This subject is always present when designing a gas pipeline that requires compressor stations to optimize the transportation and also capital and operation costs. On the Bolivia-Brazil gas pipeline project original design the technical economic analysis, thermo-hydraulic studies and failure analysis determined a selection of a parallel arrangement for the fourteen (14) compressor stations with four (4) 7000 hp ISO gas turbines per station. The project schedule considered the installation of three (3) initial compressor stations that were necessary for three (3) years of operation. With more accurate information from market development, transportation contract ramp up changes and the experience acquired from the original design a new set of studies were done. The results obtained allowed a better understanding of compressor station operation and also allowed the selection of the size and arrangement of units to be adopted for the expansion. The new studies considered bigger turbocompressors with series and parallel arrangement and electric driven compressors as an alternative for the project since there is an electric transmission line parallel to the gas pipeline in Brazilian side. The optimization study proved series arrangement to be a better solution for the configuration with electric driven compressor taken benefit of the driver sizing and speed. Economics aspects including capital cost, although considered in detail for the Bolivia-Brazil gas pipeline project, will not be addressed in this paper because of their particularities in terms of logistics, market competition and labor costs that will vary differently depending on the location of the project. The purpose of this paper is to underline the need to simulate different sizes and arrangements for compressor station units and not selecting a off-the-shelf solution that might not be the best one in terms of capital investment, fuel usage and optimal energy management. The simulation tool used to perform all the simulation analysis for the Bolivia-Brazil expansion project was PipeLine Studio 1.2 from Lic Energy. This paper adds more information over the previous one presented on the PSIG Annual Meeting of 1997 entitled "Transient Analysis - A Must in Gas Pipeline Design".

1 Introduction

The Bolivia-Brazil Gas Pipeline project required a capital investment of around US$ 2 billions. Natural gas is taken from proved and probable Bolivia reserves of around 23.37 TCF (0.66 trillions of cubic meters) to the Brazilian market in expansion. The gas pipeline started operation on July 1st 1999 for the northern leg with DN 32" and 1127 miles (1813 km), from Rio Grande, Bolivia up to the city of Campinas in the state of São Paulo, Brazil. The southern leg, with diameters varying from DN 24" to 16" and with 683.5 miles (1100 km), goes from Campinas to the city of Porto alegre in the south of Brazil that started operation onMarch 21st 2000.

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