Improving the long-term stability of bismuth alloy well plug systems

碳氢化合物资源开发是加拿大经济的关键驱动力。这导致了有害气体的排放，大气中二氧化碳(CO2)的积聚，并有可能污染井中的地下水。无论是降低污染，采用水力压裂，还是将二氧化碳隔离在地下，战略性封堵老旧和多余的井筒都是至关重要的。在艾伯塔省2012年的大约40万口油井中，需要适当封堵的油井数量很可能超过5万口，而且这个数字还在戏剧性地增长。尽管艾伯塔省在管理地下水意外污染和特别有害气体排放的严格标准方面处于世界领先地位，但封堵技术没有跟上需要退役的大量油井的步伐。总部位于艾伯塔省的Seal Well Inc.已经为一种基于铋锡合金的替代井眼封堵技术申请了专利，这种技术的安装成本应该会更低，而且比目前的方法可靠得多。为了使这项技术适应日益增长的用于提高石油采收率和二氧化碳封存的高腐蚀性加压二氧化碳的使用，有必要证明铋锡合金和周围的钢将具有形成永久堵头所需的有用使用寿命。该项目的重点是确定铋锡合金/钢系统在现实井下条件下的腐蚀敏感性，并通过组合策略解决因酸性气体攻击而遇到的腐蚀问题。首次开发了一种将缓蚀剂和除氧剂应用于铋锡/钢系统的方法，并在CO2饱和盐水中进行了测试。此外，还将对铋锡合金的表面结构进行改性，使其具有更好的耐腐蚀性，并将探索电解阴极保护和在铋锡表面添加保护性铋涂层的方法。这项工作的成果将是显著延长密封井技术在恶劣地下条件下的使用寿命，从而遏制世界各地日益严重的污染问题，并培训大量腐蚀技术人员。

Hydrocarbon resource development is a key driver of the Canadian economy. This has led to the emission of harmful gases, the build-up of carbon dioxide (CO2) in the atmosphere, and the potential for contaminating ground water from wells. Whether lowering pollution, employing hydraulic fracturing, or sequestering CO2 underground, strategic plugging of old and redundant wellbores is critical. Of the roughly 400,000 wells in Alberta in 2012, the number of wells that need to be properly plugged could well exceed 50,000, and this number is growing dramatically. Although Alberta leads the world in tough standards governing the unintended contamination of ground water and release of particularly harmful gases, plugging technologies have not kept pace with the vast number of wells that need to be retired. Seal Well Inc., an Alberta-based company, has patented an alternative wellbore plugging technology based on a bismuth-tin (Bi-Sn) alloy that should be less costly to install, while being far more reliable than current methods. To adapt this technology to the growing use of highly corrosive, pressurized CO2 for enhanced oil recovery and CO2 sequestration, it is necessary to demonstrate that the Bi-Sn alloy and the surrounding steel will have the useful service life needed to form a permanent plug. The focus of this project is to determine the corrosion susceptibility of the Bi-Sn alloy /steel system under realistic down-hole conditions and address corrosion issues encountered from acid gas attack through a combination of strategies. For the first time, a method of applying corrosion inhibitors and oxygen scavenger to Bi-Sn/steel systems will be developed and tested in CO2-saturated brine. Also, the surface structure of the Bi-Sn alloy will be modified to make it more corrosion resistant, and methods of electrolytic cathodic protection and addition of protective Bi coatings onto the Bi-Sn surface, will be explored. The outcome of this work will be the significant extension of the useful service life of the Seal Well technology under harsh underground conditions, thus containing a significantly escalating pollution problem throughout the world, as well as the training of a large number of personnel in corrosion technologies.