CN115124989A - Viscosity-reducing cold recovery method for thickened oil and application thereof - Google Patents
Viscosity-reducing cold recovery method for thickened oil and application thereof Download PDFInfo
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Abstract
The invention relates to a viscosity-reducing cold recovery method for thick oil and application thereof. In the process of exploiting the thick oil, injecting a viscosity-reducing cold recovery agent into a stratum or performing stewing after the viscosity-reducing cold recovery agent and gas are combined and injected into the stratum in a slug mode to reduce the viscosity of the thick oil; the viscosity-reducing cold recovery agent is selected from at least one of an active high-molecular viscosity reducer and a surfactant; the active high-molecular viscosity reducer contains a series of active groups, and the active groups comprise heterocyclic groups and aromatic groups. The viscosity-reducing cold recovery agent used by the method is an active high-molecular viscosity reducer and/or a surfactant, can spontaneously contact with the thick oil without stirring, quickly disperse the thick oil, strip, carry and transport the thick oil, efficiently reduce the viscosity and relieve the blockage, and is beneficial to thick oil stratum flow and shaft lifting. The method disclosed by the invention is technically feasible and obvious in economic benefit when applied to thick oil recovery, and has wide application prospect and popularization value.
Description
Technical Field
The invention belongs to the technical field of thickened oil exploitation, and particularly relates to a thickened oil viscosity reduction cold recovery method and application thereof.
Background
China has abundant thickened oil resources, the thickened oil is becoming the most important energy in the 21 st century, and the thickened oil is estimated to be more than ten times higher than the conventional crude oil resources by related experts. The thickened oil resource is widely distributed and is found in almost all oil producing countries. In the oil field being exploited, the average recovery ratio of the thickened oil is less than 20%, and the development potential is huge. At present, a plurality of heavy oil exploitation methods have been developed at home and abroad, mainly steam huff-puff thermal exploitation is taken as the main method at present, but the yield is decreased rapidly in the later period of multiple rounds of huff-puff, the production period is short, the oil-steam ratio is low, the difficulty in stable production is high, and the casing damage caused by steam injection is frequent. Therefore, people hope that the new method improves the development effect, and the thick oil viscosity reduction cold recovery technology brings a new idea for thick oil recovery.
The patent (CN111577228A) reports a nitrogen atomization dispersion composite auxiliary agent heavy oil cold production method; patent (CN111004616A) reports a cold recovery stimulation self-emulsifying corrosion-inhibition viscosity reducer for heavy oil reservoir and a preparation method and application thereof; the patent (CN110630233A) reports a heavy oil cold production process suitable for a shallow well layer; patent (CN108729893A) reports a foam composite cold recovery method for improving recovery efficiency of heavy oil reservoir, which mainly comprises: alternately injecting the thick oil viscosity-reducing oil displacement agent, water and the polymer composite foam oil displacement system into a water injection well, and then performing water flooding; the invention can effectively improve the recovery ratio of the thickened oil under the non-heating condition, and the recovery ratio is improved by more than 15%. Patent (CN107893648A) reports a carbon dioxide energy storage high-pressure viscosity reduction cold recovery method applied to heavy oil reservoirs. The patent (CN103899286A) reports a method for cold recovery of thick oil at the edge of a reservoir structure, which is applied to the recovery of the thick oil in an oil field. The patent (CN103510932A) reports a chemical cold-production method suitable for a middle-deep layer low-permeability heavy oil reservoir.
The viscosity reducer in the existing viscosity reduction cold recovery technology for the thickened oil is mainly prepared by compounding a small molecular surfactant, the viscosity reduction is mainly realized by reducing the oil-water interfacial tension, the small molecular surfactant cannot permeate the thickened oil generally, the viscosity reduction efficiency is low, and the universality of most viscosity reducers is poor. Therefore, there is a need in the art to further develop the technology for viscosity reduction and cold recovery of heavy oil.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a novel method for viscosity reduction and cold recovery of thick oil, wherein a series of active groups are arranged on a molecular branched chain of an active high-molecular viscosity reducer in the viscosity reduction and cold recovery agent adopted by the method, the aromatic groups can be spontaneously embedded between aromatic sheets of asphaltene and colloid, complex aggregates of the asphaltene and the colloid are dispersed, other heterocyclic groups and interface active groups inhibit the re-aggregation of the aromatic groups and the interface active groups, the purpose of efficient viscosity reduction from inside to outside is realized, the thick oil can be spontaneously contacted with the thick oil without stirring, the thick oil is rapidly dispersed, stripped, carried and transported, the blockage is removed efficiently, and the thick oil stratum flow and the shaft lifting are facilitated. Meanwhile, the method is simple in field operation, safe and reliable, has wide application prospect and popularization value, and can obtain a good oil increasing effect.
