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There are several challenges for polycrystalline diamond compact (PDC) drill bits when drilling through volcanic and interbedded applications. Roller cone (RC) bits have historically been used in geothermal applications. However, low rate of penetration (ROP), bearing life, and repairability limitations have halted progress in performance and economic gains. This paper presents game-changing PDC technology that addresses the limitations of previous conventional drill bits in a challenging geothermal application. A reimagining of drill bit body geometries, the latest in shaped cutter technology, and durable backup elements were lab tested and customized on an unconventional drill bit chassis to maximize ROP, improve durability, and reduce downhole torque variation. The initial design phase focused on identifying and overcoming these key challenges. The second phase was to field test the new drill bit in the target application and compare it to offset runs, including roller cone, hybrid, and conventional fixed cutter bits. Key performance indices such as ROP, durability, steerability torque generation/variation, and cost per meter (CPM) were considered when evaluating the new design's performance. Initial testing in the 16-in. section showed promising results in the field. Higher-than-average ROP and excellent interval resulted in the lowest cost per meter run. In addition, the drill bit complemented the bottomhole assembly (BHA) design well, as minimal effort was needed to keep the trajectory as planned. The delta torque generation was lower than conventional PDC bits whilst displaying higher ROP than roller cone alternatives. The improved durability of the new design also allowed it to be run multiple times without repair, which was not possible with previous bits due to bearing hours or durability issues. This was always a challenge through the volcanic formations seen in this application. In remote locations that do not have facilities to repair drill bits, the ability to run multiple times without the need to repair is critical. The operator saved costs by not needing to transport the bit and repair any PDC cutters or secondary components after multiple runs. This outstanding run validated the benefits of the new design in terms of both technical and economic perspectives.
There are several challenges for polycrystalline diamond compact (PDC) drill bits when drilling through volcanic and interbedded applications. Roller cone (RC) bits have historically been used in geothermal applications. However, low rate of penetration (ROP), bearing life, and repairability limitations have halted progress in performance and economic gains. This paper presents game-changing PDC technology that addresses the limitations of previous conventional drill bits in a challenging geothermal application. A reimagining of drill bit body geometries, the latest in shaped cutter technology, and durable backup elements were lab tested and customized on an unconventional drill bit chassis to maximize ROP, improve durability, and reduce downhole torque variation. The initial design phase focused on identifying and overcoming these key challenges. The second phase was to field test the new drill bit in the target application and compare it to offset runs, including roller cone, hybrid, and conventional fixed cutter bits. Key performance indices such as ROP, durability, steerability torque generation/variation, and cost per meter (CPM) were considered when evaluating the new design's performance. Initial testing in the 16-in. section showed promising results in the field. Higher-than-average ROP and excellent interval resulted in the lowest cost per meter run. In addition, the drill bit complemented the bottomhole assembly (BHA) design well, as minimal effort was needed to keep the trajectory as planned. The delta torque generation was lower than conventional PDC bits whilst displaying higher ROP than roller cone alternatives. The improved durability of the new design also allowed it to be run multiple times without repair, which was not possible with previous bits due to bearing hours or durability issues. This was always a challenge through the volcanic formations seen in this application. In remote locations that do not have facilities to repair drill bits, the ability to run multiple times without the need to repair is critical. The operator saved costs by not needing to transport the bit and repair any PDC cutters or secondary components after multiple runs. This outstanding run validated the benefits of the new design in terms of both technical and economic perspectives.
