Laboratory Study Provides Guidelines for Diverting Acid With Foam

Abstract

Summary A series of experiments was conducted in which foam quality, foam reactivity, diverting-stage volume, core permeability, and treatment design were varied. The goal was to determine how these parameters affect diversion in competing limestone cores. Situations involving natural permeability differences and diversion to damaged cores were considered. Experiments indicate that the minimum foam quality required for useful resistance to acid flow is 60%; foams of 70% or 80% quality were the most effective for diversion. Both acid and brine foams were used. Acid foams provide good diversion and can be included easily in a treatment, while in high-porosity, low-permeability limestones like chalk, brine foams appear to be more effective than acid foams. One can expect to maintain good diversion up to a permeability ratio of 10. Results also show that both types of foam effectively divert acid to damaged cores.