RESERVOIR GEOLOGICAL MODELLING OF THE NORTH RANKIN FIELD, NORTHWEST AUSTRALIA

Abstract

The North Rankin Field off northwestern Australia provides the major part of the gas reserves for the North West Shelf Project, one of the largest and most ambitious natural resource developments yet undertaken in Australia. Detailed reservoir geological modelling coupled with a three dimensional reservoir simulator have strongly enhanced development planning of the field.

The North Rankin structure is a large horst feature of Upper Triassic to Lower Jurassic fluvial and marginal marine sediments unconformably overlain by Cretaceous claystones and marls. The sequence is comprised of braided stream 'sheet like' sandstones, fluvial meandering stream and floodplain sediments, and mixed marginal marine and fluvial channel sandstones.

Comprehensive reservoir geological studies involving the examination of reservoir quality, distribution, and continuity were undertaken and combined with an extensive three dimensional seismic survey to provide improved structural definition. The resultant reservoir geological model, which required close interaction and integration of all petroleum engineering disciplines, provided not only the geological basis for improving the estimate of field reserves but also formed the geological input for a reservoir simulation model to optimise the development planning of the North Rankin Field and to predict the reservoir performance of this internally faulted field.

The completion of the Domestic Gas Phase of the Project, which involved the drilling of seven development wells, has confirmed the reservoir geological/structural model thus providing a firm basis for the future development planning of the gas recycling and liquefied natural gas phases of the North West Shelf Project.