Abstract

The McMurtrey No. 1 well, 5 miles southwest of Eden, Concho County, Texas, along the southern portion of the Eastern Shelf of the Midland Basin was drilled on the basis of a subsurface geological anomaly mapped on the lower King sandstone that was confirmed and enhanced by soil gas geochemistry. The well encountered 38 feet of sandstone, and was potentialed for 79 BOPD (pumping).

The lower King sandstone at the Lonesome Dove II Field is part of a larger NE-SW trending Cisco depositional system. Data from two conventional cores, samples, sidewall cores, dipmeters, and electric logs indicate that the lower King sandstone was deposited during a regressive cycle of fluvial-deltaic sedimentation. It has characteristics of both fluvial point bars and distributary channels, and the development of a distributary model of deposition led to the extension of the field beyond the limits of the original subsurface and geochemical mapping. The presence of two or more separate channels or channel systems is indicated by isopach maps and by significant oil gravity, field pressure, and grain-size differences. These channel systems are interpreted to have been deposited on a relatively flat-lying deltaic plain as indicated by cross sections showing only slight channel downcutting.