(66d) A Critical Overview of Cause and Detection of Pipeline Blockages

Due to dramatic energy renaissance in US since 2010, more pipelines carrying crude oil and petroleum products are constructed to meet the gathering and transportation requirements. Blockage, however, can occur anywhere because of the depositions of wax, hydrate, paraffins and sand in pipes, and seriously affects the safety and reliability of transportation process. Therefore, it is imperative to detect the location and size of blockage in pipelines more accurately and efficiently to reduce the number of pipeline accidents.

Before any detection method is taken, it is important to make an appropriate assessment of the nature and severity of blockages, which can be mitigated or removed to avoid possible pipeline incident. Then selected inspections can provide accurate location of blockages. It is known that physical methods such as acoustic reflectometry, gamma-ray transmission scanning, radioisotope tracer injection, tomography measurement, radiographic detection, and pipeline diameter measurement can detect blockage accurately but with high cost/time consuming and necessary equipment or materials, while mathematical models used to detect blockage are at a relatively low cost and can monitor the pipeline continuously without interrupting pipeline operations but with less accuracy. Therefore, understanding of cause of blockage and the advantage/disadvantage of each detection method are crucial to selecting an appropriate method to detect blockage in a specific pipeline with a relatively low cost while could still meet the flow assurance requirement.

In this study, blockage nature is assessed in several aspects including fluid characteristic, blockage varieties and formation mechanism. Upon obtaining initial assessment of the blockage, the suitability of blockage detection method is studied for different fluids in a pipe of various layouts and operating conditions. By comparing the difference of detection methods, a systematic instruction is proposed to choose the right method for differentiating single blockage from multiple blockages and then estimating the location and size of blockage in different scenarios. Finally, it is found that mathematical method has the privilege to narrow down the possible blockage interval especially for long-distance pipeline, then physical method is used to locate blockage accurately and evaluate severity confidently.

Early information of pipeline blockage can improve the effectiveness and reliability of pipeline operating. This paper highlights the importance of assessing the nature of blockages correctly and focuses on developing best practice to detect the pipeline blockages in different scenarios. Furthermore, for the comparison of numerous detection methods, this study addresses a practical and systematic guideline that instructs how to select efficient and appropriate detection method, which also allow the operator to assess the risks and schedule remediation procedures efficiently and economically.