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州墨西哥湾沿岸盆地卤水的成因和运移历史。该盆地由从侏罗纪到现代的一系列沉积层组成。总体上，该盆地存在三种不同的流态，即浅层淡水系统和两个较深的系统，一个是水压系统，一个是地压系统，其特征是流体具有较高的溶质浓度。尽管对该盆地沉积建造的沉积层序有较好的认识，但卤水与其寄主建造的关系往往不清楚。碘的地球化学性质和129I的半衰期(15.7 Ma)使该同位素体系有可能用于确定该盆地流体和有机质的来源年龄，并结合36Cl的测定，估计水在各自的寄主地层中的滞留时间。这项研究的结果将提供流体与其主岩之间的年龄关系、盆地不同部分流体之间的关系以及不同储集层之间的沟通信息。由于碘的存在与有机物质的存在有关，这一结果将为该盆地碳氢化合物的来源和年龄关系提供信息。由于该项目是该同位素系统首次在沉积盆地的区域范围内使用，因此这项研究还将表明129I系统在多大程度上有助于研究含有机物质盆地中的流体运动。这对于认识盆地演化、油气赋存和沉积成矿具有很强的意义。

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.//