A numerical simulator to estimate hydrological parameters of a fractured porous medium using fluorescein thermal decay correction

Abstract

A method that can be used to estimate hydrological parameters of a fracture using fluorescein thermal decay correction is presented. These parameters are porosity, permeability, fracture size, entire reservoir pore volume and reservoir recharge rate. A tracer was pumped into an injection well and its arrival characteristics with respect to time in the production wells monitored. The data was used to generate breakthrough curves which gives tracer effluent history. These curves yielded important information about the reservoir. Resulting fluorescein decays were accounted for by application of numerical modelling and properties of the geothermal system were estimated. The estimates were used to simulate a fracture connecting two wells.

A mathematical model describing the flow of the tracer was solved to generate its flow profile in a fracture. This was done by developing a computer package in Microsoft Visual C++. The profile was matched with the field data by trying out different values of the fracture parameters. The values that almost matched the profile on the field data curve were the required parameters. Porosity was observed to vary between 13 % to 15 %, permeability was found to be 1.8 mm" and permeability thickness of 950 m2. The fracture thickness was estimated to vary between 3 m and 10 meters. Rate of aquifer flow was 1.956 x 10-9 kglm3/sec while entire reservoir pore volume was obtained to be 653520 lit res/sec