Uticaj utiskivanja gas-lift gasa na prenos mase i toplote

Abstract

Nakon uvođenja kontinualnog gas-lifta, primećen je porast proizvodnje tečnog naftnog gasa, TNG, u postrojenju za preradu gasa, kao jednog od finalnih proizvoda dobijenog iz fluida gaso kondenzatnih i rastvorenog gasa iz naftnih bušotina. Pretpostavljeno je da se prisustvom gas-lift gasa uspostavlja drugačija ravnoteža faza u odnosu na slučaj bez gaslifta, te da je gas-lift gas stripovao propan i butane iz tečne u parnu fazu, što je dovelo do povećanja prinosa TNG-a. Napravljen je model bušotine koja radi u kontinualnom gas-liftu primenom programskog paketa Aspen HYSYS v8.8. Pri modelovanju bušotine koja radi u kontinualnom gas-liftu uključeni su: tubing, unutrašnja cev, i kezing, spoljašnja cev; fluid proizveden iz bušotine; gas-lift gas; razmena toplote fluida u tubingu i gas-lift gasa, razmena toplote između gaslift gasa i okolne sredine (zemlje). Verifikacija modela urađena je poređenjem sa rezultatima karotažnih merenja, tzv. PLT, preko profila pritiska i temperature u stubu bušotine. Rezultati analize pokazali su da se razlika između merenih i vrednosti pritisaka/temperatura u stubu modelovane bušotine smanjuje povećanjem broja pojedinačnih cevi (cevnih segmenata) koje predstavljaju tubing/kezing. Na osnovu dobijenih rezultata zaključeno je da je porast prinosa TNG-a posledica promenjenih faznih odnosa i uslova prenosa mase i toplote kada se u bušotinu utiskuje gas-lift gas. Ispitan je uticaj gas-lift gasa na taloženje parafina. Rezultati ispitivanja pokazali su da taloženje parafina počinje na većim dubinama i da je količina istaloženog parafina veća u bušotinama sa gas-liftom.

More than expected increase of liquified petroleum gas, LPG, yield was observed after continuous gas-lift start up in the gas processing plant as one of the final products obtained from gas condensate and associated gas from oil wells. It was assumed that the presence of gas-lift gas leads to the establishment of a different phase equilibrium in comparison to the case without gas-lift, and that increase of LPG yield is the result of stripping propane and butane by gas-lift-gas from the liquid to the vapor phase. A model of the gas-lift well was prepared in Aspen HYSYS v8.8. This model included pipe in pipe segment, i. e. production tubing inside production casing, countercurrent flow of gas-lift gas and producing fluid, heat exchange between gas-lift gas and the surrounding ambient – ground; and gas-lift gas with the fluid in the tubing. The model verification was done by comparing the results of the PLT measurements, through the pressure and temperature profiles in the gas-lift well. The results showed that the difference between the measured and calculated pressure/temperature profiles is reduced by increasing the number of pipe segments. Based on the obtained results, it was concluded that the increase in LPG yield is a result of the changed phase equilibrium and the mass and heat transfer when the gas-lift gas is injected into the wellbore. Influence of the gas-lift on paraffin deposition was investigated. The results of the research have shown that the precipitation of paraffins begins at greater depths and that the amount of deposit is higher in the gas-lift well.