Therefore, the invention provides a method for reducing viscosity and cold producing thick oil, which comprises the following steps: in the process of exploiting the thick oil, injecting the viscosity-reducing cold recovery agent into the stratum or injecting the viscosity-reducing cold recovery agent and gas into the stratum in a combined slug type manner and then stewing to reduce the viscosity of the thick oil; the viscosity-reducing cold recovery agent is selected from at least one of an active high-molecular viscosity reducer and a surfactant;
the active high-molecular viscosity reducer contains a series of active groups, and the active groups comprise heterocyclic groups and aromatic groups.
In some preferred embodiments of the present invention, the viscosity-reducing cold recovery agent is a mixture of an active polymeric viscosity-reducing agent and a surfactant.
In some more preferred embodiments of the invention, the mass ratio of the active high-molecular viscosity reducer to the surfactant in the viscosity-reducing cold recovery agent is 1 (1-10). In some specific embodiments of the present invention, the mass ratio of the active high molecular viscosity reducer to the surfactant in the viscosity-reducing cold recovery agent may be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1: 10. In some preferred embodiments of the invention, the mass ratio of the active high-molecular viscosity reducer to the surfactant in the viscosity-reducing cold recovery agent is 1 (2-6).
The viscosity-reducing cold recovery agent used by the invention is an active high-molecular viscosity reducer and/or surfactant, can spontaneously contact with the thick oil without stirring, quickly disperse the thick oil, strip, carry and transport the thick oil, efficiently reduce the viscosity and relieve the blockage, and is beneficial to thick oil stratum flow and shaft lifting.
In some embodiments of the present invention, the active polymeric viscosity reducer is prepared by reacting a monomer, a first base solution, an alcohol, and an initiator.
In some preferred embodiments of the present invention, the mass ratio of the monomer, the base, the alcohol and the initiator in the first alkali solution is 1 (0.05-0.6) to (0.001-0.03) to (0.0005-0.01).
In other preferred embodiments of the present invention, the reaction temperature is 40 to 80 ℃, and the reaction time is 4 to 10 hours.
In some specific embodiments of the invention, each monomer is added into a container according to a required molar ratio, then alcohol and a first alkali solution are added and mixed uniformly, finally an initiator (such as ammonium persulfate and sodium bisulfite) is added and reacts for 4-10 hours at a temperature of 40-80 ℃ to obtain a reaction product, and the reaction product is purified and crushed to obtain the active polymer viscosity reducer.
In some embodiments of the invention, the monomer is selected from at least two of N-vinyl pyrrolidone, acrylamide, methacrylic acid, acrylic acid, sodium styrene sulfonate, butylbenzene ene, and 2-acrylamide-2-methylpropane sulfonic acid, and the monomer contains N-vinyl pyrrolidone and at least one of sodium styrene sulfonate and butylbenzene ene. The monomer for preparing the active high-molecular viscosity reducer needs to comprise N-vinyl pyrrolidone and at least one of sodium styrene sulfonate and butylbenzene alkene, so that the prepared active high-molecular viscosity reducer contains heterocyclic groups and aromatic groups.
The active high-molecular viscosity reducer synthesized by the monomers has a series of active groups on a molecular branched chain, wherein the aromatic groups can be spontaneously embedded between aromatic sheets of asphaltene and colloid, complex aggregates of the asphaltene and the colloid are broken up, other heterocyclic groups and interface active groups inhibit the secondary aggregation of the aromatic groups, the purpose of efficient viscosity reduction from inside to outside is realized, the viscosity reducer can be spontaneously contacted with thick oil under the condition of no stirring, the thick oil is rapidly dispersed, stripped, carried and transported, the efficient viscosity reduction and blockage removal are realized, and the thick oil stratum flow and the shaft lifting are facilitated.
In other specific embodiments of the present invention, the first alkali solution is selected from any one of a potassium hydroxide solution, a sodium hydroxide solution, a calcium hydroxide solution, a sodium carbonate solution, and a sodium bicarbonate solution. The first alkali solution is used for adjusting the pH value of a reaction system to be required (such as 7-11).
In some embodiments of the invention, the alcohol is selected from any one of thiol, ethanol, isopropanol, n-butanol and n-pentanol. The alcohol is used as a molecular weight regulator of a reaction system, so that the number average molecular weight of the prepared active high-molecular viscosity reducer is between 100 and 800 ten thousand.
In other embodiments of the present invention, the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium bisulfite.
In some embodiments of the present invention, the surfactant is prepared by reacting at least one selected from the group consisting of polyvinyl alcohol, sulfonate, and aromatic cyclic acid with the second alkali solution.
In the present invention, the amount of the component for preparing the surfactant is not specifically limited. In general, the amount of the components used to prepare the surfactant will be routinely selected by those skilled in the art.
In some preferred embodiments of the present invention, the reaction temperature is 40 to 60 ℃, and the reaction time is 1 to 3 hours.
In some embodiments of the invention, at least one of polyvinyl alcohol, sulfonate and aromatic cyclic acid is dissolved in water, and then a second alkali solution is added to the solution to perform mixed reaction for 1 to 3 hours at a temperature of 40 to 60 ℃ to obtain the surfactant.
In some embodiments of the invention, the sulfonate is selected from at least one of sodium dodecylbenzene sulfonate, sodium hexadecylbenzene sulfonate, sodium alpha-olefin sulfonate, and sodium methylene bis-naphthalene sulfonate.
In other embodiments of the present invention, the aromatic ring acid is selected from any one of benzoic acid, toluene-4-sulfonic acid, and p-toluenesulfonic acid;
in some embodiments of the present invention, the second alkali solution is selected from any one of a potassium hydroxide solution, a sodium carbonate solution and a sodium bicarbonate solution.
According to the method, the viscosity-reducing cold recovery agent and gas can be combined and injected into the stratum in a slug mode aiming at different oil reservoir conditions (such as heavy oil reservoirs with insufficient stratum energy). The gas has the viscosity reduction and energy increasing effects, and is synergistic with the cold recovery agent, thereby being beneficial to discharge assistance after measures and prolonging the production period.
In some embodiments of the invention, the gas is nitrogen or carbon dioxide. The amount of said gas is not specifically limited in the present invention. Generally, when the dosage of the viscosity-reducing cold recovery agent is 300 to 1000 tons, the dosage of the nitrogen can be 10000 to 50000 standard square, and the dosage of the carbon dioxide can be 100 to 300 tons.
In some embodiments of the invention, the dosage of the viscosity-reducing cold recovery agent is 0.1-2.0 wt% of the mass of the heavy oil. In some embodiments of the invention, the viscosity reducing cold recovery agent may be used in an amount of 0.1 wt%, 0.2 wt%, 0.45 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.2 wt%, 1.5 wt%, or 2.0 wt% of the mass of the thickened oil. In some preferred embodiments of the invention, the viscosity-reducing cold recovery agent is used in an amount of 0.2-1.5 wt% of the mass of the thick oil.
In some embodiments of the present invention, the soaking time is 1 to 20 days, preferably 3 to 15 days.
In some embodiments of the present invention, the method for viscosity reduction and cold recovery of heavy oil specifically comprises: in the process of thick oil exploitation, injecting the viscosity-reducing cold recovery agent into a stratum or injecting the viscosity-reducing cold recovery agent and gas into the stratum in a combined block mode according to the use amount of the viscosity-reducing cold recovery agent accounting for 0.1-2.0 wt% of the mass of the thick oil, stewing for 1-20 days to promote the cold recovery agent and gas to contact with heavy component asphaltenes and colloids in the thick oil and disperse complex aggregates, so that the viscosity of the thick oil is greatly reduced; the viscosity-reducing cold recovery agent is selected from at least one of active high-molecular viscosity reducer and surfactant; the active high-molecular viscosity reducer contains a series of active groups, and the active groups comprise heterocyclic groups and aromatic groups; the gas is nitrogen or carbon dioxide.
In a second aspect the invention provides the use of a method according to the first aspect of the invention in heavy oil recovery.
