Zonation and Compartmentalization of Tensleep Sandstone Reservoirs

Yin, Peigui¹, Dag Nummedal² (1) University of Wyoming, Laramie, WY (2) Colorado School of Mines, Golden, CO

The Pennsylvanian Tensleep Sandstone in Wyoming was developed along the northern margin of the Ancestral Rocky Mountains. Each depositional sequence is characterized by eolian sandstones toward the uplift and marine carbonates toward the ocean. Frequent and high-amplitude sea level fluctuations generated alternating sandstone-carbonate sequences along the coastline, whereas a thick package of eolian sandstones was developed farther landward, out off reach of the marine transgressions. Stabilization and preservation of the eolian sandstone accumulations were closely linked to the ground water table, which changed in phase with rise and fall of sea level. Early cementation by dolomite and anhydrite caused great heterogeneity of porosity and permeability in Tensleep sandstones due to variation in chemistry of introduced waters. Eight petrophysical facies are identified based on the depositional and diagenetic studies, including uncemented dune sandstone facies, cemented dune sandstone facies, dolomite-grain-rich cemented dune sandstone facies, uncemented interdune sandstone facies, cemented interdune sandstone facies, cemented sandsheet facies, dolostone facies, and dolomitic sandstone facies. Each petrophysical facies is characterized by specific porosity and permeability distributions. Combined with the diagenetic modification, the depositional sequence architecture created lateral and vertical zonation in the Tensleep Sandstone permeability. 

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