# US 8,571,688 B2 · System and method for optimization of gas lift rates on multiple wells

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- Number: US 8,571,688 B2
- Document ID: US8571688B2
- Status: Granted
- Kind: B2
- Application number: 11/440,750
- Filed: 2006-05-25
- Published: 2007-11-29
- Granted: 2013-10-29
- Earliest claimed: 2006-05-25
- Assignees: Honeywell International Inc.
- Applicants: Brian A. Coward
- Inventors: Brian A. Coward
- Web page: https://patentgrep.com/patent/US8571688B2

## CPC

- E21B 43/122: {Gas lift}
- E21B 43/00: Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells (applicable only to water E03B)
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS

## Abstract

A method includes controlling a lift-gas compression process, controlling a lift-gas extraction process, and controlling a production separation process. The method also includes receiving asset data and optimizing the lift-gas compression process, the lift-gas injection process, and the production separation process according to the asset data.

## Claims

### Claim 1

A method, comprising:
controlling a lift-gas compression process associated with multiple wells using a lift-gas compression process control system, the lift-gas compression process comprising a compressor that compresses a lift gas for injection of compressed lift gas between wellheads and processing equipment to facilitate lifting of material from one or more reservoirs associated with the wells;
controlling a lift-gas extraction process associated with the multiple wells using a lift-gas extraction process control system;
controlling a production separation process using a production separation process control system, the production separation process comprising a separator, wherein operation of the separator in the production separation process affects operation of the compressor in the lift-gas compression process;
receiving process-related data associated with at least one of: one or more of the processes and the material from the one or more reservoirs; and
optimizing the lift-gas compression process control system, the lift-gas extraction process control system, and the production separation process control system based on the process-related data, wherein the optimizing comprises optimizing a gas lift rate for each of the wells by accepting an optimal gas lift rate as a quadratic optimization target for each gas lift rate, the quadratic optimization target determined based on differences between actual and desired resting values of multiple controlled variables and multiple manipulated variables;
wherein the processing equipment includes equipment performing the lift-gas extraction process and the production separation process; and
wherein the manipulated variables include a number of wells, a compressor discharge pressure, and a compressor speed.

### Claim 2 (depends on 1)

The method of claim 1, wherein the process-related data includes at least one of: equipment constraints, configuration parameters, commercial objectives, and product price.

### Claim 3 (depends on 1)

The method of claim 1, wherein the optimizing is performed using a multivariable controller that receives target values from a steady-state optimizer, the multivariable controller operating to adjust the manipulated variables to cause the controlled variables to approach the target values.

### Claim 4 (depends on 1)

The method of claim 1, wherein the controlled variables include a number of gas lift flow controllers or gas lift flow controller valve positions, a suction pressure of the compressor, wellhead pressures, a crude production rate, a compressor proximity to surge, and a compressor motor current or a gas turbine exhaust gas temperature.

### Claim 5 (depends on 4)

The method of claim 4, wherein the controlled variables further include a compressor suction valve position, a compressor recycle valve position, and a recycle gas rate.

### Claim 6

A method, comprising:
controlling a lift-gas compression process associated with multiple wells using a lift-gas compression process control system, the lift-gas compression process comprising a compressor that compresses a lift gas for injection to facilitate lifting of material from one or more reservoirs associated with the wells;
controlling a lift-gas extraction process associated with the multiple wells using a lift-gas extraction process control system;
controlling a production separation process using a production separation process control system, the production separation process comprising a separator, wherein operation of the separator in the production separation process affects operation of the compressor in the lift-gas compression process;
receiving process-related data associated with at least one of: one or more of the processes and the material from the one or more reservoirs; and
optimizing the lift-gas compression process control system, the lift-gas extraction process control system, and the production separation process control system based on the process-related data, wherein the optimizing comprises optimizing a gas lift rate for each of the wells by accepting an optimal gas lift rate as a quadratic optimization target for each gas lift rate, the quadratic optimization target determined based on differences between actual and desired resting values of one or more controlled variables and one or more manipulated variables;
wherein the quadratic optimization target for each gas lift rate is determined according to a function of:
Minimize
J
=
∑
i
⁢
b
i
×
CV
i
+
∑
i
⁢
a
i
2
⁡
(
CV
i
-
CV
0
⁢
i
)
2
+
∑
j
⁢
b
j
×
MV
j
+
∑
j
⁢
a
j
⁢
⁢
2
⁡
(
MV
j
-
MV
0
⁢
⁢
j
)
2
where:
bi represents a linear coefficient of an ith controlled variable;
bj represents a linear coefficient of a jth manipulated variable;
ai represents a quadratic coefficient of the ith controlled variable;
aj represents a quadratic coefficient of the jth manipulated variable;
CVi represents the actual resting value of the ith controlled variable;
CV0i represents the desired resting value of the ith controlled variable;
MVj represents the actual resting value of the jth manipulated variable; and
MV0j represents the desired resting value of the jth manipulated variable.

