The Brazil ultra-deepwater, pre-salt application has been a very challenging drilling environment since exploration activity began in 2005. The initial pre-salt section contains limestone with random silicified nodules. Over the last few years, operators have collected large amounts of data for service companies to analyze to improve drilling performance through bit design. Using this information, a hybrid bit design with the most advanced cutter and bit technology was developed successfully increasing the distance drilled by 138% and the rate of penetration (ROP) by 171%.Prior to advanced hybrid bit technology, a variety of other drill bit technologies such as polycrystalline diamond compact (PDC) bits and impregnated designs were used in the pre-salt. Historically, impregnated bits had longer runs, but with high mechanical specific energy (MSE) and low ROP, drilling with these bits was not economical. Contrarily, PDC bits can deliver higher ROP but cannot drill as far as impregnated bits. Three hybrid designs, the last one using dual-chamfer technology, were brought into this application to reduce cost-per-meter through better drilling efficiency and ROP. Each successive design managed to exceed customer expectations.Extensive laboratory tests were conducted on the hybrid designs to address the demanding needs of pre-salt applications. These unique bits showed promising results on atmospheric surface rig tests and in pressurized bottomhole simulator testing. Hybrid bits produced much less torque, with smoother torque fluctuations and faster ROPs than roller-cone and PDC bits through the simulated interbedded formations in laboratory testing. Novel dual-chamfer cutters used in the bit have been lab tested on a vertical turret lathe (VTL), a visual pressurized single-point-cutter (VSPC) test machine and a monotonic loading test. Cutter testing showed positive VTL results and increased resistance to diamond fractures.Ultra-deepwater drilling is very demanding and expensive, so operators want to achieve total depth in just one run by avoiding trips to change out the bit or bottomhole assembly (BHA). The improved bit and cutter technology resulted in significant cost savings and confidence for the customer. The performance of the hybrid bit with dual-chamfer cutters was significantly better than offsets, saving the operator approximately USD 9769/m.
Historically, deepwater offshore Brazil underreaming operations in large hole sizes (bigger than 20 in.) were always considered a significant challenge due to the presence of hard, abrasive interbeded formations in these sections. These challenges were typically associated with premature underreamers cutting structure damage and with bottomhole assembly (BHA) or drillstring catastrophic failures. These situations have caused extra costs to operators to implement remedial solutions, such as enlarging a pre-drilled hole or performing expensive fishing operations.Downhole vibrations, along with underreamers' cutting structure durability had been the main villains in this type of operation. Recently, many options have been tried by operators and service companies including the selection of various drill bit types to improve drilling dynamics, and the use of nonconventional BHAs with underreamers in tandem to enhance the system's longevity. In spite of these efforts, the problems have remained.A total systems approach was implemented to overcome these problems in a particularly challenging application offshore Brazil, where in the closest offset seven underreamer runs were needed to enlarge 850 meters. As the goal was maximizing the likelihood of drilling and underreaming the entire section in a single run, the under-reamer was equipped with a specialized heavy-duty cutting structure design. The design consisted of an optimized blade profile with increased cutter density and the latest newest technology in PDC cutters with improved impact and abrasion resistance. Along with the fit-for-purpose underreamer design, it also utilized a concentric expandable stabilizer on top of the underreamer to reduce downhole vibrations and a real-time drilling dynamics service to monitor downhole torque, weight on bit and vibrations to adjust drilling parameters as needed during the operation.This concept was introduced for the first time in a big-bore project in Brazil. Proper planning and integration between the operator and service company resulted in drilling and underreaming 1,164 meters in a single run, with a total of 304 circulating hours. This accomplishment finalized the 18 1 8 -in. ϫ 22-in. section twenty days ahead of the planned AFE.
Salt drilling in offshore projects has become more frequent over the last 10 years in many parts of the world. In Brazil, important oil discoveries were made in carbonates reservoirs that lay below thick salt bodies. Drilling through salt can be challenging, especially where severe salt mobility is common. Salt mobility or creep rate is mainly a function of downhole temperature, geomechanical stresses around the salt body and salt mineralogy.Today, many deepwater wells targeting hydrocarbons below the salt in Brazil are still considered exploratory or appraisal, and are drilled vertically through salt, with only a few projects in the development phase. Due to the gradual transition of deepwater projects into the development phase, the requirement for directional drilling through salt is rapidly increasing.To achieve a better understanding of the salt drillability, in terms of steerability capabilities and directional assembly stability, a pioneer directional drilling test was conducted in a mobile onshore Brazil salt formation, using an advanced rotary steerable system (RSS) and a specialized downhole drilling optimization measurementwhile-drilling (MWD) tool. This paper will show, in detail, the results and lessons learned from this unique salt drilling steerability test, along with the result of deepwater sections drilled directionally through salt formations offshore Brazil.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.