Modeling tracer flowback behaviour for a fractured vertical well in a tight formation by coupling fluid flow and geomechanical dynamics

Abstract

In this work, a pragmatic technique has been developed to describe tracer flowback behaviour for a vertically fractured well in a tight formation by coupling fluid flow and geomechanical dynamics. More specifically, the Barton-Bandis model is employed to describe the relationship between effective stress and fracture permeability, while tracer flowback profiles, which can reveal the fracture properties, are quantified by taking tracer dispersion and adsorption into account. Subsequently, this method considering two main mechanisms (i.e., tracer flow behaviour and fracture propagation dynamics) is separately validated with previous analytical solutions and then extends its application to a field case. In addition to tracer flowback concentration, the tracer recovery factor (TRF) is generated to analyze the tracer flowback behaviour. With considering geomechanics, the TRF is nearly 20% higher than that without considering geomechanics. During the flowback period, tracer concentration profiles appear to be unimodal for reservoirs with a single fracture, while tracer concentration increases quickly at the initial stage and then decreases slowly as time proceeds. An increase in matrix permeability increases tracer flowback concentration and the TRF. A larger tracer dispersion coefficient leads to earlier arrival time for the tracer flowback concentration peak together with a lower TRF. Also, the stronger the tracer adsorption is, the lower the tracer flowback concentration and the TRF will be. A higher Young's modulus results in a lower tracer flowback concentration and TRF. An increase in minimum horizontal stress increases tracer flowback concentration. Other parameters, including maximum horizontal stress, fracture closure permeability, and normal fracture stiffness, are also examined and analyzed though less sensitive.