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Phase Equilibria of Natural Gas Hydrates in Bulk Brine and Marine Sediments from the South China Sea

JOURNAL OF CHEMICAL AND ENGINEERING DATA 2021年第11期66卷 4064-4074页

作者： Geng, Lantao Cai, Jin Lu, Cheng qin, xuwen Qi, Rongrong Meng, Fanle Xie, Yan Sha, Zhibin Wang, Xiaohui Sun, Changyu China Geol Survey Guangzhou Marine Geol Survey Guangzhou 510760 Peoples R China China Geol Survey Gas Hydrate Engn Technol Ctr Guangzhou 510760 Peoples R China Southern Marine Sci & Engn Guangdong Lab Guangzho Guangzhou 511458 Peoples R China China Univ Petr State Key Lab Heavy Oil Proc Beijing 102249 Peoples R China China Geol Survey Ctr Oil & Nat Gas Resource Explorat Beijing 100083 Peoples R China China Univ Geosci Sch Energy Resources Beijing 100083 Peoples R China

Studies on gas hydrate phase equilibrium conditions are reported widely in the literature. However, the data available for natural gas hydrates (NGHs) in real marine conditions are limited. In this study, NGH dissociation conditions in bulk brine and marine sediments were measured by using a microdifferential scanning calorimetry (mu-DSC). The sediments used in the experiment were obtained from the Shenhu area of the South China Sea, and the natural gas, as well as part of the water samples, were prepared according to the field data. Additionally, the Chen-Guo model was improved to calculate the NGH equilibrium conditions in the systems containing electrolytes and porous sediments. The experimental results showed that the NGH is relatively more stable than pure CH4 hydrate. The hydrate phase equilibrium curves shift to the left with the increased salinity in bulk water and sediments. In addition, the hydrate decomposition temperatures in marine sediments are obviously lower than those in bulk water. The average deviations of the improved model are 2.32% and 3.7% for bulk brine and sediments, respectively, which indicates great predictability. We consider that besides pore size as the main factor affecting the hydrate phase equilibrium, the water absorption capacity of marine sediments can also affect their decomposition conditions. The hydrate decomposition enthalpies were calculated by the Clausius-Clapeyron equation, and the results showed that the enthalpies increased with the decreased salinity and the addition of marine sediments. These findings are significant to NGH production safety in real marine sediments.

关键词： Geological materials Organic reactions Solvates Phase equilibria Water

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Effects of Micellization Behavior on the Interfacial Adsorption in Binary Anionic/Nonionic Surfactant Systems: A Molecular Simulation Study

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LANGMUIR 2021年第40期37卷 11835-11843页

作者： Lian, Peng Jia, Han Yan, Hui Yuan, Jie Tang, Hongtao Li, Zhe Fan, Fangning qin, xuwen Lv, Kaihe Liu, Dexin China Univ Petr East China Sch Petr Engn Qingdao 266580 Peoples R China China Univ Petr East China Sch Petr Engn Shandong Key Lab Oilfield Chem Qingdao 266580 Peoples R China Liaocheng Univ Sch Pharmaceut Sci Liaocheng 252059 Shandong Peoples R China SINOPEC Shengli Oilfield Co Shengli Oil Prod Plant Dongying 257000 Peoples R China

A surfactant interfacial adsorption process is highly associated with its micellization behaviors in the water phase, which is of great fundamental and practical significance in enhanced oil recovery. In this paper, the typical anionic surfactant 1-dodecanesulfonic acid sodium (DAS) and nonionic surfactants octylphenol polyoxyethylene ether-n (OP-n, n = 1, 5, and 10) are introduced to investigate their micellization behavior and interfacial adsorption process via molecular dynamics simulation. Number density profiles reveal that the additional OP5 molecules in the water phase generate the mixed micelle with DAS molecules and greatly promote its interfacial adsorption. Interaction energy calculation is employed to confirm the interaction of anionic/nonionic surfactants in the mixed micelle. Then, the radial distribution function, solvent-accessible surface area, and solvation free energy are calculated to further explore and verify the adsorption mechanism of the mixed micelle. It is found that the nonionic surfactant obviously decreases the hydrophilicity of the mixed micelle in the water phase, which should be responsible for its intensive tendency of the interfacial adsorption.

