Measuring and modeling drillstring vibrations with top drive and near-bit sensors

In drill-bit generated seismic, understanding propagation of drillstring vibrations is a key factor for successful processing and interpretation. These vibrations are measured by the pilot sensors located at the top drive or down hole. Different sensor positions in the drillstring give rise to distinct drillstring-related arrivals. Using a unique dataset that contains recordings of both top drive and downhole sensors, we conduct a modelling-based analysis of the vibrations recorded in the first DrillCAM field trial. We analyze the extensional waves recorded on the vertical component and identify the main drillstring-related multiple waves recorded on the top drive and downhole signal autocorrelations. We also analyze the dependence of the top drive signal on the type of drilling bit by comparing the records from roller-cone and polycrystalline diamond compact (PDC) bits. While PDC bits tend to produce relatively weak signals at depth, we observe notable exceptions.