Potential Reef Reservoir Objectives in the Lower Mississippian St. Joe Group (Kinderhookian to Basal Osagean) in Southern Kansas

Beau Morris and Sal Mazzullo

Porous reef limestones, commonly with significant oil shows, are present in outcrops of the St. Joe Group in SW Missouri and NW Arkansas. Specifically, the reefs are present in the Compton and Pierson formations, and reefs are not known to be developed in the intervening Northview Formation. These reef occurrences are analogs of potential petroleum reservoirs in subsurface Kansas. The reefs are developed on south-sloping ramps, particularly where they intersect topographically-positive seafloor features related to syndepositional Ouachita tectonism. They were constructed by fenestrate bryozoans and crinoids, and porosity therein was related to post-depositional subaerial exposure and meteoric dissolution. In the subsurface of southern Kansas, indications of reefing in the Compton and Pierson formations in similar locations on their respective ramps are: (i) abrupt thickening of these units as indicated on wireline logs and (ii) concomitant development of high porosity, and (iii) the presence of reef facies in some cores. Petroleum reservoirs in such rocks are most likely to dominantly be depositional-facies traps associated with overlying tight limestone or shale seals. Late Kinderhookian and early Osagean erosion, however, locally may impart some degree of paleotopographic trap development on these potential reservoirs. Oil production from such reef facies is known from some fields in northern Oklahoma, and a play for these rocks may extend into southern Kansas. 

AAPG Search and Discovery Article #90176©AAPG Mid-Continent Meeting, Wichita, Kansas, October 12-15, 2013