Abstract: Pubei oilfeld is the first oifield recovered by gas injection miscible process in China. The project of gas injection miscible flooding is one of the critical tasks proposed in the Ninth Five-Year Plan” of the state. Since putting into production by gas injection process in 1998, stable production has been maintained at present in the whole oilfield with recovery rate of 5.6%,current recovery percent of 15.74% and composite water cut of zero,,achieving remarkable results for development. This paper studied the variation of fluid property since gas-injection production and numerical simulation results, showing that current gas-injection blocks in this oilfield have reached requirements of the miscible phase project design. It will provide significant guide for oilfields, especially for those having high gasoil ratio in westerm China developed by abundant associated gas or gas-injection miscible phase process.

Key words: Turpan basin, Hami basin, Pubei oilfield, gas injection, miscible flooding, fluid, PVT