CN110105936B - Temperature-resistant salt-tolerant foam profile control and flooding system suitable for complex oil reservoir and preparation method and application thereof - Google Patents

Temperature-resistant salt-tolerant foam profile control and flooding system suitable for complex oil reservoir and preparation method and application thereof Download PDF

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CN110105936B
CN110105936B CN201910421174.8A CN201910421174A CN110105936B CN 110105936 B CN110105936 B CN 110105936B CN 201910421174 A CN201910421174 A CN 201910421174A CN 110105936 B CN110105936 B CN 110105936B
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profile control
oil
stratum
control system
titanium dioxide
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CN110105936A (en
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赵海洋
王世洁
刘中云
刘宝增
李亮
李海霞
丁保东
任波
何龙
冯一波
焦保雷
秦飞
魏芳
杨利萍
甄恩龙
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China Petroleum and Chemical Corp
Sinopec Northwest Oil Field Co
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Sinopec Northwest Oil Field Co
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Abstract

The invention provides a profile control and flooding system, which comprises the following components in percentage by weight: 1 to 3 percent of nano titanium dioxide, 0.2 to 0.9 percent of hexadecyl trimethyl ammonium bromide, 0.01 to 0.3 percent of partially hydrolyzed polyacrylamide and the balance of water. The invention also provides a preparation method and application of the profile control and flooding system and an oil displacement method for an oil reservoir by adopting the profile control and flooding system. The profile control and flooding system is suitable for complex oil reservoirs with harsh conditions, has the characteristics of temperature resistance and salt tolerance, and can realize excellent oil displacement effect.

Description

Temperature-resistant salt-tolerant foam profile control and flooding system suitable for complex oil reservoir and preparation method and application thereof
Technical Field
The invention belongs to the technical field of oil exploitation, and particularly provides a temperature-resistant salt-resistant foam profile control system suitable for complex oil reservoirs and a preparation method and application thereof.
Background
After primary oil recovery and secondary oil recovery are carried out on various domestic oil fields, the water content of crude oil is stably increased, and most of the oil fields enter a tertiary oil recovery stage. In tertiary oil recovery, the water-oil fluidity ratio is changed by adding chemical substances, so that the crude oil recovery rate is improved, and currently, alkali flooding, polymer flooding, surfactant flooding, binary or ternary combination flooding and the like are commonly used. The foam system has the advantages of high apparent viscosity, defoaming in oil and stability in water, and the foam profile control technology is produced and successfully applied to the field of oil displacement and the like. However, under the influence of factors such as dilution of formation water, formation adsorption and the like, the effective concentration of the foaming agent in the foam system is gradually reduced in the migration process, the foam stability is poor, and the effective period is shortened.
The nano material is a new material which is paid much attention in recent years, the particle size of the nano particle is fine, and a large number of atoms in the crystal grain defects exist, so that the nano particle has characteristics which cannot be compared with many conventional particles, such as superplasticity, large specific surface area, high strength and the like. Nanoparticles have better thermal and chemical stability and thus can exist under severe formation conditions. Because the activity of a pure nano material is poor, the swept volume cannot be enlarged, and a good profile control effect cannot be achieved, the nano material is often used after high interfacial activity is obtained by compounding electrostatic interaction and a surfactant.
The Chinese invention patent application with the application number of 201811298872.5 discloses a temperature-resistant salt-resistant foam profile control and flooding system prepared from high-salinity formation water, which comprises the following components in parts by mass: 0.5 to 2 percent of nano silicon dioxide, 0.01 to 2 percent of tetradecyl hydroxysulfobetaine, 0.01 to 0.5 percent of partially hydrolyzed polyacrylamide, 0.01 to 0.3 percent of citrate and the balance of water, and discloses an oil displacement method adopting the temperature-resistant and salt-resistant foam profile control and flooding system. However, the oil displacement system needs more components and the preparation method is more complex.
The Chinese patent application with the application number of 201610936584.2 discloses a surfactant micelle oil displacement agent, which is a foam system obtained by compounding Sodium Dodecyl Sulfate (SDS) and silicon dioxide, but the temperature resistance of the surfactant micelle oil displacement agent is poor, and the applicable mineralization degree range is low due to the addition of certain counter ions. Because complex oil reservoir conditions are harsh (the temperature is 130 ℃, the total salinity is 220000mg/L), defoaming can easily occur under the conditions of high temperature and high salt by adopting a simple surfactant foam system, but most of the existing oil displacement foam systems have poor temperature resistance and salt resistance, and cannot be suitable for high-temperature and high-salt reservoirs.
