High-efficiency yield-increasing exploitation method for natural gas hydrates

Patent metadata

Field	Value
Publication number	US-11952869-B1
Application number	US-202318341816-A
Country	US
Kind code	B1
Filing date	Jun 27, 2023
Priority date	Sep 13, 2022
Publication date	Apr 9, 2024
Grant date	Apr 9, 2024

Abstract

A high-efficiency yield-increasing exploitation method for natural gas hydrates includes steps of drilling of natural gas hydrate reservoirs along horizontal wells, seepage increasing by fracturing for fracture forming and stability improvement by grouting in the natural gas hydrate reservoirs, and yield improvement by combined exploitation of depressurization of the horizontal wells and heat injection; according to the present invention, drilling time is shortened by rapid drilling along the horizontal wells, the permeability of the reservoirs can be effectively improved by fracturing for fracture forming, the stability of the reservoirs can be improved by injecting foam cement slurry into the reservoirs, and the yield of the natural gas hydrates can be improved by the combined exploitation method of depressurization of the horizontal wells and heat injection.

First claim

What is claimed is:

1. A high-efficiency yield-increasing exploitation method for natural gas hydrates, comprising the following steps:
(i) drilling of natural gas hydrate reservoirs along horizontal wells
as for the natural gas hydrate reservoirs, drilling well arrays in an exploratory trench drilling manner along the horizontal wells, each of which comprising three horizontal wells: a first horizontal well, and a second horizontal well and a third horizontal well positioned on two sides of the first horizontal well, and each of the horizontal wells comprising a vertical well section, an inclined well section, and a horizontal well section;
(ii) seepage increasing by fracturing for fracture forming and stability improvement by grouting in the natural gas hydrate reservoirs
after completing a drilling operation, implementing fracturing for fracture forming at the horizontal well section of the first horizontal well, injecting a seawater fracturing fluid into the first horizontal well, and allowing the seawater fracturing fluid to flow into the natural gas hydrate reservoirs along the horizontal well section, so that fractures are formed in the hydrate reservoirs between the first horizontal well and the second horizontal well, and between the first horizontal well and the third horizontal well,
then, injecting foam cement slurry into the horizontal well section of the first horizontal well, allowing the foam cement slurry to be distributed all over the natural gas hydrate reservoirs, and curing for forming, and
finally, injecting a resin or oligomer chemical sand control agent into a periphery of the well to reduce or avoid a sand production rate during an exploitation of the natural gas hydrates at a later period; and
(iii) yield improvement by combined exploitation of depressurization of the horizontal wells and heat injection
injecting seawater into the natural gas hydrate reservoirs along the first horizontal well at a temperature of above 60° C., and meanwhile, reducing a bottom pore pressure of the second horizontal well and the third horizontal well, so as to improve a decomposition rate of the natural gas hydrates in the reservoirs under a collaborative action of the two operations.

2. The high-efficiency yield-increasing exploitation method for the natural gas hydrates according to claim 1 , wherein in step (i), an interval among different horizontal wells is determined in the following method:
firstly, based on a Darcy's law, a pressure distribution in the natural gas hydrate reservoirs is as follows:

P
2

=

P
1

+

Q
·
μ
·
L

K
·
A

(
1
)

wherein P 1 is a bottom pore pressure of the horizontal wells, MPa; P 2 is a pressure in the natural gas hydrate reservoirs, MPa; Q is a flow in pores of the natural gas hydrate reservoirs, m 3 /s; μ is a fluid viscosity in the reservoirs, mPa·s; L is a seepage radius of a fluid in the reservoirs, m; K is an absolute permeability of the natural gas hydrate reservoirs, mD; A is a sectional area of seepage flow of the natural gas hydrate reservoirs, m 2 ;
then, in order to achieve a decomposition of the natural gas hydrates during an exploitation of the natural gas hydrates under reduced pressure, the pressure P 2 in the reservoirs needs to conform to the following criteria:

P
2

≤

P
e

=

1
⁢

0
6

⁢

exp
⁡
(

∑

n
=
0

5

a
n

(

T
+

Δ
⁢

T
d

)

n

)

(
2
)

wherein

{

a
0

=

-

1
.
9

⁢
4
⁢
1
⁢
3
⁢
8
⁢
5
⁢
0
⁢
4
⁢
4
⁢
6
⁢
4
⁢
5
⁢

Assignees

• Univ China Petroleum East China
• Shandong Pengbo Safety And Environmental Prot Service Co Ltd

Inventors

• Zhang Jianbo
• Wang Zhiyuan
• Wang Yuting
• Sun Baojiang
• Zhong Jie
• Pei Jihao
• Ma Nan
• Liu Xueqi
• Hu Junjie

Classifications

• E21B41/0099 Primary

  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

• E21B7/046

  horizontal drilling (drilling with mechanical conveying means E21B7/003) · CPC title

• E21B33/138

  Plastering the borehole wall; Injecting into the formation · CPC title

• E21B43/24

  using heat, e.g. steam injection · CPC title

• E21B43/26 Primary

  by forming crevices or fractures · CPC title