Thermal conductivity and heat flow modeling of petroleum exploration and research wells onshore Svalbard

Thermal properties such as thermal conductivity and radiogenic heat production are crucial to provide reliable heat flow estimates, with direct implications on geothermal exploration. Such parameters can be derived from laboratory analyses on drill core samples or estimated from standard wireline logs. Onshore the Arctic archipelago of Svalbard, geothermal energy is being considered as an alternative to the diesel-fueled present-day energy supply. However, reliable thermal conductivity estimates are only available from fully cored research boreholes covering the Late Triassic to Paleogene sedimentary succession. Adequate temperatures for geothermal district heating (80 °C) are only reached at ca. 2 km depth beneath Longyearbyen, Svalbard’s largest settlement. At such depths, the thermal properties of the subsurface are unconstrained. In this contribution, we use petroleum exploration boreholes drilled to depths of up to 3.3 km onshore Svalbard to derive thermal properties from wireline logs for the Carboniferous to Paleogene succession. Lithology logs of ten boreholes were digitized and used as the foundation for thermal modeling. Based on these logs, we implemented two modeling cases: (1) assigning generalized thermal properties by lithology type, and (2) using thermal properties calculated directly from wireline logs, which also require lithological information. Our calculations suggest variable thermal conductivity from 0.4 to 4.2 W/mK, largely controlled by lithology. In the uppermost 1 km, where fully cored research boreholes are available, we compared the calculated thermal properties with the measured data from these boreholes. We observed similar trends between lithology and the calculated thermal conductivity; however, the calculated values are generally slightly lower than the values measured in the laboratory. Subsequently, we use the regional thermal properties as input to 1D heat flow modeling of ten boreholes and a hypothetical deep geothermal borehole beneath Longyearbyen. The calculated heat flow values span from 60 to 147 mW/m 2 , with the highest values obtained from the Raddedalen borehole in Edgeøya. By calculating thermal properties from wireline logs, we allow for more accurate heat flow models, providing valuable insights into the spatial distribution of heat flow across Svalbard and its thermal state. • Thermal conductivity was estimated for petroleum and research boreholes onshore Svalbard using wireline logs. • Thermal conductivity is primarily controlled by the lithology. • 1D heat flow modeling suggests laterally varying heat flow ranging from The calculated heat flow values span from 60 to 147 mW/m2.