Abstract

The exploitation of a thin oil column overlain by a large gas cap, and underlain by a huge aquifer by horizontal wells is challenging due to an early development of gas and water crests. This paper examines a strategy for alleviating the excessive production of gas and water by controlling the movement of fluid interfaces. This is achieved by withdrawing gas cap gas, and aquifer water, by means of separate horizontal completions, one each in the gas cap and in the aquifer, which are parallel and aligned with the oil zone completion. The gas cap gas, aquifer water, and oil are produced through separate strings. The high-pressure gas can be sold or utilized, and the produced water can be disposed of at the surface or subsurface.

The simulation results indicate an increase in the oil reserves to the extent of 25–50% over a conventional horizontal well for different ratios of vertical to horizontal permeability, over a 5 years period. The proposed system offers a relatively easy effluent handling, and sustained production of normal GOR, low water-cut oil for a longer duration of time. Proper well steering, completion, and its maintenance are identified as keys to the economic success of the strategy

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