Case Study of a Novel Acid-Diversion Technique in Carbonate Reservoirs

Abstract

Abstract A novel non-particulate, non-foam diverting agent was developed to improve zone coverage during matrix stimulation of carbonate reservoirs. Typically the treating fluid flows into thief zone/s of high water-saturation and/or higher permeability sections. Higher water cut often results due to over-treating the water zones and inadequate treatment of the hydrocarbon bearing zones. Although foam has been used successfully in diverting acid from the aquifer to the damaged oil zones, the limited nitrogen availability in some areas and additional handling requirements call for a simpler process, especially in long intervals where multiple acid/divertor alternating stages are involved. The newly developed one-additive diverting agent system contains only a viscoelastic surfactant (VES) which can easily be mixed in brine to form a highly viscous gel. The gel maintains its viscosity when contacting water thus temporarily plugs the high water-saturation and/or pre-stimulated zones resulting in diversion of acid into the targeted oil zones.