Heavy oil cold production development method

Abstract

The invention belongs to the technical field of petroleum development, and relates to a thickened oil cold production development method which comprises the following steps: injecting clear water into a shaft to replace fluid in the shaft and clean impurities on the shaft wall; a front thickening water agent slug is injected into the shaft so as to improve the water absorption profile of the reservoir; injecting a viscosity-reducing composite oil-displacing agent slug into the shaft; and clear water is injected into the shaft to replace the residual reagent in the shaft. According to the heavy oil cold production and development method, the water solution containing high-molecular polyacrylamide serves as a front slug, and the oil layer production degree is improved in a synergistic mode; a viscosity-reducing composite oil-displacing agent composed of a nano-molecular wedge viscosity reducer and a high-molecular polyacrylamide aqueous solution is used as a main slug, the viscosity reducer effectively reduces the viscosity of crude oil in a stratum and improves the flowing capacity of the crude oil, and the high-molecular polyacrylamide aqueous solution increases the viscosity of a displacing fluid and expands the sweep range of the displacing fluid; the double-flow-degree effect improves the oil-water-flow-degree ratio in an oil layer, and the recovery rate of crude oil is increased

Description

Technical Field

[0001] This invention relates to the field of petroleum development technology, and in particular to a method for cold extraction and development of heavy oil. Background Technology

[0002] my country has abundant heavy oil reserves, mainly distributed in Liaohe, Xinjiang, Shengli, Turpan-Hami, and Jilin provinces. Due to the characteristics of heavy oil, such as high viscosity, high density, and poor fluidity, heavy oil extraction currently relies mainly on thermal recovery methods, including waterflooding, steam injection, steam drive, and reservoir combustion, with steam injection and steam drive being the primary methods.

[0003] In steam extraction, the difference in steam density and viscosity of heavy oil often leads to a decrease in the volumetric sweep efficiency. Furthermore, due to the characteristics of the rock-oil-water interface, a significant amount of heavy oil cannot be stripped from the rock surface, reducing the ultimate recovery rate of the crude oil. Later stages of steam development present technical challenges such as high heat loss from steam injection, demanding development technology, complex reservoir design, and difficulties in achieving uniform displacement, thus requiring improvements. Summary of the Invention

[0004] In view of this, the present invention provides a method for cold extraction and development of heavy oil.

[0005] Specifically, the present invention is achieved through the following technical solution:

[0006] According to a first aspect of the present invention, a method for cold recovery and development of heavy oil is provided, the method comprising the steps of:

[0007] Inject clean water into the wellbore to replace the fluid inside the wellbore and clean the impurities on the well wall;

[0008] Injecting a pre-thickened water slug into the wellbore to improve the reservoir water absorption profile;

[0009] Inject a viscosity-reducing composite oil displacement agent slug into the wellbore;

[0010] Clean water is injected into the well to replace the residual reagent in the well.

[0011] Optionally, the pre-thickening slug is a first polymer aqueous solution composed of a first polymer and formation water, wherein the viscosity of the first polymer aqueous solution is 100-150 mPa·s.

[0012] Optionally, the concentration of the first polymer is 2000-2500 mg / L.

[0013] Optionally, the first polymer is a first partially hydrolyzed polyacrylamide.

[0014] Optionally, the first portion of hydrolyzed polyacrylamide has a molecular weight of 25 million and a degree of hydrolysis of 23-27%.

[0015] Optionally, the viscosity-reducing composite oil displacement agent slug is an aqueous solution of the second polymer, which is composed of a viscosity reducer, a second polymer, and formation water, and the viscosity of the second polymer aqueous solution is 50-100 mPa·s.

[0016] Optionally, the concentration of the viscosity reducer is 0.20-0.40 wt%.

[0017] Optionally, the concentration of the second polymer is 0.15-0.20 wt%.

[0018] Optionally, the second polymer is a second partially hydrolyzed polyacrylamide.

[0019] Optionally, the second part of the hydrolyzed polyacrylamide has a molecular weight of 20 million and a degree of hydrolysis of 23-27%.

[0020] The technical solution provided by this invention brings at least the following beneficial effects:

[0021] This application provides a method for cold recovery of heavy oil using an aqueous solution containing high molecular weight polyacrylamide as a pre-slug, which synergistically improves the reservoir mobilization rate. A viscosity-reducing composite displacement agent composed of a nano-molecular wedge viscosity reducer and an aqueous solution containing high molecular weight polyacrylamide is used as the main slug. The viscosity reducer effectively reduces the viscosity of crude oil in the formation and improves its flowability. The aqueous solution containing high molecular weight polyacrylamide increases the viscosity of the displacement fluid and expands its sweep range. The dual mobility effect improves the oil-water mobility ratio in the reservoir and increases the oil recovery rate. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0024] Figure 1 A schematic flowchart of a method for cold recovery and development of heavy oil provided in an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of the injection method for a heavy oil cold recovery development method provided in an embodiment of the present invention;

[0026] Figure 3This is a schematic diagram of the preparation of a pre-thickening water slug in a heavy oil cold recovery development method according to an embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of the slug preparation of a viscosity-reducing composite displacement agent for a heavy oil cold recovery development method provided in an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Figure 1 The illustration schematically depicts a method for cold recovery and development of heavy oil applicable to embodiments of the present invention.

