Application of a Novel Solids-Free Diverter as an Alternative and Efficient Option to Replace Straddle Packers to Maximize Acid Coverage and Reduce Workover Rig Cost and Intervention Time: Two Case Studies from Iraq

Abstract The use of straddle packers is a common technique to accurately direct fluid treatments to specific wellbore areas. Once the packers are set, fluid is pumped through the inner diameter of the tool to stimulate the isolated zone between the packers. However, their use can be associated with additional costs, potential downhole tool failure, additional slickline and multi-finger caliper runs, and nonproductive time (NPT). Relative permeability modifiers (RPM) are a cost-effective diverter option to reduce rig and associated equipment costs through the provision of a high diversion-pressure response throughout stimulation treatments. A field application of a novel solids-free acid diverter (SFAD) system based on the use of RPM technology throughout the stimulation of sandstone formations in Iraq is described. This application used a solutions-oriented software package for complete remediation and stimulation. This novel SFAD decreases matrix-relative permeability to water-based fluid with the use of an ionic polymer, which directs subsequent stages to untreated zones. The water-based acid stages are then forced to other zones, which improves the acid coverage. This low-viscosity (less than 4 cp) RPM withstands high salinities and adheres immediately to the rock surface, which reduces soak times and makes the polymer suitable for continuous pumping. No special treatment considerations are necessary for this SFAD; it is simply pumped between the acid stages. SFAD can be used in carbonate and sandstone formations. Two recent treatments performed in a sandstone formation in Iraq that exhibited pressure increments up to 1,000 psi while the diverter was pumped are the focus of this work. The total acid volume was ramped up in two stages with 40/60 diverter ratios. More than 20 treatments have been performed in Iraq in carbonate and sandstone formations with this novel SFAD. The RPM, recently introduced to optimize well interventions, has demonstrated efficiency in intervals up to 50 m and permeability up to 6 Darcys.