Grieve oil field was discovered in August 1954. The field is located in southeastern Wind River Basin, central Wyoming, and is currently operated by Elk Petroleum Inc. (Elk Petroleum), Figure 1. The producing oil reservoir is a stratigraphic/structural trap at a depth of 6,900 ft in the Lower Cretaceous, valley-fill and channelized, Muddy sandstone. The average structural dip in the Grieve area is about 15 degrees to the northeast.