三肇地区扶余和杨大城子油层储集层的成岩作用

DIAGENESIS OF RESERVIORS IN FUYU AND YANGDACHENGZI OF SANZHAO REGION

三肇地区下白垩统扶余和杨大城子油层储集岩主要为具有较高杂基含量的岩屑长石细砂岩和长石岩屑细砂岩。孔隙度在 1 ～ 2 1 3 之间 ,平均 10 9 。渗透率在 0 0 1× 10 -3 ～ 2 89× 10 -3 μm2 之间 ,平均 1 5 3×10 -3 μm2 。主要的成岩作用有压实作用、胶结作用、溶蚀作用、交代作用等。压实作用使孔隙大大减少 ;根据结构、阴极发光特征、碳氧稳定同位素成分、主要元素和微量元素含量可以推测方解石胶结物形成于早成岩作用的还原条件下 ,方解石胶结物的沉淀使沉积物 (岩 )的孔隙减少 ;长石和中基性火山岩岩屑的溶蚀产生的孔隙约占现有孔隙的 1/ 3;交代作用使大部分蒙皂石和高岭石已转变为伊利石和伊蒙混层 ,或绿泥石和绿蒙混层 ,对储集空间发育的影响不大。大部分储集岩的变化发生在早成岩作用阶段。

The reservoir rocks of Lower Cretaceous Fuyu and Yangdachenzi unites wrer deposited in channels on the deltaic flood plain in Sanzhao area. The reservoir rocks mainly consist of fine lithic arkose and feldspathic litharenite with abundant matrix.Porosity ranges from 10/0 to 21.30/0,with a mean of 10.90/0.Permeability ranges from 0.01×10 -3 to 289×10 -3 μm 2 with a mean of 1.53×10 -3 μm 2.Main diagenesis includes compaction,cementation,dissolution,replacement and recrystallization.According to the texture;cathodoluminescence characteristics,carbon and oxygen isotopic composition, the contents of the main and trace elements,calcite cement formed in reducing condition during early diagenesis. Precipitation of calcite cement caused the decrease of porosity in sediments.Porosity formed by feldspar and intermediate/basic volcanic rock fragment dissolution makes up about one third of the whole porosity.Most smectite and kaolinite already changed into illite and chlorite,or mixed layered illite/smectite(I/S)and chlorite/smectite(C/S).Most changes of reservoir rocks occurred during early diagenesis.