Crude oil with high viscosity and high relative density is usually called heavy oil. my country's heavy oil has low asphaltene content, high colloid content, and low metal content. The heavy oil viscosity is high and the relative density is low. Since the properties of heavy oil and conventional crude oil are very different, their oil recovery processes are also very different.

Compared with conventional light crude oil, heavy oil mainly has the following characteristics: (1) High viscosity, high density, and poor fluidity. It not only increases the difficulty and cost of extraction, but also makes the ultimate recovery rate of the oil field very low. The key to heavy oil recovery is to improve its flow capacity in oil reservoirs, wellbores and gathering pipelines. (2) The content of light components in heavy oil is low, while the content of gum and asphaltene is high. (3) The viscosity of heavy oil is sensitive to temperature. As the temperature of heavy oil increases, its viscosity decreases significantly, which is the main mechanism of thermal recovery of heavy oil.

Thermal treatment oil production technology is to provide thermal energy to the oil layer to increase the temperature of the oil layer rock and fluid, thereby increasing the reservoir's oil driving power, reducing the viscosity of the oil layer fluid, preventing wax formation in the oil layer, reducing the oil layer seepage resistance, and achieving better results. The purpose is to effectively exploit heavy oil and high pour point oil. Currently, the commonly used oil recovery technologies for thermal treatment oil layers mainly include injection of thermal fluid (such as steam and hot water) and burning oil layers (Figure 5.6). Among them, the oil recovery method of steam injection treatment oil layer mainly includes two methods: steam huff and puff and steam flooding according to the characteristics of its oil recovery process.