A new model of skin factor and productivity ratio evaluation for horizontal wells with various completion systems

This paper addresses the additional flow resistance area formed in 8 leading completion systems of horizontal wells,which is divided into several areas from distant formation to inside wellbore including outside casing annular area,perforation compaction area,perforation hole packing area,and inside casing packing area in order to give a uniform formula of horizontal well productivity with consideration of skin factor.According to an assumed physical model,the calculation method of laminar flow and turbulent flow pressure drop and skin factor for the above areas is evolved and the calculation model for total skin factor and productivity ratio of horizontal wells with various completion styles is developed.This model can be optionally and easily used to analyze the skin factor of all flow areas and the productivity ratio of all well completions.A case study has analyzed the skin factor of each flow resistance area,the impacts of contaminated zone,perforation parameters and packing zone permeability on productivity ratio,and proposed methods of improving productivity ratio.