Due to various operational realities including the precision of the guiding tools that navigate the wells, actual SAGD well pairs in the field are seldom drilled perfectly parallel. And different patterns of trajectory of SAGD wellpair have a significant impact on the steam chamber development and overall recovery factor [1-4].

In this work, the focus is on the quantification of well trajectory on the SAGD performance. Based on the typical in-situ oil viscosities and reservoir properties of 11 SAGD pairs located in the Fengcheng heavy-oil region in Xinjiang Oilfield, different non-parallel patterns of injection-production-well-trajectory combinations including non-parallel vertically (upward inclination, downward inclination), horizontally and both directions between injector and producer well trajectories have been evaluated by using a detailed, 3D, flexible-wellbore reservoir-simulation model.

TTthe vertical and plane offsets in the horizontal segment both cause the smaller regional distance between injector and producer, resulting in better heat communication during preheating phase, while after converting to SAGD production phase, the better communication segment will cause faster steam chamber growth, leaving steam chamber in other segment developing poorly, therefore the SAGD peak oil rate and ultimate oil recovery factor are also affected. Especially, the case of plane and vertical offsets simultaneously cause the plane and vertical unparalleled, which causes the ultimate oil recovery factor 26.2% less than that of the ideal case without offset.

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