Experimental Investigation and Subsequent Modeling of the Cement Microstructure and Integrity of Cement/Casing and Cement/Formation Interfaces Under Downhole Stress Conditions

井下应力条件下水泥微观结构和水泥/套管和水泥/地层界面完整性的实验研究和后续建模

• 批准号: RGPIN-2022-02956
• 负责人: Kuru, Ergun
• 金额: $ 2.84万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=761100
• 关键词: Experimental; Investigation; Subsequent; Modeling; Cement

Methane is a potent greenhouse gas (GHG) that is 25 times more powerful than carbon dioxide. In Canada, methane emissions make up about 15% of all GHG emissions. Upstream oil and gas facilities are Canada's largest industrial emitters of methane, releasing 44% of the country's total methane emissions. Within the upstream oil and gas industry, a significant fraction of methane emission results from fugitive leaks arising from surface casing vent flow (SCVF) and gas migration (GM). Bulk cement, as well as cement/casing and casing /rock interfaces, are likely to be the weak spots in oil and gas wells in terms of leakage and long term well integrity. Debonding of cement from casing and/or formation, and subsequent loss of zonal isolation, is a significant contributor to fugitive methane emissions from SCVF and GM in oil and gas wells. Understanding the mechanisms of leakage pathway formation is crucial for assessment and improvement of cement performance in oil and gas wells - whether the wells are producing or plugged and abandoned. Comprehensive experimental and numerical studies of the mechanisms of cement failure and debonding, and how these impact fluid movement through the cement microstructure, are therefore proposed. An Advanced Wellbore Simulator capable of investigating flow through cemented wellbore sections under realistic downhole conditions (i.e. 43 MPa and 120 °C) will be used to investigate the integrity of the cement body, as well as the cement/casing interfaces, under representative downhole stress conditions (i.e., cyclic pressure and thermal stress conditions). Nano-CT based digital image processing of downscaled samples simulating cement body and various interface conditions (e.g., cement-casing, cement-rock) will be used to analyze the effect of downhole stress conditions. This technique will be combined with a computational fluid dynamic modelling of formation fluid flow through the 3D microstructures of the samples. Together, this new methodology will assess the permeability of cemented wellbore sections, which represent potential microscale leakage pathways in a well. The experimental investigation and numerical model study proposed in this project will result in an improved understanding of the drivers behind fluid leakage (i.e. stresses creating microchannels along the cement/casing, cement/borehole interfaces and microfractures within the cement body). The results will allow for the design and development of new, more reliable barrier technologies that can be used for more cost-effective mitigation of fugitive methane emissions. As part of the Pan-Canadian Framework on Clean Growth and Climate Change, the Government of Canada reaffirmed its commitment to reduce GHG emissions 40-45% below 2012 levels by 2025. The proposed research is, therefore, well aligned with strategic direction of the Government of Canada's efforts to reduce GHG.

甲烷是一种强效温室气体 (GHG)，其威力是二氧化碳的 25 倍。在加拿大，甲烷排放量约占所有温室气体排放量的 15%。上游石油和天然气设施是加拿大最大的甲烷工业排放源，排放量占该国甲烷总排放量的44%。在上游石油和天然气行业中，很大一部分甲烷排放是由表层套管通风流 (SCVF) 和气体运移 (GM) 引起的逸散性泄漏造成的。 散装水泥以及水泥/套管和套管/岩石界面可能是油气井在泄漏和长期井完整性方面的薄弱环节。水泥从套管和/或地层中脱粘，以及随后的区域隔离丧失，是油气井中 SCVF 和 GM 逸散性甲烷排放的一个重要因素。 了解泄漏通道形成的机制对于评估和改进油气井水泥性能至关重要 - 无论是生产井还是堵塞和废弃的井。因此，提出了对水泥失效和脱粘机制以及它们如何影响水泥微观结构中流体运动的综合实验和数值研究。 先进的井眼模拟器能够研究在实际井下条件（即 43 MPa 和 120 °C）下通过固井井眼部分的流动，将用于研究在代表性井下应力条件（即循环压力和热应力条件）下水泥体以及水泥/套管界面的完整性。基于纳米 CT 的数字图像处理模拟水泥体和各种界面条件（例如水泥套管、水泥岩石）的缩小样品，将用于分析井下应力条件的影响。该技术将与流经样品 3D 微观结构的地层流体流动的计算流体动力学模型相结合。总之，这种新方法将评估固井井筒部分的渗透率，这代表了井中潜在的微尺度泄漏路径。该项目提出的实验研究和数值模型研究将有助于更好地了解流体泄漏背后的驱动因素（即沿水泥/套管、水泥/钻孔界面和水泥体内微裂缝产生微通道的应力）。研究结果将有助于设计和开发新的、更可靠的屏障技术，这些技术可用于更具成本效益地减少无组织甲烷排放。作为泛加拿大清洁增长和气候变化框架的一部分，加拿大政府重申了到 2025 年将温室气体排放量比 2012 年水平减少 40-45% 的承诺。因此，拟议的研究与加拿大政府减少温室气体排放的战略方向完全一致。