The Study Of Wormhole Propagation In Fractured Carbonate Matrix Acidizing Under Radial Condition

The natural fractures in carbonate reservoirs largely affect the acid distribution and wormhole propagation during carbonate matrix acidizing.The effect of natural fracture on the propagation wormhole in the matrix acidizing was not studied.In this paper,numerical simulations of the wormhole propagation behavior under radial conditions in fractured carbonate reservoirs are carried out.Firstly,using the Monte Carlo method to generate random numbers and combine the probability distribution function of fracture parameters,considering the vector cross-product method and combined with the distribution of matrix porosity by using C++programming to acquire distribution of natural fractures.Secondly,a double-scale model of wormhole propagation under radial condition is established,based on the distribution of natural fracture,a wormhole propagation model of fractured carbonate-matrix acidizing is developed.By using numerical simulations,studied the wormhole propagation behavior of fractured carbonate reservoir,compared the wormhole propagation behavior of the two kind of distribution porosity,analyzed effects of natural fracture parameters?density,length,azimuth?and model size on wormhole propagation behavior.Finally,based on the model,the distance of the wormhole is predicted.The results of the study indicate that natural fractures have a decisive effect on the wormhole propagation.PV_bt with natural fractures is generally much lower than the PV_bt value of the matrix porosity,and is basically about 1/4 of the matrix porosity.Face dissolution,conical channels,wormholes,ramified wormholes,uniform dissolution still exist under natural fracture conditions.The PV_bt at different injection rates decrease when the fracture length increases.The fracture azimuth determines the wormhole propagation,but it has no obvious relationship with PV_bt at different injection velocity.PV_bt decreases when fracture density increases,but when the fracture density reaches a certain value?in this paper,1.6 bars/m²?,there is no certain relationship between PV_btt and fracture density.The change of the simulated model size makes the wormhole propagation significantly change,and the PV_bt at different injection velocity increases with the increase of the model size.The length of wormhole with natural fractures is significantly longer than that witho ut natural fractures.This study provides theoretical support and optimization methods for the acidization of carbonate rocks.