Study Of Diverting Acidizing Model In Heterogeneous Carbonate Rocks

Carbonate reservoirs have become one of the important succession of China onshore oil and gas exploration and development.Matrix acidizing are always applied to remove the damage and improve the formation percolation conditions.The problem of acid uneven distribution is serious due to severe heterogeneous formation.Diverting acid perform the characteristics of reaction slowly and self-diverting,which is a key technology to achieve the target of uniform distribution of acid in heterogeneous formation.The acidizing stimulation using diverting acid is a complex process containing reactive mass transfer,heat transfer,chemical heat release and physical properties changes.The current acidizing models are mostly simulate the acidizing stimulation on the ground condition,but they can not estimate the diverting acidizing in the formation condition.So a diverting acidizing model considering heat transfer,reactive mass transfer and physical properties changes need to be established to simulate the acidizing process in hot heterogeneous carbonation formation.In this paper,based on massive literature research,the chemical diverting technologies were inducted.The VES diverting acid had prominent advantages of automatic viscous and clean.The rheology evaluation and reaction kinetics experiments have been done.An empirical correlation considering multi-factors for residual diverting acid was obtained.A numerical model of wellbore temperature field was established to predict the downhole temperature during acidizing process.The model considered the complex wellbore structure,forced heat convection in tube and natural heat convection in annulus.The comparison results between numerical simulation and field data shown that the model was suitable for temperature prediction in reservoir stimulation process.Then,the effects of wellbore structure,heat conductive types and operation parameters were analyzed,the conclusions were of some instructive significance to acidizing.Based on two-scale continuum model,coupled the heat transfer and physical parameters,considered acid diverting in multi formation,a wormhole propagation model of diverting acidizing was established.The acidizing efficiency difference between hydrochloric acid and VES diverting acid was simulated and analyzed.The effects of formation temperature,acid temperature and reaction heat for wormhole propagation were analyzed.The effects of injection rate,formation temperature and interlayer heterogeneity for acid distribution were analyzed.The VES self-diverting acid could plug the high permeability zones,which would promote the acid flowing into the low permeability zones.The acid diverting ability could be improved by optimize the operation parameters.The diverting acidizing model established in this paper is of a certain guiding significance to matrix acidizing of carbonate formation.