Investigation of Brine Migration in the Louisiana Gulf Coast

我们将应用11129 I系统研究路易斯安那湾沿岸盆地的盐水起源和迁移历史。该盆地由一系列沉积层组成，年龄从侏罗纪到近代不等。总体而言，该盆地存在三种不同的流动体系，即浅层淡水体系和两种较深的流体体系，一种是水压体系，一种是地压体系，其特征是溶质浓度较高。虽然对该盆地沉积地层的沉积顺序已经很清楚，但对其与寄主地层的关系却往往不太清楚。碘的地球化学特征与129i （15.7 Ma）的半衰期相结合，使该同位素系统可用于确定该盆地流体和有机物的来源年龄，并与36cl的测定相结合，用于估计水在其各自宿主地层中的停留时间。研究结果将为流体与寄主岩的年龄关系、盆地不同部位流体之间的关系以及不同储层之间的连通性提供信息。由于碘的存在与有机质的存在有关，结果将提供有关该盆地碳氢化合物起源和年龄关系的信息。由于该项目是该同位素系统首次在沉积盆地的区域尺度上使用，该研究还将表明129 I系统在多大程度上有助于研究含有机质盆地的流体运动。这对认识盆地演化、油气聚集和沉积矿床的形成具有重要意义

We will apply the 11129 I system to the study of the origin and migration history of brines in the Louisiana Gulf Coast Basin. This basin consists of a sequence of sedimentary layers ranging in age from Jurassic to recent. Generally, there exist three different flow regimes in this basin, a shallow fresh-water system, and two deeper systems, one hydropressured, one geopressured, which are characterized by fluids with higher concentrations of solutes. Although the depositional sequence of the sedimentary formations in this basin is well undeerstood, the relation of the brines to their host formations is often not clear. The geochemical characteristics of iodine combined with the half-life of 129 I (15.7 Ma) make this isotope system potentially useful for the determination of source ages for fluids and orgainic material in this basin and, in conjunction with determination of 36 Cl, for the estimate of residence times of waters in their respective host formaiton. The results of this study will give information on the age relation between the fluids and their host rocks, on the relation between fluids in the different parts of the basin and on communication between different reservoirs. Because the presence of iodine is related to that of organic material the result will given information on the origin and the age relation of hydrocarbons in this basin. Since this project represents the first time that this isotope system is to be used on a regional scale in a sedimentary basin, the study will also indicate to what extent the 129 I system is useful for the investigation of fluid movement in basins containing organic material. This has very strong implication for understanding basin evolution, oil accomulation and formation of sedimentary ores.//