System for flushing a gas-measurement device for analyzing gas from a well, and related methods

1. A gas-analysis system, comprising:

a gas chromatograph comprising a column;

a sample-gas line configured to direct a flow of a sample gas to a first valve and a second valve, the flow of the sample gas defining an upstream direction and a downstream direction;

a flushing system between the sample-gas line and the column of the gas chromatograph, positioned downstream of the sample-gas line, and positioned upstream of the column of the gas chromatograph, the flushing system comprising:

a sample-gas outlet configured to move the sample gas out of the flushing system;

a flushing-gas inlet configured to direct a flushing gas to the second valve;

a testing-gas line configured to direct either the sample gas or the flushing gas to the column of the gas chromatograph;

the first valve between the sample-gas line and the sample-gas outlet, the first valve configured to either allow or prevent the sample gas to flow to the sample-gas outlet;

the second valve between the sample-gas line, the flushing-gas inlet, and the testing-gas line, positioned downstream of the sample-gas line, and positioned upstream of the testing-gas line, the second valve configured to allow the sample gas from the sample-gas line to flow to the testing-gas line while in a first valve position or allow the flushing gas from the flushing-gas inlet to flow through and flush the testing-gas line while in a second valve position; and

the gas chromatograph configured to analyze the sample gas received from the testing-gas line based on a speed at which components of the sample gas move through the column; and

a control system, the control system configured to control operation of the first valve and the second valve to configure the gas-analysis system into modes of operation, the modes of operation comprising:

a testing mode wherein the first valve is configured to prevent the sample gas from flowing from the sample-gas line to the sample-gas outlet and the second valve is in the first valve position to allow the sample gas to flow from the sample-gas line to the testing-gas line and prevent the flushing gas from flowing from the flushing-gas inlet to the testing-gas line, the testing mode comprises a testing-mode time duration; and

a flushing mode wherein the first valve is configured to allow the sample gas to flow from the sample-gas line to the sample-gas outlet and the second valve is in the second valve position to allow the flushing gas to flow from the flushing-gas inlet to the testing-gas line and prevent the sample gas from flowing from the sample-gas line to the testing-gas line, the flushing mode comprises a flushing-mode time duration,

wherein the flushing-mode time duration is shorter than the testing-mode time duration.

2. The gas-analysis system of claim 1 , wherein the gas-analysis system is configured to be used above-ground, the gas-analysis system further comprising a gas-extraction unit operatively coupled to the sample-gas line, the gas-extraction unit configured to obtain the sample gas from drilling mud above-ground.

3. The gas-analysis system of claim 1 , further comprising a gas-capture unit operatively coupled to the sample-gas line, and wherein the gas-analysis system and the gas-capture unit are positioned below-ground and are implemented in one or more of a flowline string, a casing string, a production string, a wireline tool, a completion tool, and a drilling tool, and the gas-capture unit is configured to obtain the sample gas below-ground.

4. The gas-analysis system of claim 1 , wherein the flushing system further comprises a gas pump operatively coupled to the flushing-gas inlet, the gas pump configured to pump the flushing gas through the second valve and the testing-gas line and into the gas chromatograph while the second valve is in the second valve position.

5. The gas-analysis system of claim 1 , wherein the sample gas comprises a first sample gas and a second sample gas and the control system is configured to:

configure the gas-analysis system into the testing mode to provide the first sample gas at the gas chromatograph;

instruct the gas chromatograph to analyze the first sample gas;

configure the gas-analysis system into the flushing mode to flush the first sample gas from the testing-gas line;

configure the gas-analysis system into the testing mode to provide the second sample gas at the gas chromatograph; and

instruct the gas chromatograph to analyze the second sample gas.

6. The gas-analysis system of claim 1 , wherein the flushing-gas inlet includes multiple flushing-gas lines to provide multiple flushing gases.

7. The gas-analysis system of claim 1 , wherein the first valve is configured to provide a calibration gas to the gas chromatograph.

8. The gas-analysis system of claim 1 , wherein the flushing-mode time duration is shorter than 30 seconds and the testing-mode time duration is 30 seconds or longer than 30 seconds.

