Introduction

A reflection seismic experiment was conducted over the Minneola complex of oil and gas fields in Clark county, southwest Kansas (Fig. 1) in an attempt to acquire high-resolution data that might distinguish a Morrowan-Atokan clastic section containing thin productive sandstones near the top of a channel fill to estuarine/marine section, from one that does not contain these sandstones (Fig. 2). The specific fields studied during this project are the Norcan and Norcan East fields (Fig. 1). Previous seismic data acquired in the area suggest that generally southwest-northeast trending channels up to 86 ft deep or more incised into underlying Mississippian limestones are imaged as a high amplitude trough surrounded by high amplitude peaks compared to the much lower amplitude reflection at the same level when a channel is not present (Clark 1987, 1995). Diffractions, and sometimes faults in the underlying Mississippian limestones also help outline the margins of the channels. Unlike typical channel sandstones, though, the productive sandstones at in the Minneola complex occur near the top of the basal clastic section (Fig. 2) and are more likely associated with a marine barrier bar or estuarine facies that is thicker in the channels, possibly due to compaction of the shales or lower bathymetry. These sands have been interpreted to occur in a series of northwest-southeast trending bars, separated by shales (Clark 1987, 1995). Because of this, numerous wells that have been drilled in the deeper channels and have encountered only shale or only very thin (few feet) unproductive sandstones. Because the productive sandstones are still not very thick (maximum gross in the project area is 15 ft), previous lower frequency seismic data was unaffected by the presence or absence of the sands. Therefore a drilling program could only be based on geology and the seismicly defined channels.

The purpose of this project was to determine if a seismic technique designed to acquire high-frequency data could be used in the Minneola area to define channels with thicker, productive sands from those that contained only thin, non-productive sands, or no sands at all. To accomplish this goal, three lines were laid out: One along a major seismicly and geologically defined channel, the other two across several channels (Figs. 3, 4, 5, 6, 7, 8). These lines also crossed areas with the productive upper sandstones in the channels and areas with no sand in the channels (Figs. 9,10,11).