油包水型原油乳状液核磁共振T_2谱特征与形成机理分析
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摘要
为认识油包水型原油乳状液核磁共振T_2谱中各峰的形成机理,采用低场核磁共振CPMG自旋回波法测量了不同含水率的油包水型原油乳状液,分析了油包水型原油乳状液的T_2谱特征,探讨了T_2谱中各个峰的形成机理,并通过含Mn Cl_2·4H_2O油包水型原油乳状液的核磁共振实验进行了验证。结果表明:油包水型原油乳状液T_2谱中存在三个峰,连续相中的原油发生自由流体弛豫形成T_(2A)峰,被油束缚在分散相水滴表面的水发生表面流体弛豫形成T_(2B)峰,远离液滴表面液滴内部的水发生自由流体弛豫形成T_(2C)峰;含Mn Cl_2·4H_2O油包水型原油乳状液的T_2谱中含有两个峰,未受Mn Cl_2·4H_2O影响的原油自由弛豫形成T_(2N)峰;Mn Cl_2·4H_2O使水的自由弛豫和表面弛豫时间缩短,共同形成T_(2M)峰,验证了原油乳状液T_2谱中各个峰的弛豫机理分析。这些结果为利用低场核磁共振T_2谱深入研究原油乳状液的性质奠定了基础。
In order to cognize the generation mechanism of the peaks in NMR T_(2 )spectrum of W/O(water in oil)crude oil emulsion,the method of low-field NMR(nuclear magnetic resonance)CPMG(Carr-Purcell-Meiboom-Gill)spin-echo was used to measure the W/O crude oil emulsions with different water content,and the characteristics of T_2spectra were analyzed.The formation and change mechanism of the peaks in NMR T_(2 )spectra was presented,and then it was validated by the NMR experiment of W/O crude oil emulsions containing MnCl_2·4H_2O.The results showed that:There were three peaks in the T_2 spectrum.The T_(2A)peak was from the free fluid relaxation in the continuous phase of crude oil.The surface fluid relaxation occurred in the water on the surface of droplets in dispersed phase bound by the oil,and the T_(2B) peak was formed.The free fluid relaxation occurred in the water away from the surface of the droplet,and the T_(2C) peak was formed.T_2 spectrum of W/O crude oil emulsion containing MnCl_2·4H_2O had two peaks.The T_(2N )peak was from the free relaxation of crude oil that was not affected by MnCl_2·4H_2O,and the process of free relaxation and surface relaxation in water sped up by MnCl_2·4H_2O formed the T_(2M) peak,which verified the relaxation mechanism of the peaks in T_2 spectra of the crude oil emulsions.These results lay a foundation for further study on the properties of crude oil emulsion by low-field NMR T_2 spectra.
In order to cognize the generation mechanism of the peaks in NMR T_(2 )spectrum of W/O(water in oil)crude oil emulsion,the method of low-field NMR(nuclear magnetic resonance)CPMG(Carr-Purcell-Meiboom-Gill)spin-echo was used to measure the W/O crude oil emulsions with different water content,and the characteristics of T_2spectra were analyzed.The formation and change mechanism of the peaks in NMR T_(2 )spectra was presented,and then it was validated by the NMR experiment of W/O crude oil emulsions containing MnCl_2·4H_2O.The results showed that:There were three peaks in the T_2 spectrum.The T_(2A)peak was from the free fluid relaxation in the continuous phase of crude oil.The surface fluid relaxation occurred in the water on the surface of droplets in dispersed phase bound by the oil,and the T_(2B) peak was formed.The free fluid relaxation occurred in the water away from the surface of the droplet,and the T_(2C) peak was formed.T_2 spectrum of W/O crude oil emulsion containing MnCl_2·4H_2O had two peaks.The T_(2N )peak was from the free relaxation of crude oil that was not affected by MnCl_2·4H_2O,and the process of free relaxation and surface relaxation in water sped up by MnCl_2·4H_2O formed the T_(2M) peak,which verified the relaxation mechanism of the peaks in T_2 spectra of the crude oil emulsions.These results lay a foundation for further study on the properties of crude oil emulsion by low-field NMR T_2 spectra.
