Tight oil reservoir CO.SUB.2 .flooding multi-scale channeling control system and preparation method

Abstract

A tight oil reservoir CO.sub.2 flooding multi-scale channeling control system and a preparation method, including nanoscale CO.sub.2 responsive worm-like micellar systems and micron-scale CO.sub.2 responsive dispersion gel, are provided. The nanoscale CO.sub.2 responsive worm-like micelle system is prepared by CO.sub.2 reactive monomers and organic anti-ion monomers stirred in water. The micron-scale CO.sub.2 responsive dispersion gel is made of acrylamide, a responsive monomer, a silane coupling agent modified hydroxylated multi-walled carbon nanotubes as raw materials, cross-linked in water. The tight oil reservoir CO.sub.2 multi-scale channel control system, has strong flow control ability during CO.sub.2 displacement, and high-strength carbon nanotubes are introduced into the micro-scale CO.sub.2 responsive dispersion gel, which effectively improves the strength and long-term stability of the dispersion gel, significantly enhances the sealing effect on cracks, and after displacement of the CO.sub.2 of the system, the worm-like micelles revert to spherical micelles with good responsive reversibility.

Claims

1. A tight oil reservoir CO.sub.2 flooding multi-scale channeling control system, comprising nanoscale CO.sub.2 responsive worm-like micelle system and micron-scale CO.sub.2 responsive dispersion gel; wherein, in mass percent, the micron-scale CO.sub.2 responsive dispersion gel are prepared by cross-linking the following components: acrylamide 15%-25%; responsive monomer 3%-8%; silane coupling agent modified hydroxylated multi-walled carbon nanotubes 0.05%-0.1%; initiator 0.01%-0.1% of total monomer mass; cross-linking agent 0.5%-2% of the total monomer mass; and water, wherein the total mass percent of the components is 100%; the preparation method of the micron-scale CO.sub.2 responsive dispersion gel is: after the silane coupling agent modified hydroxylated multi-walled carbon nanotubes are dispersed uniformly in water by ultrasonic waves, under the condition of stirring speed of 300-500 r/min, the acrylamide, responsive monomer, initiator and cross-linking agent are respectively added to the solution; N.sub.2 is injected into the solution until the solution becomes viscous, and a thermometer is used to monitor the temperature change of the solution, until the temperature of the solution rises to a highest temperature when cooling down starts, the solution is kept in thermal insulation for 2-4 hours under the condition of the highest temperature of the solution to obtain a black gel; micron-scale CO.sub.2 responsive dispersion gel is obtained after granulation, drying and pulverization of the black gel; wherein, the responsive monomer is N-methyl-N-vinylformamide, N,N-diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, or a combination thereof; wherein, the nanoscale CO.sub.2 responsive worm-like micelle system is prepared by cross-linking the following components: CO.sub.2 responsive monomer 30-90 mmol/L; organic counter ion monomer 30-90 mmol/L; and a solvent comprising water; the preparation method of the nanoscale CO.sub.2 responsive worm-like micelle system is: CO.sub.2 responsive monomer is completely dissolved in water to formulate CO.sub.2 responsive monomer solution, under the condition of stirring speed of 300-500 r/min, the organic counter ion monomer is added with the same amount of the CO.sub.2 responsive monomer to the CO.sub.2 responsive monomer solution, and the solution is stirred at room temperature to obtain uniform nano-scale CO.sub.2 responsive worm-like micelle system; wherein the CO.sub.2 responsive monomer is N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, N,N-dimethylbutylamine, tetramethylethylenediamine, trimethylamine, N,N-dimethyloleoaminde-propylamine, diethylenetriamine, cocoyl dimethyl tertiary amine, erucic acid amidopropyl dimethyl tertiary amine, or a combination thereof the organic counter ion monomer is sodium p-styrenesulfonate, sodium dodecylbenzenesulfonate, sodium p-toluenesulfonate, sodium oleate, or a combination thereof.

2. The tight oil reservoir CO.sub.2 flooding multi-scale channeling control system as claimed in claim 1, wherein the silane coupling agent modified hydroxylated multi-walled carbon nanotubes is γ-methacryloyloxypropyltrimethoxy silane, vinyl tri(β-methoxyethoxy) silane, vinyl triethoxy silane, or a combination thereof.

3. The tight oil reservoir CO.sub.2 flooding multi-scale channeling control system as claimed in claim 1, wherein the initiator is composed of ammonium persulfate, ammonium hydrogen sulfite and azobisisobutyramidine hydrochloride in a weight ratio of 1:1:2.

