核磁共振岩心实验分析在低孔渗储层评价中的应用

根据核磁共振(NMR)岩心实验分析的基本原理、方法和相关参数模型的研究进展,对鄂尔多斯盆地东部ZC油田3062井延长组长6油层组低孔渗砂岩样品进行了储层物性、孔隙结构和束缚水饱和度等参数的NMR岩心实验分析,并将其与常规岩心测试参数进行了分析与对比,探讨了低孔渗储层NMR岩心实验分析的精度及其应用效果。结果表明,3062井长6油层组砂岩属于典型的低孔渗储层,孔隙度在8.6%~13.0%,渗透率在(0.07~1.27)×10-3μm2;低孔渗砂岩样品NMR岩心实验所分析的孔隙结构、孔隙度、束缚水饱和度数据与其常规岩心分析结果基本一致,且系统偏差较小,但基于NMR实验参数的储层渗透率预测模型尚存在较多的不确定性,核磁共振渗透率预测结果与常规岩心分析渗透率数据存在较大偏差。

Application of NMR core experimental analysis in evaluation of low-porosity and low-permeability sandstone reservoirs

Nuclear magnetic resonance (NMR) core experimental analysis is a new developing technique in experi-mental geology. Based on the principles and methods of NMR core experimental analysis, as well as some improved parametric models, a series of reservoir parameters of Chang6 low-porosity and low-permeability oil-bearing sandstone core samples from well 3062 in the ZC Oil Field in the eastern Ordos Basin were systematically measured by NMR. Additionally, the accuracy and relative error of the NMR analysis were calculated and discussed by means of recognized exact method of conventional core experimental analysis as control group. It is revealed that the Chang6 oil-bearing sandstones are typical low-porosity and low-permeability reservoirs, with porosity ranging from 8.6% to 13.0%, and permeability from 0.07×10-3 to 1.27×10-3 μm2. NMR core experimental analysis has advantages of convenience, high efficiency and accepted accuracy with a smaller relative error for testing the low-porosity and low-permeability reservoir parameters of porosity, microscopic pore structure and irreducible water saturation. However, compared with the results of conventional core analysis, there is a larger relative error in NMR prediction for the permeability parameters, which is most probably due to some uncertainty of the reservoir permeability predictive models.