引文
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[2]张瑞,霍锦华,彭志刚,等.低场核磁共振法对油基钻井液乳状液乳滴稳定性的研究[J].分析测试学报,2016,35(11):1445-1450.
[3]Alejandro A Pe?a,Hirasaki G J.Enhanced characterization of oilfield emulsions via NMR diffusion and transverse relaxation experiments.[J].Advances in Colloid&Interface Science,2003,105(1):103-150.
[4]Fridjonsson E O,Flux L S,Johns M L.Determination of mean droplet sizes of water-in-oil emulsions using an Earth’s field NMRinstrument[J].Journal of Magnetic Resonance,2012,221(none):97-102.
[5]Vermeir L,Sabatino P,Balcaen M,et al.Evaluation of the effect of homogenization energy input on the enclosed water volume of concentrated W/O/W emulsions by low-resolution T2-relaxometry[J].Food Hydrocolloids,2014,34(1):34-38.
[6]Sandnes R,Simon S,Sj?blom J,et al.Optimization and validation of low field nuclear magnetic resonance sequences to determine low water contents and water profiles in W/O emulsions[J].Colloids&Surfaces APhysicochemical&Engineering Aspects,2014,441(3):441-448.
[7]刘杰,王殿生,崔汪明.原油乳化液低场核磁共振测量参数优化与T2谱特征分析[J].实验室研究与探索,2018,37(04):26-31+86.
[8]李琼,洪富强,薛德山,杨宗礼,刘金玉.核磁共振测量甲醇汽油中甲醇含量的实验研究[J].当代化工,2018,47(11):2468-2471.
[9]高汉宾,张振芳.核磁共振原理与实验方法[M].武汉:武汉大学出版社,2008:492-493.
[10]Brownstein K R,Tarr C E.Importance of classical diffusion in NMRstudies of water in biological cells[J].Physical Review A,1979,19(6):2446-2453.
[11]龚国波,孙伯勤,刘买利,等.岩心孔隙介质中流体的核磁共振弛豫[J].波谱学杂志,2006,23(3):379-395.
[12]王殿生,周丽霞,刘超卓,等.物理实验教程——近代物理实验[M].东营:中国石油大学出版社,2016:110-111
[13]Korringa J,Seevers D O,Torrey H C.Theory of Spin Pumping and Relaxation in Systems with a Low Concentration of Electron Spin Resonance Centers[J].Physical Review,1962,127(4):1143-1150.
[14]Marciani L,Ramanathan C,Tyler D J,et al.Fat emulsification measured using NMR transverse relaxation.[J].Journal of Magnetic Resonance,2001,153(1):1-6.
[15]刘瑞晨.关于表面张力的实验探讨[J].物理教师,2008,29(10):36-36.
[16]康万利,李金环,赵学乾.界面张力和乳滴大小对乳状液稳定性的影响[J].油气田地面工程,2005,24(1):11-12.
[17]Ter Beek L C,Ketelaars M,Mccain D C,et al.Nuclear magnetic resonance study of the conformation and dynamics of beta-casein at the oil/water interface in emulsions.[J].Biophysical Journal,1996,70(5):2396-402.
[18]王忠东,王东.顺磁离子对核磁共振弛豫响应的影响及其应用的实验研究[J].测井技术,2003,27(4):270-273.
[19]彭石林,尉中良,管志宁.顺磁物质对岩石核磁弛豫特性影响的实验研究[J].石油物探,2002,41(3):372-376.
[20]Bloembergen N.Comments on''Proton Relaxation Times in Param agnetic Solutions''[J].Journal of Chemical Physics,1961,34(3):842-850.
[21]Bloembergen N,Purcell E M,Pound R V.Relaxation Effects in Nuclear Magnetic Resonance Absorption[J].Phys Rev,2015,73(7):679-712.