[0030] Reference Figure 1-2 As shown, this application provides a method for the cold recovery and development of heavy oil, the method comprising the following steps:

[0031] S1: Inject clean water into the well to replace the fluid inside the well and clean the impurities on the well wall;

[0032] In the embodiments of this application, in the initial state, the well casing contains fluid and the well wall contains impurities. In order to ensure subsequent development, it is necessary to inject clean water into the well casing to replace the fluid inside the well casing and clean the impurities on the well wall until the inside of the well casing is completely filled with clean water and the impurities on the well wall are removed.

[0033] S2: Inject a pre-thickening water slug into the wellbore to improve the reservoir water absorption profile;

[0034] In this embodiment of the application, in order to synergistically improve the oil reservoir utilization, a pre-thickening water slug is injected into the wellbore to improve the reservoir water absorption profile.

[0035] like Figure 3 Specifically, the pre-thickening slug is an aqueous solution of a first polymer composed of a first polymer and formation water, wherein the viscosity of the first polymer aqueous solution is 100-150 mPa·s and the concentration of the first polymer is 2000-2500 mg / L.

[0036] Specifically, the first polymer is a first-part hydrolyzed polyacrylamide, which has a molecular weight of 25 million and a degree of hydrolysis of 23-27%.

[0037] S3: Inject a viscosity-reducing composite oil displacement agent slug into the wellbore;

[0038] In this embodiment, to synergistically enhance both crude oil mobility and reduce displacement fluid mobility, a viscosity-reducing composite displacement agent slug is injected into the wellbore. The viscosity-reducing composite displacement agent slug is an aqueous solution of the second polymer, composed of a viscosity reducer, a second polymer, and formation water. The viscosity of the second polymer aqueous solution is 50-100 mPa·s, and the concentration of the viscosity reducer is 0.20-0.40 wt%.

[0039] like Figure 4 Specifically, the concentration of the second polymer is 0.15-0.20 wt%, the second polymer is a second-part hydrolyzed polyacrylamide, the second-part hydrolyzed polyacrylamide has a molecular weight of 20 million and a degree of hydrolysis of 23-27%.

[0040] Specifically, the viscosity reducer used in the aforementioned viscosity-reducing composite oil displacement agent slug is a viscosity reducer containing nano-molecular wedges. This viscosity reducer is a nanomaterial synthesized mainly based on metallic molybdenum, and is compositely assembled with flexible active macromolecular wedges.

[0041] S4: Inject clean water into the wellbore to replace the residual reagent in the wellbore.

[0042] In this embodiment of the application, after the reaction is completed, clean water is injected into the wellbore to replace the residual reagents in the wellbore, so as to achieve efficient development of heavy oil and significantly improve the recovery rate.

[0043] This application provides a method for cold recovery of heavy oil using an aqueous solution containing high molecular weight polyacrylamide as a pre-slug, which synergistically improves the reservoir mobilization rate. A viscosity-reducing composite displacement agent composed of a nano-molecular wedge viscosity reducer and an aqueous solution containing high molecular weight polyacrylamide is used as the main slug. The viscosity reducer effectively reduces the viscosity of crude oil in the formation and improves its flowability. The aqueous solution containing high molecular weight polyacrylamide increases the viscosity of the displacement fluid and expands its sweep range. The dual mobility effect improves the oil-water mobility ratio in the reservoir and increases the oil recovery rate.

[0044] It should be noted that in this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0045] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0046] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0047] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0048] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for cold extraction and development of heavy oil, characterized in that, The method includes the following steps: Inject clean water into the wellbore to replace the fluid inside the wellbore and clean the impurities on the well wall; Injecting a pre-thickened water slug into the wellbore to improve the reservoir water absorption profile; Inject a viscosity-reducing composite oil displacement agent slug into the wellbore; Clean water is injected into the well to replace the residual reagent in the well.

2. The method for cold recovery and development of heavy oil according to claim 1, characterized in that, The pre-thickening slug is an aqueous solution of a first polymer composed of a first polymer and formation water, and the viscosity of the first polymer aqueous solution is 100-150 mPa·s.

3. The method for cold recovery and development of heavy oil according to claim 2, characterized in that, The concentration of the first polymer is 2000-2500 mg / L.

4. The method for cold recovery and development of heavy oil according to claim 2, characterized in that, The first polymer is a first-part hydrolyzed polyacrylamide.

5. The method for cold recovery and development of heavy oil according to claim 4, characterized in that, The first part of the hydrolyzed polyacrylamide has a molecular weight of 25 million and a degree of hydrolysis of 23-27%.

6. The method for cold recovery and development of heavy oil according to claim 1, characterized in that, The viscosity-reducing composite oil displacement agent slug is an aqueous solution of the second polymer, which is composed of a viscosity reducer, a second polymer, and formation water. The viscosity of the second polymer aqueous solution is 50-100 mPa·s.

7. The method for cold recovery and development of heavy oil according to claim 6, characterized in that, The concentration of the viscosity reducer is 0.20-0.40 wt%.

8. The method for cold recovery and development of heavy oil according to claim 6, characterized in that, The concentration of the second polymer is 0.15-0.20 wt%.

9. The method for cold recovery and development of heavy oil according to claim 6, characterized in that, The second polymer is a second-part hydrolyzed polyacrylamide.

10. The method for cold recovery and development of heavy oil according to claim 9, characterized in that, The second part of the hydrolyzed polyacrylamide has a molecular weight of 20 million and a degree of hydrolysis of 23-27%.

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