), and the mixture was stirred at a stirring rate of 600 r / min for 10 min.

[0103] (3) 15 g of C1 was added to the liquid obtained in step (2), and the mixture was stirred at a stirring rate of 600 r / min for 10 min.

[0104] (4) Add 2 g of D3 to the liquid obtained in step (3) and stir at a stirring rate of 600 r / min for 10 min.

[0105] (5) The solution obtained in step (4) was heated to 40° C., the reaction stirring rate was 500 r / min, and the reaction time was 1.0 h to obtain an oil-based drilling fluid clearing agent MOD-7.

[0106] Example 8

[0107] (1) Add 16 g of suspending agent to 400 g of clean water, and mix and stir at a stirring rate of 8000 r / min for 10 min to obtain a base slurry;

[0108] (2) Add 2 g of phosphate copolymer (prepared in Example 1 of CN109503760A), 60 g of sodium chloride, 4 g of n-butanol, and 20 g of oil clearing agent MOD-3 to the base slurry, and mix and stir at a stirring rate of 8000 r / min for 10 min;

[0109] (3) Take 400 mL of the slurry obtained in step (2) and add 112 g of barite (density 4.2 g / cm 3 ), mixing and stirring at a stirring rate of 8000 r / min for 10 min;

[0110] (4) The density is 1.2 g / cm 3 cementing flushing fluid.

[0111] Example 9

[0112] (1) Add 8 g of suspending agent to 400 g of clean water, and mix and stir at a stirring rate of 8000 r / min for 10 min to obtain a base slurry;

[0113] (2) Add 4 g of phosphate copolymer (prepared in Example 1 of CN109503760A), 28 g of potassium chloride, 2 g of n-octanol, 40 g of oil clearing agent MOD-3, and 3.2 g of sodium sulfite to the base slurry, and stir at a stirring rate of 8000 r / min for 10 min;

[0114] (3) Take 400 mL of the slurry obtained in step (2), add 240 g of barite, and mix and stir at a stirring rate of 8000 r / min for 10 min;

[0115] (4) The density is 1.4 g / cm 3 cementing flushing fluid.

[0116] Example 10

[0117] (1) Add 12 g of suspending agent to 400 g of clean water, and mix and stir at a stirring rate of 8000 r / min for 10 min to obtain a base slurry;

[0118] (2) Add 8 g of inorganic-organic polymer (prepared in Example 5 of CN109503781A), 40 g of sodium chloride, 4 g of emulsified silicone oil, 60 g of oil clearing agent MOD3, and 6 g of sodium sulfate to the base slurry, and mix and stir at a stirring rate of 8000 r / min for 10 min;

[0119] (3) Take 400 mL of the slurry obtained in step (2), add 470 g of barite, and mix and stir at a stirring rate of 8000 r / min for 10 min;

[0120] (4) The density is 1.7 g / cm 3 cementing flushing fluid.

[0121] Example 11

[0122] (1) Add 4 g of suspending agent to 400 g of clean water, mix and stir at a stirring rate of 8000 r / min for 10 min to obtain a base slurry;

[0123] (2) Add 6 g of inorganic-organic polymer (prepared in Example 5 of CN109503781A), 40 g of potassium formate, 4 g of n-octanol, 80 g of oil clearing agent MOD3, and 4 g of sodium sulfate to the base slurry, and mix and stir at a stirring rate of 8000 r / min for 10 min;

[0124] (3) Take 400 mL of the slurry obtained in step (2), add 765 g of barite, and mix and stir at a stirring rate of 8000 r / min for 10 min;

[0125] (4) The density is 2.0 g / cm 3 cementing flushing fluid.

[0126] Example 12

[0127] (1) Add 4 g of suspending agent to 400 g of clean water, mix and stir at a stirring rate of 8000 r / min for 10 min to obtain a base slurry;

[0128] (2) Add 10 g of inorganic-organic polymer (prepared in Example 5 of CN109503781A), 40 g of sodium formate, 4 g of emulsified silicone oil, 60 g of oil clearing agent MOD3, and 6 g of sodium sulfite to the base slurry, and mix and stir at a stirring rate of 8000 r / min for 10 min;

[0129] (3) Take 400 mL of the slurry obtained in step (2), add 1008 g of barite, and mix and stir at a stirring rate of 8000 r / min for 10 min;

[0130] (4) The density is 2.2 g / cm 3 cementing flushing fluid.

