核磁共振测井在致密含气砂岩中的应用

通过对核磁共振测井的T₂谱及其T₂截至值的合理选取，解释并获得了鄂尔多斯盆地西缘上古生界山西组、石盒子组致密砂岩储集层的总孔隙度、有效孔隙度、毛细管束缚水体积、可动水体积及渗透率等参数，据此预测的储集层孔隙结构特征与岩心分析测试结果很吻合。研究还发现，致密含气砂岩的T₂谱具有分布范围窄-中等，波形及差谱分析谱位置明显后移、分布中等、呈单峰的典型特征。结合常规测井资料，综合研究了致密砂岩储层特征及其含气层的测井响应。经测试验证，致密含气砂岩储层的核磁共振测井解释结果十分可靠，表明核磁共振测井可用于该区致密含气砂岩复杂储集层评价。

THE APPLICATION OF NUCLEAR MAGNETIC RESONANCE LOGGING IN GAS-BEARING TIGHT SANDSTONE

This paper interpreted and obtained such parameters as total porosity, effective porosity, capillary irreducible volume, removable water volume and permeability of tight sandstone reservoirs in Shanxi and Shihezi formations in upper Paleozoic by using T2 spectrum of nuclear magnetic resonance (NMR) logging and selecting T2 cutoff value reasonably. The pore structure properties of the reservoir derived from these parameters matched well with the core analysis results. The study also reveals that T2 spectrum of the gas-bearing tight sandstone has the typical characteristics of that the spectrum distribution expresses as narrow-medium extents, and the waveform and spectrum location of the difference spectrum analysis evidently shift backward with medium distribution and single peak value. Combining with the conventional logging data, the paper comprehensively researched the features of the tight sandstone reservoir and the logging response of the gas-bearing reservoir. The test results confirmed that the interpretation results of the gas-bearing tight sandstone from NMR logging are quite reliable, which indicates that NMR logging can be applicable for evaluating the complex reservoirs of the gas-bearing tight sandstone in this area.