鄂尔多斯盆地旬邑探区延长组储层特征和开发效果

鄂尔多斯盆地旬邑探区延长组开发潜力较大,储层特征的定量评价对准确预测开发效果具有指导意义。选取延长组6段（长6）和延长组8段（长8）储层典型岩心进行实验分析,核磁共振实验结果显示长6和长8储层孔喉分布特征较为单一,不进行离心实验的情况下可利用核磁共振渗透率和T₂几何平均值计算可动流体百分数。恒速压汞实验结果表明,孔隙比喉道发育均匀,未开展其他实验的情况下可利用恒速压汞实验计算孔隙度。通过建立核磁共振和恒速压汞耦合求取完整孔喉半径分布的方法,确定了旬邑探区延长组长6和长8储层的表面弛豫率为0.15 μm/ms。核磁共振孔喉半径分布的计算结果显示,长6储层孔喉半径分布范围为0.01~433.10 μm,长8储层孔喉半径分布范围为0.01~403.91 μm,长6储层孔喉发育比长8储层均匀。通过定义拟粒间孔和拟溶蚀孔,拟溶蚀孔绝对体积占比揭示,长8储层渗流能力强于长6储层。建立了"拟溶蚀孔+含油饱和度"方法预测开发效果,分析认为拟溶蚀孔对试油产量的影响更大,进一步揭示了旬邑探区长8储层整体开发效果好于长6储层。

Reservoir characteristics and development performance of Yanchang Formation in Xunyi exploration area,Ordos Basin

Yanchang Formation in Xunyi exploration area of Ordos Basin has great development potential, and the quantitative evaluation of reservoir characteristics has a certain guiding significance for accurately predicting development performance. Typical cores of Chang 6 and Chang 8 reservoirs are selected for experiments. Nuclear Magnetic Resonance (NMR)results indicate that both Chang 6 and Chang 8 reservoirs show the relatively single distribution characteristics of pore throat; the percentage of movable fluid can be calculated using the NMR permeability or T₂ geometric mean without doing centrifugation experiments; the constant-rate mercury injection experiment results show the more uniform pore development than throat development, and the porosity can be calculated by constant-rate mercury injection experiment in case of no other experiments. This study establishes a method for obtaining complete pore throat radius distribution by the coupling between NMR and constant-rate mercury injection experiment; the surface relaxivity of Chang 6 and Chang 8 reservoirs of Yanchang Formation in Xunyi exploration area is determined as 0.15 μm/ms. The NMR experiment shows that the pore radius distribution in Chang 6 and Chang 8 reservoir is within the range of 0.01-433.10 μm and 0.01-403.91 μm respectively, indicating the more homogeneous pore throat development in the latter. Pseudo intergranular pores and pseudo dissolution pores are defined, and the absolute volume ratio of pseudo dissolution pores indicate Chang 8 reservoir has greater seepage capacity than Chang 6 reservoir. Moreover, this study sets up the method to predict development performance by "pseudo dissolution pores + oil saturation", and the analysis results show pseudo dissolution pores have a greater impact on the oil test production, thus achieving the prediction of oil well production. The further study reveals that on the whole, Chang 8 reservoir presents better development than Chang 6 reservoir in Xunyi exploration area.