CN109812249B - Oil reservoir oil displacement method - Google Patents
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Abstract
The invention relates to the field of oil reservoir oil displacement, and discloses an oil reservoir oil displacement method, wherein the oil displacement method comprises the following steps: injecting a front slug A, then injecting gas, sequentially and alternately injecting a viscosity-reducing oil displacement system B and gas, then injecting a protection slug C, and finally injecting water into an oil layer from an injection well; wherein the pre-slug A is an aqueous solution containing a surfactant and/or a polymer, and the viscosity-reducing oil displacement system B contains the surfactant, alcohol, the polymer and water; the protection slug C is an aqueous solution containing a polymer. According to the invention, by a periodically-transformed 'liquid-gas' alternate injection method, the shearing action of the stratum deep emulsifying agent and the thick oil is enhanced, the stratum deep thick oil is promoted to be emulsified, the emulsifying and oil washing action of an oil displacement system in the stratum deep is enhanced, and the oil washing efficiency and the sweep efficiency in the oil displacement process are obviously improved.
Description
Technical Field
The invention relates to an oil reservoir oil displacement method, in particular to an oil reservoir oil displacement method suitable for a heavy oil exploitation process.
Background
The thick oil refers to crude oil with viscosity of more than 50mPa.s at 50 ℃. The thick oil development has a certain proportion in the oil gas development of China, and the thick oil distribution exists in Liaohe oil field, victory oil field, xinjiang oil field, original oil field and Jiangsu oil field. In the existing thick oil development technology, the thermal oil extraction is mainly performed, the viscosity of thick oil is reduced by heating, the fluidity of thick oil is improved, and the recovery ratio is improved. The main disadvantage of thermal oil recovery is the high energy consumption. For oil reservoirs with deep burial, thin oil layer and high water content, the heat utilization rate in the heat recovery process is low. In contrast, in the process of thick oil cold recovery, the method is not limited by the conditions.
In the thick oil exploitation process, the viscosity of the thick oil is far higher than that of water, so that the unfavorable high fluidity ratio is caused, and the water injection exploitation recovery ratio of the thick oil is lower. Viscous fingering due to high fluidity ratio makes the sweep efficiency of the displacement process lower, resulting in low recovery of the heavy oil development. Improving the fluidity of the thick oil, and expanding the sweep efficiency in the displacement process is a key for improving the recovery ratio in the thick oil exploitation process. In the prior art, the fluidity of the thick oil is improved mainly through emulsification viscosity reduction, and the recovery ratio of the thick oil is improved. The viscosity reduction method is to adopt an external surfactant to form an oil-in-water emulsion from the thickened oil and the aqueous solution of the surfactant, thereby reducing the viscosity of crude oil and improving the fluidity of the thickened oil.
CN103320110a discloses a nano composite high temperature resistant mining aid for thick oil and super thick oil exploitation and a preparation method thereof. The method comprises the steps of preparing the modified nano inorganic auxiliary agent, petroleum sulfonate, viscosity reducer, emulsifier, surface wetting agent, penetrating agent, macromolecule modifier, accelerator, catalyst and water. The modified nano inorganic auxiliary agent is modified nano SiO 2 The viscosity reducing agent is an anionic surfactant and/or a nonionic surfactant. The viscosity reducing agent can reduce viscosity of thick oil under high temperature.
CN104650843a discloses an emulsified viscosity-reducing oil displacement composition suitable for heavy oil reservoirs, which comprises the following components in percentage by weight: 0.1-0.3% of anionic polymer, 0.01-0.1% of nonionic surfactant, 0.02-0.12% of emulsion stabilizer, a proper amount of inorganic salt and the balance of water. Wherein the anionic polymer comprises an anionic polymer having carboxyl groups in the molecule, preferably sodium polyacrylate. The nonionic surfactant comprises one or more of alkyl glycoside, tween 80 and tween 85. The emulsion stabilizer comprises polyacrylamide. The emulsified viscosity-reducing oil displacement agent composition has good emulsification viscosity-reducing and oil displacement effects on common thick oil.
CN103422840a discloses an oil displacement method adopting a combination of anionic and cationic compound surfactants, which is applied to thin oil to improve recovery ratio. The oil displacement agent contains anionic surfactant, cationic surfactant, polymer and water. Wherein the anionic surfactant is at least one selected from petroleum sulfonate, alkylbenzenesulfonate, olefin sulfonate, lignin sulfonate, petroleum carboxylate and alkyl carboxylate, the cationic surfactant is tetraalkylammonium chloride and/or tetraalkylammonium hydroxide, and the polymer is polyacrylamide or xanthan gum. The system can form ultra-low interfacial tension with dilute crude oil under the alkali-free condition.
CN102287172 a discloses a method for heavy oil recovery. The method adopts a method of injecting gel profile control slugs and then injecting an oil displacement agent to recover thick oil. The method utilizes the movable gel profile control agent to improve the sweep efficiency of the displacement process, then injects the surfactant oil displacement agent, and adopts the technology of combining '2+3' to improve the recovery ratio.
For some common thickened oil, the viscosity of the thickened oil in the stratum is less than 10000 Pa.s, the thickened oil can flow in the stratum, water injection development can be carried out, but the exploitation effect is poor. As previously mentioned, the primary factor affecting recovery in the thickened oil cold recovery process is sweep efficiency. The method in the prior art mainly improves the recovery ratio by improving the fluidity of the thick oil through emulsification viscosity reduction, and has less influence on the enhancement of the sweep efficiency, so that the improvement effect of the recovery ratio needs to be further improved.
Disclosure of Invention
The invention aims to solve the problem that recovery ratio is to be improved in the prior art, and provides an oil reservoir oil displacement method which can improve an oil reservoir, particularly can simultaneously improve oil washing efficiency and sweep efficiency in the displacement process of common heavy oil and wax-containing heavy oil, and can greatly improve the water-flooding exploitation effect of the oil reservoir.
The inventor of the invention discovers that the emulsification viscosity reduction of the thickened oil is successfully applied to the shaft lifting process, the thickened oil pipe conveying process and the single well throughput process at present, but the emulsification viscosity reduction technology cannot be applied to the industrialized scale in the oil displacement process. The main influencing factor is that the thick oil emulsification process cannot be formed spontaneously and can only occur under a certain shearing force condition; the shearing action in the shaft and pipe transportation process can meet the emulsifying requirement; and for the viscous oil emulsification viscosity-reducing oil displacement technology, unlike the viscous oil shaft viscosity-reducing lifting and viscous oil chemical viscosity-reducing conveying process, the shearing acting force of the emulsifier in the stratum migration process is far lower than that in the shaft and pipe conveying process under stratum conditions, and the shearing acting force is lower and lower along with the emulsifier migration to the stratum deep part, so that the emulsifying effect of the emulsifier in the stratum deep part is weakened and even emulsification cannot occur, and the emulsifying oil displacement effect is obviously reduced. In addition, because the viscosity of the thickened oil is far higher than that of the thin oil, the sweep efficiency in the water drive process is far lower than that of a thin oil reservoir, and the viscosity of the displacement phase is further reduced by the simple emulsification viscosity reduction effect, so that the sweep efficiency is reduced.
