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Three-dimensional simulation of geologic carbon dioxide sequestration using MRST
Get PDFPhysics-based computational modeling of subsurface CO2 migration constitutes the primary tool to assess geologic carbon storage. Such models are often required to plan injection operations and assess hazards such as CO2 migration into units above the storage formation. Here, we present three tools developed to increase fidelity of black-oil type geologic carbon storage models in the open-source MATLAB Reservoir Simulation Toolbox. These tools, which are published in the co2lab-mit module, include functionality to: (1) Calculate and output PVT properties of miscible brine and CO2 as a function of pressure, temperature, and salinity; (2) account for relative permeability hysteresis, necessary to model residual trapping; and (3) model CO2 transport due to concentration gradients (molecular diffusion). We validate our implementation with published results including experimental observations, present MRST examples, and conclude with some remarks on applicability, limitations, and potential extensions. Source code and examples are provided.Document Type: Original articleCited as: Saló-Salgado, L., Møyner, O., Lie, K. -A, Juanes, R. Three-dimensional simulation of geologic carbon dioxide sequestration using MRST. Advances in Geo-Energy Research, 2024, 14(1): 34-48. https://doi.org/10.46690/ager.2024.10.0
Pore network characterization and fluid occurrence of shale reservoirs: State-of-the-art and future perspectives
Get PDFDue to the increasing energy consumption and the promoting of the carbon neutral target, the exploitation of shale oil and gas, as well as carbon dioxide sequestration and hydrogen storage using shale as caprock, has received enormous attention. As a foundation for these hotspots, the characterization of pore structure in shale reservoirs has been widely studied. In this paper, the application of fluid intrusion and radiation methods in the characterization of pore structure in shale reservoirs was systematically reviewed, and the merits and limitations of both methods were highlighted. Taking the Fengcheng shale as an example, a detailed investigation of the fluid occurrence state was conducted, indicating that the fluid occurrence state significantly impacts the exploitation of hydrocarbon from shale reservoirs. Furthermore, there needs to be a systematic of investigation of how the pore structure characteristics and inorganic components of shale reservoirs control the integrity and safety of CO2 and H2 storage. Moreover, confinement effect of nanopores in shale should be paid attention to in future research on carbon and hydrogen storage.Document Type: PerspectiveCited as: Sun, M., Fu, J., Wang, Q., Gao, Z. Pore network characterization and fluid occurrence of shale reservoirs: State-of-the-art and future perspectives. Advances in Geo-Energy Research, 2024, 12(3): 161-167. https://doi.org/10.46690/ager.2024.06.0
Organic-inorganic interactions of clay minerals and organic matter: Action mechanism and analysis techniques
Get PDFElucidating the formation mechanism of organic-rich shale holds significant implications for hydrocarbon exploration, carbon sequestration, and carbon cycling. In recent years, the relationship between organic matter and clay minerals in shale has attracted widespread attention. This study aims to comprehensively overview the interactions between organic matter and clay minerals during deposition and diagenesis. Through sedimentation processes, climate and provenance control the composition of clay minerals in sediments jointly. Meanwhile, clay minerals exhibit selective adsorption of organic matter, thereby influencing the abundance and type of organic matter in sediments. In modern marine depositional environments, the interaction between clay minerals and organic matter significantly impacts the overall activity and burial efficiency of organic carbon. During the diagenesis stage, the presence of organic matter dramatically affects the transformation of smectite into illite. Conversely, the process of smectite illitization also exerts a significant influence on hydrocarbon generation. Furthermore, this study introduces state-of-the-art techniques to investigate the interactions between organic matter and clay minerals.Document Type: PerspectiveCited as: Xu, S., Zhao, T., Cui, X., Cai, J. Organic-inorganic interactions of clay minerals and organic matter: Action mechanism and analysis techniques. Advances in Geo-Energy Research, 2024, 14(3): 161-164. https://doi.org/10.46690/ager.2024.12.0
Correlations of residual oil distribution with pore structure during the water flooding process in sandstone reservoirs
Get PDFThe displacement of residual oil by water flooding in porous media is an important mechanism of enhanced oil recovery in many sandstone reservoirs. Nonetheless, our basic understanding of the influence of complex pore geometries of natural porous media on fluid distribution is still incomplete. Herein, two-phase flow simulations were performed to investigate the pore-scale dynamics of imbibition in a heterogeneous sandstone rock sample. Furthermore, the relationship between residual oil distribution and pore structure parameters was quantitatively characterized based on a pore-throat segmentation method. The findings suggest that the pore-scale displacement and snap-off processes have a strong dependence on the coordination number and aspect ratio. The entrapment and remobilization of oil clusters were also analyzed under continuous and discontinuous displacement modes. In addition, a new quantitative method to evaluate the displacement potential and mobilization pattern of remaining oil was presented and discussed. Statistical analysis revealed that the development of sub-pathways and the suppression of snap-off are responsible for the decrease in residual oil saturation with increasing capillary number during water injection. Moreover, the connected residual oil clusters trapped in pores with high coordination number prefer to be displaced and produced. Finally, the displacement modes with different capillary numbers under different initial oil distributions were evaluated to explain the effect of pore structure. By incorporating these correlations of displacement events with pore-throat geometry, existing predictive models can be improved, which could be helpful for the fine tapping of highly disconnected remaining oil in sandstone reservoirs.Document Type: Original articleCited as: Zhang, Q., Yang, Y., Wang, D., Sun, H., Zhong, J., Yao, J., Lisitsa, V. Correlations of residual oil distribution with pore structure during the water flooding process in sandstone reservoirs. Advances in Geo-Energy Research, 2024, 12(2): 113-126. https://doi.org/10.46690/ager.2024.05.0
