鄂尔多斯盆地延长油气区山西组山2段储层物性影响因素

Influential factor and charactristics of Shan-2 Member of Shanxi Formation in Yanchang Oil-Gas Field,Ordos Basin

利用铸体薄片、扫描电镜、X线衍射及岩心和测井等各种资料,对鄂尔多斯盆地中东部延长油气区山2储层特征及影响因素进行分析。研究结果表明:研究区储层岩性主要为中细粒石英砂岩,成分成熟度较高,结构成熟度较低,储层空间以次生孔隙为主。孔隙结构以微孔微喉型为主,进汞曲线平台不明显,呈陡斜式,储层孔隙结构微观非均质性强。储层物性差,属低渗和特低渗气藏。储层特征受沉积作用和成岩作用综合影响,水下分流河道是形成有利储层的主要相带;压实作用和胶结作用是砂岩孔隙率降低的主要原因,分别造成19.5%和14%的原生孔隙丧失;溶蚀作用形成的次生孔隙在一定程度上改善了砂岩储集性能,溶蚀作用增加的孔隙率平均为1.7%。

The physical property and influential elements of Shan-2 Member of Shanxi Formation in Yanchang Oil-Gas Field in Ordos Basin were studied by using the cast slices, scanning electron microscope, porosity and permeability analysis, log interpretation and mercury injection test. The research results show that the main sandstones in the area are quartz sandstone and lithic quartz sandstone with lower compositional maaxrity and higher structure maturity. The pore space of reservoir mainly includes the primary residual intergranular pores and emposieu. Tiny pore and tiny throat are the main pore configurations. Mercury intrusion method shows that the micro heterogeneity of pore configuration is high and the connectivity of pore throat of Shan-2 sandstone reservoir is very weak, and thus it belongs to low permeability and porosity oil reservoir. The characteristics of reservoir are affected by deposition and diagenesis, and underwater distributary channel is the main favorable microfacie. Decrease of sandstone porosity is mainly caused by compaction and the cemention, which contribute 19.5% and 14% to the loss of primary pores, respectively. Secondary pore resulting from dissolution improves the poroperm of sandstone to some extent, while diaclases contribute less to improving the poroperm of sandstone, and dissolution increases porosity by 1.7%.