Rank Wildcat Drilling Risks Drilling Time Reduced in Ultra Deepwater Offshore Namibia with the Application of Seismic Formation Pressure While Drilling Technology

摘要

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 his 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. n 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 rend lines to be calibrated reducing the uncertainty in the pore pressure model ahead of the bit. Uncertainty in depth of argets and modeled pressure ramps ahead of the bit were further reduced with the Seismic data.