Control method and control device for drilling operations

Patent metadata

Field	Value
Publication number	US-10337267-B1
Application number	US-201816122656-A
Country	US
Kind code	B1
Filing date	Sep 5, 2018
Priority date	Sep 5, 2018
Publication date	Jul 2, 2019
Grant date	Jul 2, 2019

Abstract

The invention relates to the field of stratum drilling, and in particular to a control method and a control device for drilling operations. The control method comprises: detecting whether an overflow occurs in a well; controlling the wellhead back pressure based on a preset bottom hole pressure when no overflow occurs in the well, in order to keep the bottom hole pressure stable; and performing a shut-in operation and controlling the wellhead back pressure based on the increase in fluid discharge returned from an annulus of the well when an overflow occurs in the well, so as to keep the bottom hole pressure stable and prevent the gas in the stratum from continuing to invade into the drilling fluid during the process that the overflow drilling fluid is discharged from the bottom of the well. The control method and control device make it possible to prevent drastic fluctuation of the wellhead back pressure caused by the expansion of the invaded gases during the discharge thereof during the drilling operation, thereby realizing the stable control of the wellhead back pressure.

First claim

The invention claimed is:

1. A control method for drilling operations, wherein the control method comprises:
detecting an overflow occurring in a well;
performing a shut-in operation and controlling the wellhead back pressure based on an increase in fluid discharge returned from an annulus of the well, so as to keep the bottom hole pressure stable and prevent a gas in the stratum from continuing to invade drilling fluid during process that overflow drilling fluid is discharged from annular of the well, wherein the controlling the wellhead back pressure based on the increase in fluid discharge returned form the annulus of the well comprises:
controlling the wellhead back pressure to a first back pressure in an initial stage after the shut-in operation;
controlling the wellhead back pressure to a second back pressure after the initial stage lasts for a predetermined period of time and before a gas overflow is detected at the wellhead; and
controlling the wellhead back pressure to a third back pressure when a gas overflow is detected at the wellhead
wherein the control method further comprises, after performing the shut-in operation:
determining whether the gas contains an acid gas based on an actual increase in fluid discharge and a calculated value of the increase in fluid discharge, the calculated value of the increase in fluid discharge is calculated according to a gas state equation;
calculating, if the gas contains the acid gas, the total amount of the acid gas based on a methane solubility chart, an acid gas solubility chart, a pressure distribution of the annulus, and a total gas volume;
calculating a critical pressure for keeping the acid gas in supercritical state based on the total amount of the acid gas, a temperature and pressure field of the wellbore, a dissolution pattern and phase state curve of the acid gas; and
regulating the wellhead back pressure based on the critical pressure to prevent the gas in the stratum from continuing to invade into the drilling fluid,
wherein the regulating the wellhead back pressure based on the critical pressure comprises:

calculating a fourth back pressure based on the critical pressure; and regulating the wellhead back pressure based on a stage corresponding to the first back pressure, the second back pressure, and the third back pressure respectively, and a maximum value between the fourth back pressure and one of the first back pressure, the second back pressure, and the third back pressure.

2. The control method according to claim 1 , wherein the detecting whether the overflow occurs in the well comprises:
detecting a discharge amount of fluid returned from the annulus of the well; and
determining whether the overflow occurs in the well based on the discharge amount of fluid.

3. The control method according to claim 1 , wherein the control method further comprises:
separating liquid and gas in the overflow drilling fluid after the overflow drilling fluid is discharged out of the well, when the overflow occurs in the well.

4. The control method according to claim 1 , wherein the first back pressure is determined by the following formula:

p

a
⁢

⁢
0

=

p
d

+

V

K
⁢

⁢
0

A
a

⁢

(

ρ
m

-

ρ

g
⁢

⁢
1

)

⁢
g

,

⁢

ρ

g
⁢

⁢
1

=

z
0

⁡

(

p
d

+

p
b

)

⁢

T
0

z
1

⁢

p
0

⁢

T
b

⁢

ρ

g
⁢

⁢
0

,

wherein p a0 is the first back pressure, V k0 is the increase in fluid discharge when the overflow occurs, p d is the read riser pressure, A a is cross-sectional area of the annulus of an open hole section, ρ m is density of the drilling fluid when no invaded gas is present, ρ g1 is density of a invaded gas at the bottom of the well, z 0 is methane compression factor in a standard state, T 0 is temperature in the standard state, p 0 is standard atmospheric pressure, ρ g0 is methane density in the standard state, T b is the bottom hole temperature, z 1 is the methane compression factor at bottom hole temperature and pressure conditions, and p b is a designed bottom hole pressure,
the second back pressure is determined by the following formula:
p a1 =p a0 +p ml ,

Assignees

• Univ China Petroleum East China

Inventors

• Wang Zhiyuan
• Pan Shaowei
• Sun Baojiang
• Zhang Jianbo
• Yu Jing

Classifications

• E21B44/00

  Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions · CPC title

• E21B43/34

  Arrangements for separating materials produced by the well · CPC title

• 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