This paper details the improvements to drilling performance and torsional response of fixed cutter bits when changing from a conventional 19-mm cutter diameter configuration to 25-mm cutter diameters for similar blade counts in two different hole sizes. Key performance metrics include rate of penetration (ROP), rerun-ability, torsional response, and ability to maintain tool-face control during directional drilling. A high-performance drilling application was selected with several existing offset wells using a 12¼-in., five-bladed, 19-mm (519) drill bit design, and a concept bit developed using 25-mm diameter cutters while maintaining comparable ancillary features. This was tested in the same field on both vertical and S-shape sections using the same bent-housing motor assembly and drilling performance compared to the existing offsets. A 17½-in. hole size application that experiences high drillstring vibration was also selected, and a 25-mm cutter diameter drill bit was designed with comparable ancillary features to replace a six-bladed, 19-mm (619) drill bit. This was tested in the same field with the drilling performance, and vibration propensity was assessed. Initial testing in the 12¼-in. section showed extremely promising initial results, breaking the field ROP record in a well-established field of more than 3,000 wells. The rerun of the same bit without repair placed fourth in the field in terms of ROP records. Additional testing in the vertical and s-shape sections showed the new 25-mm cutter diameter design consistently exceeding the ROP performance of the 519 drill bit design while achieving directional targets without any reported drilling concerns. Subsequent trials with other operators saw similar performance improvement with multiple instances of breaking field ROP records. The first trial of the new 17½-in. hole size design with 25-mm diameter cutters had 34% average higher ROP than the offset average ROP, achieving the field ROP record. An overall 70% improvement during trials was seen in ROP versus the existing 619 drill bit design. The daily drilling reports and client feedback reported a significantly reduced level of drillstring vibration versus offset wells. This paper demonstrates the potential for a paradigm shift in drilling response and overall ROP by using 25-mm diameter cutters on fixed cutter bits. When correctly modeled, designed, and selected for specific applications, they benefit operators by reducing the time it takes to drill the section, improving repairability, reducing the time that an openhole is left exposed, and reducing drilling costs.
This paper details the inception, modeling, laboratory, and field testing of a concept polycrystalline diamond compact (PDC) drill bit when removing its vestigial features. The extent to which length, gauge geometry, and bit design can affect directional response on push-the-bit rotary steerable systems (RSS) and a bent housing motor is examined. Results from laboratory testing provided feedback into analytical models for validation and are then field-tested in several different directional applications. A comprehensive study was conducted to determine the benefits of removing the bit shank, which can be considered a redundant structure, alike the human appendix. Following this, both a steering-sensitive drill string model and computer-aided design (CAD) analyses were conducted to predict directional response and steering force values of both conventional and short-shank configurations. Drill bits were then manufactured and repeatedly tested on a push-the-bit RSS tool in a horizontal drill test. The testing results were used to validate and optimize the drill string model. This validated model was then used to design a drill bit for a field application where directional work was historically challenging. The results from this paper focus on validating the short-shank concept known as the ultra-short make-up (USMU) bit via the drill string model and rigorous testing, as well as confirming the potential drilling benefits in challenging directional applications. The initial assumptions and approach from the drill string model and CAD analyses are presented. Validation by several high and low side tests on push the-bit RSS using drill bits with and without the short-shank modification were conducted. The dependent variables for testing were the directional capability, bit stability, borehole quality, and gauge pad-to-borehole interaction while biasing. The drilling parameters were kept constant to allow for a fair comparison of this concept design. The results of the post-horizontal testing were examined against the drill string model and adaptations made to both the model and its initial assumptions. This concept was then field-tested in a challenging directional application in Oman where steerable roller cone bits were predominately used. This led to back-to-back field rate-of-penetration (ROP) records, stable tool face, and excellent steering response from two hole sizes. The vestigial concept generally applies to genetically determined structures or attributes that have apparently lost most or all their ancestral functions, such as a human's appendix or coccyx. This approach has rarely been used to drive technological developments within oil and gas tools. It also gives a refreshing new framework for concept, testing, and validation of changes to this unique directional drill bit design. A future development phase of this concept is to test it on the various rotary steerable systems and beyond.
Drilling challenges in the Hassi Messaoud (HMD) oilfield have proven to be equal to the magnitude of its production. Historically, wells drilled in this field were vertical, moderate borehole diameters having a long 12 ¼"section. In order to increase production and to gain a better understanding of the reservoir, Sonatrach Drilling engineering moved to moderately deviated large diameter boreholes, delivering 1000 meters of drain in the reservoir. Instead of the conventional 12 1/4’’ vertical section, 1800 meters was drilled in 16’’ diameter. This section consists of abrasive sands, inter-bedded evaporate/carbonate and sand/claystone formations prone to instability and collapse. In addition, there is a 30 meter band of extremely hard dolomite. Rock strengths vary widely from 5 Kpsi to 30Kpsi. Since early 2000, Sonatrach and National Oilwell Varco (NOV) have been working as a team to rise to the challenges presented by the larger hole size. Most significantly drilling vibrations, slow penetration rates, increased trips to TD, severe bit and BHA damage and NPT due to stuck pipe while pulling out-of-hole. This article describes first, the process by which significant performance improvement was achieved as a result of combining innovative bit design techniques and technologies, BHA optimization, optimization of parameters through BHA dynamics modelling, and formation Rock Strength Analysis. Secondly, the article discusses optimized techniques introduced to enhance performance for the 16’’ section on rigs that have been recently equipped with VFD - AC top drives and properly deal with torque limitation issues. This enabled Sonatrach to repeatedly set ROP drilling records as well as consistently making section TD in a single run. The net result was a 37% improvement in rate of penetration1.
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.