The Research On Steam Distribution Technique With Equal Dryness In Heavy Oil Wells

There are abundant heavy oil resources in the world. A lot of large and medium size heavy oil reservoirs have been found in areas and basins such as Songliao Basin, Bohai Basin and Junggar Basin in China. It is predicted that the geologic reserve of heavy oil reservoirs in China exceeds 8×108m3. However, the viscosity of heavy oil is high, and the filtrational resistance of oil layer is large, also the mobility of heavy oil is poor, so it is difficult to recover heavy oil. Since the viscosity of heavy oil decreases with temperature increases, it is commonly accepted that steam injecting thermal oil recovery is an ideal heavy oil recovery method.Currently, the decreasement of heavy oil recovery is due to different physical properties of oil layers, and different amout of steam is absorbed by oil layers, so heavy oil recovery is low. The fundamental way to solve the above problems is to improve gas absorption profile of the well. And the technique of steam allocation with equal dryness fraction is based on improving steam absorption profile of oil well to increase well yield.In this paper, based on the analysis of the influence of geological condition and steam injection condition on thermal energy allocation of wet steam at well bottom, flow characteristics of steam in the pipe and perforations are stimulated to support the structural design of steaming pipe string, then uniform and appropriate steam allocation at well bottom is achieved. For vertical wells, the angles of steaming pipe string perforations are changed to influence steaming effect, and steam overlap is reduced; for straight delamination wells ,we realize different reservoir thermal fluid allocation by embedding tube structure; for horizontal wells, since oil recovery is poor at the middle and end part of long wells, less or no perforation at heel and downward perforation, and aclinal perforation in the middle part are adopted to increase oil recovery.Therefore, the flow characteristics of two-phase fluid and the phase separation mechanism and influencing factors are studied to support technically the bottleneck problems of steam allocation with equal dryness fraction, and ultimately, technical support is gained to slove the problems due to steam with unequal dryness fraction which is absorbed by straight and horizontal wells in heavy oil recovery.