Low-to-medium maturity lacustrine shale oil resource and in-situ conversion process technology: Recent advances and challenges
Get PDF Low-to-medium maturity lacustrine shale oil resources have enormous potential and are projected to play a crucial role in the massive scale-up of crude oil production in China in the near future. The in-situ conversion process is currently the only effective means of utilizing this resource. Nevertheless, significant scientific challenges and technological bottlenecks still exist. Under this circumstance, the National Natural Science Foundation of China approved an integrated project of the Enterprise Innovation and Development Joint Fund titled “The Mechanism of Low-to-medium Maturity Lacustrine Shale Oil Resource Formation and its in-situ Conversion and Exploitation”. This project aims to systematically investigate the entire process of in-situ conversion for low-to-medium maturity shale oil resources and lay a solid scientific and technological foundation for advancing the smooth implementation of on-site pilot trials. This paper presents the latest progress in this field and summarizes the existing scientific and technological challenges that need to be addressed. With the foundational support of the above project, our research team has made significant progress in several fields, including the formation mechanisms of organic matter superrich shale, low-to-medium maturity shale oil enrichment area evaluation, heat and mass transfer dynamics, coupled fluid field and hydrocarbon expulsion efficiency, exploitation methods, among others. Despite these theoretical advances, several major challenges were identified, which help to further focus on the critical scientific issues, determine the in-situ conversion technique-developing direction, and formulate a feasible implementation plan for future resource utilization.Document Type: PerspectiveCited as: Zhao, W., Guan, M., Liu, W., Bian, C., Li, Y., Wang, X., Xu, R. Low-to-medium maturity lacustrine shale oil resource and in-situ conversion process technology: Recent advances and challenges. Advances in Geo-Energy Research, 2024, 12(2): 81-88. https://doi.org/10.46690/ager.2024.05.0
Understanding the post-frac soaking process in multi-fractured shale gas-oil wells
Get PDFMulti-stage hydraulic-fracturing horizontal wells has revolutionized today’s oil and gas industry. Post-frac fluid soaking is essential for improving productivity of shale oil-gas wells. Optimization of soaking time is an open problem to solve in the petroleum industry. Understanding the post-frac soaking process is vitally important for solving the puzzle. Analytical solutions were developed in this study to describe the spontaneous imbibition processes in shale matrix and shale cracks during fluid soaking. Solutions show that the imbibition distance is directly proportional to the square root of imbibition time and the imbibition velocity is inversely proportional to the square root of imbibition time. The rate of spontaneous imbibition in shale cracks is much faster than that in shale matrix. Therefore, the optimum time for post-frac fluid soaking was further analyzed on the basis of the imbibition in shale cracks only. The solution was combined with pressure fall-off data to formulate a mathematical method for predicting the post-frac fluid soaking time required for the fluid to reach the mid-point between two adjacent hydraulic fractures. A case study with Tuscaloosa Marine Shale data suggests that the front of fluid imbibition should propagate 4 meters in 2 weeks and to 6 meters in 4 weeks. These numbers may be considered as the optimum times of post-frac fluid imbibition if the shale swell effect is negligible. Future research should quantify the effects of shale swelling on spontaneous imbibition so that the information can be incorporated in the soaking model to fully describe the imbibition process for better prediction of well productivity.Document Type: Original articleCited as: Guo, B., Wortman, P. Understanding the post-frac soaking process in multi-fractured shale gas-oil wells. Capillarity, 2024, 12(1): 6-16. https://doi.org/10.46690/capi.2024.07.0
Impeding effect on droplet spreading by a groove on the substrate
Get PDFUnderstanding the wetting behaviors of droplets on grooved surfaces is indispensable in surface science and offers promising avenues for advancing industrial processes. The droplet spreading on grooved surfaces can be discretized into a series of individual events that the droplet across each groove with variations in capillary forces and a subsequent re-equilibrium. In this work, a simplified model of droplet spreading on surface with an individual groove on both the left and right sides was utilized in order to elucidate the fundamental mechanisms underlying contact line pinning due to the groove. We examined the effects of the groove position and the wettability of solid surfaces. The contact line is observed to be pinned when the grooves are strategically positioned. However, by reducing the distance between the grooves, the contact lines can cross them. In such instances, the spreading process can be classified into four modes: Free spreading, impeding