Methodology for Assessing Transport Properties of Wells Used in the Geological Storage of Carbon Dioxide

• Author / Creator

  Moreno Tellez, Francisco J

• One of the aspects of climate change is global warming, which can be defined as the increase in the average temperature of the Earth’s near-surface air and the oceans and its projected continuation. Scientific understanding of the cause of global warming has been increasing. In its fourth assessment of the relevant scientific literature, the Intergovernmental Panel on Climate Change (IPCC) reported that scientists were more than 90% certain that most of global warming was being caused by increasing concentrations of greenhouse gases (GHG) produced by human activities. Common GHGs in the Earth’s atmosphere include water vapor, carbon dioxide, methane, nitrous oxide, ozone, and chlorofluorocarbons. Carbon dioxide (CO2) is the most important anthropogenic GHG that has significant contribution to the climate change. Carbon dioxide (CO2) emissions come mostly from fossil fuel combustion, cement production, and land use changes such as deforestation. Ways to lessen the environmental impact of fossil fuel combustion technologies, which currently comprise a substantial portion of the planet energy supply, are being evaluated internationally. One promising option is carbon capture and storage (CCS). CCS involves capturing CO2 emissions from large point sources and storing them underground in suitable geological formations. The process of storing CO2 is defined as geological CO2 sequestration or CO2 geo-sequestration. Suitable geological formations include declining oil reservoirs, un-minable coal seams, depleted oil and gas reservoirs, and saline formations. Storage options such as enhanced oil recovery (EOR) for declining oil reservoirs and enhanced coal-bed methane (ECBM) recovery for un-mineable coal seams provide short-term storage opportunities. On the other hand, storage in depleted oil and gas reservoirs and deep saline formations can be considered longer-term options. The storage of CO2 is not risk-free, but if it is properly planned, operated and monitored, risk can be reduced substantially. Leakage of stored CO2 from a storage formation may take place due a loss in the structural integrity of the cap rock. This integrity is controlled by two mechanisms, which are geological leakage mechanism and wellbore leakage mechanism. Wellbores provide access to a reservoir and may serve as preferential flow paths by allowing upward migration of injected CO2. This migration, unlike the lateral movement of the CO2 plume in the reservoir, might occur in a very short time frame, on the order of years to tens of years and, in some critical cases, less. This can have potential adverse effects in relation to safety and/or environmental damage, thus posing a risk to the success of CO2 underground disposal. For CO2 storage, the ultimate goal for well-leakage models is to serve as inputs for a certification framework and risk analysis. In order to achieve this goal, there is a need to further investigate a more realistic representation of wellbore element bulk permeability that can differ from element to element within a wellbore system. Researchers have adopted the concept of wellbore lifecycle and recognized its importance in understanding wellbore behavior under different states. However, all of these efforts are scattered and dispersed due to either the various approaches of the study and the multi-disciplinary nature of the problem. In addition, direct measurements of wellbore bulk permeability along well segments are limited and very expensive to obtain. As a result, there is a need to develop a unified method and a conceptual model, which can be used as a practical engineering platform to assess wellbore integrity. A methodology to assess the transport properties of wells is introduced. The methodology presented systematically identifies and estimates the effect of each of the physical and chemical processes responsible for the alteration of the transport properties of wells. Based on the physics involved in these permeability alteration processes, a four-group classification is proposed: geomechanical damage, hydrochemical damage, mud removal, and deterioration damage (cement). These processes can occur during the various phases of a well’s life, namely drilling, completion, production, and abandonment. Example of wellbore bulk permeability calculation for a typical 54 –year old vertical well, drilled in the Weyburn oil field in southeastern Saskatchewan, Canada, using the proposed methodology is presented. Estimate of permeability is in good agreement with direct measurements conducted as a component of the IEAGHG Weyburn-Midale CO2 Monitoring and Storage Project.

• Subjects / Keywords

  • Effective permeability
  • Well integrity
  • Cement barrier
  • CO2 Storage

• Graduation date

  Fall 2014

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R32B8VJ7V

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.