天然气水合物分解沉积层内水流速度分布特性
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摘要
天然气水合物(NGH)是一种储量巨大的新型清洁能源,具有极大的开采潜力.水合物开采过程中水流速度分布特性是揭示含水合物沉积层中流体运移机制的关键参数.目前有关含水合物沉积层水流速分布特性处于研究瓶颈,缺少实验研究,核磁共振成像(MRI)是一种有效的研究方法.本文在6 MPa压力、274.15 K温度的条件下进行了天然气水合物恒容生成实验,并在0.5 K梯度水合物升温分解过程中利用MRI对水相截面速度分布进行了测试.研究发现在含水合物填砂岩芯的横截面处存在正速度区域和负速度区域;填砂岩芯内水合物的分布影响正速度和负速度的分布;在等梯度升温分解过程中,填砂岩芯中水相截面正流速区域沿水合物富集区表面向内部逐渐变大;水合物的存在对水的流动速度具有一定的削弱作用,流速越大削弱作用越明显.
The nature gas hydrates(NGHs) are a kind of clean and new type energy with huge reserves, which has a great exploitation potential. Water flow velocity distribution characteristic is a key parameter for revealing fluid migration mechanism in hydrate sediments during the hydrate exploitation process. At present, there are few experimental studies on the water flow velocity distribution in hydrate sedimentary layers by using magnetic resonance imaging(MRI).Meanwhile, there is still a blank for the application of MRI in hydrate seepage characteristics research. The constant volume method for methane hydrate formation with the initial pressure of 6 MPa and the temperature of 274.15 K were used in this paper. And a method which used a constant step of 0.5 K in the temperature-increasing process to control hydrate dissociation was used to research the water phase velocity distribution. A standard spin echo pulse sequence was chosen to obtain the 2D proton density weighted images in this study. The results showed that there are two different water velocity areas with plus velocity and minus velocity in the cross section of the hydrate-saturated sediment core. The distribution of the hydrate in the hydrate-saturated sediment core influenced the two different velocity area(plus velocity and minus velocity). The plus water phase velocity area will gradually increasing along the surface of the hydrate enrichment area to the interior with the temperature increase process. There is a certain weakening effect of the presence of hydrate for the flow of water. And the greater the flow velocity, the more obvious the weakening effect.
The nature gas hydrates(NGHs) are a kind of clean and new type energy with huge reserves, which has a great exploitation potential. Water flow velocity distribution characteristic is a key parameter for revealing fluid migration mechanism in hydrate sediments during the hydrate exploitation process. At present, there are few experimental studies on the water flow velocity distribution in hydrate sedimentary layers by using magnetic resonance imaging(MRI).Meanwhile, there is still a blank for the application of MRI in hydrate seepage characteristics research. The constant volume method for methane hydrate formation with the initial pressure of 6 MPa and the temperature of 274.15 K were used in this paper. And a method which used a constant step of 0.5 K in the temperature-increasing process to control hydrate dissociation was used to research the water phase velocity distribution. A standard spin echo pulse sequence was chosen to obtain the 2D proton density weighted images in this study. The results showed that there are two different water velocity areas with plus velocity and minus velocity in the cross section of the hydrate-saturated sediment core. The distribution of the hydrate in the hydrate-saturated sediment core influenced the two different velocity area(plus velocity and minus velocity). The plus water phase velocity area will gradually increasing along the surface of the hydrate enrichment area to the interior with the temperature increase process. There is a certain weakening effect of the presence of hydrate for the flow of water. And the greater the flow velocity, the more obvious the weakening effect.
引文
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16 Han S I,Marseille O,Gehlen C,et al.Rheology of blood by NMR.J Magn Reson,2001,152:87-94
17 Sederman A J,Mantle M D,Buckley C,et al.MRI technique for measurement of velocity vectors,acceleration,and autocorrelation functions in turbulent flow.J Magn Reson,2004,166:182-189
18 Chen B,Yang M,Zheng J,et al.Measurement of water phase permeability in the methane hydrate dissociation process using a new method.Int JHeat Mass Transfer,2018,118:1316-1324
19 Li P F,Lei X H,Xu H,et al.A review on researches on factors affecting gas hydrate phase equilibrium(in Chinese).Nat Gas Chem Ind,2012,37:12-17[李鹏飞,雷新华,徐浩,等.天然气水合物相平衡影响因素研究.天然气化工(C1化学与化工),2012,37:12-17]
20 van den Heuvel M M,Peters C J,de Swaan Arons J.Influence of water-insoluble organic components on the gas hydrate equilibrium conditions of methane.Fluid Phase Equilib,2000,172:73-91
