CN112279962A

CN112279962A - Terpolymer used as thick oil displacement agent and preparation method thereof

Info

Publication number: CN112279962A
Application number: CN201910677165.5A
Authority: CN
Inventors: 陈瞰瞰; 路熙; 龙秋莲
Original assignee: China Petroleum and Chemical Corp; Sinopec Exploration and Production Research Institute
Current assignee: China Petroleum and Chemical Corp; Sinopec Exploration and Production Research Institute
Priority date: 2019-07-25
Filing date: 2019-07-25
Publication date: 2021-01-29

Abstract

The invention provides a terpolymer used as a thick oil displacement agent and a preparation method thereof. The terpolymer has the following structural formula:

wherein n is₁Is 100 to 180, n₂Is 5 to 10, n₃Is 70 to 80, n₄From 90 to 110, the number average molecular weight of the terpolymer being from 4459500 to 7733000.

Description

Terpolymer used as thick oil displacement agent and preparation method thereof

Technical Field

The invention provides a terpolymer and a preparation method thereof, and particularly provides a terpolymer capable of being used as a thick oil displacement agent.

Background

The oil field exploitation process in China is divided into multiple exploitation, and the exploitation rate is gradually reduced along with the increase of exploitation times. At present, main oil fields all enter the later stage of exploitation, so that in order to improve the recovery ratio of the existing oil fields, the oil recovery technology is more and more concerned, and the research and development of oil displacement agents used in the exploitation process are also increasingly concerned by various large oil companies and researchers.

Chemical flooding is a main method in oil extraction technology, common oil displacement agents are mostly used for thin oil at present, and an oil displacement system applied to thick oil is relatively few. However, displacement is the most efficient way to develop, in view of the problem of high viscosity and difficult flow of the heavy oil itself. Compared with an oil displacement agent used for thin oil, a thick oil displacement system is mainly based on polymers. By manually injecting water-soluble high-molecular-weight polymer, the viscosity of the water phase is increased, the permeability of the water phase is reduced, the oil-water viscosity ratio is improved, and the purpose of improving the recovery ratio is achieved. However, in view of complex reservoir conditions, the existing polymer oil displacement agent has several problems to be solved in the adaptive application process: 1. easy to hydrolyze at high temperature; 2. shearing the easy-to-break chain; 3. the flocculation is easy when meeting calcium and magnesium ions. The above problems are liable to cause a decrease in the viscosity of the polymer solution in a manner of a breakring, thereby losing the effect of water-phase thickening.

Therefore, the thick oil displacement agent can be effectively realized by developing a temperature-resistant, shear-resistant and salt-resistant polymer.

Disclosure of Invention

One of the present invention provides a terpolymer having the following structural formula:

In one embodiment, the number average molecular weight distribution index of the terpolymer is from 1.05 to 1.1.

In one embodiment, the molar content of N, N-dimethylacrylamide monomer in the terpolymer is 57% to 66%, the molar content of 2-acrylamido-2-methylpropanesulfonic acid monomer in the terpolymer is 30% to 40%, and the molar content of N, N-methylenebisacrylamide in the terpolymer is 3% to 4%.

In one embodiment, the ratio of the weight average molecular weight Mw to the peak top molecular weight Mp, Mw/Mp, is from 0.9 to 1.0.

The second aspect of the invention provides a process for the preparation of a terpolymer according to any of the first aspects of the invention, comprising the steps of:

1) dissolving a first monomer and a second monomer in water to obtain a monomer aqueous solution; wherein the first monomer is N, N-dimethylacrylamide and the second monomer is 2-acrylamide-2-methylpropanesulfonic acid;

2) adding N, N-methylene bisacrylamide to the monomer aqueous solution to obtain an aqueous solution of a crosslinked copolymer;

3) and adding an initiator and a catalyst into the crosslinking aqueous solution, and reacting to obtain a gel product containing the terpolymer.

In a specific embodiment, the mass ratio of the first monomer to the second monomer is from 4:1 to 9: 1.

In one embodiment, the amount of the N, N-methylenebisacrylamide is 0.1% to 0.3% by mass based on 100% by mass of the sum of the first monomer and the second monomer.

In one embodiment, the amount of the initiator is 0.1% to 0.5% based on 100% of the sum of the mass of the first monomer and the mass of the second monomer.

In one embodiment, the catalyst is used in an amount of 0.1% to 0.3% based on 100% of the sum of the mass of the first monomer and the mass of the second monomer.

In one embodiment, the initiator is azobisisobutylamidine hydrochloride.

In one embodiment, the catalyst is at least one of dimethylethylenediamine, copper chloride, and tetramethylethylenediamine.

In one embodiment, in step 1), the pH of the aqueous monomer solution is adjusted to a value of 7 to 14.

In one embodiment, the initiator and the catalyst are added to the aqueous crosslinking solution after passing nitrogen through the aqueous crosslinking solution for 20 to 40 minutes. For example, the nitrogen gas is introduced for 30 minutes.