Disclosure of Invention
The invention aims to provide a temperature-resistant salt-resistant foam profile control system suitable for complex oil reservoirs, and a preparation method and application thereof, aiming at the problems in the prior art.
In one aspect, the invention provides a profile control and flooding system, which comprises the following components in percentage by weight: 1 to 3 percent of nano titanium dioxide, 0.2 to 0.9 percent of hexadecyl trimethyl ammonium bromide, 0.01 to 0.3 percent of partially hydrolyzed polyacrylamide and the balance of water.
Further, the profile control and flooding system comprises the following components in percentage by weight: 1 to 2 percent of nano titanium dioxide, 0.5 to 0.9 percent of hexadecyl trimethyl ammonium bromide, 0.01 to 0.2 percent of partially hydrolyzed polyacrylamide and the balance of water;
preferably, the profile control and flooding system comprises the following components in percentage by weight: 2% of nano titanium dioxide, 0.9% of hexadecyl trimethyl ammonium bromide, 0.1% of partially hydrolyzed polyacrylamide and the balance of water.
Further, the nano titanium dioxide is hydrophilic self-dispersing nano titanium dioxide.
Further, the average particle size of the nano titanium dioxide is 10-30 nm, and preferably 30 nm.
Further, the molecular weight of the partially hydrolyzed polyacrylamide is 500-1200 ten thousand, and the hydrolysis degree is 5% -20%; preferably, the partially hydrolyzed polyacrylamide has a molecular weight of 700 ten thousand and a degree of hydrolysis of 10%.
Further, the water is simulated mineralized water.
In another aspect, the present invention provides a method for preparing a profile control system, comprising:
(1) adding cetyl trimethyl ammonium bromide into water to be dissolved to obtain a cetyl trimethyl ammonium bromide solution;
(2) adding nano titanium dioxide into the cetyl trimethyl ammonium bromide solution to obtain a mixed solution in which the nano titanium dioxide is uniformly dispersed;
(3) and adding the partially hydrolyzed polyacrylamide into the mixed solution, and uniformly stirring to obtain the profile control and flooding system.
On the other hand, the invention provides the application of the profile control and flooding system in oil displacement of an oil reservoir.
In another aspect, the present invention provides a method for displacing oil from an oil reservoir, comprising: a main slug including a profile control system is injected into the formation.
Further, the oil displacement method comprises the following steps:
step 1: injecting a pre-pretreatment slug into the stratum according to the volume injection amount of 0.1-1% of the pore volume of the stratum;
step 2: injecting a main section plug comprising the profile control system and nitrogen into the stratum according to the volume injection amount of 30-50% of the pore volume of the stratum;
and step 3: injecting a post-positioned protective slug into the stratum according to the volume injection amount of 0.1 to 1 percent of the pore volume of the stratum;
and 4, step 4: and (5) closing the well.
Further, in the step 1, the pre-pretreatment slug is a hexadecyl trimethyl ammonium bromide solution with the concentration of 0.1 mmol/L-0.5 mmol/L.
Further, in step 2, the profile control system and the nitrogen gas are alternately injected into the stratum according to the volume ratio of the profile control system and the nitrogen gas being 1: 1 to 1: 3 (preferably 1: 2).
Further, in step 3, the post-protection slug is a nano titanium dioxide solution with a mass concentration of 1% to 5% (preferably 3%).
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
(1) CTAB (cetyl trimethyl ammonium bromide) and nano TiO adopted by the invention2Can generate good synergistic effect, and the existence of CTAB can change the nano TiO2And the process is irreversible to ensure subsequent displacement effect and to make TiO2The foam is adsorbed on a gas-liquid interface, so that the interfacial viscoelasticity of the foam is obviously improved, and the foam stability is greatly improved; on the other hand, the cationic property of CTAB can change nano TiO2The position of (2) makes it be changeed and adsorbs on the rock, improves the profile control efficiency.
