Fluids flow within microporous and nanoporous rocks involves several industrial processes such as enhanced oil recovery, geological CO₂ sequestration, and hydraulic fracturing. However, the pore structure of subsurface rocks is complex, and fluid flow is influenced by strong fluid-fluid and fluid-solid interactions, including wettability, interfacial tension, and slip effects. Characterizing this flow processes is costly and challenging through experimental techniques. At meanwhile, pore-scale simulations have been widely employed to investigate complex flow behaviors within microporous and nanoporous media. This work investigates the applications of pore-scale simulation methods for characterizing flow processes in porous rocks considering microscale and nanoscale effects. Two mainstream simulation methods, pore network modeling and direct numerical simulation, are introduced. Their application scenarios encompass immiscible flow, as well as miscible and near-miscible flow involving CO₂ enhanced recovery. Additionally, some explorations of single-phase and multiphase flow processes within nanoporous media are described. Finally, future development of pore-scale simulations is discussed, with a focus on complex transport phenomena involving diffusion, reactions, and dissolution.

Renowned for its organic richness, unconventional shale presents both unique challenges and opportunities for hydrocarbon extraction and various geo-engineering applications, owing to its complex storage, flow, and stimulation properties. It is essential, from a multidisciplinary perspective, to characterize the rock physics response and construct rock physics model for unconventional shale reservoirs. A maturity-constrained rock physics modeling method for shales, in conjunction with geochemical analyses, is proposed, employing the stepwise homogenization method to quantify the scale-dependent elastic and anisotropic behavior of laminated shales. Considering the complex pore structure of shale, combined with the microscale effects of fluid transport, various forces, and microfracture features, the multiphase fluid flow behavior can be accurately characterized. Then, from the perspective of fracturing performance, it is necessary to develop a new fracability evaluation model for unconventional shale reservoirs. This model integrates fracture mechanics theory, the elastic and mechanical properties of rocks, fracturing operations, reservoir geological characteristics, and in-situ stress to thoroughly evaluate fracability. Unconventional petrophysicists must move beyond traditional hydrocarbon evaluation to embrace interdisciplinary approaches, which requires comprehensive understanding and characterization of the storage, flow, and stimulation capacities, thereby optimizing development strategies and maximize resource utilization.

From April 19-22, 2024, the editorial department of Advances in Geo-Energy Research (AGER), in collaboration with several organizations, successfully hosted the first “Geo-Energy Frontier Forum”. The forum was themed around “opportunities and challenges in geo-energy exploration and development” and introduced several innovative organizational approaches such as conference report scheduling, expert invitations, meeting manual, operational modes, and content, achieving notable outcomes. The event expanded AGER’s service capabilities and marked the initiation of the “one-journal-one-forum” mode. Scheduled biennially, the forum aims to establish a high-level academic exchange platform for “geo-energy”, characterized by its comprehensive, strategic, cutting-edge, and innovative focus, fostering interdisciplinary collaboration and development across various professions and industries.

Multiphase flow is a common scenario in industrial and environmental applications. Especially at microscopic scale, accurately describing flow processes is challenging due to fluid-fluid, fluid-solid, and solid-solid interactions. Pore-scale microfluidics and numerical simulation methods considering complex topology are increasingly being applied to study multiphase flow phenomena. This work focuses the recent applications of microfluidic experiments and new numerical simulations in complex flows for enhanced oil recovery. Two types of coupling algorithms are provided to integrate the advantages of pore network model and direct numerical simulation methods. For fines migration, the computational fluid dynamics-discrete element method is proposed to describe the coupling process between fluid and solid particles. Pore-scale microfluidic experiments and simulation methods deals with complex flow processes at micro/nano scales, providing effective solutions for complex industrial processes.

The capillary pressure curve is a crucial basis for studying the pore structure and multiphase flow characteristics in oil and gas reservoirs. Due to the loose and unconsolidated nature of the clayey-silt sediment of natural gas hydrate reservoirs in the South China Sea, conventional methods such as mercury intrusion and centrifugation struggle to obtain capillary pressure curves for these sediments. In this study, X-ray diffraction analysis, scanning electron microscopy, nitrogen adsorption, and water-gas contact angle measurements are utilized to characterize the mineral composition, pore structure, pore size distribution, and wettability of the clayey-silt sediment. Subsequently, the filter paper method from soil mechanics is employed to determine the capillary pressure curve for the clayey-silt samples. The results indicate that the capillary pressure curve obtained through the filter paper method exhibits a saturation range of 18.39%-80.31% and a capillary pressure range of 19.04 to 46,481.42 kPa. It exhibits a distinct two-stage characteristic, where capillary pressure changes rapidly with water saturation below 61.05% and slowly above 61.05%. The pore radius calculated from the capillary pressure curve ranges from 2.41 nm to 5.91 μm. This alignment with the pore ranges obtains from nitrogen adsorption and Scanning Electron Microscopy confirms the accuracy of the obtained capillary pressure curve. Furthermore, in comparison with a literature capillary pressure curve obtained through centrifugation, the paper filtration method covers a broader range, providing better representation of capillary pressure in the multiscale pores of clayey-silt samples.

