Study On Viscosity Reduction Of LiaoHe Super Heavy Crude Oil

Thermal recovery including cyclic-steam-stimulation and steam-driving is the most popular technology to recover super heavy oil in the world. However, there exist some problems such as high cost of steam injection, low displacement efficiency and low oil recovery in late steam injection. On the other hand, the viscosity treating with chemicals have made very important contribution to the enhancement of heavy oil recovery. The combination of thermal recovery and the viscosity treating with chemicals could be helpful to EOR to reduce the viscosity of heavy oil.In this paper, Liaohe super heavy oil was chosen as feed and viscosity reduction experimenets in an antoclave at thermal recovery temperature (200~300℃) with some transition metal salts, free radical initiators and the self-made viscosity-reducer mixture were conducted.The effects of reaction temperature, reaction time, and water content on the viscosity were studied in detail on the viscosity, composition and average molecular weight of heavy oil. The optimized viscosity reducer was chosen and the mechanism of viscosity reducer was also investigated.It is shown that in anhydrous systems, some transition metal salts and some free radical initiators reduced the viscosity of heavy oil, and the viscosity reduction of the heavy oil by 0.5w% transition metal salt(FeSO4) or 0.3 w% free radical initiator A could reach 30%, respectively,while the viscosity reduction could reach 53% by their mixture. Although the transition metal salts, the free radical initiators, surfactants, anti-associating reagents and hydrogen donor could reduce the viscosity of heavy oil in the aqueous reaction systems of heavy oil, it is difficult to achieve satisfactory results with a single viscosity reducing method.The self-made viscosity-reducer mixture has been developed by screening. The component of the heat-resistant viscosity reducer of super heavy oil is as follows: the initiator A 3000μg·g-1, emulsifying agent A 3000μg·g-1, emulsifying agent B 2000μg·g-1, emulsifying promoter A 4000μg·g-1, effective additive A 5000μg·g-1 and Tetralin: 30000μg·g-1.When the content of water was≧30%, O/W emulsion could formed by the self-made viscosity reducer. The viscosity reduction of the heavy oil reached 96% and the emulsifier plays an important role in this process. However, W/O emulsion could form by the self-made viscosity reducer when the content of water was <30%. Since the aquathermolysis catalyst, anti-associating reagent and diluent played an important role in this process, the viscosity reduction of the heavy oil could reach 80%.Higher reaction temperature, water content and longer reaction time were helpful to viscosity reduction of heavy oil.