Petrophysical Anisotropies: Relation Between Properties and Influence in Peri-Volcanic Reservoir Modelisation and Simulation

Abstract

Peri-volcanic reservoirs can be a high-enthalpy source of energy for geothermal exploitation at relative shallow depth, and be a solution to grow energetic independence in some countries. In real reservoir, the architecture is heterogeneous due to deposition process (lava flows, volcano-sedimentary flows, ash deposit, etc.) but also by the development of fracture network and supports highly heterogeneous petrophysical properties, like permeability or thermal conductivity. But these properties are also anisotropic due to the direction of setting up; this is superimposed on the heterogeneity making the modelling of the flow (fluid and heat) more complex. In many models, petrophysical properties are considered isotropic. We establish here anisotropic preferential directions in some volcanic and volcano-sedimentary samples using thermal conductivity, P-wave propagation speeds, permeability and magnetic susceptibility. We create a simple theoretical model based on real dataset from the Bouillante geothermal field (Guadeloupe, Lesser Antilles), and integrate petrophysical measured properties. We finally observe the influence of petrophysical anisotropies integrating the model in Tough2 software in order to simulate thermal and fluid transfers in the reservoir. These simulations highlight the importance of anisotropies in horizontal transfers.