Implementing a Solids-Free, Non-Damaging Loss Control Solution to Enable Overbalanced Workover Interventions: Case Studies and Applications from 80+ Wells in Iraq

Abstract

Controlling lost circulation can be costly and complicated. When well conditions include low reservoir pore pressure and high reservoir permeability, traditional techniques to minimize fluid loss, such as solids or viscous pills, can damage the formation due to interaction with sandstone formation characteristics, such as kaolinite, smectite, incrustations, polymer residues, pH changes, clay swelling, and others. This often means that minimizing near-wellbore damage is key for the future productivity of the well. This paper presents a laboratory validation and field application of a novel solids-free fluid-loss (SFFL) system based on a relative permeability modifier (RPM) used during well-kill and overbalanced workover operations. This study will focus on the detailed information needed for selection, treatment application, and operational procedures used in sandstone formations in Iraq. This system relies on an ionic polymer that decreases matrix permeability to aqueous fluids, limiting leak-off into treated zones. This RPM, with low molecular weight, high salinity tolerance, very low viscosity (less than 3 cp), and acid resistance, immediately adheres to the rock's surface, eliminating the need to shut the well in. In addition, this system does not require breakers, which eliminates the negative impact on post-stimulation well productivity. Laboratory test data shows the capability of the material to control fluid leak-off and achieve high levels of regained permeability to hydrocarbons. Fluid is placed in front of the target zone and can be pumped, squeezed (or gravity injected) into the formation. As the majority ofmost of the cases have been applied in old wells, the treatment injection pressure limit must be related to the casing integrity with no more than 1,000 psi measured at surface. To date, about 80+ jobs have been performed with this novel SFFL system in Iraq. This system has been proposed for solving partial and total losses, to full circulation in overbalanced operations such as: Lost-circulation events during well killing operationsWellhead maintenanceWell integrityReplacement of electrical submersible pumps (ESPs)Overbalanced tubing-conveyed perforating (TCP), among others Laboratory tests, procedures, case histories, and continuous improvement actions are presented in this study.