Tight formations or the reservoir rocks with extremely low permeability, make vast hydrocarbon fields in the United States and worldwide. In contrast to conventional reservoirs, production from tight formations is only economic when such formations are hydraulically fractured. Economic production from tight formations relies on the existence of a network of connecting fractures in the rock to create a more volumetric pattern of fracture. To achieve this goal, we have proposed a novel method for fracturing rock by thermal means, in which the rock is frozen prior to hydraulic fracturing, leading to a reduction of effective stress and creation of thermal cracks. The question is how much is the effective rock permeability improved by cooling down the hot reservoir. We use the discrete element method (DEM) to obtain a network of thermal fractures as the rock is frozen. The permeability can then be calculated using a pore network model which is not the subject of this paper. Here we present the Discrete Element Method (DEM) analysis for thermal fracturing and show the effect of main parameters involved in the solutions obtained from the DEM, including the stiffness of rock.