Probabilistic Model-Based Evaluation of Volumetric and Connectivity Uncertainty, Humma Marrat Reservoir, Partitioned Neutral Zone (PNZ)

W. Scott Meddaugh¹, Stewart Griest¹, Stephen Gross¹, and David Barge^2
1 ChevronTexaco Energy Technology Company, Bellaire, TX
² Joint Operations, Wafra, Kuwait

The Jurassic-age Humma Marrat reservoir in the southwest Partitioned Neutral Zone was evaluated using a design of experiments (DoE) workflow. The Humma Marrat reservoir was discovered in 1998. Porosity in productive zones is 8-20% and permeability is generally less than 20 md. The dolomitized lowermost Marrat “E” interval is the most porous and permeable zone. Fractures may be important in the uppermost limestone Marrat “A” zone.

The first level DoE used drained volume as the experimental response. Uncertainty sources evaluated were structure (velocity model), original oil-water contact (OOWC), facies distribution, porosity and water saturation histograms, porosity semivariogram, fault compartmentalization and transmissibility, and permeability multiplier. Drained volume results were obtained via finite difference fluid flow simulation of up-scaled geostatistical reservoir models defined using a Plackett-Burman experimental design. The only significant uncertainty sources for drained volume were the porosity histogram and permeability multiplier. The OOWC and porosity histogram were the most significant contributors to volumetric-only uncertainty. P10, P50, and P90 earth models were defined for use in the second level DoE.

The second level DoE evaluated dynamic uncertainty elements using cumulative oil production as the response variable. The uncertainty sources evaluated were earth model, aquifer support, rock compressibility, heavy oil distribution, Kv/Kh, PI multiplier, Sorw, and Krw. The results showed that the earth model and PI multiplier were the significant contributors to the cumulative oil production uncertainty. The second level DoE work was used to define P10, P50, and P90 flow simulation models used for subsequent reservoir optimization studies and economic forecasts.

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