Viscoelastic Surfactants Are Turned To Acid Experiments And Simulation Studies

The viscoelastic surfactant self-diverting acid(VES acid) are widely used in matrix acidizing for carbonate for being self-viscosified with its consumption,leaving less damage to the reservoirs and extensive application scope.VES acid is mainly for the problem of effective acid placement caused by heterogeneity.However,the theory research about VES acid is far behind its project application.The design for several construction parameters rely on experience to a great extent.In this paper,we study the factors influencing rheological behavior such as pH value,calcium ion concentration and surfactant concentration.Based on a great quantity of experiments,we find out the relationship between viscosity and these 3 main factors.Then a numerical model is developed to describe reaction,transportation and diversion of VES acid in carbonate rocks for linear flow and radial flow on the basis of the two-ccale continuum models.The detail works are as follows:(1)Carrying out large quantities of experiments about the viscosity of VES acid. Analysising the relationship between viscosity and pH value,calcium ion concentration and surfactant concentration then a numerical model is developed.(2)Developing the numerical model of matrix acidizing of VES acid for carbonate reservoirs by coupling viscosity function with 2-scale continuum model. Then calculating this model on the basis of MATLAB.(3)Analyzing the wormhole propagation?pressure?acid concentration and Ca2+ concentration during VES acidizing.We mainly study the influence of injection rate on diversion capability.The results show that rejection rate have great effect on the growing of wormhole,the dostage of acid and diversion capability.To gain the best acidizing results,comprehensive consideration should be given to injection rate and its affect.By combining experiments and numerical simulation,we find out some regulars and recognitions,them may be helpful when acidizing with VES acid in oil field.