Article
Energy & Fuels
Xiaoyu Hou, James J. Sheng
Summary: Experimental and simulation studies have shown mixed results on the effects of shut-in and interfacial tension (IFT) reduction in removing water blockage after hydraulic fracturing. This work studied the impact of shut-in and IFT reduction on water blockage and found that shut-in can decrease permeability due to water refill, while reducing IFT is beneficial for regained permeability ratio. However, emulsification should be avoided. The study also found that the residual water saturation is larger in micropores and mesopores, indicating that core damage mainly comes from these smaller pores.
Article
Chemistry, Multidisciplinary
Xueping Zhang, Youquan Liu, Yuzhou Liu, Chuanrong Zhong
Summary: This study quantitatively investigates the imbibition characteristics of fracturing fluids in tight sandstone reservoirs through high-precision fluid spontaneous imbibition experiments. The results show that the tight sandstone samples have strong imbibition capacity and fast imbibition rate, with surface tension being the main controlling factor. This research is important for understanding the absorption mechanism of fracturing fluids in tight sandstone reservoirs and predicting flowback rates.
Article
Energy & Fuels
Zhonghua Liu, Baojun Bai, Jing Tang, Zuping Xiang, Shunpeng Zeng, Hai Qu
Summary: The study focused on the importance of gas shale permeability reduction in shaping gas production from shale gas reservoirs. Through experiments, it was found that microfractures significantly impact the flow of slickwater in the core, with the cumulative gas volume increasing linearly over time. The research also highlighted the effects of injection pressure gradients, injection volumes, and slickwater compositions on permeability reduction and flowback efficiency.
Article
Energy & Fuels
Zhonghua Liu, Baojun Bai, Yanling Wang, Hai Qu, Qianhua Xiao, Shunpeng Zeng
Summary: The study found that during the spontaneous imbibition process of slickwater in shale gas fields, the imbibition capacities of its components differ, and the imbibition mainly occurs through secondary microfractures.
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
(2021)
Article
Mathematics, Interdisciplinary Applications
Shanshan Yang, Mengying Wang, Mingqing Zou, Qiong Sheng, Ruike Cui, Shuaiyin Chen
Summary: In order to study the gas transmission characteristics in organic pores of rough shale reservoirs, models for effective fracture width, real gas transport, and apparent permeability coupling were established. The validity of the proposed models was verified by simulation data, and the contribution of each migration mechanism to the total flow was analyzed. The study found that the formation pressure is proportional to the influence of roughness on permeability, and the influence of roughness on diffusion ratios and slippage flow proportion depends on initial crack width and pore pressure.
CHAOS SOLITONS & FRACTALS
(2023)
Article
Energy & Fuels
Dunqing Liu, Hongkui Ge, Yinghao Shen, Hongxian Liu, Yanjun Zhang
Summary: The study shows that highly developed bedding fractures in Fuling play a key role in the formation of ultra-low WRR but high gas yield phenomenon. These fractures have larger apertures, leading to increased imbibition rate and retention of gas flow channels.
JOURNAL OF NATURAL GAS SCIENCE AND ENGINEERING
(2021)
Article
Geochemistry & Geophysics
Zhiyu Liu, Fan Fan, Donghang Zhang, Yang Li, Yuan Li, Kai Yang, Hongkui Ge, Fujian Zhou
Summary: The study focused on the drag reduction performance of slick-water in fractures, finding that the main factors affecting drag reduction are relative molecular weight and added concentration, with a negative drag reduction effect appearing when the concentration exceeds 0.10%.
Review
Engineering, Chemical
Liu Yang, Duo Yang, Chen Liang, Yuxue Li, Manchao He, Junfei Jia, Jianying He
Summary: This paper aims to provide a scientometric review of imbibition studies in unconventional reservoirs from 2010 to 2021. A total of 1810 papers are collected from the Web of Science Core Correction database based on selected keywords and paper types. Using CiteSpace software, a quantitative scientific analysis is carried out on various aspects of research. The study constructs a comprehensive research knowledge map of imbibition, providing relevant research with a more valuable and in-depth understanding of the field.
