WEBER, K. J., Shell International Petroleum Corp., The Hague, The Netherlands

ABSTRACT: Enhanced Reservoir Definition for Increased Production

New production techniques such as the use of horizontal holes for drainage and injection purposes, require more detailed and accurate reservoir characterization. Three main methods have reached an advanced state of application, viz. 3D seismic, computerized reservoir modeling using geostatistical theories and advanced correlation techniques and the use of outcrop data to provide reservoir analog models.

Of particular importance is the construction of realistic reservoir models at the earliest opportunity. However, also for old fields, a modern approach with a new phase of data gathering will often reveal hidden reserves and a wide scope for recompletion and infill drilling.

Usually is it the combined use of several methods that is most effective. Probablistic reservoir modeling systems may be very sophisticated, their use is restricted to those environments of deposition for which one possesses a sufficient statistical data base of sand body geometry and interrelationships. Such models can be significantly constrained if sand body contours and pore fill can be detected on seismic sections and amplitude maps. In favorable cases, the irregular present oil-water contacts can be observed in old fields as well as secondary gas caps.

Detailed geological models consisting of millions of cells have to be scaled-up by a factor of hundred to allow reservoir simulation. Various techniques have been developed to achieve this and to compute grid block parameters that properly account for their internal heterogeneity. The detailed geological models can also be used directly for volumetric computations of original oil-in-place in parts of the reservoir flooded by water or gas. In this way, water saturations revealed by through casing logging in flooded zones can be integrated into the reservoir model to estimate sweep efficiency and to locate the remaining oil.

Thus the applications of these reservoir modeling techniques range from the early appraisal stage to the late life upgrading of old fields. The economic benefits of these methods are remarkable compared to their cost.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.