鄂尔多斯盆地太原组砂岩缝合线特征及成因OA北大核心CSTPCD

Stylolites were widely developed in Taiyuan Formation sandstones at northern Ordos Basin with complex genesis mechanisms,and have important influence on the physical properties of sandstone reservoirs.Based on comprehensive analysis of core,scanning electron microscopy,energy dispersive spectrometry,X-ray diffraction and cast thin section,the geometry,mineral composition and genetic mechanism of sandstone stylolites in Taiyuan Formation are documented.The study indicates that the amplitude of sandstone stylolites in Taiyuan Formation varies obviously,and these stylolites can be classified into wave type,peak type,rectangular column type,composite type and network interweaved type.The sandstone stylolites are composed of organic carbon,quartz,illite,kaolinite,pyrite,rutile and zircon.The content of illite in the clay minerals is much higher than that in the surrounding rock,while the content of kaolinite is much lower than that in the surrounding rock.The organic matter and clay minerals of the sandstone stylolites are typical of sedimentary origin.They are catalysts for siliceous migration and precipitation,and lead to the silica precipitation and the proliferation of clastic quartz particles in the stylolites and surrounding sandstone pores.The stylolites are the products of pressure solution of sedimentary organic matter during burial,and are controlled by the diagenesis of sedimentary clay minerals and organic matters.The siliceous precipitation and quartz enlargement associated with the sandstone stylolites are the main factors for the quartz sandstone compaction in Taiyuan Formation in the study area.However,fractures which were prone to be developed along the stylolites can improve the permeability.