Energy Equation Derivation of the Oil-Gas Flow in Pipelines

Abstract

In the simulation of oil-gas pipeline multiphase flow, thermodynamic computation is an important process interacting with the hydraulic calculation and it influences the convergence of the program and the accuracy of the results. The form of the energy equation is the key to the thermodynamic computation. Based on the energy equation of oil-gas flow in pipeline, the Explicit Temperature Drop Formula (ETDF) is derived for oilgas steady state temperature calculation. This new energy equation has considered many factors, such as Joule-Thomson effect, pressure work, friction work and impact of terrain undulation and heat transfer Oil & Gas Science and Technology – Rev. IFP Energies nouvelles with the surroundings along the line. So it is an overall form of energy equation, which could describe the actual fact of multiphase pipeline accurately. Therefore, some standpoints in literatures on the temperature calculation of oil-gas two-phase flow in pipelines are reviewed. Elimination of temperature iteration loop and integration of the explicit temperature equation, instead of enthalpy energy equation, into the conjugated hydraulic and thermal computation have been found to improve the efficiency of algorithm. The calculation applied to both the component model, also applied to the black-oil model. This model is incorporated into the component model and black-oil model, respectively, and two simulations are carried out with two practical pipeline Yingmai-Yaha and Lufeng multiphase pipeline and the temperature results are compared with the simulation calculated by the OLGA and the measured. It is shown that this model has simulated the temperature distribution very well. Finally, we analyzed the influence of the specific heat capacity of oil and gas on the temperature of the mixture of fluids and the influence of the Joule-Thomson effect on the temperature distribution on the pipeline. It is shown that the Joule-Thomson coefficient is a key factor to well describe the oil-gas two-phase flow.