Abstract: Foinaven Development - Breaking the Mould

C. Maclean

Foinaven Phase I, the first oil field development West of Shetland, had produced a new standard in the time required between discovery and development. The bedrock of this performance improvement stems from the clarity of hydrocarbon imaging available with new technology based on 3D seismic data.

Oil in the Foinaven field (discovered in late 1992) lies within Palacocene reservoir sands interbedded with impermeable mudstones. Reservoir quality is excellent, although the sands are relatively thin, distributed over a large area, and are overlain by a gas cap.

Prior to appraisal drilling, 3D seismic data were acquired over Foinaven as part of an extensive 2000 sq km survey shot in the summer of 1993.

The conventional 3D seismic data have been inverted to produce an acoustic impedance (AI) dataset. Comparisons of predicted vs. actual hydrocarbon pore thickness during appraisal drilling using the AI data have shown a typical variance of +/- 10%. Overall accuracy of the depth conversion has been excellent.

The AI dataset has been calibrated to net sand using available well data. Stochastic models have been constructed which preserve the information held within the seismic and which describe the distribution of major sand packages.

An horizontal appraisal well, was spudded in mid-1994. Once the target reservoir was entered, directional information from the MWD tool was used to steer the well along a desired path in real time to intersect with specific targets. Once the hole had been cleaned, it was then completed using a pre-packed production liner.

To further evaluate the reservoir, following an initial horizontal well drill-stem test an extended well test, using a semi-submersible linked to a shuttle tanker was undertaken. Over 400,000 bbl oil were produced from the Foinaven reservoir. This extended test yielded significant long-term development information.

The combination of technologies, seismic, drilling and extended well test, has proved invaluable in advancing the appraisal of Foinaven.

Foinaven Phase I will be developed by Petrojarl IV a ship shaped Floating Production, Storage and Off loading (FPSO) facility, currently being rebuilt in Northern Spain. In conjunction with the FPSO horizontal production wells will be used with subsea completions and following processing the crude oil will be exported by shuttle tanker to the refinery. Development drilling started in November 1994. First oil is programmed for early 1996 at a plateau rate around 85 mbd.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France