Anisotropy and spatial variation of relative permeability and lithologic character of Tensleep Sandstone reservoirs in the Bighorn and Wind River basins, Wyoming. Quarterly report, January 1, 1996--March 31, 1996

Work in conjunction with Marathon Oil Company in the Oregon Basin field utilizing Formation MicroImager and Formation MicroScanner logs has been completed. Tensleep outcrops on the western side of the Bighorn Basin are not of the quality necessary to do detailed study of stratification. This made the use of borehole imaging logs, in which stratification can be recognized, particularly attractive for the western side of the Bighorn Basin. The borehole imaging logs were used to determine the dip angle and dip direction of stratification as well as to distinguish different lithologies. It is also possible to recognize erosional bounding surfaces and classify them according to a process-oriented hierarchy. Foreset and bounding surface orientation data was utilized to create bedform reconstructions in order to simulate the distribution of flow-units bounded by erosional surfaces. The bedform reconstructions indicate that the bedforms on the western side of the basin are somewhat different from those on the eastern side of the Bighorn Basin. A report has been submitted to Marathon Oil Company, the principal cost-share subcontractor. Marine dolomitic units initially identified and correlated in the Bighorn Basin have been correlated into the Wind River Basin. Gross and net sand maps have been produced for the entire upper Tensleep in the Bighorn and Wind River Basins, as well as for each of the eolian units identified in the study. These maps indicate an overall thickening of the Tensleep to the west and south. This thickening is a result of both greater subsidence to the west and south and greater differential erosion to the north and east. An article documenting the North Oregon Basin field study will appear in the Gulf Coast Society of Economic Paleontologists and Mineralogists Foundation Conference volume entitled {open_quotes}Stratigraphic Analysis Utilizing Advanced Geophysical, Wireline and Borehole Technology for Petroleum Exploration and Production{close_quotes}