In order to achieve the above object, the present invention provides a method for displacing oil in an oil reservoir, wherein the method for displacing oil comprises: injecting a front slug A, then injecting gas, sequentially and alternately injecting a viscosity-reducing oil displacement system B and gas, then injecting a protection slug C, and finally injecting water into an oil layer from an injection well;
Wherein the pre-slug A is an aqueous solution containing a surfactant and/or a polymer, and the viscosity-reducing oil displacement system B contains the surfactant, alcohol, the polymer and water; the protection slug C is an aqueous solution containing a polymer.
According to the invention, by a periodically-transformed 'liquid-gas' alternate injection method, the shearing action of the stratum deep emulsifying agent and the thick oil is enhanced, the stratum deep thick oil is promoted to be emulsified, and the emulsifying and oil washing action of an oil displacement system in the stratum deep is enhanced; the viscous oil displacement system has the advantages that the viscous oil is stripped to disperse and move under the action of the oil displacement agent system, the resistance coefficient is increased due to the 'Jack effect' of dispersed crude oil, the injected viscosity-reducing oil displacement system with foaming performance plays a role in adjusting the injection profile when foaming is formed between a high-water-content region of a stratum and gas, meanwhile, the gas can be dissolved in the viscous oil, the viscosity of the crude oil is further reduced, the fluidity of the crude oil is improved, and the oil washing efficiency and the sweep efficiency in the oil displacement process are remarkably improved.
Detailed Description
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
In the present invention, "at least one" means one or two or more.
According to the invention, the oil displacement method comprises the following steps: injecting a front slug A, then injecting gas, sequentially and alternately injecting a viscosity-reducing oil displacement system B and gas, then injecting a protection slug C, and finally injecting water into an oil layer from an injection well;
wherein the pre-slug A is an aqueous solution containing a surfactant and/or a polymer, and the viscosity-reducing oil displacement system B contains the surfactant, alcohol, the polymer and water; the protection slug C is an aqueous solution containing a polymer.
According to the invention, the pre-slug A injected firstly can be adsorbed on the surface of the rock core to form a protective layer, so that the protective effect is achieved, the loss of the emulsifying agent injected subsequently can be reduced, meanwhile, the pre-slug A and the gas injected subsequently can form foam, the effect of section adjustment is achieved, and the viscosity-reducing oil displacement system B can be better contacted with thick oil. The pre-slug a capable of performing the above function is a surfactant and/or a polymer. The pre-slug a is typically used in the form of its aqueous solution and injected.
The surfactant can be one of anionic surfactant, nonionic surfactant and cationic surfactant or a mixture of various surfactants, and the excellent compatibility exists among the anionic surfactant, the nonionic surfactant and the cationic surfactant, so that the composite use of various types of surfactants can be realized. Specifically, examples of surfactants capable of achieving the above functions include, but are not limited to:
The anionic surfactant can be selected from one or more of alkylphenol ethoxylate sulfate, alkylphenol ethoxylate phosphate and alkylphenol ethoxylate carboxylate; alkylphenol ethoxylate sulfate is preferred. Wherein, the alkyl in the alkylphenol ethoxylate sulfate, the alkylphenol ethoxylate phosphate and the alkylphenol ethoxylate carboxylate can be respectively and independently C7-C12 alkyl, and the repeating unit of the ethoxy can be respectively and independently 5-50.
The nonionic surfactant can be selected from one or more of alkyl ammonium oxide, alkyl phenol polyoxyethylene ether, alkyl phenol polyoxyethylene ether sulfate and alkyl phenol polyoxyethylene ether phosphate; preferably an alkyl ammonium oxide. Wherein, the alkyl in the alkyl ammonium oxide, alkylphenol ethoxylates, alkyl polyoxyethylene ethers, alkylphenol polyoxyethylene ether sulfates and alkylphenol polyoxyethylene ether phosphates can be each independently C7-C12 alkyl; the repeating units of the ethoxy groups in the alkylphenol ethoxylates, the alkylphenol ethoxylate sulfates and the alkylphenol ethoxylate phosphates may each independently be 5 to 50.
The cationic surfactant is tetraalkylammonium chloride and/or tetraalkylammonium bromide, more preferably wherein at least one alkyl group is a long chain alkyl group containing 12-18 carbon atoms, the other alkyl groups are each independently selected from one of methyl, ethyl, propyl and butyl, more preferably wherein one or two alkyl groups are long chain alkyl groups containing 12-18 carbon atoms, the other alkyl groups are each independently selected from methyl or ethyl; most preferably, the cationic surfactant is one or more of dodecyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride and dimethyl dioctadecyl ammonium chloride. Most preferably, the tetraalkyl ammonium chloride is one or more of dodecyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, and dimethyl dioctadecyl ammonium chloride; the tetraalkyl ammonium bromide is one or more of dodecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium bromide and dimethyl dioctadecyl ammonium bromide.
Wherein the polymer may be various polymer polymers for oil displacement commonly used in the field of crude oil extraction, and preferably examples of polymer polymers capable of achieving the above functions include, but are not limited to: one or more of polyacrylamide, xanthan gum, and hydrophobically associating polymer. In a preferred embodiment of the invention, the polymer in the pre-slug a is polyacrylamide.
The concentration of the surfactant and/or polymer in the pre-slug a may be in an amount conventional in the art, and in general the total concentration of the surfactant and the aqueous polymer solution may be in the range of 1000-6000mg/L, preferably 2000-5000mg/L. If the pre-slug a is an aqueous solution containing a surfactant or a polymer, the "total concentration" refers to the concentration of the surfactant or the concentration of the polymer. If the pre-slug a is an aqueous solution containing surfactant and polymer, the "total concentration" refers to the concentration of surfactant and polymer, and the ratio of surfactant to polymer may be selected in a wide range, for example, the mass ratio of surfactant to polymer may be 1-3:1.
The pre-slug a may be obtained by various methods. For example: the pre-slug a may be obtained by mixing the surfactant and/or polymer with water under stirring. The stirring and mixing time is only required to ensure that the surfactant and/or the polymer are fully and uniformly mixed. The temperature of the mixing may be normal temperature.
According to the invention, after the pre-slug A is injected, the injected gas can form a foam section, and the injection section is further adjusted so as to protect the viscosity-reducing oil displacement system B which is injected later from being in contact with crude oil to be emulsified better, and the emulsifying performance is improved.
According to the invention, the viscosity-reducing oil displacement system B is an emulsified viscosity-reducing oil displacement system with foaming property. The viscosity-reducing oil displacement system B comprises a surfactant, alcohol, a polymer and water.
Wherein the surfactant may be selected from one or more of alkylphenol ethoxylate sulfate, alkylphenol ethoxylate carboxylate, alkyl polyglycoside, betaine, petroleum sulfonate, tetraalkylammonium chloride and tetraalkylammonium bromide. The alkyl in the alkylphenol ethoxylate sulfate and the alkylphenol ethoxylate carboxylate can be respectively and independently C7-C12 alkyl, and the repeating unit of the ethoxy can be respectively and independently 5-50; the alkyl group in the alkyl polyglycoside may be a C8-C16 alkyl group.
In a preferred embodiment of the invention, the surfactant is betaine, in combination with tetraalkylammonium chloride and/or tetraalkylammonium bromide.
