For long distance single-phase export pipelines, the normal wax control strategy is by sending regular cleaning pigs. The cleaning pigs will mechanically scrape off wax, or any other solid deposited on the pipeline wall, and remove water. This is to assure that there are no obstacles to flow and no corrosion. A key question for single-phase pipeline systems is: What is the minimum cleaning frequency required? This question can only be answered by an evaluation of the following issues where one parameter can alone be governing for the pigging frequency:
Equipment design (spares, valves, etc.)
Pig design
Single phase wax deposition predictions
Wax remediation (chemical, pigging, etc.)
Wax handling at receiving facilities
Evaluation of corrosion control strategy
Monitoring possibilities
This paper discusses the changes for operations with introduction of a light oil to an offshore heavy oil pipeline. The key success parameter to improve and optimize the existing wax control strategy has been to better utilize operational data together with update of simulations, fluid data and pig design. The result illustrates the importance of continuous monitoring and evaluation of consequences of changed operating conditions for safe and cost-effective operations.
In addition to wax control, this paper also discusses changes to flow regime where a low-pressure drop has been experienced compared to design.
The pipeline system is shown in Figure 1. The existing pipeline system (pipeline 2) is transporting stabilized oil with a gravity of 19°API to onshore receiving facility. In 2015 a new field was tied in to the existing pipeline system with a wye and a new pipeline of 43 km (26.7 miles).