### Claim 7

A non-transitory computer readable medium embodying a computer program, the computer program comprising computer readable program code for:
controlling a lift-gas compression process associated with multiple wells using a lift-gas compression process control system, the lift-gas compression process comprising a compressor that compresses a lift gas for injection of compressed lift gas between wellheads and processing equipment to facilitate lifting of material from one or more reservoirs associated with the wells;
controlling a lift-gas extraction process associated with the multiple wells using a lift-gas extraction process control system;
controlling a production separation process using a production separation process control system, the production separation process comprising a separator, wherein operation of the separator in the production separation process affects operation of the compressor in the lift-gas compression process;
receiving process-related data associated with at least one of: one or more of the processes and the material from the one or more reservoirs; and
optimizing the lift-gas compression process control system, the lift-gas extraction process control system, and the production separation process control system based on the process-related data;
wherein the computer readable program code for optimizing comprises computer readable program code for optimizing a gas lift rate for each of the wells by accepting an optimal gas lift rate as a quadratic optimization target for each gas lift rate, the quadratic optimization target based on differences between actual and desired resting values of multiple controlled variables and multiple manipulated variables;
wherein the processing equipment includes equipment performing the lift-gas extraction process and the production separation process; and
wherein the manipulated variables include a number of wells, a compressor discharge pressure, and a compressor speed.

### Claim 8 (depends on 7)

The computer readable medium of claim 7, wherein the process-related data includes at least one of: equipment constraints, configuration parameters, commercial objectives, and product price.

### Claim 9 (depends on 7)

The computer readable medium of claim 7, wherein the computer program is executed by a multivariable controller.

### Claim 10 (depends on 7)

The computer readable medium of claim 7, wherein the controlled variables include a number of gas lift flow controllers or gas lift flow controller valve positions, a suction pressure of the compressor, wellhead pressures, a crude production rate, a compressor proximity to surge, and a compressor motor current or a gas turbine exhaust gas temperature.

### Claim 11 (depends on 10)

The computer readable medium of claim 10, wherein the controlled variables further include a compressor suction valve position, a compressor recycle valve position, and a recycle gas rate.

### Claim 12

A non-transitory computer readable medium embodying a computer program, the computer program comprising computer readable program code for:
controlling a lift-gas compression process associated with multiple wells using a lift-gas compression process control system, the lift-gas compression process comprising a compressor that compresses a lift gas for injection to facilitate lifting of material from one or more reservoirs associated with the wells;
controlling a lift-gas extraction process associated with the multiple wells using a lift-gas extraction process control system;
controlling a production separation process using a production separation process control system, the production separation process comprising a separator, wherein operation of the separator in the production separation process affects operation of the compressor in the lift-gas compression process;
receiving process-related data associated with at least one of: one or more of the processes and the material from the one or more reservoirs; and
optimizing the lift-gas compression process control system, the lift-gas extraction process control system, and the production separation process control system based on the process-related data;
wherein the computer readable program code for optimizing comprises computer readable program code for optimizing a gas lift rate for each of the wells by accepting an optimal gas lift rate as a quadratic optimization target for each gas lift rate, the quadratic optimization target based on differences between actual and desired resting values of one or more controlled variables and one or more manipulated variables; and
wherein the quadratic optimization target for each gas lift rate is determined according to a function of:
Minimize
J
=
∑
i
⁢
b
i
×
CV
i
+
∑
i
⁢
a
i
2
⁡
(
CV
i
-
CV
0
⁢
i
)
2
+
∑
j
⁢
b
j
×
MV
j
+
∑
j
⁢
a
j
⁢
⁢
2
⁡
(
MV
j
-
MV
0
⁢
j
)
2
,
where:
bi represents a linear coefficient of the ith controlled variable;
bj represents a linear coefficient of the jth manipulated variable;
ai represents a quadratic coefficient of the ith controlled variable;
aj represents a quadratic coefficient of the jth manipulated variable;
CVi represents the actual resting value of the ith controlled variable;
CV0i represents the desired resting value of the ith controlled variable;
MVj represents the actual resting value of the jth manipulated variable; and
MV0j represents the desired resting value of the jth manipulated variable.

