A great quantity of crude is heavy crude oil which has been produced by using steam huff-puff method in Liaohe Oil Field. This kind of crude contains a lot of resin-asphaltene and possesses the property of very high viscosity (4537 mPa. s at 50°C) and specific gravity (0.9568 — 0.9611). The formation is not only very sensible to water, but also damaged by fluids of drilling mud. Through injecting steam, the production rate was still very low and duration of steam huff-puff was very short because of plugs which were formed by clay swelling and the residual hydrocarbon that produced by volatilization of light fraction of heavy crude around wellbore.

This paper offered a synthetical relieving plug agent which is a mixed fluid, containing organic mixed solvent, inorganic acid, surfactant and other additives. The synthetical relieving plug agent (ARP — 8801 and BJ — 30) has been successfully used in 37 wells in Shuguang No. 48 union, Liaohe Oil Field since April 1989.

According to the statistical data, obtained from 33 experiment wells, it has been sown that the ARP — 8801 and BJ — 30 synthetical relieving plug agent has excellent relieving plug ability for the heavy crude wells of using steam huff-puff method in watersensible formation. The production rate per well was increased on an average from 0—8.6tons/day (before treatment) to 6.0 — 26.7tons/day (after treatment). The duration of steam huff-puff was increased on an average from 121 days (before treatment) to 218 days (after treatment). The oil/steam ratio increased from 0.41 (before treatment) to 1.17 (after treatment). The cumulative incremental oil production has reached 41704 tons.

The application in oil field proved that the method, offered by this paper, is a very nice stimulation treatment for heavy crude wells of injecting steam in the watersensible formation.

The mechanism of relieving plug is discussed in this paper also.

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