Production Casing Regains Integrity by Repairing Shallow Leak with Microfine Cement

Abstract

While carrying out planned workover activities, production casing had to be tested to verify integrity. A shallow leak was observed across the production casing at about 1000 ft MD from surface. External and/or internal casing corrosion especially across relatively old wells, could lead to such inconsistency, moreover that major challenge to address and react such surprises online while operation meanwhile nothing to help as a pre-planning studies. Further production objectives require casing integrity as per ESP design to protect shallow aquifer sources. Numerous attempts to repair the casing leak by performing remedial squeeze operations utilizing conventional cement slurry designs proved unsuccessful. Other ideas were considered such as deploying a scab liner to cover the damaged casing section, however this was discounted as it would introduce undesirable borehole restrictions; as well as extra 6 days for running, cementing and clean-out. A novel engineered approach with Microfine cement slurry design squeezed into the damaged zone successfully regained casing and well integrity, while maintaining full borehole access through the production casing, thus saving rig time and tangible cost. Well drilling operations should be carefully designed and executed targeting the integrity assurance by providing the right casing metallurgy and good cementation for proper zonal isolation behind individual casing strings to mitigate external casing corrosion and act as the first line of defense against corrosion and any potential leakage or cross flow among different formations across the life span of the well. Well completions should be installed / tested considering the protection of inner production casing / liner from getting in prolonged contact with wellbore fluids, to avoid excessive internal corrosion and achieve reservoir fluid containment across the life of the well. A proactive approach been raised to acquire production casing / liners corrosion logs across workover activities especially regarding old wells to enable the mapping and interpretation of casing wall thickness / corrosion progress along the well life. That approach could aid in predicting the condition of production strings before commencing planned workover activity; and thus justify the availability of back-up repair plan to maintain rig operations and avoid any unscheduled operational surprises and possible strategic production rate defer.