推荐论文摘要

祁连山冻土区DK-9孔温度监测及天然气水合物稳定带厚度

王超群，丁莹莹，胡道功，等

推荐论文摘要

祁连山冻土区DK-9孔温度监测及天然气水合物稳定带厚度

王超群，丁莹莹，胡道功，等

祁连山冻土区木里盆地三露天井田自2008年首次钻采到天然气水合物实物样品以来，实现了中低纬度高山冻土区天然气水合物勘探的重大突破。天然气水合物钻孔 DK-9于2013年发现水合物，通过对该孔长期地温实时监测，获得了稳态的地温数据。结果表明，祁连山多年冻土区聚乎更矿区三露天井田冻土层底界为约163 m，冻土层的厚度达约160 m，冻土层内的地温梯度为1.38℃/100 m，冻土层以下的地温梯度达4.85℃/100 m。根据天然气水合物形成的温-压条件分析，聚乎更矿区具备较好的天然气水合物形成条件，天然气水合物稳定带底界深度处于510～617 m之间。

天然气水合物；温度监测；地温梯度；水合物稳定带；祁连山

来源出版物：现代地质, 2017, 31(1): 158-166

联系邮箱：胡道功，hudg@263.net

多孔介质中天然气水合物生成的主要影响因素

Khlebnikov VN，Antonov SV，Mishin AS，等

摘要：目前有关天然气水合物（以下简称水合物）的研究主要集中在物理化学性质考察和开采（分解）方法探索方面。在进行后者的研究过程中，地层渗流过程的物理模拟至关重要，但目前借助于石油开采研究中广泛应用的填砂管等多孔介质对水合物进行动态过程的研究却鲜有报道。为此，利用河砂填砂管在岩心驱替装置上进行了甲烷水合物生成过程的物理模拟，考察了地层温度、甲烷压力及地层模型性质参数等对水合物生成过程的影响。结果表明：（1）利用冰融水作为地层模型的束缚水可显著提升甲烷水合物的生成速率；（2）多孔介质条件下过程驱动力（即实验压力或温度偏离水合物相平衡对应值的程度）对甲烷水合物的生成起着决定性作用；（3）当甲烷压力高于水合物相平衡压力1.4倍以上，或者实验温度低于相平衡温度3℃以下时，甲烷水合物生成诱导期几乎不随温压条件的变化而变化；（4）渗透率、含水饱和度、润湿性等参数对实验中甲烷水合物的生成率不构成明显影响。

关键词：甲烷水合物；多孔介质；生成过程；天然气水合物地层；物理模拟；影响因素；诱导期；生成率

来源出版物：天然气工业, 37(5): 38-45

联系邮箱：Khlebnikov VN，khlebnikov_2011@mail.ru

基于支持向量机结合遗传算法的天然气水合物相平衡研究

马贵阳，宫清君，潘振，等

摘要：天然气水合物（以下简称水合物）具有高储气率和高可靠性等优点，在天然气储存及运输方面具有广泛的应用前景，同时水合物的存在也会给输气管道带来堵塞等严重影响，因此对水合物的生成研究具有重要意义。为此，对Ⅰ型水合物在无添加剂条件下的静态生成规律进行了研究。首先基于水合物动力学实验装置进行一系列实验，然后利用支持向量机（SVM）结合遗传算法（GA）建立了水合物生成预测模型（SVM＋GA）。据此将实验中得到的温度和压力数据进行预测和优化处理，并对上述数据进行非线性拟合，得出了相平衡曲线及其方程，计算得出了常温下生成水合物的相平衡压力为33.5 MPa，常压下生成水合物的相平衡温度为237.1 K。将分别由SVM+GA模型、Chen-Guo模型和vd W-P热力学模型所得到的数据与经典的实验数据进行了对比，其平均相对误差分别为2.678%、1.447%和3.249%。结论认为：SVM+GA模型具有较高的计算准确度，比Chen-Guo模型和vd W-P热力学模型更为简便，可为水合物开发研究提供更多的数据。

