Reversing the Drilling Damage in Naturally Fractured Limestone Using Self-Diverting Acid System: A Case Study

Abstract Formation damage remains one of the primary challenges in achieving optimal productivity from carbonate reservoirs, particularly in naturally fractured formations where drilling-induced losses and mud additives can impair near-wellbore productivity. This paper explores a strategy designed to reverse out the formation damage induced by such loss control measures and restore the deliverability of the formation to its optimum potential. The candidate well, completed across a naturally fractured limestone formation, was drilled with excessive loss control measures to reach the target formation. These measures impaired near-wellbore permeability, causing severe skin damage. To restore formation productivity and remove filter cake, the sand face was washed with mineral acid using chemical and mechanical methods. A tailored matrix acidizing treatment was designed to self-divert by sensitizing spent acid concentration to provide near uniform coverage across the long reservoir section. A novel, non-damaging viscoelastic surfactant-based diverter enabled viscosity reversal upon contact with hydrocarbons, enhancing smooth post-stimulation flowback of treatment fluids and improving inflow efficiency. The combined effect of mechanical cleaning via perforation wash jetting, chemical stimulation, strategic diversion, and foamed fluid displacement during matrix stimulation effectively restored near-wellbore connectivity and addressed the permeability contrast across zones. The matrix acidizing treatment utilized a high-reactivity, MS-based acid system formulated to maximize carbonate dissolution while minimizing risks of secondary precipitation and tubular corrosion. Visco-elastic self-diverting acid enabled uniform coverage across the perforated interval, overcoming reservoir heterogeneity and directing the treatment into lower permeability zones. Post-treatment evaluation indicated a production increase exceeding sixfold, validating the effectiveness of this integrated stimulation approach in restoring reservoir connectivity and mitigating near-wellbore damage in carbonate formations compromised by fluid loss and mud invasion. The application of a self-diverting acid system provided a comprehensive solution for damage remediation in an enhanced reactivity carbonate formation. This case highlights the effectiveness of customizing acid systems based on formation mineralogy and operational constraints, offering valuable insights for similar interventions in complex carbonate reservoirs.