A new pure membrane separation technology for CO2 and light hydrocarbons from oilfield associated gas
In the process of oilfield development,a large amount of CO2 which is used for oil recovery and produced along with the production of crude oil and light hydrocarbons(C2-C5)are discharged directly,which not only wastes resources but also pollutes the environment.Obviously,it is not in line with the environmental protection concept of CO2 flooding,so it is imperative to recover CO2 and high value-added light hydrocarbons.In this paper,the changes in the compositions of the associated gas after the construction of a CO2 capture,utilization,and storage(CCUS)demonstration area are analyzed.Based on this,polyvinylamine(PVAm)membrane and polydimethylsiloxane membrane are selected to conduct laboratory separation experiments on CO2 and light hydrocarbons in associated gas.Then,PRO II software is used to simulate the overall process of associated gas separation and carry out optimal process design and trial device production.Finally,the applicability of the membrane technology to separate CO2 and light hydrocarbons from oilfield associated gas in oil fields is clarified,and on-site tests are conducted.And the following research results are obtained.First,as CO2 is injected into the CCUS demonstration area,it has a certain extraction effect on the light hydrocarbons in the formations while leading to a gradual increase in the compositions of light hydrocarbons.Therefore,it is imperative to recover produced CO2 and high value-added light hydrocarbons.Second,PVAm has a strong promoting effect on CO2 transfer,with CO2 concentration,temperature,and humidity as the main influencing factors.The two-stage separation rate of CO2 reaches 90%.Third,polydimethylsiloxane membrane has good selectivity for light hydrocarbons,and the higher the carbon value,the better the selectivity.Pressure ratio and temperature are the main influencing factors,and the highest separation rate can be up to 70%.Fourth,these two kinds of membranes are excellent in long-term operational stability,confirming the membrane method's ability to separate CO2 and light hydrocarbons.Fifth,during the 600 hours of the on-site test,the experimentally produced skid-mounted membrane separation device ran smoothly,with the separation effect basically consistent with laboratory test and numerical simulation results.In conclusion,the use of pure membrane method to separate CO2 and light hydrocarbons from oilfield associated gas is advantageous with low investment,low energy consumption,energy conservation and environmental protection,and has the potential for long-term application.
CO2 floodingPolyvinylamine(PVAm)membranePolydimethylsiloxane membraneOilfield associated gasMembrane separationCO2 separationHydrocarbon separation
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