Description: The foremost conclusion of this study is that fractured Devonian shale gas reservoirs, as exemplified by the Cottageville field, are detectable by seismic reflection methods. Further, the target is not particularly difficult, once the nature of the seismic anomaly is understood. The preferred exploration rationale is based on travel time anomalies related to lowered acoustic velocity within the gas-bearing zone. In the simplest case the travel time anomaly causes an apparent down-warp or sag in a flat-lying reflector. This conclusion is developed in Parts B and C of this report. Concerning the high-resolution extension of the seismic method, which is the subject of Part A, there are essentially two separate conclusions which can be drawn. One is that additional, valuable subsurface information can be obtained by recording seismic data at frequenies higher than those in common use by the petroleum industry at the time of this writing. The other is that it is feasible to obtain seismic reflection data on a smaller scale, using less costly instrumentation, than is typically employed in the petroleum industry. However, it is not yet possible to say whether such small scale surveying will be practical from an industry point of view.
Date: June 1, 1982
Creator: Williams, R.T.; Ruotsala, J.E.; Kudla, J.J. & Dunne, W.E.
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