Model study of acid fracturing model for carbonate reservoirs

The current acid fracturing design has the problems as follows: the classical leakoff theory for homogeneous reservoirs is mostly used for the leakoff of fracturing fluid, the acidizing fluid does not taken the effect of acid wormhole into account, and the simulation of acid-rock reaction dose not consider the acidizing fluid mass transfer along the fracture height. In accordance with the problems, on the basis of the up-to-date research of acid fracturing models, further study is conducted on the core models for multi-stage acid fracturing design and calculation of carbonate reservoirs. So the model is set up for calculating fracturing fluid leakoff of carbonate reservoirs when multi-state acid fracturing, the analytic solution to the model is presented. Based on the reaction characteristics of acidizing fluid flow, the growth model of acid wormhole, the reaction model of acidizing fluid in wormhole, and the flow model of filtrated acidizing fluid in formations are established. The calculating method of acidizing fluid leakoff favorable for field application is put forward. Considering the migration of acidizing fluid along the fracture length and height and the convective diffusion of acidizing fluid along the fracture width, the numerical model of 3D acidizing fluid flow-reaction is developed. All these provide theoretical basis for acid fracturing design of carbonate reservoirs.