(591d) Optimization of Liquid Petroleum Products Pipeline Operations

Pipeline transportation of petroleum and petroleum products is the most common, economically viable, and reliable method for long distance transmission of liquid hydrocarbon commodities such as crude oil, petroleum products, and diesel fuel. Over the past century, considerable worldwide investments have been made in continental scale liquid pipeline networks. Given the contemporary dependence on hydrocarbons for meeting modern fuel demands for transportation, heating, and electrification, there is growing interest in modeling the behavior of these networks, including the physics of stationary [1] and non-stationary [2], [3] flows of incompressible fluid in pipelines, as well as engineering and control analysis of these complex systems [4], [5]. Here, we simplify these modeling complexities and incorporate them into a methodology that can be applied to reduce the energy consumption required to transport petroleum products through pipeline networks. This is achieved by minimizing the system-wide hydraulic resistance by optimizing petroleum pumping.

Liquid pipeline operations involve changes to the settings of pump stations that are used to maintain system pressure and actuate flow. Here, we formulate and solve a class of problems for optimizing liquid pipeline network operations. These involve minimization of energy used by pump stations or maximization of pipeline capacity utilization, subject to physical constraints that account for engineering limits on system pressures, flows, and temperatures, and operating constraints on pump station settings. The use of an adjustable pump drive as part of the automatic pressure control system in a pump station increases the control efficiency, and thus also liquid pipeline throughput [6]. The pump rotor speed can be adjusted by changing the frequency of motor shaft rotation, or alternatively by changing the rotation frequency of the pump rotor given a constant motor shaft rotation frequency. To regulate the operating pump modes by varying the rotor speed, an adjustable electric drive can be used. Here we utilize engineering models of frequency-regulated electric drive pumps [7], [8], which have complex nonlinear dependence on the physical variables of fluid flow through a pump station and fluid properties. These complicated models, which specify constraints on the ability of pump stations to actuate liquid flow throughout a pipeline network, are simplified here to essential dependencies that are incorporated into constraints that yield well-posed (quasi-convex) non-linear optimization formulations. The reduction in frictional losses of momentum caused by turbulent flow are thus minimized [9], which increases the efficiency of pipeline transportation.

We present the application of our optimization approach using computations for a case study for a pipeline of 516 km length with 5 pump stations, each of which utilizes several rotating electric-drive pumps. Our study demonstrates that, when the capacity of the system is restricted to 900 m³/h at the terminal, optimization of pump frequency regulation yields an increase in equivalent transfer efficiency over nominal settings. Optimization of liquid pipeline operations subject to engineering constraints will enable improvements in system resilience in several key ways. Liquid pipeline system settings are typically configured given the design topology. Trusted optimization of such settings would allow automatic re-configuration of system operations in the case of unexpected component outages. Such formulations would also aid in analysis of logistics of multi-commodity transport, and could be extended to optimal system expansion planning analysis with the addition of economic cost information.

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[2] M. H. Chaudhry. “Applied hydraulic transients.” Technical report, Springer, 1979.

[3] A. R. D. Thorley. “Fluid transients in pipeline systems.” ASME Press, 2004.

[4] G. Z. Watters. “Modern analysis and control of unsteady flow in pipelines.” 1980.

[5] A. R. D. Thorley and K. J. Enever. “Control and suppression of pressure surges in pipelines and tunnels.” CIRIA, 1979.

[6] A. A. Korshak and Y. M. Muftahov. “Technology calculation of the main oil pipeline.” Ufa: DizaynPoligrafServis, 2005. (in Russian)

[7] A. P. Grishin, and V. A. Grishin. “The efficiency of frequency-regulated electric pump.” Automation and Informatization of electrified agricultural production: Scientific papers, 89:118–127, 2004. (in Russian)

[8] V. A. Shabanov, O. V. Bondarenko, and Z. Kh. Pavlova. “Definition of the location of variable frequency drive in the pipeline technological plot.” Problems of collection, processing, and transport of petroleum and petroleum products, 89(3):93–95, 2012. (in Russian)

[9] A. Y. Lipovka and Y. L. Lipovka. “Determining hydraulic friction factor for pipeline systems.” 2014. (in Russian)