In-Situ Field Experiment Study of Thermal Expansion and Asphaltene Blockage Effects in Fuyu Oil Shale
Bin Zhu, Wei Guo, Youhong Sun, Sunhua Deng, Chaofan Zhu, Yuan Wang, Qiang Li
Abstract
Oil shale in-situ conversion has received considerable attention due to its potential for commercialization. However, most in-situ conversion technologies remain confined to theoretical studies and laboratory research. Topochemical heat technology (TSA), an in-situ conversion technology, heats oil shale under a nitrogen atmosphere and efficiently pyrolyzes it into shale oil and gas products in ambient air conditions. This study presents two in-situ field experiments conducted using TSA in Fuyu oil shale. It interprets the real-time qualitative and quantitative thermal expansion and asphaltene blockage effects under nitrogen and air atmospheres. The results showed that during heating nitrogen injection in technical step 2 (TS2), the estimated permeability decreased by 53.4%, from 2.53 to 1.18 mD, significantly affecting heat exchange efficiency. When injecting ambient air, the estimated permeability sharply increased from 1.18 to 7.83 mD, which is 5.63 times higher than during nitrogen heating, and then fluctuated between 0 and 7.83 mD. Additionally, several seepage channel blockages occurred in TS2 due to asphaltene precipitation. In this study, we explicitly illustrated the mechanism of thermal expansion and asphaltene blockage effects and solved these problems by adjusting injecting parameters. The findings provide a valuable reference for commercializing oil shale in-situ conversion.