页岩油储层D—T2核磁共振解释方法

D—T₂二维核磁共振能够快速、直观地区分不同性质、不同赋存状态的孔隙流体，已成为储层评价的热门技术，但对于页岩油储层，常规储层的D—T₂孔隙流体解释图版并不适用，考虑受限扩散、内部梯度等影响因素的修正图版也难以满足页岩油储层油、水识别的要求。为此，采用理论分析与实验分析相结合的方法，对D—T₂孔喉尺度分辨率、流体含量分辨率、孔隙流体解释图版3个关键要素进行了深入研究。结果表明，D—T₂孔喉尺度分辨率、流体含量分辨率均低于T₂一维核磁共振，难以检测到T₂短于2 ms、含量低于0.2%的流体信号；D—T₂信号位置与流体含量有关，且随着流体含量的递增，具有随机游走特性。2口页岩油井的应用表明，基于流体含量信号响应轨迹的D—T₂流体解释图版能够实现页岩油储层的准确解释。

Discuss on D-T2 NMR interpretation of oil shale

D-T₂ two-dimensional nuclear magnetic resonance (NMR) could quickly and visually distinguish different type, different occurrence state of pore fluid, and become the hot technology for reservoir evaluation, but for oil shale, D-T₂ pore fluid interpretation chart of conventional reservoir is not suitable. The correction chart, considering restricted diffusion, internal gradient, etc., is also difficult to meet the requirements of oil and water recognition in oil shale. Therefore, three key scientific problems of D-T₂ pore throat scale resolution, fluid content resolution and pore fluid interpretation chart are studied by combining theoretical analysis and experimental analysis. The results show that the pore throat scale resolution and fluid content resolution of D-T₂ NMR was lower than that of T₂ NMR, and it was difficult to detect the fluid signal with T₂ shorter than 0.2ms and content less than 0.2%.The location of D-T₂ signal is related to fluid content and has a random walk property as fluid content increases. The applications of two shale oil wells show that the D-T₂ fluid interpretation chart based on the signal response trajectory can achieve accurate interpretation of oil shale.