关键词： Adsorption Molecules Micelles Surfactants Water

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Carbon Sequestration in Overlying Methane Hydrate Layers Via Hydrate Technology: Feasibility and Synergistic Benefits

SSRN

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SSRN 2024年

作者： Zhang, Zhaobin Li, Yuxuan Li, Shouding He, Jianming Xie, Zhuoran Li, Xiao Lu, Cheng qin, xuwen Key Laboratory of Shale Gas and Geoengineering Institute of Geology and Geophysics Chinese Academy of Sciences Beijing100029 China Innovation Academy for Earth Science Chinese Academy of Sciences Beijing100029 China College of Earth and Planetary Sciences University of Chinese Academy of Sciences Beijing100049 China Oil and Gas Resources Survey China Geological Survey Ministry of Natural Resources Beijing100083 China China Geological Survey Ministry of Natural Resources Beijing100037 China

Excessive carbon dioxide emissions pose a global environmental issue, and carbon sequestration technology offers a solution. This study proposes a novel approach for carbon dioxide sequestration in the overlying layers of methane hydrate reservoirs using carbon dioxide hydrate technology. The feasibility and risks of this method are evaluated over a time scale of 100,000 years. The research indicates that after injection into the overlying layers of methane hydrate reservoirs, carbon dioxide migrates upwards driven by buoyancy, gradually forming highly saturated carbon dioxide hydrate shells at the leading edge of migration. Within these carbon dioxide hydrate shells, a portion of the carbon dioxide is sequestered in liquid and dissolved forms;however, over tens of thousands of years, some carbon dioxide escapes via dissolution and diffusion. The study further discusses the synergistic effects between methane hydrate extraction and carbon sequestration in overlying layers, showing that the cold seawater downdraw effect induced by methane hydrate extraction significantly enhances the efficiency and safety of carbon dioxide hydrate sequestration in the overlying layers. Given the widespread distribution of methane hydrate reservoirs globally, this research provides new insights into carbon sequestration technology. © 2024, The Authors. All rights reserved.

关键词： Carbon dioxide

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Pore structure changes induced by hydrate dissociation: An example of the unconsolidated clayey-silty hydrate bearing sediment reservoir in the South China Sea

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MARINE GEOLOGY 2022年 443卷 106689-106689页

作者： Lei, Xin Yao, Yanbin qin, xuwen Lu, Cheng Luo, Wanjing Wen, Zhiang Yuan, Xuehao China Univ Geosci Sch Energy Resources Beijing 100083 Peoples R China Beijing Key Lab Unconvent Nat Gas Geol Evaluat & Beijing 100083 Peoples R China China Geol Survey Guangzhou Marine Geol Survey Guangzhou 510075 Peoples R China China Geol Survey Gas Hydrate Engn Technol Ctr Guangzhou 510075 Peoples R China Southern Marine Sci & Engn Guangdong Lab Guangzho Guangzhou 511458 Peoples R China China Geol Survey Ctr Oil & Nat Gas Resource Explorat Beijing 100083 Peoples R China

The natural gas hydrates (NGHs) in the South China Sea are found in unconsolidated clayey-silty sediments, featured by very weak mechanical strength and low permeability. During gas extraction from such unstable, low permeability reservoirs, hydrate dissociation can result in distinct changes in pore properties and flow capability. Thus, it is extremely important to investigate the pore characteristics and gas flow mechanisms in such reservoirs. In this study, five sediment samples including two from the hydrate bearing layer (HBL) and three from the underlying layer (ULL), were taken from an exploration well in the Shenhu area, South China Sea. The pore morphology, pore specific surface area (SSA), total pore volume, porosity, and pore size distribution of these samples have been analyzed to compare the reservoir physical properties of the HBL (after the hydrate has dissociated and disappeared) with the ULL. Results from scanning electron microscopy reveal that the HBL samples without the hydrate present feature larger grain sizes, larger pore apertures and better connectivity than ULL samples. Results of NMR analysis and low temperature N-2/CO2-adsorption show that both HBL and ULL samples have high total porosities (42.4%-48.8%) and high SSA (21.17-30.09 m(2)/g), while the results from centrifugal experiments demonstrate that the producible porosity (defined as the pore volume available for hydrocarbon emplacement) of the HBL samples is about twice (26.6%-30.3%) that of the ULL samples (15.5%-19.6%). The pores in the two sample types are dominated by intra-particle pores of 80 nm, and inter-particle and inter-aggregate pores of 0.2-3 mu m. The above differences between HBL and ULL can be used to analyze the pore structure changes occurring as a result of the dissociation of NGHs in the HBL. We assume that on the one hand, formation of NGHs reduces pore pressure, thus resulting in higher effective stress, then compacts the pore space and reduces the total porosity

