Sequence Stratigraphy and Architecture of Lower Pennsylvanian Strata, Southern West Virginia: Potential for Carbon Sequestration and Enhanced Coal-Bed Methane Recovery in the Pocahontas Basin
Rouse, William Allan
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Carbon dioxide sequestration in coal-bed methane fields has potential to add significant recoverable reserves and extend the production life of coal-bed methane fields while at the same time providing a geologic sink for atmospheric greenhouse gases. The ability to relate the thickness, extent, and quality of coal seams to their relative position within a sequence is fundamental in determining the sequestration potential of a geologic formation. This thesis documents the carbon dioxide storage capacity and enhanced coalbed methane recovery of lower Pennsylvanian coal-bearing siliciclastic strata within the Bradshaw CBM field, southern McDowell County, WV. Analysis of outcrop, gamma ray and density logs, and eight cross-sections within the study area reveals a hierarchy of bounding discontinuities and architectural elements. Discontinuities are both erosional (unconformable) and depositional (condensed) surfaces of 3rd-order (~2.5 Ma) and 4th-order (~400 k.y.) origin. Architectural elements bound by 4th-order erosional discontinuities consist of upward-fining lowstand and transgressive incised valley fill, alluvial, and estuarine deposits, and upward-coarsening highstand deltaic deposits, representing 4th-order sequences. 4th-order sequences are stacked into composite 3rd-order sequences. Sequence development is attributed to higher frequency (~400 k.y.) 4th-order Milankovitch orbital eccentricity cycles superimposed on lower frequence (~2.5 Ma) orbital eccentricity cycles. Coal seams occur in the transgressive and highstand systems tracts, associated with 4th-order flooding surfaces and high-frequency deltaic autocycles, respectively. Transgressive coal-bed development is attributed to Milankovitch driven glacio-eustacy while highstand coal-bed development is attributed to autocyclic deltaic influences. Assessment of carbon dioxide storage capacity within coals of the lower Pennsylvanian Pocahontas and Bottom Creek formations in the Bradshaw CBM field indicates that 19 million tons of carbon dioxide can be sequestered. Sequestration of carbon dioxide within the Bradshaw CBM field has the potential to increase coal-bed methane recovery by as much as 52 billion cubic feet.
- Masters Theses