(2) Partially hydrolyzed HPAM (partially hydrolyzed polyacrylamide), CTAB and nano TiO in the invention2The mutual synergy of the components can play the role of temperature resistance and salt tolerance. Because CTAB's self long carbon chain can play the steric hindrance effect, and HPAM has certain flocculent and network structure, HPAM and CTAB twine, flocculate because of the adsorption effect, and at high temperature (for example 130 ℃), HPAM motion is hindered, can keep higher viscosity, and the temperature resistance is excellent. Nano TiO in solution2The charge repulsion with HPAM makes the form of HPAM more extended, further improves the salt tolerance of the system.
(3) The oil displacement system can form a flocculating constituent by winding HPAM in a high-temperature and high-salt environment, the flocculating constituent can effectively inhibit defoaming of foam, a bridging structure is formed in the foam, the stability of the foam system is enhanced, and meanwhile TiO2The Janus structure is adsorbed and formed on the gas-liquid interface, so that liquid in the foam can be kept, the liquid discharge rate of the foam is reduced, the solubility of gas in a liquid film is reduced, and the foam stability is enhanced.
(4) The profile control system can be suitable for high-temperature and high-salinity oil reservoirs, and the adopted nano TiO is2Has good temperature resistance, salt resistance and shearing resistance.
(5) The profile control system has good aging stability, and can still maintain stable volume and particle size after aging for two months under the condition of high temperature (such as 130 ℃).
(6) The profile control system can still maintain better structural strength after being aged for two months at high temperature (such as 130 ℃), can effectively block a crack, enables subsequent injection pressure to be maintained at a higher level, and can remarkably improve the swept volume of subsequent fluid.
(7) The profile control system of the invention does not add alkali, thus avoiding the adverse effect of alkali on the stratum.
(8) The system can meet the requirements of field preparation, is convenient and quick, has a simple oil displacement mode, and can improve the oil displacement effect of the system to the maximum extent by arranging a plurality of alternating oil displacement slugs.
Drawings
FIG. 1 shows the normal temperature morphology of the profile control system prepared in the first example.
FIG. 2 shows the morphology of the profile control system prepared in the first example after aging at 130 ℃ for 72 hours.
FIG. 3 shows the foam morphology formed after stirring the room temperature profile control system for 10 minutes.
FIG. 4 shows the foam morphology formed after 10 minutes of stirring of the profile control system after aging at 130 ℃ for 72 hours.
FIG. 5 shows the foam form of the room temperature profile control system after stirring for 10 minutes and then standing for 2 hours at room temperature.
FIG. 6 shows the foam morphology of the profile control system after aging at 130 ℃ for 72 hours, stirring for 10 minutes, and then standing at room temperature for 2 hours.
Detailed Description
The present invention will be described in detail with reference to the following embodiments in order to fully understand the objects, features and effects of the invention. The process of the present invention employs conventional methods or apparatus in the art, except as described below. The following noun terms have meanings commonly understood by those skilled in the art unless otherwise specified.
Aiming at the problems that most of the existing oil displacement foam systems are poor in temperature resistance and salt resistance and cannot be applied to high-temperature and high-salt reservoirs, the inventor of the invention provides a foam profile control and flooding system for improving the recovery efficiency of tertiary oil recovery through research, the foam profile control and flooding system is suitable for complex oil reservoirs with harsh conditions (the temperature is not lower than 130 ℃, and the mineralization degree is not lower than 220000mg/L), and nanoparticles are introduced into the conventional foam profile control and flooding system by the system, so that the interfacial properties of foam can be greatly changed, and the foam profile control and flooding system can stably exist under the conditions of high temperature and high salt and has good retention performance.
In a first aspect, the invention provides a profile control and flooding system, which comprises the following components in percentage by weight: 1 to 3 percent of nano titanium dioxide, 0.2 to 0.9 percent of hexadecyl trimethyl ammonium bromide, 0.01 to 0.3 percent of partially hydrolyzed polyacrylamide and the balance of water. Preferably, the profile control and flooding system of the invention comprises the following components in percentage by weight: 1 to 2 percent of nano titanium dioxide, 0.5 to 0.9 percent of hexadecyl trimethyl ammonium bromide, 0.01 to 0.2 percent of partially hydrolyzed polyacrylamide and the balance of water. More preferably, the profile control and flooding system of the invention comprises, in weight percent: 2% of nano titanium dioxide, 0.9% of hexadecyl trimethyl ammonium bromide, 0.1% of partially hydrolyzed polyacrylamide and the balance of water.
