Midstream companies Tallgrass Energy and Silver Creek Midstream are expanding their joint venture in Wyoming's Powder River Basin. : Tallgrass Energy and Silver Creek Midstream are expanding their joint venture in the Powder River Basin (PRB). The JV was formed by Tallgrass and Silver Creek in February to develop the Iron Horse Pipeline, an 80-mile, 16-inch crude oil pipeline currently under construction, which will be used to transport crude oil from the growing Powder River Basin to Guernsey, Wyoming.