Seismic Expression of Marts Field (Silurian Reef) in Sullivan County, Indiana

H. J. Renick, Jr., R. M. Rene, N. C. Hester, F. L. Stanonis

The Marts field of Sullivan County, Indiana, is associated with a Silurian reef that is part of the Terre Haute bank on the eastern flank of the Illinois basin. Gas production has come from Pennsylvanian sandstones at Marts field, and oil is presently being produced from limestones of the Devonian Muscatatuck Group. Hydrocarbons were trapped in the Devonian limestones because of structural drape over the reef. A 2.8-km (1.8-mi) north-south 24-CDP reflection seismic profile across the Marts field was obtained by using a hydraulic-assisted weight drop with a source array interval of 16.7 m (55 ft). The data were digitally processed through statics corrections, deconvolution, stack, and migration. These data clearly image drape in Carboniferous and Devonian strata, a characteristic chang in reflection pattern at the reef flanks, and diffractions associated with the reef flanks. Near Marts field, one well penetrates Silurian strata, and a synthetic seismogram for this off-reef well is tied to the seismic section.

Using well data from Marts and other reefs, mirror-imaged cross-plots of depths to tops of formations vs. depth to top of the Devonian limestone aid in examination of the drape. These plots of "transformed cross sections" approximate those of vertically stacked right circular cones indicative of the linear relationships between depths to formations.

AAPG Search and Discovery Article #91023©1989 AAPG Eastern Section, Sept. 10-13, 1989, Bloomington, Indiana.