The thermal conductivity of rocks is a property necessary to be determined at the beginning of the exploitation of oil and gas deposits, both for the design of secondary extraction (hot water injection, steam) and for the development of tertiary extraction technologies (CO2 injection, injection flue gas, and initiation of underground combustion). In this chapter, we present a new method for determining the thermal conductivity of rocks and we also analyzed the relationships between this parameter and the properties of oil and gas collector rocks (density, porosity).