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Developing the UK national centre of excellence for geohazards through quantification of field-scale turbidity current hazard

通过量化现场规模浊流危害，建立英国国家地质灾害卓越中心

基本信息

批准号：
NE/M007138/1
负责人：
Mattieu Cartigny
金额：
$ 13.07万
依托单位：
NATIONAL OCEANOGRAPHY CENTRE
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FM007138%2F1
关键词：
Developing UK national centre excellence

项目摘要

Our over-arching aim is to better understand the impact of powerful submarine flows, called turbidity currents, on pipelines and other seabed infrastructure used to recover oil and gas. Turbidity currents pose a serious hazard to expensive seabed installations, especially in deeper-water settings. These sediment flows are particularly hazardous because they can be exceptionally powerful (travelling at speeds of up to 20 m/s), and can flow for long distances (100s km), causing damage over vast areas of seafloor. Even weaker flows travelling at ~1-2 m/s can severely damage seafloor equipment, or break strategically important submarine telecommunication cables, while some flows have maintained speeds in excess of 5 m/s for hundreds of kilometres. This makes hazard mitigation by local re-routing of pipelines difficult. Where seafloor topography is rugged, many operators route pipelines within canyons; however, these are focal points for turbidity current activity. Mitigating against turbidity current geohazards, particularly within canyons, can have very significant cost implications for industry - additional deepwater pipeline routing costs ~ $3 million per km. Mitigation costs of $2 billion are predicted to route pipelines under the Congo Canyon, where turbidity current hazard is deemed to be high. Perhaps just as importantly, pipeline oil spills could lead to major reputational damage. Given concern over accidents to structures used to recover oil and gas, a focus on geohazards is also aligned with NERC's environmental responsibility. The most remarkable aspect of turbidity currents is how few direct measurements there are from flows, in part because they damage monitoring equipment placed on the seafloor. Several lines of evidence point to the existence of a region of high sediment concentration at the base of turbidity currents. These dense basal layers are of key important because of: (i) their location just above the bed where most submarine infrastructure is located; and (ii) they carry most momentum due to their large density. Yet, sediment concentration has never been measured directly measured in these layers. Physical experiments, numerical modeling and ancient deposits provide valuable insights into these flows; but there is a compelling need to monitor full-scale flows in action. This project is timely because it will develop innovative field-based techniques for imaging near bed flow structure and vertical changes in sediment concentration in situ.Aims: (1) Our first aim is to develop and field test a novel technique for remote sensing of dense near bed layers. (2) Our second aim is to better understand the nature of near bed dense layers. (3) Our third aim is to embed improved understanding of dense near-bed layers into numerical models used by industry to assess impact of turbidity currents on oil and gas pipelines. (4) The project will also help to establish an international centre of excellence for submarine geohazard research at the UK National Oceanography Centre. Here we propose to make direct measurements of dense basal layers that form part of the turbidity currents occuring daily during the elevated summer river discharge on the Squamish Delta, located in Howe Sound, Canada. We will use an innovative four-point mooring to hold a vessel and suspended instrumentation payload stable above an active channel system, while we observe the dense basal layer with a Chirp sub-bottom profiler. The low frequency and broad bandwidth (1.5 -13.0 kHz) Chirp source guarantees penetration through dense near-bed layers, resolving layers with ~10 cm resolution. These field observations will help to understand the fundamental character of near bed layers, and the situations in which they form.

我们的首要目标是更好地了解强大的海底水流（称为浊流）对用于开采石油和天然气的管道和其他海底基础设施的影响。湍流对昂贵的海底设施构成严重危害，特别是在深水环境中。这些沉积物流特别危险，因为它们可能异常强大（速度高达每秒20米），并可长距离流动（100公里），对大片海底造成损害。即使流速为1-2米/秒的较弱水流也会严重损坏海底设备，或破坏具有重要战略意义的海底通信电缆，而有些水流的速度超过5米/秒达数百公里。这使得通过局部改变管道路线来减轻危害变得困难。在海底地形崎岖的地方，许多运营商在峡谷内铺设管道;然而，这些是浊流活动的焦点。减轻浊流地质灾害，特别是峡谷内的浊流地质灾害，可能会对工业产生非常重大的成本影响--额外的深水管道布线成本约为每公里300万美元。预计在刚果峡谷下铺设管道的缓解成本为20亿美元，在那里浊流危害被认为是高的。也许同样重要的是，管道漏油可能导致重大声誉损害。鉴于对用于开采石油和天然气的结构事故的关注，对地质灾害的关注也与NERC的环境责任相一致。浊流最值得注意的方面是，从水流中直接测量的数据很少，部分原因是它们损坏了放置在海底的监测设备。若干证据表明，在浊流底部存在一个高沉积物浓度区。这些致密的基底层非常重要，因为：（i）它们位于大多数海底基础设施所在的海床上方;（ii）由于它们的密度大，它们携带的动量最大。然而，沉积物浓度从来没有直接测量这些层。物理实验、数值模拟和古代沉积物为这些流动提供了宝贵的见解;但迫切需要监测实际的全尺度流动。本项目是及时的，因为它将开发创新的基于现场的技术成像近床流动结构和泥沙浓度的垂直变化在situation.Aims：（1）我们的第一个目标是开发和现场测试一种新的技术，用于遥感致密近床层。(2)我们的第二个目标是更好地了解近床致密层的性质。(3)我们的第三个目标是将对致密近床层的更好理解嵌入到工业使用的数值模型中，以评估浊流对石油和天然气管道的影响。(4)该项目还将帮助在联合王国国家海洋学中心建立一个海底地质灾害研究国际英才中心。在这里，我们建议直接测量致密的基底层，形成每天发生在高架夏季河流排放的斯夸米什米什三角洲，位于豪湾，加拿大浊流的一部分。我们将使用一个创新的四点系泊，以保持船舶和悬挂仪器有效载荷稳定以上的主动通道系统，而我们观察密集的基底层与Chirp次底剖面仪。低频和宽带宽（1.5 - 13.0 kHz）Chirp源保证穿透密集的近床层，以~10 cm的分辨率分辨层。这些实地观察将有助于了解近床层的基本特征，以及它们形成的情况。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

A General Model for the Helical Structure of Geophysical Flows in Channel Bends

DOI：
10.1002/2017gl075721
发表时间：
2017-12
期刊：
Geophysical Research Letters
影响因子：
5.2
作者：
M. Azpiroz-Zabala;M. Cartigny;E. Sumner;M. Clare;P. Talling;D. Parsons;C. Cooper
通讯作者：
M. Azpiroz-Zabala;M. Cartigny;E. Sumner;M. Clare;P. Talling;D. Parsons;C. Cooper

Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons.

DOI：
10.1126/sciadv.1700200
发表时间：
2017-10
期刊：
Science advances
影响因子：
13.6
作者：
Azpiroz-Zabala M;Cartigny MJB;Talling PJ;Parsons DR;Sumner EJ;Clare MA;Simmons SM;Cooper C;Pope EL
通讯作者：
Pope EL

Quantification of near-bed dense layers and implications for seafloor structures: New insights into the most hazardous aspects of turbidity currents

近床致密层的量化及其对海底结构的影响：对浊流最危险方面的新见解