鄂尔多斯盆地晚三叠世延长期Cl- 演化机制分析及意义

Cl^- 是鄂尔多斯盆地上三叠统延长组地层水中最主要的阴离子，是决定地层水类型、总矿化度和盐度的最重要指标。古盐度对油气生成和保存均具有重要影响，复原古盐度是恢复古环境、重建古地理和评价含油气系统的重要内容。系统论述了延长组各油层组Cl^- 浓度和总矿化度的分布特征，借鉴了现代湖泊环境研究的最新成果，并从湖盆演化、沉积相、古气候和古海水间歇性注入等方面对Cl^- 的演化机制进行了探讨。研究认为：水循环作用及强度是控制Cl^- 浓度和总矿化度的主导因素；湖盆演化形成的不同水文地质环境和沉积相是控制Cl^- 浓度和总矿化度的重要因素；古气候和古海水间歇性注入可能对Cl^- 浓度和总矿化度具有一定的控制作用。现今地层水的类型和总矿化度对油层的准确发现、判识和评价均具有重要意义。

Cl-evolution mechanism of Yanchang stage of Late Triassic in Ordos Basin and its significance

C1- is the most important anion in the formation water chemical composition of the Upper Triassic Yanchang Formation in Ordos Basin, and it is the most important index to decide the formation water type, total salinity and salinity. Paleosalinity has important influence on oil and gas generation and preservation, the restoration of paleosalinity is important for the reconstruction of paleoenvironment and paleogeography and assessment of petroleum system. This paper analyzed the distribution characteristics of C1- concentration and total salinity of the reservoir of Yanchang Formation, drew on the latest research achievements of modern lake environment, and studied the C1- evolution mechanism from the aspects of basin evolution, sedimentary facies, paleoclimate and ancient seawater intermittent injection. The result shows that the intensity of water circulation is the dominant controlling factor for C1- concentration and total salinity, sedimentary facies and different hydrogeological environment formed by lake basin evolution are important factors for controlling C1- concentration and total salinity, and paleoclimate and ancient seawater intermittentinjection may have certain control effect on C1- concentration and total salinity. The formation water types and total salinity have important significance for the found, identification and evaluation of reservoir.