Parallel Fractures Model for Tracer Flow Through Geothermal Reservoirs - Preliminary Results

A parallel fractures model, having equal width and spacing, has been developed to study the flow of tracers through naturally fractured geothermal reservoirs. The model is capable of handling either a single fracture or a system of two or more parallel fractures, interacting with associated porous bodies. The reservoir is treated as being composed of two regions a mobile region where diffusion and convection are allowed and a stagnant or immobile region where only diffusion and adsorption are allowed. Both regions are interconnected by means of a very thin fluid film contained within the immobile region which controls the fluid and mass transfer between both regions. The mobile region represents the system of fractures, where tracer is free to flow reaching high velocities, whereas non-homogeneities of the reservoir rock, such as microfractures and dead-end fractures are represented by means of an equivalent porous body where fluid remains immobile. The boundary-value problem for the system is stated and its solution into Laplace’s space is presented. Numerical inversion of this solution was performed by means of the Stehfest algorithm. Preliminary results showing results obtained from the proposed model are included. Further work is underway to apply the model for interpretation of actual tracer flow field data. 4 figs., 1 tab., 11 refs