Heavy-Oil Field Development and Reservoir Management Challenges in Producing Onshore Shallow Reservoirs in Suriname

摘要

The Tambaredjo field was discovered in 1968, near the Calcutta village, by a wildcat well C9. A production test was carried out in the appraisal well TA-4, which proved the find to be semi-commercial at the time of the discovery[1]. After the establishment of Staatsolie Maatschappij Suriname N .V., the State Oil Company of Suriname, South America, on December 13, 1980, another well TA05 was drilled and tested in 1981. This well proved the producibility of the field. Oil production started on November 25, 1982 and the production was 250 BOPD from 5 wells. As of May 2006, the average oil production is 13,000 BOPD from 914 production wells in the two fields, Tambaredjo and Calcutta. The coastal plain of Suriname, together with that of both French Guyana and Guyana, form the onshore part of the Guyana sedimentary basin. Progressively, older beds overlap the basement in northern direction. The reservoirs are of coastal and non-coastal depositional environment (fluvial to shore-face) presenting erratic sand development. Reservoir continuity and heterogeneity within these shallow thin fluvial related sands pose great uncertainty even within a grid drilling of 10 to 30 acres spacing. This is uniquely challenging for field development and reservoir management. Oil production in Tambaredjo comes from a number of unconsolidated sands, especially the T-sands with thickness from 3 to 45 ft, at average depths of 900 (275 m) to 1200 ft (400m) with a formation temperature of 98°F (37°C). Reservoir pressures are hydrostatic. It has an average porosity and water saturation of 39.0 and 25.0 percent respectively. The oil has a viscosity of 600 cp and an API degree of 17. Developing and producing this 600 cp heavy oil within thin sand with low reservoir pressure warrants the use of artificial lifting by means of progressive cavity pumps (PCP). This adds to the difficulties of getting valuable wireline survey or subsurface data acquisition. Reservoir performance prediction utilizing the production data history has always been challenging. Efforts are being made to increase recovery and reserves by applying EOR processes (polymer flood and in-situ combustion) and infill drilling to increase production within these thin sands with high geological uncertainties and early water breakthrough problems. Hence, this paper presents some of these unique challenges in developing, producing and managing these onshore shallow reservoirs in Suriname.