Technique to Estimate Fluid-Loss and Fracture Geometry of Fracture Acidizing with Foamed/Non-Foamed Acid

Abstract A technique to estimate fluid-loss, hydraulic fracture geometry and acidized fracture geometry is developed for fracture acidizing with foamed or non-foamed acid on the basic of PKN fracture model1,2. The treatment processes are simulated during injecting and the practical bottom hole pressures after shut-in are matched with the predicted bottom hole pressures in this technique. The corresponding models to simulate fluid temperatures, pressures and flow in a fracture after shut-in are established and the models to calculate bottom hole pressures after shut-in from tested wellhead pressures while a foamed fluid is used as a overflush fluid are presented. The study indicates the flow rate in fracture is a variable during injecting and continuous flow into fracture exists after shut-in because of thermal expansion and compressibility when foamed acid is adopt in treatments. The bottom hole pressures are overestimated without consideration of warming up and continuous flow. The comparison study of two wells shows that the fluid-loss is underestimated with not considering the thermal expansivity and compressibility of fluids, CO2 produced by acid-rock reaction and the heat of acid-rock reaction. The influence of thermal expansion is most significant in the two well investigations and is more pronounced in treatments with foamed acid.