Nonpolymer Surfactant Enhances High-Strength Hydrofluoric Acid Treatments

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. ProposalTraditionally, operators have been reluctant to use acids with HF concentrations greater than 3% to remove drilling mud and stimulate the near wellbore region due to fear of formation deconsolidation in the near wellbore region. With some formations, even 3% HF concentrations will cause deconsolidation.During recent laboratory testing, it was discovered that the addition of the surfactant ("TH-1") to several conventional mud acid formulations and to several strengths of Retarded Acid System (RAS) formulations produced good stimulation in sandstone formations.Results of testing indicate that the use of the surfactant produces acid formulations which exhibit improved penetration of live acid, increase post-test permeability of test samples by a significant amount, and minimize rock disaggregation at the core face.The concentration of surfactant added is dependent on the unstimulated permeability of the rock, the rock mineralogy, and the temperature of the test. The concentration of surfactant tested to date ranges from 0.25 to 2%.Acid containing the surfactant may plug off higher permeability zones and streaks in test samples, allowing the acid to react with lower permeability streaks and zones. This technique is useful for self-diversion of acid treatments in sandstones and for causing a significant increase in permeability in sandstones which cannot be fracture stimulated.Hydrocarbons contacting the fluid during flowback will break the stiffened acid. The system is polymer-free so no polymer damage is present.