Bibliography - D. Kavetski

1. Nordbotten, Jan M., D. Kavetski, Michael Celia, and , 2009: Model for CO₂ Leakage Including Multiple Geological Layers and Multiple Leaky Wells. Environmental Science and Technology, 43(3), doi:10.1021/es801135v 743-749
   [ Abstract ]

   Geological storage of carbon dioxide (CO₂) is likely to be an integral component of any realistic plan to reduce anthropogenic greenhouse gas emissions. In conjunction with large-scale deployment of carbon storage as a technology, there is an urgent need for tools which provide reliable and quick assessments of aquifer storage performance. Previously, abandoned wells from over a century of oil and gas exploration and production have been identified as critical potential leakage paths. The practical importance of abandoned wells is emphasized by the correlation of heavy CO₂) emitters (typically associated with industrialized areas) to oil and gas producing regions in North America. Herein, we describe a novel framework for predicting the leakage from large numbers of abandoned wells, forming leakage paths connecting multiple subsurface permeable formations. The framework is designed to exploit analytical solutions to various components of the problem and, ultimately, leads to a grid-free approximation to CO₂) and brine leakage rates, as well as fluid distributions. We apply our model in a comparison to an established numerical solver for the underlying governing equations. Thereafter, we demonstrate the capabilities of the model on typical field data taken from the vicinity of Edmonton, Alberta. This data set consists of over 500 wells and 7 permeable formations. Results show the flexibility and utility of the solution methods, and highlight the role that analytical and semi-analytical solutions can play in this important problem.

2. Celia, Michael, , Jan M. Nordbotten, D. Kavetski, and S. Gasda, 2006: A Risk Assessment Modeling Tool to Quantify Leakage Potential through Wells in Mature Sedimentary Basins. Proceedings of the 8th International Conference on Greenhouse Gas Control Technologies (GHGT-8),
   [ Abstract ]

   The mature sedimentary basins of North America have a long history of oil and gas exploration and production. This has resulted in many wells being drilled, with a substantial number of them now abandoned. Therefore, injection and storage of CO₂ in these basins requires analysis of possible leakage along those wells. A computationally fast semianalytical model of CO₂ injection and potential leakage along wells has been developed, capturing many of the dominant physical characteristics of largescale injection systems. This paper illustrates the capabilities of the model using a case study based on a potential CO₂ sequestration site in Alberta, Canada. The selection of model inputs reflecting the uncertainty in the condition of abandoned wells is considered. The use of the semianalytical model in a probabilistic risk assessment framework is discussed, outlining avenues for systematic regulatory analysis of injection scenarios and systems.

3. Kavetski, D., Jan M. Nordbotten, and Michael Celia, June 2006: Analysis of Potential CO₂ Leakage through Abandoned Wells using a Semi-analytical Model. Proceedings of the XVI Intl Conf on Computational Methods in Water Resources, Copenhagen, http://proceedings.cmwr-xvi.org/getFile.py/access?contribId=1,
   [ Abstract ]

   Potential injection sites for geological CO₂ storage include deep formations in mature sedimentary basins. Many of these basins have a long history of oil and gas exploration and production and the vicinity of the injection site may therefore be perforated by hundreds of wells, potentially penetrating into the injection formation. Since typical injection operations may lead to CO₂ plums extending tens of kilometres from the injection site, geosequestration models must be able to simulate large spatial domains (up to and above 1,000 km²), while resolving the local dynamics in all the wells. Furthermore, many of these wells are abandoned and their locations and hydraulic properties might be uncertain or unknown. Therefore, risk assessment based on Monte Carlo simulations may be necessary to estimate the resulting uncertainty in the leakage. In this paper, we present a semi-analytical model that simulates the evolution of CO₂ plumes and leakage in multiple brine aquifers penetrated by multiple wells over decadal to century time scales. The model equations and state variables are obtained from the self-similarity of the plume shapes and are defined solely at well locations. Since the model does not require domain discretisation in the traditional numerical sense, it is highly computationally efficient, potentially thousands of times faster than existing numerical multiphase simulators. This paper demonstrates the insights gained by applying this model to a potential injection site in the Alberta Basin, Canada, with more than 500 existing wells over a domain of 900 km². Several leakage measures and statistics are presented and discussed.

4. Celia, Michael, , Jan M. Nordbotten, D. Kavetski, and S. Gasda, May 2005: Modeling Critical Leakage Pathways in a Risk Assessment Framework: Representation of Abandoned Wells. Proceedings of the 4th Annual Conference on Carbon Capture and Sequestration, http://www.netl.doe.gov/publications/proceedings/05/carbon-seq/Tech%20Session%20Paper%20115.pd,
   [ Abstract ]

   In many locations in North America, likely injection sites for CO₂ storage in deep geological formation are located in mature sedimentary basins. These basins have a century-long history of oil and gas exploration and production, which has led to hundreds of thousands of wells (the Alberta Basin) to more than a million wells (Texas) being drilled. The spatial density of these wells is on the order of 0.5 to 5 wells per square kilometer. Therefore, a typical injection will produce a CO₂ plume that intersects hundreds of existing wells, many of which are abandoned and some of which have uncertain or unknown locations. In order to analyze the leakage potential in such situations, computational models must be developed that can cover large spatial areas (of order 1,000 km²) while resolving the local flow dynamics in all of the hundreds of wells. In addition, both the layered structure of the subsurface, and possible leakage along wells and into successive overlying permeable layers in the subsurface, also need to be represented. We have developed a semi-analytical model that can simulate all of these attributes, over decadal to century time scales, while running quickly on a laptop computer. With this tool, risk assessment based on Monte Carlo analysis can be carried out, and a quantitative analysis of leakage potential can be performed.

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