Exploiting structure for natural gas hydrate reservoir and exploiting method for natural gas hydrate by injecting hydraulic calcium oxide via gas fracturing

Patent metadata

Field	Value
Publication number	US-2021270117-A1
Application number	US-202016943811-A
Country	US
Kind code	A1
Filing date	Jul 30, 2020
Priority date	Feb 28, 2020
Publication date	Sep 2, 2021
Grant date	—

Abstract

The present invention discloses an exploiting structure for a natural gas hydrate reservoir, comprising: a drilling well located in the natural gas hydrate reservoir; and a fractured fracture provided in communication with the drilling well, which is located in the natural gas hydrate reservoir and in which a gas containing calcium oxide powder is provided. In the present invention, the calcium oxide powder is filled with the fractured fracture by means of the gas. Then, the natural gas hydrate in the fractured fracture is decomposed, and the water generated from the decomposition reacts with the calcium oxide to release a large amount of heat, and a high-porosity calcium hydroxide filler can be formed. The exploiting method provided in the present invention is simple and easy to operate, and has low exploitation costs, and is suitable for commercial promotion and application.

First claim

1 . An exploiting structure for a natural gas hydrate reservoir, comprising:
a drilling well located in the natural gas hydrate reservoir; and a fractured fracture provided in communication with the drilling well, which is located in the natural gas hydrate reservoir and in which a gas containing calcium oxide powder is provided.

2 . The exploiting structure according to claim 1 , wherein the drilling well includes a vertical well and/or a horizontal well;
the fractured fracture has a width of 0.1 to 100 mm and a length of 10 to 300 m; the number of the fractured fracture is one or more; and the angle between the length direction of the fractured fracture and the length direction of the drilling well is 45° to 140°.

3 . The exploiting structure according to claim 1 , wherein the fractured fracture is formed by perforation and high-pressure gas fracturing;
the calcium oxide includes hydraulic lime; the calcium oxide powder has a particle size of 0.001 to 10 mm; and the gas containing calcium oxide powder has a calcium oxide concentration of 5 to 90 kg/kg and a pressure of 1 to 60 MPa.

4 . The exploiting structure according to claim 1 , wherein the gas includes air;
the drilling well has a diameter of 100 to 800 mm; the gas containing calcium oxide powder is also provided in the drilling well; and after the drilling well is depressurized, in the fractured fracture, the water in the natural gas hydrate reservoir forms calcium hydroxide with the calcium oxide, and the calcium hydroxide forms a hard filler with sediments in the natural gas hydrate reservoir.

5 . An exploiting method for a natural gas hydrate reservoir, comprising the steps of:
1) laying a drilling platform in a natural gas hydrate occurrence area for drilling construction, to construct a drilling well entering the natural gas hydrate reservoir; 2) perforating the drilling well located in the natural gas hydrate reservoir to form a perforated fracture in the natural gas hydrate reservoir around the drilling well; 3) fracturing the natural gas hydrate reservoir with a gas containing calcium oxide powder through the drilling well, such that the gas containing calcium oxide powder enters the perforated fracture; and 4) depressurizing the drilling well, pumping water and exploiting the natural gas.

6 . The exploiting method according to claim 5 , wherein the exploiting method is a method of depressurization and backfilling with in-situ supplemental heat;
the natural gas hydrate occurrence area includes a natural gas hydrate occurrence area in a sea area; and the drilling platform includes a drilling platform in seawater.

7 . The exploiting method according to claim 5 , wherein the drilling well includes a horizontal well and/or a vertical well, in which the vertical well is specifically drilled by passing a drilling well through the seawater and overlying strata respectively, followed by entering the natural gas hydrate reservoir; and the horizontal well includes a vertical section and a horizontal section, and the horizontal well is specifically drilled by passing a vertical section of a drilling well through the seawater and overlying strata respectively followed by entering the natural gas hydrate reservoir, and then drilling a horizontal section in the natural gas hydrate reservoir.

8 . The exploiting method according to claim 7 , wherein the step 2) is performed after the drilling is completed;
the perforating includes one or more of uniform perforation, spiral-phase perforation and hydraulic jet perforation; the perforated fracture is specifically in a form of a plurality of perforated fractures uniformly distributed; and the perforated fracture is distributed in the vertical section and/or the horizontal section of the horizontal well.

9 . The exploiting method according to claim 5 , wherein the pressure of the fracturing is 1 to 60 MPa;
the perforating and the fracturing are multi-stage clustering perforation and staged fracturing; the depressurizing is specifically by reducing the wellhead pressure of the drilling well after the fracturing is stopped; and the wellhead pressure of the drilling well is greater than or equal to 1 MPa after the depressurizing.

10 . The exploiting method according to claim 5 , wherein the pumping water is pumping water in the natural gas hydrate reservoir and water generated by the decomposition of the natural gas hydrate from the wellbore of the drilling well;
the natural gas generated by the decomposition of the natural gas hydrate migrates from the wellbore of the drilling well to the wellhead thereof for gas production; and the exploiting method further comprises a process of repeating the fracturing step and/or continuing to reduce the wellhead pressure so as to increase and maintain the gas production rate.

Assignees

• Inst Geology & Geophysics Cas

Inventors

• Li Shouding
• Li Xiao
• Wang Sijing
• Sun Yiming

Classifications

• E21B41/0099

  specially adapted for drilling for or production of natural hydrate or clathrate gas reservoirs; Drilling through or monitoring of formations containing gas hydrates or clathrates · CPC title

• E21B43/2605

  using gas or liquefied gas · CPC title

• E21B43/295 Primary

  Gasification of minerals, e.g. for producing mixtures of combustible gases (E21B43/243 takes precedence) · CPC title

• E21B43/305

  comprising at least one inclined or horizontal well · CPC title

• E21B43/267

  reinforcing fractures by propping · CPC title