Wax deposition is a severe flow assurance challenge that threatens waxy crude oil production and transportation. For wax remediation, pipeline pigging is the most widely used technique. However, the elusiveness of wax removal mechanism and the lack of reliable methods to evaluate wax breaking force and wax removal efficiency easily trigger pig stalling and wax blockage in field pigging operations. Modeling wax breaking force and wax removal efficiency, therefore, promotes the pigging confidence. This Review seeks to clarify the current picture of wax removal research in crude oil pipeline pigging. Relevant wax deposit properties including wax layer thickness and strength are discussed. Wax removal mechanisms are summarized from perspectives of wax–pig interaction, macroscopic force response, and scenarios with oil flow. Prediction models of wax breaking force and wax removal efficiency are analyzed comprehensively. Pig geometry optimization using this model is given. In addition, the key roles of wax deposit strength, viscoelasticity and thixotropy, foam pig investigation, and wax plug prediction are highlighted for guiding future endeavors in this area.

中文翻译：

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原油输送系统上管道清管作业除蜡的进展和未来挑战

蜡沉积是严峻的流量保证挑战，威胁着蜡质原油的生产和运输。对于蜡的修复，管道清管是最广泛使用的技术。但是，除蜡机理难以捉摸，并且缺乏评估除蜡力和除蜡效率的可靠方法，很容易在田间清管作业中触发清管器堵转和蜡阻塞。因此，对蜡的断裂力和除蜡效率进行建模可提高清管信心。本文旨在澄清目前原油管道清管中除蜡研究的现状。讨论了相关的蜡沉积性能，包括蜡层厚度和强度。从蜡与猪之间的相互作用，宏观力响应以及油流动情况的角度总结了除蜡机理。综合分析了破蜡力和除蜡效率的预测模型。给出了使用该模型的猪几何形状优化。此外，突出了蜡沉积强度，粘弹性和触变性，泡沫猪研究和蜡塞预测的关键作用，以指导该领域的未来工作。