Optimizing Cement Plug Operations for Severe Circulation Losses: Case Studies and Operational Improvements in Naturally Fractured Reservoirs

Abstract

Abstract

Abstract This paper presents strategies and operational improvements for curing severe and total circulation losses during oil and gas well drilling using cement plugs and direct injection methods. The scope includes analyzing critical factors for effective loss control, minimizing plug repetition, and mitigating hydrocarbon migration risks, with a focus on keeping the high-productivity of naturally fractured reservoirs. The study reviews historical operations and case studies, to evaluate the effectiveness of cement plug applications. It details the operational sequence, risk mitigation actions, and the properties of cement slurries used. The methodology includes transient simulations of pressure and temperature conditions, sensitivity testing of cement slurries, and the implementation of revised operational standards. Comparative analyses of cement density and temperature schedule are performed to optimize plug performance and reduce hydrocarbon inflow. Results indicate that the adoption of improved cement slurry designs and operational practices significantly reduced the incidence of hydrocarbon entry during plug setting, without compromising loss control effectiveness. Historical data show that, although repeated plugs were sometimes necessary due to exposure of new fractures, most operations achieved successful isolation. The new procedures, including the use of lighter, thixotropic cement slurries and enhanced temperature estimation, led to better operational outcomes: higher rates of effective loss control without repetition, complete absence of hydrocarbon inflow, and improved cement cutting performance. The study emphasizes the importance of rigorous adherence to updated standards and the need for case-by-case tailored slurry design. The findings provide actionable recommendations for improving operational safety and efficiency, contributing new insights to industry best practices for well integrity in challenging reservoir conditions.