A Production-Based Sequence Stratigraphic Framework is the Key for Optimal Oil Recovery on Mature Fields: Examples from the Statfjord Field of the North Sea, Norway

Pierre Theriault
Statoil, Stavanger, Norway

Software developments in 3D geomodeling and 3D visualisation are increasingly attractive to the reservoir geoscientist, providing him with tools that facilitate the well planning and real-time evalution processes. However, there is a overhanging danger that the basic reservoir geology data that forms the framework for decision-making can be overlooked in the face of fancy software and displays. This presentation shows, through established work processes and case examples from the Statfjord Field of offshore Norway, the value of establishing and actively using a high resolution stratigraphic framework on mature fields.

The targeting remaining oil process (TRO process) on the Statfjord Field has proven to be a valuable method for identifying and maturing remaining pockets of oil. Both conventional and time-lapse seismic, flood-front monitoring, and sedimentological / sequence stratigraphic understanding and are key elements involved. When it comes to the planning of new wells, our experience from the fluvial Statfjord Formation, the marginal-marine Ness Formation, and the delta-front Rannoch Formation shows that a high resolution sequence stratigraphic framework is the basis for correct decisions and correct assessment of volumetrics. During drilling, real-time data and use of 3D visualisation are major assets for geosteering, but equally important is the careful evaluation of the incoming well data with respect to the sequence stratigraphic framework. Finally, well interventions need to be supported by an adequate geological understanding of the reservoir. The mature stage of the Statfjord Field is such that the completion strategy is best established by interaction between the production engineer's PI and fluid-flow estimates, the reservoir engineer's understanding of the production history, and the geologist's representation of the high resolution stratigraphic framework and interwell architecture.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005