Sensing Cracks in the Earth Using Multiple Scattering and Nonlinear Elasticity

使用多重散射和非线性弹性来感测地球裂缝

• 批准号: RGPIN-2016-04415
• 负责人: Malcolm, Alison
• 金额: $ 2.4万
• 依托单位: Memorial University of Newfoundland
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=685012
• 关键词: Sensing; Cracks; Earth; Using; Multiple

Cracks are increasingly important to our understanding of Earth resources and structures. They hold most of the unconventional oil and gas reserves, are important for geothermal energy, and play a role in conventional oil and gas production, volcanic eruptions and perhaps even earthquakes. In wavefields, they introduce scattering effects, in which waves reflect many times between different cracks in the subsurface, and it is likely cracks that introduce the dependence of elastic paramters on stress and strain, making rocks exhibit strong elastic nonlinearity. The long term goals of this research program are to better understand how to sense and characterize rocks. On the shorter term, we aim to (i) to better understand the role of cracks in the nonlinear elasticity of rocks with the long-term goal of using these parameters to image crack density and orientation and (ii) to use microseismic data sets to characterize scattering from cracks in volcanic regions to characterize cracks through scattering attenuation and fluids through intrinsic attenuation.*** To look at how cracks influence the nonlinearity of rocks, we will work from a recently developed experiment that uses a high-amplitude shear wave to perturb the elastic properties of a rock, and senses those perturbations with a P-wave. We have data indicating that this experiment senses the orientation of cracks in a sample. To better understand why this is the case, and the underlying mechanisms of nonlinear elasticity, we will develop a comprehensive numerical model of this experiment. To verify this model, we will perform a suite of new lab experiments focussing on igneous rocks (our past work has focussed on sedimentary rocks). ***To characterize cracks from microseismic data, we will use a data set from Iceland, collected to monitor seismicity for volcanic and geothermal applications. We will use these data to measure scattering strength and intrinsic attenuation of the region and its variability. We will perform laboratory and numerical experiments, using the techniques developed for the nonlinear elasticity part of the project to better understand our results and will interpret them in terms of local stress changes. *** The novelty of this work is in the use of both techniques to understand cracks, their orientation, density, and properties. The approach of using a combination of numerical modelling, laboratory, and field data will improve our understanding of the physics underlying these phenomena, and will change how we sense cracks in the subsurface. This is important to the oil and gas industry, which plays a significant role in the Canadian economy, as well as to the geothermal industry, which is likely to play a role in future energy supply and has longer term implications for natural hazard mitigation in Canada and elsewhere.**

裂缝对于我们对地球资源和结构的理解越来越重要。 他们拥有大多数非常规的石油和天然气储量，对地热能很重要，并且在常规的石油和天然气生产，火山喷发甚至地震中发挥作用。 在波场中，它们引入了散射效应，其中波浪反映了地下不同裂缝之间的许多次，并且可能裂纹引入了弹性参数对压力和应变的依赖性，从而使岩石表现出强烈的弹性非线性。该研究计划的长期目标是更好地了解如何感知和表征岩石。 在短期内，我们的目标是（i）更好地理解裂纹在岩石非线性弹性中的作用，其长期目标是使用这些参数图像裂纹密度和取向图像裂纹密度和取向以及（ii）使用微量震荡数据集来表征来自裂纹的裂缝，以表征裂纹，以通过裂纹来表征裂纹，从而通过散射进行散射，从而逐渐逐渐衰减的裂纹，以构成interlin的intriniation interlinivation interlinivation intriniation interlinivation Intriniation intriniation intriniation interliniptiation interliniption interliniptiation interlin interliniphatualigation。岩石，我们将从最近开发的实验中工作，该实验使用高振幅剪切波来扰动岩石的弹性特性，并感应使用P波的扰动。 我们有数据表明该实验会感觉到样品中裂纹的方向。 为了更好地理解为什么是这种情况以及非线性弹性的潜在机制，我们将开发该实验的全面数值模型。 为了验证该模型，我们将执行一系列针对火成岩岩石的新实验室实验（我们过去的工作集中在沉积岩上）。 ***为了表征微观震荡数据的裂纹，我们将使用冰岛收集的数据集，以监视火山和地热应用的地震性。我们将使用这些数据来衡量该区域及其可​​变性的散射强度和内在衰减。我们将使用针对项目的非线性弹性部分开发的技术进行实验室和数值实验，以更好地了解我们的结果，并根据局部压力变化来解释它们。 ***这项工作的新颖性在于使用两种技术来了解裂纹，其方向，密度和特性。 使用数值建模，实验室和现场数据组合的方法将提高我们对这些现象基础物理学的理解，并会改变我们感觉地下裂纹的方式。 这对于在加拿大经济以及地热行业中起着重要作用的石油和天然气行业很重要，这很可能在未来的能源供应中发挥作用，并且对加拿大和其他地方的自然危害有长期影响。** ** **