The method for viscosity reduction and cold recovery of the thickened oil is applied to thickened oil recovery, is technically feasible and has obvious economic benefit. And the construction process is simple, the site is safe and reliable, and the method has wide application prospect and popularization value. The method makes the thick oil of the low-efficiency well and the low-efficiency well which are originally mined by the steam injection method easy to be mined, and can obtain better oil increasing effect. Meanwhile, the method is suitable for oil reservoirs with middle-deep layers, near-bottom water, low permeability, sensitivity and the like, and thick oil wells with the side far from the well and casing damage and the like which are not suitable for steam injection. The field test has obvious effect, and the method is popularized and applied to oil fields such as victory, Henan, Jianghan and the like at present, the maximum oil increase of a single well exceeds 10 times after the measures, the maximum effective period exceeds 24 months, and the average oil increase of the single well per day is 3 tons. Compared with the last round of steam stimulation, the viscosity reduction cold recovery single well has equivalent oil increase, the cost is reduced by more than 40 percent, and the benefit development of the thick oil cold recovery is really realized.
The invention has the beneficial effects that: compared with other methods for exploiting thick oil, the method for viscosity reduction and cold recovery of thick oil has the unique technical advantages that: (1) the viscosity-reducing cold recovery agent is an active high-molecular viscosity reducer and/or surfactant, can spontaneously contact with the thick oil under the condition of no stirring, quickly disperse the thick oil, strip, carry and transport the thick oil, efficiently reduce the viscosity and relieve the blockage, and is favorable for the thick oil stratum flow and the shaft lifting. (2) Aiming at different oil reservoir conditions, nitrogen or carbon dioxide is used in a matching way, the viscosity reduction and energy increasing effects of the gas are realized, and the gas and a cold recovery agent are synergistic, so that the drainage assistance and the production period extension after measures are facilitated. (3) The tubular column can be kept, the oil sleeve is injected in the annular space, and the construction cost is reduced. (4) Relative to steam stimulation, green, low-carbon and environment-friendly. (5) The measure cost is low, and the cost is reduced by more than 40% relative to the steam throughput. (6) The field test has obvious effect, and the method is popularized and applied to oil fields such as victory, Henan, Jianghan and the like at present, the maximum oil increase of a single well exceeds 10 times after the measures, the maximum effective period exceeds 24 months, and the average oil increase of the single well per day is 3 tons. Compared with the last round of steam stimulation, the viscosity reduction cold recovery single well has equivalent oil increase, the cost is reduced by more than 40 percent, and the benefit development of the thick oil cold recovery is really realized.
Detailed Description
In order that the invention may be more readily understood, the invention will now be described in further detail with reference to the following examples, which are given by way of illustration only and are not intended to limit the scope of the invention. The starting materials or components used in the present invention may be commercially or conventionally prepared unless otherwise specified.
The analytical instruments used in the following examples: RV DV-II type programmable rotary viscometer (BROOKFIELD, USA).
Example 1:
viscosity-reducing cold recovery agent and gas: the viscosity-reducing cold recovery agent consists of an active high-molecular viscosity reducer and a surfactant, and the mass ratio of the active high-molecular viscosity reducer to the surfactant is 1: 2; the gas is nitrogen.
The monomer for preparing the active high-molecular viscosity reducer comprises acrylamide, N-vinyl pyrrolidone, 2-acrylamide-2-methylpropanesulfonic acid and butylbenzene alkene, and the molar ratio of the acrylamide to the N-vinyl pyrrolidone to the 2-acrylamide-2-methylpropanesulfonic acid to the butylbenzene alkene is 1:1:1: 3. The preparation process comprises the following steps: adding the monomers into a container, adding ethanol and a sodium hydroxide solution, uniformly mixing, finally adding an initiator (a mixture of ammonium persulfate and sodium bisulfite), reacting for 8 hours at 60 ℃ to obtain a reaction product, and purifying and crushing the reaction product to obtain the active high-molecular viscosity reducer; wherein the mass ratio of the monomer, the sodium hydroxide, the ethanol and the initiator is 1:0.2:0.02: 0.001.