### Claim 13

A process control system, comprising:
a lift-gas compression process control system configured to control a lift-gas compression process associated with multiple wells, the lift-gas compression process comprising a compressor that compresses a lift gas for injection of compressed lift gas between wellheads and processing equipment to facilitate lifting of material from one or more reservoirs associated with the wells;
a lift-gas extraction process control system configured to control a lift-gas extraction process associated with the multiple wells;
a production separation process control system configured to control a production separation process, the production separation process comprising a separator, wherein operation of the separator in the production separation process affects operation of the compressor in the lift-gas compression process; and
a production process control system including a multivariable controller configured to concurrently control and optimize the lift-gas compression process control system, the lift-gas extraction process control system, and the production separation process control system based on process-related data associated with at least one of: one or more of the processes and the material from the one or more reservoirs;
wherein the multivariable controller is configured to optimize the control systems by determining a gas lift rate for each of the wells, wherein the multivariable controller is operable to accept an optimal gas lift rate as a quadratic optimization target for each gas lift rate, the quadratic optimization target based on differences between actual and desired resting values of multiple controlled variables and multiple manipulated variables;
wherein the processing equipment includes equipment performing the lift-gas extraction process and the production separation process; and
wherein the manipulated variables include a number of wells, a compressor discharge pressure, and a compressor speed.

### Claim 14 (depends on 13)

The process control system of claim 13, wherein the process-related data includes at least one of: equipment constraints, configuration parameters, commercial objectives, and product price.

### Claim 15

A process control system, comprising:
a lift-gas compression process control system configured to control a lift-gas compression process associated with multiple wells, the lift-gas compression process comprising a compressor that compresses a lift gas for injection of compressed lift gas between wellheads and processing equipment to facilitate lifting of material from one or more reservoirs associated with the wells;
a lift-gas extraction process control system configured to control a lift-gas extraction process associated with the multiple wells;
a production separation process control system configured to control a production separation process, the production separation process comprising a separator, wherein operation of the separator in the production separation process affects operation of the compressor in the lift-gas compression process; and
a production process control system including a multivariable controller configured to concurrently control and optimize the lift-gas compression process control system, the lift-gas extraction process control system, and the production separation process control system based on process-related data associated with at least one of: one or more of the processes and the material from the one or more reservoirs;
wherein the multivariable controller is configured to optimize the control systems by determining a gas lift rate for each of the wells, wherein the multivariable controller is operable to accept an optimal gas lift rate as a quadratic optimization target for each gas lift rate, the quadratic optimization target based on differences between actual and desired resting values of multiple controlled variables and multiple manipulated variables;
wherein the processing equipment includes equipment performing the lift-gas extraction process and the production separation process; and
wherein the controlled variables include a number of gas lift flow controllers or gas lift flow controller valve positions, a suction pressure of the compressor, wellhead pressures, a crude production rate, a compressor proximity to surge, and a compressor motor current or a gas turbine exhaust gas temperature.

### Claim 16 (depends on 15)

The process control system of claim 15, wherein the controlled variables further include a compressor suction valve position, a compressor recycle valve position, and a recycle gas rate.

