Study On Reservoir-wellbore Sand Production Law Of Weakly Consolidated Sandstone Reservoir

Sand production control and management is one of the key technologies for stable stimulation and efficient production of weakly consolidated sandstone reservoir.At present,the overall sand control technology development has gradually transformed from static to dynamic,from general to fine.The "engineering operation" of sand control in the single well has been upgraded to the level of "production management".Fluid-solid control has extended from bottom hole sand control to wellbore and surface management.Production-completion now faces the demand of intelligence and integration.However,there are still systematic research gaps on sand production management in the whole process from reservoir to wellbore,which restrict the efficient development of weakly consolidated sandstone reservoir.Aiming at the above problems,this paper combines theoretical analysis with numerical simulation to study the law of sand production from reservoir to wellbore in the main flow space containing oil and sand,to provide theoretical support for the integration of well completion and lifting production.(1)First,the machine learning models for shear wave logging data and formation sand particle size profile prediction are established,by the method of multi-point mapping to construct feature engineering and comprehensive fuzzy evaluation to optimize machine learning model.The single model is weighted by error reciprocal method and the combined prediction model of machine learning is established.Second,the mathematical model characterizing the particle size distribution of formation sand and the prediction method of sand production radius and speed based on pore elastic softening plastic model are proposed.Next,the dynamic evolution method of reservoir life cycle relative to sand production profile is constructed to predict the sand production law of oil wells from different levels.(2)Based on Euler double fluid model and discrete element theory,the numerical model and solution method(CFD-DEM)for dynamic analysis of oil sand two-phase flow coupling are established.Through the numerical simulation of the micro sand retaining process of slotted screen,accurately describe the complex morphology of sand retaining.The dynamics of sand deposition and blockage on the surface of sand retaining medium are studied and the micro mechanism of sand retaining process is revealed.The concept of fractal dimension based on the distribution characteristics of formation sand particle size is proposed and the prediction model of cumulative sand production quality and particle size distribution are established to reveal the influence of particle size distribution characteristics on plugging equilibrium pressure drop and plugging equilibrium time.(3)Based on CFD-DEM method,the research on wellbore flow law of sand carrying has been carried out.The sand migration model of wellbore is established and the change rule of sand concentration in the heterogeneous suspended layer and the suspended layer section are obtained.According to the influence of fluid velocity on sand concentration in wellbore,the method,applied to engineering practice,for quick determining the critical velocity at which sand particles do not deposit is given.The prediction model of sand concentration is established to quickly determine the sand flow state in horizontal wellbore.(4)In order to solve the technical problem of low sand carrying efficiency at the toe end of horizontal well,a horizontal well toe end sand control screen pipe aimed at changing the flow path of oil and sand from the screen to the base pipe is invented.The oil sand separation is realized through the "annular channel" of the sand control sleeve assembly,and the "diversion channel" changes the fluid flow direction and improves the sand carrying capacity at the toe end.Through the study of sand production law in the whole process from reservoir to wellbore,the integrated well completion and lifting method of sand production management is formed,which provides a theoretical basis for improving the decision-making level of sand control and development effect of weakly consolidated sandstone reservoir.