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Fluid flow and efficient development technologies in unconventional reservoirs: State-of-the-art methods and future perspectives
Get PDFWith the global energy consumption on the rise and the gradual decline in conventional oil production, unconventional reservoirs have received considerable attention in the last decade. However, due to the unique physical properties and a large number of micro/nanopores in unconventional reservoirs, fluid flow in these reservoirs is considerably different from conventional ones. Therefore, it is highly important to conduct research on elucidating these fluid flow mechanisms. Furthermore, to avoid problems associated with the rapid production decline and low recovery efficiency in such reservoirs, an enhanced oil recovery technology that can efficiently and economically develop unconventional reservoirs is urgently required. This paper systematically summarizes the current research on flow mechanisms, including capillary imbibition, molecular-scale fluid flow and productivity prediction in unconventional reservoirs, and introduces the enhanced oil recovery and application status of hydraulic fracturing assisted oil displacement technology, along with a brief analysis of their advantages and disadvantages. This study is intended to serve a reference for the efficient development of unconventional reservoirs.Document Type: PerspectiveCited as: Wang, F., Xu, H., Wang, S., Deng, J., Wang, Y. Fluid flow and efficient development technologies in unconventional reservoirs: State-of-the-art methods and future perspectives. Advances in Geo-Energy Research, 2024, 12(3): 237-240. https://doi.org/10.46690/ager.2024.06.0
Stability analysis of surrounding rock of multi-cavern for compressed air energy storage
Get PDFCompressed air energy storage in artificial caverns can mitigate the dependence on salt cavern and waste mines, as well as realize the rapid consumption of new energy and the “peak-cutting and valley-filling” of the power grid. At the same time, the safety and stability of the surrounding rock of gas storage has attracted extensive attention. Based on finite element simulation, a numerical model of shallow-buried double-chamber for compressed air energy storage is established, and the influence of working pressure, cavern type, pillar space, and cavern diameter on the mechanical behavior of surrounding rock is analyzed. It is discovered that the cavern type significantly affects the response of the surrounding rock, whose deformation and plastic strain in the horseshoe-shaped cavern is significantly larger than that in the circular cavern. For circular caverns, the pillar space of 2∼3 times the cavern diameter is only suitable for low working pressure, and the plastic strain and deformation of surrounding rock increases sharply with the increase of working pressure. It is more appropriate to select the pillar space that is 4 times the cavern diameter when the working pressure is greater than 16 MPa. With the increase in the cavern diameter, the maximum deformation of the surrounding rock accelerates rapidly.Document Type: Short communicationCited as: Ji, W., Wang, S., Wan, J., Cheng, S., He, J., Shi, S. Stability analysis of surrounding rock of multi-cavern for compressed air energy storage. Advances in Geo-Energy Research, 2024, 13(3): 169-175. https://doi.org/10.46690/ager.2024.09.0
AGER launches one-journal-one-forum mode to achieve a leading geo-energy exchange platform
Get PDFFrom 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.Document Type: EditorialCited as: Cai, J. AGER launches one-journal-one-forum mode to achieve a leading geo-energy exchange platform. Advances in Geo-Energy Research, 2024, 13(2): 81-82. https://doi.org/10.46690/ager.2024.08.0
Hydrogen influence on transformation of terrigenous reservoir physical and mechanical properties
Get PDFThe article aims to describe a methodology for studying the dynamic, stress-strain properties and density of core samples before and after exposure to hydrogen. The Stages of sample studies and the instruments used in laboratory experiments are examined on the example of core samples taken from the Bobrikov formations in the Volga-Ural oil and-gas bearing region. A comparative analysis of dynamic properties, density, Young’s modulus and Poisson’s ratio was carried out before and after ex-posure to hydrogen. It was discovered that after exposure to this gas, interval transit time of acoustic P-wave and S-wave through the samples decreased by an average of 2.4%; Young’s modulus increased by 6.5%, while Poisson’s ratio remained virtually unchanged. Besides, the research results demonstrat-ed an increase in sample density by 1.1%. The analysis of correlation dependencies revealed a typical change in interrelation of the parameters of P-wave interval transit time with Young’s modulus and S-wave interval transit time after samples exposure to hydrogen. Overall, based upon the results of the studies of density, dynamic properties, and Young’s modulus, there is evidence of weakening of the stress strain properties in the core samples. However, such change does not have a major effect on their absolute values. Analysis of the results collected during laboratory experiments shows that the consid-ered horizon could potentially be the formation for the storage of a methane-hydrogen mixture.Document Type: Original articleCited as: Popov, S. N., Chernyshov, S. E., Wang, X., Hou, L. Hydrogen influence on transformation of terrigenous reservoir physical and mechanical properties. Advances in Geo-Energy Research, 2024, 13(3): 193-202. https://doi.org/10.46690/ager.2024.09.0
