21: Evidence of Fault–Fracture “Hydrothermal” Reservoirs in the Southern Midcontinent Mississippian Carbonates
Published:January 01, 2019
Priyank Jaiswal, Jay M. Gregg, Shawna Parks, Robert Holman, Sahar Mohammadi, G. Michael Grammer, 2019. "Evidence of Fault–Fracture “Hydrothermal” Reservoirs in the Southern Midcontinent Mississippian Carbonates", Mississippian Reservoirs of the Midcontinent, G. Michael Grammer, Jay M. Gregg, James Puckette, Priyank Jaiswal, S. J. Mazzullo, Matthew J. Pranter, Robert H. Goldstein
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Fault–fracture related “hydrothermal” carbonate reservoirs such as Albion–Scipio (Michigan) are prolific hydrocarbon reservoirs producing mainly from secondary porosity formed through hydrothermal leaching and brecciation by warm (~60°C–150°C) basinal brines. This paper, for the first time, shows that hydrothermal reservoirs may exist in the Mississippian age limestones (“Miss Lime”) of the southern midcontinent. The chapter is pivoted on the observation of a structural depression in a 3-D seismic volume from Payne County in north-central Oklahoma. The depression involves Pennsylvanian to Ordovician (and possibly deeper) units and is fully enclosed by normal faults. Overall, the fault-bounded depression appears to be a negative flower structure with its main fault extending into the basement providing a path for fluids to flow into the flower structure. Fluid inclusion studies on nearby calcite cements suggest that high-temperature brines, likely sourced from the deeper Ordovician–basement rock, have invaded the larger study area. Multiattribute inversion suggests presence of high porosity (>10%) zones in the Miss Lime depression, but confirmation of brecciation and leaching requires further studies. Nonetheless, the paper posits that several elements of a viable fault–fracture-type play are visible in the Miss Lime depression and recommends that the concept be tested along other regional basement involved faults.