Marine geothermal study in shallow stratigraphic wells on the Kara sea shelf: high-resolution thermal conductivity and temperature data

Abstract

For the first time in the marine geothermal research practice, multiscale rock heterogeneity and anisotropy were studied with continuous thermal property profiling on whole core column from shallow stratigraphic wells on the Kara Sea shelf that improved heat flow assessment. The thermophysical core logging technology, which allows specialists to provide continuous non-destructive profiling of rock thermal properties with spatial resolution of 1 mm, was utilized for the first time in marine wells. This approach yielded high-quality data on thermal conductivity, volumetric heat capacity, and thermal diffusivity for all drilled 916 full-size core samples, accounting for their thermal heterogeneity and anisotropy. Additionally, 30 core samples were selected based on thermal profiling results for extended thermophysical studies: 25 samples were scanned after additional saturation, 5 samples were prepared and studied within the temperature range from 20 to 80 °C using the divided bar technique, and 5 samples were studied at increased up to 5 MPa uniaxial pressure. Heat flow was estimated using the equivalent thermal conductivity, which was determined accounting for each core sample length, macro- and microanisotropy of the rocks, the core decompression, the drying of samples during transportation and storage, and thermobaric conditions of the drilled sediments. The research aims to create a database on geothermal characteristics to improve the reliability of hydrocarbon exploration and development on the studied territory of the Kara Sea shelf. The applied technology for experimental geothermal research allows specialists for extensive and more representative studies of the subsurface geothermal characteristics on the shelf, compared to the traditional approaches that rely on measurements in near-bottom sediments.