SANDSTONE RESERVOIR DESCRIPT ION: AN OVERVIEW OF THE ROLE OF GEOLOGY AND

and engineering data. Modelling of reservoir performance is made by creating a three-dimensional model of the reservoir volume, where the reservoir s built of cells and layered zones which are defined geologically. Although the scale of cell size is coarse compared to the scale of geological data, it is important that the geological input to define cells is as precise as possible. The texture of clay minerals and their composition are requisite for understanding their influence on reservoir characteristics. Wireline logs probably do not provide sufficient information about clay mineralogy to evaluate reservoir characteristics, but do allow the extrapolation of 'point' mineralogical data into a continuous reservoir description. Evaluation of porosity, permeability and saturation are described, and the possible influence of clay mineralogy on evaluation of these characteristics s discussed. A multidiscipfinary approach to reservoir description has gained wide acceptance durin