含裂缝页岩核磁共振横向弛豫响应正演模拟及T2谱特征分析

Forward simulation and characteristic analysis on the low field NMR transverse relaxation response of fractured shale reservoir

裂缝的精细探测是页岩储层油气可动性评价的关键,核磁共振技术可实现多种尺度孔隙中流体的测量,已被广泛应用于非常规储层评价.然而,含裂缝页岩的核磁共振响应特征尚不明确.为此,提出一种基于三维CT数据建立的孔隙-裂缝双相介质模型方法,采用数值模拟方法系统研究了裂缝参数的核磁共振测井响应特征.模拟结果表明:裂缝的存在影响页岩的核磁共振T_(2)谱分布,裂缝张开度增大导致T_(2)谱向右偏移,纵横比增大造成T_(2)谱向左偏移;裂缝页岩的孔缝配置关系对页岩连通性起主导作用,孔缝配比减小,可动流体呈线性增长.

The accurate detection of fracture is important for oil and gas movability evaluation in shale reservoir.Nuclear Magnetic Resonance(NMR)technology can capable of measuring the fluid type and quantity in multiple scales of pores and has been widely used in unconventional reservoir evaluation.However,the NMR response characteristics of fractured shale still remain.In this paper,apore-fracture model based on 3DCT scanning data is proposed,and the NMR logging response characteristics of fracture parameters are systematically studied by numerical investigation.Numerical results show that the presence of fractures affects the T_(2)spectrum distribution.The increase of fracture width leads to the right shift of the T_(2)spectrum,and the increase of aspect ratio leads to the left shift of the T_(2)spectrum.The pore and fracture configuration of fractured-shale play a dominant role in shale connectivity,the movable fluid increasing linearly as the pore and fracture ratio decreases.