4. The tight oil reservoir CO.sub.2 flooding multi-scale channeling control system as claimed in claim 1, wherein the cross-linking agent is N,N-methylenebisacrylamide, phenolic crosslinking agent, polyethyleneimine, or a combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to more clearly illustrate the technical solution of the present invention, the drawings described in the embodiment will be briefly described below, and it should be understood that the following drawings are only shown in some embodiments of the present invention, so it should be seen as a defined scope, and will be obtained in accordance with these figures, without paying creative labor, in terms of ordinary skill in the art.

(2) FIG. 1 shows CO.sub.2 responsive performance evaluation result graph of the tight oil reservoirs CO.sub.2 responsive multi-scale channeling control system;

(3) FIG. 2 shows a microscopic topography of the tight oil reservoirs CO.sub.2 responsive multi-scale channeling control system;

(4) FIG. 3 shows a test chart of anti-channeling performance of the tight oil reservoirs CO.sub.2 responsive multi-scale channeling control system during CO.sub.2 displacement.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) The present invention will be further described in detail below with reference to the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

(6) 1) Preparation of Nanoscale CO.sub.2 Responsive Worm-Like Micellar Systems

(7) Dissolve N,N-dimethyl oleoaminde-propylamine in deionized water, prepare 200 mL of N,N-dimethyloleic acid amidopropyl tertiary amine solution with a concentration of 90 mmol/L. Add 18 mmol sodium p-styrene sulfonate to the above solution under the condition of stirring at a stirring speed of 300 r/min, and stop stirring after the solution is uniform to obtain nano-scale CO.sub.2 responsive worm-like micelle system.

(8) 2) Micron CO.sub.2 Preparation of Responsive Dispersion Gel

(9) 0.1 g of γ-methacryloyloxypropyl trimethoxysilane modified hydroxylated multi-walled carbon nanotubes were uniformly dispersed in 75 mL of deionized water under ultrasonic conditions, and then under the condition of stirring at a stirring speed of 300 r/min, 20 g of acrylamide, 5 g N,N-diethylaminoethyl methacrylate, 0.5 mL ammonium persulfate (concentration 1 wt %), 0.5 mL sodium bisulfite (concentration 1 wt %) and 1 mL azobisisobutyramidine hydrochloride (concentration 1 wt %) %) and 1 mL of phenolic cross-linking agent were added to the solution. The solution is then introduced with N.sub.2 until the solution becomes viscous and use a thermometer to monitor the temperature of the solution. When the temperature of the solution rises to the highest point and starts to cool down, keep the temperature for 2 hours to obtain a black monomer gel; the monomer gel is granulated, dried, pulverized to get micron CO.sub.2 responsive dispersion gel.

(10) It is worth noting that the method for modifying carbon nanotubes by using a silane coupling agent to prepare the above-mentioned silane-modified carbon nanotubes is a prior art in the art, and will not be repeated here.

(11) 3) Preparation of CO.sub.2 Responsive Multiscale Channeling Control Systems.

(12) 0.8 g micron-scale CO.sub.2 responsive dispersion gel obtained above was added to the aforementioned 200 mL of 90 mmol/L nano-scale CO.sub.2 responsive worm-like micelle system, fully stirred until the dispersion gel is uniformly suspended and dispersed in the micelle system, that is, the tight oil reservoir CO.sub.2 responsive multi-scale channeling control system.

Example 2

(13) 1) Preparation of Nanoscale CO.sub.2 Responsive Worm-Like Micellar Systems

(14) Dissolve N,N-dimethyl oleoaminde-propylamine in deionized water, prepare 200 mL of N,N-dimethyloleic acid amidopropyl tertiary amine solution with a concentration of 70 mmol/L, and under a condition of stirring at a stirring speed of 500 r/min, add 14 mmol sodium oleate is added to the above solution, and stop stirring after the solution is uniform to obtain nano-scale CO.sub.2 responsive worm-like micelle system.

