Abstract
Extended-reach horizontal wells are critical for the development of unconventional reservoirs. Dual-channel drill pipe drilling has a great advantage in improving the horizontal section length, while the research on its mechanical extended-reach limit prediction model is insufficient. In this paper, the torque and drag model is built considering the additional axial force of the sliding piston on the dual-channel drillpipe. Based on the torque and drag model, the mechanical extended-reach limit model for dual-channel drilling is established. A case study including a comparison to the conventional drilling method and sensitivity analysis is conducted. The result shows that under the same conditions, the mechanical extended-reach limit of the dual-channel drilling method is 10,592.2 m, while it is 9030.6 m of the conventional drilling method. The dual-channel drilling method achieves a further mechanical extended-reach limit than the conventional drilling method. To improve the mechanical extended-reach limit of dual-channel drilling, a higher back pressure on the sliding piston, a deeper measured depth of the sliding piston, a higher density of the passive drilling fluid, a smaller outer diameter of the outer pipe, a lower weight on bit and rate of penetration should be adopted. The work in this paper completes the extended-reach limit theory of dual-channel drilling, providing a guide for better use in unconventional reservoir development.
Highlights
The torque and drag model is the basis of predicting the mechanical mechanical extended-reach limit of a horizontal well
An additional axial force can be applied on the drilling string as a driving force by the sliding piston from the back pressure of the passive drilling fluid, overcoming friction in a horizontal well
The torque and drag model of dual-channel drillpipes is established considering the additional axial force applied by the sliding piston
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. For the dual-channel drilling method, prediction models of open-hole and hydraulic extended-reach limits were established by Li et al [30], in which formation characteristics and drilling pump capacity were both considered. Compared to the conventional drillpipe, which drives thedrilling drilling string is forward and extends the extended-reach limit drilling method, the sliding piston exerts a driving force on the dual-channel drillpipe,. The wheels on a tractor are pressed on the wellbore and rotated by an electric motor, driving the tools such as a perforation gun to move forward [37] with the driving force Fd. Similar to the sliding piston of the dual-channel drillpipes, an additional axial force is exerted by reach limit. Fd. Similar to the sliding piston of the dual-channel drillpipes, an additional axial force is exerted by the tractor on the tool string to overcome the drag in a horizontal section.
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