The operator’s principal objective was to implement the WPQC to ensure accurate wellbore positioning to enhance safety and to reduce the uncertainty ellipses during drilling. Continuous monitoring and verification of the well’s trajectory during drilling is essential to reduce uncertainty and facilitate timely decision making in geosteering. This alignment with the directional program ensures timely corrections when necessary. In presalt wells, the challenge of drilling through salt layers complicates contingency operations, highlighting the critical importance of reducing well position uncertainty for agile decision making and risk mitigation.
After acquiring directional data from the Quest GWD tool and MWD, the WPQC was implemented by comparing the directional data from both tools using an analytical methodology. This included a relative instrument performance test, a chi-square test, and a comparison of uncertainty ellipses at the same depth.
This approach enabled real-time verification of the accuracy of the error models applied to both tools and reduced the uncertainty ellipse area by 75% compared with MWD. A comprehensive analysis document detailing the results was rapidly communicated to the drilling team.
Upon reaching TD in the 17½-in section, the Omega Gyro gyroscope was deployed into the well performing surveys during the column pull, utilizing the memory mode to ensure directional data acquisition without adding time to the operation. The Quest GWD tool reduced the uncertainty ellipse by 68.85% in real-time at 4,450 m compared to MWD. The Omega Gyro tool achieved a 75.20% reduction at 4,476 m. These results confirm there were no gross errors with the MWD surveys and demonstrate the benefits of comparing and utilizing both surveys from the magnetic and gyroscopic tools, creating a quality assurance system in well-positioning uncertainty calculations.
