Combining electromagnetic and seismic methods to monitor carbon dioxide sequestration

结合电磁和地震方法监测二氧化碳封存

• 批准号: NE/I018735/1
• 负责人: Anton Ziolkowski
• 金额: $ 8.58万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Training Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI018735%2F1
• 关键词: Combining; electromagnetic; seismic; methods; monitor

SUMMARY Project description This project is concerned with developing a geophysical strategy, using seismic and electromagnetic (EM) methods, for monitoring sequestration of carbon dioxide in reservoirs buried hundreds of metres beneath the sea floor in areas such as the North Sea. The motivation for this research comes from the CASE partner, Petroleum Geo-Services (PGS) who wishes to develop a service in this area that is both operationally efficient and technically sound. When carbon dioxide is injected into saline aquifers, or into reservoirs that previously contained hydrocarbons, it occupies part of the pore space in the rock and changes the rock properties. The effect on the seismic response is a dramatic decrease in acoustic impedance with the early injection of a small amount of gas. Thereafter the seismic response is essentially unchanged. The resistivity of the reservoir rock is affected only slightly by early CO2 injection, but as the quantity of CO2 increases, the rock resistivity increases exponentially. Electromagnetic methods therefore have the potential to monitor the quantity of CO2 stored in a reservoir. The migration and inversion of seismic reflection data is now mature. This project focuses on the electromagnetic data. The objectives of the project are: 1. To relate the magnitude of the observed seismic and electromagnetic anomalies to the quantity of injected gas, the gas saturation, and the depth of the reservoir, and to determine the detectability of the anomalies in the presence of noise. 2. To develop a top-down modelling approach to invert the synthetic electromagnetic data for subsurface resistivities, based on a new ray-theoretical approach being developed in Edinburgh. This is totally new and relates the peak of the earth impulse response to a known subsurface 'ray path.' 3. To apply the same approach to relate the electromagnetic anomalies to subsurface changes in resistivity. 4. To apply the developed inversion method to real transient electromagnetic data. Workplan 1. Model-building. Build a three-dimensional (3D) physical and petrophysical model of a reservoir embedded in a background medium below a water layer of variable depth. The resistivity model will be anisotropic, with the vertical component of resistivity greater than the horizontal (3 months). 2. CO2 Sequestration Simulate changes in the seismic, electromagnetic (resistivity) and petrophysical properties of the reservoir by adding gas to the pore fluid in the reservoir (1 month). 3. Geophysical Monitoring Simulate both seismic and transient electromagnetic surveys over the reservoir using the 'Nucleus' modelling package provided by PGS (3 months). 4. Feasibility Study Determine the magnitude of the observed seismic and electromagnetic anomalies as a function of the quantity of injected gas. We expect large seismic anomalies for early gas injection and very little change thereafter, while the EM data should show small anomalies for early gas and then progressively larger anomalies with increasing gas, as indicated in the figure. The detection of the computed anomalies in real data with noise needs to be estimated using realistic noise measurements provided by PGS (6 months). 5. Inversion of EM synthetic data Develop a top-down modelling approach to invert the synthetic electromagnetic data for subsurface resistivities, based on a new ray-theoretical approach being developed in Edinburgh. This is totally new and relates the peak of the earth impulse response to a known subsurface 'ray path.' (1 year) 6. Inversion of EM time-lapse synthetic data Apply the same approach to relate the electromagnetic anomalies to subsurface changes in resistivity. (6 months). 7. Inversion of real transient EM data Apply the developed inversion method to real transient electromagnetic data in PGS's Edinburgh office. (6 months).

概要项目描述该项目涉及使用地震和电磁（EM）方法制定地球物理策略，以监测北海等地区海底数百米以下埋藏的水库中二氧化碳的封存情况。这项研究的动机来自CASE的合作伙伴，石油地理服务（PGS），他们希望在这一领域开发一种既有效又技术可靠的服务。当二氧化碳被注入含盐含水层或先前含有碳氢化合物的储层时，它占据了岩石中的部分孔隙空间并改变了岩石的性质。对地震响应的影响是随着少量气体的早期注入而使声阻抗急剧下降。此后，地震响应基本不变。储层岩石的电阻率仅受早期CO2注入的轻微影响，但随着CO2量的增加，岩石电阻率呈指数增加。因此，电磁方法有可能监测储存在储层中的CO2的量。地震反射数据的偏移和反演已经比较成熟。本项目的重点是电磁数据。该项目的目标是：1。将观测到的地震和电磁异常的幅度与注入气体的量、气体饱和度和储层的深度联系起来，并确定在存在噪声的情况下异常的可探测性。2.根据爱丁堡正在开发的新射线理论方法，开发一种自上而下的建模方法，以反演地下电导率的合成电磁数据。这是全新的，并且将地球脉冲响应的峰值与已知的地下射线路径相关联。' 3.应用同样的方法将电磁异常与地下电阻率的变化联系起来。4.将所提出的反演方法应用于真实的瞬变电磁资料。工作计划1.建模。建立一个三维（3D）的物理和岩石物理模型的储层嵌入在一个背景介质下的水层的变化深度。电阻率模型将是各向异性的，电阻率的垂直分量大于水平分量（3个月）。2.通过向储层孔隙流体中添加气体，模拟储层的地震、电磁（电阻率）和岩石物理特性的变化（1个月）。3.使用PGS提供的“Nucleus”建模软件包模拟对储层的地震和瞬变电磁测量（3个月）。4.可行性研究确定观测到的地震和电磁异常的大小，作为注入气体量的函数。我们预计，早期天然气注入会出现大的地震异常，此后变化很小，而EM数据应显示早期天然气的小异常，然后随着天然气的增加，异常逐渐变大，如图所示。需要使用PGS提供的实际噪声测量值（6个月）来估计在含噪声的真实的数据中计算出的异常的检测。5.电磁合成数据的反演基于爱丁堡正在开发的新射线理论方法，开发一种自上而下的建模方法，以反演地下电磁场的合成数据。这是全新的，并且将地球脉冲响应的峰值与已知的地下射线路径相关联。（1年）6。EM时移合成数据的反演应用相同的方法将电磁异常与地下电阻率的变化联系起来。（6个月）。7.真实的瞬变电磁数据的反演将开发的反演方法应用于PGS爱丁堡办公室的真实的瞬变电磁数据。（6个月）。