# US 8,146,664 B2 · Utilization of low BTU gas generated during in situ heating of organic-rich rock > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,146,664 B2 - Document ID: US8146664B2 - Status: Granted - Kind: B2 - Application number: 12/154,256 - Filed: 2008-05-21 - Published: 2008-11-27 - Granted: 2012-04-03 - Earliest claimed: 2007-05-25 - Assignees: ExxonMobil Upstream Research Company - Inventors: Robert D. Kaminsky; C. Stan Speed; Todd S. Griffith; Loren K. Starcher; William A. Symington - Web page: https://patentgrep.com/patent/US8146664B2 ## CPC - F02C 3/20: using a special fuel, oxidant, or dilution fluid to generate the combustion products - C01B 3/24: of hydrocarbons - C01B 3/34: by reaction of hydrocarbons with gasifying agents - C10L 3/10: Working-up natural gas or synthetic natural gas - C10L 3/102: {of acid contaminants} - E21B 43/24: using heat, e.g. steam injection - F05D 2220/75: equipment using fuel having a low calorific value, e.g. low BTU fuel, waste end, syngas, biomass fuel or flare gas - F24T 10/20: using underground water as working fluid; using working fluid injected directly into the ground, e.g. using injection wells and recovery wells - Y02E 10/10: Geothermal energy - Y02E 20/16: Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT] - Y02P 20/129: Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines - F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00) - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - C10L: FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS - F24T: GEOTHERMAL COLLECTORS; GEOTHERMAL SYSTEMS - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract A method for utilizing gas produced from an in situ conversion process includes heating an organic-rich rock formation, for example an oil shale formation. The method may include producing a production fluid from the organic-rich rock formation where the production fluid has been at least partially generated as a result of pyrolysis of formation hydrocarbons located in the organic-rich rock formation. The method may include obtaining a gas stream from the production fluid, where the gas stream comprises combustible hydrocarbon fluids. The method may include separating the gas stream into a first composition gas stream and a second composition gas stream, where the composition of the first composition gas stream is a low BTU gas stream maintained in a substantially constant condition and passing the first composition gas stream through a gas turbine to form a gas turbine exhaust stream, where the gas turbine is connected to an electrical generator. ## Claims ### Claim 1 A method for utilizing gas produced from an in situ conversion process, comprising: a) heating an organic-rich rock formation in situ, wherein the organic-rich rock formation is an oil shale formation; b) producing a production fluid from the organic-rich rock formation, the production fluid having been at least partially generated as a result of pyrolysis of formation hydrocarbons located in the organic-rich rock formation, the production fluid comprising hydrocarbon fluids; c) obtaining a gas stream from the production fluid, the gas stream comprising a combustible hydrocarbon fluid; d) separating the gas stream into a first composition gas stream and a second composition gas stream, wherein a composition of the first gas stream is maintained in a substantially constant condition, the first composition gas stream comprises methane and at least one inert gas and the first composition gas stream has a lower heating value less than 800 BTU/SCF; and e) passing the first composition gas stream through a first gas turbine to form a first gas turbine exhaust stream, the first gas turbine being configured to provide energy to a first electrical generator; f) feeding the second composition gas stream to a steam boiler; g) combusting the second composition gas stream to provide heat to the steam boiler; h) producing steam in the steam boiler; and i) passing the steam through a steam turbine to form a steam turbine exhaust stream, wherein the steam turbine is configured to provide energy to a second electrical generator, the steam turbine thereby providing energy to the second electrical generator. ### Claim 2 (depends on 1) The method of claim 1, wherein the first composition gas stream and the second composition gas stream both contain a hydrocarbon fluid. ### Claim 3 (depends on 1) The method of claim 1, wherein both the first composition gas stream and the second composition gas stream comprise combustible gases. ### Claim 4 (depends on 1) The method of claim 1, wherein the first composition gas stream and the second composition gas stream both have a lower heating value greater than 200 BTU/SCF. ### Claim 5 (depends on 4) The method of claim 4, wherein the first composition gas stream has a lower heating value less than 700 BTU/SCF. ### Claim 6 (depends on 1) The method of claim 1, wherein the first composition gas stream is greater than 15 mole percent methane. ### Claim 7 (depends on 1) The method of claim 1, wherein a CO2 content of the first composition gas stream is greater than 30 mole percent. ### Claim 8 (depends on 1) The method of claim 1, wherein the first composition gas stream has a substantially constant H2 to CO2 molar ratio. ### Claim 9 (depends on 8) The method of claim 8, wherein the first composition gas stream