Numerical simulation method is applied to study the effects of some parameters on steam overriding, including oil layer thickness, crude viscosity, vertical/horizontal permeability ratio, perforation method, etc. Therefore, the change pattern of steam overriding is obtained and the technical conditions for steam overriding are pointed out. Field test results indicate that by taking some measures, such as adopting the "uphole?? perforation, profile control, separate or selective steam injection, vertical and horizontal well combined SAGD, etc., the uneven producing of the reservoir vertically due to steam overriding can be further decreased. Moreover, these measures play an important role in increasing oil recovery ration during the later production period of CSS. The successful application of these techniques will provide theoretical support and technical guarantee for the production of similar super heavy oil reservoirs in the world during the later production period of CSS.
Keywords: Steam overlay; CSS; Separate or selective steam injection; Vertical and horizontal well combined SAGD