The surfactant is prepared by reacting polyvinyl alcohol, sodium dodecyl benzene sulfonate and sodium bicarbonate at 50 ℃ for 2 hours, wherein the mass ratio of the polyvinyl alcohol to the sodium dodecyl benzene sulfonate to the sodium bicarbonate is 0.1:1: 0.05.
A small experiment: the total dosage of the viscosity-reducing cold recovery agent is 0.45 wt% of the mass of the thick oil, the oil-water mass ratio of the thick oil is 7:3, 0.45g of the viscosity-reducing cold recovery agent is dissolved in 43g of water, the dissolved viscosity-reducing cold recovery agent and 100g of the thick oil (the degassing viscosity at 50 ℃ is 15500mPa.S) are added into a 500ml reaction kettle, high-purity nitrogen is introduced, the reaction is carried out for 4 hours at the oil layer temperature of 55 ℃, the viscosity of the thick oil after the reaction is 640.15mPa.S, and the viscosity reduction rate reaches 95.87%.
Example 2:
viscosity-reducing cold recovery agent and gas: the viscosity-reducing cold recovery agent consists of an active high-molecular viscosity reducer and a surfactant, wherein the mass ratio of the active high-molecular viscosity reducer to the surfactant is 1: 3; the gas is carbon dioxide.
The monomer for preparing the active high-molecular viscosity reducer comprises N-vinyl pyrrolidone, acrylamide, methacrylic acid and sodium styrene sulfonate, and the molar ratio of the N-vinyl pyrrolidone, the acrylamide, the methacrylic acid and the sodium styrene sulfonate is 1:1:1: 3. The preparation process comprises the following steps: adding the monomers into a container, adding isopropanol and sodium hydroxide solution, uniformly mixing, finally adding an initiator (a mixture of ammonium persulfate and sodium bisulfite), reacting for 8 hours at 60 ℃ to obtain a reaction product, and purifying and crushing the reaction product to obtain the active high-molecular viscosity reducer; wherein the mass ratio of the monomer, the sodium hydroxide, the ethanol and the initiator is 1:0.2:0.02: 0.001.
The surfactant is prepared by reacting polyvinyl alcohol, sodium dodecyl benzene sulfonate and sodium hydroxide for 2 hours at 50 ℃, wherein the mass ratio of the polyvinyl alcohol to the sodium dodecyl benzene sulfonate to the sodium hydroxide is 0.9:1.2: 0.08.
A small experiment: the total dosage of the viscosity-reducing cold recovery agent is 0.6 wt% of the mass of the thick oil, the oil-water mass ratio of the thick oil is 7:3, 0.5g of the viscosity-reducing cold recovery agent is dissolved in 43g of water, the dissolved viscosity-reducing cold recovery agent and 100g of the thick oil (the degassing viscosity at 50 ℃ is 15500mPa.S) are added into a 500ml reaction kettle, carbon dioxide is introduced, the reaction is carried out for 4 hours at the oil layer temperature of 55 ℃, the viscosity of the thick oil after the reaction is 361.15mPa.S, and the viscosity reduction rate reaches 97.67%.
Example 3:
viscosity-reducing cold recovery agent and gas: the viscosity-reducing cold recovery agent consists of an active high-molecular viscosity reducer and a surfactant, and the mass ratio of the active high-molecular viscosity reducer to the surfactant is 1: 4; the gas is carbon dioxide.
The monomer for preparing the active high-molecular viscosity reducer comprises acrylamide, N-vinyl pyrrolidone, butylbenzene ene and 2-acrylamide-2-methyl propanesulfonic acid, and the molar ratio of the acrylamide to the N-vinyl pyrrolidone to the butylbenzene ene to the 2-acrylamide-2-methyl propanesulfonic acid is 1:1:3: 1. The preparation process comprises the following steps: adding the monomers into a container, then adding n-butanol and a sodium carbonate solution, uniformly mixing, finally adding an initiator (a mixture of ammonium persulfate and sodium bisulfite), reacting for 8 hours at 60 ℃ to obtain a reaction product, and purifying and crushing the reaction product to obtain the active high-molecular viscosity reducer; wherein the mass ratio of the monomer, the sodium carbonate, the n-butyl alcohol and the initiator is 1:0.25:0.025: 0.001.
