In the quest to optimize carbon capture, utilization, and storage (CCUS) and enhance oil recovery (EOR) processes, researchers are delving deep into the complexities of low-permeability sandstone reservoirs (LPSR). A groundbreaking study led by Taskyn Abitkazy from the Research Institute of Petroleum Exploration and Development, CNPC, Beijing, China, published in the journal Energies, sheds new light on the role of interlayers in these reservoirs. These interlayers, which can be impermeable or ultra-low-permeability, significantly impact the flow dynamics of CO2 during flooding processes, posing both challenges and opportunities for the energy sector.
The study, which integrates geological and microscopic analyses, reveals that interlayers divide LPSR into complex, discontinuous flow units. This compartmentalization can hinder CO2 migration and storage, affecting both oil recovery and the effectiveness of CCUS efforts. Abitkazy’s team employed a multi-faceted approach, including core analysis, reservoir petrography, field emission-scanning electron microscopy (FE-SEM), and energy dispersive spectroscopy (EDS), to characterize these interlayers. They also utilized 3D geological modeling to map out the spatial distribution and characteristics of these barriers within the reservoir.
The findings are compelling. Two distinct types of interlayers were identified: petrophysical interlayers and argillaceous interlayers. Petrophysical interlayers have a porosity of less than 11% and permeability ranging from 0.006 to 0.03 mD, while argillaceous interlayers have a porosity of 1–8% and permeability of 0.001–0.005 mD. The study also revealed that the thickness and continuity of these interlayers significantly influence CO2 sealing capacity and oil displacement efficiency.
Numerical simulations conducted over a 10-year period showed that optimal sealing occurs with petrophysical barriers ≥ 4 m and argillaceous barriers ≥ 1.5 m thick. However, thicker interbeds can constrain the vertical flooding area, reducing production ratios compared to homogeneous reservoirs. “Increased interbed thickness and area can mitigate CO2 invasion time while constraining gravity override and dispersion effects, enabling horizontal oil displacement and consequently enhancing production,” Abitkazy explained.
The commercial implications of these findings are vast. For oil and gas companies, understanding and managing interlayers could lead to more efficient CO2-EOR processes, improving both oil recovery rates and the effectiveness of CCUS initiatives. This could translate into significant cost savings and enhanced environmental performance, aligning with global sustainability goals.
The study also highlights the need for further research into interlayer configurations at various positions, angles, and random arrangements. This could pave the way for more advanced development strategies, optimizing CCUS-EOR applications in LPSR worldwide. As the energy sector continues to evolve, insights from this research could shape future developments, offering a robust theoretical foundation for CO2 utilization in challenging geological settings.
The article, published in the journal Energies, marks a significant step forward in our understanding of LPSR and the role of interlayers in CO2 flooding processes. By providing a comprehensive characterization and impact analysis, Abitkazy and his team have opened new avenues for exploration and innovation in the energy sector.