Approach to Optimization of Acid Treatment in Oil Reservoirs

The mathematical model of two-phase displacement of oil by an acid aqueous solution in the neighborhood of a well and a hydraulic fracture [1] was used for investigation processes of optimization acidizing and acid fracturing. It takes into account the kinetics of acid dissolution of a carbonate rock. The proposed model allows us to improve the process of searching and selecting the best design for acidizing and acid fracturing. The effect of well acidizing and acid fracturing are estimated. It is shown possibility to find the best value of such parameters as the speed of injection, speed of reaction and volume of acid mixture injected into a well during acidizing and acid fracturing. At given process parameters in the real case is shown importance of studying the process of interval treatment including the possibility of optimizing the design of each of the treated intervals. The control of such parameters as the injection rate, the chemical reaction rate and the volume of injected acid makes possible to reach the maximum treatment effect at the given solution volume. Also calculations showed that in the case of the acid fracturing the significant slowing of the reaction rate may lead to large leakage of unreacted acid into the reservoir, extending the penetration zone, but also reducing the effects near the fracture and thus worsening the result of treatment. The created model was applied to numerical calculations for real cases. Field and calculated data are in good agreement. Using of this approach allows us to find the ways for new possibilities in improving design of acid treatments and understand the current status of the proposed design.