Equivalence of Discrete Fracture Network and Porous Media Models by Hydraulic Tomography

Yanhui Dong, Yunmei Fu, Tian Chyi Jim Yeh, Yu Li Wang, Yuanyuan Zha, Liheng Wang, Yonghong Hao

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Hydraulic tomography (HT) has emerged as a potentially viable method for mapping fractures in geologic media as demonstrated by recent studies. However, most of the studies adopted equivalent porous media (EPM) models to generate and invert hydraulic interference test data for HT. While these models assign significant different hydraulic properties to fractures and matrix, they may not fully capture the discrete nature of the fractures in the rocks. As a result, HT performance may have been overrated. To explore this issue, this study employed a discrete fracture network (DFN) model to simulate hydraulic interference tests. HT with the EPM model was then applied to estimate the distributions of hydraulic conductivity (K) and specific storage (Ss) of the DFN. Afterward, the estimated fields were used to predict the observed heads from DFN models, not used in the HT analysis (i.e., validation). Additionally, this study defined the spatial representative elementary volume (REV) of the fracture connectivity probability for the entire DFN dominant. The study showed that if this spatial REV exists, the DFN is deemed equivalent to EPM and vice versa. The hydraulic properties estimated by HT with an EPM model can then predict head fields satisfactorily over the entire DFN domain with limited monitoring wells. For a sparse DFN without this spatial REV, a dense observation network is needed. Nevertheless, HT is able to capture the dominant fractures.

Original languageEnglish (US)
Pages (from-to)3234-3247
Number of pages14
JournalWater Resources Research
Volume55
Issue number4
DOIs
StatePublished - Apr 2019

Keywords

  • discrete fracture network
  • hydraulic tomography
  • representative elementary volume

ASJC Scopus subject areas

  • Water Science and Technology

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