In one embodiment, in step 3), after the initiator and the catalyst are added to the crosslinking aqueous solution, the reaction is stirred until stirring is impossible, and then the reaction is continued for 14 to 20 hours. The reaction is continued for, for example, 16 hours.

In one embodiment, the method further comprises step 4) of cutting the gel product into pieces, and then drying and granulating the pieces.

In one embodiment, in step 4), the drying is carried out at 55 to 65 ℃ for 2 to 4 hours. For example, oven-dried at 60 ℃ for 3 hours.

The third invention provides the application of the terpolymer disclosed in any one of the first invention or the terpolymer prepared by the method disclosed in any one of the second invention in being used as a thick oil displacement agent.

The invention has the beneficial effects that:

the terpolymer disclosed by the invention has very good viscoelasticity and water solubility, is not easy to break in shearing and hydrolyze, can be used as a thick oil displacement agent, has a wider swept area compared with a common displacement agent, and reduces the finger advance phenomenon. For example, the method can be suitable for the oil displacement of heavy oil reservoirs under the conditions of high temperature, high shear, high calcium and magnesium and the like. For example, it can be used in a thick oil having a viscosity of 100 to 3000 mPas at 80 ℃. In the system, the dosage is 0.1 to 0.3 percent, and Ca²⁺When the ion concentration is 100000mg/L, the yield can be improved by 20% compared with water drive indoors.

In addition, the method for preparing the terpolymer is simple in process and high in yield.

Drawings

FIG. 1 shows the molecular weight of the terpolymer DTAM-MBAM-AMPS of example 8, as measured by gel chromatography (GPC). The molecular weight of the terpolymer in a GPC spectrogram is mainly single high peak, the half-peak width is about 1.8, which shows that the copolymerization degree is higher, the terpolymer is basically in a single polymerization state, the maximum molecular weight is about 700 ten thousand, and the average molecular weight is about 340 ten thousand.

Fig. 2 shows the results of a sand pipe displacement experiment. For thick oil with viscosity of 2860 mPas at 80 ℃, Ca²⁺The concentration is 100000mg/L, the dosage of the terpolymer is 0.1 to 0.3 percent, and the indoor recovery ratio is improved by 20.8 percent compared with that of water drive.

Detailed Description

The present invention is further illustrated by the following examples, which are intended to be purely exemplary of the invention and are not to be construed as limiting the invention in any way.

Unless otherwise specified, the reagents used in the following examples are commercially available.

DTAM: n, N-dimethylacrylamide, its molecular formula is as follows:

AMPS: 2-acrylamido-2-methylpropanesulfonic acid having the formula:

MBAM: n, N-methylene bisacrylamide, its molecular formula is as follows:

AIBA: azobisisobutylamidine hydrochloride

DEMED: dimethylethylenediamine

The molecular formula of the ternary polymer DTAM-MBAM-AMPS is as follows:

example 1

To a 1500mL three necked round bottom flask equipped with a magneton, thermometer, nitrogen recycle, 500g of deionized water was added. Under stirring, 80g of monomeric DTAM and subsequently 20g of monomeric AMPS were added, the pH was adjusted to 7 and subsequently 0.1g of intramolecular cross-linking agent MBAM was added, and nitrogen was continuously introduced at 25 ℃ for 30 min. Then 0.1g of initiator AIBA and 0.1g of catalyst DEED were added in succession. Stirring at 25 deg.C until the liquid phase in the bottle becomes viscous magneton and can not rotate, stopping stirring, and allowing the bottle to react in gel state for 16 h. Subsequently, the gel was chopped, dried at 60 ℃ and granulated, yielding 80.1%.

Wherein the yield is mass of gel after cutting and drying/total mass of monomers × 100%.

Examples 2 to 10

The experimental procedure of example 1 was followed to carry out the orthogonal synthesis experiments of examples 2 to 10.

In example 2, nitrogen was introduced at 20 ℃ for 40 minutes, the reaction temperature was 20 ℃, the drying temperature was 65 ℃ and the drying time was 2 hours, and the other set parameters are shown in table 1.

In example 3, nitrogen was introduced at 30 ℃ for 20 minutes, the reaction temperature was 30 ℃, the drying temperature was 55 ℃ and the drying time was 4 hours, and the other set-up parameters are shown in Table 1.

In examples 3 to 10, the setting parameters are shown in Table 1.

The rest is the same as example 1.

