Applications of Real-Time Matrix-Acidizing Evaluation Method

Summary A new technique for real-time matrix-acidizing job evaluation has recently been presented that uses reservoir transients during acid injection to simulate pressure response of the unperturbed reservoir and compares simulated pressures with measured values. The difference between these values is attributed to the changing skin effect. An associated pretreatment injection/falloff test is presented as an essential element of that method. It involves injection of an inert fluid (water or reservoir oil) and analysis of the ensuing falloff for a period during which pumping has stopped, just before acid enters the perforations. Injection resumes immediately thereafter. Two field case studies, a water-injection well in a fissured carbonate reservoir and an oil well completed in a sandstone reservoir, demonstrate the technique. For both treatments, conclusions are drawn regarding the effectiveness of the acid injection. The job evolution is demonstrated, and forecasts of expected well performance for unstimulated and stimulated cases are presented. The skin evolution is shown as a function of injection time. The simulated and measured pressure values for both treatments are shown, indicating the real-time job progression.