Performance of the Sussex Area Tensleep Reservoirs

This is a report on the performance of three Tensleep sandstone reservoirs located within an area of 6 sq miles in Meadow Creek and Sussex fields, Johnson County, Wyo. The fields are in the Powder River Basin near Linch, Wyo., which is 8 miles northeast of the Salt Creek field. The surface location of these reservoirs is shown in Fig. 1. The Sussex field was discovered in July, 1948. There are three separate producing areas including the West Sussex, Sussex, and Meadow Creek fields in the general Sussex area. At the present time there are over 350 producing wells completed in seven producing horizons varying in depth from 3,000 to 9,200 ft. The initial Tensleep discovery was in June, 1951 in the Sussex Unit A area. The initial Tensleep discoveries in the Meadow Creek Unit and in the Sussex Unit B areas were in March and June, 1952, respectively. Due to market allowables, development of these reservoirs was somewhat restricted until the latter part of 1953. Development since that time has continued on 40-acre spacing in each reservoir. The Sussex Unit Tensleep A reservoir is approximately 1 ¼-miles long and ½-mile wide. The Sussex Unit Tensleep-Amsden B reservoir is approximately 2 ½-miles long and 1 ½-miles wide. The Meadow Creek Unit Tensleep reservoir is approximately 2-miles long and 2-miles wide. It will be the purpose of this paper to discuss basic reservoir and geological characteristics, past performance and producing problems of these Tensleep reservoirs. The three reservoirs will be discussed separately in each section in order to bring out similar basic characteristics, as well as to show the contrast in individual reservoir performance. Future performance predictions have been made, but because of the relatively short producing history, they will be discussed only from an academic viewpoint. Development Sussex Unit Tensleep A The Tensleep A discovery well was completed in June, 1951, for a natural flowing potential of 585 BOPD. Development continued on 40-acre spacing, and seven wells have been completed in the reservoir. All wells are open-hole completions and the reservoir is fully developed. The original water-oil contact was at an elevation of –4,330 ft mean sea level as determined lay drill-stem tests and production data.