The tetraalkylammonium chloride and tetraalkylammonium bromide wherein at least one alkyl group is each independently a long chain alkyl group having 12-18 carbon atoms, the other alkyl groups are each independently selected from one of methyl, ethyl, propyl and butyl, preferably wherein one or two alkyl groups are each independently a long chain alkyl group having 12-18 carbon atoms, the other alkyl groups are each independently selected from methyl or ethyl; most preferably, the tetraalkyl ammonium chloride is one or more of dodecyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, and dimethyl dioctadecyl ammonium chloride; the tetraalkyl ammonium bromide is one or more of dodecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium bromide and dimethyl dioctadecyl ammonium bromide.
The betaine has a structure shown in the following formula, wherein at least one R is long-chain alkyl containing 10-18 carbon atoms, other R are independently selected from one of methyl, ethyl, propyl and butyl, preferably, one R is long-chain alkyl containing 10-18 carbon atoms, and the other R is methyl; most preferably, the betaine is one or more of dodecyl dimethyl betaine, tetradecyl dimethyl betaine, hexadecyl dimethyl betaine, and octadecyl dimethyl betaine;
wherein the alcohol is monohydric alcohol with 1-12 carbon atoms, preferably monohydric alcohol with 2-6 carbon atoms; more preferably, the alcohol is ethanol and/or butanol.
Wherein, the polymer in the viscosity-reducing oil displacement system B can stabilize emulsion of the emulsified viscosity-reducing oil displacement system; preferably, the polymer is selected from at least one of polyacrylamide, xanthan gum, carboxymethyl cellulose, scleroglucan, polyvinyl alcohol, and hydrophobically associating polymer. In a preferred embodiment of the present invention, the polymer in the viscosity-reducing flooding system B is polyacrylamide.
According to the invention, the content of each component in the viscosity-reducing oil displacement system B has a wide selectable range, and preferably, from the viewpoint of further improving the recovery ratio of crude oil, the content of the surfactant is 0.01-3 wt%, the content of the alcohol is 0.01-0.2 wt%, the content of the polymer is 0.01-0.5 wt%, and the content of the water is 96.3-99.97 wt%, based on the total weight of the viscosity-reducing oil displacement system B;
More preferably, the content of the surfactant is 0.2 to 1 wt%, the content of the alcohol is 0.02 to 0.1 wt%, the content of the polymer is 0.1 to 0.3 wt% and the content of the water is 98.6 to 99.68 wt%, based on the total weight of the viscosity-reducing oil displacement system B.
According to the invention, the viscosity-reducing oil displacement system B can be obtained by various methods. For example: the viscosity-reducing oil displacement system B can be obtained by dissolving a polymer in part of water to obtain an aqueous polymer solution, and then mixing the aqueous polymer solution with a surfactant, alcohol and part of water under stirring. The stirring and mixing time is only required to ensure that the polymer is fully dissolved and uniformly mixed with other components. The temperature of the dissolution and mixing can be normal temperature.
According to the invention, the amount of each component in the preparation process of the viscosity-reducing oil displacement system B can be added according to the expected content of each component in the viscosity-reducing oil displacement system B, and the specific content of each component is specifically described above and is not described herein.
According to the invention, the emulsifying viscosity-reducing oil displacement system B and gas are injected alternately, so that the shearing action of the stratum deep emulsifying agent and the thick oil can be enhanced, the stratum deep thick oil is promoted to be emulsified, and the emulsifying oil washing action of the oil displacement system in the stratum deep is enhanced. Meanwhile, the injected emulsified viscosity-reducing oil displacement system with foaming performance plays a role in adjusting injection profile in the formation high water content area and the foam formation of injected gas, so that the oil washing efficiency and sweep efficiency in the oil displacement process are remarkably improved.
According to the invention, the finally injected protection slug C contains the polymer, so that the viscosity can be further increased, and the subsequent water flooding is facilitated.
According to the present invention, the protection slug C is an aqueous solution containing a high molecular polymer, and examples of the polymer capable of achieving the above functions include, but are not limited to: at least one of polyacrylamide, xanthan gum, carboxymethyl cellulose, scleroglucan, polyvinyl alcohol, and hydrophobically associating polymer. Preferably, the polymer is polyacrylamide. The concentration of the polymer in the protection slug C may be in an amount conventional in the art, and in general, the concentration of the polymer in the protection slug C may be 1000-5000mg/L, preferably 2000-3000mg/L.
The protection slug C may be obtained by various methods. For example: the protected slug C may be obtained by slowly dissolving the polymer in water under stirring. The stirring and mixing time only ensures that the high molecular polymer is fully dissolved. The temperature of the mixed dissolution may be normal temperature.
According to the invention, among the polymers in the pre-slug A, the viscosity-reducing oil displacement system B and the protection slug C, hydrophobic association polymers can be selected, and the hydrophobic association polymers comprise: the acrylic acid amide is prepared by using acrylic acid amide as a monomer and carrying out free radical copolymerization reaction with a hydrophobic monomer, and can be, for example, AP-P4, AP-P5 (for example, manufactured by Sichuan optical subunit company) and the like.
According to the invention, the polymers in the pre-slug A, the viscosity-reducing flooding system B and the protection slug C are preferably all polyacrylamides. The polyacrylamide comprises cationic polyacrylamide, anionic polyacrylamide and nonionic polyacrylamide, wherein,
the cationic polyacrylamide is obtained by copolymerizing cationic monomers such as DM (dimethyl diallyl ammonium chloride), DMC (2-methyl-acryloyloxyethyl trimethyl ammonium chloride), DMDAAC (dimethyl diallyl ammonium chloride or diallyl dimethyl ammonium chloride), DMAEMA (dimethylaminoethyl methacrylate) and the like with acrylamide.
The anionic polyacrylamide is a polyacrylamide containing an acrylamide structural unit and an acrylic acid structural unit and/or an acrylate structural unit, and can be obtained by partially hydrolyzing the polyacrylamide under alkaline conditions. The anionic polyacrylamide may have a degree of hydrolysis of 5 to 35 mole%. Preferably, the anionic polyacrylamide has a degree of hydrolysis of 10 to 30 mole%.
The nonionic polyacrylamide is a homopolymer of an acrylamide monomer, and is a linear polymer having a high molecular weight and a low ionic degree.
The degree of hydrolysis is generally referred to as the anionic polyacrylamide parameter. In the present invention, the degree of hydrolysis (i.e., the degree of ionization) refers to the percentage of the polyacrylamide molecules in which the amide groups are converted to carboxyl groups upon hydrolysis. In the present invention, the degree of hydrolysis is determined by the method specified in GB 12005.6-89.
Preferably, in order to further improve the synergistic effect of the flooding system and better achieve the objective of improving the recovery ratio, according to a specific embodiment of the present invention, when the surfactant or polymer in the front slug a is a cationic surfactant, a nonionic surfactant or a cationic polyacrylamide, the polymer in the viscosity-reducing flooding system B is preferably a polyacrylamide, and the polyacrylamide is preferably a cationic polyacrylamide, the polymer in the protection slug C is preferably a polyacrylamide, and the polyacrylamide is preferably a cationic polyacrylamide. According to another embodiment of the invention, when the surfactant or polymer in the pre-slug a is an anionic surfactant or an anionic polyacrylammonium, the polymer in the viscosity reducing displacement system B is preferably a polyacrylammonium, and the polyacrylammonium is preferably an anionic or nonionic polyacrylammonium, and the polymer in the protection slug C is preferably a polyacrylammonium, and the polyacrylammonium is preferably an anionic or nonionic polyacrylammonium, more preferably an anionic polyacrylammonium.
