Calculating densities and viscosities of natural gas with a high content of C_(2+) to predict two-phase liquid-gas flow pattern

The paper is devoted to the two-phase flow simulation.The gas-condensate mixture flow in a horizontal pipe under high pressure is considered.The influence of the equation of state(EOS)choice for mixture properties modelling on the flow regime calculation results is studied for gas with high content of methane homologues.An analytical overview of the methods to predict the flow pattern is provided.Based on this analysis,two techniques are selected.For these techniques,values of density and viscosity for each phase are required.Density calculation for the gas phase is performed with Van der Waals based EOS.The propriate EOS is selected based on studies of calculation errors for test mixtures.Calculation of liquid phase density is done by means of Patela-Teja and Guo-Du equations,two different models are considered for viscosity estimation.The flow patterns of gas-condensate mixture in a range of temperatures and pressures are calculated and verified via probability map.The results of study allow to recommend the Brusilovsky EOS for calculation of densities for similar gas mixtures and make more rigorous flow regime evaluation.The probability map shows that for the chosen composition and parameters of media the flow pattern is mostly transitional between segregated and annular independent from EOS.

Energy efficiencies and CO_(2)emissions associated with lowtemperature separation technologies for the processing of formation fluid from the Achimov deposits

Three different technologies for the low-temperature separation(LTS)of gas condensate from the Achimov deposits in the Russian Urengoyskoe gas and condensate field were assessed using exergy analyses.The options examined included turbo-expansion and ejection.Thermomechanical exergy values were calculated for material streams and exergy losses and efficiencies were estimated for dedicated equipment used in the LTS.The lowest exergy loss of 4221.2 kW was obtained using turboexpansion and electricity cogeneration.The carbon release associated with each scenario was calculated while considering different production rates,technological parameters and natural decreases in wellhead pressure.The integral carbon footprint after 40 years of LTS operation was estimated for all cases.A classical ejector-based LTS scheme was shown to produce 1200 t of CO_(2)emissions over 40 years of operation.This same scheme combined with a turboexpander and electricity generator produced 59%less CO_(2)in the same period.An expansion-cogeneration LTS scheme was found to be the most effective and ecologically friendly among the various options based on this analysis.