摘要
致密砂岩微观结构控制着储层的储集和渗流能力，对油气的勘探与开发至关重要。文中以鄂尔多斯盆地南梁油田长9储层为例，运用核磁共振、高压压汞、扫描电镜、阴极发光等手段刻画了致密砂岩储层的微观结构特征，采用分形理论将致密砂岩储层孔隙分为大孔（孔隙半径大于0.10 μm）、中孔（孔隙半径介于0.01~0.10 μm）和小孔（孔隙半径小于0.01 μm），在此基础上，开展了致密砂岩储层分类评价。结果表明：强烈的压实作用是致密砂岩储层普遍致密化的原因，在强烈压实作用的基础上，胶结作用加剧了储层的致密化，而溶蚀作用则改善了储层的品质；在致密砂岩储层中，不仅不同储层之间差异性较大，而且同一储层内部的微观结构也非常复杂；随着孔隙半径的增大，孔隙的非均质性逐渐增强，其中大孔控制着储层的物性；根据大孔孔隙度，将致密砂岩储层分为3类。将高压压汞、核磁共振、分形理论相结合，能够定量地表征致密砂岩储层的微观特征，进而确定影响储层品质的关键因素，为致密砂岩储层分类评价提供可靠的依据。
Abstract
The storage capacity and seepage capacity in reservoir are controlled by the microstructure of tight sandstone, which is critical for oil and gas exploration and development. Taking the Chang 9 reservoir in the Nanliang Oilfield of the Ordos Basin as an example, the microstructural characteristics of tight sandstone reservoirs were described by using nuclear magnetic resonance(NMR), high-pressure injection, scanning electron microscope and cathode luminescence. Then, the fractal theory was applied to classify the pore of tight sandstone reservoirs into macropore (＞0.10 μm), mesopore(0.01￣0.10 μm) and micropore(＜0.01 μm). The classification evaluation of tight sandstone reservoirs are carried out on this basis. The results indicate that strong compaction is the reason for the general densification of tight sandstone reservoirs. On the basis of strong compaction, cementation aggravates the densification of the reservoir, while dissolution improves the quality of the reservoir. In tight sandstone reservoirs, not only are there great differences between different reservoirs, but also the microstructure within the same reservoir is extremely complex. With the increase of pore radius, the heterogeneity of pores increases gradually, in which macropores control the physical properties of the reservoir. According to the macro porosity, tight sandstone reservoirs are divided into three types. It is concluded that the combination of high-pressure injection, nuclear magnetic resonance and fractal theory can quantitatively characterize the microscopic property of tight sandstone reservoirs, and then determine the key factors affecting the quality of the reservoir, which provide a reliable basis for the classification evaluation of tight sandstone reservoirs.
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