A major concern in development of fractured reservoirs in Enhanced Geothermal Systems (EGS) is to achieve and maintain adequate injectivity, while avoiding short-circuiting flow paths. The injection performance and flow paths are dominated by fracture rock permeability. The evolution of fracture permeability can be made by change in temperature or pressure induced rock deformation and geochemic...

Vapor-dominated geothermal systems, including The Geysers and Larderello, have experienced significant increases in noncondensible gas during their productive histories. A depletion model has been developed to explain these increases. In the model, the low permeability of the reservoir rock matrix initially retards the flow of vapor through the matrix to fractures due to the plugging effect of ...

AEiSTRACT Reinjection of spent geothermal brine is a common means of disposing of geothermal effluents and maintaining reservoir pressures. Contrary to the predictions of twefluid models (tweviscosity) of nonisothermal injection, an increase of injectivity, with continued injection, is often observed. Injectivity enhancement and thermally-affected pressure transients are particularly apparent i...

Background Engineered or enhanced geothermal systems (EGS) have been promoted as a technology that exploits geothermal heat and power production from regions of the crust devoid of shallow high enthalpy reservoirs (also referred to as high-grade hydrothermal resources) (e.g., MIT 2006). The status of EGS development was reviewed by Breede et al. (2013) who reported on 14 EGS projects that were ...

Gas concentrations and ratios in 110 analyses of geothermal fluids from 47 wells in the Cos0 geothermal system illustrate the complexity of this two-phase reservoir in its natural state. Two geographically distinct regions of single-phase (liquid) reservoir are present and possess distinctive gas and liquid compositions. Relationships in soluble and insoluble gases preclude derivation of these ...

This paper describes the applications of the fractured continuum model to the different enhanced geothermal systems reservoir conditions. The capability of the fractured continuum model to generate fracture characteristics expected in enhanced geothermal systems reservoir environments are demonstrated for single and multiple sets of fractures. Fracture characteristics are defined by fracture st...

The current Enhanced Geothermal Systems (EGS) with a fractured reservoir undergoes several practical issues, such as scaling in the wellbore, the mass flow loss into the reservoir, and the challenge in designing the placement of production wells. In this paper, novel underground well pattern systems were proposed for geothermal energy exploitation. A numerical model of two kinds well pattern sy...

Estimates of temperatures, past and present, in geothermal reservoirs can be made by using now standard mineralogical techniques, including fluid inclusion geothermometry, vitrinite reflectance, calc-silicate and clay occurrence, the extent of clay interlayering, and measuring clay crystallinity. Recent studies of clays in 60 drillcores from 6 wells at Wairakei, for example, show an inverse rel...

As a new modeling procedure of geothermal energy extraction systems, the authors present two dimensional and three dimensional modeling techniques of subsurface fracture network, based on fractal geometry. Fluid flow in fractured rock occurs primarily through a connected network of discrete fractures. The fracture network approach, therefore, seeks to model fluid flow and heat transfer through ...