Modular tool for design and off-design analysis of compression trains for oil and gas applications

Compression trains for oil and gas applications must meet, now more than ever, the requirement of versatility. Production rates and compression demands of extraction fields significantly change during their operational life; this has pushed customers to ask for equipments designed to efficiently operate all over their lifespan in order to comply with energy saving and pollution reduction needs. For this reason modular simulation codes turn out to be the best choice compared with dedicated tools for specific compression plant configuration, since they provide flexibility without losing accuracy. This paper presents the implementation, within a previously developed modular tool, of a design and off-design procedure for compression plant simulation. This tool is based on a wide library of elementary components analytically defined through equations that model their physical behaviour. For impellers, descriptive equations represent an in-house database of real stages characteristic curves, for all the other elementary components the equations arise from fundamental mechanical and thermodynamic laws. Physical properties of real gases are assessed by the use of suitable thermodynamic libraries. An implemented trust-region Gauss-Newton method, called TRESNEI, has been adopted to solve the mathematical model. Numerical calculations, performed on two real compression train arrangements, have been devoted to validate the code over design and off-design simulation mode. Results have been compared with those obtained with a pre-existing in-house tool and with experimental data. Comparisons show both a satisfactory agreement between numerical and experimental data and a perfect matching between the simulation codes