Drill Bits Evolution in Lump-Sum Turnkey Project Delivers Up to 70 Percent ROP Improvement

Abstract

Drilling rate of penetration (ROP) is one of the variables that influences well delivery timing and cost. ROP is affected by many factors, including but not limited to well profile, bottom hole assembly (BHA) design, challenging formations per section, and drill bit selection. In one of the drilling project in the Middle East, the primary method chosen to improve well delivery is to focus on optimizing the drill bit design in order to improve ROP while delivering other drilling objectives. As the project progressed, the ROP plateaued in most of sections in the field. The drilling team collaborated with the drill bit engineering to launch a drill bit optimization campaign in various hole sizes ranging from 16-in. to 6⅛-in. Since fixed-cutter bits are predominantly used in these sections, improvements are made to the existing drill bit designs by replacing the cutting elements with more efficient three-dimensional polycrystalline diamond compact cutters (3DC). 3DC cutters have different shapes, uniquely designed to tackle different drilling challenges. Using an in-house petrophysical log analysis program, each of the formations drilled in this field was analyzed, drilling challenges and ROP values were compared against previous performance. This information paired with finite element analysis (FEA) for dynamic drilling simulation was used to the optimize drill bit selection. This workflow was followed to avoid costly field tests and ensure that the newly designed drill bit performs flawlessly downhole. Other design elements, such as choosing bit body material, were also incorporated by converting matrix-bodied to steel-bodied, which not only improved the ROP but also reduced the cost-per-foot (CPF). Initially the bit optimization program enabled ROP improvement in the 16-in. section by 36 percent from 55 ft/h to 75 ft/h by replacing the roller-cone bit with a matrix-bodied fixed-cutter bit. Moreover, the drilling team further improved their performance, achieving 118 ft/hr. ROP when using the steel-bodied bit. The ROP in 12¼-in. section improved by 50% from 30 ft/h to 45 ft/h when the 3DC bit was used. Prior to using the 3DC bits, the existing bit design with the conventional flat PDC cutters was tested and showed minor ROP improvements. Similarly, two different 3DC cutters were introduced in the 8½-in. section and successfully improved overall ROP by 20%. In addition, the 6⅛-in. section showed 35-percent improvement in ROP following several design iterations that utilized two different types of 3DC cutters. By the end of the drill bit optimization campaign, the operator was able to improve the drilling curve and save up to 2.5 days per well. The 3DC cutters also helped eliminate the risk of bit failure in the 8½-in. section, wherein offset wells several bits were required to complete the section. With the performance mindset new technology deployment made faster to test new bit designs. This helped with getting early data point for analysis before being able to test in the different fields in the area.