Ratcliffe Anhydrite Edges - Indicators of Paleo- Structure in the Central Williston Basin, U.S.A.

Hendricks, Michael L. ¹ (1) Hendricks and Associates, Inc, Englewood, CO

Anhydrite edges can be used to depict paleo-structural trends in the Flat Lake Interval of the Ratcliffe Formation in the central Williston Basin. Well defined salients and reentrants correspond to bathymetric changes that overlie ancient structural trends. Recent horizontal drilling indicates that production is highest within Ratcliffe reentrants where subtidal sediments are thick and secondary porosity is common. The subtidal system is fractured producing variations in reservoir productivity. Facies changes to deeper and tight subtidal sediments to the west and impermeable shoreline and sabkha sediments to the east limit the Flat Lake producing trend in this portion of the basin

AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana