GAS

： Yufutsu gas condensate fi eld has a fractured reservoir which consists of conglomerate and granite. It contains condensate-rich gas. We observed some strange fl uid behaviors. Production gas oil ratio ranges from 900 m 3 /k l to 1,900 m l to 1,900 m l 3 /k l according to production area where reservoir depth is different. Gas production started l according to production area where reservoir depth is different. Gas production started l ten years ago. At the early stage of the production, gas oil ratio decreased with time. This trend is opposite from normal behavior of a gas condensate reservoir. Also, we observed that heavy gas existed on light gas in a tubing at a specifi c well. we The reservoir is approximately from 4,000 m and 1,000 m thick. pressure and temperature are varying in a wide range with the reservoir depth. Gas compositions at the top and the bottom of the reservoir are so different that the lightest component, tends to increase with depth and temperature due to the thermal diffusion because methane has larger thermal diffusion coeffi cient than the other heavier the uid behaviors. This paper reviews the above phenomena and the theory and reports current effort to increase condensate recovery using gas cycling scheme.