Hydrodynamic and Geochemical Interactions Between Formation Waters of Varying Salinity

不同盐度地层水之间的水动力和地球化学相互作用

• 批准号: 0537555
• 负责人: Jeffrey Nunn
• 金额: --
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-01 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0537555&HistoricalAwards=false
• 关键词: Hydrodynamic; Geochemical; Interactions; Between; Formation

Pore fluids in the subsurface range in salinity from meteoric (0 g/l) to hypersaline brines ( 300 g/l), while temperature and pressure affect the density and viscosity of these pore waters. Spatial variations in pore fluid density may drive or inhibit pore fluid motion. Pore fluids of different salinities may physically and/or chemically interact when they are brought into close proximity. This may occur as: 1) meteoric water moves through a basin driven by topographic recharge (e.g., North Slope of Alaska); 2) dissolution of salt and subsequent buoyancy drive flow around salt structures (e.g., Marchand Dome or Bullwinkle field, offshore Gulf of Mexico); and 3) episodic expulsion of geopressured fluids along faults or fracture networks (e.g., Wilcox formation, onshore Louisiana or Eugene Island, offshore Gulf of Mexico). Previous studies have made simplifying assumptions, such as ignoring pressure and buoyancy driven flow or the effect of salinity on pore fluid density or viscosity. We propose to address fundamental questions as to how pore fluids of variable salinity interact when both pressure and density, as well as how concurrent fluid-rock chemical interactions affect the transport properties of the porous medium. Toward this end, we have acquired data sets on the structure, stratigraphy and physical/chemical properties of sediments and formation waters in south Louisiana and the North Slope foreland basin. This project is a three-year study on the following aspects of fluid flow, mass transport and reaction in the North Slope of Alaska and Gulf of Mexico: (1) a determination of spatial variations in formation water and sediment properties, solute transport pathways and water-sediment chemical reactions using wireline logs, seismic data, formation water and sediment samples; and (2) a study of coupled density-driven and pressure-driven fluid flow and associated heat and solute transport. Data will be used to test our hypotheses as well as assess the validity of simplifying assumptions made in previous mathematical and numerical solutions of variable-density fluid flow. We will study two specific examples: 1) meteoric recharge as it moves through a basin interacting with brine at depth or brine above a dissolving salt structure; and 2) a brine plume moving down dip from a dissolving salt structure interacting with fresher formation waters being expulsed from a geopressured zone. In both cases we wish to know whether fresh water will physically mix with the brine, displace the brine, or ride over the brine, and what factors control that response. Understanding how fluids of variable salinity interact in the subsurface has important implications for coastal aquifers, groundwater resources, oil exploration, aquifer remediation, CO2 sequestration, and hazardous waste disposal. Deeply buried hypersaline brine might be a repository for hazardous material if brines are truly immobile. Alternatively, spatial variations in pore water salinity might induce density driven fluid flow or indicate migration pathways or spill points in a proposed CO2 sequestration site, an oil field, or a salt water intrusion remediation project. This project provides general service to the science community by development of several data sets and enhancement of existing variable density fluid flow simulation codes.

地下孔隙流体的盐度范围从大气降水（0 g/l）到高盐卤水（300 g/l），而温度和压力影响这些孔隙沃茨的密度和粘度。 孔隙流体密度的空间变化可以驱动或抑制孔隙流体运动。 不同盐度的孔隙流体在它们紧密接近时可能发生物理和/或化学相互作用。 这可能发生在：1）大气降水通过地形补给驱动的盆地移动（例如，阿拉斯加北坡）; 2）盐的溶解和随后的浮力驱动盐结构周围的流动（例如，Marchand Dome或Bullwinkle油田，墨西哥湾近海）;以及3）沿着断层或裂缝网络（例如，威尔科克斯地层，路易斯安那陆上或尤金岛，墨西哥湾近海）。 以往的研究都做了简化的假设，如忽略压力和浮力驱动的流动或盐度对孔隙流体密度或粘度的影响。 我们建议解决的基本问题，如何可变盐度的孔隙流体相互作用时，压力和密度，以及如何并发流体-岩石化学相互作用影响的多孔介质的传输特性。为此，我们已经获得了路易斯安那州南部和北坡前陆盆地的沉积物和地层沃茨的结构，地层和物理/化学性质的数据集。该项目是一项为期三年的研究，主要研究阿拉斯加北坡和墨西哥湾的流体流动、物质输运和反应：（1）利用电缆测井、地震数据、地层水和沉积物样品确定地层水和沉积物性质的空间变化、溶质输运途径和水-沉积物化学反应;以及（2）耦合的密度驱动和压力驱动的流体流动以及相关的热量和溶质输运的研究。 数据将被用来测试我们的假设，以及评估的有效性简化假设在以前的数学和数值解的变密度流体流动。我们将研究两个具体的例子：1）流星补给，因为它通过一个盆地移动与盐水在深度或盐水以上的溶解盐结构相互作用;和2）盐水羽流向下倾斜移动从溶解盐结构与新鲜的地层沃茨被驱逐从一个超压区。在这两种情况下，我们都希望知道淡水是否会与盐水物理混合，取代盐水，或骑在盐水上，以及什么因素控制这种反应。 了解不同盐度的流体如何在地下相互作用对沿海含水层、地下水资源、石油勘探、含水层修复、CO2封存和危险废物处置具有重要意义。 如果盐水真的不流动，深埋的高盐度盐水可能是危险物质的储存库。 或者，孔隙水盐度的空间变化可能会引起密度驱动的流体流动或指示迁移路径或溢出点在一个拟议的CO2封存网站，油田，或盐水入侵修复项目。 该项目通过开发若干数据集和增强现有的变密度流体流动模拟代码，为科学界提供一般服务。