The molecular weight of the polyacrylamide is not particularly limited in the present invention, and the polyacrylamide may have a molecular weight well known to those skilled in the art. To further ensure that the displacement system has a certain apparent viscosity, increasing the stability of the emulsion, the polyacrylamide preferably has a viscosity average molecular weight of 500×10 4 -3000×10 4 The method comprises the steps of carrying out a first treatment on the surface of the More preferably, the polyacrylamide has a viscosity average molecular weight of 1500X 10 4 -2500×10 4 . In the present invention, the viscosity average molecular weight of the polyacrylamide is determined according to the method disclosed in GB/T12005.10-92.
According to the invention, as the viscosity-reducing oil displacement system B has good emulsifying property and lower interfacial tension and foaming property, the polymer can further play a role in prolonging and stabilizing the emulsion time of the oil displacement system, so that the viscosity of the oil displacement system can be effectively improved. Therefore, the degree of mineralization of the water in the viscosity-reducing flooding system B is not particularly required, and the degree of mineralization of the water may be conventional in the art or even water having a higher degree of mineralization, for example, the degree of mineralization of the water may be 0 to 25X 10 4 mg/L. The water as solvent in the viscosity-reducing flooding system B may have a mineralization degree of 0 to 20X 10 from the viewpoint of further reducing the cost of the method of the present invention under the condition of ensuring that the apparent viscosity of the finally obtained viscosity-reducing flooding system B satisfies the use requirement 4 mg/L, and calcium and magnesium ion content of 0-2×10 4 mg/L water, more preferably having a degree of mineralization of 2X 10 4 -10×10 4 mg/L, calcium and magnesium ion content of 0.1X10 × 4 -0.5×10 4 mg/L water. The water used as solvent in the pre-slug A and the protection slug C can also be mineralized to 0-20×10 4 mg/L, and calcium and magnesium ion content of 0-2×10 4 mg/L water, preferably having a degree of mineralization of 2X 10 4 -10×10 4 mg/L, calcium and magnesium ion content of 0.1X10 × 4 -0.5×10 4 mg/L water. The water having mineralization satisfying the above requirements may be water of various sources, for example:oilfield produced water having a mineralization degree satisfying the above requirements, oilfield injection water, water having a mineralization degree satisfying the above requirements obtained by mixing clean water (for example, water having a mineralization degree of 100 to 400 mg/liter) with oilfield produced water (typically, water having a mineralization degree of 3000 to 20000 mg/liter). In the present invention, the oilfield produced water may be treated prior to use by methods known to those skilled in the art (e.g., the methods specified in GB 50428-2007).
In the present invention, the mineralization degree refers to the total content of salts in water, such as: carbonates, bicarbonates, chlorides, sulfates, nitrates of metals such as calcium, magnesium, iron, aluminum, and manganese; and various sodium salts. The mineralization degree in the present invention is determined according to the gravimetric method specified in the Chinese industry Standard SL 79-1994.
According to the invention, preferably, the liquid and the gas are injected through periodical transformation, and the liquid and the gas are injected at a high-low alternating speed in the injection process, so that the shearing action of the deep stratum emulsifier and the thick oil can be further enhanced, the emulsification of the deep stratum thick oil is promoted, and the oil washing and sweep efficiency in the oil displacement process is improved. Thus, according to the present invention, the injection rates of the lead slug a, the viscosity-reducing flooding system B and the protection slug C are each independently 1-3 times the gas injection rate.
According to the invention, the gas in the oil displacement method can be various gases commonly used in the field of crude oil extraction for oil displacement, and examples of the gas capable of achieving the functions include, but are not limited to, CO 2 At least one of N2 and air, preferably CO 2 。
According to the invention, the volume ratio of the pre-slug A injected firstly to the gas injected subsequently in the oil displacement method has a wider selectable range, and from the perspective of further improving the recovery ratio of crude oil, the volume ratio of the pre-slug A injected firstly to the gas injected subsequently is 0.5-3:1, preferably 1-2:1 under the same pressure condition. According to the oil displacement method, the volume multiple of the front slug A is 0.01-0.1 times of the pore volume.
According to the oil displacement method, after the front slug A and the gas are injected, the volume ratio of the viscosity-reducing oil displacement system B to the gas injected each time is wide in selectable range, and from the perspective of further improving the recovery ratio of crude oil, the volume ratio of the viscosity-reducing oil displacement system B to the gas injected each time alternately is 1:0.5-1, preferably 1:0.8-1 under the same pressure condition. According to the invention, the volume multiple of the viscosity-reducing oil displacement system B injected each time is 0.01-0.1 times of the pore volume. The times of alternate injection are such that the total volume multiple of the injected viscosity-reducing oil displacement system B and the gas is preferably 0.1-0.6 times of the pore volume.
According to the oil displacement method, after the viscosity-reducing oil displacement system B and the gas are alternately injected, the volume multiple of the injected protection slug C is 0.01-0.1 time of the pore volume.
The oil displacement agent composition provided by the invention can be applied to the oil displacement of various oil reservoirs, and is particularly suitable for heavy oil reservoirs, wherein the viscosity of the heavy oil reservoirs in a stratum is less than 10000 Pa.s.
Besides the oil reservoir displacement by adopting the method of periodically and alternately injecting the liquid and the gas to improve the oil displacement efficiency, the method is not particularly limited to other conditions of the oil reservoir displacement, and can adopt methods known to those skilled in the art, for example, the method can also comprise the step of carrying out water flooding afterwards.
The present invention will be described in detail by examples.
The water content measurement method and the recovery ratio in the following examples are calculated by the following formulas:
during the core displacement process, sampling is carried out once every 2min at the core outlet end;
water content = volume of water/total volume of liquid in sample x 100%;
recovery = crude oil recovery/raw oil content x 100%.
Example 1
This example is presented to illustrate the preparation and performance of each slug provided by the present invention.
(1) Leading slug a: weighing 800g clear water (mineralization degree 0 mg/L), adding polyacrylamide (viscosity average molecular weight 3000×10) under stirring 4 Hydrolysis degree 20%) 3g, and stirring and dissolving for 4h.3g of dimethyl dioctadecyl ammonium chloride serving as a cationic surfactant is added, water is added to 1000g, and stirring is carried out for 20-30min until complete dissolution.
Viscosity-reducing oil displacement system B: weighing 800g clear water (mineralization degree 0 mg/L), adding polyacrylamide (viscosity average molecular weight 3000×10) under stirring 4 Hydrolysis degree 20%) 3g, and stirring and dissolving for 4h. Adding 3g of dimethyl dioctadecyl ammonium chloride serving as a cationic surfactant, adding 3g of octadecyl dimethyl betaine, adding 0.5g of ethanol, adding 1000g of water, and stirring for 20-30min until the mixture is completely dissolved.
