Method and apparatus for handling acid gases generated by pyrolysis of kerogen

Abstract

In some embodiments, a pyrolysis method comprises: a. heating kerogen or bitumen to initiate pyrolysis so that a stream of pyrolysis formation gases is recovered via production wells or production conduits; b. monitoring or estimating a concentration of acid gas within the gas stream; c. contingent upon an acid gas concentration being below a threshold value, subjecting pyrolysis gases of the stream to sequestration; and d. responding to an estimated or monitored increase in acid gas concentration of the gas stream by performing at least one of: i. subjecting a greater fraction of the stream to an acid gas separation process and/or acid gas elimination process; and ii. subjecting a lesser fraction of the stream to a sequestration. The presently disclosed teachings are applicable both to in situ pyrolysis and to pyrolysis performed within an enclosure such as a pit.

What is claimed is: 
     
         1 . A pyrolysis method comprising:
 a. heating a hydrocarbon-containing subsurface formation in situ so as to initiate pyrolysis of kerogen and/or bitumen therein so that a stream of pyrolysis formation gases is recovered via production wells;   b. monitoring or estimating a concentration of acid gas within the gas stream;   c. contingent upon an acid gas concentration being below a threshold value, subjecting pyrolysis gases of the stream to sequestration; and   d. responding to an estimated or monitored increase in acid gas concentration of the gas stream by carrying at least one of:
 i. subjecting a greater fraction of the stream to an acid gas separation process and/or acid gas elimination process; and 
 ii. subjecting a lesser fraction of the stream to a sequestration. 
   
     
     
         2 . A pyrolysis method comprising:
 a. heating a hydrocarbon-containing subsurface formation in situ so as to initiate pyrolysis of kerogen and/or bitumen therein thereby generating pyrolysis formation gases so that:
 i. early pyrolysis gases formed during early pyrolysis are acid-gas rich and have at most low concentrations of the combination of hydrogen gas and hydrocarbon gases; 
 ii. a concentration of acid gases within later pyrolysis gases formed during later stages of pyrolysis is significantly less than the concentration within the early pyrolysis gases; and 
 iii. the later pyrolysis gases are rich in hydrocarbon gases and/or hydrogen gas; 
   b. sequestering the early pyrolysis gases; and   c. subjecting the later pyrolysis gases to an acid gas separation process and/or to an acid gas elimination process.   
     
     
         3 . A pyrolysis method comprising:
 a. heating a hydrocarbon-containing subsurface formation in situ by heaters so as to initiate pyrolysis of kerogen and/or bitumen therein;   b. operating the heaters so as to maximize the quantity of acid formation gases that are formed as part of a gas mixture having at most low concentrations of the combination of hydrogen gas and hydrocarbon gases; and   c. sequestering the acid gases.   
     
     
         4 . A pyrolysis method comprising:
 a. heating a hydrocarbon-containing subsurface formation in situ by heaters so as to initiate pyrolysis of kerogen and/or bitumen therein;   b. operating the heaters so as to maximize the quantity of acid formation gases that are formed when a bulk temperature of the pyrolyzed portion of the formation is at most 300 degrees Celsius or at most 295 degrees Celsius or at most 290 degrees Celsius; and   c. sequestering the acid gases.   
     
     
         5 . A pyrolysis method comprising:
 a. heating a hydrocarbon-containing subsurface formation in situ by heaters so as to initiate pyrolysis of kerogen and/or bitumen therein;   b. monitoring or estimating content of a gas mixture stream of formation gases formed by the pyrolysis to determine an indication of an acid gas concentration thereof; and   c. during an early stage of pyrolysis of the portion of the formation, operating the heater(s) at a power level determined in accordance with the acid gas concentration.   
     
     
         6 . The method of any preceding claim wherein the heaters are subsurface heaters. 
     
     
         7 . A pyrolysis method comprising:
 a. introducing hydrocarbon-containing rocks into an interior region of an enclosure to form a bed of rocks therein;   b. heating the bed of rocks so as to pyrolyze kerogen or bitumen thereof so that a stream of pyrolysis formation gases is recovered via production conduit(s);   c. monitoring or estimating a concentration of acid gas within the gas stream;   d. contingent upon an acid gas concentration being below a threshold value, subjecting pyrolysis gases of the stream to sequestration; and   d. responding to an estimated or monitored increase in acid gas concentration of the gas stream by carrying at least one of:
 i. subjecting a greater fraction of the stream to an acid gas separation process and/or acid gas elimination process; and 
 ii. subjecting a lesser fraction of the stream to a sequestration. 
   
