Using Seismic-While-Drilling (SWD) Data to Assist in Selecting Casing Depths: Case Histories: ABSTRACT

Abstract

Drill-bit source VSP surveys have been used to successfully tie seismic events to driller's depths during the drilling of wells. Fully processed data sections obtained with the drill-bit source technique can be deconvolved to a reflected wave-field section for estimating the depth of seismic events that occur deeper than the drill bit. Using extrapolated measured velocities, or other velocity data, predictions of depths to the seismic horizon of concern can be made. In the case studies presented, the seismic events were correlated to indicated casing depths from drilling experience on offset wells. Poor velocity control at the proposed location made SWD estimates of depth to casing point extremely valuable. The paper presents the basic principles of SWD, the processing of the data at the well site, and the technique of tie-in to surface seismic for making explicit predictions of depth to seismic horizons ahead of the bit.