关键词： Natural gas hydrates (NGHs) Pore types Pore size distribution Nuclear magnetic resonance (NMR) Centrifuge experiment Shenhu area

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Evolution of hydrate habit and formation properties evolution during hydrate phase transition in fractured-porous medium

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FUEL 2022年第PartA期324卷

作者： Bian, Hang qin, xuwen Luo, Wanjing Ma, Chao Zhu, Jian Lu, Cheng Zhou, Yingfang China Univ Geosci Sch Energy Resources Beijing 100083 Peoples R China Ctr Oil & Nat Gas Resource Explorat China Geol Survey Beijing 100083 Peoples R China Guangzhou Marine Geol Survey China Geol Survey Guangzhou 510075 Peoples R China Southern Marine Sci & Engn Guangdong Lab Guangzhou 511458 Peoples R China iRock Technol Beijing 100094 Peoples R China Univ Aberdeen Sch Engn Aberdeen Scotland Natl Engn Res Ctr Gas Hydrate Explorat & Dev Guangzhou 511458 Peoples R China

Natural gas hydrate, as an efficient and clean energy resource, are naturally distributed in porous and fractured porous medium. With the most recent development of advanced micro-scale imaging techniques, hydrate habits evolution, hydrate occurrences, and pore structure evolution as well as seepage characteristics during hydrate phase transition in porous hydrate-bearing sediments have been studied extensively at pore scale. However, there are few studies on gas hydrates in fractured-porous sediment. In this work, xenon hydrate phase transition experiment by excess-gas method is carried out in a fractured sandstone core with in-situ micro computed tomography (micro-CT) scanning to explore the evolution of hydrate habits and physical parameters of the host sediment. The results indicate that hydrate-bearing sediment is a dynamic equilibrium system as hydrate synthesis and decomposition occur simultaneously at each moment of hydrate phase transition induced by pressure change. The hydrate occurrences in fractured hydrate reservoirs include contiguous-sheet, clustered and isolated, which are slightly different from that of porous hydrate formation;and the contiguous-sheet hydrate is the occurrence that dominantly determines the seepage characteristics of fractured hydrate-bearing sediments. In addition, the logic diagram for hydrate growth paths in fractured-porous medium is presented for the first time. These findings are significant for detailed understanding of pore-scale hydrate distribution throughout phase transition process and provide theoretical basis for precise modeling of permeability in host sediments.

关键词： Hydrate Habit Hydrate Morphology Fractured-Porous Medium Micro-CT Seepage Capacity

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从有路导航走向无路导航

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自然资源遥感 2024年第4期36卷 1-8页

作者：张过秦绪文朱春阳王善绣徐青运晓宇武汉大学测绘遥感信息工程国家重点实验室武汉430079 中国自然资源航空物探遥感中心北京100083 中国卫星导航定位应用管理中心北京100088 战略支援部队信息工程大学地理空间信息学院郑州450001

在有路导航日臻成熟的背景下,该文结合车辆在复杂非结构化环境下对导航服务的需求,提出了无路导航这一多学科交叉研究方向。首先,介绍了有路导航的发展及无路导航的需求场景,基于车辆通过性的4个具体方面,提出了从有路导航走向无路导航... 详细信息

在有路导航日臻成熟的背景下,该文结合车辆在复杂非结构化环境下对导航服务的需求,提出了无路导航这一多学科交叉研究方向。首先,介绍了有路导航的发展及无路导航的需求场景,基于车辆通过性的4个具体方面,提出了从有路导航走向无路导航过程中的科学问题,包括地理-地质通行要素精细化遥感探测、无路区域软地面土壤参数遥感获取、天候变化对地面特性的定量影响机理,阐明了无路导航的研究导向;然后,归纳了车辆通过性计算与表征技术、无路区域数字路网构建技术、无路导航智能路径规划技术等关键技术,提出了“无路区域有路化”的技术途径与无路区域数字路网的概念,构建了无路导航技术体系;最后,结合无路导航相关技术的实践,展现了其应用潜力。无路导航的研究将进一步丰富导航的内涵,拓宽导航应用边界。

关键词：无路导航导航电子地图通过性数字路网无路区域有路化

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Environmental Monitoring Technology for Marine Natural Gas Hydrate

Environmental Monitoring Technology for Marine Natural Gas H...

