莺歌海盆地东方区黄流组一段储层成岩作用机理及孔隙演化

Diagenesis Mechanism and Porosity Evolution of the First Member of Huangliu Formation Reservoirs in Dongfang Area,Yinggehai Basin

根据化学热力学和流体动力学，探讨了莺歌海盆地东方区黄流组一段储层成岩机理、成岩模式及孔隙演化。研究表明：（1）成岩阶段参与反应的矿物主要有长石、高岭石、伊蒙混层、伊利石、石英以及少量的碳酸盐胶结物，来自于下伏地层的有机酸、高温热流体及超压为矿物反应提供了高温高压的酸性流体环境。（2）同生一早成岩A期，系统开放，地层温度在70℃以下，高岭石、蒙皂石伊利石化，驱使不稳定的斜长石大量溶蚀，钾长石得以保存，石英部分加大，局部碳酸盐沉淀，孔隙演化趋势为先减少后稳定。早成岩B期一中成岩A期，系统半封闭，地层温度70～140℃，高温高压的酸性环境下钾长石大量溶蚀，并驱使蒙皂石继续向伊利石转化，钠长石大量保存，SiO2沉淀，孔隙演化趋势呈稳定的减少态势；中成岩B期以后，系统封闭，地层温度约140℃，高岭石和钾长石直接反应，生成伊利石，钾长石基本消耗殆尽，高岭石与伊利石共存，大量钠长石剩余，部分石英加大边呈港湾状溶蚀，孔隙演化曲线出现局部回春。

This paper discusses diagenesis mechanism, diagenesis model and porosity evolution of the first member of Huangliu Formation reservoirs in Dongfang area, Yinggehai Basin based on chemical thermody- namics and hydrodynamics. The results show that the minerals participating in reaction were feldspar, ka- olinite, illite smectite mixed layer, illite, quartz and a few carbonate cements of diagenesis stage. Organic acid, high temperature thermal fluid and over-pressure from underlying formation supplied acid fluid envi- ronment of high temperature and high pressure for mineral reaction. From syngenetic period to the early A stage of diagenesis, when the system was open, the temperature of stratum was below 70~C, the illitiza- tion of kaolinite and smectite impeled largely unstable plagioclase to dissolve and K-feldspar was preserved while part of quartz was expanded and carbonate was deposited locally. Correspondingly, the porosity e- volution tended to reduce before stabilization. From early B stage to middle A stage of diagenesis, when the system was semi-closed, the temperature of stratum was 70-140℃ and K-feldspar was largely dissolved, which impeled smectite to illitize sequentially, while albite was largely preserved and SiO2 was deposited. In coorespondence, the porosity evolution tended to reduce steadily. From middle B stage of diagenesis, when the system was closed, the temperature of stratum was 140℃ ~ and kaolinite and K-feldspar reacted directly to form illite with K-feldspar basically consumed out, but kaolinite and illite coexisted with many remains of albite while part of quartz shows harbor-shape dissolution. Then, the porosity evolution tended to rejuvenize in part of the curve.