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Geochemical Impact of Fluid Injection into St. Peter Sandstone Within the Kankakee Arch: Implications for Salt Water Injection and Disposal


Geochemical Impact of fluid injection into St. Peter Sandstone within the Kankakee Arch: Implications for Salt Water Injection and Disposal.

Thomas, Richard M. Devon Energy, Oklahoma City.

Salt water injection into the Kankakee Arch, specifically the St. Peter Sandstone, could serve as a deep geologic repository for waste salt water from producing oil and gas wells in the region. This research aims to explore the viability of this proposed deep injection reservoir. There are some basic criteria that must be met to effectively store waste brine in a geologic reservoir. First, the reservoir must have sufficient porosity and permeability for both injectivity and for migration of the injected fluid through the reservoir. Second, the reservoir must be overlain by some form of impermeable seal or cap layer(s). Third, the reservoir should be sufficiently isolated from interaction with surface and near surface water. Finally, the formation must contain enough storage volume to handle significant amounts of injected material.

Based on the above criteria, a promising candidate for injection and disposal is the St. Peter Sandstone in the Kankakee Arch. This study investigates the viability of saltwater disposal within the St. Peter Sandstone on a micro scale.

Initial porosity of the formation plug samples yielded a range of 16% to 19%. Initial permeability ranges from 26 to 981 millidarcies (mD). This wide difference in permeability is attributed to the variation in strength of cement, in this case quartz overgrowth in the sandstone. This preliminary evidence indicates that the storage capacity of the formation will remain constant or increase depending on injection location, suggesting that the St. Peter Formation will lend itself well to future salt water disposal.