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2023年中国地球科学联合学术年会

作者： Liang Qianyong Ye Jianliang qin xuwen Dong Yifei Xie Wenwei Zhong Chao Guo Binbin Guangzhou Marine Geological Survey China Geological Survey

Natural gas hydrate(NGH) is considered as one of the new clean energy sources of the 21st century with the highest potential. The environmental issues of NGH production have attracted the close attention of scientists in various countries. In 2017 and 2020, China Geological Survey successfully organized two rounds of NGH production test in the South China Sea, which set a number of world records, marking a significant leap from "exploratory test production" to "experimental test production", and also indicating an important breakthrough in environmental safety of NGH production test. China Geological survey attaches great importance to the environmental impact of NGH research work. Since 2011, we have research methane leakage, underwater landslides, subsidence, and marine ecological change may cause by NGH exploration. And the marine environment baseline characteristics before the production test in Shenhu sea area have been clarified. In addition, environmental security has also been effectively guaranteed via a comprehensive environmental monitoring system built during the NGH production test. The monitoring system considered methane leakage, seabed subsidence, marine environment and sea surface atmosphere environment. The whole process was monitored via multiple means, in multiple layers, in all domains, and in real time. After the production test, the marine environment tracking survey have been carried out in time to effectively discuss and verify the environmental impact of NGH production test. The results of the two rounds of NGH production test showed that the content of dissolved methane in seawater and the seabed environment characteristics is consistent with the background values, indicating that the two rounds of production test did not cause seabed landslide, methane leakage and other environmental problems, and make no difference on the marine environment basically.

关键词： Natural gas hydrates Production test Environmental monitoring Environmental impact

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Submarine Continental Slopes Stability Prediction of Natural Gas HydratesBased on Machine Learning

Submarine Continental Slopes Stability Prediction of Natural...

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Offshore Technology Conference, OTC 2025

作者： Chen, Yu He, Yufa Wang, Yixuan Zhou, Yunjian Fu, Qiang qin, xuwen Liu, Dingyuan Tian, Zheng Zhang, Kexin CNOOC Research Institute Ltd State Key Laboratory of Offshore Natural Gas Hydrates Beijing China Huairou Laboratory Beijing China China Aero Geophysical Survey and Remote Sensing Center for Natural Resources Beijing China

ISBN: (纸本)9781959025610

In the process of extracting naturally-occurring oceanic gas hydrates, the dissociation of hydrates can causea reduction in soil strength. This reduction has the potential to trigger slope failure and submarine landslides,which present a catastrophic threat to offshore facilities and hydrate production. This research aims to create a robust and accurate machine-learning model that can efficiently predict stability of submarine continental slopes where gas hydrates are widespread. By collecting and analyzing 144 relevant cases, a comprehensive dataset was constructed, incorporating slope basic data, overlying and underlying layer data, and geological parameters of the hydrate layer. After conducting a correlation coefficient analysis between the characteristic parameters of the dataset and the output, the key characteristic parameters were determined. To model the dataset and assess its performance, four machine learning techniques were employed: Random Forest(RF), XGBoost, K-Nearest Neighbors (KNN), and Support Vector Machine (SVM). Formation physical parameters, geotechnical parameters, and NGH parameters were taken as input parameters, and the stability of NGH slopes was taken as prediction indicator. Evaluation metrics such as the ROC and confusion matrix were employed to comprehensively evaluate these models’ classification ability. Among these algorithms,the RF algorithm achieves the best prediction accuracy and AUC value, demonstrating its potential in submarine continental slopes stability prediction of natural gas hydrates. Additionally, sensitive analysis using Gini impurity calculations revealed that hydrate decomposition degree is the most significant factor affecting slope stability, followed by the burial depth and thickness of the hydrate layer. The slope angle,cohesion, and internal friction angle also have significant impacts. This study provides a new perspective for predicting submarine continental slopes stability with NGH and offers a scientific