关键词：天然气水合物；可靠性；支持向量机；遗传算法；相平衡曲线；平均相对误差；计算准确度

来源出版物：天然气工业, 2017, 37(5): 46-52

联系邮箱：马贵阳，guiyangma1@163.com

天然气水合物形成与生长影响因素综述

丁麟，史博会，吕晓方，等

摘要：天然气水合物（NGH）是水分子和天然气分子形成的一种复杂的笼型晶体，其在油气管道输送、天然气储存和制冷等行业中都具有重要的研究意义和利用价值，但天然气水合物的形成是一个多组分、多阶段的复杂过程，不同因素对于天然气水合物形成和生长的影响尚有待明确。本文介绍了天然气水合物形成的物理过程以及水合物成核的3种机理假说；详细梳理了基质两亲性、添加剂、多孔介质环境和杂质、液体组成、温度压力以及流动条件等因素对于天然气水合物形成和生长的影响，并对其作了简要分析。同时指出，原油组成对于水合物抑制效果的定量化、蜡晶结构对于水合物形成过程中传质和传热的影响以及微观化的动力学抑制剂抑制机理等都是水合物相关研究中需要进一步深入探究和明确的问题。

关键词：天然气水合物；物理过程；形成；生长；影响因素

来源出版物：化工进展, 2016, 35(01): 57-64

联系邮箱：宫敬，ydgj@cup.edu.cn

南海天然气水合物远景区海洋可控源电磁探测试验

景建恩，伍忠良，邓明，等

摘要：为了测试我国自主设计与研发的海洋可控源电磁仪器性能及其在水合物探测中的适用性，本文从海洋可控源电磁法基本原理出发，首先根据试验海域水合物地质特征，建立简化地电模型开展理论研究，确定海洋可控源电磁试验的技术方案；利用研发的海洋可控源电磁仪器，在南海天然气水合物远景区开展探测试验，首次获得了我国深水海域的海洋可控源电磁数据。通过对采集数据进行处理与反演，获得了试验剖面的海底电性结构模型，揭示了4号测点下方存在一个50 m厚的高阻层，其电阻率为25 Ωm、顶部埋深为181 m，为该区天然气水合物调查提供了有价值的电性参考资料。研究结果表明，自主研发的海洋可控源电磁仪器性能达到了预期的设计指标，这标志着我国海洋可控源电磁探测技术向实用化进程迈出了重要一步。

关键词：海洋可控源电磁法；天然气水合物；南海；数据处理；反演

来源出版物：地球物理学报, 2016, 59(7): 2564-2572

联系邮箱：伍忠良，52936891@qq.com

南海东北部陆坡天然气水合物钻探区生物地层与沉积速率

陈芳，庄畅，周洋，等

摘要：2013年我国首次在南海东北部东沙陆坡实施天然气水合物钻探，并获取块状等可视天然气水合物样品。为了解钻区地层、天然气水合物产出带（the zone of gas hydrate occurrence）或天然气水合物储层的地层时代和沉积速率特征，对其中5个站位（GMGS05、GMGS07、GMGS08、GMGS09和GMGS16）的岩心沉积物进行钙质超微化石、有孔虫生物地层学和沉积速率变化的研究。钻孔取心最大深度为213.55 m。共识别出第四纪中更新世以来3个钙质超微化石事件和2个有孔虫事件，确定了钻探区所钻达最老地层为中更新统；天然气水合物产出带的地层时代为中更新世—全新世约0.44 Ma以来。钻区0.12，Ma以来的沉积速率介于36.9～73.3 cm/ka之间，平均值高达54.2 cm/ka，0.44 Ma以来平均沉积速率为47.4 cm/ka，表明东沙海域天然气水合物钻探区位于一高沉积速率堆积体上，高沉积速率更有利于天然气水合物的成藏，该结论与前人研究结果一致。

关键词：生物地层；沉积速率；中更新世；天然气水合物钻区；南海东北部陆坡

来源出版物：地球科学：中国地质大学学报, 2016 (3):416-424

联系邮箱：陈芳，Zhchenfang66@21cn.com

青藏高原昆仑山垭口盆地发现天然气水合物赋存的证据

吴青柏，蒋观利，张鹏，等

摘要：青藏高原多年冻土区是否存在天然气水合物一直是国内外广泛关注的问题，但一直没有确定的答案。通过钻探、地球物理测井以及气体地球化学研究，在昆仑山垭口盆地发现了天然气水合物赋存的证据。钻探发现250 m以下多个深度岩层存在大量气体释放异常，甲烷气体浓度为22%～32%，且具有天然气水合物分解间歇性释放的特征，这些气体释放层位具有显著的含天然气水合物特有的密度降低、侧向电阻率和声波波速的增大特征。同时多个深度上发现了与水合物分解产生甲烷密切相关的碳酸盐和黄铁矿等自生矿物。

