Various Enhanced Oil Recovery (EOR) techniques are used to increase oil recovery factors from reservoirs. Thermal EOR methods, mainly steam injection, are widely used in heavy oil reservoirs. High temperature reduces the viscosity of heavy oil, and facilitates fluid flow to the production wells. Also, high-pressure injection increases the pore pressure which reduces the rock strength; combined with thermally induced stresses, shear, fracture, and dilation can take place at many scales. Naturally fractured carbonate reservoirs formed of brittle rocks (e.g. calcite - CaCO₃) contain more than 2.3 trillion barrels of heavy oil. Their behavior is simulated with various macro-scale continuum methods, and discontinuum methods at various scales help understand macro-scale jointed rock mass behavior as well. Little is done at the microscale, despite clear evidence of damage related to changing loads and temperatures, so we use Molecular Dynamics (MD) as a nano-micro scale discontinuum method. To explore calcite's thermo-mechanical behavior, a MD model of pure CaCO₃ is developed, and numerical simulations of uniaxial tests carried out at two different temperatures (300K and 400K). Among other results, the MD modeling shows that the yield-point strain value is about 1.5 times larger at the higher temperature compared to the lower temperature, in accordance with typical rock testing results. MD may aid in progress toward a better understanding and simulation of small-scale rock damage, in addition to the large scale issues modeled conventionally.