--> Abstract: Reservoir Compartmentalisation and Lateral Drainage from Multiple-Scales: Evidence from Pressure Datasets, by Stephen A. O'Connor, Richard Swarbrick, Phillip Clegg, and David Scott; #90082 (2008)

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Reservoir Compartmentalisation and Lateral Drainage from Multiple-Scales: Evidence from Pressure Datasets

Stephen A. O'Connor, Richard Swarbrick, Phillip Clegg, and David Scott
Geopressure Technology, Durham, United Kingdom

Reservoir compartments can be defined by both vertical and lateral seals. Vertical seals are commonly low-permeability sediments such as salt and/or shales and diagenetic fronts. Lateral seals are usually faults which form effective static boundaries, where sealing potential is a function of clay volume, cement, time and stress. Other lateral seals include stratigraphic shale-out and diagenetic changes in the rock. Virgin (non-production) pressure data can be utilised in conjunction with structural mapping to identify these static boundaries and better understand reservoir connectivity.

The Jurassic sediments of the Halten Terrace, Mid-Norway region of the North Sea are ideally suited to the integration of pressure data with structural maps due to the high data quality. Using regional pressure gradients, defined by direct pressure measurements in isolated, deep-water reservoirs as a guide to expected pressures with increasing depth, rapid changes in pressure can be seen in these reservoirs, both horizontally and laterally. Also, large pressure differences across seals, defining distinct pressure cells are observed. Many of the pressure cells have significantly different magnitudes of pressure at the same depth, implying pressure dissipation via lateral drainage has occurred in a non-uniform distribution throughout the region, at varying scales from sub-basinal to intra-reservoir.

The identification of these pressure cells is key to the understanding of fluid flow (driven by overpressure gradients) and fault seal in the region and provide key learning’s that can be applied in other basins worldwide. The implications for hydrocarbon prospectivity in such basins include the identification of hydrodynamic traps, estimation of column heights (as a result of pressure differences across seals) and pressure isolation of reservoirs and hence drilling risk.

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