Simon A. Smith
Quantitative 3-D geological models of Shell's Niger delta reservoirs are now routinely used for well and field development planning, simulation input and reserves booking. A review of these models, built with Shell's reservoir modelling package Geocap, has highlighted the successes and potential pitfalls of 3D reservoir modelling and has led to a template for better modelling of wave-dominated deltaic reservoirs.
The key issues fall into two categories. The first concerns the use of "soft" geological knowledge. Conceptual models are a prerequisite for quality 3-D reservoir models and meaningful results can be obtained only if the geologist has a mental 3-D picture(s) of the reservoir which is used to steer the modelling. The decision to use stochastic techniques is crucial. In wave-dominated deltaic reservoirs, uncertainty may be better handled by a series of deterministic scenarios rather than many stochastic realisations. Sequence stratigraphic correlation tools and the definition of meaningful and recognisable facies types and flow units also determine the quality of the model.
Integration between the petroleum engineering disciplines is the second category. The interface with the reservoir engineer is particularly important; the relevant level of geological detail must be identified and preserved during upscaling and flow simulation. Reservoir engineering and seismological data must be used to refine or validate alternative scenarios in an iterative loop. 3-D modelling is a tremendous business opportunity, but it demands more geological skills as well as a fully integrated, multidisciplinary approach.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California