Fluid escape pipe formation in the Levant Basin

该项目包括对黎凡特盆地广泛分布的众多FEPs的研究，因为它为分析FEPs的形成提供了一个很好的自然数据集。盆地地层由c. 2公里厚的不透水岩盐层，覆盖在一个C。3 km厚的泥岩和砂岩层序列（Cartwright等人，2020年）。砂岩单元构成含气储层，泥岩和盐垂向封闭含气储层。Levant FEP从这些砂岩中排出气体（Oppo等人，2020年），因此穿透了数公里的不透水的泥岩和盐。在盆地的东北边缘，三维地震数据显示，在过去的200万年里，管道已经从12个固定位置形成。然而，由于粘性盐的西向流动，现有的管道变形和移位，使得每隔一段时间就必须形成一个新的垂直管道。1万最终的结果是12条管道记录了整个地质时期的每个事件，因为当地的盐地形也使每个事件的相对定年成为可能（Oppo等人，2020，Evans等人，2020).为了了解FEP形成的机制，我需要一个准确的物理模型，在所有的空间和时间尺度上与现有的数据是一致的。我建议把这个项目分成三个子项目：1.盆地和盆地尺度的压力演化.单个管道事件的力学。3.黎凡特盆地的耦合模型。这条研究路线自然地将每个组成部分概念性地引导到下一个组成部分，并建立在从前一个组成部分获得的知识基础上。第一部分是关于黎凡特盆地超压的来源及其如何导致FEP的形成。例如，是北东-南西向构造挤压还是边缘隆起导致超压和随后的管道形成？这种超压是如何传递到每条管道的源储层的？压力模型与管道跟踪数据是否一致？随着对大尺度机制的广泛理解，第二个目标是管道事件的断裂力学。这里要回答的基本问题包括：在什么压力下骨折会开始/愈合？裂缝是如何传播和相互作用形成管道的？气体（或浮力）的作用重要吗？最后，结合前两部分的知识，这些模型可以组合成一个耦合模型，用于跨地质时期的黎凡特盆地的演化。这将为黎凡特盆地流体逸出管道的出现提供精确、有凝聚力和多尺度的解释。由于这一领域的研究是不可或缺的二氧化碳储存风险评估，这项工作可以是有用的项目，如Sleipner领域。关于该应用的一些具体问题包括：在工业过程中是否可能形成FEP，如果是，CO2注入操作员必须做些什么来避免FEP的形成？我们怎样才能更好地从地震数据中识别和描述现有管道？

This project includes a study of the numerous FEPs that are widespread in the Levant Basin as it offers an excellent natural dataset for analyzing the formation of FEPs. The basin stratigraphy consists of a c. 2 kmthick sheet of impermeable rock salt that overlies a c. 3 km thick succession of mudstone and sandstone layers (Cartwright et al., 2020). Sandstone units form the gas-hosting reservoirs which are vertically sealedby mudstone and salt. Levant FEPs vent gas from these sandstones (Oppo et al., 2020) and so penetrate through kilometers of impermeable mudstone and salt. In the north-eastern margin of the basin, 3Dseismic data reveals that pipes have been forming from 12 fixed positions over the past two million years. However, due to the westward flow of viscous salt, existing conduits are deformed and shifted, such thata new vertical pipe must form for each event every c. 10 kyr. The end result is 12 trails of pipes recording each event through geologic time since the local salt topography also enables relative dating of each event(Oppo et al., 2020, Evans et al., 2020).Aims & ObjectivesTo understand the mechanisms underlying FEP formation, I require an accurate physical model that is consistent with the available data at all spatial and temporal scales. I propose to divide the project intothree sub-projects:1. Basin and reservoir-scale pressure evolution.2. Mechanics of individual pipe events.3. Coupled model for the Levant basin.This line of enquiry naturally leads each component conceptually to the next and builds on the knowledge obtained from the previous one. The first part is concerned with the source of overpressure in the Levantbasin and how it leads to FEP formation. For example, is it NE-SW tectonic compression or marginal uplift causing overpressure and subsequent pipe formation? How is this overpressure transferred to the sourcereservoir of each pipe? Is the pressure model consistent with the pipe trail data? With a broad understanding of the large-scale mechanisms, the second objective is the fracture mechanicsof pipe events. The foundational questions to be answered here include: at what pressure will a fracture initiate/heal? How do fractures propagate and interact to form a pipe? Is the role of gas (or buoyancy)important?Finally, with the combined knowledge from the preceding two parts, these models can be combined into a coupled model for the evolution of the Levant basin across geologic time. This will provide a refined,cohesive and multi-scale explanation for the occurrence of fluid escape pipes in the Levant basin. As this area of research is integral to carbon dioxide storage risk assessment, this work can be useful to projectssuch as the Sleipner field. Some specific questions regarding this application include: Is FEP formation likely during industrial processes and if so, what must CO2 injection operators do to avoid FEP formation? Howcan we better identify and characterize existing pipes from seismic data?