Method for in-depth profile control and displacement of low-permeability oil reservoirs

Abstract

The present invention provides a method for in-depth profile control and displacement of low-permeability oil reservoirs, comprising: sequentially injecting a flexible and elastic particle-containing pre-slug, a polymer microsphere-containing main slug and a flexible and elastic particle-containing protective slug into an oil layer, and the three slugs have a volume ratio of total injection amount of 1-2:6-8:1-2. The invention provides a method for in-depth profile control and displacement by using styrene-based flexible and elastic particles in combination with the polyacrylamide polymer microsphere, wherein the flexible elastic particles can block cracks and large pore channels of the oil layer, and the polymer microsphere can displace the remaining oil in the oil layer. In the present invention, different slugs of profile control and displacement system are combined to achieve the objective of blocking cracks and large pore channels, displacing crude oil, and improving oil well recovery.

Claims

1. A method for in-depth profile control and displacement of low-permeability oil reservoirs, wherein the method comprises: sequentially injecting: (a) a flexible and elastic particle-containing pre-slug, (b) a polymer microsphere-containing main slug comprising 0.25%-5% of a polymer microsphere and 95%-99.75% of water, based on 100% of the total weight of the polymer microsphere-containing main slug, and (c) a flexible and elastic particle-containing protective slug into an oil layer, wherein each of the flexible and elastic particle-containing pre-slug, the polymer microsphere-containing main slug and the flexible and elastic particle-containing protective slug has a respective total injection amount, and a volume ratio between the respective total injection amount of each slug is 1-2:6-8:1-2; wherein the polymer microsphere of the polymer microsphere-containing main slug is synthesized by reacting 18%-25% of co-monomers, 0.2%-0.3% of a crosslinker, 0.1%-0.2% of an initiator, 7.5%-8.5% of a dispersant, 40%-45% of an external phase, and balance of water as an internal phase by inverse emulsion polymerization, based on 100% of the total weight of raw materials used, and wherein the co-monomer is one or more of 2-acrylamide-2-methylpropanesulfonic acid and acrylamide; the crosslinker is N,N-methylenebisacrylamide; the initiator is ammonium persulfate; the dispersant is one or more of Span 60 and Tween 60; and the external phase is a white oil.

2. The method for in-depth profile control and displacement of low-permeability oil reservoirs according to claim 1, wherein each of a daily injection amount of the flexible and elastic particle-containing pre-slug and a daily injection amount of the flexible and elastic particle-containing protective slug is 1.5-2.5 times by volume of a daily water injection amount of a target well for profile control and displacement, respectively.

3. The method for in-depth profile control and displacement of low-permeability oil reservoirs according to claim 1, wherein a daily injection amount of the polymer microsphere-containing main slug is 1.0-1.5 times by volume of a daily water injection amount of a target well for profile control and displacement.

4. The method for in-depth profile control and displacement of low-permeability oil reservoirs according to claim 1, wherein the cumulative total injection amount of the flexible and elastic particle-containing pre-slug, the polymer microsphere-containing main slug and the flexible and elastic particle-containing protective slug is 0.1-0.3 times by volume of the controlled pore volume in the oil layer of the target well for profile control and displacement.

5. The method for in-depth profile control and displacement of low-permeability oil reservoirs according to claim 1, wherein the flexible and elastic particle-containing pre-slug, the polymer microsphere-containing main slug and the flexible and elastic particle-containing protective slug have a volume ratio of total injection amount of 1:8:1.

6. The method for in-depth profile control and displacement of low-permeability oil reservoirs according to claim 1, wherein the flexible and elastic particle-containing pre-slug comprises 0.2%-0.3% of the flexible and elastic particles, 0.05%-0.1% of polyacrylamide and balance of water, based on 100% of the total weight of the flexible and elastic particle-containing pre-slug.

7. The method for in-depth profile control and displacement of low-permeability oil reservoirs according to claim 6, wherein the flexible and elastic particles are produced by polymerizing 49.85%-49.95% of styrene and 49.85%-49.95% of butadiene as main agents, with 0.1%-0.3% of benzoyl peroxide as an initiator, based on 100% of the total weight of raw materials used, to obtain a colloid, and then pelleting the colloid, wherein the polymerization is carried out at 80-85 C. for 70-100 mins.

8. The method for in-depth profile control and displacement of low-permeability oil reservoirs according to claim 7, wherein the flexible and elastic particles in the flexible and elastic particle-containing pre-slug have a particle size of 3-6 mm and an elongation at break of 1000%-1300%.

