No abstract

A finite element method for the solution of two‐dimensional transient dispersive‐convective transport of nonconservative solute species in fractured porous media is presented. A two‐nodal point one‐dimensional transport element for fractures is developed which provides a number of advantages relative to conventional fracture representation by two‐dimensional continuum elements. To eliminate the oscillatory behavior of convective‐dominated transport which is a more likely occurrence in fracture, a very efficient one‐dimensional upstreaming method along with a two‐dimensional method is implemented. Validity of the numerical scheme is established by comparison with existing one‐ and two‐dimensional analytic solutions.

Abstract. The determination of the storage capacity of fractures in crystalline rocks by means of hydraulic injection tests is studied by coupled hydromechanical finite element simulations. The results verify that the storage is related to the fracture opening, which is dependent on the combined stiffness of the fracture and the ambient rock mass. In most practical cases the storage is entirely controlled by the normal stiffness of the fractures. The strong coupling to the fracture opening implies that the storage capacity can be estimated from the pressure dependency of the fracture aperture in a high-pressure injection test. Such high-pressure injection tests can be conducted in addition to a conventional low-pressure test to independently determine the storativity of the fracture. This provides an additional validation of the evaluated storativity, which implies not only that the value is more accurately assessed but also that other hydraulic properties can be determined more unambiguously. The method of high-pressure injection testing is applied in field experiments to deep fractures in granitic rocks at two sites, and its usefulness is demonstrated in an analysis of the field data. In this paper, hydraulic injection tests are simulated by coupled hydromechanical modeling to study the interplay between mechanical parameters contributing to the storage of water. This leads to the suggestion of using a high-pressure injection test as a method for an independent determination of the fracture storativity. A high-pressure test is here defined as a hydraulic injection test that induces elastic fracture opening, thus changing the fracture permeability considerably, but without causing hydraulic fracturing. Thus the well pressure is kept below lithostatic pressure. The method is applied to field experiments at two sites in granite, and the evaluated storativity is presented as a function of effective normal stress. (1) 2551 Transmissivity and

The fundamentals of the theory of consolidation and thermoelasticity are recast into the formulation of a phenomenon called thermohydroelasticity. Subsequently, a variational principle and Galerkin formulation are combined with the finite element method to develop a new technique to investigate coupled thermal‐hydraulic‐mechanical behavior of liquid‐saturated, fractured porous rocks. A code‐to‐code verification of the method is performed. Finally, the environment of a heater emplaced in hard rock is simulated. The effects of the coupled thermal stresses in the fractured rock are evident from the dramatic reduction of permeability due to the deformation of the fractures. These results can improve the under‐standing of observations and displacement measurements made in the in situ experiments at the Stripa mine in Sweden.

No abstract