压裂井的三维精细表征与单井模拟分析

3D Fine Characterization and Single-Well Simulation Analysis of Fractured Wells

目前压裂直井或压裂水平井的单井模拟主要是基于二维或拟三维网格进行表征,但这2类网格无法精细表征裂缝、井筒的三维空间形态。为此,提出利用计算机辅助设计(CAD)技术来进行压裂井的三维几何建模方法,形成了3D精细半结构网格剖分方法和流程,以及高效数值求解方法,将该方法应用于现场一口压裂直井,并对其进行了模拟分析。分析结果表明:所构建的3D压裂直井、压裂水平井的内边界井模型,简化和统一了不同压裂井模型的井产量计算方程,该方法同样适用于更复杂的3D定向压裂井的井产量计算;水力裂缝的几何形态、尺寸和小层物性是空间压力分布的重要影响因素。所得结论可为提高复杂压裂井的三维精细表征能力和单井模拟精度提供技术支撑。

The single-well simulation for fractured vertical or horizontal wells is mainly conducted based on two-dimensional or quasi-three-dimensional grids,which,however,cannot accurately characterize the 3D spatial morphology of fractures and wellbores.In this paper,a CAD-based 3D geometric modeling method of fractured wells,a grid node constraint algorithm adapting to fracture morphology and spatial flow characteristics,and a grid-scale optimization method were proposed.Then,semi-structured grids were used to build a 3D inner boundary model of fractured well,simplifying and unifying the production calculation equations for fractured vertical and horizontal wells.Based on the differences in flow characteristics of matrix and fractures,a coupled two-point and multi-point flux approximation method was used for numerical solution.Finally,a single-well simulation was conducted on a fractured vertical well in a multilayer reservoir with complex fracture networks.The results show that the differences in physical properties of layers have a significant impact on the pressure distribution of hydraulic fractures in the layers,and the geometric shape and size of hydraulic fractures as well as the physical parameters of the layers are important factors affecting the spatial distribution of pressure.The study results are of practical significance for improving the 3D fine characterization capacity and single-well simulation accuracy of complex fractured wells.