Research Note: Automated data‐driven alignment of near‐bit and top‐drive vibration sensors for seismic while drilling and beyond

Abstract

Downhole near‐bit vibration sensors are used to record the pilot signal for seismic while drilling and identify drilling dysfunctions for drilling optimization. The typical downhole sensor is a memory‐based device with an inexpensive internal clock of limited accuracy that is not synchronized to surface data. Integrating downhole vibrations with other time‐based data such as surface drilling parameters or seismic recordings requires accurate time alignment between all data sets. We present a novel automated two‐step alignment procedure that uses a Global Positioning System‐synchronized top‐drive vibration sensor as a reference. The accuracy of the new method satisfies the most demanding requirements of seismic while drilling. The first step finds the delay time and linear drift using global optimization. The second step estimates nonlinear drift using time‐variant cross‐correlation. Alignment precision of a few seconds after the first step becomes a few milliseconds after the second step, as demanded by seismic‐while‐drilling. The field data example shows that the proposed methodology successfully aligns top‐drive and downhole data using a fully unsynchronized near‐bit vibration data set. After alignment, the near‐bit sensor delivers a usable pilot for seismic‐while‐drilling processing, resulting in better quality correlated seismic data than those obtained with the top‐drive surface pilot.