Abstract
Seismic While Drilling (SWD) technology provides a means to properly locate a well path with respect to depth and seismic travel time in order that the driller can effectively guide the bit toward a seismically-defined target. SWD can also facilitate drilling decisions such as setting coring and casing points, avoiding drilling hazards, and identifying overpressure-zones .
Accurate and reliable SWD tools must address at least two main issues: sensor coupling/fidelity, and precision timing. These issues must be addressed within the framework of the drilling environment, whose rigors impose significant constraints on the design and mounting of the seismic sensors and on the accuracy of the clock.
A next-generation SWD tool has been developed that addresses coupling issues through the deployment of multiple, multi-axis sensors, including ruggedized geophones, seismic accelerometers, and hydrophones, in combination with a novel, highly accurate clock and contingent surface systems. This paper investigates the performance of the new tool design and presents the results of field tests and operations in which seismic data were acquired using multiple sensors and types of sensors in various types of formations and in deviated boreholes. The data acquired while drilling are compared to baseline commercial wireline VSP measurements in order to verify that the system provides accuracy comparable to that of a standard commercial wireline.
