Geobody Modelling and Reservoir Characterization of Siliciclastic Wara Formation in Khashman Field, Kuwait

Exploration of Middle Cretaceous Wara Formation in Khashman area started in 1960s and till date ten wells were drilled of which two had produced hydrocarbon. Facies architecture and reservoir properties prediction are major exploration challenges. On the basis of 3D Pre-Stack Time-Migrated seismic data, the present study applied new technologies to integrate seismic attributes and well data. The study came up with geobody modeling and reservoir characterization of Wara Formation, which helped to identify new drillable prospects.

Sequence Stratigraphic framework and depositional environment of Wara Formation (around 200ft thick) are interpreted by integrating core and well logs and envisaged fluvio-deltaic deposits within a Lowstand Systems Tract.

3D seismic attribute volumes viz. Spectral Decomposition, Instantaneous Sweetness and Relative Acoustic Impedance were generated in frequency and depth domain at Wara interval. Calibrated by litho-facies at the well locations, geobodies (channel sand) are identified in seismic-attribute volumes in the depth domain and subsequently extracted from correndered attribute volumes by using Neural Network technique. Extracted geobodies were modeled to incorporate inside 3D structural model. Modeled geobodies show geometry and orientation of channel sand inside Wara Formation across Khashman Field. Subsequently the geobody was integrated with upscaled facies logs to populate facies in areas adjoining to geobody using stochastic simulation. Porosity and Water Saturation (Sw) logs were upscaled guided by facies model and then stochastically populated in the model.

Wara Facies model could delineate geometry, orientation and areal continuity of sand bodies. Facies model predicts stacked channel sand with areal continuity and sand lenses with limited continuity and pinchouts. Porosity and Sw model predict isolated sand lenses have maximum 20% porosity and high Sw (50-70%) while stacked sand layers have maximum 35% porosity and low to moderate Sw (20-40%). Siltstone with low porosity (5-10%) and very high Sw (60-80%) has marginal reservoir potential.

Present study helped in understanding Wara facies architecture and prediction of reservoir facies and properties in Khashman Field. The study has identified potential unexplored drillable prospects for Wara Formation in Khashman Field. Successful drilling of identified prospects could add substantial reserve in Wara Formation.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California