摘要
The Permian Basin is one of the most prolific,and currently one of the most active,oil and gas basins in the USA.The Lower Permian strata in the Permian Basin have produced more than 14 billion barrels of oil(BBO),making it the largest volume of hydrocarbon in the basin.Sedimentation in the Midland Basin during late Leonardian through early Guadalupian(ca.272-269 Ma)resulted in progradation of shelf edge and ultimately closure of the basin by Middle Permian time.We analyzed a merged seismic survey covering parts of the Permian Basin(i.e.,Central Basin Platform and Midland Basin)in Andrews,Ector,and Midland Counties,Texas.The seismic survey and well logs show the presence of gently dipping(ca.1°)clinoforms in the Upper San Andres and Grayburg Formations on the eastern edge of the Central Basin Platform and western Midland Basin.The seismic attributes,curvature,and spectral decomposition identify low sinuosity slope channels oriented north-south,but such channels do not appear beyond the slope.The shelf edge shifts from north to south during deposition of the Upper San Andres and Grayburg Formations.We identify five basinward shifts noted by the migration of the shelf edge toward the basin center and the presence of channel features along the depositional slope.The petrophysical analysis indicates that channels cut into carbonate rocks and are filled by siliciclastic sediments;this interpretation is supported by the most negative curvature anomalies along the channel axes caused by the differential compaction between the carbonate and siliciclastic rocks.There are a few channels with a northwest-southeast strike,which matches the direction of the Concho Lineament observed by satellite data.Such observations are consistent with previous interpretations of the northern Midland Basin closure during Middle-Late Permian time.
