facies interpretation from well logs: applied to calub–hilala field within ogaden basin, ethiopia

the lithofacies and environments of deposition interpretations of the calub–hilala field toward the central trough of ogaden basin were analyzed, and geophysical well logs from three deep exploration wells, namely calub-1, bodle-1, and hilala-2, were used. a methodology was piloted in establishing the sedimentary facies, their successions, and environments of deposition. gamma-ray, neutron, sonic, and resistivity logs were used for lithologic and depositional environment identification. an attempt was also made to identify formation tops and well-to-well lithostratigraphic correlation basing gamma-ray log trends and correlate with the cored interval of the wells for lithological comparisons. lithofacies interpretation was carried out with schlumberger’s petrel software, version 2009. correlation techniques were conducted to delineate the subsurface trends of these facies with electrofacies to compare facies interpretation results that were implied using the wireline log signatures. ten formations, namely calub, bokh, gumburo, adigrat, transition, hamanlei (lower, middle, and upper), urandab, gebredare, gorrahei, mustahil, and five log facies, namely a cylindrical-shaped log trend representing aeolian, i.e., braded fluvial, a funnel-shaped facies representing a crevasse splay, a carbonate, shallowing upward sequence and shallow marine sheet sand, a bell-shaped facies representing transgressive marine shelf, a symmetrical-shaped facies representing sandy offshore, and an irregular shaped facies representing fluvial floodplain, were recognized. the environments of deposition delineated for the study area are alluvial and transgressive–regressive marine.