结合推拉示踪试验和单孔探地雷达研究裂隙岩体运移过程的水文地球物理特征
Hydrogeophysical characterization of transport processes in fractured rock by combining push-pull tracer tests and single-hole ground penetrating radar
摘要：
由于示踪剂路径和主要控制过程（如分散、沟道、捕获、基质扩散、环境和密度驱动流）具有相当大的空间不确定性，因此裂缝介质中输运过程的原位表征特别具有挑战性。我们试图减少这种不确定性耦合推拉示踪实验单孔探地雷达（GPR）延时成像。实验涉及不同的注入裂缝、驱油体积和静止时间，并且在法国的Ploemeur的裂缝岩石研究现场进行（H+网络，hplus.ore.fr/en）。对于GPR采集，我们在用柔性衬管隔离的钻孔中使用固定和移动天线设置。在固定天线实验中，随时间变化的GPR反射使我们能够跟踪推拉实验中示踪剂的空间和时间动态。在移动天线实验中，我们清楚地成像的主要裂缝中的示踪剂运输发生，裂缝中的示踪剂被困在较长的时间内，和空间范围的示踪剂分布（高达8米）在不同的时间。这表明在最初几米处存在强烈的渠化流，而在更远的距离处存在径向流。通过改变给定实验的休息时间，我们确定了受密度驱动和环境流影响的区域。这些实验开辟了新的视角耦合水文地球物理反演，旨在了解运输现象，在破碎的岩层。
英文摘要：
The in situ characterization of transport processes in fractured media is particularly challenging due to the considerable spatial uncertainty on tracer pathways and dominant controlling processes, such as dispersion, channeling, trapping, matrix diffusion, ambient and density driven flows. We attempted to reduce this uncertainty by coupling push-pull tracer experiments with single-hole ground penetrating radar (GPR) time-lapse imaging. The experiments involved different injection fractures, chaser volumes and resting times, and were performed at the fractured rock research site of Ploemeur in France (H+ network, hplus.ore.fr/en). For the GPR acquisitions, we used both fixed and moving antenna setups in a borehole that was isolated with a flexible liner. During the fixed-antenna experiment, time-varying GPR reflections allowed us to track the spatial and temporal dynamics of the tracer during the push-pull experiment. During the moving antenna experiments, we clearly imaged the dominant fractures in which tracer transport took place, fractures in which the tracer was trapped for longer time periods, and the spatial extent of the tracer distribution (up to 8 m) at different times. This demonstrated the existence of strongly channelized flow in the first few meters and radial flow at greater distances. By varying the resting time of a given experiment, we identified regions affected by density-driven and ambient flow. These experiments open up new perspectives for coupled hydrogeophysical inversion aimed at understanding transport phenomena in fractured rock formations.
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