Safeguarding CO2 Storage by Restoring Well Integrity Using Leakage Rate Modeling LRM along Wellbore in Depleted Gas Fields Offshore Sarawak

P. A. Patil, P. Chidambaram, M. Amir, P. Tiwari, Mahesh S. Picha, H. A. Hakim, Dr. Rabindra Das, Khaidhir B A Hamid, R. Tewari
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引用次数: 3

Abstract

Ensuring long-term integrity of existing plugged and abandoned (P&A) and active wells that penetrated the selected CO2 storage reservoir is the key to reduce leakage risks along the wellpath for long-term containment sustainability. Restoring the well integrity, when required, will safeguard CO2 containment for decades. Well integrity is often defined as the ability to contain fluids with minimum to nil leakage throughout the project lifecycle. With a view to develop depleted gas fields as CO2 storage sites in offshore Sarawak, it is vital to determine the complexity involved in restoring the integrity of these P&A wells as well as the development wells. Leakage Rate Modeling (LRM) was performed to identify and evaluate the associated risks for designing the remedial action plan to safeguard CO2 storage site. The P&A wells in the identified depleted gas fields were drilled 35–45 years ago and were not designed to withstand high CO2 concentration downhole conditions. Corrosive-Resistant Alloy (CRA) tubulars and CO2 resistant cement were not used during well construction and downhole pressure and temperature conditions may have further degraded the material strength and elevated the corrosion susceptibility. As a proof of concept, single well was selected to assess the loss of containment along the wellbore and to determine the complexity in resorting the well integrity, multiple scenarios were considered in LRM and composite structure and barrier parameters were assigned to estimate possible leakage pathways. Detailed numerical models were simulated for estimating leakage from reservoir to the surface through possible leakage pathways. Risks were identified and remedial action plan was designed for restoring well integrity. Post remedial plan covers Marine CO2 dispersion modeling to design comprehensive monitoring and mitigation plan for potential CO2 leakage in the marine environment. This study summarizes the unique challenge associated with estimating well integrity and re-entering existing P&A wells. Leakage rate modeling along these wells involves uncertainties but when carried out with realistic parameters, it can be used as a predicting tool to determine the nature and complexity of leakage. Integrating with site survey results for any indication of gas bubbling, decision can be made to restoring the well integrity. The paper outlines the detail strategic options to safeguard CO2 storage by restoring well integrity using LRM and integrating with marine CO2 dispersion modeling. Assessing well integrity of P&A wells on individual basis, risk is assessed and identified. Proper remedial actions are proposed accordingly. Quantification of all the uncertainties involved needs to be conducted that may affect long-term security of CO2 storage site.
在Sarawak近海枯竭气田,利用泄漏率建模LRM恢复井筒完整性,保护CO2储存
确保现有封堵弃井(P&A)和活动井的长期完整性,是降低沿井径泄漏风险、实现长期密封可持续性的关键。如果需要,恢复油井的完整性将在未来几十年里保护二氧化碳的控制。井的完整性通常被定义为在整个项目生命周期中以最小或零泄漏的方式容纳流体的能力。为了开发沙捞越近海的废弃气田作为二氧化碳储存场所,确定这些弃井和开发井的完整性所涉及的复杂性至关重要。采用泄漏率模型(LRM)来识别和评估相关风险,以设计保护CO2储存场地的补救行动计划。在已确定的枯竭气田中,弃井是在35-45年前钻探的,并且不能承受高二氧化碳浓度的井下环境。在施工过程中没有使用抗腐蚀合金(CRA)管柱和抗二氧化碳水泥,井下压力和温度条件可能会进一步降低材料强度,提高腐蚀敏感性。为了验证这一概念,选择单井来评估沿井筒的安全壳损失,并确定采用井完整性的复杂性,在LRM中考虑了多种情况,并分配了复合结构和屏障参数来估计可能的泄漏路径。模拟了详细的数值模型,以估计通过可能的泄漏途径从水库到地表的泄漏量。确定了风险并设计了补救行动计划,以恢复井的完整性。后期补救计划包括海洋二氧化碳扩散建模,以设计海洋环境中潜在二氧化碳泄漏的综合监测和缓解计划。该研究总结了评估井完整性和重新进入现有弃井的独特挑战。这些井的泄漏率建模具有不确定性,但如果使用实际参数进行建模,则可以作为确定泄漏性质和复杂性的预测工具。结合现场调查结果,发现任何气泡迹象,就可以决定恢复井的完整性。本文概述了通过使用LRM恢复油井完整性并与海洋二氧化碳分散建模相结合来保护二氧化碳储存的详细策略选择。在单个井的基础上评估井的完整性,评估和识别风险。因此,提出了适当的补救措施。需要对可能影响CO2储存场地长期安全的所有不确定因素进行量化。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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