Improving Productivity of Zubair Formation Using Matrix Acidizing

Abstract

Near-wellbore damage deteriorate oil production due to a reduction in permeability. Matrix acidizing may significantly enhance well performance by using a predefined mixture of acids concentration. After preparing core plugs (core sample cleaning), the petrographic inspection of thin sections has shown that all samples have quartz arenite rank which consists of 95% quartz mineral and little amount of clay minerals and calcite cement filling pores. The arithmetic average of measured porosity by using helium porosimeter was about 24.9%. Also, the geometric averaging permeability was 802 md measured by using core lab permeameter. Based on the technical criteria for selecting appropriate acids, HF (hydrofluoric acid) and HCl (hydrochloric acid) acids have been chosen to acidize core samples with concentrations of 3 and 12%, respectively. The high permeability of core plugs, besides mineralogical composition, is one of the reasons behind the percentages of acid concentrations of HF and HCl. Laboratory findings unequivocally demonstrate a substantial increase in oil recovery following core acidization, notably surpassing recovery rates achieved without acidization, especially in scenarios involving early water saturation. These findings underscore the significant potential of matrix acidizing as an effective strategy for mitigating near-wellbore damage and optimizing oil production in sandstone reservoirs.