鄂尔多斯盆地陕北地区上三叠统延长组长6油层组的成岩相与储层分布

Diagenetic facies and distribution of the Chang 6 reservoir group of the Upper Triassic Yanchang Formation in the northern Shaanxi area,Ordos basin,China.

利用室内铸体薄片鉴定、扫描电镜、X-射线衍射、图像粒度、压汞分析等现代测试技术和数理统计、储层综合评价方法研究了陕北延长组长6油层组成岩相与储层分布的关系。研究结果表明,压实作用和胶结作用分别造成砂岩中24.9%和12.0%的原生孔隙丧失,溶解作用使孔隙间的连通性得到改善、渗透性提高。沉积相、埋藏条件和碎屑成分的不同导致地区之间成岩作用的差异。可划分出5种成岩相带:浊沸石胶结溶蚀相是储层发育的最有利区,绿泥石薄膜胶结粒间孔相是次有利成岩相带,碳酸盐+自生粘土充填微孔相在一定条件下可形成良好的储层,压实压溶致密相和浊沸石/碳酸盐胶结致密相不利于储层的发育。

The relationship between the diagenetic facies and distribution of the Chang 6 reservoir group of the Yanchang Formation in northern Shaanxi was studied using various modem analytic techniques such as identification of blue epoxy resin-impregnated thin sections, electron scanning microscope （ESM）, X-ray diffraction （XRD）, image grain size and capillary pressure analysis, mathematical statistics and reservoir comprehensive evaluation. The research results indicate that compaction and cementation caused the loss of 24.9% and 12.0% primary pores in sandstones respectively and that dissolution improved the connectivity between the pores and enhanced permeability. The difference between sedimentary facies, burial conditions and detrital composition caused difference in diagenesis between areas. Five diagenetic facies zones may be recognized： the humentite cementation-dissolution diagenetic fades zone, which is the most favorable area for the development of reservoirs; the chlorite membranous cementation-intergranular pore diagenetic facies zone, which is the second favorable diagenetic facies zone, and authigenic kaolinite ＋ carbonate filling micropore diagenetic fa- cies can act as a favorable reservoir under certain conditions; and the compaction and pressure solution dense diagenetic facies and humentite or carbonate cementation dense diagenetic facies are disadvantageous to the development of reservoirs.