古龙页岩限域空间的原位相态与组分变化特征OA

Gulong shale in Songliao Basin is a pure shale-type reservoir,with storage space dominated by pores with pore size of tens of nanometers and micro-fractures.Fluids in these nano-scale pores and fractures exhibit complex phase behavior due to the confined space effect,and phase transition and component migration during depressuriza-tion development remain unclear.By establishing a confined fluid phase calculation model,the in-situ phase char-acteristics of Gulong shale are clarified.A developed constant composition expansion(CCE)experimental simula-tion software is applied to quantify composition variation in pore fluids with different pore sizes,finally establishing a multi-scale spatial shale oil phase transition model for depressurization development.The results show that,com-pared to bulk fluids,the bubble/dew points of confined fluids decrease significantly.As pressure decreases,light components preferentially migrate with significant amounts of C2-5 and C6-10 released into the gas phase,while heavy components are retained in nano-pores as undersaturated fluids.Methane is continuously released.This simulation results are consistent with the trend of oil and gas composition monitoring results from Well GYP1.During the devel-opment process,macropores maintain a black-oil state,mesopores(weak confinement)transition from volatile to black-oil state,and micropores(strong confinement)evolve from condensate to volatile and then to black-oil state.The research reveals the in-situ phase characteristics of micro-nano pores and component migration patterns during depressurization development,clarifying multi-scales spatial phase transition pattern during development process and providing theoretical guidance for understanding the original occurrence state and reasonable and effective de-velopment of shale oil reservoirs.