WU Lei; YUAN Shiyi; HU Yongle; LIU Henian and LI Haiping
, 2004, 31(2): 817-0.
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The liquid phase often condenses in the reservoir when the fluid pressure drops below the dew point pressure. The condensate often remains as an immobile phase in the porous media with low recovery because the saturation point of liquid condensate is usually less than that of the critical condensate and the mobility effect occurs due to larger viscosity of condensate. Due to the effect of phase equilibria, the reservoir fluid may exhibit one, or a combination, of the following three types of vaporization: ① the re-vaporization of condensate, when the pressure is below the maximum condensation pressure, ② the equilibria revaporization due to the extraction effect of lean gas during gas injection, ③ the retrograde vaporization of condensate, when the reservoir pressure builds up as a result of more voids being replaced by injected gas. With pressure depletion, the liquid volume will be reduced continuously. For rich gas condensate reservoirs, due to the component exchange between the injection gas and the condensed liquid, the re-vaporization is obvious. The tests show that the lean gas can vaporize the intermediate as well as the heavier fraction such as C20+. In the natural reservoir, under the condition of high injection-production ratio, the composition of heavy components will increase and the heavy components can be extracted to the surface through partial vaporization.