Well Integrity and Sealing in CO2 Sequestration Wells
Abstract
CO2 sequestration is a cost-effective and safe way to help mitigate climate change. Sustained well integrity and zonal isolation of CO2 by cement for the required 1000 year trapping period may be challenging. Some researchers report that cement fails when exposed to CO2 leading to potential leakage into the atmosphere or other underground zones. Others show cement samples from 30-50 year old CO2 wells that maintain the well’s sealing integrity, even though carbonization was found. This presentation provides reasons likely for this disparity between research lab test results and actual well performance data along with best practices to provide efficient cement-based systems for maintaining CO2 containment in storage and EOR (enhanced oil recovery) reservoirs. This discussion includes the geochemical conditions surrounding wells and the positive, long-term effects on cement durability, sealing integrity, and the protection of well casing from CO2 induced corrosion. Also discussed are recent laboratory results testing cement samples surrounded by formation material treated at two different downhole conditions. In one case the cement specimens were treated with a 40% humid CO2 at 140°F and 2000 psi whereas in the second case they were treated with saturated CO2 in water at 200°F and 2000 psi for various time intervals. Results show that samples of carefully designed cement systems had carbonization without any sign of loss of mechanical or sealing integrity which could lead to zonal isolation and well integrity failures. We also will report on a new lab method proposed to determine CO2 sealing performance by cement in a relatively short time period compared to previous methods. In summary, we will discuss a comprehensive approach that may be taken to help ensure longer term effective well integrity and CO2 containment in new CO2 wells and remedial solutions for old wells and for plugging and abandoning wells.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.U41A0013S
- Keywords:
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- 1009 GEOCHEMISTRY / Geochemical modeling;
- 1011 GEOCHEMISTRY / Thermodynamics;
- 1012 GEOCHEMISTRY / Reactions and phase equilibria;
- 1600 GLOBAL CHANGE