The Horse Creek field in Laramie County, Wyoming, was discovered and developed by the General Petroleum Corp. following a reconnaissance gravity survey and preliminary and detail seismic surveys. The gravity survey, made during 1940, delineated a strong maximum gravity anomaly having a magnitude of about 5 mg. Limited seismic work was then conducted in the area during 1941 and 1942 and mapped a prominent anticline having some 2,000 ft. of closure. In Sept. 1942, General Petroleum Corp. spudded in their No. 78-31-G well, located on the apex of the structure. This well was completed as the discovery for the field, producing from the lower Cretaceous-Lakota sand. The second well, No. 74-6-P, was completed in Apr. 1943, as the lower Cretaceous-Muddy sand discovery for the field. Further seismic work was done during 1944 and 1945 to detail and refine the structural picture. Subsequent drilling developed the Muddy sand as the primary producing zone in this field. A total of 32 producing wells has been drilled on this structure, and to Aug. 1958 the total cumulative production from the field was 3,519,000 barrels of oil.