In the heart of China’s Ordos Basin, a groundbreaking study is unraveling the intricate dance between shale and supercritical CO2 (ScCO2), with implications that could reshape the energy sector’s approach to carbon capture and storage. Led by Lili Jiang from the College of Petroleum Engineering at China University of Petroleum (Beijing), the research delves into the microscopic world of shale, exploring how ScCO2 interacts with and alters its pore structure.
The study, published in the Journal of Natural Gas Science, focuses on the Chang 73 submember of the Yanchang Formation, a significant shale play in the Ordos Basin. By employing a combination of organic geochemical analyses, low-temperature gas adsorption experiments, and nuclear magnetic resonance (NMR) scanning, Jiang and her team have painted a detailed picture of shale’s microporous structure and its fractal characteristics under ScCO2 treatment.
“Our findings show that ScCO2 treatment significantly impacts the shale’s pore structure,” Jiang explains. “The total organic carbon (TOC) content decreases, while the quartz content increases, and the contents of clay minerals and feldspar decrease. This suggests that the mineral composition of shale is highly sensitive to pressure changes, more so than temperature variations.”
The research reveals that shale pores are primarily distributed in the micropore (0–2 nm) and mesopore (2–50 nm) ranges, which contribute significantly to the specific surface area. Macropores (>50 nm), though fewer, play a crucial role in the total pore volume. Post-ScCO2 treatment, the total specific surface area of shale samples decreases, while total pore volume, average pore diameter, and effective porosity increase.
This study highlights the multi-scale fractal characteristics of shale pores, with micropores displaying higher fractal dimensions than meso- and macropores. After ScCO2 treatment, fractal dimensions at all scales decline, indicating an improvement in the complexity of the shale pore structure. “The fractal dimension of micropores is significantly positively correlated with TOC content, while meso- and macropore fractal dimensions have a stronger correlation with quartz and clay mineral content,” Jiang notes.
The implications of this research for the energy sector are profound. Understanding how ScCO2 interacts with shale at a microscopic level is crucial for optimizing carbon capture, utilization, and storage (CCUS) technologies. By identifying the intrinsic and external factors that influence shale pore structures, energy companies can make more informed decisions about target layers for CCUS projects.
“This study provides a valuable scientific basis and practical guidance for the optimal selection of CCUS target layers,” Jiang concludes. As the energy sector continues to grapple with the challenges of reducing carbon emissions, research like Jiang’s offers a beacon of hope, guiding the way towards more effective and efficient carbon storage solutions.
In the quest for a sustainable energy future, the microscopic world of shale and its interaction with ScCO2 could hold the key to unlocking new possibilities for the energy sector. As Jiang’s research continues to shed light on this complex relationship, the energy sector can look forward to more informed and strategic approaches to carbon capture and storage.