Angola Block 18: a deep-water exploration success story

Abstract

Offshore Angola Block 18 was awarded to Amoco in October 1996 for an initial four-year exploration period with an associated four well commitment. This was subsequently extended in October 2000 for an additional three years and further two well commitment. Ownership is BP (operator) 50% and Shell 50%. The block covers an area of 4880 km 2 , the equivalent of some 35 UKCS blocks. Water depths range from 200m in the east to over 1600m in the west. Block 18 is almost entirely covered by over 5000 km 2 of high quality 3D seismic data. Exploration activity has, to date, focused on the western part of the block lying in 1200–1600m of water on the southward extension of the successful Tertiary play from Blocks 15 and 17. Reservoir targets occur in Miocene and Oligocene submarine slope channel sands associated with the evolving Congo River cone. Charge is derived from Upper Cretaceous–Tertiary marine shales of the Iabe Formation. Dominant trap styles are combined structural and stratigraphic domes and turtles associated with movement of Aptian salt. Since the BP–Amoco merger in January 1999, six exploration wells have been drilled to fulfil the first and second phase exploration commitments (Platina, Plutonio, Galio, Paladio, Cobalto & Cromio) all of which have been significant oil discoveries in turbidite channel and sheet sands of Miocene and Oligocene age. Given an unprecedented six discoveries out of six wells, it is clear that the working Tertiary fairway in Block 17 extends south into Block 18. Keys to success have been rapid integration of BP’s Block 15 and 17 experience with existing Amoco interpretation and technologies in Block 18. The learnings from the successful exploration campaign in Block 18 Angola, specifically in the use of high quality 3D seismic attributes as a risk reduction tool, have application in deep-water plays elsewhere, such as the Tertiary and Upper Cretaceous of the North Sea and offshore mid Norway.