Abstract: A Toolbox for Early Identification of Reservoir Compartmentalization, Case study: An Integrated Appraisal of the Ross Field, UKCS

P. Craig Smalley, Nick Hale

The Ross Field (Moray Finh, UKCS) contains oil in Jurassic sandstones. An appraisal dataset of 10 wells and a 1991 3-D survey exists in an area of 60 sq km. Commerciality depends on the number of wells needed to access the oil. One principal uncertainty is the degree of reservoir compartmentalization: whether faults seen on seismic are sealing, or shales seen in wells are laterally extensive. In the absence of dynamic data, an integrated package of 10 geotechnical tools has been applied to the appraisal wells in the Ross field to reduce this uncertainty: (1) RFT pressure analysis; (2) oil maturity analysis of DST oils; (3) geochemistry of oil core extracts; (4) statistics analysis of oil gas chromatograph data (GC fingerprinting); (5) PVT data analysis; (6) well tests; (7) fault throw analysis; (8) sedimentological description: (9) Sr fingerprinting of water compositions from core; (10) sequence stratigraphy. This combination of novel and conventional tools is useful as a general template for early assessment of reservoir complexity in field appraisal.

Several fault-bounded reservoir compartments were identified in Ross. A shale was also identified as a barrier to vertical fluid flow over a 5 sq km area. Each of the 10 tools applied on its own only told a small part of the story, but putting them together provided an assessment of reservoir compartmentalization capable of predicting future dynamic performance. This has allowed a more realistic representation of the reservoir complexity in the full-field simulation model and will be an important factor in locating development wells.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994