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Development of a new semi-analytical model for cross-borehole flow experiments in fractured media

February 1, 2015

Analysis of borehole flow logs is a valuable technique for identifying the presence of fractures in the subsurface and estimating properties such as fracture connectivity, transmissivity and storativity. However, such estimation requires the development of analytical and/or numerical modeling tools that are well adapted to the complexity of the problem. In this paper, we present a new semi-analytical formulation for cross-borehole flow in fractured media that links transient vertical-flow velocities measured in one or a series of observation wells during hydraulic forcing to the transmissivity and storativity of the fractures intersected by these wells. In comparison with existing models, our approach presents major improvements in terms of computational expense and potential adaptation to a variety of fracture and experimental configurations. After derivation of the formulation, we demonstrate its application in the context of sensitivity analysis for a relatively simple two-fracture synthetic problem, as well as for field-data analysis to investigate fracture connectivity and estimate fracture hydraulic properties. These applications provide important insights regarding (i) the strong sensitivity of fracture property estimates to the overall connectivity of the system; and (ii) the non-uniqueness of the corresponding inverse problem for realistic fracture configurations.

Publication Year 2015
Title Development of a new semi-analytical model for cross-borehole flow experiments in fractured media
DOI 10.1016/j.advwatres.2014.12.002
Authors Delphine Roubinet, James Irving, Frederick D. Day-Lewis
Publication Type Article
Publication Subtype Journal Article
Series Title Advances in Water Resources
Index ID 70193748
Record Source USGS Publications Warehouse
USGS Organization OGW Branch of Geophysics; Toxic Substances Hydrology Program