Two-pass method for developing a system of in situ oil shale retorts

A two-pass method for developing a system of in situ oil shale retorts formed in a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale;

• in which a first set of in situ oil shale retorts has been formed in a first pass through the subterranean formation containing oil shale;
• in which an intervening zone of unfragmented formation separates adjacent in situ oil shale retorts within the first set;
• and in which a first gas level drift system communicates with fragmented masses of such adjacent in situ retorts within the first set;
• the method comprising the steps of:
• forming one or more intervening in situ oil shale retorts in such an intervening zone of unfragmented formation during a second pass through the subterranean formation containing oil shale;
• and
• forming a second gas level drift system that communicates with the fragmented mass of such an intervening in situ retort, the second gas level drift system being isolated from the first gas level drift system for preventing gas flow between the first gas level drift system and the second gas level drift system.

A system of in situ oil shale retorts formed in a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale, the system comprising:

• a first set of in situ oil shale retorts formed in the subterranean formation containing oil shale, such a first set of retorts including separate spaced apart rows of retorts;
• an intervening zone of unfragmented formation separating at least one row of retorts within the first set from an adjacent row of retorts within the first set;
• at least one row of intervening in situ oil shale retorts formed in the intervening zone of unfragmented formation between such adjacent rows of in situ oil shale retorts within the first set;
• a first gas level drift system in gas communication with fragmented masses of such adjacent rows of in situ oil shale retorts within the first set;
• and
• a second gas level drift system in gas communication with fragmented masses of such an intervening row of in situ retorts, the second gas level drift system being at a different elevation from the elevation of the first gas level drift system and being isolated from the first gas level drift system by a barrier of unfragmented formation for preventing gas flow between the first gas level drift system and the second gas level drift system.

A system of in situ oil shale retorts formed in a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale, the in situ retort system comprising:

• a first set of in situ oil shale retorts formed in the subterranean formation containing oil shale, the in situ retorts in the first set including separate groups of in situ retorts which are horizontally spaced apart from one another in the subterranean formation containing oil shale;
• a plurality of intervening zones of unfragmented formation, each intervening zone being between a pair of adjacent groups of in situ retorts within the first set;
• a second set of in situ oil shale retorts formed in the subterranean formation containing oil shale, the in situ retorts in the second set including separate groups of in situ retorts which are formed in corresponding intervening zones of unfragmented formation between adjacent groups of in situ retorts within the first set;
• a first production level drift communicating with fragmented masses of the in situ retorts in each group of in situ retorts within the first set;
• a second production level drift communicating with fragmented masses of the in situ retorts in each group of in situ retorts within the second set;
• a first gas level main drift communication with the first production level drifts for the groups of in situ retorts within the first set;
• a second gas level main drift communicating with the second production level drifts for the groups of in situ retorts within the second set;
• and
• one or more barriers of unfragmented formation for preventing gas flow from the first gas level main drift and the first production level drifts to the second gas level main drift and the second production level drifts, and vice versa.

A two-pass method for developing a system of in situ oil shale retorts formed in a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale;

• in which a first set of in situ oil shale retorts has been formed in a first pass through the subterranean formation containing oil shale;
• in which an intervening zone of unfragmented formation separates each adjacent group of the in situ oil shale retorts within the first set;
• in which a first gas level drift system communicates with fragmented masses of the groups of in situ oil shale retorts within the first set;
• and in which retorting operations have been commenced in fragmented masses within at least a portion of the in situ oil shale retorts within the first set for producing liquid and gaseous products of retorting and leaving spent in situ retorts, the method comprising the steps of:
• forming a second set of in situ oil shale retorts in such an intervening zone of unfragmented formation during a second pass through the subterranean formation containing oil shale, such a second set of in situ oil shale retorts being formed in the intervening zone of unfragmented formation between adjacent groups of spent in situ oil shale retorts within such a first set of in situ retorts;
• and
• forming a second gas level drift system that communicates with fragmented masses in the second set of in situ retorts, the second gas level drift system being isolated from the first gas level drift system for preventing gas flow between the first gas level drift system and the second gas level drift system.

A two-pass method for recovering liquid and gaseous products from an in situ oil shale retort system formed in a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale, the method comprising the steps of:

• in a first pass,
• forming spaced apart rows of in situ oil shale retorts in the subterranean formation containing oil shale, adjacent rows of in situ oil shale retorts being separated by an intervening zone of unfragmented formation;
• forming a first gas level drift system in fluid communication with fragmented masses of the rows of in situ retorts formed in the first pass;
• conducting retorting operations in fragmented masses of the in situ retorts formed in the first pass for producing liquid and gaseous products of retorting;
• withdrawing gaseous products of retorting from the in situ retorts formed in the first pass through the first gas level drift system;
• and in a second pass,
• forming one or more rows of in situ oil shale retorts in such an intervening zone of unfragmented formation, formation of at least a portion of the in situ retorts in the second pass being commenced after commencement of retorting operations in the in situ retorts formed in the first pass;
• forming a second gas level drift system in fluid communication with fragmented masses of such in situ retorts formed in the second pass, leaving sufficient barriers of unfragmented formation between the first and second gas level drift systems to prevent gas communication between the two gas level drift systems;
• conducting retorting operations in fragmented masses within the groups of in situ retorts formed in the second pass for producing liquid and gaseous products of retorting;
• and
• withdrawing gaseous products of retorting from such a group of in situ retorts formed in the second pass through the second gas level drift system.