Review
Geosciences, Multidisciplinary
Manab Mukherjee, Vikram Vishal
Summary: This paper reviews and analyzes the research on shale permeability at the laboratory scale, including methods and data. It is found that there is a need to further study the methods for reporting relative permeability and design innovative laboratory techniques to address this issue.
EARTH-SCIENCE REVIEWS
(2023)
Article
Geochemistry & Geophysics
Tianlu Xu, Yingxian Lei, Chengmei Wu, Yinghao Shen
Summary: Large amounts of fracturing fluid are injected into unconventional reservoirs during hydraulic fracturing to increase formation energy and improve production and recovery efficiency. Improving fracture complexity and implementing well shutting before production can enhance pressure balance, increase formation energy, and promote imbibition and oil displacement. By using enhanced imbibition displacement additives, the displacement efficiency and amount of crude oil in micro-nanopores can be greatly improved, leading to increased fluid utilization efficiency. This research has significant implications for the efficient development and practical production of unconventional reservoirs.
Review
Energy & Fuels
Lijun You, Nan Zhang, Yili Kang, Jieming Xu, Qiuyang Cheng, Yang Zhou
Summary: Studies have found that reducing the flowback rate of hydraulic fracturing fluid in shale gas reservoirs may lead to higher gas production, leading to the concept of zero flowback rate (ZFR). By extending shut-in time or adjusting fluid properties, ZFR can be achieved, improving gas permeability and reducing costs.
Article
Energy & Fuels
Lei Hou, Derek Elsworth
Summary: The study investigates the permeability characteristics of CO2 in shale fractures, including the pressure evolution curve and its impact on adsorbed and non-adsorbed gases. The results show that the permeability evolution of CO2 in shale is controlled by the increasing adsorbed-phase density and swelling stress, with contributions from inorganic adsorbents playing a role in permeability evolution.
Article
Geochemistry & Geophysics
Hao Chen, Jianfei Wei, Hanlie Cheng, Qiang Qin, Ying Chen, Linqiang Zhang
Summary: Formation pressure decreases during fracturing fluid flowback and gas production. The stress sensitivity of fractures affects their permeability and gas well productivity. This study investigates the stress sensitivity of proppant-containing fractures with different roughness and its impact on well productivity. Experimental samples with varying proppant concentrations and fracture surfaces are used to quantify stress sensitivity. The results show that proppant concentration and fracture surface roughness significantly influence fracture permeability and stress sensitivity, impacting well productivity.
Article
Engineering, Chemical
Zhou Hu, Pengfei Chen, Wei Jiang, Yadong Yang, Yizhen Li, Longqing Zou, Huaming Wang, Yuping Sun, Yu Peng
Summary: Horizontal wells with multi-section and multi-cluster hydraulic fracturing are crucial for efficient development of shale gas. This study aims to investigate the influence of perforating holes and natural fractures on the initiation and propagation of hydraulic fractures. Experimental results revealed that the triaxial principal stress of the sample was deflected by natural fractures, resulting in significant tortuosity propagation of hydraulic fractures near the wellbore. Moreover, the degree of stress deflection and the probability of near-wellbore tortuosity propagation decreased with increasing natural fracture dip angle. In reservoirs with natural fractures, proppant should be added after the fractures are fully expanded to prevent sand plugging in tortuous fractures.
Article
Energy & Fuels
Mahmoud Khadijeh, Alissar Yehya, Elsa Maalouf
Summary: This study analyzes the efficiency of hydraulic fracturing operations using numerical models and experimental studies. It finds that in vertically transversely isotropic (VTI) formations, the expansion of cracks is influenced by the degree of anisotropy. Additionally, cracks grow independently when the distance between cracks exceeds 12 m, and a planar propagation is observed for a distance above 20 m. The results also indicate that close cluster spacing leads to larger fractured area and resulting permeability. This work helps identify the optimal fracturing scenario for enhancing permeability in anisotropic unconventional reservoirs under different hydro-mechanical conditions.
GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES
(2022)
Article
Energy & Fuels
Bin Shi, Yunxing Cao, Lin Tian, Junsheng Zhang, Shimin Liu
Summary: This study conducted a CO2 gas fracturing (CO2-Frac) experiment in an area with steeply inclined multicoal seam formations. The results showed that using CO2 fracturing in in-seam boreholes and penetration boreholes significantly improved the efficiency of gas drainage. The fractures radius of CO2-Frac in the penetrating borehole was larger than in the in-seam boreholes, which may be related to the developing property of bedding and cleat system in coal seam.
Article
Energy & Fuels
Peng Liu, Ang Liu, Shimin Liu, Lingling Qi
Summary: Effective reservoir stimulation is crucial for enhancing coalbed methane (CBM) recovery, and ultrasound treatment offers a new alternative to traditional hydraulic fracturing. This study investigated the alteration of pore/fracture structure in coal with ultrasound treatment and its impact on gas desorption and diffusion behaviors. Results show that ultrasound treatment significantly increases pore volume and interconnectivity in coal, leading to improved gas transport during gas drainage and CBM production.
Article
Thermodynamics
Ang Liu, Shimin Liu
Summary: CO2 sequestration in geological coal formations has the potential to store a large amount of CO2. However, the mechanisms underlying the CO2-coal interactions and their effects on the mechanical properties of coal at the micro-to-nano scale are still not well understood. In this study, we used grid-based nanoindentation tests and FESEM-EDS analyses to investigate the mechanical property variations and distributions of coals due to mineral and structural changes. We also quantified the mechanical property alterations induced by different treatments involving gaseous CO2, ScCO2, and ScCO2-water mixtures. The results revealed that the heterogeneity of coals at the micro-to-nano scale and their corresponding mechanical properties are dependent on composition and microstructure. Additionally, the mechanical properties of coals can be altered by the interactions between organic carbon and CO2, as well as the hydration effects of water in wetted coals or the dissolution and precipitation of minerals in fluid environments.
Article
Energy & Fuels
Yunxing Cao, Junsheng Zhang, Xinsheng Zhang, Shimin Liu, Derek Elsworth
Summary: The study finds that high-pressure CO2 impact tests result in open and zigzag fractures on coal. This suggests that the fracturing mechanism of CO2 gas on coal can be described as four consecutive steps.
Article
Energy & Fuels
Shaoqing Wang, Hao Chen, Xiaoling Wang, Yuegang Tang, Shimin Liu, Harold H. Schobert, Xiaoxia Song, Fangui Zeng
Summary: The evolution of coals affected by igneous intrusions differs from normal coalification, and is related to geological conditions. By analyzing data, three evolution pathways were identified, with Track I being similar to normal coalification, Track II showing faster dehydrogenation and slower deoxygenation, and Track III displaying anomalously high oxygen content due to the presence of carbonate minerals.
Article
Engineering, Geological
Jiandong Ren, Yixin Zhao, Wen Wang, Jihong Guo, Zhongbo Sun, Shimin Liu
Summary: Currently, the width of the protection coal pillar with the buried pipeline at gas-coal integrated mining area is determined by the horizontal distance between the surface subsidence boundary and the panel (traditional method). However, this method leads to the loss of abundant coal resources. Therefore, an optimal design for the protective coal pillar of the pipeline is proposed by investigating the Gaussian function equation of the surface subsidence curve and analysing the failure probability of the pipeline.
ROCK MECHANICS AND ROCK ENGINEERING
(2023)
Article
Construction & Building Technology
Nathan Gendrue, Shimin Liu, Sekhar Bhattacharyya, Ronald Clister
Summary: In this study, the airflow distribution of a large opening mine with a booster fan was investigated using a CFD model. The results showed that the booster fan is an effective ventilation control for airflow direction and placement significantly influences the pollutants' removal. Additionally, the traditional traverse method may be inadequate for measuring airflow around booster fans, with errors ranging from 35% to 210%. The study provides a foundation for future research on booster fan placement optimization and face ventilation effectiveness.
TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY
(2023)
Editorial Material
Geosciences, Multidisciplinary
Jingshou Liu, Wenlong Ding, Shimin Liu, Kouqi Liu, Dadong Liu
FRONTIERS IN EARTH SCIENCE
(2023)
Article
Energy & Fuels
Ang Liu, Shimin Liu
Summary: This study measured and analyzed the sorption and diffusion behaviors of eight coals from major coalfields in the United States. The results showed that all eight coals have considerable hydrogen sorption capacities. The fixed carbon content and O/C ratio are correlated with the maximum hydrogen adsorption capacity in coals. Hydrogen has superior diffusive gas deliverability in coal, making it a promising candidate for hydrogen storage.
Article
Energy & Fuels
Ang Liu, Shimin Liu
Summary: In this study, the gas-water production period in a shale gas reservoir is divided into two stages: gas-water two-phase flow dominates at Stage I, while flows are controlled by desorbed gas and water in the adsorbed phase at Stage II. The evolution models of porosity and permeability consider the swelling strains induced by gas and water sorption. A coupled model of multi-mechanistic gas-water transport behavior in tight shale was proposed and numerically solved. The results provide insights into gas/water transport behavior and water retention behavior in tight shale.
Article
Energy & Fuels
Shuaifang Guo, Yunxing Cao, Junsheng Zhang, Xinsheng Zhang, Bingbing Meng, Shimin Liu
Summary: High-pressure CO2 gas fracturing is a novel technology to improve coal-seam permeability and increase gas extraction efficiency. However, the understanding of the pore-microfracture evolution characteristics and damage mechanism induced by CO2-Frac is still limited.
Article
Engineering, Geological
Ang Liu, Shimin Liu, Kaiwen Xia, Peng Liu, Yun Yang, Gang Wang
Summary: Matrix shrinkage/swelling induced by gas sorption plays a crucial role in coalbed methane reservoir stress depletion and gas transport enhancement. This study used a sorption and matrix shrinkage system to measure the gas sorption capacity and 3-D anisotropic swelling/shrinkage strains simultaneously. The high heterogeneity and anisotropy of coals were confirmed using imaging techniques, and the principal strains were computed through a proposed strain transformation model.
ROCK MECHANICS AND ROCK ENGINEERING
(2023)
Article
Energy & Fuels
Jinming Zhang, Xiaowei Hou, Shimin Liu, Luwang Chen, Yingjin Wang
Summary: In this study, a new data-driven method, an improved BP neural network model optimized by grey relational analysis (GRA) and particle swarm optimization (PSO) algorithm, was proposed for predicting the accurate evolution of in situ coalbed methane (CBM) content. The results showed that the GRA method helped determine the input parameters for the BP neural network model, improving the operation speed and reducing the influence of redundant parameters. Additionally, the PSO algorithm with asynchronous learning factors successfully optimized the weights and thresholds of the BP neural network, leading to increased modeling accuracy. The proposed model yielded reliable results, outperforming traditional prediction models in terms of prediction accuracy (only 3.71% relative error). It is believed that this model is useful for high accuracy prediction of in situ CBM content in heterogeneous reservoirs under complicated geological structure conditions due to its robustness and generalization.
Article
Energy & Fuels
Chuanwen Sun, Shimin Liu, Shouding Li, Kai Wang, Yiming Sun, Xiao Li, Zhaobin Zhang
Summary: Nano-SiO2 particles can accelerate the formation of tetrahydrofuran hydrate and shorten the induction time, with an optimal mass concentration of 0.5 mg/mL.
Article
Energy & Fuels
Elham Rahimi, Shimin Liu, Meng Wang
Summary: Co-bioconversion of coal and anaerobic digestion sludge is an innovative approach to managing waste materials and producing valuable products such as biogas and biofertilizers. This study investigates the effects of different media combinations on the bioconversion process and finds that the use of formation water and nutrients leads to maximum biogas production in a short period, while mixing coal-sludge with deionized water results in maximum cumulative biogas production over a longer duration.