Protection slug C: weighing 800g clear water (mineralization degree 0 mg/L), adding polyacrylamide (viscosity average molecular weight 3000×10) under stirring 4 Hydrolysis degree 20%) 3g, and stirring and dissolving for 4h. Adding water to 1000g, stirring for 20-30min to dissolve completely.
(2) Taking the pre-slug A, the viscosity-reducing oil displacement system B and thick oil (viscosity is 9600mPa.s at 50 ℃), and measuring interfacial tension at 70 ℃ by adopting Model TX500C interfacial tension to obtain a total of 1.8X10 respectively -4 mN/m and 5.3X10 -3 mN/m. In a 100mL beaker, respectively taking 30g of the pre-slug A and the viscosity-reducing oil displacement system B, adding 70g of thick oil, placing the beaker in a water bath with the temperature of 70 ℃ for 2h, and stirring for 3 min. At a shear rate of 7.34S using a Brookfield DV-II viscometer at 70 DEG C -1 Under the condition, the viscosity of the mixed solution is measured to be 80mPa.s and 63mPa.s respectively.
Example 2
The embodiment is used for explaining the use effect of the oil displacement method on the thickened oil recovery ratio improvement.
An enhanced oil recovery experiment (flooding system same as in example 1) was performed using cores with a specification of 4.5mm×4.5mm×300mm and a permeability of 3000 md. Drying the core, vacuumizing saturated water, saturating thick oil at 70 ℃ (same as in example 1), and aging for 48 hours. (1) 1.5mL/min injection rate water drive to 95% water by volume. (2) The pre-slug A0.05 PV was injected at an injection rate of 1.5mL/min and CO was injected at an injection rate of 1.0mL/min 2 0.05PV; (3) Injecting the viscosity-reducing oil displacement system B0.05PV at an injection speed of 1.5mL/min, and injecting CO at an injection speed of 1.0mL/min 2 The alternate injection was repeated for 3 cycles at 0.05 PV. (4) At an injection rate of 1.5mL/minInjecting a protection slug C0.05 PV; (5) The water flooding was continued to 95% by volume water at an injection rate of 1.5 mL/min.
Experimental results: the water flooding recovery ratio is 22.5%; the water content is reduced from 95% to 61% by volume and is reduced by 34% after the oil displacement agent is injected; the recovery ratio is increased by 56.0 percent, and the recovery ratio is improved by 33.5 percent.
Example 3
This example is presented to illustrate the preparation and performance of each slug provided by the present invention.
(1) High mineralization degree water (mineralization degree 100000mg/L, wherein Ca 2+ Concentration: 10000 mg/L), and preparing a pre-slug A, a viscosity-reducing oil displacement system B and a protection slug C. The preparation method is the same as in example 1.
(2) Taking the pre-slug A, the viscosity-reducing oil displacement system B and thick oil (viscosity is 9600mPa.s at 50 ℃), and measuring interfacial tension at 70 ℃ by adopting Model TX500C interfacial tension to obtain 3.9X10 respectively -4 mN/m and 6.3X10 -3 mN/m. In a 100mL beaker, respectively taking 30g of the pre-slug A and the viscosity-reducing oil displacement system B, adding 70g of thick oil, placing the beaker in a water bath with the temperature of 70 ℃ for 2h, and stirring for 3 min. At a shear rate of 7.34S using a Brookfield DV-II viscometer at 70 DEG C -1 Under the condition, the viscosity of the mixed solution is measured to be 60mPa.s and 43mPa.s respectively.
Example 4
The embodiment is used for explaining the use effect of the oil displacement method on the thickened oil recovery ratio improvement.
An enhanced oil recovery experiment (flooding system same as example 3) was performed using cores with a specification of 4.5mm×4.5mm×300mm and a permeability of 3000 md. Drying the core, vacuumizing saturated water, saturating thick oil at 70 ℃ (same as in example 1), and aging for 48 hours. (1) 1.5mL/min injection rate water drive to 95% water by volume. (2) The pre-slug A0.05PV was injected at an injection rate of 1.5mL/min and CO was injected at an injection rate of 1.0mL/min 2 0.05PV; (3) Injecting the viscosity-reducing oil displacement system B0.05PV at an injection speed of 1.5mL/min, and injecting CO at an injection speed of 1.0mL/min 2 The alternate injection was repeated for 3 cycles at 0.05 PV. (4) Injecting the protection slug C0.05 PV at an injection rate of 1.5 mL/min; (5) The water flooding was continued to 95% by volume water at an injection rate of 1.5 mL/min.
Experimental results: the water flooding recovery ratio is 21.7%; the water content is reduced from 95 to 69% by volume after the oil displacement agent is injected, and the water content is reduced by 26%; the recovery ratio is increased by 53.0 percent, and the recovery ratio is improved by 31.3 percent.
Example 5
This example is presented to illustrate the preparation and performance of each slug provided by the present invention.
(1) High mineralization degree water (mineralization degree 200000mg/L, wherein Ca 2+ Concentration: 20000 mg/L), a pre-slug A, a viscosity-reducing oil displacement system B and a protection slug C are prepared. The preparation method is the same as in example 1.
(2) Taking the pre-slug A, the viscosity-reducing oil displacement system B and thick oil (viscosity is 9600mPa.s at 50 ℃), and measuring interfacial tension at 70 ℃ by adopting Model TX500C interfacial tension to obtain a total of 1.9X10 respectively -3 mN/m and 7.3X10 -3 mN/m. In a 100mL beaker, respectively taking 30g of the pre-slug A and the viscosity-reducing oil displacement system B, adding 70g of thick oil, placing the beaker in a water bath with the temperature of 70 ℃ for 2h, and stirring for 3 min. At a shear rate of 7.34S using a Brookfield DV-II viscometer at 70 DEG C -1 Under the condition, the viscosity of the mixed solution is measured to be 68mPa.s and 53mPa.s respectively.
Example 6
The embodiment is used for explaining the use effect of the oil displacement method on the thickened oil recovery ratio improvement.
An enhanced oil recovery experiment (flooding system same as example 5) was performed using cores with a specification of 4.5mm×4.5mm×300mm and a permeability of 3000 md. Drying the core, vacuumizing saturated water, saturating thick oil at 70 ℃ (same as in example 1), and aging for 48 hours. (1) 1.5mL/min injection rate water drive to 95% water by volume. (2) The pre-slug A0.05PV was injected at an injection rate of 1.5mL/min and CO was injected at an injection rate of 1.0mL/min 2 0.05PV; (3) Injecting the viscosity-reducing oil displacement system B0.05PV at an injection speed of 1.5mL/min, and injecting CO at an injection speed of 1.0mL/min 2 The alternate injection was repeated for 3 cycles at 0.05 PV. (4) Injecting the protection slug C0.05 PV at an injection rate of 1.5 mL/min; (5) The water flooding was continued to 95% by volume water at an injection rate of 1.5 mL/min.
Experimental results: the water flooding recovery ratio is 20.5%; the water content is reduced from 95% by volume to 71% by volume after the oil displacement agent is injected, and the water content is reduced by 24%; the recovery ratio is increased by 49.0 percent, and the recovery ratio is increased by 28.5 percent.