In the profile control system of the present invention, the nano titanium dioxide is preferably hydrophilic self-dispersing nano titanium dioxide. The hydrophilic self-dispersing nano titanium dioxide has high affinity to water and can be well dissolved in water. Preferably, the average particle size of the nano titanium dioxide is 10nm to 30nm, and more preferably, the average particle size of the nano titanium dioxide is 30 nm.
In the profile control system, the average molecular weight of the partially hydrolyzed polyacrylamide is 500-1200 ten thousand, and the hydrolysis degree is 5-20%. Preferably, the partially hydrolyzed polyacrylamide has an average molecular weight of 700 ten thousand and a degree of hydrolysis of 10%.
In the profile control system of the invention, the water can be simulated mineralized water, for example, the total mineralization of the simulated mineralized water is 220000mg/L, wherein Ca2+With Mg2+The ion concentration was 2000 mg/L.
The profile control system of the present invention comprises nano titanium dioxide, cetyl trimethyl ammonium bromide and partially hydrolyzed polyacrylamide which are commercially available, for example, nano titanium dioxide is purchased from Sigam-Aldrich, cetyl trimethyl ammonium bromide is purchased from Shanghai Michelin Biochemical technology, Inc., and partially hydrolyzed polyacrylamide is purchased from Shanghai Michelin Biochemical technology, Inc.
In a second aspect, the invention provides a preparation method of the profile control and flooding system, which specifically comprises the following steps:
(1) adding cetyl trimethyl ammonium bromide into water to be dissolved to obtain a cetyl trimethyl ammonium bromide solution;
(2) adding the nano titanium dioxide into a cetyl trimethyl ammonium bromide solution to obtain a mixed solution in which the nano titanium dioxide is uniformly dispersed;
(3) and adding the partially hydrolyzed polyacrylamide into the mixed solution, and uniformly stirring to obtain the profile control and flooding system.
In one embodiment, the preparation method of the profile control and flooding system comprises the following steps:
(1) adding a CTAB surfactant into water at 25 ℃, and stirring by using a magnetic stirrer to fully dissolve the CTAB surfactant to obtain a CTAB aqueous solution;
(2) dropwise adding nano TiO into CTAB aqueous solution2Stirring and then ultrasonic treatment is carried out to enable the nano TiO to be2Uniformly dispersing in water to obtain CTAB and nano TiO2Dispersing the aqueous solution, weighingIs a mixed solution;
(3) adding partial hydrolysis HPAM into the mixed solution, and stirring the solution at low speed for 12 hours by using a mechanical stirrer; thus obtaining the temperature-resistant salt-tolerant foam profile control system suitable for complex oil reservoir conditions.
Preferably, the stirring time in the step (1) and the stirring time in the step (2) are both 3-5 minutes, the ultrasonic time in the step (2) is 30 minutes, and the stirring time in the step (3) is 12 hours.
The inventor of the invention mainly bases on the following inventive concept when designing the profile control and drive system of the invention:
the surfactant can reduce the interfacial tension of oil, water and gas and liquid, has better foaming performance, can generate a foam system under the stratum condition, and the adsorption of the surfactant on an oil-water interface enables oil to be easily washed down from the surface of the stratum, so that the surface of the oleophylic stratum can be inverted into a hydrophilic surface, and the oil washing efficiency is improved; the existence of the polymer improves the fluidity ratio of the surfactant to oil, the thickening of the polymer to an oil displacement medium can reduce the diffusion rate of the surfactant, and the polymer can react with calcium ions, magnesium ions and the like to protect the surfactant; the adsorption of the nano particles on a gas-liquid interface can form a special layered structure, liquid film drainage and gas diffusion can be reduced, the rheological characteristics of the interface can be changed to a large extent by the adsorption of the nano particles, and the stability of a foam system can be enhanced by the increase of the interfacial viscoelasticity of the system. The combination of the surfactant, the polymer and the nano particles can play a role in improving the oil washing efficiency and swept volume.
