Seismic while-drilling technology: use and analysis of the drill-bit seismic source in a cross-hole survey

> Multicomponent seismic while-drilling data were analysed in order to define better the different wavefield components and the energy radiation pattern of a tricone drill-bit. A unique cross-hole acquisition scheme from one of ENI-AGIP's special test sites was used. Direct measurements of high quality P- and S-waves allowed the determination of the radial horizontal component (HR) and of the corresponding transverse horizontal component (HT). Subsequently, analysis of the vertical transverse component (T), derived by combining Z and HR. led to the computation of simplified radiation pattern for the SV component of the drill-bit signal. A large time splitting between horizontally and vertically polarized shear waves, influenced by the acquisition geometry and by the geological setting, was analysed. An unconventional SV velocity tomographic reconstruction from the drill-bit signal is also derived and discussed.

Multicomponent seismic while-drilling data were analysed in order to define better the different wavefield components and the energy radiation pattern of a tricone drill-bit. A unique cross-hole acquisition scheme from one of ENI-AGIP's special test sites was used. Direct measurements of high quality P- and S-waves allowed the determination of the radial horizontal component (HR) and of the corresponding transverse horizontal component (HT). Subsequently, analysis of the vertical transverse component (T), derived by combining Z and HR, led to the computation of a simplified radiation pattern for the SV component of the drill-bit signal. A large time splitting between horizontally and vertically polarized shear waves, influenced by the acquisition geometry and by the geological setting, was analysed. An unconventional SV velocity tomographic reconstruction from the drill-bit signal is also derived and discussed. Multicomponent seismic while-drilling data were analyzed in order to define better the different wavefield components and the energy radiation pattern of a tricone drill-bit. A unique cross-hole acquisition scheme from one of ENI-AGIP's special test sites was used. Direct measurements of high quality P- and S-waves allowed the determination of the radial horizontal component (HR) and of the corresponding transverse horizontal component (HT). Subsequently, analysis of the vertical transverse component (T), derived by combining Z and HR, led to the computation of a simplified radiation pattern for the SV component of the drill-bit signal. A large time splitting between horizontally and vertically polarized shear waves, influenced by the acquisition geometry and by the geological setting, was analyzed. An unconventional SV velocity tomographic reconstruction from the drill-bit signal is also derived and discussed.