Effects of Non-uniform Skin Distribution on Horizontal Well Inflow Performance

Abstract

Abstract Formation damage around a horizontal wellbore has been a long-standing problem. The damage zone is expected to be a cone-like shape, extending from the heel end to the toe. This situation leads to a difficulty in studying the inflow performance. In fact, previous studies assumed clean and homogeneous formations and ignored any skin factor in predicting pressure drops along a horizontal wellbore, critical rate, and water breakthrough time. The present study is focused on investigating influx and flowing pressure distribution along a horizontal wellbore in the presence of non-uniform formation damage. The relevance with the inflow performance is also discussed. Modified wellbore hydraulics correlations coupled with a reservoir inflow equation are used to accommodate this effort. Calculations are performed for different skin distribution, damage severity quality, and wellbore diameters. Results obtained show that non-uniform skin causes reduced influx rate toward the heel end. The undamaged well reveals an opposite trend as expected. For a given total production rate, the influx rate at some portions of the wellbore increases as the formation damage gets heavier, as well as for smaller wellbore diameter, resulting in greater pressure drops. Thus, the presence of non-uniform skin promotes an increase in pressure gradients within the wellbore. The changes in pressure losses are more sensitive to the level of damage severity in smaller wellbore diameter. Such a study has not been previously reported in the literature. Overall, this investigation improves our knowledge to better understand flow behavior in a horizontal wellbore. The paper presents information to be considered in predicting the inflow performance and also provides a guide for deciding or optimizing a horizontal well completion strategy.