has an H2 to CO2 molar ratio between 0.1 to 2.0. ### Claim 10 (depends on 1) The method of claim 1, wherein the first composition gas stream has a substantially constant ethane to CO2 molar ratio. ### Claim 11 (depends on 1) The method of claim 1, wherein the steam boiler is a supercritical boiler. ### Claim 12 (depends on 1) The method of claim 1, wherein the steam boiler is equipped with catalytic combustors. ### Claim 13 (depends on 1) The method of claim 1, wherein at least a portion of the steam is delivered to the organic-rich rock formation. ### Claim 14 (depends on 1) The method of claim 1, wherein the first composition gas stream is greater than 90 mole percent hydrogen. ### Claim 15 (depends on 1) The method of claim 1, wherein the second composition gas stream is greater than 90 mole percent hydrogen. ### Claim 16 (depends on 1) The method of claim 1, wherein a Wobbe Index of the first composition gas stream on an averaged daily basis varies by less than 15 percent over a 7 day period. ### Claim 17 (depends on 1) The method of claim 1, wherein a total concentration of inert gas in the first composition gas stream on an averaged daily basis varies by less than 10 mole percent over a 7 day period. ### Claim 18 (depends on 1) The method of claim 1, wherein a concentration of CO2 in the first composition gas stream on an averaged daily basis varies by less than 10 mole percent over a 7 day period. ### Claim 19 (depends on 1) The method of claim 1, wherein a concentration of methane in the first composition gas stream on an averaged daily basis varies by less than 10 mole percent over a 7 day period. ### Claim 20 (depends on 1) The method of claim 1, wherein the lower heating value of the first composition gas stream on an averaged daily basis varies by less than 10 percent over a 7 day period. ### Claim 21 (depends on 1) The method of claim 1, wherein a concentration of ethane in the first composition gas stream on an averaged daily basis varies by less than 10 mole percent over a 7 day period. ### Claim 22 (depends on 1) The method of claim 1, wherein a composition of the second composition gas stream is also maintained in a substantially constant condition. ### Claim 23 A method for utilizing gas produced from an in situ conversion process, comprising: a) heating an organic-rich rock formation in situ, wherein the organic-rich rock formation is an oil shale formation; b) producing a production fluid from the organic-rich rock formation, the production fluid having been at least partially generated as a result of pyrolysis of formation hydrocarbons located in the organic-rich rock formation, the production fluid comprising hydrocarbon fluids; c) obtaining a gas stream from the production fluid, the gas stream comprising a combustible hydrocarbon fluid; d) separating the gas stream into a first composition gas stream and a second composition gas stream, wherein a composition of the first gas stream is maintained in a substantially constant condition, the first composition gas stream comprises methane and at least one inert gas and the first composition gas stream has a lower heating value less than 800 BTU/SCF; e) passing the first composition gas stream through a first gas turbine to form a first gas turbine exhaust stream, the first gas turbine being configured to provide energy to a first electrical generator; f) monitoring the first composition gas stream for one or more properties; and g) altering the composition of the first composition gas stream, thereby controlling one or more operating parameters of the first composition gas stream, wherein the first composition gas stream includes methane and wherein altering the composition of the first composition gas stream comprises reforming at least a portion of the methane in the first composition gas stream to generate hydrogen. ### Claim 24 (depends on 23) The method of claim 23, wherein the one or more properties is selected from gas composition, temperature, heating value, specific gravity, Wobbe index, Modified Wobbe Index, dew point, flammability limit, flame velocity, and combinations thereof. ### Claim 25 (depends on 23) The method of claim 23, wherein the operating parameter is a concentration of one or more C2 and higher hydrocarbons, C3 and higher hydrocarbons, carbon dioxide, inert gases, hydrogen gas, ethane, ethylene, propane, and combinations thereof. ### Claim 26 (depends on 23) The method of claim 23, wherein altering the composition of the first composition gas stream includes blending a blend gas stream with the first composition gas stream. ### Claim 27 (depends on 23) The method of claim 23, wherein at least a portion of the methane is removed from the first composition gas stream prior to the reforming, the removed methane is reformed, thereby generating the hydrogen, and the generated hydrogen is returned to the first composition gas stream prior to passing the first composition gas stream to the first gas turbine. ### Claim 28 (depends on 23) The method of claim 23, wherein at least a portion of the methane is reformed while in the first composition gas stream, thereby generating the hydrogen in the first composition gas stream from at least a portion of the methane present in the first composition gas stream. ### Claim 29 (depends on 23) The method of claim 23, wherein the portion of the methane reformed into hydrogen is controlled