Quantitative Modeling of Fluid Phase Evolution in Ordovician Reservoirs of the Shuntuoguole Area, Tarim Basin: Implications for Oil and Gas Phase Differentiation

The Shuntuoguole area has become an important oil and gas exploration replacement zone; however, the complexity of its ultra-deep oil and gas phase behavior poses a challenge to petroleum exploration and development. Previous research lacks quantitative modeling of the evolution of the oil and gas phase. In this paper, the phase characteristics, phase evolution processes, and main factors influencing phase differentiation in Ordovician reservoirs of three typical wells in the Shuntuoguole area were studied quantitatively by integrating PVT simulation and basin modeling. The results indicate that the difference in geothermal field between the Shunbei, Shuntuo, and Shunnan areas profoundly influences oil and gas phase differentiation. The Ordovician fluid in well SB5 has remained in the oil phase since the light oil accumulated during the Late Hercynian period. In well MS1, the Ordovician fluid briefly existed in a gas–liquid two-phase state after the light oil accumulated in the Late Caledonian period, then transformed into the liquid phase at 348 Ma and has maintained this state to the present. In the dry gas reservoir of well SN5, the fluid has remained in a single gas phase throughout all stages of reservoir temperature and pressure evolution after accumulation.