Study On Phase Behavior And Influencing Factors Of Condensate Gas In Porous Media

The current condensate gas phase behavior experiments are mostly carried out in PVT cells without porous media;similarly,the mature condensate gas phase calculation method is based on the presume that the fluid properties and phase transformation mechanism of the condensate gas are not affected by the porous media.In fact,the storage and phase transformation of condensate gas occurs in the porous media of the reservoir.In view of whether the porous media will affect the phase change process of the condensate gas,many scholars have conducted a lot of research,but their understanding is different.Therefore,it is necessary to clarify the influence of porous media on the characteristics of abnormal condensate gas condensate process and analyze its influencing factors.The corresponding phase state calculation method should be established.In this thesis,a simulated condensate gas system was designed and used in the CCE&CVD experiments.At the same time,the CMG-Win Prop module was used to fit and expand the experimental results to obtain the retrograde condensate characteristics of this system without porous media.Then,two different sand tube models were used to conduct the depletion experiment to study the retrograde condensate characteristics of the system in porous media.By comparsion and analysis,the influence of porous media on abnormal condensate characteristic was observed,and the mechansims of the influence factors were analyzed.On the basis of above,the adsorption process was described by FHVSM model,and the influence of capillary pressure was calculated separately in two stages;Combined with PREOS,the calculation model for the retrograde condensate characteristics of condensate gas in porous media was established.Through the above work,the existence of porous media will affect the retrograde condensate characteristics of condensate gas:(1)The porous media will increase the dew point pressure of the condensate gas system;More condensate will precipitate and more condensate will remain in the pores.(2)The porous media mainly affects the abnormal condensate characteristics by adsorption and capillary effect.Porous media has a large specific surface for adsorption under high temperature and high pressure,affected by gas adsorption the gas composition will change and affect the retrograde condensation.For capillary effect,the smaller average pore radius,the more difference between the retrograde condensate characteristics in the porous media and in the PVT cells.(3)Using the model established in this thesis,the dew point pressure and the CVD process of a 6-component simulated condensate gas system is calculated.Comparing the calculation results with the results without the influence of the porous media,the conclusion is consistent with the experimental results,it confirms that the porous media increases the dew point pressure as well as the saturation of the condensate liquid increased during the depletion process.