A two-pass method for developing an in situ oil shale retort system, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale, the method comprising the steps of:

• forming spaced apart groups of in situ oil shale retorts during a first pass through the subterranean formation containing oil shale, leaving intervening barrier pillars of unfragmented formation between adjacent groups of in situ retorts formed during the first pass;
• forming a first gas level drift system communicating with in situ retorts formed during the first pass;
• conducting retorting operations in at least a portion of the in situ retorts formed during the first pass and withdrawing off gas to the first gas level drift system from such in situ retorts formed during the first pass;
• thereafter, during a second pass of retorting, forming intervening groups of in situ oil shale retorts in the intervening barrier pillars between the groups of in situ retorts formed during the first pass;
• and
• forming a second gas level drift system communicating with the in situ retorts formed during the second pass, the second gas level drift system being formed at a different level and being isolated from the first gas level drift system for inhibiting gas flow from the first gas level drift system to the second gas level drift system.

A two-pass method for recovering liquid and gaseous products from an in situ oil shale retort system formed in a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale, the method comprising the steps of:

• in a first pass,
• forming spaced apart rows of in situ oil shale retorts in the subterranean formation containing oil shale, adjacent rows of such in situ retorts being separated by an intervening zone of unfragmented formation;
• forming a first gas level drift system in fluid communication with the fragmented masses in the rows of in situ retorts formed in the first pass;
• conducting retorting operations in fragmented masses of the in situ retorts formed in the first pass for producing liquid and gaseous products of retorting;
• withdrawing gaseous products of retorting from the in situ retorts formed in the first pass through the first gas level drift system;
• and in a second pass,
• forming one or more rows of in situ oil shale retorts in such an intervening zone of unfragmented formation, formation of at least a portion of the in situ retorts in the second pass being commenced after completion of retorting operations in adjacent rows of in situ retorts formed in the first pass;
• forming a second gas level drift system in fluid communication with the fragmented masses of such in situ retorts formed in the second pass, leaving sufficient barriers of unfragmented formation between the first and second gas level drift systems to prevent gas communication between the two gas level drift systems;
• conducting retorting operations in fragmented masses within the groups of in situ retorts formed in the second pass for producing liquid and gaseous products of retorting;
• and
• withdrawing gaseous products of retorting from such a group of in situ retorts formed in the second pass through the second gas level drift system.

A method for producing liquid and gaseous products of oil shale retorting from a tract having a subterranean formation containing oil shale, comprising the steps of:

• forming and processing a first set of in situ oil shale retorts in the formation in a first pass across the tract for producing liquid and gaseous products of retorting, such retorts in the first set being in rows leaving a barrier pillar of unfragmented formation between at least a portion of such rows;
• withdrawing off gas containing such gaseous products from such retorts in the first set by way of a first gas level drift system during such processing;
• forming and processing a second set of in situ oil shale retorts in a second pass across the tract for producing liquid and gaseous products of retorting, such retorts in the second set being in rows in the barrier pillars between rows of retorts in the first set;
• and
• withdrawing off gas containing such gaseous products from such retorts in the second set by way of a second gas level drift system during such processing, the second gas level drift system being sufficiently isolated from the first gas level drift system to prevent gas flow between the two gas level drift systems.

A system of in situ oil shale retorts formed in a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale, the in situ retort system comprising:

• a first set of in situ oil shale retorts formed in the subterranean formation in spaced apart rows;
• a second set of in situ oil shale retorts formed in the subterranean formation in rows interleaved with the rows of in situ retorts of the first set;
• a first gas level drift system connected to retorts in the first set for withdrawing off gas from each row of such retorts in the first set to a first gas level main drift;
• a second gas level drift system connected to retorts in the second set for withdrawing off gas from each row of such retorts in the second set to a second gas level main drift;
• and
• at least one barrier of unfragmented formation for isolating the second gas level drift system and the second gas level main drift from the first gas level drift system and the first gas level main drift for preventing gas flow between the two gas level drift systems and the two gas level main drifts.

A system of in situ oil shale retorts formed in a subterranean formation containing oil shale, such an in situ oil shale retort containing a fragmented permeable mass of formation particles containing oil shale, the in situ retort system comprising:

• a first row of spent in situ oil shale retorts;
• a second row of spent in situ oil shale retorts spaced apart from the first row by an intervening zone of unfragmented formation;
• a first gas level drift in gas communication with retorts in the first and second rows of spent in situ oil shale retorts;
• a third row of in situ oil shale retorts in the intervening zone of unfragmented formation;
• and
• a second gas level drift in gas communication with retorts in the third row for withdrawing off gas from such retorts in the third row, the second gas level drift being at an elevation different from the elevation of the first gas level drift and being sufficiently isolated from the first gas level drift by a barrier of unfragmented formation for preventing gas flow between the two gas level drifts.