9. A method for analyzing sample gases at a gas chromatograph, the method comprising:

at a first time:

allowing a first sample gas, using a first valve and a second valve of a flushing system between a sample-gas line and a gas chromatograph, to move from the sample-gas line to a testing-gas line, the testing-gas line configured to receive the first sample gas from the second valve while the second valve is in a first position and direct the first sample gas to the gas chromatograph, the gas chromatograph comprising a column, the gas chromatograph configured to analyze a gas based on a speed at which components of the gas move through the column;

preventing a flushing gas, using the second valve, from moving from a flushing-gas inlet to the testing-gas line while the second valve is in the first position; and

analyzing the first sample gas at the gas chromatograph;

at a second time:

preventing the first sample gas, using the first valve and the second valve, from moving from the sample-gas line to the testing-gas line; and

allowing the flushing gas, using the second valve while the second valve is in a second position, to move from the flushing-gas inlet to the testing-gas line; and

at a third time:

allowing a second sample gas, using the first valve and the second valve, to move from the sample-gas line to the testing-gas line;

preventing the flushing gas, using the second valve, from moving from the flushing-gas inlet to the testing-gas line; and

analyzing the second sample gas at the gas chromatograph.

10. The method of claim 9 , further comprising, prior to the first time, capturing the first sample gas below-ground, wherein analyzing the first sample gas at the gas chromatograph comprises analyzing the first sample gas while the gas chromatograph is located below-ground.

11. The method of claim 9 , further comprising, prior to the first time, obtaining the first sample gas during one or more of drilling operations, completion operations, and production operations.

12. The method of claim 9 , wherein the second time follows the first time by a testing-mode time duration and the third time follows the second time by a flushing-mode time duration, wherein the flushing-mode time duration is shorter than the testing-mode time duration.

13. The method of claim 12 , wherein the flushing-mode time duration is shorter than 30 seconds and the testing-mode time duration is 30 seconds or longer than 30 seconds.

14. The method of claim 9 , further comprising, at the second time, allowing the first sample gas to move from the sample-gas line to a sample-gas outlet through the first valve, the first valve positioned between the sample-gas line and the sample-gas outlet,

wherein allowing the first sample gas to move from the sample-gas line to the gas chromatograph at the first time further comprises decoupling the sample-gas line from the sample-gas outlet at the first valve.

15. A well-gas analysis system comprising:

a gas trap for capturing a sample gas from a well, the gas trap operatively coupled to a sample-gas line;

a gas chromatograph comprising a column, the gas chromatograph configured to analyze the sample gas based on a speed at which components of the sample gas move through the column; and

a flushing system between the sample-gas line and the gas chromatograph, the flushing system comprising:

a multi-way valve between the sample-gas line, a sample-gas outlet, a flushing-gas inlet, and a testing-gas line, the multi-way valve positioned downstream of the sample-gas line and the flushing-gas inlet and positioned upstream of the sample-gas outlet and the testing-gas line, the testing-gas line configured to direct the sample gas to the gas chromatograph, the multi-way valve configured to:

in a first position, allow the sample gas to flow from the sample-gas line to the sample-gas outlet and allow a flushing gas to flow from the flushing-gas inlet to the testing-gas line; and

in a second position, prevent the sample gas from flowing from the sample-gas line to the sample-gas outlet, prevent the flushing gas from flowing from the flushing-gas inlet to the testing-gas line, and allow the sample gas to flow from the sample-gas line to the testing-gas line providing the sample gas to the gas chromatograph.

16. The well-gas analysis system of claim 15 , wherein the well-gas analysis system is configured to be implemented in a downhole tool in one or more of a flowline string, a casing string, a production string, a wireline tool, a completion tool, and a drilling tool.

17. The well-gas analysis system of claim 15 , wherein a flushing-mode time duration is defined while the flushing gas is allowed to flow from the flushing-gas inlet to the testing-gas line and a testing-mode time duration is defined while the sample gas is allowed to flow from the sample-gas line to the testing-gas line, and the flushing-mode time duration is shorter than the testing-mode time duration.

18. The well-gas analysis system of claim 17 , wherein the flushing-mode time duration is shorter than 30 seconds and the testing-mode time duration is 30 seconds or longer than 30 seconds.

19. The well-gas analysis system of claim 15 , wherein the flushing-gas inlet includes multiple flushing-gas lines to provide multiple flushing gases.