21 Sun D L,Wu Q,Zhang B Y.Influence of“memory effect”on induction time of gas hydrate formation(in Chinese).J Harbin Inst Tech,2006,38:2177-2179[孙登林,吴强,张保勇.“记忆效应”对瓦斯水合物生成诱导时间的影响.哈尔滨工业大学学报,2006,38:2177-2179]
22 Liu W,Wu Z,Li Y,et al.Experimental study on the gas phase permeability of methane hydrate-bearing clayey sediments.J Nat Gas Sci Eng,2016,36:378-384
23 Ghezzehei T,Kneafsey T.Capillary Pressure and Relative Permeability of Methane Hydrate Bearing Sediments.In:Proceedings of the Annual Offshore Technology Conference.Houston,2010.2-12
24 Sean W Y,Sato T,Yamasaki A,et al.CFD and experimental study on methane hydrate dissociation Part I.Dissociation under water flow.AIChEJ,2007,53:262-274
25 Yang L,Falenty A,Chaouachi M,et al.Synchrotron X-ray computed microtomography study on gas hydrate decomposition in a sedimentary matrix.Geochem Geophys Geosyst,2016,17:3717-3732
2 Lu S M.RETRACTED:A global survey of gas hydrate development and reserves:Specifically in the marine field.Renew Sust Energy Rev,2015,41:884-900
3 Sloan Jr E D,Koh C A.Clathrate Hydrates of Natural Gases.Boca Raton:CRC Press,2007
4 Collett T S.Energy resource potential of natural gas hydrates.AAPG Bull,2002,86:1971-1992
5 Sloan E D.Fundamental principles and applications of natural gas hydrates.Nature,2003,426:353-359
6 Denney D.Toward production from gas hydrates:Status,technology,and potential.J Pet Tech,2008,60:82-84
7 Falser S,Uchida S,Palmer A C,et al.Increased gas production from hydrates by combining depressurization with heating of the wellbore.Energy Fuels,2012,26:6259-6267
8 Seol Y,Kneafsey T J.Methane hydrate induced permeability modification for multiphase flow in unsaturated porous media.J Geophys Res,2011,116:B08102
9 Seol Y,Kneafsey T J,Tomutsa L,et al.Preliminary relative permeability estimates of methanehydrate-bearing sand.In:Proceedings of TOUGHSymposium 2006.Lawrence Berkeley National Laboratory,Berkeley,California,May 15-17,2006
10 Bottomley P A.NMR imaging techniques and applications:A review.Rev Sci Instruments,1982,53:1319-1337
11 Doughty D A,Tomutsa L.Multinuclear NMR microscopy of two-phase fluid systems in porous rock.Magn Reson Imag,1996,14:869-873
12 Masuda Y.A field-scale simulation study on gas productivity of formations containing gas hydrates.In:Proceedings of 4th International Conference on Gas Hydrates,May 19-23,Yokohama,Japan,2002.40-46
13 Szalinski L,Abdulkareem L A,Da Silva M J,et al.Comparative study of gas-oil and gas-water two-phase flow in a vertical pipe.Chem Eng Sci,2010,65:3836-3848
14 Sankey M,Holland D,Sederman A,et al.Magnetic resonance velocity imaging of liquid and gas two-phase flow in packed beds.J Magn Reson,2009,196:142-148
15 Kuethe D O,Gao J H.NMR signal loss from turbulence:Models of time dependence compared with data.Phys Rev E,1995,51:3252-3262
16 Han S I,Marseille O,Gehlen C,et al.Rheology of blood by NMR.J Magn Reson,2001,152:87-94
17 Sederman A J,Mantle M D,Buckley C,et al.MRI technique for measurement of velocity vectors,acceleration,and autocorrelation functions in turbulent flow.J Magn Reson,2004,166:182-189
18 Chen B,Yang M,Zheng J,et al.Measurement of water phase permeability in the methane hydrate dissociation process using a new method.Int JHeat Mass Transfer,2018,118:1316-1324
19 Li P F,Lei X H,Xu H,et al.A review on researches on factors affecting gas hydrate phase equilibrium(in Chinese).Nat Gas Chem Ind,2012,37:12-17[李鹏飞,雷新华,徐浩,等.天然气水合物相平衡影响因素研究.天然气化工(C1化学与化工),2012,37:12-17]
20 van den Heuvel M M,Peters C J,de Swaan Arons J.Influence of water-insoluble organic components on the gas hydrate equilibrium conditions of methane.Fluid Phase Equilib,2000,172:73-91
21 Sun D L,Wu Q,Zhang B Y.Influence of“memory effect”on induction time of gas hydrate formation(in Chinese).J Harbin Inst Tech,2006,38:2177-2179[孙登林,吴强,张保勇.“记忆效应”对瓦斯水合物生成诱导时间的影响.哈尔滨工业大学学报,2006,38:2177-2179]
22 Liu W,Wu Z,Li Y,et al.Experimental study on the gas phase permeability of methane hydrate-bearing clayey sediments.J Nat Gas Sci Eng,2016,36:378-384
23 Ghezzehei T,Kneafsey T.Capillary Pressure and Relative Permeability of Methane Hydrate Bearing Sediments.In:Proceedings of the Annual Offshore Technology Conference.Houston,2010.2-12
24 Sean W Y,Sato T,Yamasaki A,et al.CFD and experimental study on methane hydrate dissociation Part I.Dissociation under water flow.AIChEJ,2007,53:262-274
25 Yang L,Falenty A,Chaouachi M,et al.Synchrotron X-ray computed microtomography study on gas hydrate decomposition in a sedimentary matrix.Geochem Geophys Geosyst,2016,17:3717-3732