Dissipation Rates of Osmotic Pressures in Geologic Membrane Systems

地质膜系统中渗透压的耗散率

• 批准号: 8803738
• 负责人: Steven Fritz
• 金额: $ 13.72万
• 依托单位: Purdue Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-07-01 至 1991-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8803738&HistoricalAwards=false
• 关键词: Dissipation; Rates; Osmotic; Pressures; Geologic

Osmotic flow through clays and shales can result in anomalous hydrostatic pressures in the subsurface. Within the past 15 years, experiments conducted on clay membranes have shown that the permselectivity of membrane-functioning materials like clay is sufficiently high to generate appreciable osmotically-induced hydrostatic pressure in the subsurface. Yet to be resolved is whether osmotic-generated pressures are sustainable to explain long-term phenomena like artesian conditions and thrust faulting. Dissipation of osmotic pressure can be tested by measuring 3 phenomenological coefficients of the clay membrane. Of these, the solute permeability coefficient (w) is the most important in determining the rate at which an osmotic cell runs down. To date, there exists no data for (w) inn clay membrane systems having low porosities akin to aquitard materials in deep sedimentary basins. This study proposes to measure the rates at which osmotically-generated hydrostatic pressures are dissipated across bentonite membranes of various porosities. These data, mainly in the form of (w) values, will help resolve the kinetic conundrum of geologic membrane systems. If these data show that osmotic- pressure dissipation is extremely slow, then this should result in a re-evaluation of mechanisms causing anomalous hydrostatic pressures in the subsurface -- particularly for deep sedimentary basins.

粘土和页岩中的渗透流动会在地下产生异常的静水压力。在过去的15年里，在粘土薄膜上进行的实验表明，粘土等膜功能材料的渗透选择性足够高，足以在地下产生可观的渗透诱导静水压力。有待解决的问题是，渗透生成的压力是否可持续，以解释自流条件和逆冲断层等长期现象。通过测量粘土膜的3个唯象系数，可以测试渗透压的耗散。在这些参数中，溶质渗透系数(W)是决定渗透单元衰减率的最重要参数。到目前为止，还没有关于深层沉积盆地中具有类似于含水层材料的低孔隙率的(W)内粘土膜系统的数据。这项研究建议测量渗透产生的静水压力在不同孔隙率的膨润土膜上的消散速度。这些数据，主要以(W)值的形式，将有助于解决地质膜系统的动力学难题。如果这些数据表明渗透压消散非常缓慢，那么这应该会导致重新评估引起地下异常静水压力的机制--特别是对于深层沉积盆地。