Objective With the accelerated implementation of carbon peaking and carbon neutrality strategies, the consumption mix of traditional oil and gas resources has undergone significant changes, reflected in a slowing growth rate of oil and gas demand and a decline in the average annual utilization rate of existing oil and gas pipelines. In this context, batch transportation through product oil pipelines is considered an effective solution for the long-distance and large-scale transportation of methanol, which is a key enabler of the green and low-carbon transformation in the energy sector. Furthermore, this approach can revitalize many idle pipeline assets or those operating at low loads, thereby increasing the overall utilization rate of pipeline facilities. However, there is limited engineering experience in the batch transportation of methanol via product oil pipelines, both in China and abroad, and relevant research remains inadequate. Moreover, significant differences in the physical and chemical properties between methanol and product oil present challenges to the batch transportation process. These challenges include material compatibility, the applicability of key equipment and facilities, oil mixing mechanisms and control, operational safety assurance, pipeline design, and the establishment of standards and specifications.

Methods This paper analyzes the current status of development in the field of batch transportation of methanol through product oil pipelines, identifies the core scientific and technological challenges associated with using these pipelines for batch methanol transport, and presents prospects for future research along with recommendations for development.

Results First, material compatibility is recognized as one of the core challenges. Metallic materials, such as carbon steel and aluminum alloys, are susceptible to corrosion and stress corrosion cracking in environments containing impure methanol. Meanwhile, non-metallic sealing materials, such as fluororubber, face a significantly higher risk of swelling failures in methanol environments compared to product oil environments. Second, adaptability analysis and targeted modifications are essential for key equipment and facilities. This involves evaluating the adaptability of product oil storage tanks, including anti-corrosion coatings, nitrogen sealing systems, explosion-proof designs, and operation and maintenance systems, as well as assessing the adaptability of product oil pumps in methanol transportation environments, including materials, sealing structures, cavitation, and oil mixing control. Additionally, it is crucial to address various issues related to valves, including material compatibility, sealing reliability, and safety protection design. Third, the mechanisms and control of oil mixing are identified as challenging aspects, underscoring the need for a full-chain technological system that encompasses the mechanisms, prediction, control, and processing of oil mixing. It is also essential to systematically study the evolution patterns of leakage and diffusion of methanol transported in batches through product oil pipelines. This research aims to clarify the characteristics of developments that could lead to accidents and facilitate the creation of techniques for operational safety prevention and control, as well as emergency response.

Conclusion Building on these research efforts, there is an urgent need to implement engineering demonstrations, as well as to establish and improve the standards and specifications for the batch transportation of methanol through product oil pipelines. This will provide theoretical support and practical guidance for transitioning product oil pipelines in China to low-carbon functionality and enhancing asset utilization efficiency.