The surfactant is prepared by reacting polyvinyl alcohol, alpha-sodium alkenyl sulfonate, p-toluenesulfonic acid and sodium hydroxide at 50 ℃ for 2 hours, wherein the mass ratio of the polyvinyl alcohol to the alpha-sodium alkenyl sulfonate to the p-toluenesulfonic acid to the sodium hydroxide is 0.7:1:0.05: 0.05.
A small experiment: the total dosage of the viscosity-reducing cold recovery agent is 0.5 wt% of the mass of the thick oil, the mass ratio of oil to water in the thick oil is 6:4, 0.5g of the viscosity-reducing cold recovery agent is dissolved in 66.7g of water, the solution and 100g of thick oil (the degassing viscosity at 50 ℃ is 15500mPa.S) are added into a 500ml reaction kettle, carbon dioxide is introduced, the reaction is carried out for 4 hours at the oil layer temperature of 55 ℃, the viscosity of the thick oil after the reaction is 584.35mPa.S, and the viscosity reducing rate reaches 96.23%.
Example 4:
viscosity-reducing cold recovery agent and gas: the viscosity-reducing cold recovery agent consists of an active high-molecular viscosity reducer and a surfactant, and the mass ratio of the active high-molecular viscosity reducer to the surfactant is 1: 6; the gas is nitrogen.
The monomer for preparing the active high-molecular viscosity reducer comprises acrylamide, acrylic acid, N-vinyl pyrrolidone and sodium styrene sulfonate; and the molar ratio of the acrylamide to the acrylic acid to the N-vinyl pyrrolidone to the sodium styrene sulfonate is 1:1:1: 3. The preparation process comprises the following steps: adding the monomers into a container, then adding n-butanol and a sodium carbonate solution, uniformly mixing, finally adding an initiator (a mixture of ammonium persulfate and sodium bisulfite), reacting for 8 hours at 60 ℃ to obtain a reaction product, and purifying and crushing the reaction product to obtain the active high-molecular viscosity reducer; wherein the mass ratio of the monomer, the sodium carbonate, the n-butyl alcohol and the initiator is 1:0.25:0.025: 0.001.
The surfactant is prepared by reacting sodium methylenedinaphthalenesulfonate, benzoic acid and potassium hydroxide at 50 ℃ for 2 hours, wherein the mass ratio of the sodium methylenedinaphthalenesulfonate to the benzoic acid to the potassium hydroxide is 1.2:0.05: 0.05.
A small experiment: the total dosage of the viscosity-reducing cold recovery agent is 0.7 wt% of the mass of the thick oil, the mass ratio of oil to water in the thick oil is 7:3, 0.7g of the viscosity-reducing cold recovery agent is dissolved in 43g of water, the solution and 100g of the thick oil (the degassing viscosity at 50 ℃ is 15500mPa.S) are added into a 500ml reaction kettle, high-purity nitrogen is introduced, the reaction is carried out for 3 hours at the oil layer temperature of 55 ℃, the viscosity of the thick oil after the reaction is 381.3mPa.S, and the viscosity reduction rate reaches 97.54%.
Example 5:
viscosity-reducing cold recovery agent and gas: the viscosity-reducing cold recovery agent and the gas in the example 1 are the same.
A small experiment: the total dosage of the viscosity-reducing cold recovery agent is 0.7 wt% of the mass of the thick oil, the mass ratio of oil to water in the thick oil is 7:3, 0.7g of the viscosity-reducing cold recovery agent is dissolved in 43g of water, the solution and 100g of the thick oil (the degassing viscosity at 50 ℃ is 245780 mPa. S) are added into a 500ml reaction kettle, high-purity nitrogen is introduced, the reaction is carried out for 4 hours at the oil layer temperature of 50 ℃, the viscosity of the thick oil after the reaction is 521mPa. S, and the viscosity-reducing rate reaches 97.88%.
Example 6:
viscosity-reducing cold recovery agent and gas: the viscosity-reducing cold recovery agent and the gas in the example 2 are the same.
A small experiment: the total dosage of the viscosity-reducing cold recovery agent is 0.7 wt% of the mass of the thick oil, the mass ratio of oil to water in the thick oil is 7:3, 0.7g of the viscosity-reducing cold recovery agent is dissolved in 43g of water, the solution and 100g of the thick oil (the degassing viscosity at 50 ℃ is 245780 mPa. S) are added into a 500ml reaction kettle, carbon dioxide is introduced, the reaction is carried out for 5 hours at the oil layer temperature of 50 ℃, the viscosity of the thick oil after the reaction is 216.3mPa. S, and the viscosity reducing rate reaches 99.12%.
