The Role of Water in Enhancing In-Situ Hydrogen Production from Shale Oil

Abstract Over the past two decades, shale oil has emerged as a major contributor to the global oil market. Nevertheless, approximately 90% of shale oil resources remain unrecovered due to geological constraints and technological limitations, resulting in low overall energy efficiency. Recent studies have demonstrated that electromagnetic (EM) heating can effectively initiate the in-situ conversion of shale oil into hydrogen, enabling both the extraction of such unrecovered hydrocarbons and the direct production of high-purity hydrogen within shale reservoirs. However, the role of water—commonly present in shale formations—has been largely overlooked in prior research. This study quantitatively examines the impact of water on shale oil conversion to in-situ hydrogen under EM heating. Experimental results show that in oil-water mixtures with a 1:1 weight ratio, water not only doubles hydrogen yield but also increases hydrogen purity to 50% by promoting the conversion of short-chain hydrocarbons to hydrogen. Isotopic tracing using deuterium oxide (D2O) reveals that 61.5% of the produced hydrogen originates from shale oil, while the remaining 38.5% is associated with water. This indicates that water plays a critical role in secondary reactions (i.e., coke gasification and water-gas shift reactions) to generate extra hydrogen and reduce coke/carbon buildup within the reservoir, potentially improving borehole permeability and enabling sustained hydrogen production over time. Overall, this study provides crucial insights into water's dual role as both a hydrogen source and a reaction facilitator, advancing the technological readiness of in-situ hydrogen production from water-bearing shale oil reservoirs.