Andrew Integrated Reservoir Description

Simon P. Todd

The Andrew field is an oil and gas accumulation in Paleocene deep marine sands in the Central North Sea. It is currently being developed with mainly horizontal oil producers. Because of the field's relatively small reserves (mean 118 mmbbls), the performance of each of the 10 or so horizontal wells is highly important. Reservoir description work at sanction time concentrated on supporting the case that the field could be developed commercially with the minimum number of wells. The present Integrated Reservoir Description (IRD) is focussed on delivering the next level of detail that will impact the understanding of the local reservoir architecture and dynamic performance of each well.

Highlights of Andrew IRD Include:

-- Use of a Reservoir Uncertainty Statement (RUS) developed at sanction time to focus the descriptive effort of both asset, support and contract petrotechnical staff;

-- High resolution biostratigraphic correlation to support confident zonation of the reservoir;

-- Detailed sedimentological analysis of the core including the use of dipmeter to interpret channel/sheet architecture to provide new insights into reservoir heterogeneity;

-- Integrated petrographical and petrophysical investigation of the controls on Sw-Height and relative permeability of water;

-- Fluids description using oil geochemistry and Residual Salt Analysis Sr isotope studies.

Andrew IRD has highlighted several important risks to well performance, including the influence of more heterolithic intervals on gas breakthrough and the controls on water coning exerted by suppressed water relative permeability in the transition zone.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California