ABSTRACT
The Queen Formation is a sequence of interbedded siliciclastics, carbonate mudstones, and evaporites, that extend across a large area of the subsurface Permian basin in west Texas and southeastern New Mexico. We present a description of the lithologic and diagenetic characteristics of the formation in Millard field, Pecos County, Texas, and propose a model for its depositional environment and reservoir formation.
The Queen Formation in Millard field consists of four major lithologic characteristics: (1) cross-stratified or ripple-laminated sandstones of eolian origin, and a sabkha mudflat facies complex composed of (2) unfossiliferous and anhydritic mudstones, either massive or ripple-laminated; (3) thin dolomicrite crusts with birdseye structures and desiccation cracks; and (4) anhydrite in the form of discrete nodules, beds of nodular-mosaic texture and massive beds in the mudstones and sandstones, and as palisade anhydrite in the mudstones and dolomicrites.
Production from the Queen Formation in the field is consistently from two eolian sandstone units, designated the Queen A and C, which can be correlated across the field area. SEM examination of these sandstones indicates a positive correlation between the amount of grain-lining, authigenic smectite and porosity, and concomitantly an inverse relationship between anhydrite cement content and porosity. The porosity of the sandstone reservoirs in the Queen is of secondary origin.
