Weight Distribution Characteristics During the Process of Hole Enlargement When Drilling

  • Jun Jing
  • Yiyu Lu
  • Xiaohua Zhu
  • Liming Dai
  • Weiji Liu
Research Article - Petroleum Engineering


The weight distribution between the pilot bit and reamer is the key factor to ensure the safety and performance of hole enlargement when drilling (HEWD) assembly when reaming. Based on the finite element method, a real-time model of HEWD assembly was proposed, in which it can simulate the interactions between the components. The characteristics of weight distribution and its effects on the dynamic of HEWD assembly were studied. The results indicate, in homogeneous formation reaming, the optimal rotary speed can improve the utilization of mechanical energy up to 97% and leads to a more reasonable weight distribution. The weight distribution will also be reasonable when the difference in strength between the upper soft and lower hard formation is less than 17 MPa. However, the reamer will be out of drilling when the difference exceeds 37 MPa. In addition, the weight distribution ratio is less than 0.3 when the difference in strength between the upper hard and lower soft formation is less than 32 MPa. But it will exceed 0.5 when the difference exceeds 37 MPa. The ROP keep on increasing 1.6 and 1.4 times when the HEWD assembly reams through the upper Quartzite and lower black sandstone formation, respectively. But the ROP drops by 52 and 11% when it reams through the upper black sandstone and lower Quartzite formation while the torque slightly increases. Based on the trend of ROP and surface torque, engineers can judge the working status of a HEWD assembly and make appropriate adjustments.


Hole enlargement when drilling Weight distribution Rock strength Transition zone 

List of Symbols


HEWD assembly system damping matrices


Hole enlargement when drilling


HEWD assembly system stiffness matrices


HEWD assembly system mass matrices


Excitation applied to HEWD assembly system


Rate of penetration


Revolutions per minute

\(\hbox {S}\)

Cross-sectional area, m\(^{2}\)


Weight on bit, kN


Weight on reamer, kN

\(\left\{ {\ddot{u}} \right\} \)

Acceleration vectors of node

\(\left\{ {{\dot{u}}} \right\} \)

Velocity vectors of node

\(\left\{ u \right\} \)

Displacement vectors of node

\(\kappa \)

Weight distribution ratio

\(\delta \)

Difference of rocks strength


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Copyright information

© King Fahd University of Petroleum & Minerals 2018

Authors and Affiliations

  • Jun Jing
    • 1
    • 2
  • Yiyu Lu
    • 1
  • Xiaohua Zhu
    • 3
  • Liming Dai
    • 4
  • Weiji Liu
    • 3
  1. 1.State Key Laboratory of Coal Mine Disaster Dynamics and ControlChongqing UniversityChongqingChina
  2. 2.Postdoctoral Research Station of Chongqing UniversityChongqing UniversityChongqingChina
  3. 3.School of Mechatronic EngineeringSouthwest Petroleum UniversityChengduChina
  4. 4.Industrial Systems EngineeringUniversity of ReginaReginaCanada

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