Critical condensate saturation, Scc, is a key parameter for the evaluation of well deliverability in gas condensate reservoirs. We propose a new method to determine Scc by performing three-phase flow simulations with three-dimensional (3D) pore network model. First, we establish a network model with random fractal methodology. Second, based on the condensation model in the literature of Li and Firoozabadi, we develop a modified condensation model to describe the condensation phenomenon of gas with connate water in the porous medium. The numerical model is verified by experimental measurements in the literature. Then, we investigate the influence of different factors on the critical condensate saturation, including micro pore structure (pore radius and fractal dimension), condensate gas/oil interfacial tension (IFT), and flow rate at different irreducible water saturation, Swi. The simulation results show that Scc decreases with increasing of average pore radius, but increases with increasing of fractal dimension. In the case of the same gas/oil interfacial tension, the higher the connate water saturation, the higher the critical condensate saturation. There is a critical gas/oil interfacial tension, below the critical value, the critical condensate saturation increases drastically with increasing of interfacial tension while it keeps almost unchanged when the interfacial tension is above the critical value. The critical condensate saturation decreases with increasing in the gas flow rate. High capillary number results in low critical condensate saturation. Reasonable increase in producing pressure drop can effectively improve the flow capacity of condensate oil.

The viscosity-temperature curve of Bi melt showed that the viscosity values deceased with the increase of temperature. However, the discontinuous changing pattern took place on the viscosity curve. Viscosity of Bi melt can be divided into three parts as high temperature zone, moderate temperature zone and low temperature zone according to its change rate with temperature. The temperature ranges of the abnormal viscosity change were about 400~430°C and 610~640°C. With the DSC analysis, the abnormal phenomenon was explored from the microscopic structure viewpoint. It was assumed that the change from inhomogeneous atom configuration to homogeneous one led to the discontinuous variation, which is related to the bond transformation with the increase of temperature in melt Bi.

No abstract

No abstract