Packing and Drafting in Natural Gas Pipelines

Abstract

Summary Increasing and decreasing natural gas pipeline inventory (" packing" and "drafting" ) are examined mathematically. Any line segment's unsteady-state packing or drafting behavior depends on only two dimensionless parameters, packing or drafting behavior depends on only two dimensionless parameters, ( ) and ( ). The influence of ( ) is small, so that for any value of ( ) the behavior of all pipelines can be represented on a single plot; four such plots are shown for four different boundary conditions. Introduction Natural gas dispatchers use increase and decrease of the stored inventory of gas in their pipes as one method of matching time-varying demands with supplies, which generally have less time variation. In pipeline terminology, increasing the inventory (and hence the pressure) is called "line packing," while decreasing it is called "line drafting." This paper examines the limits of this procedure, asking both how much gas can be added to or subtracted from the inventory in a given pipeline segment, and how rapidly this can be accomplished. How Rapidly Can the Inventory Be Depleted or Restored? Although the questions of how large the inventory is and how much can be taken from it for any change in steady-state conditions can be answered very simply, the computation of how rapidly this can be accomplished requires a set of coupled partial differential equations and a numerical solution on a computer. Fortunately, as shown here, the nondimensional results can be summarized in ways that are fairly easy to use. Mathematical Theory It has been known since at least 1951 that the mathematical description of the unsteady-state flow of any gas in a long pipeline is governed by a material-balance equation, ............................(1) and a momentum-balance equation, ............................(2) The mass-balance and momentum equations, expressed with pressure, and mass flow rate, as dependent variables and length, and time, as independent variables and assuming that 's are much smaller than 's and ( / )'s, are ............................(3) and ........................... (4) respectively. The justification for dropping the terms as being much smaller than the others is that changes very slowly with changes in and other variables. JPT p. 655

Towards future infrastructures for sustainable multi-energy systems: A review

“…This is done by increasing the gas pressure, using an upstream compressor and closing a downstream valve. The linepacking issue has been studied in decades by using mathematical programming, as done in [89,90]. Optimization of line-packing is discussed in [90][91][92]; this allows evaluating the best timetable and pressures of compressor stations.…”

“…Optimization of line-packing is discussed in [90][91][92]; this allows evaluating the best timetable and pressures of compressor stations. Limits of the line-packing and for a single pipeline are discussed in [89] by considering the aim of matching variation of demands and supplies. In [93], a model for the optimal control problem of large-scale gas systems is proposed, also taking into account line-packing in modelling.…”

Linepack planning models for gas transmission network under uncertainty

“…From the mathematical programming perspective, some approaches to linepack problems are oered in De Nevers and Day (1983), Carter et al (2003), Krishnaswami et al (2004), Abbaspour et al (2007), Midthun (2007), Krishnaswami and Haugland (2008) and Borraz-Sanchez (2010). De Nevers and Day (1983) examine the ability of inventory of gas in pipeline networks to satisfy time-varying demands with supplies in a transient-state gas transmission system. The authors conduct a model on two dimensionless parameters for packing and drafting behaviours.…”