储层成岩产物对于油气运移的指示意义——以塔里木盆地群苦恰克构造带东河塘组为例

The significance of diagenetic products for petroleum migration in reservoir:An example from Devonian Donghetang Formation in Qunkuqiake structure zone,Tarim Basin

泥盆系东河塘组下段砂岩储层是塔里木盆地群苦恰克构造带内重要的勘探层系,有关储层内油气充注方向与富集规律的研究目前仍未有统一认识。研究层段内碳酸盐胶结物(主要为白云石和铁白云石胶结物)分布较为广泛,其中作为早成岩阶段产物的白云石胶结物的含量在平面上呈现出自东向西依次增加的趋势;而铁白云石胶结物则以交代先期形成白云石胶结物的形式产出于中成岩阶段,略滞后于储层内的油气充注,其胶结程度在平面上呈现出自东向西依次减弱的分布规律。铁白云石胶结物作为反映储层内较强还原环境的指示性矿物,其在储层内的分布规律也承担着判明油气运移方向或富集规律的"责任",而其上述分布规律为研究区储层内油气自东向西充注提供了全新的判定依据。

The Donghetang Formation is the important exploratory formation in the Qunkuqiake structure zone,Tarim Basin.But no agreement is yet achieved as to the direction of migration and accumulation of petroleum in the reservoir.The dolomite and ankerite cements are extensive in the sandstones.The dolomite cement developed in the sandstones during early diagenetic stage and their content in the sandstones increase respectively from east to west.The formation sequence of ankerite cement was later than that of petroleum migration in the reservoir.They replaced the previous dolomite cement during middle diagenetic stage and their content in the sandstones increase respectively from west to east that is contrary to that of dolomite cement.Ankerite cement is thought as an indicative mineral for the strong reduction environment in sandstone.The accumulation of ankerite cement in sandstones reveals the rules of migration and accumulation of petroleum in reservoir.The result of the study provides new evidences for the westward direction of petroleum migration in the reservoir.