Active control method and control device for wellbore pressure in the open-cycle drilling of marine natural gas hydrates

Patent metadata

Field	Value
Publication number	US-11002126-B2
Application number	US-202017110354-A
Country	US
Kind code	B2
Filing date	Dec 3, 2020
Priority date	Aug 4, 2020
Publication date	May 11, 2021
Grant date	May 11, 2021

Abstract

An active control method and system for wellbore pressure in open-cycle drilling in marine natural gas hydrates. The system comprises a drilling system, a drilling fluid injection system, and a data processing system for conducting the drilling operation.

First claim

What is claimed is:

1. An active control method for wellbore pressure in the open-cycle drilling of marine Natural Gas Hydrates (NGH), which comprises steps as follows:
(1) generating drilling parameters for an injection displacement of a drilling fluid, a pump pressure in a wellhead, and an injection temperature of the drilling fluid during a drilling based on data of the marine NGH reservoirs to be drilled;
(2) carrying out the open-cycle drilling according to the drilling parameters by injecting seawater into a drill pipe as the drilling fluid to carry cuttings from a bottom hole and discharging the seawater out of subsea wellhead through an annulus between the drill pipe and a casing pipe;
(3) monitoring temperature and pressure of the bottom-hole by an Annular Pressure While Drilling (APWD) in real time for correcting temperature and pressure of the annulus; determining occurrence of a hydrate decomposition in the annulus which further predicts occurrence of a shallow gas intrusion in the bottom hole, and collecting data for an intelligent active control of wellbore pressure;
(4) automatically controlling and adjusting mixed density of the drilling fluid, injection displacement of the drilling fluid, the injection temperature of the drilling fluid and the pump pressure in the wellhead during well killing when the occurrence of the hydrate decomposition in the annulus or the occurrence of the shallow gas intrusion in the bottom hole based on a real-time processing results of signal fluctuations, which are detected by the APWD, by a processor of the APWD; injecting the drilling fluid into the bottom hole via the drill pipe based on above well-killing parameters; if no hydrate decomposition occurs in the annulus and no shallow gas invasion occurs in the bottom hole, continuing with the drilling according to the drilling parameters set in step (1) until drilling is completed.

2. The active control method for wellbore pressure in the open-cycle drilling of marine natural gas hydrates according to claim 1 , characterized in that the injection displacement of the drilling fluid during the drilling in step (1) satisfies the following relational formula:
Q min <Q<Q max   (1)

wherein Q min denotes a theoretical minimum displacement, m 3 /min; Q max denotes a theoretical maximum displacement, m 3 /min; and Q denotes the injection displacement of the drilling fluid during the drilling;
among them, the theoretical minimum displacement Q min satisfies the following relational formula:
Q min =max( Q p ,Q x ,Q q )  (2)

wherein Q p denotes a minimum rock-breaking displacement, m 3 /min; Q x denotes a minimum cutting-carrying displacement, m 3 /min; and Q q denotes a minimum displacement used to prevent the shallow gas intrusion, m 3 /min;
the minimum rock-breaking displacement Q p satisfies the following relational formula:

Q
p

=

k
f

⁢
π
⁢

⁢

d
ne
2

⁡

(

S
u

⁢

k

2

⁢

x
2

1
⁢
6
⁢
λ
⁢

ρ
m

⁢

R
0
2

)

0.5

(
3
)

wherein k f denotes a bit nozzle flow coefficient, which shall fall within 0.95-0.97; d ne denotes an equivalent diameter of the bit nozzle, m; S u denotes shearing strength of soil, Pa; k denotes half-width coefficient of jet flow; x denotes an impact flow path of the jet flow, m; λ denotes a pressure drop coefficient of the jet flow; ρ m denotes a density of the drilling fluid in the drill pipe, kg/m 3 ; and R 0 denotes a bit nozzle radius, m;
the minimum cutting-carrying displacement Q x satisfies the following relational formula:

Q
x

=

π

4
⁢
0
⁢
0
⁢
0

⁢

(

d
w
2

-

d
po
2

)

⁢

v
a

(
4
)

wherein d w denotes an inner diameter of a borehole, m; d po denotes an outer diameter of the drill pipe, m; and ν a denotes a flow velocity of the drilling fluid in the annulus, m/s;
the minimum displacement required for prevention of the shallow gas intrusion Q q satisfies the followin

Assignees

• Univ China Petroleum East China

Inventors

• Wang Zhiyuan
• Zhang Jianbo
• Sun Baojiang
• Lou Wenqiang
• Sun Xiaohui
• Liu Zheng
• Tong Shikun

Classifications

• E21B21/08 Primary

  Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure (valve arrangements therefor E21B21/10) · CPC title

• 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

• E21B47/008

  Monitoring of down-hole pump systems, e.g. for the detection of "pumped-off" conditions · CPC title

• E21B47/047

  Liquid level (measuring depth or liquid level using radioactive markers E21B47/053) · CPC title

• E21B47/07

  Temperature · CPC title