Experimental investigation of thermal expansion of organic-rich shales

Abstract Experimental data on thermal expansion of rocks are necessary for many applications involving wellbore stability analysis, designing radioactive waste repositories, etc. Such information is especially actual for organic-rich shales that exhibits significant thermal anisotropy and heterogeneity and were not studied comprehensively previously. The coefficient of linear thermal expansion (CLTE) of 23 shale samples from three wells of three oilfields of the Bazhenov and Abalak formations (West Siberia, Russia) was studied with a quartz dilatometer specially adapted for the measurements on standard core plugs. Differential CLTE of shales was determined within temperature range 25–300 °C through every 25 °C for directions parallel and perpendicular to rock bedding. Strong correlations between the CLTE, thermal conductivity, and total organic carbon were established. Detailed profiles of CLTE along studied wells were obtained due to application of the optical scanning technique. These profiles fit well with total organic carbon obtained with pyrolysis. CLTE anisotropy was assessed for organic-rich shale samples together with thermal conductivity anisotropy. The thermal conductivity measurements before and after heating allowed estimation of structural changes in rock samples during heating.