The Pennsylvanian (Desmoinesian) Burbank sandstone in Tract 97 of Osage County, Oklahoma, is 2,845-2,945 ft (867-897 m) deep. Samples of the Burbank from cored intervals of five wells were analyzed to determine depositional environment, diagenetic alterations, and the effects of diagenesis on reservoir rock properties.
The Burbank sandstone consists of very fine to fine-grained lithic arenites deposited under fluvial-deltaic conditions. Though quartz dominates in the detrital fraction, rock fragments, primarily metamorphic, and feldspars constitute as much as one-third of the grains. Compaction, authigenesis, replacement, and dissolution have significantly altered the texture and composition of the Burbank sandstone. Compaction is relatively minor due to early cementation. However, multiple stages of authigenesis have given rise to abundant silica and carbonate cements and clay minerals, which together constitute approximately one-fourth of the bulk volume of the sandstone. Clay minerals, dominantly iron-rich chlorite with minor illite, occur as pore lining, pore filling, and replacement of silicate grains. Replacement of detrital particles by carbonate cement is ubiquitous; such replacement seems to be susceptible to dissolution. Dissolution of grains and particularly cement has yielded the present average porosity of 15%.
Hydrocarbon recovery from the Burbank sandstone is complicated by depositional changes and diagenesis. For a tertiary recovery program to be successful, the effects of cementation, dissolution, and authigenesis must be considered in the design.