Research On Preparation And Displacement Of Artificial Core Based On Stereolithography Additive Manufacturing Technology

As a kind of non-renewable energy,oil reserve and its recovery are gradually decreasing year by year,which leads to the increase of mining difficulty and exploitation cost.Improving recovery efficiency while reducing producing production costs is one of the key issues in the field of oil recovery.Conducting the indoor displacement experiment with the core is an effective method to explore the formation mechanism and predict the distribution of remaining oil in the reservoir.This method also helps to clarify the oil displacement mechanism of various oil recovery ways,and provide guidance for potential exploration of the reservoir.However,in-situ natural core coring is complicated and costly.At the same time,the traditional artificial core has the disadvantages of non-replicability and nonvisualization,which results in site specificity and fuzzy experimental parameters.There are great limitations in the study of displacement and remaining oil formation mechanism.Meanwhile,the current micro model of displacement can only simulate the core on the two-dimensional level,which ignores three-dimensional porous connection features such as connectivity and curvature of pore space.Therefore,the research on the parameterization,manufacturing,replication and application of 3D core can provide an effective guarantee for the investigation of the formation mechanism of remaining oil and the enhancement of oil recovery.In this paper,based on the additive manufacturing technology of top molding stereolithography,a set of manufacturing devices is developed to meet the molding precision and size demands for the artificial core.Meanwhile,the horizontal and vertical forming accuracy technology is studied,and the forming process parameters are optimized.The manufacturing of porous media with complex shape and micro scale is realized.Simultaneously,based on the structural parameters of sandstone core in reservoir,the same grains in the sandstone are abstracted into microsphere,and the sandstone is abstracted into porous medium formed by stacking microsphere.According to the stereolithography characteristics of layer stacking,the influence of printing layers on microsphere sphericity analyzed.The artificial core structure with improved simple cubic stacking method is proposed,and the core structure is obtained.Based on the finite element simulation,the distributions of flow and pressure fields in pore throat structure are analyzed,and the influences of displacement parameters and artificial core model structural parameters on displacement efficiency are studied,which provides guidance for improving oil recovery.Finally,on the basis of body centered cubic stacking structure of microsphere and the heterogeneity of sandstones core,the core structure of conjugate quadrilateral is proposed.Then the distribution and formation mechanism of remaining oil in heterogeneous core are studied;the scheme of wettability transformation to improve oil recovery is proposed;the three-phase wettability process of water,oil and solid in displacement process is analyzed;the contact angle model of heterogeneous core surface and the capillarity of fluid are studied.With the combination of simulation and experimental methods,the effectiveness and correctness of the scheme of enhancing oil recovery by core wall wettability transformation are verified.