The Sleipner storage site: Capillary flow modeling of a layered CO2 plume requires fractured shale barriers within the Utsira Formation
The Sleipner storage site: Capillary flow modeling of a layered CO2 plume requires fractured shale barriers within the Utsira Formation
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DOI：
10.1016/j.ijggc.2013.11.017
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发表时间：
2014-02-01
影响因子：
3.9
通讯作者：
Haszeldine, R. Stuart
中科院分区：
文献类型：
--
作者：
Cavanagh, Andrew J.;Haszeldine, R. Stuart
为了防止海洋酸化和减少温室气体排放，有必要捕获和储存二氧化碳。位于挪威近海的Sleipner储存场是世界上第一个也是最大的温室气体工程废物储存库。CO2从Sleipner凝析气田中分离出来，储存在乌齐拉组的孔隙中，乌兹拉组是一个位于地表以下约1公里、距离海岸200公里的含盐含水层。自1996年以来，油田运营商挪威国家石油公司每年向储存地点注入近100万吨捕获的二氧化碳。漂浮的二氧化碳羽流迅速上升，穿过含水层内八层薄薄的页岩屏障，在不到三年的时间里到达顶部密封。羽流的进展受到8次地震调查以及重力和电磁监测的监测，这些监测记录了9个薄二氧化碳层的扩散。本文提出了一个毛细管流动模型，使用侵入渗流物理，准确地匹配羽流的几何形状。该方法不同于标准的达西流模拟，它不能匹配羽流的几何形状。校准的毛细管流模拟表明，羽流的质量平衡是可能的，但只能复制羽流的几何形状，如果薄层内页岩屏障断裂。该模型能够估计页岩屏障行为和盖层性能。考虑到岩石的围压和羽流的弱超压，裂缝不太可能是由CO2注入引起的，因此压裂必须先于注入。一个新的机制是：区域冰盖的冰川消融，迅速和反复卸载约1公里的冰。诱导的瞬时孔隙压力足以水力压裂薄页岩。裂缝使二氧化碳快速上升，导致多层羽流。在北海北方和其他地区的浅层CO2储存点，第四纪冰盖的负载可能会以类似的方式表现。(C)2014作者由爱思唯尔有限公司出版。保留所有权利。
To prevent ocean acidification and mitigate greenhouse gas emissions, it is necessary to capture and store carbon dioxide. The Sleipner storage site, offshore Norway, is the world's first and largest engineered waste repository for a greenhouse gas. CO2 is separated from the Sleipner gas condensate field and stored in the pore space of the Utsira Formation, a saline aquifer approximately 1 km below the surface and 200 km from the coast. Statoil, the field operator, has injected almost 1 Mt/yr of captured CO2 into the storage site since 1996. The buoyant CO2 plume ascended rapidly through eight thin shale barriers within the aquifer to reach the top seal in less than three years. The plume's progress has been monitored by eight seismic surveys, as well as gravimetric and electromagnetic monitoring, which record the spreading of nine thin CO2 layers. This paper presents a capillary flow model using invasion percolation physics that accurately matches the plume's geometry. The approach differs from standard Darcy flow simulations, which fail to match the plume geometry. The calibrated capillary flow simulation indicates that a mass balance for the plume is likely, but can only replicate the plume geometry if the thin intra-formational shale barriers are fractured. The model enables an estimate of the shale barrier behavior and caprock performance. The fractures are very unlikely to have been caused by CO2 injection given the confining stress of the rock and weak overpressure of the plume, and so fracturing must pre-date injection. A novel mechanism is suggested: the deglaciation of regional ice sheets that have rapidly and repeatedly unloaded approximately 1 km of ice. The induced transient pore pressures are sufficient to hydro-fracture thin shales. The fractures enable fast CO2 ascent, resulting in a multi-layered plume. Shallow CO2 storage sites in the Northern North Sea and other regions that have been loaded by Quaternary ice sheets are likely to behave in a similar manner. (C) 2014 The Authors. Published by Elsevier Ltd. All rights reserved.