Experimental research of condensate blockage and mitigating effect of gas injection

The condensate blockage causes a substantial decrease in well productivity for gas condensate reservoirs.Based on the previous studies,a novel experimental method was designed to evaluate condensate blockage and the mitigating effect of gas injection.The method considers the stacking effect in the near wellbore region and the gas flow in the far wellbore region.There is an intermediate vessel containing condensate gas at the entrance of core holder in the experimental apparatus.In the process of pressure depletion experiment in a long core model,the vessel is connected to the core and the pressure of the vessel remains above the dew point pressure.The seriousness of condensate blockage is investigated by this research.When pressure drops to maximum retrograde condensation pressure,the gas permeability decreases by 80%compared with the initial gas permeability.Contrastive experiments were conducted to study the removal effect of different injection fluids and different injection volumes.The results show that CO2 injection is more effective than methanol in mitigating condensate blockage and the optimal CO2 injection volume is around 0.15 HCPV。

Effect of a synthesized anionic fluorinated surfactant on wettability alteration for chemical treatment of near-wellbore zone in carbonate gas condensate reservoirs

The pressure drop during production in the near-wellbore zone of gas condensate reservoirs causes condensate formation in this area.Condensate blockage in this area causes an additional pressure drop that weakens the effective parameters of production,such as permeability.Reservoir rock wettability alteration to gas-wet through chemical treatment is one of the solutions to produce these condensates and eliminate condensate blockage in the area.In this study,an anionic fluorinated surfactant was synthesized and used for chemical treatment and carbonate rock wettability alteration.The synthesized surfactant was characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis.Then,using surface tension tests,its critical micelle concentration(CMC)was determined.Contact angle experiments on chemically treated sections with surfactant solutions and spontaneous imbibition were performed to investigate the wettability alteration.Surfactant adsorption on porous media was calculated using flooding.Finally,the surfactant foamability was investigated using a Ross-Miles foam generator.According to the results,the synthesized surfactant has suitable thermal stability for use in gas condensate reservoirs.A CMC of 3500 ppm was obtained for the surfactant based on the surface tension experiments.Contact angle experiments show the ability of the surfactant to chemical treatment and wettability alteration of carbonate rocks to gas-wet so that at the constant concentration of CMC and at 373 K,the contact angles at treatment times of 30,60,120 and 240 min were obtained 87.94°,93.50°,99.79°and 106.03°,respectively.However,this ability varies at different surfactant concentrations and temperatures.The foamability test also shows the suitable stability of the foam generated by the surfactant,and a foam half-life time of 13 min was obtained for the surfactant at CMC.