Abstract:

At periphery of Daqing placanticline, there is 3×10⁸_treserves from extra-low permeability Fuyang layer which is difficult to produce effectively through water flood development. For producing these reserves effectively, an CO₂ immiscible displacement experiment is developed. PVT testing result indicates that crude oil of Fuyang reservoir is high-viscosity, low volume factor, low expansibility and contractility, and low dissolubility. At CO₂ displacement capillary experiment, the lowest miscible pressure is 29 MPa, which is 8.6 MPa higher than original formation pressure and shows that is an immiscible displacement experiment. Long core experiment showsCO₂ immiscible displacements get 4%-6% more recovery efficiency than water displacement. Above laboratory feasibility tests indicate that CO₂ immiscible displacement experiment is workable at Fuyang reservoir. At the beginning of 2003,  theCO₂ gas injection pilot area was built at the south of Songfangtun oilfield. There are 1 gas injection well and 5 production wells. The field test shows that CO₂ immiscible displacement can build an effective drive system at extra-low permeability and less fracture Fuyang reservoir, and improve its development effect. This technology is hopeful to be a workable one for producing Fuyang extra-low permeability layer effectively.

Key words: extra-low permeability,  Fuyang layer, CO₂ immiscible displacement, experimental study, placanticline, Daqing