Abstract: Diagenesis in Frontier Formation, Spearhead Ranch Field, Wyoming
W. R. Almon, R. W. Tillman
Spearhead Ranch field produces from about 20 deep wells in the Frontier Formation at about 12,500 ft (3,810 m) in the southwestern part of the Powder River basin of Wyoming. Three cores 116 to 150 ft (35 to 46 m) long were taken by Mountain Fuel during early development of the field. Interpretations from these cores serve as the basis for this study. In the Frontier, production is from offshore marine bars as interpreted by sedimentary structures. Several coarsening-upward sequences up to 70 ft (21 m) thick are present in the Frontier but only the upper sandstone produces and it produces only in part of the area where it was deposited.
The sequential development of chlorite clay films and quartz overgrowths has been the main diagenetic event in the reservoir sandstones of cored intervals of the Frontier sandstone in the Spearhead Ranch field. The distribution of these diagenetic minerals is controlled partly by the sedimentology of the sand units. Chlorite clay films are well developed in the physically reworked, better sorted parts of the sand bodies and are poorly developed in the more poorly sorted parts. In sand bodies where chlorite clay coats were poorly developed, quartz overgrowths subsequently developed.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC