Exploration, Development, and Reservoir Engineering Studies for the Tapis Field Offshore Peninsular Malaysia

Abstract

Summary This paper presents the rationale for oil development in the sandstone reservoirs of the Tapis field offshore Peninsular Malaysia. Pressure maintenance plans, well Peninsular Malaysia. Pressure maintenance plans, well spacing, and completion plans have been modified in response to data from exploratory and development drilling. Reservoir simulation has been a valuable tool in optimizing field development. Introduction The Tapis field is located in the South China Sea, 130 miles (209 km) off the east coast of peninsular Malaysia in 210 ft (64 m) of water (Fig. 1). Esso Production Malaysia Inc. (EPMI) has explored and developed the field as a contractor to Petroleum Natl. Berhad (PETRONAS), the Malaysian national oil company. Development plans for the field have been modified several times on the basis of data obtained from ongoing exploratory and development drilling. The producing reservoirs at Tapis are Miocene Age Group J (Tapis formation 1) sandstones that contain rim-type oil accumulations with associated gas caps. The three primary reservoirs, J-20, J-25, and J-30, are shoreface/barrier bar deposits separated by shale sequences. Both faulting and stratigraphic variations cause localized discontinuities across the field. Development wells from 4 platforms and 10 exploration wells have delineated most of the field. Reinjection of casinghead gas and waterflooding are being used to increase ultimate oil recovery. Two fieldwide reservoir-simulation studies have helped to optimize field development. These modeling efforts enabled selection of optimal waterflood pattern and determination of water-injection requirements, relative merits of commingled production vs. selective completions, benefits of gas injection, and recovery efficiency for the field. Detailed reservoir description work allowed assessment of reservoir continuity and assisted in selection of workovers needed to implement the waterflood. Exploration Exploration History The Tapis field was discovered in 1969 with the drilling of Tapis Well 1 near the crest of the structure (Figs. 2 and 3). The well, Esso's first in the Malay basin, found gas in the sandstones of Groups J and K. In 1974, Tapis Well 2, drilled downdip to Tapis Well 1, discovered oil in the Group J sandstones. It encountered a gas/oil contact (GOC) in J-20, establishing a hydrocarbon column of 740 ft (226 m) and a proved oil column of 170 ft (52 m). Pressure and fluid data indicated that the lower Group J sandstones (J-20, J-25, and J-30) had common fluid contacts and were in a separate fluid/pressure system from the upper Group J sandstones (J-10 and J-15). In 1975, Tapis Wells 3 and 4 were drilled to delineate the Group J oil columns on the flank of the structure. Both wells encountered oil in the Group J sandstones and the lower Group J proved-oil column was extended to 1,516 ft (462 m). JPT P. 1051