E8 Innovative Field Development

Abstract

E8 is a carbonate reservoir with an estimated ultimate recovery of 2.157 Tscf gas and 35 million stb of condensate. The reservoir is a carbonate build-up, consisting of two pinnacles connected through a saddle area. The field will be developed at a peak capacity of 600 MMscf/d. As a result of the study work for the FDP, the expectation recovery has increased by 370 Bscf gas. This is driven by an updated structural model based on a revised seismic interpretation. This has been achieved through a combination of improved depth conversion method (Depth Team Express) as well as uncertainty reduction based on seismic inversion techniques. In the era of uncertain hydrocarbon prices, optimisation is aimed at ensuring high system availability, maintaining safety and environmental standards while achieving an economic development. This paper describes the efforts undertaken to maximise recovery from the field and the initiatives undertaken to resolve challenges. The main challenges faced in converting the development concept from standalone to satellite were production forecasting, security of supply, slug management and unmanned operations. Introduction The E8 field is located some 140 km NW of Bintulu in a water depth of around 195 ft. With current expectation gas reserves of 2.5 Tscf (to an abandonment of 300 psi), it is the smallest of the five Central Luconia gas fields (E8, E11, F13, F6, F23), which have been committed to the MLNG PSC. The accumulation is contained in a pinnacle-type carbonate build-up with two culminations, separated by a saddle area. The southern culmination has a gas column in excess of 1600 ft in the pinnacle, whilst the northern culmination has a maximum gas column of 650 ft. The gas is characterised by a low measured CO2 content of 1.7% and H2S content of less than 10 ppm. The southern culmination of the field was discovered by well E8–1 in 1970, and the northern culmination in 1978 by well E8–4 (the two appraisal wells E8–2 and E8–3 tested the southern culmination and off structure silici-clastics respectively). The main subsurface uncertainties are degree of communication and nature of the reservoir between southern and northern accumulations, gross bulk volume and reservoir properties distribution. Start-up of production is planned for July 2006. The initial development scenario was for a standalone facility at E8. All processing would be carried out at E8 before piping the gas, via the E11 and existing trunklines. There are opportunities to further reduce the development cost via options such as unmanned operations or produce E8 as a satellite to the existing E11 Complex. The satellite option will potentially reduce a substantial amount of capital expenditure. At the start of the field development, there were a number of surface uncertainties that had to be resolved such as security of supply and scope of additional facilities at E11. Subsurface In this section an overview of the E8 reservoir is provided (see Figures 1 and 2). The E8 gas field is a carbonate reservoir of Middle Miocene age (i.e. 10 million years ago). The carbonate reservoir was developed during a period of extensive coral reef growth and carbonate sedimentation over the Luconia shelf. Some modern day analogues of such an environment would be Layang Layang in the Spratly Islands, Bahamas Bank and the Great Barrier Reef. The E8 field is overlain by an extensive thickness of deep marine shales, which provide the reservoir seal. In the very shallow overburden, i.e. < 1000ft, seismic anomalies are seen indicative of shallow gas bearing sands. In E8 this shallow gas directly overlies and is aerially confined to the southern pinnacle only (see Figure 3).