A New Measurement with World's First At-Bit Imaging

Abstract Formation imaging at the drill-bit is a disruptive measurement being introduced to aid in subsurface characterization and drilling geomechanics while drilling a well. This paper presents the methodology, lab experiments and early field-test results from this new measurement that is independent of drilling environment (mud type/ hole-size/ salinity/ mud-wt.) and type of formation being drilled. At-bit hardware is designed and installed in a polycrystalline diamond compact (PDC) drill bit as part of its cutting structure. The system collects data while drilling translating the forces of cutter interaction with the rock into azimuthal measurement of formation response. The raw data is processed to generate a borehole image for formation characterization and rock properties qualification. Subsurface layering, dips, fractures and textural details can be observed and resulting borehole image can be introduced in any interpretation workflows. This work presents the results from lab-tests performed on the rock-samples, followed by field tests in two different geological settings. The lab experimentations encouraged to deploy the technology in field-test based on the geological observations of layering and fractures. The first field test of at-bit imager also had logging while drilling (LWD) ultrasonic imager in the same drilling bottom-hole assembly (BHA) for comparison, in addition to a wireline run of borehole imager. Results illustrate that at-bit imager could achieve higher fidelity and resolution than industry standard wireline imager, leaving behind the ultrasonic imager by a big margin while acquiring subtle details of textural variations in addition to regular bedding and sedimentary features. Second field test was performed independently, and the images provided excellent validation with offset well and field information for sedimentary features. Meticulously articulated design, detailed lab-experiments followed by rigorous field-test resulted in introduction of a new measurement at the drill-bit providing a unique formation imaging capability. This is first of its kind technology, independent of drilling environment and formation characteristics.