Running Duke Field, a small domal structure. Five gas wells; water-free gas production from zones with water saturations in excess of 60%. Porosity ranges from 7 to 14%. Development of an active organic buildup, successively overlain by ooid-skeletal-peloid lime sands, lagoonal lime muds, and subsequently by anhydrite and shale. Six lithofacies; each has a uniform diagenetic history, making porosity development predictable for each facies. The one grainstone facies forms the reservoir in the field and has two distinct diagenetic sequences; one consists of a marine isopachous cement followed by a later partial infilling of pore space by sparry calcite; the other, a discontinuous meteoric phreatic cement followed by sporadic patches of sparry cement.--Modified journal abstract.