关键词： Landslides

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Optimization of the Natural Gas Hydrate Hot Water Injection Production Method: Insights from Numerical and Phase Equilibrium Analysis

SSRN

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SSRN 2023年

作者： Zhang, Zhaobin Li, Yuxuan Li, Shouding He, Jianming Li, Xiao Xu, Tao Lu, Cheng qin, xuwen Key Laboratory of Shale Gas and Geoengineering Institute of Geology and Geophysics Chinese Academy of Sciences Beijing100029 China Innovation Academy for Earth Science Chinese Academy of Sciences Beijing100029 China College of Earth and Planetary Sciences University of Chinese Academy of Sciences Beijing100049 China Oil and Gas Resources Survey China Geological Survey Ministry of Natural Resources Beijing100083 China Guangzhou Marine Geological Survey China Geological Survey Ministry of Natural Resources Guangzhou510075 China

The heat injection during depressurization is a crucial technique for sustaining the long-term gas production rate of natural gas hydrates. To analyze the production patterns and mechanisms of hydrate dissociation under various heat injection conditions and to further optimize heat injection strategies, this study establishes a reservoir-scale three-dimensional heterogeneous computational model using a self-developed hydrate simulator. A novel in-situ heating method utilizing bottom seawater is proposed for heat injection, and comprehensive analyses of heating power and injection rates are conducted. The results indicate that increasing heating power at a constant injection rate enhances gas production rates while reducing thermal efficiency. Simultaneously, under constant heating power, gas production rates initially increase and then decrease with increasing injection rates, revealing the presence of an optimal injection rate. This paper introduces the concepts of temperature driving force and temperature modification ratio, analyzes the mechanisms of heat injection development, and derives an optimized strategy for hot water injection through curve fitting. This research enhances our understanding of the integrated approach involving thermal stimulation and depressurization, providing significant guidance for future production endeavors. © 2023, The Authors. All rights reserved.

关键词： Curve fitting

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Effects of the seepage capability of overlying and underlying strata of marine hydrate system on depressurization-induced hydrate production behaviors by horizontal well

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MARINE AND PETROLEUM GEOLOGY 2021年 128卷 105019-105019页

作者： Yang, Lin Ye, Jianliang qin, xuwen Liang, Qianyong Wu, Xuemin China Geol Survey Guangzhou Marine Geol Survey Guangzhou 510075 Peoples R China China Geol Survey Gas Hydrate Engn Technol Ctr Guangzhou 510075 Peoples R China China Geol Survey Beijing 100083 Peoples R China

Marine gas hydrates mostly occur in high-water content and non-diagenetic submarine sediments without tight stratigraphic traps. Therefore, the seepage capability of overlying and underlying strata (OUS) serves as a crucial parameter to analyze hydrate production behaviors. This study focuses on the numerical simulation study on the effects of the seepage capability of OUS on hydrate production behaviors in depressurization-induced production of three-phase hydrate deposits using a horizontal well. As shown by the simulation results, in the early stage of hydrate production, the permeability of the OUS had little effects on gas production rates. In long-term hydrate production, the hydrate deposit with lower permeability OUS has higher cumulative gas production, larger gaswater ratio and hydrate dissociation scope, and less cumulative water production. Moreover, the hydrate production efficiency first decreased rapidly and then tended to be stable as the permeability of OUS increased, and hydrate production behaviors are similar while the permeability of OUS larger than 1.0 mD. Herein, a waterresisting layers were constructed in overlying and/or underlying strata to decrease the seepage capability of OUS. Compared to the original hydrate deposits, the cumulative gas production and gas-water ratio increased by 31% and 147%, respectively but the water production was only 76% on the 5th year of the simulated production in which water-resisting layers were designed. Furthermore, the water-resisting layer in underlying strata produced more significant effects on hydrate production efficiency than the layer in overlying strata. All these indicate that the low-permeability OUS (especially in underlying strata) can restrain fluid invading into hydrate reservoirs, increase the pressure gradient of hydrate reservoirs and significantly improve the hydrate production efficiency during long-term hydrate production. Therefore, water-proof reformation in OUS may be an effective me

关键词： Marine gas hydrate Seepage capability Water-resisting layer Horizontal well Depressurization

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