关键词：昆仑山垭口盆地；多年冻土；天然气水合物；地球物理测井异常；气体释放

来源出版物：科学通报, 2015 (1): 68-74

联系邮箱：吴青柏，qbwu@lzb.ac.cn

天然气水合物热力学抑制剂作用机制及优化设计

赵欣，邱正松，黄维安，等

摘要：基于2种典型天然气水合物生成预测理论模型，结合水合物热力学抑制剂评价实验数据以及水活度测试结果，分析了水合物热力学抑制剂影响天然气水合物生成条件的作用机制，建立了水合物生成温度降低值与水活度的关系式。结果表明，水合物热力学抑制剂降低水合物生成温度，或提高水合物生成压力的作用机制是降低溶液的水活度，其抑制水合物生成效果随水活度的降低线性增加。通过模拟深水钻井环境，对典型的水合物热力学抑制剂氯化钠，以及钻井液常用的有机盐甲酸钠进行了水活度测试以及水合物抑制效果评价实验，探讨了可降低钻井液水活度的有机盐加重剂 Weigh作为水合物抑制剂的可能性。结果表明，加入氯化钠或甲酸钠降低水活度至0.84，钻井液可在1500 m水深条件下循环16 h无水合物生成；Weigh可大幅降低溶液水活度，水合物抑制效果优于氯化钠、甲酸钠以及由氯化钠和乙二醇组成的复合抑制剂。针对深水钻完井作业中遇到的必须使用低密度钻井液或完井液的情况，初步优化设计了低密度水合物抑制剂，可保证钻井液和完井液在低密度条件下（1.05～1.07 g/cm3）有效抑制水合物生成。

关键词：深水钻井；天然气水合物；热力学抑制剂；预测模型；作用机制；水活度；有机盐；低密度

来源出版物：石油学报, 2015, 36(6): 760-766

联系邮箱：邱正松，qiuzs63@sina.com

南海北部神狐海域天然气水合物钻探区第四纪以来的沉积演化特征

苏明，沙志彬，乔少华，等

摘要：南海北部神狐海域是我国首次获取海洋天然气水合物实物样品的海域。然而，陆坡区深水水道和海底峡谷的侵蚀以及频发的沉积物失稳，将会加剧地层对比和沉积相识别的难度，导致目前该区域典型地震相-沉积相特征、沉积体类型、成因机制和空间匹配关系等方面还缺少精细的研究，特别是第四纪以来的沉积演化涉及较少，区域内水合物形成和分布的沉积地质条件尚不清晰。基于海底地形特征的描述、层序地层格架的对比和地震资料的综合解释，本次研究在第四纪以来的沉积充填序列中识别出5种典型的地震相类型，并分析了对应的沉积体类型：进积型的陆坡、第四纪早期发育的小型浊积水道、沉积物失稳（滑移和滑塌）、海底峡谷和伴生的沉积物变形、以及深海沉积-块体流沉积的复合体。通过沉积单元的空间匹配关系，将沉积演化划分为3个阶段：浊积水道侵蚀-沉积物再沉积阶段、陆坡进积-沉积物失稳阶段、海底峡谷的侵蚀-充填阶段。研究结果表明，受第四纪早期小型浊积水道的侵蚀，再沉积的沉积物将在中-下陆坡以“近源”的方式堆积下来，可能具有相对较好的物性条件，从而可被视为适于水合物赋存的有利沉积体。进积型陆坡带来的沉积物易于发生失稳，在研究区内广泛分布，因其具有较小的沉积物颗粒粒度和较好的垂向连续性，可被认为是水合物的区域盖层。大量发育的海底峡谷及伴生的沉积物变形，将会侵蚀和破坏先前沉积的有利沉积体，使其呈现为“斑状/补丁状”的平面展布特征，进而影响了神狐海域水合物的分布。因此，神狐海域第四纪以来的沉积演化是钻探区水合物不均匀性分布的关键控制因素之一。

