Abstract

Since the production of China offshore heavy oil field, cold production is mainly used for oil recovery. However, it has faced great challenge including declination of oil production, rapid-increasing water cut and sharp cutoff of reservoir pressure. Conventional heavy oil recovery, such as steam stimulation, steam drive, in-situ combustion and SAGD, is not entirely suitable for offshore platform condition (platform space is small). Based on a new portable and convenient gas generator that can produce high-temperature steam, CO2 and N2, a new stimulation treatment is discussed in this paper, which aimed at the characteristic of sharp cutoff of reservoir pressure, combining steam and flue gas stimulation in production well together with injecting weak gel formed by polymer and cross linker in injection well, thus to keep the reservoir pressure to the utmost extent, and obtain maximal recovery.

Numerical simulation study was conducted on the basis of the conceptual model aimed at the recovering mechanism of weak gel injection and steam and flue gas thermal recovery, the mechanism including dwelling and displacement of weak gel, heating and visbreaking of thermal water or steam, solution and miscible visbreaking of CO2, and thermal fluid heating radius enlarging and gas driving effort improvement of N2. On the foundation of mature mechanism, the optimal injection-production technological parameters fit for reservoir development can be estimated by numerical stimulation of several development programs designed for certain reservoir and orthogonal optimizing method. And injection time and rate for weak gel injection preserving pressure are also discussed in this paper.

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