Automatic Depth Shifting by Identifying and Matching Events on Well Logs Chicheng Xu

Abstract

Depth matching or depth shifting between well logs acquired from different runs or between core scans and well logs is a critical data quality control task to ensure subsequent accurate petrophysical interpretation and modeling. Conventional depth-shifting workflow heavily relies on human expertise to manually match a series of peaks and troughs between log curves, which is often subjective, error-prone, and cumbersome. Therefore, it is necessary to establish an automatic depth-shifting workflow to perform this routine yet important task accurately in a consistent and efficient manner. We implemented an automatic workflow to emulate human expertise to identify important “events” such as peaks, troughs, and bed boundaries on log curves and then intelligently match the identified series of events between log curves with local maximum correlation criteria to generate a depth shift table. We applied the automatic workflow in a field case to shift the well log and core gamma ray and delivered a depth shift table comparable to manual depth matching. The final shifted log achieved a significantly enhanced correlation with the reference log. The events identifying and matching method presents a white-box solution that still follows the conventional petrophysical wisdom and allows more user interaction to fine-tune the results. The users have full control of the parameters for optimal results.