Hydrodynamics of Overpressuring in the Sacramento Valley, California

加利福尼亚州萨克拉门托谷超压的流体动力学

• 批准号: 9526951
• 负责人: Grant Garven
• 金额: $ 10万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-04-15 至 1998-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9526951&HistoricalAwards=false
• 关键词: Hydrodynamics; Overpressuring; Sacramento; Valley; California

9526951 Garven Regional overpressuring is a phenomenon characteristic of the Sacramento Valley and the Coast Ranges of California. The creation and maintenance of high fluid pressures in any sedimentary sequence require two basic conditions: (1) low-permeability confining units and (2) geologic forces which increase the pore pressure within these rocks. The forces may be tectonic, thermal, or even chemical in nature. The intent of this study is to determine which factors play a role in the creation of overpressure zones in the Central Valley of California and to quantify the contribution of each in order to successfully model the high pressures currently found in the region. Sedimentary basins in the Great or Central Valley of California host regional aquifers and at greater depths host large petroleum reservoirs. Geological and geochemical data are abundant, as the Valley has been extensively explored and mapped for these natural resources. The Sacramento Basin in the north is rich in natural gas and geothermal resources, and deep groundwater (depths greater than 700 m) is noticeably overpressured in the western part of the basin near the Coast Ranges. Despite the long history of geologic exploration, very little hydrogeologic work has been done to quantify the nature of deep groundwater flow of geologic processes such as overpressuring in the Great Valley. This proposal seeks to increase our basic understanding of how the deep groundwater flow systems have evolved over geologic time in the Sacramento Basin. Earlier studies on the Sacramento Basin suggest that the origin of anomalously high fluid pressures is related to tectonic compression. According to the conceptual model of Berry (1973), east-west compression associated with the San Andreas Fault and the Basin and Range province "squeezed" the Great Valley sediments like a tectonic vise, driving deep pore waters upward. These forces generated high pressure zones due to the low permeability of the thick marine mudstone sectio n. However, other mechanisms for overpressuring may be important. Petroleum generation, dehydration reactions, crustal heating, and rapid subsidence are other mechanisms that need to be considered and quantified hydrodynamically. A primary objective of this proposal therefore is to use hydrogeologic modeling as a tool for quantifying the relationship between the deep ad shallow flow systems in the Valley and test the viability of conceptual models for overprssuring . Various types of field observations will be used to place constraints on the hydrogeologic models, but mostly we will compile pressure data from deep exploration wells. The work proposed here represents the first effort to quantify "deep" groundwater flow dynamics in the Great Valley of California. Hydrologic testing of geologic concepts with coupled mathematical models form the heart of the study: hydromechanical model of the Sacramento Basin ought to shed basic light on other causes for for the origin of overpressures I the Earth's crust. Furthermore, water resources are precious in the Valley which contains one of the largest fresh-water aquifer systems in the world. Improving our understanding of the basin groundwater systems may have significant practical benefit with regard to understanding of the potential salinity contamination of the shallow, fresh-water aquifers as development continues to satisfy an over increasing demand for potable water.

小行星9526951 区域超压是萨克拉门托山谷和加州海岸山脉的一种特征现象。 在任何沉积层序中，高流体压力的产生和维持需要两个基本条件：（1）低渗透性封闭单元和（2）增加这些岩石内部孔隙压力的地质力。 这些力可能是构造力、热力甚至是化学力。 本研究的目的是确定哪些因素在加州的中央谷超压区的形成中起作用，并量化每个因素的贡献，以便成功地模拟该地区目前发现的高压。 加州大峡谷或中央谷的沉积盆地蕴藏着区域含水层，并且在更深的地方蕴藏着大型石油储层。 地质和地球化学数据十分丰富，因为对河谷的这些自然资源进行了广泛的勘探和测绘。 北部的萨克拉门托盆地有丰富的天然气和地热资源，盆地西部靠近海岸山脉的深层地下水（深度大于700米）明显超压。 尽管地质勘探历史悠久，但很少有水文地质工作量化地质过程（如大峡谷超压）的深层地下水流的性质。 该提案旨在增加我们对萨克拉门托盆地深层地下水流系统在地质时期如何演变的基本了解。 早期对萨克拉门托盆地的研究表明，异常高的流体压力的起源与构造挤压有关。根据Berry（1973年）的概念模型，与圣安德烈亚斯断层和盆岭省有关的东西向挤压像构造虎钳一样“挤压”大峡谷沉积物，将深层孔隙沃茨向上推。 由于厚海相泥岩段的低渗透性，这些力产生了高压区。 然而，其他过压机制可能也很重要。 石油生成、脱水反应、地壳加热和快速沉降是其他需要考虑和量化的流体动力学机制。 因此，本提案的一个主要目标是使用水文地质建模作为一种工具，用于量化山谷中的深、浅流系统之间的关系，并测试概念模型的可行性。 将使用各种类型的现场观测对水文地质模型施加约束，但我们主要将汇编来自深勘探威尔斯的压力数据。 这里提出的工作是第一次努力量化“深”地下水流动力学在大峡谷的加州。 水文地质概念与耦合的数学模型的测试形式的研究的心脏：流体力学模型的萨克拉门托盆地应该摆脱其他原因的超压的起源我地壳的基本光。 此外，该山谷的水资源十分宝贵，因为它拥有世界上最大的淡水含水层系统之一。 提高我们对流域地下水系统的理解，可能有显着的实际利益方面的了解潜在的盐度污染的浅，淡水含水层的发展继续满足过度增长的饮用水需求。