Depositional Environments and Reservoir Properties of the Upper Queen Formation, Concho Bluff and Concho Bluff North Fields, Midland Basin, Texas

Abstract

The upper Queen Formation (Upper Permian) in Concho Bluff and Concho Bluff North fields (Crane, Upton, and Ector counties, Texas) consists of four thick (6-11 m) clastic members separated by evaporite members, and contains several major sandstone reservoirs. A study of cores and logs from the upper Queen was done to determine its depositional environments and the properties of its sandstone reservoirs. Four facies are present in the upper Queen. Facies 1 consists of planar- and wavy-laminated fine and very fine sandstones and silty sandstones deposited in fluvial sandflats and delta-plains. Facies 2 consists of wavy-laminated siltstones and haloturbated mudstones with anhydrite nodules deposited in subaqueous prodelta environments and subaerial saline mudflats. Facies 3 consists of well-sorted fine to very fine sandstones with horizontal and inclined planar laminae deposited in eolian sand sheets. Facies 4 consists of massive to laminated halite and anhydrite deposited in hypersaline playas. The vertical sequence of these facies indicates that the upper Queen was deposited during four cycles of fan-delta progradation into and retreat from coastal-plain playas during a sea level lowstand in the Midland basin. The sandstones of the fluvial sandflat and eolian sand-sheet facies constitute the reservoirs of the upper Queen in themore » fields. The average cumulative thickness of these facies is 8 m, and the fields average 16% porosity and 40-50 md of permeability. The remaining facies are all nonproductive with averagge porosities of less than 10% and average permeabilities of less than 1 md.« less