DOUBLE POROSITY MODEL WITH TRANSIENT INTERPOROSITY FLOW FOR THE RESPONSE OF TRACERS IN NATURALLY FRACTURED RESERVOIRS, CONSIDERING CONSTANT MASS FLUX INJECTION

In tracer test interpretation, fissured reservoirs are commonly referred to as double porosity systems. Different approaches have been proposed for analyzing their well tracer concentration responses. This work presents a double porosity model with transient fracture-matrix transfer, considering constant mass flux at the injection well, for the interpretation of the observed tracer response in the producing wells for continuous injection of a tracer. A new parameter is presented which represent the gradient of mass flow that governs the fracture- matrix transfer and it is used to characterize the porous media. The solution for the proposed mathematical model was obtained in Laplace space. The numerical inversion was carried out with Stehfest's algorithm. In addition, approximate analytical solution for short and long dimensionless time are obtained, and are compared with the solution obtained by numerical inversion, providing satisfactory results. The values of the numerical inversion were used to generate the "type curve", presented in terms of the dimensionless groups obtained from the approximate analytical solution.