Fracture Network and Fluid Flow Imaging for Enhanced Geothermal Systems Applications from Multi-Dimensional Electrical Resistivity Structure

Wannamaker, Philip E.¹ 

[1] Univ. of Utah, Salt Lake City, UT (United States)

关键词: magnetotellurics;    finite elements;    topography;    forward modeling;    inversion;   

DOI  :  10.2172/1243367
RP-ID  :  DOE-UUEGI--EE0002750-1
PID  :  OSTI ID: 1243367
Others  :  Other: 8015813547

学科分类：再生能源与代替技术

美国|英语

来源: SciTech Connect

【 摘 要 】

We have developed an algorithm for the inversion of magnetotelluric (MT) data to a 3D earth resistivity model based upon the finite element method. Hexahedral edge finite elements are implemented to accommodate discontinuities in the electric field across resistivity boundaries, and to accurately simulate topographic variations. All matrices are reduced and solved using direct solution modules which avoids ill-conditioning endemic to iterative solvers such as conjugate gradients, principally PARDISO for the finite element system and PLASMA for the parameter step estimate. Large model parameterizations can be handled by transforming the Gauss-Newton estimator to data-space form. Accuracy of the forward problem and jacobians has been checked by comparison to integral equations results and by limiting asymptotes. Inverse accuracy and performance has been verified against the public Dublin Secret Test Model 2 and the well-known Mount St Helens 3D MT data set. This algorithm we believe is the most capable yet for forming 3D images of earth resistivity structure and their implications for geothermal fluids and pathways.