     
     
         8 . A pyrolysis method comprising:
 a. introducing hydrocarbon-containing rocks into an interior region of an enclosure to form a bed of rocks therein;   b. heating the bed of rocks so as to initiate pyrolysis of kerogen and/or bitumen therein thereby generating pyrolysis formation gases so that:
 i. early pyrolysis gases formed during early pyrolysis are acid-gas rich and have at most low concentrations of the combination of hydrogen gas and hydrocarbon gases; 
 ii. a concentration of acid gases within later pyrolysis gases formed during later stages of pyrolysis is significantly less than the concentration within the early pyrolysis gases; and 
 iii. the later pyrolysis gases are rich in hydrocarbon gases and/or hydrogen gas; 
   b. sequestering the early pyrolysis gases; and   c. subjecting the later pyrolysis gases to an acid gas separation process and/or acid gas elimination process   
     
     
         9 . A pyrolysis method comprising:
 a. introducing hydrocarbon-containing rocks into an interior region of an enclosure to form a bed of rocks therein;   b. heating the bed of rocks by heaters so as to pyrolyze kerogen or bitumen thereof so as to initiate pyrolysis of kerogen and/or bitumen thereof;   c. operating the heaters so as to maximize the quantity of acid formation gases that are formed as part of a gas mixture having at most low concentrations of the combination of hydrogen gas and hydrocarbon gases; and   d. sequestering the acid gases.   
     
     
         10 . A pyrolysis method comprising:
 a. introducing hydrocarbon-containing rocks into an interior region of an enclosure to form a bed of rocks therein;   b. heating the bed of rocks by heaters so as to pyrolyze kerogen or bitumen thereof so as to initiate pyrolysis of kerogen and/or bitumen thereof;   c. operating the heaters so as to maximize the quantity of acid formation gases that are formed when a bulk temperature of the pyrolyzed portion of the formation is at most 300 degrees Celsius or at most 295 degrees Celsius or at most 290 degrees Celsius; and   d. sequestering the acid gases.   
     
     
         11 . A pyrolysis method comprising:
 a. introducing hydrocarbon-containing rocks into an interior region of an enclosure to form a bed of rocks therein;   b. heating the bed of rocks by heaters so as to pyrolyze kerogen or bitumen thereof so as to initiate pyrolysis of kerogen and/or bitumen thereof;   c. monitoring or estimating content of a gas mixture stream of formation gases formed by the pyrolysis to determine an indication of an acid gas concentration thereof; and   d. during an early stage of pyrolysis of the portion of the formation, operating the heater(s) at a power level determined in accordance with the acid gas concentration.   
     
     
         12 . The method of any of  claims 7 - 11  wherein the interior region is maintained under anoxic conditions during the heating. 
     
     
         13 . The method of any of  claims 7 - 12  wherein the enclosure is an excavated enclosure. 
     
     
         14 . The method of any of  claims 7 - 12  any previous claim wherein the enclosure is a pit or an impoundment. 
     
     
         15 . The method of any preceding claim wherein the sequestration is subsurface sequestration, for example, deep well sequestration. 
     
     
         16 . The method of any preceding claim wherein the sequestration is subsurface sequestration, for example, deep well sequestration in a well-confined saline aquifer gas cap. 
     
     
         17 . The method of any preceding claim wherein the acid gas threshold value is between 70% and 95%, 
     
     
         18 . The method of any preceding claim wherein the acid gas threshold value is least 85% and/or at most 90%. 
     
     
         19 . The method of any preceding claim wherein the sequestration is carried out immediately. 
     
     
         20 . The method of any preceding claim wherein the sequestration is carried out at a much later time. 
     
     
         21 . The method of any preceding claim wherein the subsurface formation is an oil shale formation or a coal formation or a bitumen formation. 
     
     
         22 . The method of any preceding claim wherein the kerogen is type IIs kerogen or the bitumen is derived from type IIs kerogen. 
     
     
         23 . The method of any preceding claim wherein the kerogen is sulfur-rich type IIs kerogen or the bitumen is derived from sulfur-rich type IIs kerogen. 
     
     
         24 . The method of any preceding claim wherein the acid gas separation process is carried out in an amine unit. 
     
     
         25 . The method of any preceding claim wherein the acid gas elimination process is carried out in a caustic system, for example, based upon sodium hydroxide or potassium hydroxide.