Example 7
This example is presented to illustrate the preparation and performance of each slug provided by the present invention.
(1) High mineralization degree water (mineralization degree 100000mg/L, wherein Ca 2+ Concentration: 10000 mg/L) to prepare a pre-slug A, a viscosity-reducing oil displacement system B and a protection slug C. The specific configuration method comprises the following steps:
leading slug a: 800g of water was weighed, and under stirring, 3g of octadecyl dimethyl ammonium chloride, 1g of dodecyl dimethyl ammonium oxide and a surfactant, namely, polyacrylamide (viscosity average molecular weight: 3000X 10) 4 Hydrolysis degree 20%) 1g, and stirring and dissolving for 4h. Adding water to 1000g, and stirring for 20-30min.
Viscosity-reducing oil displacement system B: 800g of water was weighed and, with stirring, polyacrylamide (viscosity average molecular weight 3000X 10) 4 Hydrolysis degree 20%) 2g, and stirring and dissolving for 4h. Adding 5g of surfactant nonylphenol polyoxyethylene ether (10) sodium sulfate, adding 5g of octadecyl dimethyl betaine, adding 1.0g of ethanol, adding water to 1000g, and stirring for 20-30min until the mixture is completely dissolved.
Protection slug C: 800g of water was weighed and, with stirring, polyacrylamide (viscosity average molecular weight 3000X 10) 4 Degree of hydrolysis 20%) 5g, and stirring and dissolving for 4h. Adding water to 1000g, stirring for 20-30min to dissolve completely.
(2) Taking the pre-slug A, the viscosity-reducing oil displacement system B and thick oil (viscosity is 10000 Pa.s at 50 ℃), and measuring interfacial tension at 70 ℃ by adopting Model TX500C interfacial tension to obtain a viscosity of 1.5X10 respectively -2 mN/m and 6.9X10 -3 mN/m. In a 100mL beaker, respectively taking 30g of the pre-slug A and the viscosity-reducing oil displacement system B, adding 70g of thick oil, placing the beaker in a water bath with the temperature of 70 ℃ for 2 hours, and stirring for 3 minutes to form uniform oil-in-water emulsion. At a shear rate of 7.34S using a Brookfield DV-II viscometer at 70 DEG C -1 Under the condition, the viscosity of the mixed solution is measured to be 70mPa.s and 62mPa.s respectively.
Example 8
The embodiment is used for explaining the use effect of the oil displacement method on the thickened oil recovery ratio improvement.
An enhanced oil recovery experiment (flooding system same as in example 7) was performed using cores with a specification of 4.5mm×4.5mm×300mm and a permeability of 3000 md. Drying the core, vacuumizing saturated water, saturating thick oil at 70 ℃, and aging for 48 hours. (1) 1.5mL/min injection rate water drive to 95% water by volume. (2) The pre-slug A0.05 PV was injected at an injection rate of 1.5mL/min and CO was injected at an injection rate of 1.0mL/min 2 0.05PV; (3) Injecting the viscosity-reducing oil displacement system B0.05 PV at an injection speed of 1.5mL/min, and injecting CO at an injection speed of 1.0mL/min 2 The alternate injection was repeated for 3 cycles at 0.05 PV. (4) Injecting the protection slug C0.05 PV at an injection rate of 1.5 mL/min; (5) The water flooding was continued to 95% by volume water at an injection rate of 1.5 mL/min.
Experimental results: the water recovery ratio is 21.8%, and the water content is reduced from 95% to 70% by volume after the oil displacement agent is injected, and the water content is reduced by 25%; the recovery ratio is increased by 46.9 percent, and the recovery ratio is improved by 25.1 percent.
Example 9
This example is presented to illustrate the preparation and performance of each of the slugs provided.
(1) High mineralization degree water (mineralization degree 100000mg/L, wherein Ca 2+ Concentration: 10000 mg/L) to prepare a pre-slug A, a viscosity-reducing oil displacement system B and a protection slug C. The specific configuration method comprises the following steps:
leading slug a: 1000g of water is weighed, 1g of dodecyl dimethyl ammonium oxide serving as a surfactant is added under stirring, and stirring is carried out for 20-30min.
Viscosity-reducing oil displacement system slug B: 800g of water was weighed and, with stirring, polyacrylamide (viscosity average molecular weight 3000X 10) 4 Hydrolysis degree 20%) 1g, and stirring and dissolving for 4h. 5g of surfactant nonylphenol polyoxyethylene ether (10) sodium sulfate, 1.5g of octadecyl dimethyl betaine and 0.5g of ethanol are added, water is added to 1000g, and stirring is carried out for 20-30min until complete dissolution.
Protection slug C: 800g of water was weighed and, with stirring, polyacrylamide (viscosity average molecular weight 3000X 10) 4 Hydrolysis degree 20%) 1g, and stirring and dissolving for 4h. Adding water to 1000g, stirring for 20-30min to dissolve completely.
(2) Taking the solution of the pre-slug A and the viscosity-reducing oil displacement system B and thick oil (viscosity is 10000 Pa.s at 50 ℃), and measuring the interfacial tension at 70 ℃ by using a Model TX500C interfacial tensiometer to obtain a solution with the interfacial tension of 2.1 multiplied by 10 -2 mN/m and 9.0X10 -3 mN/m. In a 100mL beaker, 30g of the preposed slug A and the slug B are respectively taken and added with 70g of thick oil, the beaker is placed in a water bath with the temperature of 70 ℃ and kept constant for 2 hours, and the mixture is stirred for 3 minutes to form a uniform oil-in-water emulsion. At a shear rate of 7.34S using a Brookfield DV-II viscometer at 70 DEG C -1 Under the condition, the viscosity of the mixed solution is measured to be 112mPa.s and 89mPa.s respectively.
Example 10
The embodiment is used for explaining the use effect of the oil displacement method on the thickened oil recovery ratio improvement.
An enhanced oil recovery experiment was performed using cores with a gauge of 4.5mm x 300mm and a permeability of 3000md (flooding system same as in example 9). Drying the core, vacuumizing saturated water, saturating thick oil at 70 ℃, and aging for 48 hours. (1) 1.5mL/min injection rate water drive to 95% water by volume. (2) The pre-slug A0.05 PV was injected at an injection rate of 1.5mL/min and CO was injected at an injection rate of 1.0mL/min 2 0.05PV; (3) Injecting the viscosity-reducing oil displacement system B0.05 PV at an injection speed of 1.5mL/min, and injecting CO at an injection speed of 1.0mL/min 2 The alternate injection was repeated for 3 cycles at 0.05 PV. (4) Injecting the protection slug C0.05 PV at an injection rate of 1.5 mL/min; (5) The water flooding was continued to 95% by volume water at an injection rate of 1.5 mL/min.
Experimental results: the water recovery ratio is 22.4%, and the water content is reduced from 95% to 79% by volume after the oil displacement agent is injected, and the water content is reduced by 16%; the recovery ratio is increased by 45.5 percent, and the recovery ratio is increased by 23.1 percent.
Example 11
This example is presented to illustrate the preparation and performance of each slug provided by the present invention.
