Generation of Depositional Facies Maps Using Microcomputers and Lithocrossplot Data, Minnelusa Formation, Powder River Basin: ABSTRACT

Abstract

A series of depositional facies maps for units within the upper member of the Permo-Pennsylvanian Minnelusa Formation was generated using data from core descriptions and geophysical logs in combination with regional isopach maps. Over 1,300 ft (396 m) of described core from 22 wells was used to calibrate log readings to the four principal lithologies: anhydrite, dolomite, cross-bedded sandstone, and wavy-bedded sandstone. Log cutoff values for each lithology were derived from core through graphic and statistical analysis routines using standard cross-plots. Over 24,000 ft (7,315 m) of synthetic core was generated for 121 uncored wells. Data were analyzed with microcomputers using common software such as LOTUS 1-2-3 and dBASEII. Clastic and carbonate percent maps were ade using all 143 control points. Lithofacies work maps were then constructed by overlaying clastic and carbonate percent maps with regional isopachs. Facies interpretations, based on sedimentary features observed in core, were extrapolated to the lithologic sequences in the synthetic cores. These interpretations served as environmental constraints in the construction of the final facies maps. End_of_Article - Last_Page 862------------