Aspects of hydrofracture and heat transfer in a geothermal energy reservoir

Kelly, Amanda Dawn (1992) Aspects of hydrofracture and heat transfer in a geothermal energy reservoir. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The problem of propagating a crack in a linearly elastic substance using a viscous fluid is considered. Conventionally, such problems assume that the elastic stress on the crack wall is supported entirely by the fluid pressure. Here, existing cracks are discussed for the case of the normal stress supported jointly by the fluid pressure and by the elastic deformation of local asperities in the crack. The resulting one-dimensional, second order, non-linear, partial, integro-differential equation is analysed. Analytical and numerical solutions of this equation are obtained using asymptotic analysis and similarity transformations for the cases of extreme values of the non-dimensional parameter, representing the balance between the two possible stress supporting mechanisms. Additionally, the geothermal energy reservoir is considered on a macroscopic scale as a porous medium and the long term heat transfer effects are investigated. The permeability of the rock and the viscosity of the fluid are assumed to have a simple temperature dependence and a condition for the stability of an isotherm is determined.

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