[0131] Example 13

[0132] (1) Add 8 g of suspending agent to 400 g of clean water, and mix and stir at a stirring rate of 8000 r / min for 10 min to obtain a base slurry;

[0133] (2) Add 4 g of phosphate copolymer (prepared in Example 1 of CN109503760A), 60 g of sodium formate, 2 g of n-octanol, 60 g of oil clearing agent MOD3, and 1.2 g of sodium sulfite to the base slurry, and stir at a stirring rate of 8000 r / min for 10 min;

[0134] (3) Take 400 mL of the slurry obtained in step (2), add 470 g of barite, and mix and stir at a stirring rate of 8000 r / min for 10 min;

[0135] (4) The density is 1.7 g / cm 3 cementing flushing fluid.

[0136] The performance of the prepared cementing flushing fluid for oil-based drilling fluid was evaluated.

[0137] Evaluation method for flushing efficiency of cementing flushing fluid used in oil-based drilling fluid:

[0138] (1) Cut 80-grit sandpaper according to the circumference and height of the outer cylinder of the six-speed rotary viscometer, fix it on the surface of the outer cylinder, weigh it, and record its mass as m1.

[0139] (2) Immerse the outer cylinder of the six-speed rotary viscometer in step (1) into the oil-based drilling fluid of the actual drilling site so that the liquid level just covers the upper edge of the sandpaper. Soak for 5 minutes, take it out and weigh it, which is recorded as m2.

[0140] (3) Install the outer cylinder with oil-based drilling fluid on the six-speed rotary viscometer, inject the cementing flushing fluid into the six-speed rotary viscosity sample cup to the scale line, move the base frame so that the flushing fluid level coincides with the scale line on the outer cylinder, rotate at a speed of 300 r / min for 8 minutes, remove the outer cylinder, place it in a 105℃ oven for 2 hours, and weigh its mass again, which is recorded as m3.

[0141] (4) Flushing efficiency calculation formula:

[0142] W=(m2- m3)×100 / (m2-m1) (1)

[0143] Where: w—is the flushing efficiency, %;

[0144] m1—total mass of the outer cylinder and sandpaper before soaking in oil-based drilling fluid, in g;

[0145] m2—mass of oil-based drilling fluid after immersion for 5 minutes, in g;

[0146] m3—The mass after flushing with flushing liquid for 8 minutes and drying for 2 hours, in g.

[0147] Flushing Efficiency of the Cementing Flushing Fluids Prepared in Examples 8-13: Experiments were conducted using the flushing efficiency evaluation method described above. The oil-based drilling fluids used to soak the outer cylinder of the six-speed rotary viscometer were field-tested oil-based drilling fluids, numbered 1# to 6#. The drilling fluid properties are shown in Table 1. The drilling fluid properties were measured and calculated in accordance with the requirements of GB / T 16783.1, "Field Testing of Drilling Fluids in the Petroleum and Natural Gas Industry - Part 1: Water-Based Drilling Fluids."

[0148] Table 1 Performance of oil-based drilling fluids in field drilling

[0149]

[0150] To evaluate the flushing performance of oil-based drilling fluids during field drilling, it's necessary to select cementing flushing fluids with varying oil-clearing agent contents based on the low-density solids content. When the low-density solids content of the oil-based drilling fluid exceeds 5%, the amount of oil-clearing agent added to the flushing fluid must exceed 10%. When the low-density solids content exceeds 10%, the amount of oil-clearing agent added to the flushing fluid must exceed 15%. The experimental results for Examples 8-13 are shown in Table 2.