spreading, pinning, and depinning. The pinning and depinning phenomenon are explained by the balance between the driving force and pinning force on the contact line. Based on simulation results, the maximum pinning force exerted on the contact line by a certain solid surface can be theoretically predicted. Besides, the wettability of the solid surface also contributes to the impeding effect. This work provides theoretical guidance for the study of wetting on grooved surfaces at the nanoscale, which is essential for developing a comprehensive understanding of the interactions between droplets and structured surfaces, with potential applications in optimizing industrial processes and advancing surface science.Document Type: Original articleCited as: Huang, X., Li, Y. Q., Fan, J. C., Wu, H. A., Wang, F. C. Impeding effect on droplet spreading by a groove on the substrate. Capillarity, 2024, 13(1): 1-9. https://doi.org/10.46690/capi.2024.10.0
Effects of gravity and buoyancy on spontaneous liquid-liquid imbibition in fractured porous media
Get PDFSpontaneous imbibition in porous materials has received significant attention in recent decades; however, spontaneous liquid-liquid imbibition in fractures has not been well studied. Specifically, the mechanism behind the influence of gravity and buoyancy on the spontaneous imbibition of wetting phase fluid into fractured porous media remains uncertain. In this study, an analytical solution for spontaneous imbibition in fractured porous media under the influence of gravity and buoyancy is presented. The results show that imbibition velocity with buoyancy and gravity is faster than that without these forces. The effect of buoyancy and gravity on imbibition velocity increases with rising fracture aperture and length. When the fracture aperture is less than 1 μm, the relative deviation between imbibition height with and without gravity and buoyancy is about 50%. On the other hand, when the fracture aperture is greater than 1 μm, the relative deviation is proportional to the fracture aperture. The relative reduction in imbibition height over time is not obvious when the fracture aperture is the same. In the process of water-oil spontaneous imbibition, the effect of buoyancy and gravity is more pronounced at low oil-water interfacial tension. Therefore, the effect of buoyancy and gravity on spontaneous imbibition cannot be ignored under this condition.Document Type: Original articleCited as: Cheng, H., Wang, F. Effects of gravity and buoyancy on spontaneous liquid-liquid imbibition in fractured porous media. Capillarity, 2024, 10(1): 1-11. https://doi.org/10.46690/capi.2024.01.0
Gas transport mechanisms, mathematical models, and impact factors in low-permeability rocks: A critical review
Get PDFThe study of gas transport in low-permeability rocks is both practical and of significant importance to produce tight rock reservoirs. The presence of nanopores in tight rocks results in distinctly different gas transport mechanisms from those found in conventional reservoirs. Traditional Darcy’s law is inadequate for describing gas flow in this context. Instead, various modes of gas transport, such as continuum flow, slip flow, transition flow, and Knudsen diffusion for bulk gas, as well as surface diffusion and adsorption/desorption for adsorbed gas, coexist within these nanopores. This paper mainly focuses on studies of gas transport in nanopores that consider apparent permeability. To begin with, the pore structure characteristics and gas seepage mechanisms in shale are introduced. An overview of the three main methods for measuring apparent permeability including laboratory experiments, numerical simulations, and analytical techniques, is provided. Mathematical models describing gas transport within nanopores are emphasized as a foundational component of apparent permeability measurements. Furthermore, the factors that influence these models are discussed. Upon analyzing the existing models, it is evident that they are diverse and numerous. While these models typically encompass multiple mechanisms and influencing factors related to gas transportation, each model has its specific limitations. Therefore, there is a continued need for the development of more comprehensive and general models. This study offers the most detailed overview of gas transport mechanisms and mathematical models in low-permeability rocks, aiming to support the evaluation and exploitation of tight rock reservoirs.Document Type: Invited reviewCited as: Wang, M., Gao, M., Zhang, C., Thanh, H. V., Zhang, Z., Wang, D., Dai, Z. Gas transport mechanisms, mathematical models, and impact factors in low-permeability rocks: A critical review. Advances in Geo-Energy Research, 2024, 14(2): 119-134. https://doi.org/10.46690/ager.2024.11.0
Delving into the science of capillary effect for laser polishing
Get PDFLaser polishing techniques offer promising solutions for enhancing surface quality in precision surface finishing. By harnessing laser beams, this method provides efficient and controllable surface treatment, which is crucial for achieving desired surface smoothness and optical performance. Central to this process is the capillary effect driven by surface tension, which facilitates fluid flow on solid surfaces. Despite advancements, challenges persist in predicting and controlling capillary flow due to its complex nature. This paper explores the role of the capillary effect in laser polishing, outlining fundamental principles, discussing influencing factors, and proposing strategies for optimizing polishing outcomes. Understanding and manipulating the capillary effect holds the key to unlocking the full potential of laser polishing, offering avenues for improving surface finishes and material properties across various applications.Document Type: PerspectiveCited as: Huang, W., Yang, S., Xu, J., Xiao, J. Delving into the science of capillary effect for laser polishing. Capillarity, 2024, 13(2): 47-52. https://doi.org/10.46690/capi.2024.11.0