9. The method for in-depth profile control and displacement of low-permeability oil reservoirs according to claim 1, wherein the flexible and elastic particle-containing protective slug comprises 0.3%-0.4% of the flexible and elastic particles, 0.1%-0.15% of polyacrylamide and balance of water, based on 100% of the total weight of the flexible and elastic particle-containing protective slug.

10. The method for in-depth profile control and displacement of low-permeability oil reservoirs according to claim 9, wherein the flexible and elastic particles are produced by polymerizing 49.85%-49.95% of styrene and 49.85%-49.95% of butadiene as main agents, with 0.1%-0.3% of benzoyl peroxide as an initiator, based on 100% of the total weight of raw materials used, to obtain a colloid, and then pelleting the colloid, wherein the polymerization is carried out at 80-85 C. for 70-100 mins.

11. The method for in-depth profile control and displacement of low-permeability oil reservoirs according to claim 10, wherein the flexible and elastic particles in the flexible and elastic particle-containing protective slug have a particle size of 3-6 mm and an elongation at break of 1000%-1300%.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(1) In order to clearly understand the technical features, objects, and advantages of the present invention, the technical solutions of the present invention are described in detail below with reference to the following specific examples, which, however, are not to be construed as limiting the scope of the invention.

Example 1

(2) This example provides a polymer microsphere synthesized by reacting 9% of 2-acrylamide-2-methylpropanesulfonic acid and 16% of acrylamide as comonomers, 0.3% of N,N-methylenebisacrylamide as a crosslinker, 0.2% of ammonium persulfate as an initiator, 5.5% of Span 60 and 3.0% of Tween 60 as a dispersant, 45% of white oil as an external phase and balance of water as an internal phase by inverse emulsion polymerization, based on 100% of the total weight of raw materials used, wherein the polymerization temperature is 90 C. and the polymerization time is 20 mins. The polymer microsphere produced in this example has an initial particle size of 20 m and a hydration swelling rate of 15 folds.

Example 2

(3) This example provides a polymer microsphere-containing main slug comprising 3% of the polymer microsphere produced in Example 1 and 97% of water, based on 100% of the total weight of the polymer microsphere-containing main slug.

Example 3

(4) This example provides a method for in-depth profile control and displacement of low-permeability oil reservoirs, comprising the following steps:

(5) the total injection amount is designed to be 0.1 PV, i.e. 5000 m.sup.3, in a case that the daily water injection amount of the target well for profile control and displacement is 20 m.sup.3, and the controlled pore volume is 50000 m; a flexible and elastic particle-containing pre-slug, the polymer microsphere-containing main slug produced in Example 2 and a flexible and elastic particle-containing protective slug are sequentially injected into the oil layer through the water injection well with daily injection amounts of each slug of 30 m.sup.3, 20 m.sup.3 and 50 m.sup.3 respectively, and total injection amounts of each slug of 500 m.sup.3, 4000 m.sup.3 and 500 m.sup.3 respectively;

(6) wherein the flexible and elastic particle-containing pre-slug comprises the following components: 0.25% of flexible and elastic particles, 0.75% of polyacrylamide (having a molecular weight of 10 million, a hydrolysis degree of 20%) and balance of water, by mass ratio;

(7) the flexible and elastic particle-containing protective slug comprises the following components: 0.35% of flexible and elastic particles, 0.12% of polyacrylamide (having a molecular weight of 10 million, a hydrolysis degree of 20%) and balance of water, by mass ratio.

(8) The flexible and elastic particles are produced as follows: 49.95% of styrene and 49.95% of butadiene as main agents and 0.1% of benzoyl peroxide as an initiator, by mass ratio, are polymerized to obtain a colloid, wherein the the polymerization temperature is 85 C. and the polymerization time is 70 mins. The colloid is then pelleted. The flexible and elastic particles have a particle size of 6 mm and an elongation at break of 1300%.

(9) After profile control and displacement treatment, the corresponding oil well has an oil increase rate of 8%, and a water reduction rate of 12%.

Example 4

(10) This example provides a polymer microsphere synthesized by reacting 9% of 2-acrylamide-2-methylpropanesulfonic acid and 16% of acrylamide as comonomers, 0.3% of N,N-methylenebisacrylamide as a crosslinker, 0.2% of ammonium persulfate as an initiator, 5.5% of Span 60 and 3.0% of Tween 60 as a dispersant, 45% of white oil as an external phase and balance of water as an internal phase by inverse emulsion polymerization, based on 100% of the total weight of raw materials used, wherein the polymerization temperature is 95 C. and the polymerization time is 15 mins.

