We present results of measurements of the physical properties (thermal conductivity, porosity, permeability, and density) of 65 air-dry sedimentary-rock samples from the cores of six deep wells drilled in the Lena-Anabar interfluve. The rocks are compact low-porosity, almost impermeable siltstones, sandstones, and dolomites mainly of Paleozoic and Precambrian ages. Correlations of thermal conductivity with porosity and bulk density have been established. The available information about the thermal conductivity of rocks as well as the production thermograms recorded after drilling made it possible to estimate the geothermal gradient and heat flow (q) for the Ust'-Ole nekskaya-2370, Charchykskaya-1, Khastakhskaya-930, and D'yappal'skaya-1 wells. The gradient was calculated from the temperature values at the lower boundary of the permafrost (0 °C) and at the bottom-hole. The determined heat flow varies from 37 to 70 mW/m². These q estimates are consistent with the available data on the distribution of heat flow in the north of the Siberian Platform. The proposed method for heat flow estimation is worthy of use in other northern regions of Siberia for obtaining more geothermal data.