Total has been operating oil and gas production from a series of heterogeneous reservoirs offshore Abu Dhabi since 1974. The recovery efficiency is already one of the highest in the industry compared to analogous carbonate reservoirs worldwide and the lessons learnt on this field can be usefully applied in the future on other less mature fields in the region.

Since the drilling of the first multilateral well in 1996 most of the infill wells drilled are multilateral with up to 6 drains per well slot targeting different reservoir layers. The layers have different permeabilities, porosities, oil quality, depletion and residual oil saturation. A database containing 20 years of production data from ca. 130 horizontal or multi-lateral penetrations cross-referenced with log and core data now exists.

This paper describes how Total has applied pragmatic technologies in a challenging environment to give itself the best chance of economic success when drilling this type of well. In particular, issues such as target choice, anti-collision with existing wells, flexibility to make "last-minute" target changes, keeping the well within thin layers and the production benefits of zone selectivity will be discussed.

In a 40 year old water-flooded reservoir with diminishing infill targets scattered across the field it has been important to maximize the chances of economic success by maximizing the use of existing data and introducing flexibility in the drilling proposal and well design.

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