[0151] Table 2 Flushing efficiency of cementing flushing fluid examples

[0152]

[0153]

[0154] As shown in Table 2, the oil clearing agents prepared in Examples 1 to 6 of the present invention can meet the requirements of density up to 2.2 g / cm 3Or the flushing needs of oil-based drilling fluid with low-density solid content of 15%, the flushing efficiency exceeds 90%, with good flushing effect.

[0155] Based on field drilling data, 85% of oil-based drilling fluids tested had a low-density solids content of ≤8.0%. Therefore, oil-based drilling fluid #6 was selected to evaluate the heat resistance of the examples. Experimental Method: The prepared cementing flushing fluid was placed in an aging tank, aged at a set temperature, removed and cooled to room temperature, and then tested according to the flushing efficiency evaluation method described above. The heat resistance of the cementing flushing fluid is related to the amount of deoxidizer added and the type of retarder. When the bottomhole temperature exceeds 150°C, an inorganic-organic polymer retarder is required, and the deoxidizer dosage is 1.5%. The heat resistance test results of Examples 8-13 are shown in Table 3.

[0156] Table 3 Temperature resistance of cementing flushing fluid examples

[0157] Example Deoxidizer, parts by mass Retarder type Aging conditions Flushing efficiency, % 8 0 Phosphate copolymer 15℃ / 2h 95.4 9 0.8 Phosphate copolymer 150℃ / 2h 96.8 10 1.5 Inorganic-organic polymers 220℃ / 2h 93.9 11 1.0 Inorganic-organic polymers 200℃ / 2h 98.5 12 1.5 Inorganic-organic polymers 240℃ / 2h 94.8 13 0.3 Phosphate copolymer 100℃ / 2h 98.8

[0158] As shown in Table 3, the cementing flushing fluids of Examples 8 to 13 of the present invention still have good flushing capabilities after aging for 2 hours at 15°C to 240°C, with flushing efficiencies exceeding 90%. This indicates that the present invention can meet the requirements for use under formation temperatures of 15°C to 240°C.

[0159] Compatibility testing of the flushing fluid with oil-based drilling fluid and cement slurry: Using oil-based drilling fluid from field drilling #2, a cement slurry with a water-cement ratio of 0.44 was prepared. This slurry was mixed with Example 9 cementing flushing fluid in varying proportions and tested for compatibility. The results are shown in Table 4.

[0160] Table 4 Compatibility of Example 9 with oil-based drilling fluid and cement slurry

[0161]

[0162]

[0163] From the results in Table 4, it can be seen that Example 9 of the present invention has good rheological properties after being mixed with oil-based drilling fluid and cement slurry in actual drilling on site; the thickening time of the slurry mixed with the cement slurry is greater than 300 minutes, meeting the safety requirements of on-site construction.

[0164] Comparative Example 1

[0165] The cementing flushing fluid was prepared according to Example 9. The difference from Example 9 is that the oil clearing agent MOD-3 was not used and was replaced by oil clearing agent R. After testing, the density of the cementing flushing fluid prepared in Comparative Example 1 was 1.4 g / cm 3 .

[0166] Oil clearing agent R was prepared as follows:

[0167] (1) Add 6 g of A2 to 100 g of water and stir at a stirring rate of 600 r / min for 10 min.

[0168] (2) Add 20 g of B1 to the liquid obtained in step (1), and stir at a stirring rate of 600 r / min for 10 min.

[0169] (3) 1.5 g of D1 was added to the liquid obtained in step (2), and the mixture was stirred at a stirring rate of 600 r / min for 10 min.

[0170] (4) The solution obtained in step (3) was heated to 45° C., the reaction stirring rate was 500 r / min, and the reaction time was 1.0 h to obtain an oil-based drilling fluid clearing agent R.

[0171] The performance of the cementing flushing fluids prepared in Example 9 and Comparative Example 1 was evaluated: Experiments were conducted according to the flushing efficiency evaluation method described above. The oil-based drilling fluid used to soak the outer cylinder of the six-speed rotary viscometer was 2# field-drilled oil-based drilling fluid. The flushing efficiencies of Example 9 and Comparative Example are shown in Table 5.

