Generation and expulsion of petroleum and gas from Almond Formation Coal, Greater Green River Basin, Wyoming
Journal Article
·
· AAPG Bulletin
OSTI ID:433073
- Universidad industrial de Santander, Bucaramanga (Colombia)
- Univ. of Wyoming, Laramie, WY (United States)
- Bringham Young Univ., Provo, UT (United States)
Petrographic and geochemical studies of coal from the Almond Formation in the Greater Green River basin demonstrate that the coal contains important volumes of stored liquid petroleum, as well as methane. Modeling indicates that at the basin center, most of the oil generated in the coal has been thermally cracked to gas, whereas at the basin flank the oil-to-gas reaction has barely proceeded. Several new concepts are presented about the mechanism of petroleum generation in coal based on (1) natural maturation trends gleaned form examination of Almond coal samples from different burial depths and (2) similar maturation trends observed in hydrous pyrolysis experiments using immature Almond coal samples. These new concepts show that the oil in the coal was generated during the alteration of desmocollinite and liptinite macerals to exsudatinite (waxy oil) and inertinite solid residue; that the waxy oil was initially stored in porous structures and subsequently in vesicles as the coal matured under increasing temperature; that primary migration of the oil occurred as the generation of a sufficient volume of exsudatinite microfractured the vitrinite-semifusinite vesicles, interconnecting vesicles and pores; and that the thermal cracking of exsudatinite generated a sufficient volume of gas to fracture the vesiculated coal as pore pressure increased and allowed migration of hydrocarbons out of the coal.
- OSTI ID:
- 433073
- Journal Information:
- AAPG Bulletin, Journal Name: AAPG Bulletin Journal Issue: 1 Vol. 81; ISSN 0149-1423; ISSN AABUD2
- Country of Publication:
- United States
- Language:
- English
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