Based on the above inventive concept, the inventors of the present invention further optimized the components, the characteristics of the components, and the mixture ratio of the components. Specifically, in the profile control system of the invention, after foam is generated, the nano TiO is used2The stable adsorption forms a Janus structure on a gas-liquid interface, the structure can reduce liquid film drainage, gas diffusion and inhibit Oswald ripening, and the HPAM generates flocculation by adsorbing one or more foams, so that on one hand, the surface elasticity of the foams is strengthened, the surface viscosity is improved, on the other hand, the molecules adsorbed on the surfaces of the foams are more closely arranged, and the gas ventilation is reducedAnd meanwhile, the flocculation structure forms a bridge between foams, so that the stability of the foams is greatly improved. When the profile control system enters underground, the movement of the HPAM at high temperature is hindered under the adsorption effect of the HPAM and the steric effect of the surfactant, so that the viscosity reduction is limited, and higher viscosity can be maintained at high temperature. Generally, in high salt water, the HPAM molecular chain is in a curled state due to shielding of the electric property of the carboxyl group, and the thickening ability is lowered, but in the present invention, the nano TiO molecule is used2The charge repulsion with HPAM can promote the form of HPAM to be more extended, improve the viscosity of the profile control system and improve the salt tolerance of HPAM. Nano TiO 22Under the action of charge repulsion with HPAM, the oil is more easily adsorbed on the rock, and the oil is stripped from the rock, thereby playing the role of oil displacement and profile control.
Compared with the traditional binary or ternary combination flooding, the profile control flooding system has the following advantages: the surfactant, the polymer and the nano material used in the system are all industrial products, are cheap and easily available, and have simple preparation process and less time consumption. When the profile control and flooding system is prepared at 25 ℃, a small amount of sediment exists in the system, a large amount of flocculation can be generated under stratum conditions (such as the temperature of 130 ℃ and the mineralization degree of 220000mg/L), a bridge can be formed between foams by the flocculation structure, so that the foam stability is greatly improved, a common binary or ternary flooding system cannot play a good effect in a large crack due to a fracture-cavity oil reservoir under the complex oil reservoir condition, and the viscosity cannot be reduced due to the fact that a large amount of flocculants are formed by the profile control and flooding system under the high-temperature and high-salt conditions, so that the foam system can play a role in displacing oil in the stratum and can play a certain role in profile control due to the existence of flocculation.
In a third aspect, the invention provides the application of the profile control system in oil displacement of oil reservoirs, especially complex oil reservoirs with harsh conditions (the temperature is not lower than 130 ℃, and the mineralization degree is not lower than 220000 mg/L).
In a fourth aspect, the present invention provides a method for displacing oil from an oil reservoir (especially a complex oil reservoir with harsh conditions), comprising: injecting into the formation a main slug comprising the profile control system of the first aspect of the invention.
Specifically, the oil displacement method comprises the following steps:
step 1: injecting a pre-pretreatment slug into the stratum according to the volume injection amount of 0.1-1% of the pore volume of the stratum;
step 2: injecting a main section plug comprising the profile control system and nitrogen of the first aspect of the invention into the stratum according to the volume injection amount of 30-50% of the pore volume of the stratum;
and step 3: injecting a post-positioned protective slug into the stratum according to the volume injection amount of 0.1 to 1 percent of the pore volume of the stratum;
and 4, step 4: and (5) closing the well.
Preferably, in step 1, the pre-pretreatment slug is a cetyltrimethylammonium bromide solution with a concentration of 0.1mmol/L to 0.5 mmol/L.
Preferably, in step 2, the profile control system and nitrogen are alternately injected into the formation at a volume ratio of profile control system to nitrogen of from 1: 1 to 1: 3 (preferably 1: 2).
Preferably, in step 3, the post-protection slug is a nano titania solution with a mass concentration of 1% to 5% (preferably 3%).
In one embodiment, the flooding method of the present invention comprises:
step 1: CTAB aqueous solution with the concentration of 0.1 mmol/L-0.5 mmol/L is used as a pre-pretreatment slug, and the pre-pretreatment slug is injected into the stratum, wherein the volume injection amount is 0.1-1% of the pore volume of the stratum. By pre-treating the slug, the oil saturation can be reduced, the relative permeability difference of an oil-water layer is increased, and the injection of subsequent working fluid is facilitated.
Step 2: the first aspect of the invention adopts a profile control and flooding system and a pure nitrogen system as main slugs, the profile control and flooding system and the pure nitrogen system with the volume ratio of 1: 2 are alternately injected into the stratum, and the volume injection amount of the main slugs is 30-50% of the pore volume of the stratum. Stable foam can be generated by arranging a section plug of a profile control and flooding system, wherein a surfactant CTAB is a foaming agent, and a polymer HPAM and nano TiO are2All are foam stabilizers, HPAM can improve the viscoelasticity of a foam phase, and nano TiO2Can improve the foam interfaceThe viscoelasticity of the oil-based oil.
