Experimental Study of Formation of Open-framework Gravels

0304426桥梁对单向水流形成开放骨架砾石进行了实验研究。开放框架砾石在砾石颗粒之间的空隙中含有很少的沙子和泥浆，这是因为它们具有极高的渗透性。它们在砾石河流储集层中很常见，形成了如此多的重要碳氢化合物储集层和含水层。在碳水化合物储集层中，开放骨架砾石在注水和混相注气过程中起到“小偷带”的作用。在许多冰川含水层中，敞开的框架槽允许地下水污染物的快速、局部扩散。河流中的开阔框架沟壑也是鲑鱼的主要产卵地点。因此，重要的是：0了解开放框架砾石的来源、几何形状和空间分布)，以便：(1)设计石油开采项目；(2)模拟污染物在马里兰州含水层中的扩散；(3)评估人类活动对鲑鱼产卵的影响。然而，对开放格架砾石的成因了解甚少，也很难理解和判断它们在河流沉积中的位置。此外，空腹砾石的渗透性很难准确定义。实验将被用来验证以下假设：(1)开式砾石形成于相对较低的位置；通过优先夹带和泥沙分离，无基质砾石作为推移质床层输送，并沉积在沙丘和单元沙洲的背风侧；(2)在稳定流动条件下不能形成厚而广泛的开式砾石沟，但需要流量的反复波动；(3)低流量阶段沙粒向开式砾石的渗透是形成相关双峰砂砾石的重要过程。这些实验还将允许比目前更准确地测量开放框架砾石的渗透率，以及预测孔隙度的地球物理技术的测试。实验室实验(将被录像)将是学生无价的学习工具。研究结果将在水文地质学、水库工程和淡水鱼生态学等领域产生重大的实际影响。

0304426BridgeAn experimental investigation of the formation of open- framework gravels by midirectional water flows is proposed. Open-framework gravels have very small Imounts of sand and mud in the spaces between the gravel grains, and are significant Jecause of their exceptionally high permeability. They are common in the gravelly river ieposits that form so many important hydrocarbon reservoirs and aquifers. In lydrocarbon reservoirs, open-framework gravels act as "thief zones" during water- Gooding and miscible-gas injection. In many glaciofluvial aquifers, open-framework ~avels allow rapid, localized dispersion of groundwater contaminants. Open-framework ~ravels in rivers are also prime spawning sites for salmonid fish. It is therefore important :0 understand the origin, geometry and spatial distribution of open-framework gravels in )rder to: (1) design oil recovery projects; (2) model contaminant dispersion in aquifers, md; (3) assess the impact of human activities on salmonid spawning. However, the origin n open-framework gravels is poorly understood, and it is difficult to understand and Jredict where they occur in fluvial deposits. Furthermore, the permeability of open- rramework gravel is very difficult to define accurately. The experiments will be used to :est the hypotheses that: (1) open-framework gravels are formed at relatively low ;ediment-transport stage (rather than at high stage) by preferential entrainment and ;eparation of sand and silt, transport of matrix-free gravel as bedload sheets, and ieposition on the lee-side of dunes and unit bars; (2) thick, extensive open-framework ~ravels cannot be formed under steady flow conditions, but require repeated fluctuations in discharge, and; (3) infiltration of sand into open-framework gravel at low flow stage is lot a significant process in forming associated bimodal sandy gravel. The experiments will also allow the permeability of open-framework gravels to be measured much more lccurately than possible up to now, and testing of geophysical techniques that predict ;ediment porosity. The laboratory experiments (which will be videotaped) will be an invaluable learning tool for students. The results will have a major practical impact in the lfeas of hydrogeology, reservoir engineering, and freshwater fish ecology.