基于集合平滑数据同化与直接采样法融合水文地球物理数据刻画裂隙网络分布

Characterizing fracture networks by integrating hydrogeophysical data based on the ESMDA-DS method

刻画裂隙含水层在地下水污染、地热、油气资源开采等研究中起关键作用。由于裂隙介质的强非均质性,其渗透率场一般呈现出显著的非高斯特性,该特性给水文地质参数的推估带来了极大的困难与挑战。为解决裂隙介质参数推估难的问题,本研究利用集合平滑数据同化与直接采样法融合水文地球物理数据推估裂隙介质参数场,设计多个数值算例,探究该数据同化框架刻画裂隙介质参数场的有效性,分析同化3种不同类型的观测数据对参数推估结果的影响,并探讨裂隙密度以及观测井的数量对参数推估效果的影响。研究结果表明:(1)基于集合平滑数据同化与直接采样法融合水文地球物理数据的方法,可有效地推估裂隙介质水文地质参数空间分布;(2)对比3种类型的观测数据推估结果,可知同时融合水头和自然电位观测数据(水文地球物理数据)的参数推估效果最佳;(3)研究区的裂隙密度以及观测井的数量同样对数据同化结果产生影响,因此建议在实际应用中应选择合理的观测井数量从而获得最优的参数推估方案。该研究可为裂隙介质参数场的刻画提供一种有效的方法,进一步为裂隙水资源的开发和管理提供可靠的理论依据。

Characterizing fractured aquifers plays a crucial role in the issues related to groundwater contamination,and geothermal and hydrocarbon resource exploitation.Due to the heterogeneity of the fractured medium,the permeability of fractured medium generally exhibits significant non-Gaussian characteristics,leading to difficulties and challenges in the estimation of hydrogeological parameters.This study used the ESMDA-DS(ensemble smoother with multiple data assimilation-direct sampling)integrating hydrogeophysical data to explore the effectiveness of the data assimilation framework in portraying the parameter field of the fractured medium and to analyze the influences of assimilating three different types of observation data,the fracture density,and the number of observation wells on the parameter estimation.The results show that the method of ESMDA-DS integrating hydrogeophysical data can estimate the spatial distribution of hydrogeological parameters in the fractured medium effectively.Comparing the estimated results from three types of observation,it finds that fusing the hydraulic head and the self-potential observational data(hydrogeophysical data)has the best effect.The fracture density in the study area and the number of observation wells also affect the data assimilation results.A reasonable number of observation wells is suggested to obtain the optimal parameter estimation scheme in practical applications.This study can provide an effective method for characterizing the parameter field of the fractured medium and a reliable theoretical basis for the development and management of fractured water resources.