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.

甲烷是一种强有力的温室气体（GHG），比二氧化碳强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，占全国甲烷排放总量的44%。在上游石油和天然气工业中，甲烷排放的很大一部分是由表层套管排气流（SCVF）和气体运移（GM）引起的逃逸泄漏造成的。 散装水泥以及水泥/套管和套管/岩石界面可能是油气威尔斯井在泄漏和长期井完整性方面的薄弱点。水泥与套管和/或地层的脱粘以及随后的层位隔离损失是油气威尔斯井中SCVF和GM的逃逸性甲烷排放的重要原因。 无论威尔斯井是在生产还是堵塞和废弃，了解泄漏通道形成的机理对于评估和改善油气井威尔斯的水泥性能至关重要。因此，提出了水泥破坏和脱粘机制的全面实验和数值研究，以及这些如何影响流体通过水泥微观结构的运动。 能够在实际井下条件（即43 MPa和120 °C）下研究通过水泥井段的流动的高级井筒模拟器将用于研究水泥体的完整性，以及在代表性井下应力条件（即，循环压力和热应力条件）。模拟水泥体和各种界面条件（例如，水泥-套管、水泥-岩石）将用于分析井下应力条件的影响。该技术将与通过样品的3D微观结构的地层流体流动的计算流体动力学建模相结合。总之，这种新方法将评估水泥井段的渗透率，这代表了井中潜在的微尺度泄漏途径。本项目中提出的实验研究和数值模型研究将有助于更好地理解流体泄漏背后的驱动因素（即应力沿水泥/套管、水泥/井眼界面和水泥体内的微裂缝沿着形成微通道）。研究结果将有助于设计和开发新的、更可靠的屏障技术，可用于以更具成本效益的方式减少易散性甲烷排放。作为《泛加拿大清洁增长和气候变化框架》的一部分，加拿大政府重申其承诺，到2025年将温室气体排放量减少到2012年水平的40-45%。因此，拟议的研究与加拿大政府努力减少温室气体的战略方向完全一致。