[0172] Table 5 Flushing efficiency of Example 9 and Comparative Example

[0173]

[0174]

[0175] From the results in Table 5, it can be seen that the flushing efficiency of the cementing flushing fluid prepared in Example 9 of the present invention is 97.4%, while the flushing efficiency of Comparative Example 1 is 36.9%.

[0176] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A cementing flushing fluid, characterized in that: include: 100 parts by weight of water; 1-5 parts by weight of suspending agent; 0.1-3 parts by weight of retarder; 5-20 parts by weight of inhibitor; 2-25 parts by weight of oil clearing agent; The oil clearing agent comprises a penetrant, an emulsifier, a complexing agent, a dispersant and water; the mass ratio of the penetrant, emulsifier, complexing agent, dispersant and water in the oil clearing agent is (2-15): (8-30): (5-20): (0.5-2): 100; The complexing agent includes ethylenediaminetetraacetic acid sodium salt; The retarder is selected from phosphate copolymers and / or inorganic-organic polymers; The suspending agent is a xanthan gum / sodium bentonite composite super absorbent resin; The phosphate copolymer includes monomer units formed by organic phosphonate, monomer units formed by itaconic acid and monomer units formed by 2-acrylamido-2-methylpropanesulfonic acid; The inorganic-organic polymer comprises an organic polymer and an inorganic non-metallic material coupled to the organic polymer via a silane coupling agent; the organic polymer comprises monomer units formed by itaconic acid and monomer units formed by 2-acrylamido-2-methylpropanesulfonic acid; the inorganic non-metallic material is one or more of silicon carbide, silicon nitride, silicon dioxide and aluminum oxide; The inhibitor is selected from one or more of sodium chloride, potassium chloride, sodium formate and sodium formate; The penetrant is selected from sodium salt of di-secondary octyl sulfosuccinate and / or polyoxyethylene ether; The emulsifier is selected from alkylphenol polyoxyethylene ether and / or polyoxyethylene sorbitan monooleate; The sodium salt of EDTA is selected from tetrasodium EDTA and / or disodium EDTA; The complexing agent further comprises one or more of citric acid, sodium gluconate, sodium ethylenediaminetetramethylenephosphate and diethylenetriaminepenta(methylenephosphonate); The dispersant is selected from sodium pyrophosphate and / or sodium metaphosphate.

2. The cementing flushing fluid according to claim 1, characterized in that It also includes 0.1 to 1 parts by weight of a defoamer and 0 to 2 parts by weight of an oxygen scavenger; The defoaming agent is selected from one or more of n-butanol, n-octanol and emulsified silicone oil; The deoxidizer is selected from sodium sulfate and / or sodium sulfite.

3. The cementing flushing fluid according to claim 1, characterized in that The invention also includes 0 to 252 parts by weight of a weighting agent; the weighting agent is barite; the density of the barite is 4.2 to 4.5 g / cm 3 .

4. The cementing flushing fluid according to claim 1, characterized in that The cementing flushing fluid is suitable for oil-based drilling fluid with a low-density solid phase content of 2% to 15%.

5. A method for preparing the cementing flushing fluid according to claim 1, characterized in that: The following steps are involved: The cementing flushing fluid is obtained by mixing water, suspending agent, retarder, inhibitor and oil clearing agent.

6. The preparation method according to claim 5, characterized in that The oil clearing agent is prepared according to the following method: a penetrant is mixed with water and stirred for the first time, an emulsifier is added and stirred for the second time, a complexing agent is added and stirred for the third time, a dispersant is added and stirred for the fourth time, and after heating and reaction, an oil clearing agent for oil-based drilling fluid is obtained.

7. The preparation method according to claim 6, characterized in that The rotation speeds of the first stirring, the second stirring, the third stirring, and the fourth stirring are each independently 300 to 1000 r / min; the time of the first stirring, the second stirring, the third stirring, and the fourth stirring are each independently 5 to 20 min; The temperature of the heating reaction is 30° C. to 50° C.; the time of the heating reaction is 0.5 to 2 h.

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