Through the use of high temperature and high pressure two-dimension physical simulation and numerical simulation technology, researches were carried out on the production mechanism of Gas-SAGD (Adding N2 in the process of SAGD-Steam Assisted Gravity Drainage) process, mainly including forming thermal insulating layer, reducing the heat loss in the overlying rocks, and improving thermal efficiency; effectively slowing down steam overlap velocity, and expanding the horizontal steam swept volume; reducing steam injection volume to improve economic benefits. It optimizes the nitrogen injection pattern, nitrogen steam ratio and effective nitrogen injection volume. Research results show that nitrogen assisted SAGD exploration technology has the feasibility to be used in Guantao oil reservoir of Du 84 block; it can promote steam chamber in sideways to increase available reserves and can extend SAGD production time and increase oil steam ratio and reservoir recovery factor.

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