The Simulation Research Of Horizontal Well Efficient Acidizing In Complex Carbonate Reservoir

The horizontal well greatly increases the reservoir drainage area,which has an advantage over the vertical well.The carbonate reservoir is often characterized by strong heterogeneity and the horizontal well has a large span.The different soaking time and pressure of drilling and completion fluid is likely to cause damage of irregular distribution,which increase the complexity of reservoir heterogeneity.Because the acid is more inclined to flow into the low seepage resistance area,the serious damage area will not be deal with ideally.Another main reason for the bad acidizing effect is that the wormhole channel with high conductivity has not formed near the wellbore.Therefore,for acidizing of horizontal wellbore in carbonate reservoir,high efficient acid-placement and effective deep penetration of wormhole is the two key technologies to remove formation plugging uniformly and ensure acidizing effect.This project focuses on the key problems of science and technology of horizontal well high efficiency acidizing plugging removal in porous carbonate reservoir,encircling closely the core problems of wormhole propagation mechanism,extension rule and its influencing factors.Based on local reaction,diffusion and convection and continuum theory,and combined with the reaction dynamic,three-dimensional CT imaging scanning experiment methods by the combination of theoretical analysis and numerical simulation method,a multi-scale 3D wormhole extending mathematical model was built,and the accurate 3D dynamic simulation of wormhole extension,competition and development were achieved.Based on the rheological experimental study,the constitutive equation of steering acid variable viscosity under multiple control factors is constructed,and the steering acid synthesis control equation and simulation method are formed.Taking the damage feature description,acidizing model optimization,technological parameter optimization and post acidification evaluation as the main line,a set of efficient 3D fully refined mathematical model and optimization method of horizontal well are developed.The research has perfected the theoretical foundation of acidizing reformation of carbonate reservoir,and provided an optimization method for simulation,design and effect prediction in industrial application.The main research work and achievements are as follows:(1)Based on the continuous medium theory,we established a multi-scale three-dimensional 3D wormhole extending mathematical model under different flow type.Through computer programming to the coupling of complex physical field,we provided a theoretical basis for the realization of carbonate reservoir matrix acidizing dynamic fine simulation.(2)Combined the basic theory of heat and mass transfer as well as geology,and aimed at the problems of complex pore connection structure,complicated rock mineral composition and complex heat and mass transfer between fluid and solid in the carbonate rock,acid rock reaction mathematical model under the non-isothermal conditions and multi mineral medium was established.We emphasized on the research of influence rules of fluid and solid heat transfer and exothennic reaction,rock space physics connection and multi mineral filling on wormhole propagation behavior,enriching the theory basis of wormhole numerical simulation.(3)Comprehensively Considering the important influence factors of surfactant concentration,metal cation concentration,pH value and shear rate,we built the diverting acid effective viscosity constitutive equation under a multi factor control mechanism;coupling three-dimensional wormhole extension mathematical model,we established the diverting acid acidizing comprehensive control equation and simulation method,revealing the diverting acid variable viscosity acid and diverting control mechanism.(4)According to the basic idea of carbonate reservoir horizontal well high efficiency acidizing design,the establishment of a comprehensive mathematical model and method of horizontal well damage characterization description,acidification process,the pattern transformation method and post acidizing effect evaluation are finished;Focused on the example of horizontal well general,segmentation and local acidification model optimization,engineering parameter optimization carried out the system research,providing strong technical support for the realization of horizontal well efficient acidizing.