to maintain a substantially constant Wobbe Index value over time. ### Claim 30 (depends on 29) The method of claim 29, further comprising: h) selling generated electricity from the first electrical generator to a third party. ### Claim 31 (depends on 30) The method of claim 30, further comprising: i) buying electricity from an electricity supplier at selected off-peak demand times. ### Claim 32 (depends on 23) The method of claim 23, wherein the first composition gas stream includes inert gas and wherein altering the composition of the first composition gas stream includes adjusting the inert gas content of the first composition gas stream to maintain a substantially constant Wobbe Index value over time. ### Claim 33 (depends on 23) The method of claim 23, wherein altering the composition of the first composition gas stream includes adjusting a pressure or temperature of one or more oil-gas separators. ### Claim 34 (depends on 23) The method of claim 23, wherein altering the composition of the first composition gas stream comprises adding hydrogen, ethane, ethylene, or combinations thereof, thereby increasing a flame speed of the first composition gas stream, adjusting a burn rate of the first composition gas stream, stabilizing combustion in the first gas turbine, or combinations thereof. ### Claim 35 (depends on 23) The method of claim 23, further comprising: h) adjusting a temperature of the first composition gas stream, thereby adjusting a Wobbe Index of the first composition gas stream. ### Claim 36 (depends on 23) The method of claim 23, wherein a composition of the second composition gas stream is also maintained in a substantially constant condition. ### Claim 37 (depends on 36) The method of claim 36, further comprising: h) passing the second composition gas stream through a second gas turbine to form a second gas turbine exhaust stream, the second gas turbine being configured to provide energy to a second electrical generator. ### Claim 38 (depends on 23) The method of claim 23, wherein altering the composition of the first composition gas stream comprises reducing an inert gas content of the first composition gas stream and the first gas turbine is equipped with lean pre-mixed combustor(s), Dry Low NOx (DLN) combustor(s), or Dry Low Emissions (DLE) combustor(s). ### Claim 39 (depends on 23) The method of claim 23, wherein altering the composition of the first composition gas stream comprises increasing an inert gas content of the first composition gas stream, thereby reducing NOx generation in the first gas turbine. ### Claim 40 (depends on 39) The method of claim 39, wherein the inert gas content of the first composition gas stream is increased by increasing a CO2 content of the first composition gas stream. ### Claim 41 (depends on 23) The method of claim 23, wherein a Wobbe Index of the first composition gas stream on an averaged daily basis varies by less than 15 percent over a 7 day period. ### Claim 42 (depends on 23) The method of claim 23, wherein a total concentration of inert gas in the first gas composition gas stream on an averaged daily basis varies by less than 10 mole percent over a 7 day period. ### Claim 43 (depends on 23) The method of claim 23, wherein a concentration of CO2 in the first composition gas stream on an averaged daily basis varies by less than 10 mole percent over a 7 day period. ### Claim 44 (depends on 23) The method of claim 23, wherein a concentration of methane in the first composition gas stream on an averaged daily basis varies by less than 10 mole percent over a 7 day period. ### Claim 45 (depends on 23) The method of claim 23, wherein the lower heating value of the first composition gas stream on an averaged daily basis varies by less than 10 percent over a 7 day period. ### Claim 46 (depends on 23) The method of claim 23, wherein a concentration of ethane in the first composition gas stream on an averaged daily basis varies by less than 10 mole percent over a 7 day period. ### Claim 47 A method for utilizing gas produced from an in situ conversion process, comprising: a) heating an organic-rich rock formation in situ, wherein the organic-rich rock formation is an oil shale formation; b) producing a production fluid from the organic-rich rock formation, the production fluid having been at least partially generated as a result of pyrolysis of formation hydrocarbons located in the organic-rich rock formation, the production fluid comprising hydrocarbon fluids; c) obtaining a gas stream from the production fluid, the gas stream comprising a combustible hydrocarbon fluid; d) separating the gas stream into a first composition gas stream and a second composition gas stream, wherein a composition of the first gas stream is maintained in a substantially constant condition, the first composition gas stream comprises methane and at least one inert gas and the first composition gas stream has a lower heating value less than 800 BTU/SCF; e) passing the first composition gas stream through a first gas turbine to form a first gas turbine exhaust stream, the first gas turbine being configured to provide energy to a first electrical generator; f) separating NH3 from the production fluid to form an NH3 treatment stream; and g) injecting the NH3 into the first gas turbine exhaust stream, thereby converting a portion of NOx components in the first gas turbine exhaust stream to N2.