关键词：天然气水合物；地震相；沉积演化；神狐海域天然气水合物钻探区；南海北部

来源出版物：地球物理学报, 2015, 58(8): 2975-2985

联系邮箱：吴能友，wuny@ms.giec.ac.cn

冷泉形成的数值模拟研究

刘善琪，尹凤玲，朱伯靖，等

摘要：海底冷泉形成的一种可能机制是海平面下降引起天然气水合物的分解。本文基于对冷泉渗漏特征的分析，建立了二维轴对称模型，利用有限元方法定量分析了南海区域海平面下降对冷泉形成的影响。结果表明，末次冰盛期（26.5～19.0 ka BP）海平面下降引起的冷泉活动可以持续到现在，但是从水合物停止分解至今，超孔隙压力的极值在持续减小，而流体向海底的渗漏达西速度先快速减小、然后缓慢减小。同时发现，流体向海底的渗漏达西速度与管状通道的渗透率、通道周围介质的渗透率以及通道的半径等有关，估计目前的冷泉活动还可以持续10000年以上。海平面下降引起的天然气水合物分解，可能是影响全球气候变化的一个重要因素。

关键词：天然气水合物；冷泉；有限元；海平面下降

来源出版物：地球物理学报, 2015, 58(5): 1731-1741

联系邮箱：李永兵，yongbingli@ucas.ac.cn

来源出版物：Chemical Engineering Science, 2016, 146:199-206

Study on gas hydrate formation and hydrate slurry flow in a multiphase transportation system

Lv, V; Shi, B; Wang, Y; Gong, J; et al.

Abstract: As oil and/or gas exploration and production enter deeper water, the flow assurance confronts challenges, one of which is the hydrate formation and blockage. Investigations about gas hydrate formation and hydrate slurry flow in a multiphase transportation system were performed on a newly constructed high-pressure experimental loop. On the basis of the experimental hydrate formation data, an inward and outward hydrate shell model was improved to predict the gas consumed amount during the hydrate formation process. With the help of a focused beam reflectance measurement and particle video microscope installed in this flow loop, the distribution of hydrate particles was observed,characterized in the coalescence and fragmentation. A“minimum safety flow rate” was first addressed for the safety of hydrate slurry flow in a multiphase transportation system. Then, the comparisons between our experimental data of the natural gas hydrate slurry flow pattern and the Mandhane flow pattern map revealed the influence of hydrate particles on the flow pattern of the slurry.Furthermore, the influence of the gas/liquid superficial velocity on the pressure drop was discussed at stratified flow for this gas hydrate slurry multiphase system.

来源出版物：Energy & Fuels, 2013, 27(12): 7294-7302

An inward and outward natural gas hydrates growth shell model considering intrinsic kinetics,mass and heat transfer

Shi, BH;Gong, J;Sun, CY; et al.

Abstract:The natural gas hydrates formation and growth at 2 MPa and 277.15 K were studied at different water cuts for water-in-condensate oil emulsions in the flow loop unit. The variations of gas consumption with time at different water cuts were obtained. The experimental results showed that the gas consumption value increased with the rise of water cut. The total water conversion rates not only depended on the water cuts, but also related to several other factors, two of which were the amount of the dissolved gas and the surface/volume ratio of the particles.No more natural gas transformed into hydrates after 3 h,which was likely caused by intrinsic kinetics, mass transfer and heat transfer limitations. An inward and outward natural gas hydrates growth shell model was proposed considering all the three limitations to simulate the gas and water consumptions to form natural gas hydrates.

来源出版物：Chemical Engineering Journal, 2011, 171(3):1308-1316

Thermal responses of a gas hydrate-bearing sediment to a depressurization operation

Yamamoto, K; Kanno, T; Wang, XX ; et al.