In shale reservoirs, spontaneous imbibition is an important mechanism of fracturing fluid loss, which has an important impact on enhanced oil recovery and water resource demand. However, spontaneous imbibition behaviors are more complicated to characterize and clarify due to the nanoscale effects of the boundary slip, oil-water interfacial slip, and heterogeneous fluid properties caused by intermolecular interactions. A nanoscale multi-relaxation-time multicomponent and multiphase lattice Boltzmann method was applied to investigate the water imbibition into oil-saturated nanoscale space. The effects of pore size, fluid-surface slip, water film, oil-water interfacial slip, water bridge, and pore structures on the imbibition behaviors in a single nanopore were investigated. Then, the spontaneous imbibition behaviors in nanoporous media based on the pore scale microsimulation parameters obtained from the molecular simulation velocity results were simulated, and the effects of water saturations on imbibition behaviors were discussed. The results show that as the water saturation increases from 0 to 0.1, the imbibition mass in nanoporous media increases because of the oil-water interfacial slip and a completely hydrophilic wall. As water saturation continues to increase, the imbibition mass decreases gradually because the existence of water bridges impedes the water imbibition.

Natural gas hydrate reservoirs in the northern South China Sea primarily comprise clayey silt, making exploitation more challenging relative to sandy reservoirs in other countries and regions. This paper provides an overview of the latest research developments in the exploitation mechanism covering the past five years, focusing on hydrate phase transition, multiphase flow in the decomposition zone, the seepage regulation of reservoir stimulation zone, and production capacity simulation, all of which are relevant to the previously conducted two rounds of hydrate trial production in offshore areas of China. The results indicate that the phase transition of clayey-silt hydrate remains in a dynamic equilibrium, with the decomposition efficiency mainly controlled by the coupling of heat and flow and high heat consumption during decomposition. The decomposition zone exhibits strong hydrophilicity, easy adsorption, and sudden permeability changes. A temperature drop is present that is concentrated near the wellbore, and once a water lock has formed, the gas-phase flow capacity significantly decreases, leading to potential secondary hydrate formation. To enhance permeability and increase production, it is imperative to implement reservoir and temperature field reconstruction based on initial formation alterations, which will further optimize and improve the transport capacity of the reservoir.

Shale oil and gas, as important unconventional resources, have been widely discussed in the last decade. The occurrence characteristics of fluids (oil, gas, and water) in shale reservoirs are closely related to the exploitation of shale oil and gas, therefore the quantitative characterization of fluid occurrence in shale reservoirs has received extensive attention. In this paper, the latest advances and potential challenges on this subject are summarized. With respect to shale oil, the amounts, ratios and micro-distributions of shale oil in different states can be determined using the state equation of liquid and adsorption ratio equation, which contributes to identifying high-quality shale oil reservoirs. However, it is still necessary to strengthen the research on the multi-attribute coupling relationship and oil-rock interaction of shale oil reservoirs, and the determination of occurrence characteristics of adsorbed and free oil under in situ reservoir conditions. In terms of shale gas evaluation, the process analysis method and isotope fractionation method effectively solve the problem of evaluating in situ gas-bearing characteristics of shale, and can accurately estimate the amounts of total, adsorbed and free gas. The quantum physisorption behavior of gas could be a new research direction to reveal the microscopic occurrence mechanism of shale gas. As for shale pore water, a complete evaluation procedure for determining the amounts and micro-distributions of adsorbed and free water in shale matrix pores has been established, which provides insight into the storage and flow of oil and gas. In future work, a study on the quantitative evaluation of water-rock interaction is significant for obtaining the adsorbed and free water under in situ reservoir conditions.

The scientific and engineering challenges of research on porous media have gained substantial attention in recent decades. These intricate issues span different disciplines and fields, manifesting in natural and industrial systems like soils, oil and gas reservoirs, tissues, plants, etc. Meanwhile, digital core analysis technology has rapidly developed, proving invaluable not just in oil and gas reservoirs development, but also in geothermal energy, carbon and hydrogen storage. The China InterPore Chapter and the Research Center of Multiphase Flow in Porous Media at China University of Petroleum (East China) have established a conference platform for global scholars to exchange ideas and research in porous media utilizing digital core analysis technology. The 6^th International Conference on Digital Core Analysis & the 2023 China Interpore Conference on Porous Media was successfully held in Qingdao from July 5 to 7, 2023. The conference facilitated discussions among 150 participants, including over 20 invited experts from academia and industry, and the recent advances in research of fluid flow in porous media using digital core analysis technology were thoroughly presented.

As common physical phenomena in porous media,capillarity behaviors exist in many engineering applications and natural science fields. The experimental,theoretical and numerical research on capillarity in porous media has lasted for more than a century,and the research results have been widely used in various fields,such as the development of conventional and unconventional resources. However,although the research has made great progress,the complex imbibition mechanism poses new challenges to us. The 1st National Conference on Imbibition Theory and Application in Porous Media was held in Beijing from April 22 to 24,2023, to gather researchers who are interested in imbibition research,exchange the latest progress and achievements in the field of imbibition in porous media,and discuss research hotspots and difficulties.