Study of Modern Gravelly Braided River Deposits with Special Reference to Spatial Variations in Porosity and Permeability

9902894Bridge 将研究砾石辫状河沉积物的性质和起源，特别强调孔隙度和渗透率的空间变化。将使用与沟渠、岩心和测井记录紧密相连的探地雷达剖面图对河道带沉积物进行 3D 研究。这项研究的一个创新之处在于，在某些采样过程中（位于阿拉斯加北坡）河流和沉积物将被冻结，从而最大限度地减少取芯过程中的干扰，并能够轻松进入河道带的所有部分。该采样策略将允许描述不同类型和规模的分层、粒度分布、孔隙度和渗透率以及矿床的相关地球物理特性的 3D 变化。将特别关注高渗透性（开放框架砾石）和低渗透性（泥浆）区域。将尝试使用以下方法来解释这些沉积模式：（1）从连续航空照片中获得的河道切割、迁移和充填模式的知识；以及； (2)重大侵蚀沉积事件期间河床的几何形状、沉积物结构和河床形态的推断。最终目标是为砾石辫状河构建详细的 3D 沉积模型，该模型是对现有模型的重大改进，特别是在描述大规模分层模式方面。此外，与沉积相相关的孔隙度和渗透率预测对于模拟通过类似古代沉积物中的含水层和油气藏的流体流动也很重要。然而，严重缺乏来自砾石辫状河的孔隙数据来支持这种建模。试点研究结果表明，该项目的目标是可以实现的。

9902894BridgeThe nature and origin of gravelly braided-river deposits will be studied, with specific emphasis on spatial variations in porosity and permeability. Channel-belt deposits will be studied in 3-D using closely spaced ground-penetrating radar profiles tied to trenches, cores and wireline logs. An innovative aspect of this study is that the river and sediment will be frozen during some of the sampling (being on the North Slope of Alaska), thus minimizing disturbance during coring, and enabling easy access to all parts of the channel belt. This sampling strategy will allow description of the 3-D variation of the different types and scales of stratification, grain-size distributions, porosity and permeability, and related geophysical properties of the deposits. Particular attention will be paid to zones of high permeability (open-framework gravels) and low permeability (muds). Interpretation of these patterns of deposition will be attempted using: (1) knowledge of the mode of channel cutting, migration and filling, obtainable from sequential aerial photographs, and; (2) inferences about the geometry, sediment textures and bed forms of the channel bed during major erosional-depositional events. An ultimate objective is construction of a detailed, 3-D depositional model for gravelly braided rivers that is a major improvement over existing models, particularly in the description of the large-scale stratification patterns. Also, prediction of porosity and permeability in relation to sedimentary facies is important for modeling of fluid flow through aquifers and hydrocarbon reservoirs in analogous ancient deposits. However, there is a critical lack of poroperm data from gravelly braided rivers to support such modeling. The results of a pilot study indicate that the objectives of this project can be realized.