苏里格气田Z30区块下石盒子组8段储层成岩演化与成岩相

Diagenetic evolution and facies of reservoirs in Member 8 of Permian Xiashihezi Formation in the Z30 block of Sulige gasfield

通过镜下、成岩流体包裹体以及酸、碱性流体介质中各种成岩反应热力学特征的分析,结合有机质演化史、埋藏史,对苏里格气田Z30区块二叠系下石盒子组8段(简称盒8段)储层的成岩演化和成岩相进行了划分。结果表明,盒8段储层经历了同生成岩—早成岩A早期的弱酸性溶蚀阶段、早成岩A晚期—早成岩B期的酸性溶蚀阶段、中成岩A期—中成岩B早期的酸性溶解阶段以及中成岩B晚期—地层抬升过程中成岩后生的碱性交代和胶结4个成岩演化阶段,最终形成5种成岩相类型,即净砂岩不稳定组分溶蚀—绿泥石薄膜相、净砂岩不稳定组分溶蚀—高岭石及硅质胶结相、净砂岩高岭石及硅质胶结—不稳定组分溶蚀相、净砂岩不稳定组分溶蚀—碳酸盐致密胶结相以及杂砂岩杂基充填致密压实相。其中,酸性溶解阶段是形成储层主要储集空间的关键性阶段,并使净砂岩不稳定组分溶蚀—绿泥石薄膜相、净砂岩不稳定组分溶蚀—高岭石及硅质胶结相和净砂岩高岭石及硅质胶结—不稳定组分溶蚀相成为建设性成岩相。

Based on microscopic observations, fluid inclusions and thermodynamic analyses of various diagenetic reactions in acidic and alkaline fluid media, and combined with evolutionary history of organic matter and burial history, diagenetic evolution and fa- cies of reservoirs in Member 8 of Xiashihezi Formation in the Z30 block of Sulige Gasfield were classified. The result showed that the Member 8 of Xiashihezi Formation reservoirs experienced at least four evolutionary stages of diagenesis, namely the syndiage- netie to early Period A of Early Diagenesis weak-acid corrosion stage, the late Period A to Period B of Early Diagenesis acid cor- rosion stage, the Period A to early Period B of Middle Diagenesis acid dissolution stage, and finally the late Period B of Middle Diagenesis to epigenetic alkaline metasomatism and cementation stage. The epigenetic stage emerged during the uplift of the study area. After the diagenetic evolution, five types of diagenetic facies were formed in this area, i. e, unstable component dissolution chlorite film facies of arenite, unstable component dissolution kaolinite and siliceous cementation facies of are nite, kaolinite and siliceous cementation unstable component dissolution facies of arenite, unstable component dissolution carbonate dense cementation facies of arenite, and miscellaneous matrix-filled dense compaction facies of greywacke. The acid dissolution stage is a critical period for the formation of main reservoir space, which makes the unstable component dissolu- tion-chlorite film facies of arenite, the unstable component dissolution kaolinite and siliceous cementation facies of arenite and the kaolinite and siliceous cementation unstable component dissolution facies of arenite as the constructive diagentic facies of reservoirs.