Existence of convective threshold and its role on temperature in reactive flow through fractured rocks: a simulation study in 2D

Abstract

A reactive fluid flowing through porous or fractured rocks causes changes in its porosity and permeability. Experimental studies on the effects of reactive flow in porous systems are normally confined to finite size rock samples in laboratories as actual field data is not sufficiently available. Such laboratory data and simulations based on them, may not always correctly predict or explain changes that take place in rock basins in geological time. In this study we simulate two cases- transient and steady. In a transient case, reactions occur as soon as a reactive fluid is injected into the rock, whereas in the steady case, reactions begin only after the injected fluid percolates through the sample length. The transient case is comparable to real rock basins, while the steady case mimics the situation in laboratory experiments. Variation of the hydrodynamic parameters such as porosity, permeability and surface area, and their inter-relationships at different temperatures, are discussed in both cases. We establish that for every temperature, there exists a threshold flux above which the two cases give similar results. Prediction of changes in rock property due to reactive flow in real situations can be made from laboratory experiments provided the flux is kept above this threshold value. When the fluid flux is kept above this threshold value, the porosity-permeability relation follows a power law behaviour. While the threshold flux is independent of temperature and channel width, the exponent of the power law is a slow decreasing function of temperature.