--> Abstract: The Impact of Turbidite Pinchout/Onlap Geometry from Hydrocarbon Recovery in Stratigraphically Trapped Fields, by Andy R. Gardiner, Simon A. Peachey, and Lawrence Amy; #90082 (2008)

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The Impact of Turbidite Pinchout/Onlap Geometry from Hydrocarbon Recovery in Stratigraphically Trapped Fields

Andy R. Gardiner, Simon A. Peachey, and Lawrence Amy
Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh, United Kingdom

Stratigraphic trapping is an important component of many hydrocarbon fields reservoired in deep-water, turbidite deposits. The trapping may occur at channel margins, onlap surfaces and when turbidite sandbodies exhibit lateral variations in sand quality and/or bed thickness. The pinchout/onlap of turbidite sandbodies exhibits a wide range of geometries (of both the sandbody and its component beds) and distributions of reservoir properties.

These variations in geometry and properties will impact the static and dynamic reservoir behaviour. Previous work (Gardiner, 2006) has indicated that, for onlapping layered sandbodies in which the turbidite sandstones have uniform reservoir properties, the optimum well location is a compromise between leaving updip oil and, for wells too close to the onlap termination, leaving oil in the lower part of the sandbody. For sandbodies with continuous shale barriers between individual sandstones, the optimum well position is close to the start of sandbody pinchout and hydrocarbon recovery decreases rapidly either side of this position. However, with progressive erosion of shales, the well position is less critical.

The work presented here extends the initial work to examine the impact of a wider range of reservoir pinchout geometries, including variations in net-to-gross ratio, thinning of individual sandstones and lateral variations of reservoir properties, on both static and dynamic reservoir behaviour.

In many turbidite systems, the fines between individual turbidites may contain significant proportions of silt and so may not act as perfect seals. If the ‘shales’ are given low but finite permeabilities, the impact of complex reservoir geometries is significantly reduced.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery