D-T_2二维核磁共振脉冲序列改进设计及性能对比
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摘要
针对现有D-T2二维核磁共振脉冲序列无法兼顾扩散系数测量范围和横向弛豫分辨率的难题,在对比PFG(脉冲梯度场)、STE-PFG(stimulated echo PFG)、BP-PFG(Bi-polar PFG)、改良式CPMG(Car-Purcel-Meiboom-Gill)、"扩散编程"、多回波间隔CPMG脉冲序列技术特点的基础上,提出一种基于脉冲梯度场的两窗口、双变量D-T2改进脉冲序列。PFG、改良式CPMG、D-T2改进脉冲序列在气水、油水、稠油模型不同信噪比条件下的正反演数值模拟结果表明,D-T2改进脉冲序列达到了平衡扩散系数测量范围和横向弛豫分辨率的设计要求,在非常规油气储层的探测和测井评价中具有广泛应用前景,可为推动D-T2二维核磁共振技术的发展提供有利条件。
In order to solve the difficulties in D-T22 D NMR technology that cannot balance the dynamic range of the diffusion coefficient measurements and the transverse relaxation resolution in practical applications,an improved design of D-T22 D NMR pulse sequence,based on two " windows" and bivariate on pulsed filed gradient,was proposed,after summarizing the technical characteristics of PFG( pulsed filed gradient),STE-PFG( stimulated echo pulsed filed gradient),BP-PFG( Bi-polar pulsed filed gradient),modified CPMG( Car-Purcel-Meiboom-Gill), " diffusion editing",and multi echo intervals CPMG pulse sequences. The numerical simulation results of different structural models( gas-water,oil-water and heavy oil-water) under different signal-to-noise ratios show that the modified D-T2 pulse sequence balances the diffusion coefficient measurement range and transverse relaxation resolution successfully. The new pulse sequence has wide applications in the exploration and formation evaluation for unconventional reservoir,and will benefit future development of D-T22 D NMR technology.
In order to solve the difficulties in D-T22 D NMR technology that cannot balance the dynamic range of the diffusion coefficient measurements and the transverse relaxation resolution in practical applications,an improved design of D-T22 D NMR pulse sequence,based on two " windows" and bivariate on pulsed filed gradient,was proposed,after summarizing the technical characteristics of PFG( pulsed filed gradient),STE-PFG( stimulated echo pulsed filed gradient),BP-PFG( Bi-polar pulsed filed gradient),modified CPMG( Car-Purcel-Meiboom-Gill), " diffusion editing",and multi echo intervals CPMG pulse sequences. The numerical simulation results of different structural models( gas-water,oil-water and heavy oil-water) under different signal-to-noise ratios show that the modified D-T2 pulse sequence balances the diffusion coefficient measurement range and transverse relaxation resolution successfully. The new pulse sequence has wide applications in the exploration and formation evaluation for unconventional reservoir,and will benefit future development of D-T22 D NMR technology.
引文
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[13]王忠东,肖立志,刘堂宴.核磁共振弛豫信号多指数反演新方法及其应用[J].中国科学:G辑,2003,33(4):323-332.WANG Zhongdong,XIAO Lizhi,LIU Tangyan.A new multi-exponential inversion method of NMR relaxation signal and its application[J].Science in China(Series G),2003,33(4):323-332.
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[15]TANNER J E.Use of the stimulated echo in NMR diffusion studies[J].The Journal of Chemical Physics,1970,52(5):2523-2526.
[16]KARLICEK J R F,LOWE I J.A modified pulsed gradient technique for measuring diffusion in the presence of large background gradient[J].Journal of Magnetic Resonance,1980,37(1):75-91.
[17]COTTS R M,HOCH M J R,SUN T,MARKERT J T.Pulsed field gradient stimulated echo methods for improved NMR diffusion measurements in heterogeneous systems[J].Journal of Magnetic Resonance,1989,83:252-266.
[18]VANDUSSCHOTEN D.Flexible PFG NMR desensitized for susceptibility artifacts,using the PFG multiple-spinecho sequence[J].Journal of Magnetic Resonance,Series A,1995,112(2):237-240.
[19]曲岩涛,姜志敏,史京生,等.水驱油过程的核磁共振二维谱研究[J].波谱学杂志,2012,29(1):51-59.QU Yantao,JIANG Zhimin,SHI Jingsheng,et al.Water flooding studied by measuring NMR two-dimensional distribution function[J].Chinese Journal of Magnetic Resonance,2012,29(1):51-59.
[20]SUN B Q,DUNN K J.A global inversion method of multi-dimensional NMR logging[J].Journal of Magnetic Resonance,2005,172(1):152-160.
[21]谢然红,肖立志,刘家军,等.核磁共振多回波串联合反演方法[J].地球物理学报,2009,52(11):2913-2919.XIE Ranhong,XIAO Lizhi,LIU Jiajun,et al.A method for multiple echo trains jointing inversion of NMR relaxation measurements[J].Chinese Journal of Geophysics,2009,52(11):2913-2919.
[22]TAN M J,ZOU Y L,ZHOU C C.A new inversion method for(T2,D)2D NMR logging and fluid typing[J].Computers&Geosciences,2013,51(2):366-380.
[23]高阳,肖立志,谢庆明.基于BG理论确定Phillips方法的正则化参数并评价反演结果[J].中国石油大学学报:自然科学版,2014,38(3):50-56.GAO Yang,XIAO Lizhi,XIE Qingming.Evaluating regular parameter of Phillips method and assessing inversions based on BG theory[J].Journal of China University of Petroleum(Edition of Natural Science),2014,38(3):50-56.
