Diagenesis Of Shihezi Formation In Linxing Area,Ordos Basin

The tight reservoir of Shihezi Formation in Linxing area in Ordos Basin has good oil and gas shows.This paper is focus on reservoir diagenesis study which is significant to oil and gas potential recognition and in-depth evaluation in this structural belt.On the basis of thin-section,mercury injection porosimetry,SEM,cathodoluminsecence,X-ray diffractometer,rock-eval and pollen test,a comprehensive research on diagenesis type,diagensis stage,diagensis sequence and diagenetic facies is conducted against tight reservoir in study formation,and the influence factor of reservoir property is discussed.The lithology of tight reservoir of Shihezi Formation in Linxing area is chiefly mid-fine grained sandstone,and the pore types are mainly consists of secondary pores which is source from dissolution intergranular pore and dissolution intragranular pore.The diagenesis type of reservoir include compaction,cementation,replacement and dissolution.The diagenetic stage of reservoir is in the middle diagenetic stage A.The diagentic facies of reservior include six types,such as compaction pressolution facies,carbonate cementation facies,cementation-weak dissolution facies,authigenic kaolinite filling intergranular pore facies,secondary dissolution pore facies,primary pore and secondary solution pore facies.Reservior physical is better in the secondary pores facies,primary pore facies,authigenic kaolinite filling intergranular pore facies and weak cementation dissolution facies of upper Shihezi formation reservior,which is mainly distributed in He2,He3 and He4.Reservior physical is better in the secondary pores facies,primary and secondary pore facies,authigenic kaolinite filling intergranular pore facies of low Shihezi formation reservior,which is mainly distributed in He5,He6 and He8.The tight reservoir property of Shihezi Formation in Linxing area shows a positive correlation with grain size of sandstone,lithic content,feldspar content,and shows a negative correlation with content of quartz and carbonate.The mechanical compression is the most important factor that deteriorate physical properties,and cementation is the second factor.among all the facies,primary and secondary solution pores,secondary solution hole permeability is best,compaction pressolution facies and carbonate cementation facies are the worst.