Reservoir stimulation for unconventional oil and gas resources: Recent advances and future perspectives
Get PDFThe first Geo-Energy Frontier Forum with the theme of “opportunities and challenges for geo-energy exploration and development” was successfully held in Wuhan, recently. The forum included 32 sessions, mainly focused on four directions: geo-energy development and reserve, petroleum geophysical exploration, oil and gas geology, and field development engineering. This paper summarizes the key findings in the 22nd session titled “Reservoir stimulation for unconventional oil and gas resources”. A total of 17 experts and scholars participated in the presentations, covering a wide range of topics in unconventional oil and gas resources development. This research collectively highlighted the significance of reservoir stimulation techniques in unconventional oil and gas resource development, including research progress in fracture network modeling techniques, fluid pressure, rock mechanics, fracture propagation, and proppant migration in hydraulic fracturing.Document Type: PerspectiveCited as: Liao, Q., Wang, B., Chen, X., Tan, P. Reservoir stimulation for unconventional oil and gas resources: Recent advances and future perspectives. Advances in Geo-Energy Research, 2024, 13(1): 7-9. https://doi.org/10.46690/ager.2024.07.0
Nanoscale mineralogy and organic structure characterization of shales: Insights via AFM-IR spectroscopy
Get PDFAtomic force microscopy coupled with infrared spectroscopy (AFM-IR) is one of the most effective and widely employed mixed techniques capable of providing direct access to infrared spectroscopic imaging and chemical analysis at the nanoscale spatial resolution. In this communication, AFM-IR was applied to the evaluate the in-situ nanoscale mineralogy and to characterize the organic structure of shale. Significant chemical and microstructural heterogeneity could be observed on the mirror-like surface of naturally deformed shale. It was also apparent that slickensides formed on the mirror-like surface potentially influence the spatial distribution of organic matter. This technique provides an effective combination for direct and in-situ studies of the morphology and physicochemical properties of geological rocks at the nanoscale, opening a new avenue for investigations to help reveal some complex geological phenomena, such as organic carbon graphitization and mineral transformation during fault deformation. Furthermore, this technique makes it possible to determine the chemical composition, molecular structure and functional group information of shale organic matter, which is crucial information for investigating the hydrocarbon generation potential, maturity evaluation, and oil and gas migration mechanisms in shale.Document Type: Short communicationCited as: Zhu, H., Lu, Y., Pan, Y., Qiao, P., Raza, A., Liu, W. Nanoscale mineralogy and organic structure characterization of shales: Insights via AFM-IR spectroscopy. Advances in Geo-Energy Research, 2024, 13(3): 231-236. https://doi.org/10.46690/ager.2024.09.0
Development and validation of a remotely triggered pressure- and gas-preserved coring tool for deep coal mines in drilling fluid environments
Get PDFThe accurate measurement of coal seam gas content is essential for several aspects of deep coal mining, including disaster management, resource allocation and sustainability. However, obtaining in-situ coal samples while preserving gas content under challenging conditions, such as high stress, temperature fluctuations, and drilling fluid environments, remains a significant challenge. To overcome this difficulty, we present an innovative in situ pressure- and gas-preserved coring tool specifically designed for deep coal mining applications. This device enables the collection of coal seam samples under in-situ conditions while ensuring that both pressure and gas content are preserved, thereby preventing gas escape during sample transfer and providing more accurate parameters for evaluating coal and natural gas reserves. In the demanding environment of deep coal seams, the performance of the pressure-preserved chamber of the corer relies on the reliability of its remote triggering mechanism. The presence of drilling fluid introduces medium resistance, which can impair the triggering process–an issue largely overlooked in previous research. Herein, we propose a robust method to calculate remote triggering forces within liquid media and optimize its key parameters to improve operational stability. Laboratory tests and field validations in coal mining environments are conducted, which confirm the effectiveness of the optimized design and demonstrate the tool’s practical applicability. This study offers valuable insights into addressing key challenges in deep coal reservoir exploration and gas resource preservation.Document Type: Original articleCited as: Li, J., Li, J., Wang, T., Shi, X., Cui, P., Shang, D. Development and validation of a remotely triggered pressure- and gas-preserved coring tool for deep coal mines in drilling fluid environments. Advances in Geo-Energy Research, 2024, 14(2): 147-160. https://doi.org/10.46690/ager.2024.11.0
Modeling capillary pressure in dual-scale fibrous structures for resin transfer molding processing of composites: A brief review and perspective