Abstract:As a part of a research program aiming to mobilize marine gas hydrate deposits as an energy resource, the worlds' first gas production attempt was performed in early 2013 in the Daini Atsumi Knoll,Eastern Nankai Trough, off Honshu Island, Japan. The test concluded with 119000 m3(under ambient conditions) of methane gas production during six consecutive days ofdepressurization operation through a borehole drilled at 1000 m water depth. As thermal and mass transportation in a heterogeneous geological formation are the governing factors of efficiency and effectiveness of the resource,the test was associated with intensive underground temperature monitoring. Temperature sensors installed in one production and two observation boreholes could detect temperature variations during gas production due to the endothermic gas hydrate dissociation process and mass/ heat transport around the boreholes. The measurements in the observation holes started one year before the test and continued until plug-and-abandonment,and thus enabled monitoring of both the initial temperature and temperature change arizing from recovery processes. The depth profiles of measured temperatures in all holes can be related to the geological features of the corresponding formation, and those thermal responses revealed the intervals where gas hydrate dissociation predominantly occurred. By analyzing the energy conservation in the production borehole, the gas and water production profiles could be estimated and major gas and water production zones were identified. Preliminary numerical analysis results show the range of formation permeability and that the observed temperature drop is equivalent to the heat consumption by hydrate dissociation for the volume of produced methane gas. Moreover, the thermal responses could provide some clues about the location and mechanism of the sand production event. This sand production event ultimately terminated the production operations on the seventh day of flow.

来源出版物：RSC Advances, 2017, 7(10): 5554-5577

The iġnik sikumi field experiment, alaska north slope: Design, operations, and implications for CO2–CH4exchange in gas hydrate reservoirs

Ray Boswell; David Schoderbek; Timothy S. Collett; et al.

Abstract: The Iġnik Sikumi Gas Hydrate Exchange Field Experiment was conducted by ConocoPhillips in partnership with the U.S. Department of Energy, the Japan Oil, Gas and Metals National Corporation, and the U.S.Geological Survey within the Prudhoe Bay Unit on the Alaska North Slope during 2011 and 2012. The primary goals of the program were to (1) determine the feasibility of gas injection into hydrate-bearing sand reservoirs and(2) observe reservoir response upon subsequent flowback in order to assess the potential for CO2exchange for CH4in naturally occurring gas hydrate reservoirs. Initial modeling determined that no feasible means of injection of pure CO2was likely, given the presence of free water in the reservoir.Laboratory and numerical modeling studies indicated that the injection of a mixture of CO2and N2offered the best potential for gas injection and exchange. The test featured the following primary operational phases: (1) injection of a gaseous phase mixture of CO2, N2, and chemical tracers;(2) flowback conducted at downhole pressures above the stability threshold for native CH4hydrate; and (3) an extended (30-days) flowback at pressures near, and then below, the stability threshold of native CH4hydrate. The test findings indicate that the formation of a range of mixed-gas hydrates resulted in a net exchange of CO2for CH4in the reservoir, although the complexity of the subsurface environment renders the nature, extent, and efficiency of the exchange reaction uncertain. The next steps in the evaluation of exchange technology should feature multiple well applications; however, such field test programs will require extensive preparatory experimental and numerical modeling studies and will likely be a secondary priority to further field testing of production through depressurization. Additional insights gained from the field program include the following: (1) gas hydrate destabilization is self-limiting, dispelling any notion of the potential for uncontrolled destabilization; (2) gas hydrate test wells must be carefully designed to enable rapid remediation of wellbore blockages that will occur during any cessation in operations; (3) sand production during hydrate production likely can be managed through standard engineering controls; and (4) reservoir heat exchange during depressurization was more favorable than expected—mitigating concerns for near-wellbore freezing and enabling consideration of more aggressive pressure reduction.

来源出版物：Energy & Fuels, 2016, 31(1): 140-153

联系邮箱：Ray Boswell; ray.boswell@netl.doe.gov

High-pressure gas hydrate autoclave hydraulic experiments and scale-up modeling on the effect of stirring RPM effect

Qureshi, MF; Atilhan, M; Altamash, T ; et al.

Abstract:A synthetic quaternary gas mixture (Methane =85.24%, Ethane = 10.03%, n-Hexane = 0.02 mol %, Carbon dioxide = 2.49% and Nitrogen = 2.22%) has been used to study the effect of different stirring rates between 100 and 1400 rotations per minute (RPM) on hydrate crystalformation in the high pressure autoclave cell (HPC). The experimental results obtained show that there exists a threshold limit above and below which hydrate formation decreases drastically. The results were used to determine the optimum-stirring rate at which maximum hydrate crystal formation is obtained in HPC. For the scale up purposes, using the experimental results, the dimensional analysis has been conducted on HPC to obtain optimum power and density ratio factors for the bench scale reactor system. So this work aims to facilitate the ongoing research for using hydrates for natural gas storage and transportation purposes.