Example 7:
viscosity-reducing cold recovery agent and gas: the viscosity-reducing cold recovery agent and the gas in example 3 were the same.
A small experiment: the total dosage of the viscosity-reducing cold recovery agent is 1.0 wt% of the mass of the thick oil, the mass ratio of oil to water in the thick oil is 8:2, 0.8g of the viscosity-reducing cold recovery agent is dissolved in 25g of water, the solution and 100g of the thick oil (the degassing viscosity at 50 ℃ is 245780 mPa. S) are added into a 500ml reaction kettle, carbon dioxide is introduced, the reaction is carried out for 3 hours at the oil layer temperature of 50 ℃, the viscosity of the thick oil after the reaction is 322mPa. S, and the viscosity reduction rate reaches 98.69%.
Example 8:
viscosity-reducing cold recovery agent and gas: the viscosity-reducing cold recovery agent and the gas in the example 4 are the same.
A small experiment: the total dosage of the viscosity-reducing cold recovery agent is 1.5 wt% of the mass of the thick oil, the mass ratio of oil to water in the thick oil is 7:3, 1.5g of the viscosity-reducing cold recovery agent is dissolved in 43g of water, the solution and 100g of the thick oil (the degassing viscosity at 50 ℃ is 245780 mPa. S) are added into a 500ml reaction kettle, high-purity nitrogen is introduced, the reaction is carried out for 4 hours at the oil layer temperature of 50 ℃, the viscosity of the thick oil after the reaction is 135.19mPa. S, and the viscosity reduction rate reaches 99.45%.
Example 9:
viscosity-reducing cold recovery agent and gas: the viscosity-reducing cold recovery agent is basically the same as the viscosity-reducing cold recovery agent and gas in example 1, except that the mass ratio of the active high-molecular viscosity-reducing agent to the surfactant is 1: 1.
A small experiment: the total dosage of the viscosity-reducing cold recovery agent is 0.45 wt% of the mass of the thick oil, the oil-water mass ratio of the thick oil is 7:3, 0.45g of the viscosity-reducing cold recovery agent is dissolved in 43g of water, the dissolved viscosity-reducing cold recovery agent and 100g of the thick oil (the degassing viscosity at 50 ℃ is 15500mPa.S) are added into a 500ml reaction kettle, high-purity nitrogen is introduced, the reaction is carried out for 4 hours at the oil layer temperature of 55 ℃, the viscosity of the thick oil after the reaction is 760.21mPa.S, and the viscosity reduction rate reaches 95.10%.
Example 10:
viscosity-reducing cold recovery agent and gas: the viscosity-reducing cold recovery agent only comprises an active high-molecular viscosity reducer, and the active high-molecular viscosity reducer and gas adopted by the viscosity-reducing cold recovery agent are the same as those in the example 1.
A small experiment: the total dosage of the viscosity-reducing cold recovery agent is 0.45 wt% of the mass of the thick oil, the oil-water mass ratio of the thick oil is 7:3, 0.45g of the viscosity-reducing cold recovery agent is dissolved in 43g of water, the dissolved viscosity-reducing cold recovery agent and 100g of the thick oil (the degassing viscosity at 50 ℃ is 15500mPa.S) are added into a 500ml reaction kettle, high-purity nitrogen is introduced, the reaction is carried out for 4 hours at the oil layer temperature of 55 ℃, the viscosity of the thick oil after the reaction is 940.43mPa.S, and the viscosity reduction rate reaches 93.94%.
Example 11
The liquid quantity and water content of the side bottom water heavy oil reservoir of the clear river oil zone rise after multiple rounds of thermal recovery, and the thermal recovery risk is high. In the process of exploiting the thick oil from the thick oil reservoir of the bottom water in the clear river oil zone, the viscosity-reducing cold recovery agent (the viscosity-reducing cold recovery agent in the same example 1) is injected into the stratum singly or in a combined manner with carbon dioxide in a slug manner according to the dosage that the mass of the viscosity-reducing cold recovery agent is 1.5 wt% of the mass of the thick oil, and the well is stewed for 15 days to promote the contact of the viscosity-reducing cold recovery agent and the carbon dioxide with heavy components of asphaltene and colloid in the thick oil and disperse complex aggregates, so that the macromolecular crude oil is emulsified into the micromolecular crude oil, the viscosity of the thick oil is greatly reduced, the flow capacity of the crude oil is improved, and meanwhile, the effects of thickening a water phase and changing the wettability of an oil-water interface are achieved. The flow ratio of oil and water is reduced, and the flow of crude oil is greatly improved under the action of edge-bottom water flooding, so that the purpose of increasing yield is achieved.