(11) The polymer microsphere produced in this example has an initial particle size of 20 m and a hydration swelling rate of 15 folds.

Example 5

(12) This example provides a polymer microsphere-containing main slug comprising 5% of the polymer microsphere produced in Example 4 and 95% of water, based on 100% of the total weight of the polymer microsphere-containing main slug.

Example 6

(13) This example provides a method for in-depth profile control and displacement of low-permeability oil reservoirs, comprising the following steps:

(14) the total injection amount is designed to be 0.2 PV, i.e. 12000 m.sup.3, in a case that the daily water injection amount of the target well for profile control and displacement is 40 m.sup.3, and the controlled pore volume is 60000 m.sup.3; a flexible and elastic particle-containing pre-slug, the polymer microsphere-containing main slug produced in Example 5 and a flexible and elastic particle-containing protective slug are sequentially injected into the oil layer through the water injection well with daily injection amounts of each slug of 60 m.sup.3, 40 m.sup.3 and 60 m.sup.3 respectively, and total injection amounts of each slug of 1200 m.sup.3, 9600 m.sup.3 and 1200 m.sup.3 respectively;

(15) wherein the flexible and elastic particle-containing pre-slug comprises the following components: 0.3% of flexible and elastic particles, 0.1% of polyacrylamide (having a molecular weight of 12 million, a hydrolysis degree of 23%) and balance of water, by mass ratio;

(16) the flexible and elastic particle-containing protective slug comprises the following components: 0.4% of flexible and elastic particles, 0.15% of polyacrylamide (having a molecular weight of 12 million, a hydrolysis degree of 23%) and balance of water, by mass ratio.

(17) The flexible and elastic particles are produced as follows: 49.95% of styrene and 49.95% of butadiene as main agents and 0.1% of benzoyl peroxide as an initiator, by mass ratio, are polymerized to obtain a colloid, wherein the the polymerization temperature is 83 C. and the polymerization time is 80 mins. The colloid is then pelleted. The flexible and elastic particles have a particle size of 6 mm and an elongation at break of 1300%.

(18) The flexible and elastic particles are used to block cracks and large pore channels in the oil layer and expand the swept volume, and the polymer microsphere is used to displace the remaining oil in the oil layer. After profile control and displacement treatment, the corresponding oil well has an oil increase rate of 9.5%, and a water reduction rate of 12.5%.

Example 7

(19) This example provides a polymer microsphere synthesized by reacting 7.5% of 2-acrylamide-2-methylpropanesulfonic acid and 14% of acrylamide as comonomers, 0.25% of N,N-methylenebisacrylamide as a crosslinker, 0.15% of ammonium persulfate as an initiator, 5.25% of Span 60 and 2.75% of Tween 60 as a dispersant, 42.5% of white oil as an external phase and balance of water as an internal phase by inverse emulsion polymerization, based on 100% of the total weight of raw materials used, wherein the polymerization temperature is 100 C. and the polymerization time is 10 mins.

(20) The polymer microsphere produced in this example has an initial particle size of 20 m and a hydration swelling rate of 15 folds.

Example 8

(21) This example provides a polymer microsphere-containing main slug comprising 5% of the polymer microsphere produced in Example 7 and 95% of water, based on 100% of the total weight of the polymer microsphere-containing main slug.

Example 9

(22) This example provides a method for in-depth profile control and displacement of low-permeability oil reservoirs, comprising the following steps:

(23) the total injection amount is designed to be 0.2 PV, i.e. 12000 m.sup.3, in a case that the daily water injection amount of the target well for profile control and displacement is 40 m.sup.3, and the controlled pore volume is 60000 m.sup.3; a flexible and elastic particle-containing pre-slug, the polymer microsphere-containing main slug produced in Example 8 and a flexible and elastic particle-containing protective slug are sequentially injected into the oil layer through the water injection well with daily injection amounts of each slug of 60 m.sup.3, 40 m.sup.3 and 60 m.sup.3 respectively, and total injection amounts of each slug of 1200 m.sup.3, 9000 m.sup.3 and 1800 m.sup.3 respectively;

(24) wherein the flexible and elastic particle-containing pre-slug comprises the following components: 0.3% of flexible and elastic particles, 0.1% of polyacrylamide (having a molecular weight of 13 million, a hydrolysis degree of 24%) and balance of water, by mass ratio;

(25) the flexible and elastic particle-containing protective slug comprises the following components: 0.4% of flexible and elastic particles, 0.15% of polyacrylamide (having a molecular weight of 14 million, a hydrolysis degree of 26%) and balance of water, by mass ratio.