关键词：hydrate production; gas transmission and storage;stirring; dimensional analysis

来源出版物：Journal of Natural Gas Science and Engineering, 2017, 38: 50-58

联系邮箱：Atilhan, M; mert.atilhan@qu.edu.qa

Methane hydrate-liquid-vapour-equilibrium phase condition measurements in the presence of natural amino acids

Bavoh, CB; Partoon, B; Lal, B ; et al.

Abstract:This work reports the thermodynamic effect of five amino acids on methane hydrate phase boundary. The studied amino acids are glycine, alanine, proline, serine and arginine. To effectively investigate the impact of selected amino acids on methane hydrates formation, the methane hydrate-liquid-vapour-equilibrium (HLwVE) curve is measured in amino acids aqueous solutions. Experiments are performed at concentration range of 5 wt%–20 wt% by employing the isochoric T-cycle method in a sapphire hydrate cell reactor at pressures and temperatures range of 3.86–9.98 MPa and 276.50–286.00 K, respectively. Results suggests that, all studied amino acid inhibits methane hydrate formation. Glycine showed the highest inhibition effect with an average depression temperature of 1.78 K at 10 wt%. The impact of inhibition is due to amino acids hydrogen bonding energies, confirmed via COSMO-RS predictions and side group alkyl chain. The inhibition impact of glycine is found to be in the range of some ionic liquid (OH-EMIM-Cl) and slightly higher than ethylene glycol (a conventional thermodynamic hydrate inhibitor) at 10 wt%. The methane hydrate dissociation enthalpies in the presence of amino acids are calculated using Clausius–Clapeyron equation, which suggests that, amino acids do not take part in methane hydrate cage occupation during hydrate formation.

关键词：methane; gas hydrates; amino acids; thermodynamic hydrate inhibitors; HLwVE points

来源出版物：Journal of Natural Gas Science and Engineering, 2017, 37: 425-434

联系邮箱：Bavoh, CB; bhajan.lal@utp.edu.my

Review of natural gas hydrates as an energy resource: Prospects and challenges

Chong, ZR; Yang, SHB; Babu, P; et al.

Abstract:Natural gas is the cleanest burning fossil fuel and has been identified as a strong candidate for energy resource compared to oil and coal. Natural gas hydrate is an energy resource for methane that has a carbon quantity twice more than all fossil fuels combined and is distributed evenly around the world. Several field trials on energy production from hydrate resources have been conducted, and their outcomes revealed the possibility of energy production from hydrate resources. In this paper,we review various studies on resource potential of natural gas hydrate, the current research progress in laboratory settings, and several recent field trials.Possible limitation in each production method and the challenges to be addressed for large scale production are discussed in detail. Whilst there are no technology stoppers to exploit or produce methane from hydrates,specific technological breakthroughs will depend on the effective management of the sand and water during production, as well as the appropriate mitigation of environmental risks.

关键词：gas hydrates; natural gas; energy recovery;energy resource; methane hydrates;unconventional gas

来源出版物：Applied Energy, 2016, 162: 1633-1652

联系邮箱：Linga, P; praveen.linga@nus.edu.sg

Rapid methane hydrate formation to develop a cost effective large scale energy storage system

Veluswamy, HP; Wong, AJH; Babu, P; et al.

Abstract:Natural gas (NG) is the cleanest burning fossil fuel and its usage can significantly reduce CO2emissions from power plants. With its widespread use, there is an ever increasing need to develop technologies to store NG on a large scale. NG storage via clathrate hydrates is the best option for a large scale storage system because of its non-explosive nature, mild storage conditions, highvolumetric capacity and being an environmentally benign process. In this work, we demonstrate a new method to achieve rapid methane hydrate formation in an unstirred tank reactor configuration (UTR) at moderate temperature and pressure conditions employing tetrahydrofuran (THF)as a promoter. For the first time, THF is reported to act both as a thermodynamic and an excellent kinetic promoter for methane hydrate formation. We demonstrate a multi-scale experimental validation of our method to a volumetric sample scale-up factor of 120 and internal reactor diameter scale-up factor of 10. Further, new insights on the dissociation behavior of the hydrates are reported. There is a competitive edge for storing NG via clathrate hydrates compared to compressed natural gas storage both in terms of cost and safety.

