Enhanced coal-bed methane production

Patent metadata

Field	Value
Publication number	US-9810050-B2
Application number	US-201214358687-A
Country	US
Kind code	B2
Filing date	Nov 16, 2012
Priority date	Dec 20, 2011
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

Methods and systems for enhanced recovery of coal bed methane. A method includes generating a diluent gas mixture comprising N 2 and CO 2 in a semi-closed Brayton cycle power plant, injecting at least a portion of the diluent gas mixture into a coal bed, and recovering a mixed production gas comprising methane from the coal bed.

First claim

What is claimed is:

1. A method for enhanced recovery of coalbed methane, comprising:
compressing a gaseous fuel for use in a semi-closed Brayton cycle power plant;
generating a gas mixture comprising N 2 and CO 2 in the semi-closed Brayton cycle power plant operating to combust the gaseous fuel and an oxygen component of an oxidant at a stoichiometric ratio;
injecting at least a portion of the gas mixture into a coal bed; and
recovering a mixed production gas comprising methane from the coal bed.

2. The method of claim 1 , comprising completing an injection well in a coal bed.

3. The method of claim 1 , comprising completing a production well in a coal bed.

4. The method of claim 1 , comprising compressing the gas mixture prior to injection.

5. The method of claim 1 , comprising using at least a portion of the mixed production gas to fuel the semi-closed Brayton cycle power plant.

6. The method of claim 1 , comprising recovering heat energy from an exhaust generated by the semi-closed Brayton cycle power plant in a heat recovery steam generator (HRSG).

7. The method of claim 6 , comprising generating power with steam generated in the HRSG.

8. The method of claim 1 , comprising processing the mixed production gas to remove acid gases and water vapor to generate a natural gas capable of transport by pipeline.

9. The method of claim 8 , comprising liquefying the natural gas.

10. The method of claim 1 , comprising cooling the gas mixture prior to injection into the coal bed.

11. The method of claim 10 , comprising recovering heat from the gas mixture to supply process heat to a facility.

12. The method of claim 1 , wherein the oxidant for the semi-closed Brayton cycle power plant is air.

13. The method of claim 1 , wherein the oxidant used in the semi-closed Brayton cycle power plant has an oxygen concentration greater than about 21% by volume.

14. A system for enhancing the recovery of coalbed methane, comprising:
a semi-closed Brayton cycle power plant operating to combust a gaseous fuel and an oxygen component of an oxidant at a stoichiometric ratio, wherein an exhaust gas from the semi-closed Brayton cycle power plant provides a diluent gas mixture comprising substantial amounts of N 2 and CO 2 ;
a compressor configured to compress the gaseous fuel prior to combustion in the semi-closed Brayton cycle power plant;
an injection well configured to inject the diluent gas mixture from the semi-closed Brayton cycle power plant into a coalbed; and
a production well configured to harvest a production gas mixture from the coal bed, wherein the production gas mixture comprises methane.

15. The system of claim 14 , comprising a heat recovery steam generator configured to use an exhaust heat from the semi-closed Brayton cycle power plant to generate steam.

16. The system of claim 15 , comprising a power plant configured to use the steam to generate electricity.

17. The system of claim 14 , comprising a gas separation system configured to generate a CO 2 rich gas stream and a CO 2 lean gas stream.

18. The system of claim 17 , comprising injecting the CO 2 rich gas stream into the coalbed.

19. The system of claim 14 , comprising a liquefied natural gas plant configured to use electricity generated by the semi-closed Brayton cycle power plant to power a liquefaction process.

20. A system for enhancing the recovery of coalbed methane, comprising:
a combustor associated with a gas turbine, the combustor configured to combust therein a gaseous fuel and an oxygen component of an oxidant at a stoichiometric ratio, wherein the gas turbine receives hot exhaust gases from the combustor, wherein cooling is provided by a diluent gas injected into the combustor, and wherein the diluent gas substantially comprises N 2 and CO 2 ;
a generator configured to convert mechanical energy provided by the gas turbine into electrical energy;
a heat recovery steam generator (HRSG) configured to generate steam by heating a boiler with an exhaust stream from the gas turbine;
a Rankine cycle power plant configured to generate electricity from the steam;
a cooler configured to condense water from the exhaust stream downstream of the HRSG, generating the diluent;
a diluent compressor configured to increase the pressure of the diluent and direct at least a portion of the diluent to the combustor;
an injection system configured to inject a portion of the diluent from the compressor into a coalbed;
a production system configured to harvest a production gas from the coalbed, wherein the production gas comprises methane; and
a compressor configured to compress a portion of the production gas to generate a compressed stream of coal bed methane, wherein a portion of the compressed stream of coal bed methane is used as part of the gaseous fuel.

21. The system of claim 20 , comprising a desalination unit integrated into the HRSG that is configured to produce a fresh water stream.

22. The system of claim 20 , comprising a pipeline configured to convey another portion of the compressed stream of coal bed methane to a market.

23. The system of claim 20 , wherein at least a portion of the electricity from the power plant is used to power facilities associated with the production gas.

Assignees

• Sites O Angus
• Bohra Lalit K
• Exxonmobil Upstream Res Co

Inventors

• Sites O Angus
• Bohra Lalit K

Classifications

• F02C3/22

  the fuel or oxidant being gaseous at standard temperature and pressure (F02C3/28 takes precedence) · CPC title

• E21B43/16

  Enhanced recovery methods for obtaining hydrocarbons · CPC title

• E21B43/006 Primary

  Production of coal-bed methane (E21B43/243 takes precedence) · CPC title

• F01K23/10

  with exhaust fluid of one cycle heating the fluid in another cycle (F01K17/025 takes precedence) · CPC title

• F22B1/1815

  using the exhaust gases of gas-turbines · CPC title