| Title | Application of a Dual-Continuum Model for Simulation of Fluid Flow and Heat Transfer in Fractured Geothermal Reservoirs |
|---|---|
| Authors | Yue HAO, Pengcheng FU, and Charles R. CARRIGAN |
| Year | 2013 |
| Conference | Stanford Geothermal Workshop |
| Keywords | dual-continuum model, fluid flow, heat transfer, fractured rock, geothermal reservoir |
| Abstract | Modeling of fluid flow and heat transfer in fractured rocks can help estimate heat recovery efficiency of an engineered geothermal system (EGS), and therefore represents a critical component for EGS system design and performance evaluation. Fluid flow and thermal transport processes in fractured media are typically considered at discrete-fracture or continuum scales. Although the discrete-fracture approach, explicitly accounting for individual fractures, allows for more accurate description of fracture network systems its practical application at field scales is often computationally limited. For this reason the continuum models (e. g. effective continuum method, multiple interacting continua model) are often used to simulate field-scale fluid flow and heat transfer processes in fractured geothermal reservoirs. As we know heat transfer through fractured rocks is controlled by the interplay between thermal convection in the fractures and conduction in the matrix. This study aims to develop a dual-continuum model with the focus on a rigorous representation of discrete factures and their interaction with surrounding rock matrix, which therefore allows for a reliable prediction of impacts of fracture-matrix interaction on heat transfer in fractured geothermal formations. In this continuum model the fracture and matrix systems are treated as two separate overlapping continua, each of which has its own energy balance equations. The balance equations for two continua are coupled through matrix-fracture heat transfer. An upscaling technique is used to transform discrete fracture characteristics to equivalent fracture continuum parameters, which involves direct mapping of discrete fractures onto continuum grid blocks by calculating grid-based effective permeability tensor. The model is calibrated against a fine-scale discrete-fracture model to further constrain fracture-matrix heat transfer coefficient, leading to an improved calculation of heat exchange between the fractures and matrix. We also apply this approach to simulate the thermal-hydrologic (TH) behaviors of fracture-stimulated geothermal reservoirs.This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. |