关键词：gas hydrates; energy storage; tetrahydrofuran;enhanced kinetics; natural gas storage; unstirred tank reactor

来源出版物：Chemical Engineering Journal, 2016, 290:161-173

联系邮箱：Linga, P; Praveen.Linga@nus.edu.sg

Gas hydrate plug formation in partially-dispersed water–oil systems

Akhfash, M; Aman, ZM; Ahn, SY; et al.

Abstract:The formation of gas hydrate plugs in deep water oil and gas flowlines poses severe operational and safety hazards. Previous work has established a mechanism able to describe plug formation in oil-continuous systems,which relies on the assumption that all the water remains emulsified in the oil phase. However, light hydrocarbon fluids, including condensates, may not stabilize water-in-oil emulsions, and the current mechanistic model cannot reliably assess the risk of plug formation in this scenario. This study presents a comprehensive set of experiments conducted in a high-pressure sapphire autoclave apparatus using 10 vol% to 70 vol% water in partially-dispersing mineral oil at three fixed rotational speeds: 300, 500 and 900 RPM. Pressure and temperature were monitored continuously in the autoclave, providing direct estimates of hydrate growth rate, alongside measurements of the motor torque required to maintain constant mixing speed. A new conceptual mechanism for plug formation has been developed based on the visual observations made during these experiments, where a small hydrate fraction (2 vol%–6 vol%) in the oil phase was observed to disrupt the stratified water–oil interface and help disperse the water into the oil. This disruption was followed by an increase in the hydrate growth rate and particle agglomeration in the oil phase. In the final stages of hydrate growth for systems with low turbulence and high watercut, hydrate particles in the visual autoclave were observed to form a moving bed followed by full dispersion of water and oil, rapid hydrate growth and deposition on the wall. These rapid hydrate growth and deposition mechanisms significantly increased the maximum resistance-to-flow for partially-dispersing systems in comparison with mixtures that are fully dispersed under similar conditions.

关键词：gas hydrates; water-oil emulsion; deposition;partial dispersion; hydrate plug; flow assurance

来源出版物：Chemical Engineering Science, 2016, 140:337-347

联系邮箱：May, EF; eric.may@uwa.edu.au

Analysis of heat transfer influences on gas production from methane hydrates using a combined method

Song, YC; Wang, JQ; Liu, Y; et al.

Abstract:Heat transfer affects the pressure and temperature distributions of hydrate sediments, thereby controlling hydrate dissociation. Therefore, its study is essential for planning hydrate exploitation. Previously, a two-dimensional axisymmetric model, to investigate the influence of heat transfer on hydrate exploitation from hydrate-bearing sediments, was developed and verified.Here, we extended our investigation to the influence of heat transfer on methane gas production using a combined method coupling depressurization and thermal stimulation.Our simulations showed that during decomposition by the combined method, a high specific heat capacity of the hydrate-bearing porous media or a high initial water content could inhibit gas generation. However, the initial water content had only a weak influence on the cumulative gas production and generation rate. The influence of water and methane heat convection was also weak. An increase of the thermal conductivity initially inhibited hydrate dissociation but later promoted it. The implementation of the combined method increased gas generation compared with using only thermal stimulation. However, the benefits gradually diminished with an increasing heat injection temperature.

关键词：methane hydrate; combined method; conduction;convection; injection temperature; heat transfer

来源出版物：International Journal of Heat and Mass Transfer, 2016, 92: 766-773

联系邮箱：Zhao, JF; jfzhao@dlut.edu.cn

Evaluation of gas production from methane hydrates using depressurization, thermal stimulation and combined methods

Song, YC; Cheng, CX; Zhao, JF; et al.

