Reservoir clay mineralogy of the Topaz Oil Field, Red River County, Texas

The type and amount of clay minerals present in sandstone hydrocarbon reservoirs may have profound effects on reservoir quality and petroleum production. The type, abundance, morphology, and reactivity of clay minerals in hydrocarbon reservoirs are among the factors controlling reservoir quality. Scanning electron microscopy and X-ray diffraction are the two analytical techniques required to characterize clay minerals in clastic reservoir rocks.; The Clarksville Sandstone in the Topaz Oil Field contains a clay assemblage of illite, kaolinite, and iron rich chlorite. These clays are common throughout the reservoir and have the potential of seriously degrading production. Mite is the most abundant clay component and it occurs as detrital overlapping flakes with irregular edges that are sometimes crenulated. Mite tends to coat the detrital quartz grains. Smaller amounts of kaolinite are present, occurring as delicate, neoformed booklets composed of stacked pseudohexagonal grains that partially fill pores. Iron rich chlorite is also present, occurring as neoformed crystals with face-to-edge morphology. It is present as two different petrographic types, chlorite grain coating and chlorite pore filling. Permeability is very sensitive to the relative abundance of clays.