Enhanced coal-bed methane production
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.
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.