塔西南坳陷石炭系碎屑储集岩的成岩演化

Diagenetic evolution of Carboniferous clastic reservoir in the southwest depression of Tarim basin

研究区石炭系碎屑岩储集层的主要成岩作用为机械压实作用、胶结作用、交代作用、溶解作用和破裂作用。机械压实作用和胶结作用对储层物性改善有破坏作用;溶解作用、交代作用、破裂作用在一定程度上有利于改善碎屑储集岩的孔隙结构及储集物性。研究区碎屑岩储集层处于早成岩阶段B期-晚成岩B期。晚成岩期,烃类从源岩中进入储集层发生石油侵位,改变了岩石的成岩环境。由于烃类的侵位,使石英的次生加大、自生铁白云石的生长受到抑制,同时也对自生伊利石生长有抑制作用,黄铁矿由于烃类侵位分布在油层、油水层,尤其在油水层中较为发育。

The Southwest depression is a secondary structure in the Tarim basin, with an area of 1.225×10~5 square kilometers, and the main reservoir and production layer within Permo-Carboniferous strata. The major diagenesis of Carboniferous clastic rocks is mechanical compaction, cementation, replacement, dissolution and fracturing. Compaction and cementation resulted in poor reserveoir properties,but dissolution, particularly dissolution during deep burial, improved reservoir properties of clastic reservoirs. Crevice caused by fracturing lead to physical property better in reservoir to a certain extent.The diagenetic stage of clastic reservoir rocks in Southwest Tarim basin was in between the early diagenetic stage B to later diagenetic stage B. During late diagenesis, the influence caused by oil emplacement on the reservoir changed the wettability of rocks and diagenetic environment. For example, the secondary overgrowth quartz, authigenic illite, and authigenic ankerite on the cementation was inhibited by oil emplacement, but pyrite was mainly distributed in oil layer and oil-water layer, particularly rich in oil-water layer.