The Liaohe oil field, which is buried at a depth of about 1000 m, has abundant amount of heavy oil. With thermal development by steam injection, it is the most productive heavy oil field in China.
In this paper, the observation of lithological and mineralogical change in the process of steam injection is discussed. Significant dissolution caused by water/rock interaction was observed for the minerals such as quartz and feldspar in the clastic reservoir rock. This caused changes within the pore structure in the rock. A computer program to predict the dissolution loss and precipitation of various minerals in water-rock reaction has been developed. The mechanism of steam displacement is also investigated.