And step 3: adopts nano TiO with the mass concentration of 3 percent2The water solution is used as a post-protection slug, and the post-protection slug is injected into the stratum, wherein the volume injection amount of the post-protection slug is 0.1-1% of the volume of the pores of the stratum. Through setting up the rearmounted protection slug, can ensure main slug full play effect, prevent that main slug from receiving great pressure differential effect and breaking through in the near wellbore area.
And 4, step 4: closing the well for 5-10 days, opening the well and recovering production.
Nano TiO 22The adsorption at the gas-liquid interface and the flocculation formed under the high-temperature condition can improve the stability of the foam, and the foam can realize the plugging of a high-seepage channel in the stratum, enlarge the swept volume of the subsequent fluid and enhance the fluidity control capability of the composite profile control and flooding system. The addition of the surfactant can reduce the gas-liquid interfacial tension, so that a foam system is formed, the temperature resistance of the HPAM is improved, the oil-water interfacial tension can be reduced, the stripping of residual oil from the surface of a rock stratum is facilitated, and the oil displacement efficiency of the composite profile control and flooding system is improved. Nano TiO 22The HPAM is promoted to be more extended, the reaction rate of the HPAM and calcium and magnesium ions is improved, so that the surfactant is protected, the stability of a foam system can be improved, and the sweep efficiency and the oil washing capacity of the foam are greatly improved.
The system can meet the requirements of field preparation, is convenient and quick, has a simple oil displacement mode, and can improve the oil displacement effect of the system to the maximum extent by arranging a plurality of alternating oil displacement slugs.
Examples
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
Example one
The composition (weight percentage) of the profile control system of the embodiment is as follows: hydrophilic TiO with particle size of 30nm22% of particles, 0.9% of CTAB, 0.1% of HPAM having a molecular weight of 700 ten thousand and a degree of hydrolysis of 10% and the balance of simulated mineralized water having a total degree of mineralization of 220000mg/L (wherein Ca is present in the mineralized water)2+With Mg2+The ion concentration was 2000 mg/L).
The preparation method of the profile control system of the embodiment is as follows:
(1) adding a CTAB surfactant into simulated mineralized water with the total mineralization of 220000mg/L at 25 ℃, and stirring for 3-5 minutes by using a magnetic stirrer to fully dissolve the CTAB surfactant to obtain a CTAB aqueous solution;
(2) adding hydrophilic TiO with the particle size of 30nm into CTAB aqueous solution dropwise2Particles are stirred for 3 to 5 minutes and then are subjected to ultrasonic treatment for 30 minutes to enable the nano TiO to be2Uniformly dispersing in water to obtain CTAB and nano TiO2A dispersed aqueous solution, called a mixed solution;
(3) the partially hydrolyzed HPAM was added to the mixed solution and the solution was stirred at low speed for 12 hours using a mechanical stirrer to obtain the profile control system of this example.
The prepared profile control and flooding system (which is not stirred) is observed at the normal temperature of 25 ℃, namely the normal temperature profile control and flooding system, as shown in figure 1, the profile control and flooding system has less precipitation at the temperature of 25 ℃ and 220000 mg/L.
The prepared profile control system solution is placed in an ampoule bottle, sealed and then placed in a constant-temperature oven at 130 ℃ for aging for 72 hours. As shown in FIG. 2, the flooding system forms a large amount of flocculation after aging at 220000mg/L at 130 ℃ for 72 hours, and the flocculation is not reduced after cooling again.
Respectively stirring a normal-temperature profile control system (without an aging process) and a profile control system aged at 130 ℃ for 72 hours at 10000 r/min for 10 minutes by adopting a Waring-Blender high-speed stirring method, and then respectively standing at the normal temperature of 25 ℃ for 2 hours.
FIG. 3 shows the foam morphology formed after stirring the room temperature profile control system for 10 minutes. FIG. 4 shows the foam morphology formed after 10 minutes of stirring of the profile control system after aging at 130 ℃ for 72 hours.