(15) 2) Preparation of Micron CO.sub.2 Responsive Dispersion Gel

(16) 0.07 g of γ-methacryloyloxypropyl trimethoxysilane modified hydroxylated multi-walled carbon nanotubes are uniformly dispersed in 70 mL of deionized water under ultrasonic conditions, and then under a condition of stirring at a stirring speed of 500 r/min, 20 g of acrylamide, 8 g N,N-diethylaminoethyl methacrylate, 0.6 mL ammonium persulfate (concentration 1 wt %), 0.6 mL sodium bisulfite (concentration 1 wt %) and 1.2 mL azobisisobutyramidine hydrochloride (concentration 1 wt %) and 0.2 g N,N-methylenebisacrylamide are added to the solution. The solution is then introduced with N.sub.2 until the solution becomes viscous and use a thermometer to monitor the temperature of the solution. When the temperature of the solution rises to the highest point and starts to cool down, keep the temperature for 2 hours to obtain a black monomer gel; the monomer gel is granulated, dried, pulverized to get micron CO.sub.2 responsive dispersion gel.

(17) 3) Preparation of CO.sub.2 Responsive Multiscale Channeling Control System

(18) 1.0 g micron-scale CO.sub.2 responsive dispersion gel obtained above is added to the aforementioned 200 mL of 70 mmol/L nanoscale CO.sub.2 responsive worm-like micelle system, fully stirred until the dispersion gel is uniformly suspended and dispersed in the micelle system, that is, obtaining the tight oil reservoir CO.sub.2 responsive multi-scale channeling control system.

(19) 1. CO.sub.2 Responsive Evaluation of the Tight Oil Reservoirs CO.sub.2 Responsive Multi-Scale Channeling Control System

(20) Under stirring condition at a rate of 100 mL/min, CO.sub.2 is injected into the tight oil reservoir CO.sub.2 responsive multi-scale channeling control system prepared in Example 1. After 60 min, the viscosity of the system at 30° C. was measured by Brookfield DV-III viscometer (shear rate 7.34s.sup.-1); then inject N.sub.2 into the system under the same conditions, repeat the above steps three times, observe the CO.sub.2 of the system responsiveness and reversibility, the experimental results are as follows FIG. 1 shown.

(21) It can be seen that after the system contacts CO.sub.2, the viscosity increased from 10.4 mPa.Math.s to 2339 mPa.Math.s. When the CO.sub.2 in the system is replaced by N.sub.2, the viscosity of the system was reduced to 10.4 mPa.Math.s. After 3 cycles, the highest viscosity of the system remained at 2339 mPa.Math.s, and the lowest viscosity remained at 10 mPa.Math.s, showing good CO.sub.2 responsiveness and reversibility.

(22) 2. Micromorphology of Tight Oil Reservoirs CO.sub.2 Responsive Multiscale Channeling Control System

(23) Under stirring conditions at a rate of 100 mL/min, CO.sub.2 is injected into the tight oil reservoir CO.sub.2 responsive multi-scale channeling control system prepared in Example 2, after 60 min, stop the introduction of CO.sub.2, the micro-morphology of the system was observed by environmental scanning electron microscope, and the results are as FIG. 2 shown. The three-dimensional network structure can be clearly observed in the system, which is the basic structure of worm-like micelles. In addition, supramolecular aggregates formed by worm-like micelles and particle side chains can be observed on the surface of the disperse gel. The dispersion gel and worm-like micelles are formed as a whole through supramolecular aggregates, which can effectively increase the anti-channeling properties of the system, ensuring that the channeling control effect of the entire channeling control system.

(24) 3. Evaluation of Anti-Channeling Performance

(25) To verify the effect of the present invention proposed CO.sub.2 responsive multi-scale channeling control system in tight oil reservoir CO.sub.2 flooding, the development of CO.sub.2 oil displacement experiment, using the CO.sub.2 responsive multi-scale channeling control system prepared in Example 2. Fractured rock slabs were used to carry out the displacement experiments. The rock slab parameters are 10 cm in length and width, 1 cm in height, and 0.2 mm in crack width. With “CO.sub.2 flooding-injection system-CO.sub.2 flooding-injection system-CO.sub.2 flooding-injection system-CO.sub.2 flooding” step, keeping the injection volume of each system at 0.25 PV, the final measurement results are as follows FIG. 3 shown. See FIG. 3, It can be seen that when CO.sub.2 is first injected, the injected CO.sub.2 channeling occurs along the fracture, and no crude oil is recovery at this time; when the system is injected in an alternate way, the system and CO.sub.2 full contact, the viscosity of the system increases, a higher pressure gradient is established, and the injected CO.sub.2 turning to enter the matrix, expanding the swept volume, when the pressure difference reaches about 0.2 MPa, the final recovery factor is increased by about 23%, and it has good channeling control potential.

(26) The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Changes or substitutions should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.