Pipeline Pigging for Flow Assurance Issues in an Onshore Gathering System
(Room Conference Hall)
05 Apr 18
9:30 AM
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11:00 AM
Pigging is an important operational procedure performed on multiphase pipelines to maintain flow efficiency in oil and gas pipelines when liquids are present. It is important during operating a gas condensate or liquid dominant system to restrict the liquid inventory in the pipeline below the capacity of the slug catcher and maintain pipeline pressure drops for continuity in operations. Inspection pigs and Maintenance pigs has long been used as a tool for solids deposition control and corrosion monitoring and control. For the case study to be illustrated in the paper, in general for summer conditions, minimum liquids will condense and pigging may not be necessary. In winter, ambient temperature is lower and the pipeline can be expected to be cooler. Therefore, water and hydrocarbon condensate is expected to condense in the pipeline depending on the combination of temperature and pressure experienced in the system. Under condensing conditions, liquids will accumulate in the line until they could: 1) cause inefficient slug flow, 2) cause corrosion, and 3) surpass the capacity of the slug catcher at the end of the line. For instance, for the 30” pipeline, liquids will accumulate at a rate of about 1 Bbl/d. After about two months, there will be over 60 bbls liquids in the line, or more than half of the slug catcher capacity of 100 bbls. Therefore, this line should be pigged about once every two months in winter. The paper and presentation will further demonstrate benefits and scenarios when pigging should be considered and when it is critical to the operation of a pipeline gathering system where the pipeline maybe transporting fluids from different sources.