Rank wildcat wells in Ultra deepwaterD- present some of the greatest challenges today. Decision making during drilling is challenging due to a lack of offset well data. 3D Surface seismic data has significant uncertainty from the translation of two-way time to horizon depths which further induces risk into the predrill pore pressure model. This paper looks in detail at how the utilization of a high-tech logging while drilling suite in the execution of a rank wildcat enabled key drilling decisions to be made, reducing risk and time vs. depth plan the well. Seismic while drilling technology guided drilling in each section from spudding to total depth by allowing up to 600 m look ahead. This reduced target depths uncertainty from +/-100 meters to less than +/-5meters. Furthermore it permittedallowed this complex S-shaped well trajectory to avoid accidental penetration into the first target avoiding well control situation, placing the 13 3/8?? casing shoe safely above the first target, 80m shallower than planned. This ensured an increased mud weight window for the 12.25?? section. In the 12.25?? section, Formation Pressure While Drilling Technology was added to the Seismic and Sonic technologies to calibrate the pre drill pore pressure model. This was critical due to a narrow mud weight. The acquired formation pressures coupled with while drilling petrophysical data allowed for the pore pressure to velocity transform and normal compaction trend lines to be calibrated reducing the uncertainty in the pore pressure model ahead of the bit. Uncertainty in depth of targets and modeled pressure ramps ahead of the bit were further reduced with the Seismic data.

No abstract

When drilling in remote areas, in the absence of offset data, pore pressure is determined as a function of seismic rock velocity. The velocity model and corresponding pore pressure model form the basis for exploration well planning. These models directly impact the casing design, number of sections, and mud weight plan. For frontier exploration drilling, the relationship is not well established; this reliance is high risk and can benefit from a high-technology approach to reduce this risk. This study examines how velocity and pressure models updated using real-time measurements from a high-tech logging-while-drilling suite can enable key drilling decisions to be made, reducing risk and the time taken to drill the well. Seismic-while-drilling technology provides checkshot data while drilling, which is used to update the velocity model. The velocity model updates in the shallow sections allow modification to the forward trajectory to ensure targets are intercepted. Furthermore, real-time updates enable geostopping by refining the predicted depths of targets or marker horizons and ensuring no accidental penetration of bright seismic amplitudes that may be associated with potential pore pressure abnormalities. In addition, formation-pressure-while-drilling technology can be added to the seismic and sonic technologies to calibrate the predrill pore pressure model. The acquired formation pressures, coupled with the while-drilling petrophysical data, allow for the velocity to pore pressure transform and normal compaction trend lines to be calibrated and reduce the uncertainty of the pore pressure model ahead of the bit. The calibrated models permit the operator to confidently make decisions and continue drilling in a single section to intercept key targets, potentially eliminating casing strings, with the assurance that the kick tolerance and safe overbalance are maintained at an optimal level to reduce the risk of mud losses or kicks.