Perforation inflow reduces frictional pressure loss in horizontal wellbores

The total pressure drop in horizontal wellbores has been analyzed in terms of four separate effects: wall friction, flow acceleration, perforation roughness, and fluid mixing. Laboratory experiments have been carried out in test pipes that are geometrically similar to perforated liners used in horizontal wells to investigate different pressure drop effects in a horizontal wellbore. It was demonstrated that the perforation inflow actually reduced the total pressure drop. Results indicated that the pressure drop due to perforation roughness was eliminated by the perforation inflow when the ratio of perforation flow to pipe flow rate reached a certain limit. Beyond this limit, the perforation inflow lubricated the wellbore flow. Such smoothing effect in the perforated section of the wellbore extended into the blank section downstream. It has been shown that different pressure drop effects can be conveniently represented by using a pressure loss coefficient.