Integration of water and gas chemistry in an unconventional Devonian black shale gas reservoir: Microbial vs. thermogenic origin

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:214828

Martini, A M; Budai, J M; Walter, L M ^[1]

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1. Univ. of Michigan, Ann Arbor, MI (United States); and others

The upper Devonian Antrim Shale is a self-sourced, fractured gas reservoir that has been the target of intensive exploitation around the margin of the Michigan Basin. Significant amounts of water are commonly produced with methane in regions adjacent to subcrop of the Antrim Shale. Chemical and isotopic properties measured in the formation waters show significant regional variations and probably delineate zones of increased flow controlled by the fracture network within the Antrim Shale. The isotopic composition of Antrim methane ({gamma}{sup 13}C = -49 to -59{per_thousand}) was used to suggest that the gas is of thermtogenic origin. However, the highly {sup 13}C-enriched carbon of co-produced CO{sub 2} gas ({gamma}{sup 13}C {approx} +22{per_thousand}) and DIC in associated Antrim brines ({gamma}{sup 13}C = +19 to +31{per_thousand}) are consistent with bacterially mediated fractionation. Deuterium values in the methane ({gamma}D = -200 to -260{per_thousand}) also support a bacterial origin for methane. Preliminary correlation of deuterium in methane with that of the Antrim waters implies that methane is being generated via CO{sub 2} reduction within the reservoir.

• OSTI ID: 214828
• Report Number(s): CONF-950801--
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
04 OIL SHALES AND TAR SANDS
BLACK SHALES
BRINES
DEUTERIUM
FRACTIONATION
FRACTURED RESERVOIRS
ISOTOPE RATIO
METHANE
ORIGIN
SHALE GAS