Abstract:To investigate the gas production from methane hydrate-bearing sediments, the gas production processes from methane hydrate in porous media using depressurization, two-cycle warm-water injection and a combination of the two methods were characterized in this study. The methane hydrates were formed in porous media with various initial hydrate saturation (Shi) in a pressure vessel. The percentage of gas production, rate of gas production, and energy efficiency were obtained and compared using the three methods. The driving force of the hydrate dissociation at different stages of depressurization was analyzed and ice formation during the gas production was observed. For the two-cycle warm-water-injection method, the percentage of gas production and the energy efficiency increased with increasing of Shi. However, due to the large amount of warm water needed to heat the porous media at the dissociation site, the percentage of gas production was lower than the other two methods under the same experimental conditions. The experimental results proved that the combined method had obvious advantages for hydrate exploitation over the depressurization and warmwater-injection method in terms of the energy efficiency,percentage of gas production and average rate of gas production, and with increasing of Shi, the advantages are enhanced. For the Shiof 51.61%, the percentage of gas production reaches 74.87%, which had increments of 18.63% and 31.19% compared with the depressurization and warm-water-injection methods. The energy efficiency for the combined method were 31.47, 49.93 and 68.13 for Shiof 31.90%, 41.31% and 51.61%, respectively.

关键词：methane hydrate-bearing sediments; energy efficiency; depressurization; thermal injection; combination production; buffer effect

来源出版物：Applied Energy, 2015, 145: 265-277

联系邮箱：Zhao, JF; jfzhao@dlut.edu.cn

Mechanical properties of hydrate-bearing turbidite reservoir in the first gas production test site of the Eastern Nankai Trough

Yoneda, J; Masui, A; Konno, Y; et al.

Abstract:The study of mechanical properties of marine sediments is essential for the prediction of the occurrence of geohazards (e.g., subsea landslides and seafloor subsidence) and the design of submarine structures for offshore industry. In this study, triaxial compression tests of gas-hydrate-bearing sandy sediments and clayey-silty sediments were conducted. The sediments were recovered by pressure coring in the Eastern Nankai Trough, the area of the first Japanese offshore production test. Soil index properties were measured and revealed porosity of 40%–50%, with porosity decreasing gradually with greater depth below the seafloor. The mean particle size was less than 10 μm for clayey-silty sediments and approximately 100 μm for sandy sediments. Permeability, estimated by a consolidation process of triaxial testing and with X-ray diffraction analysis, depended on the content of fines,which consisted chiefly of mica, kaolinite, and smectite.The results of undrained compression tests for clayey-silty sediments showed positive excess pore pressure under all test conditions. This mechanical behavior indicates that the core samples are normally consolidated sediments. Drained compression tests showed that the strength and stiffness of sandy sediments increase with hydrate saturation.Furthermore, the volumetric strain of hydrate-bearing sediments changed from compression to dilative. This result was obtained for hydrate saturation values (Sh) of more than 70%. The shear strength of hydrate-bearing turbidite sediments of the Eastern Nankai Trough is shown to be a function of the confining pressure.

关键词：hydrate-bearing sand; triaxial test; pressure core;mechanical property; hydrate saturation

来源出版物：Marine and Petroleum Geology, 2015, 66:471-486

联系邮箱：Yoneda, J; jun.yoneda@aist.go.jp

编辑：王微

Investigation of natural gas hydrate slurry flow properties and flow patterns using a high pressure flow loop

Ding, L; Shi, B; Lv, X; et al.

The formation and agglomeration of hydrates have been a major hazard to the operating safety ofdeep-sea oil/gas transportation pipeline. Although many studies have been conducted to investigate the hydrates formation and particle behaviors during the transportation,studies on the gas–slurry flow properties and effects of hydrates on multiphase flow patterns are still almost blank. In this work, a series of experiments were conducted in a high pressure flow loop, using the materials of a pseudo single-liquid-phase (saturated water/oil emulsion) and a gas–liquid multiphase, respectively. It was found that hydrates agglomeration was more violent and the flow property was worse in the gas–liquid multiphase system. When hydrates formed in the gas–liquid multiphase system, the liquid flow rate would decrease in all experimental conditions while the gas flow rate showed three different changing types: decreasing,increasing or keeping constant. These changes of the flow rate would further induce a transition of the gas–liquid multiphase flow pattern in the loop. Based on the experimental data, two flow pattern maps were made. One involved the effects of hydrates while the other did not.Through the comparison between the two flow pattern maps, it is confirmed that the influence of hydrates on the flow pattern is significant. The differences between the two flow pattern maps were also analyzed using a flow pattern transition model to provide an insight into the mechanism of how hydrates affect the multiphase flow pattern.