Effect of leakage pathway flow properties on thermal signal associated with the leakage from CO 2 storage zone

Temperature can be used to detect the leakage of fluids from the CO 2 storage zone. CO 2 leakage is accompanied by temperature cooling due to the Joule‐Thomson effect. We investigate the strength of the temperature signals for two scenarios in which leakage occurs either through a leaky well or through a leaky fault. In addition, we identify and analyze the major mechanisms contributing to the temperature signal. A larger pressure drop at shallower depths and thinner caprock thickness can induce more cooling and hence a stronger temperature signal. Furthermore, we study the effect of capillary pressure on the temperature signal as it can reduce the Joule‐Thomson effect after CO 2 leakage. The hydraulic properties of the leakage pathway, being a fractured or non‐fractured matrix porous medium, are investigated using dual‐porosity/dual‐permeability models and considering identical permeability to the single porous medium case. The leakage rate increases significantly for dual‐medium models. The further sensitivity analysis contains the effects of leakage pathway flow properties: fracture permeability, fracture spacing, and porosity. We also extend our models to consider the injection zone as a naturally fractured reservoir, and further incorporate an above‐zone monitoring interval as another naturally fractured reservoir as well. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd.