A REVIEW OF THE LITHOFACIES AND DEPOSITIONAL ENVIRONMENTS OF THE MUDDY/NEWCASTLE SANDSTONE IN THE EASTERN POWDER RIVER BASIN OF WYOMING

Hydrocarbon production from the Lower Cretaceous Muddy/Newcastle Sandstone in the Eastern Powder River Basin of Wyoming commenced in 1887. To date, vertical wells have produced several hundred million barrels of oil from Muddy/Newcastle stratigraphic traps. Multiple stacked sands within the Muddy/Newcastle were recognized by the 1940s, but there was much debate over the subsequent 20 years regarding the depositional environment of the individual sand units. Workers then recognized that continental deposits were possibly time equivalent to marine deposits further west in the basin. It took a hundred years of drilling, combined with outcrop and core studies, to develop a robust lithofacies model. The Muddy/Newcastle is interpreted to consist of fluvial, deltaic, estuarine and shallow-marine deposits in the basin. Understanding of these different lithofacies and their depositional environments has important implications for field development, horizontal drilling and enhanced oil recovery projects.