Abstract
Wax deposition occurs frequently in waxy crude oil pipelines when the level of flow decreases, and pigging is needed at regular intervals. An economic pigging model is established in accordance with the objective function based on the sum of thermal costs, power costs, and single piping costs. Thus, by compiling a program, the most economical pigging cycle will be determined. Furthermore, the calculation methods for hydraulic and thermal constraints are given. Taking the example of the distance between the central processing platform and the land terminal external piping line of the M-field cluster, the effects of different inlet temperatures, throughput, and remnant wax thicknesses on the economic pigging cycle will be analyzed. The results show that with an increase in the inlet temperature, the total costs of the pipeline operation increase, while the pigging cycle will prolong. As throughput increases, total costs will decrease, while the pigging cycle also extends. When throughput is fixed, a remnant wax thickness of 0.4 mm helps reduce the total operating costs of the pipeline at different inlet temperatures. While throughput varies, a remnant wax thickness from 0.2 to 0.4 mm can reduce total costs at a fixed inlet temperature.
Highlights
According to incomplete statistics, China National Offshore Oil Corporation has laid 315 submarine pipelines in China’s seas, with a combined length of approximately 6202 km.[1]
Waxy crude oil solidifies when exposed to certain range of low seabed temperature,[3] resulting in the reduction of circulation area, growth of flow stream friction, and a reduction in the delivery capacity of the pipe, significantly increasing risks in the delivery capacity of the pipe.[4]
It is obvious that while calculating the total cost of the pipeline operation, we should figure out the effect that the thickness of wax has on both, power and thermal.[7]
Summary
China National Offshore Oil Corporation has laid 315 submarine pipelines (with diameters from 50.8 to 762.0 mm) in China’s seas, with a combined length of approximately 6202 km.[1]. It is obvious that while calculating the total cost of the pipeline operation, we should figure out the effect that the thickness of wax has on both, power and thermal.[7]. S Zhou et al.[11] considered the influence of remnant wax thickness and established an optimal pigging cycle model with two independent variables, namely, paraffin cycle and the remnant wax thickness All these pigging models cared only about the economic issue of the pigging cycle, while ignoring the impact of the decline in pipeline delivery capacity on the safe operation of the pipeline. Under the premise of ensuring the safe operation of the pipeline, the economic pigging cycle of an actual pipeline is determined These findings can serve as a reference for the formulation of pigging programs and the reduction of oil transportation costs. The specific model is shown in equation (19), and the wax thickness d is obtained based on the actual parameters of the pipeline:
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
