Personalized design and field experiment of polycrystalline diamond compact bits for high-temperature geothermal wells

Abstract

Considering the existing geothermal drilling conditions in Kenya (200 °C, low penetration rate, and short service life), we propose new polycrystalline diamond compact (PDC) bits. The new PDC bit oblong holes, increase the drill hole radial coverage, can enlarge hole direct injection cooling cleaning the area of cutting tooth, reduce thermal wear failure of PDC cutters. Combined with the formation characteristics of the Olkaria block in a Kenyan well, the personalized design of PDC bits was realized by considering the following three aspects: high temperature–resistant PDC cutter optimization, bit cutting structure realization, and bit hydraulic structure realization. Furthermore, a φ 215.9-mm flat and long waterstoma PDC bit was developed and a field experiment was conducted. Experimental results show that the drilling speed of the PDC bit with flat waterstoma increased by 35.8%–144.3% and the footage increased by 173.4%–361.5% compared with the same bit in adjacent wells. This indicates that the PDC bit with flat waterstoma can adapt to Kenya's high temperature conditions (200 °C), efficiently cool the cutters, and prolong the service life of bits, accelerating the exploration and development of high-temperature geothermal wells. Furthermore, reducing geothermal drilling costs has positive implications.