The study on mechanism of water–rock reaction in shale oil formation rich in alkaline minerals in Mahu Sag by using supercritical CO2
Yamin Wang A * and Kouqi Liu AA
Dr Yamin Wang is currently working as a postdoc at the Institute of Energy, Peking University. Her current research is related to the shale oil mobility analysis. Dr Yamin Wang is also interested in microscopic pore structure description, water-mineral reaction and CO2 storage feasibility analysis. She completed her PhD degree from the School of Minerals and Energy Resources Engineering, University of New South Wales (UNSW) in 2021 and her Master’s Degree from UNSW in 2017. |
Dr Kouqi Liu is the assistant professor at the Institute of Energy, Peking University. His research interests include multi-scale rock mechanics (from nanoscale to macroscale), unconventional resources analysis (petrophysics and reservoir characterisation). He completed his PhD degree from University of North Dakota. Dr Liu was selected as top 2% scientist in the world in 2022. |
Abstract
Due to unforeseen circumstances, the authors of this paper did not present at the Australian Energy Producers Conference & Exhibition.
The Mahu Sag of Junggar Basin, China is rich in alkaline minerals. Generally, the water–rock reactions between hydraulic fluid and alkaline minerals during the hydraulic fracturing process will lead to the precipitation of minerals and block the pore or wellbore, thereby affecting the recovery efficiency. Supercritical carbon dioxide (ScCO2) regarded as a fracturing fluid can significantly improve the recovery of shale oil resources, but there is limited research on the reaction of ScCO2 to water and rock in shale samples rich in alkaline minerals. Therefore, ScCO2 treatment experiments were conducted on shale samples rich in alkaline minerals under 80°C and 10 MPa. Before the experiments, X-ray powder diffraction (XRD) was applied to characterise the mineral properties of the three shale samples. In addition, the duration time of ScCO2 treatment was set at 7 and 20 days to observe the treatment time impacts on the pore structure. Scanning electron microscopy (SEM) analysis and the Mann–Whitney U test were conducted before and after ScCO2 treatment. SEM images show the changes in pore structure. Opening pores are observed due to the interaction between the alkaline mineral and ScCO2. The Mann–Whitney U test shows the changes in fracture toughness. The changes in pore structure also play an important role in fracture toughness. This study investigated the ScCO2 impacts on shale samples rich in alkaline minerals and the analysis of changes in pore structure and fracture toughness can provide theoretical and data evidence to enable on-site optimisation of the ScCO2 fracturing scheme.
Keywords: alkaline mineral, fracture toughness, interaction, Mann–Whitney U test, pore structure, shale, supercritical CO2, treated time.
Dr Yamin Wang is currently working as a postdoc at the Institute of Energy, Peking University. Her current research is related to the shale oil mobility analysis. Dr Yamin Wang is also interested in microscopic pore structure description, water-mineral reaction and CO2 storage feasibility analysis. She completed her PhD degree from the School of Minerals and Energy Resources Engineering, University of New South Wales (UNSW) in 2021 and her Master’s Degree from UNSW in 2017. |
Dr Kouqi Liu is the assistant professor at the Institute of Energy, Peking University. His research interests include multi-scale rock mechanics (from nanoscale to macroscale), unconventional resources analysis (petrophysics and reservoir characterisation). He completed his PhD degree from University of North Dakota. Dr Liu was selected as top 2% scientist in the world in 2022. |
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