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基于大量物性数据和沉积构造背景,利用铸体薄片、有机地球化学和流体包裹体技术,研究了控制琼东南盆地西部崖城区储层异常高孔带发育的成岩作用.认为崖城区三段异常高孔带的成因不同,控制其发育的主要成岩作用分别为有机酸溶蚀与大气淡水淋滤作用,热流体溶蚀作用和有机质生成天然气引起的超压保持作用.研究结果表明:崖城区共发育3段异常高孔带,分布于2 400~3 100m,3 600~4 100m和4 500~4 800m.第1段异常高孔带属于有机酸和大气淡水混合溶蚀型,即有机质早期大量释放的有机酸和大气淡水共同溶解了长石、碳酸盐胶结物等产生次生孔,早期绿泥石包壳未起有效作用.第2段异常高孔带属于热流溶蚀型,热流体使烃源岩加快熟化从而延长有机酸的产出期,而且促使蒙脱石迅速转化为伊利石从而释放更多的H~+;深部流体携带大量酸性组分且具有较强的流体性,可以对储层产生淋滤,也加快了Al~(3+)的迁移;更高的温压可以促进溶蚀反应的发生,提高溶解度.第3段异常高孔带属于超压保持性型,强超压有效抑制了压实作用和自生矿物发育,保持了孔隙度.超压体系向上集中排放形成热流体使得该段超压储层硅质流失,致使自生石英未规模发育.伊蒙转化反应被提前而且超压对该反应也有抑制作用,使得自生伊利石未大量形成.该区天然气充注期为晚期,烃类侵位未能抑制石英等自生矿物的生长,但盆地晚期快速沉降使得源岩大量生成天然气促使超压形成,间接贡献了第3段异常高孔带的发育.
Based on a large amount of physical data and sedimentary tectonic setting, the diagenesis controlling the development of abnormal high-porosity zones in the Yacheng reservoir in western Qiongdongnan Basin was studied by using the techniques of thin castings, organic geochemistry and fluid inclusions. The major diagenesis that controlled the development of pore zone is organic acid dissolution and leaching of atmospheric freshwater, erosion of thermal fluid and maintenance of overpressure caused by organic matter generated by natural gas.The results show that there are altogether 3 sections Abnormally high zone of pore distribution, distributed in 2400 ~ 3 100m, 3 600 ~ 4 100m and 4 500 ~ 4 800m. The first paragraph of the abnormal high porosity zone belongs to organic acid and atmospheric freshwater mixed dissolution type, that organic matter mass early release of organic acids Together with the atmospheric freshwater, feldspar and carbonate cements produced secondary pores and the early chlorite crust did not work effectively. The second high-porosity zone belonged to the thermal-fluid erosion type, and the thermal fluid accelerated the source rock Maturation to extend the organic acid production period, but also prompted the rapid conversion of montmorillonite to illite to release more H ~ +; deep fluid carrying a large number of acidic components and has strong fluidity, you can The leaching of the reservoir also accelerates the migration of Al ~ (3 +), and the higher temperature and pressure can promote the dissolution reaction and increase the solubility.The abnormal high porosity zone in the third stage belongs to the overpressure-holding type, Effectively inhibit the compaction and authigenic mineral development and maintain the porosity.The overpressure system concentrated upward emission of hot fluid makes the overpressured reservoir siliceous loss, resulting in the development of self-generated quartz un-scale.Emonton reaction was advanced and Overpressure also inhibited the reaction, making the self-generated illite is not formed in large quantities.The gas filling period of this area is late, hydrocarbon emplacement can not restrain the growth of quartz and other authigenic minerals, but the late rapid sedimentation in the basin resulted in the massive formation of source rocks Natural gas prompted the formation of overpressure, indirectly contributed to the third paragraph of abnormal high porosity zone development.