Method for improving yield of tight gas well by injecting air after fracturing

Abstract

The invention discloses a method for improving the yield of a tight gas well by injecting air after fracturing, and belongs to the technical field of natural gas extraction. The method mainly comprises the following steps: (1) connecting a manifold; (2) testing pressure and leakage; (3) fracturing construction; (4) fracturing fluid is flowback; (5) injecting air; (6) soaking; and (7) opening the well for production. According to the method, air is injected after the tight gas well is fractured and flowback, oxygen in the air can accelerate oxidative degradation of the thickening agent, and damage of the thickening agent to a reservoir is reduced; meanwhile, the air can push a residual thickening agent solution and formation water in a near-well reservoir to the deep part of the reservoir, so that the influence of the Jamin effect on the fracturing effect of the tight gas well can be reduced, and the yield of the tight gas well is improved; in addition, the method has the characteristics of simple process, wide application range and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of natural gas extraction, and in particular relates to a method for increasing the production of tight gas wells by injecting air after fracturing. Background Art

[0002] my country boasts abundant tight gas reserves, primarily distributed in the Ordos, Sichuan, Songliao, Bohai Bay, Tarim, Tuha, and Junggar basins, accounting for 93% of the country's total tight gas reserves. By 2024, tight gas production in my country will exceed 60 billion cubic meters, accounting for over 60% of total unconventional natural gas production, ranking first in the world and becoming a core growth engine for increasing domestic natural gas reserves and production.

[0003] Due to the properties of tight gas reservoirs, tight gas wells require fracturing before production to achieve optimal yields. The thickeners used during fracturing can remain in the reservoir due to incomplete flowback or degradation, causing damage. Furthermore, the presence of residual thickener solution and formation water in the reservoir near the wellbore causes the Jamin effect as natural gas seeps through the reservoir, increasing flow resistance and reducing the yield of tight gas wells after fracturing.

[0004] In order to improve the development effect of tight gas, it is necessary to optimize the fracturing process so that it can further reduce the damage of thickeners to the reservoir and further reduce the impact of the Jamin effect on the fracturing effect of tight gas wells. Summary of the Invention

[0005] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for increasing the production of tight gas wells by injecting air after fracturing.

[0008] In order to solve the above technical problems, the present invention provides the following technical solution: a method for increasing the production of tight gas wells by injecting air after fracturing, characterized in that: it includes:

[0009] Connect the manifold; perform pressure and leak testing; perform fracturing operation; return fracturing fluid; inject air; shut down the well; and start production.

[0010] As a preferred embodiment of the method of the present invention, the speed of injecting air is 1200 to 2400 standard cubic meters per hour, and the amount of injected air is 50,000 to 100,000 standard cubic meters.

[0011] As a preferred embodiment of the method of the present invention, the soaking time is 3 to 5 days.

[0012] As a preferred embodiment of the method of the present invention, the mass concentration of the thickener in the fracturing fluid is 0.1%.

[0013] As a preferred embodiment of the method of the present invention, the thickener in the fracturing fluid comprises acrylic acid, acrylamide, methacryloylethyl sulfobetaine and a mixture of initiators APS and SDS.

[0014] As a preferred embodiment of the method of the present invention, the pH value of the thickener in the fracturing fluid is 7.

[0015] As a preferred embodiment of the method of the present invention, the molar ratio of APS to SDS in the mixture of the initiators APS and SDS is 1:1.

[0016] Beneficial effects of the present invention:

[0017] The method for increasing the production of tight gas wells disclosed herein involves injecting air after fracturing and flowback in a tight gas well. The oxygen in the air accelerates the oxidative degradation of the thickener, further reducing damage to the reservoir. Simultaneously, the air pushes residual thickener solution and formation water in the near-well reservoir to deeper levels, reducing the impact of the Jamin effect on the fracturing efficiency of the tight gas well, thereby increasing the production of the tight gas well. Furthermore, the method has the advantages of simple process and wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0019] Figure 1 It is an implementation flow chart of the present invention. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0023] The thickener preparation method of the present invention includes the following steps: adding a certain amount of acrylic acid and deionized water to a wide-mouth bottle, adjusting the pH to 7 with NaOH, adding acrylamide and methacryloylethyl sulfobetaine, and stirring until completely dissolved. Deionized water is then added to bring the total monomer concentration to 25%. The bottle is placed in a 40°C constant-temperature water bath and, after nitrogen is introduced for 10 minutes, a mixture of initiators (APS and SDS) (a molar ratio of 1:1) is added, at a concentration of 0.15% of the total monomer mass. The mixture is then allowed to react at this constant temperature for 4 hours to obtain the terpolymer thickener AA-AM-SBMA.