TABLE 1

Examples	DTAM/g	AMPS/g	MBAM/g	AIBA/g	DEMED/g	pH	R.T/h	Yield/%
									2	80	20	0.1	0.1	0.1	14	20	81.6
3	80	20	0.1	0.2	0.1	14	14	82.9
									4	80	20	0.1	0.4	0.1	14	16	88.4
5	80	20	0.1	0.5	0.1	14	16	88.8
									6	80	20	0.1	0.5	0.2	14	16	90.1
7	80	20	0.1	0.5	0.3	14	16	90.8
									8	80	20	0.3	0.5	0.3	14	16	90.8
9	90	10	0.1	0.5	0.3	14	16	85.2
									10	90	10	0.3	0.5	0.3	14	16	86.5

According to examples 1 and 2, it is found that an increase in pH is advantageous for an increase in reaction yield; examples 2 to 5 show that the increase of the amount of the initiator AIBA can effectively improve the product yield, but when the amount is increased to 0.5 percent of the mass ratio of the monomers, the yield increase tends to be stable; examples 5 to 7 show that the increase in the amount of the catalyst DEMED further increases the product yield, but the increase in the yield is maximized when the amount is 0.3% by mass of the monomer. The DTAM monomer ratio is increased, which leads to the reduction of the product yield, but the amount of the MBAM intramolecular cross-linking agent has no influence on the yield. By contrast, the MBAM monomer was used in a relatively smaller amount, and therefore, the cost performance was higher, and example 7 was the optimal synthesis method.

Example 12

Evaluation of oil displacing Performance on the terpolymer synthesized in example 8

Experiment temperature: 80 ℃.

Core for experiment: the natural oil sand epoxy resin cemented rock core of quartz sand has the appearance size of phi 2.5cm multiplied by 30cm and the gas permeability of 2200 multiplied by 10^-3μm²Left and right.

Crude oil: the viscosity of the degassed thick oil in the Shengli oil field is 2860 mPa.s at 80 ℃.

Preparing the concentration of an aqueous solution: the mass concentration is 0.3 percent.

Displacing and preparing liquid water: adding CaCl into Milli-Q water₂Adjusted to Ca²⁺The concentration was 100000 mg/L.

Water drive experiment: and (4) displacing at the speed of 0.3mL/min, recording the pressure and the volume of the produced liquid in the process, stopping injecting when the water content is 98%, and finishing water flooding. The results are shown in FIG. 2.

Polymer flooding experiment: injecting 1.5PV polymer solution at the speed of 0.3mL/min, then switching to the subsequent water flooding, ending the oil displacement experiment when the water content is 98%, and recording the pressure and the volume of the produced liquid at each stage.

While the invention has been described with reference to specific embodiments, those skilled in the art will appreciate that various changes can be made without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, and method to the essential scope and spirit of the present invention. All such modifications are intended to be included within the scope of the present invention as defined in the appended claims.

Claims

1. A terpolymer having the formula:

wherein n is₁Is 100 to 180, n₂Is 5 to 10, n₃Is 70 to 80、n₄From 90 to 110, the number average molecular weight of the terpolymer being from 4459500 to 7733000.

2. The terpolymer of claim 1 having a number average molecular weight distribution index of 1.05 to 1.1.

3. The terpolymer according to claim 1 or 2, characterized in that the molar content of N, N-dimethylacrylamide monomer in the terpolymer is 57% to 66%, the molar content of 2-acrylamido-2-methylpropanesulfonic acid monomer in the terpolymer is 30% to 40%, and the molar content of N, N-methylenebisacrylamide in the terpolymer is 3% to 4%.

4. The terpolymer according to any of claims 1-3, characterized in that the ratio of weight average molecular weight Mw to peak top molecular weight Mp, Mw/Mp, is from 0.9 to 1.0.

5. A process for preparing the terpolymer according to any of claims 1 to 4, comprising the steps of:

6. The method of claim 5, wherein the mass ratio of the first monomer to the second monomer is from 4:1 to 9: 1;

preferably, the amount of the N, N-methylene-bisacrylamide is 0.1% to 0.3% based on 100% of the sum of the mass of the first monomer and the mass of the second monomer;

preferably, the amount of the initiator is 0.1 to 0.5 percent based on 100 percent of the sum of the mass of the first monomer and the mass of the second monomer;

preferably, the catalyst is used in an amount of 0.1% to 0.3% by mass based on 100% by mass of the sum of the first monomer and the second monomer.

7. The method of claim 5 or 6, wherein the initiator is azobisisobutylamidine hydrochloride;

and/or

The catalyst is at least one of dimethyl ethylenediamine, copper chloride and tetramethyl ethylenediamine.

8. The process according to any one of claims 5 to 7, characterized in that in step 1) the pH of the aqueous monomer solution is adjusted to a value of 7 to 14.

9. The method according to any one of claims 5 to 8, characterized in that the initiator and the catalyst are added to the aqueous crosslinking solution after passing nitrogen gas through it for 20 to 40 minutes;

preferably, in step 3), after adding the initiator and the catalyst into the crosslinking aqueous solution, stirring and reacting until stirring is impossible, and then continuing to react for 14 to 20 hours;

preferably, the method further comprises a step 4) of shearing the gel product, and then drying and granulating; drying is preferably carried out at 55 to 65 ℃ for 2 to 4 hours.

10. Use of the terpolymer according to any one of claims 1 to 4 or prepared according to the process of any one of claims 5 to 9 as an oil displacement agent for heavy oils.