The Middle Ground Shoal field is an elongated structure located offshore in the middle of the Cook Inlet. The field is approximately 20 kilometres in length and its southern end lies 10 kilometres to the west of the Tesoro refinery on the Kenai Peninsula. The Middle Ground Shoal field contains predominantly oil, but also has an associated gas cap. The field began production in 1966. Remaining production from the field is currently operated by ExxonMobil.