Study on high-periodic steam soak technique of heavy oil in thin-bedded layers

The heavy oil reservoirs of Henan Oilfield are characterized by shallow, thin, viscous and dispersive, with formation depth of 90 - 1 100 m, layer thickness of 1 - 4m, series combined thickness of 310 m and viscosity of gas ?free crude oil of 90-160 000 mPa·s. Through 20 years study on production techniques of heavy oil, high- periodic steam soak technique in thin - bedded layers has been established, which successfully makes heavy oil productive when the thickness of layers is over 3m, and viscosity limit is increased to 80 000 mPa·s. With this technique, development efficiency is greatly enhanced, for example, the recovery ratio of steam soak is up to 30. 7%, gas - oil ratio is 0. 4, and the production cost is decreased 23% -30%.