[0024] In the embodiment of the present invention, the volume percentage of nitrogen in the injected air is 78%, the volume percentage of oxygen is 21%, and the volume percentage of rare gases (helium, neon, argon, krypton, xenon, radon), carbon dioxide and other substances is 1%.

[0025] Example 1

[0026] This embodiment provides a method for increasing the production of a tight gas well by injecting air after fracturing, comprising the following steps: (1) connecting a manifold; (2) performing a pressure test and leak detection; (3) performing fracturing operation; (4) returning the fracturing fluid; (5) injecting air; (6) soaking the well; and (7) starting the well for production. Specific application scenarios are:

[0027] Well A-1 is a tight gas well in the B2 block in the eastern Sichuan Basin. It is an adjacent well in the same layer of Well A-4. It underwent fracturing construction before being put into production. The mass concentration of the thickener in the fracturing fluid used was 0.1%, and the injection volume of the fracturing fluid was 3,000 cubic meters. The return rate of the fracturing fluid after fracturing was 85.2%. Then, 50,000 standard cubic meters of air were injected at a rate of 1,200 standard cubic meters per hour. The well was shut down for 3 days. The average daily gas production after 60 days of production was 32,575 cubic meters.

[0028] Example 2

[0029] This embodiment applies the method of Example 1 to Well A-2, specifically:

[0030] Well A-2 is a tight gas well in the B2 block in the eastern Sichuan Basin. It is an adjacent well in the same layer of Well A-4. It underwent fracturing construction before being put into production. The mass concentration of the thickener in the fracturing fluid used was 0.1%, and the injection volume of the fracturing fluid was 3,000 cubic meters. The return rate of the fracturing fluid after fracturing was 85.6%. Then, 100,000 standard cubic meters of air were injected at a rate of 2,400 standard cubic meters per hour. The well was shut down for 5 days. The average daily gas production after 60 days of production was 35,283 cubic meters.

[0031] Example 3

[0032] This embodiment applies the method of Example 1 to Well A-3, specifically:

[0033] Well A-3 is a tight gas well in Block B2 in the eastern Sichuan Basin. It is an adjacent well in the same layer of Well A-4. It underwent fracturing before being put into production. The mass concentration of the thickener in the fracturing fluid used was 0.1%, and the injection volume of the fracturing fluid was 3,000 cubic meters. The return rate of the fracturing fluid after fracturing was 85.4%. Then, 80,000 standard cubic meters of air were injected at a rate of 1,800 standard cubic meters per hour. The well was shut down for 4 days. The average daily gas production after 60 days of production was 33,250 cubic meters.

[0034] Comparative Example 1

[0035] This comparative example provides a natural gas production method without air injection after fracturing and is applied to the A-4 well, specifically:

[0036] Well A-4 is a tight gas well in Block B2 in the eastern Sichuan Basin. It is located in the same layer adjacent to Wells A-1, A-2, and A-3. It underwent fracturing before being put into production. The mass concentration of the thickener in the fracturing fluid used was 0.1%, and the injection volume of the fracturing fluid was 3,000 cubic meters. The return rate of the fracturing fluid after fracturing was 85.5%. Subsequently, the well was put into production, and the average daily gas production over 60 days was 28,692 cubic meters.

[0037] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A method for increasing the production of tight gas wells by post-fracture air injection, characterized in that: include, Connect the manifold; perform pressure and leak testing; perform fracturing operation; return fracturing fluid; inject air; shut down the well; and start production.

2. The method according to claim 1, wherein: The speed of injecting air is 1200 standard cubic meters per hour to 2400 standard cubic meters per hour, and the amount of injected air is 50,000 standard cubic meters to 100,000 standard cubic meters.

3. The method according to claim 1, wherein: The soaking time is 3 to 5 days.

4. The method according to claim 1, wherein: The mass concentration of the thickener in the fracturing fluid is 0.1%.

5. The method according to claim 1, wherein: The thickener in the fracturing fluid comprises acrylic acid, acrylamide, methacryloylethyl sulfobetaine and a mixture of initiators APS and SDS.

6. The method according to claim 1, wherein: The pH of the thickener in the fracturing fluid is 7.

7. The method according to claim 1, wherein: The molar ratio of APS to SDS in the mixture of the initiators APS and SDS is 1:1.

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