HOULLEBERGHS, ERIC, Nederlandse Aardolie Maatschappij, Velsen, Netherlands, PATRICK HALTMEIER, Shell Turkey, Diyarbakir, Turkey, and JAN VAN DE SANDE, Nederlandse Aardolie Maatschappij, Assen, Netherlands

ABSTRACT: Use of Prediction Techniques in an Integrated Study of the L5 Field, Offshore Netherlands

Seismic imaging provides a powerful tool for a variety of development applications. While defining development locations in the L5-FA gas field, the project team was confronted with the question: do seismic images accurately reflect the quality of the reservoir? Careful integration of the seismic data with the geological information supplied the answer to this problem.

The L5-FA field is situated in the southwestern part of the Central Graben in the Dutch sector of the North Sea. The Volpriehausen reservoir consists of thin but widespread alluvial/aeolian sandsheets alternating with silty claystones.

A geophysical modeling exercise, characterized by an iterative process of merging the geological data, reservoir geological models, and the three-dimensional seismic data set into one coherent picture was initiated. Synthetic reflectivity data were generated for gas-filled reservoirs with a varying average porosity, with different porosity profiles and thickness variations as well as varying overburden parameters. Correlations between different reservoir parameters and a variety of amplitude measurements were investigated. A strong linear relation between porosity and amplitude extremum for the porosity range 5-18% was one of the outcomes of the study. Amplitudes were measured on the top and base Volpriehausen reflections. After well calibration, an average porosity map was compiled.< P>

Based on this map, two development well locations were picked in the more prolific part of the reservoir.

Although subsequent drilling proved the mapped porosities to be correct, there is still a major challenge to be met: a further integration of all available information, including, for instance, production data. Only then we will fully understand the reservoir architecture.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.