Sublacustrine-fan sandstones in Eocene Es4x are important hydrocarbon reservoirs.
Evaporite and related diagenetic processes critically influenced reservoir quality.
Microbial sulfate reduction (MSR) resulted in precipitation of micritic dolomite and framboidal pyrite.
Dehydration fractures within anhydrite could increase reservoir permeability by connecting isolated pores.
Dissolution of gypsum and anhydrite related to thermochemical sulfate reduction contributed little to reservoir quality.