(1) High mineralization degree water (mineralization degree 100000mg/L, wherein Ca 2+ Concentration: 10000 mg/L) to prepare a pre-slug A, a viscosity-reducing oil displacement system B and a protection slug C. The specific configuration method comprises the following steps:
leading slug a: weigh 800g of water and add to the table with stirringSurfactant octadecyl dimethyl ammonium chloride 3g, dodecyl dimethyl ammonium oxide 1g, cationic polyacrylamide (viscosity average molecular weight 1200X 10) 4 1g of the ion degree is 10 percent) and is stirred and dissolved for 4 hours. Adding water to 1000g, and stirring for 20-30min.
Viscosity-reducing oil displacement system B: 800g of water was weighed and, with stirring, cationic polyacrylamide (viscosity average molecular weight 1200X 10) was added 4 Ion degree 10%) 2g, and stirring and dissolving for 4h. Adding 5g of surfactant nonylphenol polyoxyethylene ether (10) sodium sulfate, adding 5g of octadecyl dimethyl betaine, adding 1.0g of ethanol, adding water to 1000g, and stirring for 20-30min until the mixture is completely dissolved.
Protection slug C: 800g of water was weighed and, with stirring, cationic polyacrylamide (viscosity average molecular weight 1200X 10) was added 4 Ion degree 10%) 5g, and stirring and dissolving for 4h. Adding water to 1000g, stirring for 20-30min to dissolve completely.
(2) Taking the pre-slug A, the viscosity-reducing oil displacement system B and thick oil (viscosity is 10000 Pa.s at 50 ℃), and measuring interfacial tension at 70 ℃ by adopting Model TX500C interfacial tension to obtain a viscosity of 1.6X10 respectively -2 mN/m and 6.0X10 -3 mN/m. In a 100mL beaker, respectively taking 30g of the pre-slug A and the viscosity-reducing oil displacement system B, adding 70g of thick oil, placing the beaker in a water bath with the temperature of 70 ℃ for 2 hours, and stirring for 3 minutes to form uniform oil-in-water emulsion. At a shear rate of 7.34S using a Brookfield DV-II viscometer at 70 DEG C -1 Under the condition, the viscosity of the mixed solution is measured to be 58mPa.s and 49mPa.s respectively.
Example 12
The embodiment is used for explaining the use effect of the oil displacement method on the thickened oil recovery ratio improvement.
An enhanced oil recovery test (flooding system same as in example 11) was performed using cores with a specification of 4.5mm×4.5mm×300mm and a permeability of 3000 md. Drying the core, vacuumizing saturated water, saturating thick oil at 70 ℃, and aging for 48 hours. (1) 1.5mL/min injection rate water drive to 95% water by volume. (2) The pre-slug A0.05 PV was injected at an injection rate of 1.5mL/min and CO was injected at an injection rate of 1.0mL/min 2 0.05PV; (3) Injecting the viscosity-reducing oil displacement system B0.05 PV at an injection speed of 1.5mL/min and injecting at an injection speed of 1.0mL/minVelocity of entry CO injection 2 The alternate injection was repeated for 3 cycles at 0.05 PV. (4) Injecting the protection slug C0.05 PV at an injection rate of 1.5 mL/min; (5) The water flooding was continued to 95% by volume water at an injection rate of 1.5 mL/min.
Experimental results: the water recovery ratio is 23.5%, and the water content is reduced from 95% by volume to 65.5% by volume after the oil displacement agent is injected, and is reduced by 29.5%; the recovery ratio is increased by 50.5 percent, and the recovery ratio is improved by 27.0 percent.
Comparative example 1
This comparative example is used to illustrate the use of different injection modes to drive oil.
An enhanced oil recovery experiment (flooding system same as in example 1) was performed using cores with a specification of 4.5mm×4.5mm×300mm and a permeability of 3000 md. Drying the core, vacuumizing saturated water, saturating thick oil at 70 ℃ (same as in example 1), and aging for 48 hours. (1) 1.5mL/min injection rate water drive to 95% water by volume. (2) Injecting the pre-slug A0.05 PV at an injection rate of 1.5mL/min and CO at an injection rate of 1.5mL/min 2 0.05PV; (3) Injecting the viscosity-reducing oil displacement system B0.15PV at an injection speed of 1.5mL/min, and injecting CO at an injection speed of 1.5mL/min 2 0.15PV. (4) Injecting the protection slug C0.05 PV at an injection rate of 1.5 mL/min; (5) The water flooding was continued to 95% by volume water at an injection rate of 1.5 mL/min.
Experimental results: the water flooding recovery ratio is 20.3%; the water content is reduced from 95% to 82% by volume after the oil displacement agent is injected, and 13% is reduced; the recovery ratio is increased by 38.4 percent, and the recovery ratio is improved by 18.1 percent.
Comparative example 2
This comparative example is used to illustrate the use of different injection modes to drive oil.
An enhanced oil recovery test (oil displacement agent 0.3 wt% petroleum sulfonate) was performed using cores with a gauge of 4.5mm×4.5mm×300mm and a permeability of 3000 md. Drying the core, vacuumizing saturated water, saturating thick oil at 70 ℃ (same as in example 1), and aging for 48 hours. (1) 1.5mL/min injection rate water drive to 95% water by volume. (2) Injecting the oil displacement agent at 0.05PV at an injection rate of 1.5mL/min, and injecting CO at an injection rate of 1.0mL/min 2 The alternate injection was repeated for 3 cycles at 0.05 PV. (3) The water flooding was continued to water 9 at an injection rate of 1.5mL/min5% by volume. Experimental results: the water flooding recovery ratio is 21.0%; the water content is reduced from 95% to 85% by volume and 10% by volume after the oil displacement agent is injected; the recovery ratio is increased by 33.8 percent, and the recovery ratio is improved by 12.8 percent.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (30)
1. An oil reservoir displacement method, which is characterized by comprising the following steps: injecting a front slug A, then injecting gas, sequentially and alternately injecting a viscosity-reducing oil displacement system B and gas, then injecting a protection slug C, and finally injecting water into an oil layer from an injection well;
wherein the pre-slug A is an aqueous solution containing a surfactant and/or a polymer, and the viscosity-reducing oil displacement system B contains the surfactant, alcohol, the polymer and water; the protection slug C is an aqueous solution containing a polymer;
in the viscosity-reducing oil displacement system B,
the surfactant is betaine and tetraalkylammonium chloride and/or tetraalkylammonium bromide, the betaine has a structure shown in the following formula, wherein at least one R is long-chain alkyl containing 10-18 carbon atoms, and other R are each independently selected from one of methyl, ethyl, propyl and butyl;
；
in the tetraalkyl ammonium chloride and the tetraalkyl ammonium bromide, at least one alkyl is a long-chain alkyl containing 12-18 carbon atoms independently, and the other alkyl is selected from one of methyl, ethyl, propyl and butyl independently.
2. The flooding method of claim 1, wherein, in said pre-slug a,
The surfactant is selected from one or more of anionic surfactant, nonionic surfactant and cationic surfactant;
the polymer is selected from one or more of polyacrylamide, xanthan gum and hydrophobically associating polymer.