### Claim 17

A process control system, comprising:
a lift-gas compression process control system configured to control a lift-gas compression process associated with multiple wells, the lift-gas compression process comprising a compressor that compresses a lift gas for injection to facilitate lifting of material from one or more reservoirs associated with the wells;
a lift-gas extraction process control system configured to control a lift-gas extraction process associated with the multiple wells;
a production separation process control system configured to control a production separation process, the production separation process comprising a separator, wherein operation of the separator in the production separation process affects operation of the compressor in the lift-gas compression process; and
a production process control system including a multivariable controller configured to concurrently control and optimize the lift-gas compression process control system, the lift-gas extraction process control system, and the production separation process control system based on process-related data associated with at least one of: one or more of the processes and the material from the one or more reservoirs;
wherein the multivariable controller is configured to optimize the control systems by determining a gas lift rate for each of the wells, wherein the multivariable controller is operable to accept an optimal gas lift rate as a quadratic optimization target for each gas lift rate, the quadratic optimization target based on differences between actual and desired resting values of one or more controlled variables and one or more manipulated variables; and
wherein the quadratic optimization target for each gas lift rate is determined according to a function of:
Minimize
J
=
∑
i
⁢
b
i
×
CV
i
+
∑
i
⁢
a
i
2
⁡
(
CV
i
-
CV
0
⁢
i
)
2
+
∑
j
⁢
b
j
×
MV
j
+
∑
j
⁢
a
j
⁢
⁢
2
⁡
(
MV
j
-
MV
0
⁢
j
)
2
,
where:
bi represents a linear coefficient of the ith controlled variable;
bj represents a linear coefficient of the jth manipulated variable;
ai represents a quadratic coefficient of the ith controlled variable;
aj represents a quadratic coefficient of the jth manipulated variable;
CVi represents the actual resting value of the ith controlled variable;
CV0i represents the desired resting value of the ith controlled variable;
MVj represents the actual resting value of the jth manipulated variable; and
MV0j represents the desired resting value of the jth manipulated variable.

### Claim 18 (depends on 1)

The method of claim 1, wherein the quadratic optimization target for each gas lift rate is determined according to a function of:
Minimize
J
=
∑
i
⁢
b
i
×
CV
i
+
∑
i
⁢
a
i
2
⁡
(
CV
i
-
CV
0
⁢
i
)
2
+
∑
j
⁢
b
j
×
MV
j
+
∑
j
⁢
a
j
⁢
⁢
2
⁡
(
MV
j
-
MV
0
⁢
⁢
j
)
2
where:
bi represents a linear coefficient of an ith controlled variable;
bj represents a linear coefficient of a jth manipulated variable;
ai represents a quadratic coefficient of the ith controlled variable;
aj represents a quadratic coefficient of the jth manipulated variable;
CVi represents the actual resting value of the ith controlled variable;
CV0i represents the desired resting value of the ith controlled variable;
MVj represents the actual resting value of the jth manipulated variable; and
MV0j represents the desired resting value of the jth manipulated variable.

### Claim 19 (depends on 7)

The computer readable medium of claim 7, wherein the quadratic optimization target for each gas lift rate is determined according to a function of:
Minimize
J
=
∑
i
⁢
b
i
×
CV
i
+
∑
i
⁢
a
i
2
⁡
(
CV
i
-
CV
0
⁢
i
)
2
+
∑
j
⁢
b
j
×
MV
j
+
∑
j
⁢
a
j
⁢
⁢
2
⁡
(
MV
j
-
MV
0
⁢
j
)
2
,
where:
bi represents a linear coefficient of the ith controlled variable;
bj represents a linear coefficient of the jth manipulated variable;
ai represents a quadratic coefficient of the ith controlled variable;
aj represents a quadratic coefficient of the jth manipulated variable;
CVi represents the actual resting value of the ith controlled variable;
CV0i represents the desired resting value of the ith controlled variable;
MVj represents the actual resting value of the jth manipulated variable; and
MV0j represents the desired resting value of the jth manipulated variable.

### Claim 20 (depends on 13)

The process control system of claim 13, wherein the quadratic optimization target for each gas lift rate is determined according to a function of:
Minimize
J
=
∑
i
⁢
b
i
×
CV
i
+
∑
i
⁢
a
i
2
⁡
(
CV
i
-
CV
0
⁢
i
)
2
+
∑
j
⁢
b
j
×
MV
j
+
∑
j
⁢
a
j
⁢
⁢
2
⁡
(
MV
j
-
MV
0
⁢
j
)
2
,
where:
bi represents a linear coefficient of the ith controlled variable;
bj represents a linear coefficient of the jth manipulated variable;
ai represents a quadratic coefficient of the ith controlled variable;
aj represents a quadratic coefficient of the jth manipulated variable;
CVi represents the actual resting value of the ith controlled variable;
CV0i represents the desired resting value of the ith controlled variable;
MVj represents the actual resting value of the jth manipulated variable; and
MV0j represents the desired resting value of the jth manipulated variable.