The Diagenesis Of Quartz And Its Effect On Reservoir Property

bridgehead sandstone of Taiyuan formation in eastern Ordos Basin is an important exploration horizon of Upper Paleozoic,which is a marine delta front deposit,which is a compact reservoir,and has undergone a strong diagenesis process.The siliceous cementation has the greatest influence on the reservoir physical properties.Finding out the development process of siliceous cementation can provide basis for exploration and development decision.On the basis of thin slice analysis,combined with the methods of casting sheet analysis,scanning electron microscope,cathode development,inclusion temperature measurement and strontium isotope,the petrological characteristics of bridgehead sandstone and the types and characteristics of siliceous cementation were studied.The mechanism of siliceous cementation and the effect of siliceous cementation on pore are studied.The main conclusions and understandings are as follows:1)The bridgehead sandstone underwent a strong diagenesis process,the clastic components underwent a strong transformation,and the feldspar components were basically transformed into clay minerals kaolinite or Illite during diagenesis.The composition of sandstone is similar to that of siliceous and clay minerals in general.2)Based on the combination of cementation type and occurrence,the rock forming type of silica gel is divided into 6 types.They are ?grade enlarged cementing,grade ?enlarged cementation,grade larger cementation,grade larger cementation,filling ? ?chlorite intermembrane pore cementation and filling intergranular pore cementation.3)There are five obvious characteristics of siliceous cementation in the study area:(1)Quartz augmentation cementation mostly terminates in carbonate cementation.(2)Intergrowth of quartz ?increase with kaolinite.(2)The siliceous cementation develops in the area where quartz particles gather.(4)In the microenvironment,muddy cementation,calcareous cementation and siliceous cementation can be seen in different regions.(5)Siliceous cementation and Illite cementation are not symbiotic.4)There are many possible sources of siliceous cementation,but the main sources are feldspar kaolinite and feldspar Illite.According to the alteration analysis of feldspar,the kaolinization formation temperature of plagioclase is relatively low,which is the main material source of quartz ?-?increase.Combined with strontium isotope analysis and inclusion temperature analysis,the end temperature of siliceous cementation is estimated to be between 145-175?.5)The development of intergranular pore is controlled by quartz particle and siliceous cementation,and intergranular pore develops between quartz particles,which decreases and finally disappears due to the increase of quartz.At present,the residual intergranular pores are found in quartz-enlarged intergranular.The development and distribution of pores are predicted by predicting the distribution of siliceous cementation,taking the lithologic distribution plan as the base map.The prediction results show that the intergranular pore is mainly developed in feldspar quartz sandstone area and the intergranular pore is mainly developed at the intersection of river channel.