Stratigraphy and Depositional Setting of the Lower Missourian (Pennsylvanian) Bethany Falls and Mound Valley Limestones, Analogues for Age-Equivalent Ooid-Grainstone Reservoirs, Kansas

Significant quantities of mobile oil remain in Pennsylvanian reservoirsin the midcontinent region of the United States. To recover this oil efficiently, we mustunderstand the factors that control heterogeneity in these complex reservoirs. One wayto accomplish this is to evaluate reservoir-quality carbonate units that occur in both theoutcrop and the shallow subsurface as analogues to equivalent producing zones. Insoutheastern Kansas the lower Missourian Bethany Falls and Mound Valley limestonescontain oolitic grainstones similar to coeval productive lithofacies that occur in thedeeper subsurface to the west. Depositional sequence analysis of these grainstone-bearing units suggests that (1) at least two cycles of relative sea-level change led to thedeposition of discrete oolitic grainstones that are separated by subaerial exposuresurfaces, with these surfaces strongly influencing the vertical distribution of porosity,and (2) the character and distribution of reservoir-scale grainstone buildups werestrongly controlled by preexisting depositional topography.