通过野外地质调查及钻井资料复查,探明了雷口坡组及嘉陵江组顶、底界面特征。根据岩性组合、电性特征、旋回特征及地层厚度特征,对南充盐盆雷口坡组及嘉陵江组地层进行对比分析。在此基础上,对南充盐盆嘉陵江组及雷口坡组地层进行了重新梳理,得到南充盐盆盐岩层位的空间展布,及3个主要成盐段:嘉四段、嘉五2—雷一1亚段和雷三2亚段。通过大量单井分析,统计各成盐段石盐岩的单层厚度,结合各段岩性组合特征及放射性测井分析各成盐段的成钾条件;绘制各段石盐岩等厚图,得出各段盐岩分布范围及成盐中心,从而确定有利的成钾区。在广安构造的雷三2亚段,首次发现了杂卤石,否定了以往认为的雷三2亚段原始沉积石盐岩的海水中钾含量异常偏低的推测。
Based on a review of the geological survey and drilling data, the authors investigated the top and bottom interface features of the Middle Triassic Leikoupo Formation and the Lower Triassic Jialingjiang Formation in the Nanchong Salt Basin. A comparative analysis was also made for these two formations according to their lithologic compositions, electrical characteristics, cycle characteristics and stratigraphic thicknesss with the purpose of restudying these two formations. Through the study, the spatial distribution of these two formations in the Nanchong Salt Basin and the major salt segments T1j4, T1j5-2-T2 l1-1, T2 l3-2 were determined. Based on a large number of single well analyses and statistics of salt rock thickness in each formation in combination with the lithologic composition characteristics and radioactive logging display characteristics, the authors analyzed the potash layer formation conditions. With the isopach map of potash layer, the potash distribution in each formation and the potash center as well as the favorable potash zones can be seen. The first discovery of polyhalite in T2 l3-2 in the Guang' an structure excludes the previous opinion that the potash content was abnormally low in the seawater where the original salt rock was deposited.