Chemical diverter systems, such as relative permeability modifiers (RPMs), can significantly reduce effective permeability, mainly to aqueous-based fluids (e.g., acids), where the fluid enters into the interval being treated. Graded salt is a granular solid used at all temperatures that has a wide particle-size distribution (PSD) for bridging and sealing to provide effective diversion of treating fluids. This combined with an RPM fluid can help divert the entire interval during a matrix-acid stimulation. This paper discusses a review of wells treated, with excellent results, using such a chemical and bridging diversion system (CBDS) in different fields in the southern region of Mexico.
If a formation has zones containing a large number of open, natural fractures, the resulting tendency is for treatment fluids to flow into the zone(s) with the highest effective permeability or the least amount of damage instead of creating a uniform distribution over the entire interval, as is necessary. An important characteristic for a diverter product is creating a temporary skin effect during the injection of the treatment that leaves no permanent damage or that can later be removed or dissolved.
The focus of this study was on gathering more detailed information for the selection of the diverter, treatment design, and operational procedures. Additionally, the learning curve is presented associated with the challenge of stimulating a specific zone within a complex mechanical wellbore and selecting the correct candidate for applying a schedule of mechanical diversions and acid stimulations.
Laboratory study data are included to illustrate how the diverting process physically manifests, which is used to substantiate the field designs. Understanding how chemical diverters interact with the formation rock and fluid is fundamental to selecting the proper product for a specific treatment application.