鄂尔多斯盆地东缘上古生界泥页岩储层定量表征

Quantitative Characterization of Shale Reservoir of Upper Paleozoic Shale in the Eastern Margin of Ordos Basin

页岩气主要以游离态和吸附态两种形式赋存在泥页岩中,泥页岩中的微孔隙和微裂缝是页岩气的主要储集空间和渗流通道,孔裂隙的发育程度关系到泥页岩中含气量的多少。结合场发射扫描电镜、氩离子抛光和核磁共振等技术,对鄂尔多斯盆地东缘台头剖面上古生界泥页岩中微孔隙和微裂缝的形态进行分析,并对微米级孔隙、纳米级孔隙、裂缝的大小和发育程度进行定量分析。分析认为：台头剖面泥页岩中微米级孔隙孔径平均值分布范围为1.32～5.58μm,平均面孔率分布范围为19.48%～23.66%,有机质纳米级孔隙平均孔径分布范围为56.51～80.75 nm,平均面孔率分布范围为7.45%～9.66%,裂缝百分数分布于0.69%～5.13%,有效孔隙度为0.25%～1.33%,占总孔隙的16%～46%。综合分析认为台头剖面山西组泥页岩储层最佳,山西组泥页岩埋深较浅,微米级孔隙发育,裂缝百分数和可动流体百分数分别为2.18%、10.82%,有效孔隙度均值为0.76%,占总孔隙的16%～41%。

Shale gas exists in forms of free state and adsorption state in shale. Micro pore and micro fracture in shale are the main locations of the reservoir space and the drainage channels of the shale gas and the gas content is related to the pore fracture growth degree. So it is very important to study the micro pore and the micro fracture in the shale reservoir. In this paper, based on the results of the field emission scanning electron microscopy, the argon ion polishing and the nuclear magnetic resonance, the micro pore and micro crack morphologies in the Upper Paleozoic in the eastern margin of Ordos Basin are analyzed. The pore size and the development degree of the micro-scale pore, the nano-scale pore and the fracture are quantitatively analyzed. The comprehensive analysis shows that the main reservoir space of shale is the micropore and the microcrack with organic pore as revealed mainly by the argon ion polishing and the clay mineral micro pore as revealed mainly by the scanning electron microscope. The micron pore size is in the range of 1.32-5.58 μm and its average area percent of pore is in the range of 19.48%-23.66%. The average size of the organic micro pore is in the range of 56.51-80.75 nm and its average area percent of pore is in the range of 7.45%-9.66%. The percent of crack is in the range of 0.69%-5.13%. Effeetive porosity is in the range of 0.25%-1.33%, which aceounts for 16%-46% of total porosity. Comprchensive analysis reveals that the shale reservoir of Shanxi of Taitou is the best, because of the relatively low buried depth, the full development of micro-scale pore, the relatively high pereentage of crack/micro crack of 56.51-80.75 nm and its average area percent in the range of 7.45%-9.66%. The proportions of the crack and the movable fluid are 2.18%, 10.82%, respectively, and the mean value of effective porosity is 0.76% amounting to 16%-41% of the total pore. The quantitative study of micro pore and micro crack provides a reliable basis for the further study of shale gas of Upper Paleozoic in this region.