Rock fragmentation and drilling experiment of electric impulse drilling and structural optimization of electrode bit

Abstract

Due to the low rate of penetration (ROP) and high cost of natural resource development projects such as oil and gas, and mining, it's urgent to explore some new rock-breaking methods with subversive characteristics for rising ROP. Electric impulse drilling (EID) has attracted widespread attention due to its unique advantages, but its rock-breaking effect is affected by various factors such as the structures of electrode bits, pulse voltage characteristics, liquid medium type, rock type, circulation conditions, and the contact between electrode bit and rocks, etc, leading to the lack of theoretical basis for the design of the electrode bit. Therefore, to more truly reflect the interaction among electrode bits, rocks, and liquid media of EID, this study carried out rock fragmentation and drilling experiment of EID on red sandstone. Firstly, an electrical impulse generator (EIG) with a stable frequency range of 1–5 Hz and a pulse voltage of about 0–80 kV at the load terminal was developed. And an indoor EID and rock fragmentation experimental system was built, then three kinds of electrode bits with typical structures: petal-type (H type), cross-type (S type) and, coaxial type (T type) were designed. Subsequently, the rock fragmentation and drilling experiment of EID was carried out on red sandstone in three liquid media (tap water, deionized water, and hydraulic oil) under the capacitors' charging voltage of 13–17 kV (the load terminal voltage was about 45–60 kV). The general influence law of electrode bit structure, liquid medium type, circulation condition, and pulse voltage on EID was studied. Finally, the electrode bits used in the experiment were evaluated, and suggestions for structural optimization of the electrode bit were put forward based on the experiment. This study is expected to further promote the design of electrode bits and the development of EID technology.