页岩油储层T_(2)-T_(1)二维核磁共振测量参数敏感性分析

Sensitivity Analysis of T_(2)-T_(1)2D NMR Measurement Parameters in Shale Oil Reservoirs

为了提高二维核磁共振(NMR)在页岩油储层测量结果的可靠性,从NMR实验室岩心分析、井场移动式全直径岩心扫描、测井三类不同应用场景出发,分析了页岩油储层T_(2)-T_(1)二维NMR响应特征及影响因素.针对不同的应用场景,分别提出了页岩油储层的T_(2)-T_(1)二维NMR测量参数优化方法.实验室岩心NMR分析除了关注磁场强度、测量序列外,还需要注意回波间隔(TE)和回波组数的选择.井场移动式全直径岩心NMR扫描时,需要重点关注TE和最短等待时间(Tw)的设置,为保证快弛豫组分T1维度的收敛,最短Tw应至少设置为1 ms.NMR测井受限于采集条件,需要重点关注数据处理中的布点范围和平滑因子,以对不同信噪比的数据进行解释和修饰;页岩油NMR孔隙度小于5%为差储层,其低信噪比导致NMR结果的准确性难以保证.T_(2)-T_(1)二维NMR测量参数的系统性分析为页岩油储层二维NMR探测方法优化提供了参考依据,有助于提高NMR测量结果的精度,进而得到更加可靠的储层参数信息.

In order to improve the reliability of two-dimensional nuclear magnetic resonance(2D NMR)measurement in shale oil reservoirs,the T_(2)-T_(1)2D NMR response characteristics and influencing factors of shale oil reservoirs were analyzed in three scenarios:laboratory core analysis,wellsite mobile full-diameter core scanning and logging.For different application scenarios,the optimization method of T_(2)-T_(1) NMR measurement parameters for shale oil reservoirs were proposed.Laboratory core measurements require attention to the choice of echo interval time(TE)and number of echo groups,in addition to the different magnetic field strengths and measurement sequences.When scanning full-diameter cores at the well site,it is necessary to focus on TE and minimum waiting time(Tw).To ensure the convergence in T_(1) dimension of quickly relaxed component,the minimum Tw should be set to at least 1 ms.NMR logging is limited by the acquisition conditions.It is necessary to focus on the distribution range and smoothing factor in data processing to interpret and modify data with different signal-to-noise ratios.A poor shale oil reservoir with NMR porosity less than 5%is difficult to ensure the accuracy of NMR results for its low signal-to-noise ratio.The systematic analysis of T_(2)-T_(1)2D NMR measurement parameters provides a reference for the optimization of 2D NMR detection methods for shale oil reservoirs,which helps to improve the accuracy of NMR measurements and obtain more reliable reservoir information.