Get PDFResin transfer molding has garnered significant attention for the development of high performance and complex structural composites. Capillary forces, driven by surface tension and fibre wettability, play a crucial role in the impregnation of fibres by resin flow. Capillary pressure is identified as a key factor in void formation and transport during the molding process. The influence of geometrical parameters on the capillary pressure is also examined. This review delves into the mechanism of capillary pressure, considering the effects of fibre arrangement and dual-scale pore structures during the resin transfer molding filling stage. The models incorporate fluid dynamics, surface tension and fibre wettability, and is validated by the wicking experiments. The recent works suggest that better control over capillary pressure during resin transfer molding processing can lead to improved filling uniformity, reduced void content, and enhanced mechanical properties of composite materials. The development of artificial intelligence assisted methods for capillary pressure assessment and control shows great potential for improving high-performance composite manufacturing.Document Type: Invited reviewCited as: Deng, Y., Chen, Y., Zhi, J., Yang, W., Li, Y. Modeling capillary pressure in dual-scale fibrous structures for resin transfer molding processing of composites: A brief review and perspective. Capillarity, 2024, 13(3): 60-67. https://doi.org/10.46690/capi.2024.12.0
The influence of methyl orange on the CO2-brine wettability of organic-acid-aged calcite samples: Implications for CO2 geo-storage
Get PDFThe underground storage of CO2 in a depleted carbonate formation is a suitable method for limiting its anthropogenic release and minimize global warming. The rock wettability is an essential factor controlling the mechanisms of CO2 trapping and its containment safety in the geo-storage formation. The geo-storage rock contains innate organic acids which alters the wettability of the rock surface from the hydrophilic condition to the hydrophobic state, thus reduce the CO2 storage capacity. In this study, methyl orange which is a toxic dye that is generally released into environment was used as wettability modifier to change the wettability of stearic acid aged calcite (oil wet) to water wet. This study uses the contact angle technique (sessile drop method) to examine the effects of various concentration of methyl orange (10-100 mg/L) on the wettability of the CO2/brine/stearic-acid aged calcite system under geo-storage conditions (i.e., temperatures of 25 and 50 ℃ and pressures of 5-20 MPa). The results indicate that the advancing and receding contact angles (θa and θr) of the organic-acid contaminated rock surface were drastically reduced upon exposure to methyl orange, attaining the minimum values of 62◦ and 58◦ respectively, in the presence of 100 mg/L methyl orange at 20 MPa and 50 ℃. Thus, the present results suggest that rather than discharging methyl orange into the environment, it could be injected into underground reservoirs in order to reduce the level of environmental pollution and at the same time increase the CO2 storage capacity of carbonate formations.Document Type: Original articleCited as: Alhammad, F., Ali, M., Yekeen, N., Ali, M., Kamali, M., Iglauer, S., Keshavarz, A. The influence of methyl orange on the CO2-brine wettability of organic-acid-aged calcite samples: Implications for CO2 geo-storage. Advances in Geo-Energy Research, 2024, 12(2): 102-112. https://doi.org/10.46690/ager.2024.05.0
Novel Transformer-based deep neural network for the prediction of post-refracturing production from oil wells
Get PDFThe accurate prediction of post-refracture production can be of great value in the selection of target wells for refracturing. Given that production from post-refracture wells yields time-series data, deep neural networks have been utilized for making these predictions. Conventional deep neural networks, including recurrent neural network and long shortterm memory neural network, often fail to effectively capture long-range dependencies, which is particularly evident in tasks such as forecasting oil well production over periods extending up to 36 years. To overcome this limitation, this paper presents a novel deep neural network based on Transformer architecture, meticulously designed by fine-tuning the key components of the architecture, including its dimensions, the number of encoder layers, attention heads, and iteration cycles. This Transformer-based model is deployed on a dataset from oil wells in the Junggar Basin that spans the period of 1983 to 2020. The results demonstrate that the Transformer significantly outperforms traditional models such as recurrent neural networks and long short-term memory, underscoring its enhanced ability to manage long-term dependencies within time-series data. Moreover, the predictive accuracy of Transformer was further validated with data from six newly refractured wells in the Junggar Basin, which underscored its effectiveness over both 90 and 180 days post-refracture. The effective application of the proposed Transformer-based time-series model affirms the feasibility of capturing long-term dependencies using Transformer-based encoders, which also allows for more accurate predictions compared to conventional deep learning techniques.Document Type: Original articleCited as: Jia, J., Li, D., Wang, L., Fan, Q. Novel Transformer-based deep neural network for the prediction of post-refracturing production from oil wells. Advances in Geo-Energy Research, 2024, 13(2): 119-131. https://doi.org/10.46690/ager.2024.08.0