Step-out well positioning using hydrocarbon indicators from seismic inversion: a case study

Abstract AVO attributes and especially absolute rock properties from prestack seismic inversion after calibrating to existing production wells are demonstrated to reduce the risk of drilling dry wells. At a mature onshore gas field, step-out well position optimization using inverted rock and reservoir properties to identify sweet spots has been successful. Initial prestack inversion used empirically generated shear sonic logs in the background model. The inversion results indicated a possible commercial gas accumulation in bypassed pay zones, and this was proven by drilling. Log data from this new well, including the shear sonic measurement, was incorporated into the background model. The prestack inversion was rerun and the improved inversion results indicated a new prospect. This has recently been drilled and the well found a 10-m thick gas sand reservoir.