3. The flooding method of claim 2, wherein, in said pre-slug a,
the anionic surfactant is selected from one or more of alkylphenol ethoxylate sulfate, alkylphenol ethoxylate phosphate and alkylphenol ethoxylate carboxylate, wherein each alkyl is independently C7-C12 alkyl, and each ethoxy repeating unit is independently 5-50;
the nonionic surfactant is selected from one or more of alkyl ammonium oxide, alkylphenol ethoxylates, alkylphenol ethoxylate sulfate and alkylphenol ethoxylate phosphate, wherein each alkyl is independently C7-C12 alkyl, and each ethoxy has independently 5-50 repeating units;
the cationic surfactant is tetraalkylammonium chloride and/or tetraalkylammonium bromide.
4. The method of displacing oil according to claim 3, wherein at least one alkyl group in the tetraalkylammonium chloride and/or tetraalkylammonium bromide is a long-chain alkyl group having 12 to 18 carbon atoms, and the other alkyl groups are each independently selected from one of methyl, ethyl, propyl and butyl.
5. The method of displacing oil according to claim 3, wherein one or two alkyl groups in the tetraalkylammonium chloride and/or tetraalkylammonium bromide are long-chain alkyl groups having 12 to 18 carbon atoms, and the other alkyl groups are each independently selected from methyl or ethyl.
6. The flooding method of claim 4, wherein said tetraalkylammonium chloride is one or more of dodecyltrimethylammonium chloride, cetyltrimethylammonium chloride, octadecyltrimethylammonium chloride, and dimethyldioctadecyl ammonium chloride; the tetraalkyl ammonium bromide is one or more of dodecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium bromide and dimethyl dioctadecyl ammonium bromide;
the polymer is polyacrylamide with a viscosity average molecular weight of 500×10 4 -3000×10 4 。
7. The flooding method of claim 2 or 3, wherein the total concentration of surfactant and aqueous polymer solution in the pre-slug a is 1000-6000mg/L.
8. The flooding method of claim 7, wherein the total concentration of surfactant and aqueous polymer solution in said pre-slug a is 2000-5000mg/L.
9. The flooding method of claim 1, wherein in the viscosity-reducing flooding system B,
the alcohol is monohydric alcohol with 1-12 carbon atoms;
the polymer is at least one selected from the group consisting of polyacrylamide, xanthan gum, carboxymethyl cellulose, scleroglucan, polyvinyl alcohol and hydrophobically associating polymer.
10. The flooding method of claim 9, wherein said alcohol is a monohydric alcohol having 2 to 6 carbon atoms.
11. The flooding method of claim 9, wherein in said viscosity-reducing flooding system B,
the alcohol is ethanol and/or butanol;
the polymer is polyacrylamide with viscosity average molecular weight of 500×10 4 -3000×10 4 。
12. The method of displacing oil according to claim 11, wherein one R is a long chain alkyl group having 10 to 18 carbon atoms and the other R is methyl.
13. The flooding method of claim 11, wherein the betaine is one or more of dodecyl dimethyl betaine, tetradecyl dimethyl betaine, hexadecyl dimethyl betaine, and octadecyl dimethyl betaine.
14. The method of displacing oil according to claim 11, wherein one or two alkyl groups are each independently a long chain alkyl group having 12 to 18 carbon atoms, and the other alkyl groups are each independently selected from methyl or ethyl.
15. The method of displacing oil according to claim 11, wherein the tetraalkylammonium chloride is one or more of dodecyltrimethylammonium chloride, cetyltrimethylammonium chloride, octadecyltrimethylammonium chloride, and dimethyldioctadecyl ammonium chloride; the tetraalkyl ammonium bromide is one or more of dodecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium bromide and dimethyl dioctadecyl ammonium bromide.
16. The flooding method of claim 9 or 11, wherein the surfactant is present in an amount of 0.01-3 wt%, the alcohol is present in an amount of 0.01-0.2 wt%, the polymer is present in an amount of 0.01-0.5 wt%, and the water is present in an amount of 96.3-99.97 wt%, based on the total weight of the viscosity-reducing flooding system B.
17. The flooding method of claim 16, wherein said surfactant is present in an amount of 0.2-1 wt%, said alcohol is present in an amount of 0.02-0.1 wt%, said polymer is present in an amount of 0.1-0.3 wt%, and water is present in an amount of 98.6-99.68 wt%, based on the total weight of said viscosity-reducing flooding system B.
18. The flooding method of claim 1, wherein, in said protection slug C,
The polymer is at least one selected from the group consisting of polyacrylamide, xanthan gum, carboxymethyl cellulose, scleroglucan, polyvinyl alcohol and hydrophobically associating polymer.
19. The flooding method of claim 1, wherein the polymer is a polyacrylamide having a viscosity average molecular weight of 500 x 10 4 -3000×10 4 。
20. The flooding method of claim 17, wherein the concentration of the aqueous polymer solution in said guard slug C is 1000-5000mg/L.
21. The flooding method of claim 20, wherein the concentration of the aqueous polymer solution in said guard slug C is 2000-3000mg/L.
22. The flooding method of claim 1, wherein the mineralization of water in the pre-slug a, the viscosity-reducing flooding system B and the protection slug C is 0-20 x 10 4 mg/L, and calcium and magnesium ion content of 0-2×10 4 mg/L。
23. The flooding method of claim 22, wherein the mineralization of water in the pre-slug a, the viscosity-reducing flooding system B, and the protection slug C is 2 x 10 4 -10×10 4 mg/L, calcium and magnesium ion content of 0.1X10 × 4 -0.5×10 4 mg/L。
24. The flooding method of claim 1, wherein the gas is selected from CO 2 、N 2 And at least one of air.
25. The flooding method of claim 1, wherein the volume ratio of pre-slug a injected first to gas injected subsequently is 0.5-3:1 under the same pressure conditions; under the same pressure, the volume ratio of the viscosity-reducing oil displacement system B to the gas injected each time is 1:0.5-1.
26. The flooding method of claim 25, wherein the volume ratio of pre-slug a injected first to gas injected subsequently is 1-2:1 under the same pressure conditions.
27. The flooding method of claim 25, wherein the volume ratio of the viscosity reducing flooding system B to the gas per injection is 1:0.8-1 under the same pressure conditions.
28. The flooding method of claim 1 or 25, wherein the volume multiple of the pre-slug a is 0.01-0.1 times the pore volume, the volume multiple of the viscosity-reducing flooding system B per injection is 0.01-0.1 times the pore volume, and the number of injections is alternated so that the total volume multiple of the viscosity-reducing flooding system B and the gas injected is 0.1-0.6 times the pore volume, and the volume multiple of the protection slug C is 0.01-0.1 times the pore volume.
29. The flooding method of claim 28, wherein the injection rates of the lead slug a, the viscosity-reducing flooding system B, and the guard slug C are each independently 1-3 times the gas injection rate.
30. The method of displacing oil of claim 1, wherein the reservoir is a heavy oil reservoir having a viscosity of less than 10000 mpa.s in the formation.
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| CN110439517B (en) * | 2019-07-12 | 2021-09-17 | 浙江海洋大学 | Oil displacement method suitable for heavy oil reservoir |
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| CN115418211B (en) * | 2022-11-07 | 2023-06-23 | 山东东方盛嘉石油科技有限责任公司 | Thickened oil viscosity-reducing oil displacement agent and preparation method thereof |
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