UNSTEAD, PETER, and RICHARD KEECH,* Shell Internationale Petroleum Maatschappij B.V., The Hague, Netherlands; and JOE WANOGHO-ONUNKETE, Shell Petroleum Development Company, Lagos, Nigeria

ABSTRACT: Forcados Yokri: An Example of a New Approach to Fault Mapping

Forcados Yokri is a mature producing field in the western part of the Niger Delta. The field was discovered in 1968 and commenced production in 1971. A recent three-dimensional seismic survey has significantly changed the structural picture of this mature field. Key horizons and fault planes have been interpreted. CPS-3 and the Radian Full Fault Modeling System (FFMS) have been used to complete the structural mapping using inclined faults and to calculate accurate volumetrics. More consistent infill maps have been obtained, and volumetrics indicate that up to 3% can be found behind the footwalls of the fault planes.

The FFMS module has been designed to address three main problems in computer mapping: (1) horizon mapping with inclined fault planes, (2) automated isochore stacking for infill horizons, and (3) volumetrics in an inclined fault system.

Data exchange between the seismic workstations and CPS-3 for FFMS has been the main problem. This has been investigated and improved. Further developments for the system focus on process improvements in data exchange and in technical additions such as cross fault sand-to-sand juxtaposition.

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