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Deep Gas Potential in Wyoming

Ronald C. Surdam and Zun Sheng. Wyoming State Geological Survey, P.O. Box 1347, Laramie, WY 82073, phone: 307 766 2286, fax: 307 766 2605, [email protected]

The National Energy Technology Laboratory estimates that there is a huge natural gas resource (>1000 tef) in Wyoming at depths greater than 15,000 ft depth. The key question is with current technology how much of this gas can be converted to energy reserves? The answer to this question is predicated on the accomplishment of 2 tasks. The first task is to detect gas distribution at depths greater than 15, 000 ft. The second task is to delineate commercial porosity/permeability at depths greater than 15,000 ft.

The first task can be accomplished by combining detailed velocity analyses with hydrocarbon maturation modeling. The second task can be accomplished by diagenetic modeling based on burial history, thermal evolution, and reaction kinetics.

Work on deep gas accumulations has shown that significant commercial porosity/permeability can occur at depths >20,000 ft. These deep high porosity/permeability domains result from the convergence of critical determinative elements.

The convergence of these critical elements can be modeled with the following reactions:

1) CaS04 + CH4 ® CaCO3 + H2S + H2O CaS04 + 3H2S + CO2 ® CaC03 + 4So + 3H2O

2) Fe+3 + 0.5So + 1.5H2S ® FeS2 + 3H+ Fe+2 + So + H2S ® FeS2 + 2H+

3) CaC03 + 2H+ ® Ca+2 + H2O + CO2

The Mesozoic and Paleozoic stratigraphic sections, plus structural settings in Wyoming provide an ideal framework for the convergence of the geologic elements required for deep commercial gas accumulations.