At present, the process is applied to the bottom-water heavy oil reservoir in the clear river oil area for 11 wells, the effective rate of the measure is 100 percent, the economic effective rate of the measure is 72.7 percent, the oil is increased by 3044 tons in an accumulated way at present, and the average effective period is 262 days.
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.
Claims (10)
1. A viscosity-reducing cold recovery method for thick oil comprises the following steps: in the process of exploiting the thick oil, injecting the viscosity-reducing cold recovery agent into the stratum or injecting the viscosity-reducing cold recovery agent and gas into the stratum in a combined slug type manner and then stewing to reduce the viscosity of the thick oil; the viscosity-reducing cold recovery agent is selected from at least one of an active high-molecular viscosity reducer and a surfactant;
the active high-molecular viscosity reducer contains a series of active groups, and the active groups comprise heterocyclic groups and aromatic groups.
2. The method according to claim 1, wherein the viscosity-reducing cold recovery agent is a mixture of an active high-molecular viscosity-reducing agent and a surfactant;
preferably, the mass ratio of the active high-molecular viscosity reducer to the surfactant in the viscosity-reducing cold recovery agent is 1 (1-10), and preferably 1 (2-6).
3. The method according to claim 1 or 2, wherein the active high molecular viscosity reducer is prepared by reacting a monomer, a first alkali solution, an alcohol and an initiator; preferably, the mass ratio of the monomer, the base in the first alkali solution, the alcohol and the initiator is 1 (0.05-0.6): 0.001-0.03): 0.0005-0.01; further preferably, the reaction temperature is 40-80 ℃, and the reaction time is 4-10 hours.
4. The method of claim 3, wherein the monomer is selected from at least two of N-vinylpyrrolidone, acrylamide, methacrylic acid, acrylic acid, sodium styrene sulfonate, butylbenzene ene, and 2-acrylamido-2-methylpropane sulfonic acid, and the monomer contains N-vinylpyrrolidone and at least one of sodium styrene sulfonate and butylbenzene;
and/or the first alkali solution is selected from any one of potassium hydroxide solution, sodium hydroxide solution, calcium hydroxide solution, sodium carbonate solution and sodium bicarbonate solution;
and/or the alcohol is selected from any one of mercaptan, ethanol, isopropanol, n-butanol and n-pentanol;
and/or the initiator is selected from at least one of ammonium persulfate, potassium persulfate and sodium bisulfite.
5. The method according to any one of claims 1 to 4, wherein the surfactant is prepared by reacting at least one selected from the group consisting of polyvinyl alcohol, sulfonate, and aromatic cyclic acid with a second alkali solution; preferably, the reaction temperature is 40-60 ℃, and the reaction time is 1-3 hours.
6. The method according to claim 5, wherein the sulfonate is selected from at least one of sodium dodecylbenzene sulfonate, sodium hexadecylbenzene sulfonate, sodium α -olefin sulfonate, and sodium methylenedinaphthalenesulfonate;
and/or the aromatic ring acid is selected from any one of benzoic acid, toluene-4-sulfonic acid and p-toluenesulfonic acid;
and/or the second alkali solution is selected from any one of a potassium hydroxide solution, a sodium carbonate solution and a sodium bicarbonate solution.
7. The method according to any one of claims 1 to 6, wherein the gas is nitrogen or carbon dioxide.
8. The method according to any one of claims 1 to 7, wherein the viscosity-reducing cold recovery agent is used in an amount of 0.1 to 2.0 wt%, preferably 0.2 to 1.5 wt% of the mass of the thick oil.
9. The method according to any one of claims 1 to 8, wherein the soaking time is 1 to 20 days, preferably 3 to 15 days.
10. Use of a method according to any one of claims 1-9 in heavy oil recovery.
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