Innovative Solution for Fluid Loss in Sub-Hydrostatic Wells During Workover Operation-Case Study from Kuwait.

Abstract

Fluid loss in sub-hydrostatic wells during overbalanced workover operation is a significant concern and includes three different challenges. The first challenge is the near wellbore damage due to the invasion of the completion fluid to the formation. The second challenge is the additional operating cost associated with both rig time spent to pump fluid into the well and stimulation treatment to restore the initial formation condition. The third challenge is maintaining a safe window of overbalance condition during the workover operation which is a major HSE & well integrity concern. The outmoded technique to control losses is to use solids base fluid which could damage the formation if not properly removed after the treatment. Also, in some cases it requires an acid breaker to restore the original formation state. The acid treatment must be done before installing the pump in hole as the solid-fluid system can't be flow back through the artificial lift. KOC keeps the safety window of the overbalance by pumping completion fluid (brine) into the well while killing operation. As a consequence, rig had to pump hundreds of bbls of brine into most of the depleted reservoirs which in most of the cases causes sever wellbore/reservoir damage (major concern) leading to delay in Production and increase in operation cost associated with rig time and completion fluid cost. Customised Salt Pill system is a unique solution for such challenge, and it had been proved trouble-free globally by sealing the face of the formation during the killing operation. Recently the salt pill system was deisgned and deployed in a well in one of KOC brown fields, the job magnificently compiled with KOC success criteria safely. Moreover, the fluid level was static in the well during the entire workover operation. With the successful flow back for the well after ESP installation, demonstrated no wellbore damage with salt pill even without requiring any breaker nor acid. The application of Salt Pill was successful and it lead to saving of approximately two days of rig time and Early Production from the well without damaging the reservoir with the invasion of completion fluid. This innovative solution has opened the way forward for KOC to implement same technology in other sub-hydrostatic wells.