Effect of cavities shapes on the roughness friction factor in perforated and slotted horizontal wells used to dewater opencast mines

The horizontal wells have been adapted to use for dewatering purpose in the mining industry. Due to unique characteristics, those horizontal filters are recommended to utilize not only the mechanical strength but also the hydraulic performance. Pressure drop along the horizontal well is a major factor that affects the performance of a wellbore. The pressure drop incurs due to four separate effects: wall friction, perforation roughness, inflow acceleration and mixing effects. This work presents the effects of the two first factors in perforated or slotted pipes, which correspond to the case of no flow through the wall. Numerical analysis was carried out with different types of perforations and slots. The simulated model accomplished using ANSYS Fluent 14.5. The results revealed that at high Reynolds number, the roughness friction factors in circular perforated pipes are significantly greater than those in axial slotted pipes and perpendicular slotted pipes.