Reservoir: Do We Still Need Pseudo-Relative Permeability?
The oil industry continues to experience a trend toward assessing and developing reservoirs which are more difficult to characterize and to produce. Deepwater turbidites are an important example of this trend. In addition to their architectural complexity some of these reservoirs contain substantial volumes of heterolithic facies which may require non-conventional approaches to characterize and model. The use of pseudo-relative permeability curves has recently been shown to be helpful for history matching a key deepwater turbidite reservoir with a significant volume of heterolithic facies which is currently under waterflood operations in the offshore area of Equatorial Guinea.
Realistic lamina scale conceptual models for the heterolithic facies were generated which were consistent with all static and dynamic data resulting from a careful data collection program. Producing profiles were obtained from reservoir simulation of these lamina scale models which used conventional oil-water relative permeability curves from laboratory experiments. However, following the scale up the resulting producing profiles were found not to correspond with the profiles from the lamina scale models. Pseudo-relative permeability curves were subsequently generated for use with the scaled-up models in order to better match the profiles observed in the lamina scale conceptual models.
For the actual history match of a key reservoir in the field, the heterolithic facies were allowed to use either pseudo-relative permeability curves or laboratory based relative permeability curves. However, the more conventional facies were only allowed to use the laboratory based relative permeability curves. The pseudo-relative permeability curves for the heterolithic facies consistently outperformed the conventional laboratory measured “rock” relative permeability curves in terms of the history match quality. The pseudo-relative permeability curves for the heterolithic facies were thus selected for the final models. This finding suggests that pseudo-relative permeability curves are still useful for certain reservoir characterization and modeling applications.
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