Integrated fault interpretation using well data

Abstract

A standard well logging suite, including borehole seismic, sonic and formation imaging data logged in 2011 on the North-West Shelf of Australia, is shown to provide crucial structural interpretation information when processed in an innovative and integrated way. Initial well logging results indicated that the pre-drill seismic interpretation model was not matching the observations. Geological information from wireline borehole resistivity imaging tools confirmed the presence of many fractured/faulted zones in the well and synthetic seismograms showed that there was a problem tying well information to the surface seismic markers. The acquired rig source vertical seismic profile (VSP) established a good time-depth relation as well as a tie with the other log data. Further analysis of the three component VSP data showed significant and anomalous out of plane seismic events resulting in the proposal of a novel fault analysis workflow. A calibrated 2D model was built and a combination of modelling and VSP dip estimation techniques were used to provide solid indications of a major steeply dipping fault cutting the wellbore. Sonic and borehole imaging data were subsequently analysed providing further support for this interpretation. By combining the processing results of various petrotechnical domains, a coherent and integrated fault interpretation was obtained that significantly altered the initial perception regarding a major fault position and its well intersection. A new 3D interpretation effort is now being undertaken as a result of these new findings. This project demonstrates the value of integration of data processing and interpretation.