Depositional facies, diagenesis, and reservoir character of Mississippian cyclic carbonates in the Mission Canyon formation, Little Knife field, Williston basin, North Dakota.

Abstract

Reservoir development and hydrocarbon accumulation in Little Knife field are the result of structural flexure and stratigraphic entrapment, coupled with diagenetic porosity development. The Mission Canyon formation represents a prograding carbonate sequence with some upward-diminishing cyclic carbonate sedimentation as a result of overall regression. Depositional environments changed from dominantly open shallow-marine settings into transitional and restricted, low-energy, shallow-marine environments on a protected shelf, to emergent barrier island and back-lagoon sections overridden by prograding supratidal flats. Within the mud-enriched protected shelf setting, the transitional open shallow-marine to restricted shallow-marine facies were dolomitized and contain all hydrocarbon-bearing beds. Subtle facies variations in original lime-mud content, burrowing and compaction combined to cause parts of the formation to be more susceptible to development of porosity through anhydrite replacement, dolomitization and later leaching of anhydrite.-J.M.H.