Abstract
In this work, the hydromechanical modeling of the fractured rock masses was conducted based on a new numerical simulation method named as embedded fracture continuum (EFC) approach. As the principal advantage, this approach allows to simplify the meshing procedure by using the simple Cartesian meshes to model the fractures that can be explicitly introduced in the porous medium based on the notion of fracture cells. These last elements represent the grid cells intersected by at least one fracture in the medium. Each fracture cell in the EFC approach present a continuum porous medium whose hydromechanical properties are calculated from ones of the matrix and ones of the intersected fractures, thanks for using the well-known solution of the joint model. The determination of the hydromechanical properties of the fracture cells as presented in this work allows to provide the theoretical base and to complete some simple approximations introduced in the literature. Through different verification tests, the capability of the developed EFC approach to model the hydromechanical behavior of fractured rock was highlighted. An analysis of different parameters notably the influence of the fracture cell size on the precision of the proposed approach was also conducted. This novel approach was then applied to investigate the effective permeability and elastic compliance tensor of a fractured rock masses taken from a real field, the Sellafield site. The comparison of the results calculated from this approach with ones conducted in the literature based on the distinct element code (UDEC) presents a good agreement. However, unlike the previous studies using UDEC, which limits only in the case of fractured rock masses without dead-end fractures, our approach allows accounting for this kind of fractures in the medium. The numerical simulations show that the dead-end fractures could have a considerable contribution on the effective compliance moduli, while their effect can be neglected to calculate the overall permeability of the of fractured rock masses.
Highlights
Evaluation of effective mechanical and hydraulic properties of a geological reservoir, represented as porous rock masses with complex fracture networks, is a major issue in many engineering applications such as oil and gas field recovery, CO2 storage, and geothermal exploitation to just mention a few. e porosity of the matrix constitutes the primary porosity and the essential storage capacity of the reservoir, while the capacity storage of fractures represents only some fraction of the total porosity
Our attention is focused to the results evaluated from the embedded fracture continuum (EFC) approach, which were conducted on the two other models using the uniform and nonuniform meshes and the isotropic approximations of the fracture cell properties
We introduce in this work a new numerical simulation method to model the coupled hydromechanical behavior of fractured porous media. is method called the embedded fracture continuum (EFC) approach allows to model explicitly the embedded fractures network in the continuum porous media by using the fracture-cell concept
Summary
Evaluation of effective mechanical and hydraulic properties of a geological reservoir, represented as porous rock masses with complex fracture networks, is a major issue in many engineering applications such as oil and gas field recovery, CO2 storage, and geothermal exploitation to just mention a few. e porosity of the matrix constitutes the primary porosity and the essential storage capacity of the reservoir, while the capacity storage of fractures represents only some fraction of the total porosity. Albeit a huge number of studies on fractured rock masses in the past, their modeling is yet a challenging and dynamic research topic, with two principal trends grouping continuum and discontinuum approaches [3,4,5,6,7,8,9,10]. In the former approach, the fractured medium is considered as an equivalent continuum medium whose properties are derived from an Advances in Civil Engineering appropriate upscaling procedure by using a homogenization technique. The homogenization-based continuum model may not take into account the connectivity effect of fractures, the effect of clustering and spatial distribution of fractures, or the individual characteristics of a fracture since these characteristics are, at best, taken into account through some statistical features of all crack sets
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