Provenance, Diagenesis, and Reservoir Characteristics of Shattuck Member of Queen Formation (Permian), Northwest Shelf, Permian Basin: ABSTRACT

Abstract

The Shattuck Member of the Queen Formation forms important stratigraphic traps for oil and gas on the Northwest shelf of the Permian basin. The Shattuck is a wedge-planar body of well-sorted silty sandstone and has a detrital composition of 70-85% quartz, 15-30% feldspar, and traces (less than 2%) of mica and opaque iron-oxide grains. Generally, the quartz grains are rounded to subrounded and the feldspar grains (which are mostly microcline) are partly weathered and dissolved. The detrital composition of the Shattuck reflects its partial derivation from deeply weathered granitic rocks in the Pedernales Mountains. The texture and roundness of the quartz grains reflect the effects of transport by the wind, which deposited the Shattuck on the Northwest shelf during a lowstand of sea level. The reservoir lithology within the Shattuck is a pale yellow-brown sandstone that was deposited in desert dunes and dry sand sheets. This sand was cemented by anhydrite, dolomite, and authigenic clay during a shallow (precompaction) diagenetic phase, but the cement was later partly dissolved. The reservoir lithology presently has 2-15% porosity and permeabilities between 30 and 500 md. The nonreservoir lithology is a reddish-brown sandstone that was deposited in wet eolian sand sheets and contains detritalmore » hematitic clay (as matrix and within laminae) and hematite-coated detrital grains of possible pedogenetic origins. This sand was completely cemented by anhydrite, dolomite, and traces of authigenic clay during a shallow diagenetic phase, but the cements did not later dissolve to form secondary porosity. The nonreservoir lithology presently has less than 1% porosity and less than 10 md permeability.« less