(26) The flexible and elastic particles are produced as follows: 49.9% of styrene and 49.9% of butadiene as main agents and 0.2% of benzoyl peroxide as an initiator, by mass ratio, are polymerized to obtain a colloid, wherein the the polymerization temperature is 82 C. and the polymerization time is 90 mins. The colloid is then pelleted. The flexible and elastic particles have a particle size of 5 mm and an elongation at break of 1200%.

(27) The flexible and elastic particles are used to block cracks and large pore channels in the oil layer and expand the swept volume, and the polymer microsphere is used to displace the remaining oil in the oil layer. After profile control and displacement treatment, the corresponding oil well has an oil increase rate of 9.5%, and a water reduction rate of 12.5%.

Example 10

(28) This example provides a polymer microsphere synthesized by reacting 6% of 2-acrylamide-2-methylpropanesulfonic acid and 12% of acrylamide as comonomers, 0.2% of N,N-methylenebisacrylamide as a crosslinker, 0.1% of ammonium persulfate as an initiator, 5.0% of Span 60 and 2.5% of Tween 60 as a dispersant, 40% of white oil as an external phase and balance of water as an internal phase by inverse emulsion polymerization, based on 100% of the total weight of raw materials used, wherein the polymerization temperature is 105 C. and the polymerization time is 5 mins.

(29) The polymer microsphere produced in this example has an initial particle size of 20 m and a hydration swelling rate of 15 folds.

Example 11

(30) This example provides a polymer microsphere-containing main slug comprising 5% of the polymer microsphere produced in Example 10 and 95% of water, based on 100% of the total weight of the polymer microsphere-containing main slug.

Example 12

(31) This example provides a method for in-depth profile control and displacement of low-permeability oil reservoirs, comprising the following steps:

(32) the total injection amount is designed to be 0.2 PV, i.e. 12000 m.sup.3, in a case that the daily water injection amount of the target well for profile control and displacement is 40 m.sup.3, the controlled pore volume is 60000 m.sup.3; a flexible and elastic particle-containing pre-slug, the polymer microsphere-containing main slug produced in Example 11 and a flexible and elastic particle-containing protective slug are sequentially injected into the oil layer through the water injection well with daily injection amounts of each slug of 60 m.sup.3, 40 m.sup.3 and 60 m.sup.3 respectively, and total injection amounts of each slug of 2400 m.sup.3, 8400 m.sup.3 and 1200 m.sup.3 respectively;

(33) wherein the flexible and elastic particle-containing pre-slug comprises the following components: 0.3% of flexible and elastic particles, 0.1% of polyacrylamide (having a molecular weight of 16 million, a hydrolysis degree of 30%) and balance of water, by mass ratio;

(34) the flexible and elastic particle-containing protective slug comprises the following components: 0.4% of flexible and elastic particles, 0.15% of polyacrylamide (having a molecular weight of 16 million, a hydrolysis degree of 30%) and balance of water, by mass ratio.

(35) The flexible and elastic particles are produced as follows: 49.85% of styrene and 49.85% of butadiene as main agents and 0.3% of benzoyl peroxide as an initiator, by mass ratio, are polymerized to obtain a colloid, wherein the the polymerization temperature is 80 C. and the polymerization time is 100 mins. The colloid is then pelleted. The flexible and elastic particles have a particle size of 6 mm and an elongation at break of 1300%.

(36) The flexible and elastic particles are used to block cracks and large pore channels in the oil layer and expand the swept volume, and the polymer microsphere is used to displace the remaining oil in the oil layer. After profile control and displacement treatment, the corresponding oil well has an oil increase rate of 10%, and a water reduction rate of 13%.

(37) Seen from above, the method for in-depth profile control and displacement of low-permeability oil reservoirs according to the present invention is a method having large injection amounts, in which different slug of profile control and displacement system are combined to block cracks and large pore channels and to displace the crude oil, thereby achieving the objective of improving oil well recovery.

(38) The above examples are merely illustrative of the present invention and are not intended to limit the scope of the invention, and all designs that are the same as or similar with the present invention are within the scope of the present invention.