FIG. 5 shows the foam form of the room temperature profile control system after stirring for 10 minutes and then standing for 2 hours at room temperature. FIG. 6 shows the foam morphology of the profile control system after aging at 130 ℃ for 72 hours, stirring for 10 minutes, and then standing at room temperature for 2 hours.
It can be seen that the aged composite system solution formed a foam with better stability. The aged compound system solution can form more foams after being stirred, the foams are more compact, and the foam defoaming speed is much slower than that of a normal-temperature system.
Example two
The composition (weight percentage) of the profile control system of the embodiment is as follows: hydrophilic TiO with particle size of 30nm21% of particles, 0.5% of CTAB, 0.2% of HPAM having a molecular weight of 700 ten thousand and a degree of hydrolysis of 10% and the balance of simulated mineralized water having a total degree of mineralization of 220000mg/L (wherein Ca is present in the mineralized water)2+With Mg2+The ion concentration was 2000 mg/L).
The preparation method of the profile control system of the embodiment is as follows:
(1) adding a CTAB surfactant into simulated mineralized water with the total mineralization of 220000mg/L at 25 ℃, and stirring for 3-5 minutes by using a magnetic stirrer to fully dissolve the CTAB surfactant to obtain a CTAB aqueous solution;
(2) adding hydrophilic TiO with the particle size of 30nm into CTAB aqueous solution dropwise2Particles are stirred for 3 to 5 minutes and then are subjected to ultrasonic treatment for 30 minutes to enable the nano TiO to be2Uniformly dispersing in water to obtain CTAB and nano TiO2A dispersed aqueous solution, called a mixed solution;
(3) the partially hydrolyzed HPAM was added to the mixed solution and the solution was stirred at low speed for 12 hours using a mechanical stirrer to obtain the profile control system of this example.
EXAMPLE III
The composition (weight percentage) of the profile control system of the embodiment is as follows: hydrophilic TiO with particle size of 10nm23% of particles, 0.2% of CTAB, 0.3% of HPAM having a molecular weight of 1000 ten thousand and a degree of hydrolysis of 15% and the balance of simulated mineralized water having a total degree of mineralization of 220000mg/L (wherein Ca is present in the mineralized water)2+With Mg2+The ion concentration was 2000 mg/L).
The preparation method of the profile control system of this example is the same as that of the first example.
Example four
The composition (weight percentage) of the profile control system of the embodiment is as follows: hydrophilic TiO with particle size of 20nm22% of particles, 0.8% of CTAB, 0.1% of HPAM having a molecular weight of 500 ten thousand and a degree of hydrolysis of 5% and the balance of simulated mineralized water having a total degree of mineralization of 220000mg/L (wherein Ca is present in the mineralized water)2+With Mg2+The ion concentration was 2000 mg/L).
The preparation method of the profile control system of this example is the same as that of the first example.
EXAMPLE five
The composition (weight percentage) of the profile control system of the embodiment is as follows: hydrophilic TiO with particle size of 30nm22% of particles, 0.5% of CTAB, 0.2% of HPAM having a molecular weight of 1200 ten thousand and a degree of hydrolysis of 20% and the balance of simulated mineralized water having a total degree of mineralization of 220000mg/L (wherein Ca is present in the mineralized water)2+With Mg2+The ion concentration was 2000 mg/L).
The preparation method of the profile control system of this example is the same as that of the first example.
Example six: simulated oil displacement experiment
In this embodiment, the oil displacement is performed by using the oil displacement and displacement system prepared in the first embodiment. Aiming at the permeability of 2.3 mu m2Artificial core (length 8.5cm, diameter 2.5cm, pore volume about 13.65 mL). The artificial core was purchased from Zhisheng Petroleum technologies, Inc., of Oriental, Beijing.
