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<p>To address the challenges of excessive drilling disturbance and compromised coring quality encountered by conventional bit (CB) drilling systems in highly heterogeneous geological formations (e.g., fractured strata and fissured rock masses), this study integrates numerical simulations and experimental methodologies. Leveraging a self-balancing dual-bit (DB) drilling system, comparative models of conventional bit (CB) and dual-bit (DB) drilling processes in heterogeneous rock were established. A systematic investigation was conducted to elucidate the dual-bit (DB) disturbance mechanisms through multidimensional analyses encompassing borehole bottom morphology, vibration signatures, drilling pressure/torque dynamics, and borehole wall/core damage characteristics. Numerical simulations reveal that dual-bit (DB) drilling achieves a 35.16% reduction in mean vibration reaction force compared to conventional bit (CB) drilling, accompanied by decreases of 33.34% and 17.27% in drilling pressure fluctuation and torque fluctuation, respectively. Fractographic analysis demonstrates that initial rock fragmentation predominantly initiates within the annular region between the inner and outer bits. The failure modes exhibit distinct spatial patterns: rock units beneath the inner bit (IB) undergo dispersed point-wise failure, whereas those under the outer bit (OB) develop single-side-initiated lateral propagation. Experimental validation corroborates these findings, showing a 52.95% reduction in peak vibration acceleration during dual-bit (DB) drilling, alongside 81.93% and 70.73% decreases in borehole wall and core disturbances, respectively. This research establishes a theoretical foundation for implementing dual-bit (DB) drilling systems in highly heterogeneous formations, enabling enhanced operational stability and high-fidelity core recovery, thereby addressing critical limitations of conventional drilling technologies.</p>

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Simulation and Experimental Study on the Disturbance Mechanism of Dual-Bit Drilling in Heterogeneous Rock

  • 期刊论文

  • 发表日期：

    2025年7月25日

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  • Yan Zhao,
  • Yumin Wen,
  • Jinlong Wang,
  • Ke Gao,
  • Songhe Liu,
  • Jingkun Guo,
  • Xiaoshu Lv

摘要

To address the challenges of excessive drilling disturbance and compromised coring quality encountered by conventional bit (CB) drilling systems in highly heterogeneous geological formations (e.g., fractured strata and fissured rock masses), this study integrates numerical simulations and experimental methodologies. Leveraging a self-balancing dual-bit (DB) drilling system, comparative models of conventional bit (CB) and dual-bit (DB) drilling processes in heterogeneous rock were established. A systematic investigation was conducted to elucidate the dual-bit (DB) disturbance mechanisms through multidimensional analyses encompassing borehole bottom morphology, vibration signatures, drilling pressure/torque dynamics, and borehole wall/core damage characteristics. Numerical simulations reveal that dual-bit (DB) drilling achieves a 35.16% reduction in mean vibration reaction force compared to conventional bit (CB) drilling, accompanied by decreases of 33.34% and 17.27% in drilling pressure fluctuation and torque fluctuation, respectively. Fractographic analysis demonstrates that initial rock fragmentation predominantly initiates within the annular region between the inner and outer bits. The failure modes exhibit distinct spatial patterns: rock units beneath the inner bit (IB) undergo dispersed point-wise failure, whereas those under the outer bit (OB) develop single-side-initiated lateral propagation. Experimental validation corroborates these findings, showing a 52.95% reduction in peak vibration acceleration during dual-bit (DB) drilling, alongside 81.93% and 70.73% decreases in borehole wall and core disturbances, respectively. This research establishes a theoretical foundation for implementing dual-bit (DB) drilling systems in highly heterogeneous formations, enabling enhanced operational stability and high-fidelity core recovery, thereby addressing critical limitations of conventional drilling technologies.