Dissipation Rates of Osmotic Pressures in Geologic Membrane Systems

通过粘土和页岩的渗透流可以在地下造成异常的静水压力。在过去的15年里，对粘土膜进行的实验表明，像粘土这样的膜功能材料的过电选择性足够高，可以在地下产生可观的渗透诱导静水压力。然而，要解决的问题是，渗透产生的压力是否可持续，以解释长期现象，如自流条件和逆冲断层。通过测量粘土膜的3个现象学系数，可以测试渗透压力的消散。其中，溶质渗透系数(w)是决定渗透细胞下降速率的最重要因素。到目前为止，还没有深沉积盆地中类似于含水层物质的低孔隙度粘土膜系统的数据。本研究建议测量渗透产生的静水压力在不同孔隙度的膨润土膜上消散的速率。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耗散非常缓慢，那么这应该导致重新评估导致地下异常静水压力的机制，特别是对于深沉积盆地。

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.