Abstract
Targeting deep reach laterals in vibration prone interbedded abrasive sandstones requires multiple bits to complete the prolific pay zones in Central USA. Excessive cutter wear coupled with extreme torque fluctuation in such targets results in reduced ROP and premature failure of BHA components. Early POOH leads to 24 to 48 hours of non-productive time due to BHA tripping. This puts huge economic risk on such challenging pay zones. This study exhibits detailed analysis of downhole and in-bit sensing data to increase the operational stability window enabling enhanced bit durability and smoother drilling conditions for economic drilling of long laterals.
The proposed bit's operation optimization framework is built using a detailed analysis for an in-bit high-frequency sensing gyro and accelerometers data correlated to the geo-steering unit vibrational and Gamma-ray data. The data analysis identified High-Frequency Torsional Oscillation (HFTO) prone formations and HFTO event frequencies, amplitudes and durations while drilling through lithologies with different rock strengths. The findings from the analysis of the field data are cross referenced to the bit response in lab experiments using in-bit sensing while drilling custom built rock cores under high confinement pressure. The result of this work is used to accurately model the drill bit performance to develop best practices to operate them. An operational stability map and a drilling guideline were built and communicated with the region for longer reach and stable drilling.
The data analysis showed a correlation between the lithology shaleness factor and the bits susceptibility to trigger HFTO among other vibrational events. The higher the shale content on the GR track the lower the HFTO excitation probability. These findings were mirrored in the lab while drilling interbedded cores at high confining pressure and it was used to calibrate our drilling models for bit optimization. The application of the drilling guidelines on operating 9 bits resulted in a total savings of $500K per well and 4 days less of non-productive tripping. The guided drilling practices increased the drilled footage per bit by 50%, while reaching the same dull state as previous runs. The control of the bit HFTO and vibrational response decreased the frequency of premature BHA equipment failure enabling longer intervals and less unnecessary tripping.
The absence of wire line logging in long reach laterals limits the understanding of targeted zones. This framework enables gaining deeper formation insights that unlock the optimization of capable drill bits. The adoption of such practice is promising longer footage per bit, less downhole vibrational issues, and economic completion of challenging interbedded abrasive across the world.