[2]HURLIMANN M D,VENKATARAMANAN L.Quantitative measurement of two dimensional distribution functions of diffusion and relaxation in grossly inhomogeneous fields[J].Journal of Magnetic Resonance,2002,157(1):31-42.
[3]HURLIMANN M D,VENKATARAMANAN L,FLAUM C.The diffusion-spin relaxation time distribution function as an experimental probe to characterize fluid mixtures in porous media[J].Journal of Chemical Physics,2002,117(22):10223-10232.
[4]SONG Y Q,VENKATARAMANAN L,HURLIMANN M D,et al.T1-T2correlation spectra obtained using a fast two-dimensional Laplace inversion[J].Journal of Magnetic Resonance,2002,154(2):261-268.
[5]邓克俊.核磁共振测井理论及应用[M].东营:中国石油大学出版社,2010:9-148.
[6]HURLIMANN M D,FLAUM M,VENKATARAMANAN L,et al.Diffusion-relaxation distribution functions of sedimentary rocks in different saturation states[J].Magnetic Resonance Imaging,2003,21(3):305-310.
[7]SUN B Q,DUNN K J.Two-dimensional nuclear magnetic resonance petrophysics[J].Magnetic Resonance Imaging,2005,23(2):259-262.
[8]谢然红,肖立志.(T2,D)二维核磁共振测井识别储层流体的方法[J].地球物理学报,2009,52(9):2410-2418.XIE Ranhong,XIAO Lizhi.The(T2,D)NMR logging method for fluids characterization[J].Chinese Journal of Geophysics,2009,52(9):2410-2418.
[9]谭茂金,邹友龙.(T2,D)二维核磁共振测井混合反演方法与参数影响分析[J].地球物理学报,2012,55(2):683-692.TAN Maojin,ZOU Youlong.A hybrid inversion method of(T2,D)2D NMR logging and observation parameters effects[J].Chinese Journal Geophysics,2012,55(2):683-629.
[10]胡法龙,周灿灿,李潮流,等.基于弛豫-扩散的二维核磁共振流体识别方法[J].石油勘探与开发,2012,39(5):552-558.HU Falong,ZHOU C C,LI Chaoliu,et al.Fluid identification method based on 2D diffusion-relaxation NMR[J].Petroleum Exploration&Development,2012,39(5):552-558.
[11]STEJSKAL E O,TANNER J E.Spin diffusion measurement:spin echoes in the presence of a time-dependent field gradient[J].The Journal of Chemical Physics,1965,42(1):288-292.
[12]STEJSKAL E O.Use of spin echoes in a pulsed magneticfield gradient to study anisotropic,restricted diffusion and flow[J].The Journal of Chemical Physics,1965,43(10):3597-3603.
[13]王忠东,肖立志,刘堂宴.核磁共振弛豫信号多指数反演新方法及其应用[J].中国科学:G辑,2003,33(4):323-332.WANG Zhongdong,XIAO Lizhi,LIU Tangyan.A new multi-exponential inversion method of NMR relaxation signal and its application[J].Science in China(Series G),2003,33(4):323-332.
[14]VENKATARAMANAN L,SONG Y Q,HURLIMANN M D.Solving Fredholm integrals of the first kind with tensor product structure in 2 and 2.5 dimensions[J].IEEE Transactions on Signal Processing,2002,50(5):1017-1026.
[15]TANNER J E.Use of the stimulated echo in NMR diffusion studies[J].The Journal of Chemical Physics,1970,52(5):2523-2526.
[16]KARLICEK J R F,LOWE I J.A modified pulsed gradient technique for measuring diffusion in the presence of large background gradient[J].Journal of Magnetic Resonance,1980,37(1):75-91.
[17]COTTS R M,HOCH M J R,SUN T,MARKERT J T.Pulsed field gradient stimulated echo methods for improved NMR diffusion measurements in heterogeneous systems[J].Journal of Magnetic Resonance,1989,83:252-266.
[18]VANDUSSCHOTEN D.Flexible PFG NMR desensitized for susceptibility artifacts,using the PFG multiple-spinecho sequence[J].Journal of Magnetic Resonance,Series A,1995,112(2):237-240.
[19]曲岩涛,姜志敏,史京生,等.水驱油过程的核磁共振二维谱研究[J].波谱学杂志,2012,29(1):51-59.QU Yantao,JIANG Zhimin,SHI Jingsheng,et al.Water flooding studied by measuring NMR two-dimensional distribution function[J].Chinese Journal of Magnetic Resonance,2012,29(1):51-59.
[20]SUN B Q,DUNN K J.A global inversion method of multi-dimensional NMR logging[J].Journal of Magnetic Resonance,2005,172(1):152-160.
[21]谢然红,肖立志,刘家军,等.核磁共振多回波串联合反演方法[J].地球物理学报,2009,52(11):2913-2919.XIE Ranhong,XIAO Lizhi,LIU Jiajun,et al.A method for multiple echo trains jointing inversion of NMR relaxation measurements[J].Chinese Journal of Geophysics,2009,52(11):2913-2919.
[22]TAN M J,ZOU Y L,ZHOU C C.A new inversion method for(T2,D)2D NMR logging and fluid typing[J].Computers&Geosciences,2013,51(2):366-380.
[23]高阳,肖立志,谢庆明.基于BG理论确定Phillips方法的正则化参数并评价反演结果[J].中国石油大学学报:自然科学版,2014,38(3):50-56.GAO Yang,XIAO Lizhi,XIE Qingming.Evaluating regular parameter of Phillips method and assessing inversions based on BG theory[J].Journal of China University of Petroleum(Edition of Natural Science),2014,38(3):50-56.