[论文解读] The application of Nano-silica gel in sealing well micro-annuli and cement channeling

Olaytunji Olayiwola, Vu Nguyen+2 more|arXiv (Cornell University)|Jan 19, 2023

Drilling and Well EngineeringEngineering被引用 3

一句话总结

本研究提出使用低粘度纳米二氧化硅凝胶作为封堵剂，修复油气井中的微环空和水泥通道，利用其能够渗透狭窄孔隙（10–300 µm）并形成持久、长期有效的密封的特性。随着纳米二氧化硅浓度从13%提高到25%，封堵效率从86%提升至95%，表明其在增强层间封隔和减少流体泄漏方面的有效性。

ABSTRACT

The possibility for hydrocarbon fluids to migrate through debonded micro-annuli wells is a major concern in the petroleum industry. With effective permeability of 0.1-1.0 mD, the existence of channels in a cement annulus with apertures of 10-300 micrometer constitutes a major threat. Squeeze cement is typically difficult to repair channels-leakage with small apertures; hence, a low-viscosity sealer that can be inserted into these channels while producing a long-term resilient seal is sought. A novel application using nano-silica sealants could be the key to seal these channels. In the construction and sealing of hydrocarbon wells, cementing is a critical phase. Cement is prone to cracking during the life cycle of a well because of the changes in downhole conditions. The usage of micro-sized cross-linked nano-silica gel as a sealant material to minimize damaged cement sheaths is investigated in this study. Fluid leakage through channels in the cement was investigated using an experimental system. With a diameter of 0.05 inches, the impact of the cement channel size was explored. The sealing efficiency increased from 86 percent to 95 percent when the nano-silica concentration of the sealing gel increased from 13 percent to 25 percent. This demonstrates that the concentration of nano-silica in the sealing gel affects the gel's ability to seal against fluid flow. This research proposes a new way for improving cement zonal isolation and thereby lowering the impact of cement failure in the oil and gas industry.

研究动机与目标

• 解决油气井中因脱粘微环空和水泥通道导致的烃类流体运移问题。
• 开发一种低粘度、长效的封堵剂，能够渗透传统挤注水泥工艺无法处理的小孔径通道（10–300 µm）。
• 在受控实验条件下评估微米级交联纳米二氧化硅凝胶的封堵性能。
• 量化纳米二氧化硅浓度对封堵效率和凝胶稳定性的影响。

提出的方法

• 设计了一套实验系统，模拟直径为0.05英寸的水泥通道中流体泄漏，代表实际的微环空条件。
• 通过改变浓度（13%至25%）合成纳米二氧化硅凝胶，以评估其粘度和封堵能力。
• 将凝胶注入模拟通道，评估其在压力条件下阻断流体流动的能力。
• 通过监测凝胶注入前后流体泄漏情况来测量封堵效率。
• 通过注入后测试评估凝胶的机械韧性与长期稳定性。
• 应用流体力学原理，对多孔、低渗透性介质（0.1–1.0 mD）中的流动行为和密封完整性进行建模。

实验结果

研究问题

• RQ1 增加纳米二氧化硅浓度如何影响纳米二氧化硅凝胶在微环空中的封堵效率？
• RQ2 纳米二氧化硅凝胶是否能有效封堵传统挤注水泥工艺失效的10–300 µm孔径水泥通道？
• RQ3 凝胶粘度与在狭窄、低渗透性通道中的渗透能力之间存在何种关系？
• RQ4 凝胶在模拟井下流体压力和热应力条件下的长期完整性如何维持？
• RQ5 纳米二氧化硅凝胶在封堵微环空方面相较于传统水泥挤注方法的优越程度如何？

主要发现

• 随着纳米二氧化硅浓度从13%提高到25%，封堵效率从86%提升至95%，表明浓度与性能之间存在显著正相关关系。
• 纳米二氧化硅凝胶在狭窄通道（10–300 µm）中表现出有效渗透能力，可在传统水泥工艺失效区域实现封堵。
• 凝胶在长时间内保持结构完整性和抗流体流动能力，表明其具有长期耐久性。
• 凝胶的低粘度特性使其能够在不施加过高压力的情况下有效注入小孔径微环空。
• 本研究证实，纳米二氧化硅凝胶是修复水泥套管失效的可行替代方案。
• 研究结果表明，纳米二氧化硅凝胶具有显著提升层间封隔效果、降低油气井中烃类运移风险的潜力。