Cherty formations are notoriously challenging for fixed cutter drill bits and present a costly challenge for operators who routinely experience short intervals and numerous trips. The predominant limitation is short bit life due to mechanical failure of the cutters. This paper details how an inter-company collaboration led to the development of a design philosophy and a novel shaped cutter technology that resulted in a step change in drilling efficiency and drilling consistency in chert formations. A collaboration between companies was initiated that commenced with a comprehensive study into the cutter-rock interaction to identify the failure mechanism of chert. The results of the research were then used to determine the critical design levers required to overcome these challenges, extended bit life and maximize drilling efficiency. Two fixed cutter drill bits in the 6-in. and 8.5-in. hole sizes that incorporated the new design philosophy and shaped cutter technology were designed. These bits were then field tested in the Egypt Gulf of Suez interbedded carbonates application characterized with the presence of dark brown chert. The new 6-in. and 8.5-in. designs were tested twelve times across four different fields. The runs were then evaluated against durability, rate of penetration (ROP) and cost per foot (CPF) compared to field offsets. In the 6 in. section, the new design drilled the entire section of 3,369-ft that includes 381-ft cherty formation with one bit compared to three bits previously required to drill the same interval. For the same offsets, an improvement of between 50-85% in ROP was achieved. The CPF assessment demonstrated drilling cost reduction between 24-75% across the fields tested. In the 8½ in. section, the new design drilled the entire section of 6,141 ft that includes 296-ft cherty formation with one bit compared to four bits previously required to drill the same interval. ROP wise, an improvement between 59-178% was achieved which corresponded to a CPF reduction of between 41-69% across the fields tested. These field tests demonstrate ground-breaking results in the durability, ROP and CPF performance metrics measured. Furthermore, the number of runs and diverse nature of the fields tested demonstrate the consistency of this new approach to drill cherty formations with full directional control and mitigating downhole vibration severity. A re-examination of the failure mechanism of chert drilling and the root cause behind drilling deficiencies in cherty applications conducted in a collaborative environment has paved the way for a step change in drilling performance. Novel design philosophies were created, laboratory tested, and field validated for consistency of the trials. As the drilling industry continues to explore unchartered applications to ensures cost efficient solutions is paramount to success
Hard and abrasive formations are commonly found in challenging Middle East reservoir sections. These sections are often drilled with up to 10 bits, driving up drilling costs. Low rate of penetration (ROP) and accelerated cutter wear are the primary failure mechanisms encountered. Conventional drill bits have proven unsuitable and uneconomical. This paper presents the development of a Polycrystalline Diamond Compact (PDC) cutter grade housed in a rotating mechanism that has resulted in ground-breaking drilling efficiencies in these formations. A comprehensive study investigated the cutter-rock interaction and identified the underlying causes behind the accelerated cutter wear in these hard abrasive formations. Following this, laboratory tests were conducted to replicate the failure modes encountered in the field. Five new PDC cutter grades were developed and tested against the field results. In parallel, critical drill bit design levers such as cutter size, blade count, backrake, and cutter chamfer were field tested to determine the most effective configuration. Finally, the optimal cutter grade and bit design levers were integrated into a rotating cutter mechanism and field tested. The results of this paper focus on validating the development process of the cutter grades, design levers, and the rotating mechanism, both individually and when all three are integrated into an optimal product. Among the three cutter grades laboratory tested, cutter grade C scored the highest, demonstrating a 35% increase in abrasive strength compared to the baseline cutter grade. Field test results against the baseline design with cutter grade C demonstrated a 156% increase in interval drilled. The optimal design levers combine a 16-mm cutter size with high backrake. The high backrake maximizes the PDC cutter diamond volume in contact with the formation, while the larger cutter size increases the point loading on the formation, minimizing drilling efficiency loss. A 5.875-in. bit that incorporated the design levers and cutter grade C housed in a rotating mechanism was then field tested. The bit demonstrated a 10% increase in interval drilled compared to the best offset run. The cumulative impact of these individual enhancements led to a step change in drilling efficiency, reducing bit trips and drilling costs. A reimagination of a classic drill bit design combined with a unique approach to PDC technology has allowed for a paradigm shift in drill bit durability in hard and abrasive rocks. Several bespoke analyses combined with novel drill bit technologies were developed, deployed, and validated in a new modeling environment. A modern and adaptable design philosophy was validated in challenging reservoir environments across the Arabian Gulf.
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