碳酸盐胶结物溶解—沉淀的热力学平衡在碎屑岩储层质量预测中的应用——以渤南洼陷沙三段为例

Application of thermodynamic equilibrium for dissolution-precipitation of carbonate cements in prediction of clastic reservoir quality:A case study from Es_3,Bonan sag

碳酸盐胶结物对碎屑岩储层质量具有较大影响。根据渤南洼陷沙三段47口井的地层水化学数据,采用化学热力学方法,结合沉积相分布、薄片观察和孔隙度等资料,预测有利储层发育带。结果表明:现今地层水多为NaHCO3型,有利于碳酸盐矿物的沉淀(吉布斯自由能ΔG>0kJ/mol),CaCl2型水相对有利于碳酸盐矿物的溶解。碳酸盐矿物的含量与孔隙度在纵向和平面上有较好的对应关系。研究区吉布斯自由能较小的区域主要在三角洲沉积相,该区域碳酸盐含量较低,孔隙度发育较好,是有利储层的发育区。因此,碳酸盐胶结物对研究区碎屑岩储层质量起决定性影响,通过对碳酸盐矿物的溶解—沉淀热力学平衡计算,可作为一种新的储层预测方法。

The carbonate cements have great impact on the quality of clastic reservoirs.In this paper,by means of using the chemical datas of the formation water of 47 wells in the three sections of the Bonan sag,the factors affecting the dissolution of carbonate minerals in the three sections of the sand are analyzed by means of chemical thermodynamic calculation,combined with the data of sedimentary facies distribution,thin sections observation and porosity materials,predicated the zone of the favorable reservoir development.The results show that most of the current formation water is NaHCO 3 type,which is most conducive to the precipitation of carbonate minerals(ΔG>0 kJ/mol),and CaCl 2 type water is relatively favorable for the dissolution of carbonate minerals.And the corresponding relationship between the content of carbonate minerals and the porosity in the vertical and the plane.The lower area ofΔG in the study area is mainly in the delta sedimentary facies,and the carbonate content in this area is low and porosity is high,which is a favorable reservoir development area.Therefore,carbonate cements has a decisive impact on the quality of the clastic reservoir in the study area,the thermodynamic calculation of dissolution and precipitation of carbonate minerals can be used as a new reservoir prediction tool.