Ceiba Field Subsurface Considerations

Abstract

Abstract This paper describes some of the subsurface considerations that were involved in Triton Equatorial Guinea, Inc. (Acquired by Amerada Hess Corporation in August 2001) rapid development of the Ceiba field. Introduction The Ceiba Field is located offshore Equatorial Guinea approximately 75-km southwest of the port city of Bata and 275 km south of the city of Malabo (Figure 1). The Ceiba Field was discovered in September 1999, with the drilling of Ceiba-1. The first appraisal well, Ceiba-2 was drilled in November 1999 approximately 1.6-km southwest of Ceiba-1. Ceiba-1 and Ceiba-2 were drilled based on interpretation of 2D seismic data acquired between 1984 and 1998. Open-hole logs, cores, pressure data, and a DST of Ceiba-1 indicated that both wells contained Cretaceous sands of very high quality, capable of producing high rates of oil. Ceiba-1 was drill stem tested at rates as high as 12,400 barrels of oil per day. Ceiba-2 was not tested because of the excellent reservoir quality indicated from the open-hole logs, cores, pressure data, and the oil samples recovered. Figure 2 shows the general stratigraphic section from the Rio Muni Basin, which was encountered in both wells. In December 1999, the Ceiba Field Plan of Development Phase 1 was submitted to the Equatorial Guinea Ministry of Mines and Energy. The Plan detailed the work necessary for early, initial production from the Ceiba Field. The Plan of Development Phase 1 was approved in December 1999. A 3D seismic survey was completed over Block F and Block G in March 2000. A portion of the survey that encompasses the primary Ceiba reservoir was processed and interpreted to determine the location of appraisal wells necessary to confirm the extent of the field. Results of the 3D seismic survey were used to select the placement of three further appraisal wells, Ceiba-3, Ceiba-4 and Ceiba-5. These additional appraisal wells were drilled in June and July of 2000 and confirmed the presence, connectivity, and quality of the reservoirs encountered in the Ceiba-1 discovery well. The locations of the drilled wells are shown on Figure 3. Concurrent with the drilling of the appraisal wells, construction of an early production system consisting of a converted oil tanker was initiated. In November 2000, only 14 months after initial field discovery, the Sendje Berge FPSO was installed in the Ceiba Field and production commenced from the Ceiba-2 well. Geologic Ceiba Field is located on the present day continental slope in approximately 700m of water. The depth to the crest of the structure is approximately 2125mSS at the Top Campanian reservoir level. The depth to the free water level is 2471mSS giving the field a gross-oil-column-height of 346m. The field sits within a NE-SW trending belt of salt-cored structural highs, interpreted as base of slope compressional features, in the Rio Muni Basin.