The oil displacement method of the embodiment comprises the following steps:
in a constant temperature oven at 130 ℃, the permeability is 2.3 mu m2The artificial rock core (the length is 8.5cm, the diameter is 2.5cm, the pore volume is about 13.65mL), vacuumizing, saturated water and saturated oil are pumped, and after the water content is driven to 96%, oil displacement of a composite profile control and flooding system is carried out according to the following three slugs: the device comprises a front pretreatment slug, a main slug and a rear protection slug. The specific operation of the composite profile control and flooding system for oil displacement is as follows:
(1) pre-pretreatment of a slug: the pre-pretreatment slug is a CTAB aqueous solution, the mass fraction of CTAB in the aqueous solution is 0.3mmol/L, and the volume injection amount is 0.1% of the pore volume of the core;
(2) a main slug: the composite profile control and flooding system in the main slug is the profile control and flooding system prepared in the first embodiment, the profile control and flooding system and pure nitrogen gas pass through a foam generator according to the volume ratio of 1: 2 and are injected into a rock core, and the total volume injection amount is 50% of the pore volume of the rock core;
(3) a rear protection slug: the post-positioned protective slug is nano TiO2Aqueous solution of (2), nano TiO in the aqueous solution2The mass fraction of the core is 3 percent, and the volume injection amount is 1 percent of the pore volume of the core;
after the three steps are completed, the core is aged for 5 days at 130 ℃, and water is driven again until the water content reaches 98%. After the profile control and flooding system prepared in the first embodiment is injected, the pressure in the subsequent water flooding stage is obviously increased, the maximum value of 80kPa is reached after the pore volume is 2 times that of water flooding, and the maximum value of 80kPa is still maintained after the pore volume is 5 times that of water flooding, so that the profile control capability is strong, and the recovery ratio increment is obviously improved by 32.36%.
Example seven: simulated oil displacement experiment
According to the oil displacement method of the sixth embodiment, oil displacement experiments are respectively carried out by adopting the oil displacement and control systems of the second embodiment to the fifth embodiment, and the improvement of the recovery ratio is respectively as follows: 28.31%, 25.45%, 27.63%, 25.12%.
The present invention has been disclosed in the foregoing in terms of preferred embodiments, but it will be understood by those skilled in the art that these embodiments are merely illustrative of the present invention and should not be construed as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to those of the embodiments are intended to be included within the scope of the claims of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined in the claims.

Claims (8)

1. A method for displacing oil from an oil reservoir, comprising:
step 1: injecting a pre-pretreatment slug into the stratum according to the volume injection amount of 0.1-1% of the pore volume of the stratum;
step 2: injecting a main section plug comprising a profile control system and nitrogen into the stratum according to the volume injection amount of 30-50% of the pore volume of the stratum; the profile control and flooding system comprises the following components in percentage by weight: 2% of nano titanium dioxide, 0.9% of hexadecyl trimethyl ammonium bromide, 0.1% of partially hydrolyzed polyacrylamide and the balance of water; the average grain diameter of the nano titanium dioxide is 30 nm; the molecular weight of the partially hydrolyzed polyacrylamide is 700 ten thousand, and the degree of hydrolysis is 10%;
and step 3: injecting a post-positioned protective slug into the stratum according to the volume injection amount of 0.1 to 1 percent of the pore volume of the stratum;
and 4, step 4: and (5) closing the well.
2. The oil displacement method of claim 1, wherein in step 2, the water is simulated mineralized water with a total mineralization of 220000Mg/L and ion concentrations of both Ca2+ and Mg2+ of 2000 Mg/L.
3. The oil displacement method of claim 1 or 2, wherein in the step 2, the preparation method of the profile control and flooding system comprises the following steps:
(1) adding cetyl trimethyl ammonium bromide into water to be dissolved to obtain a cetyl trimethyl ammonium bromide solution;
(2) adding nano titanium dioxide into the cetyl trimethyl ammonium bromide solution to obtain a mixed solution in which the nano titanium dioxide is uniformly dispersed;
(3) and adding the partially hydrolyzed polyacrylamide into the mixed solution, and uniformly stirring to obtain the profile control and flooding system.
4. The oil displacement method of claim 1, wherein in step 1, the pre-pretreatment slug is a cetyl trimethyl ammonium bromide solution with a concentration of 0.1mmol/L to 0.5 mmol/L.
5. The oil displacement method according to claim 1, wherein in the step 2, the profile control system and the nitrogen are alternately injected into the stratum according to the volume ratio of the profile control system to the nitrogen being 1: 1 to 1: 3.
6. The method of claim 5, wherein in step 2, the profile control system and the nitrogen are alternately injected into the stratum according to the volume ratio of the profile control system to the nitrogen being 1: 2.
7. The oil displacement method according to claim 1, wherein in the step 3, the post-protection plug is a nano titanium dioxide solution with a mass concentration of 1-5%.
8. The oil displacement method of claim 7, wherein in step 3, the post-protection plug is a nano titanium dioxide solution with a mass concentration of 3%.
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