IN SITU HEAVY OIL AND BITUMEN RECOVERY PROCESS

摘要

The present invention is directed to an in situ reservoir recovery process that uses a horizontal well located near the top of a reservoir and an inclined production well to extract bitumen or heavy oil from a reservoir. The process may consist of a first stage in which the top well is used for cold production of reservoir fluids to the surface. In cold production, reservoir fluids are pumped to the surface in the absence of stimulation by steam or other thermal and/or solvent injection. In the present invention, a lower production well is drilled into the formation below the top well. The top well is converted to an injection well or, if no cold production then a top well is drilled as an injector well. A portion of the bottom well is inclined so that one end of the incline is closer to the injector well than the other end of the incline. Alternatively, the new bottom well is inclined at an angle so that the interwell distance between the toes of both wells is less than the interwell distance between the heels of both wells. In the process, steam circulation creates a heated zone at the point of the two wells that are closest together in the reservoir. For example, for an inclined bottom well, this is at the toes of the wells. After thermal communication between the two wells is established, then the wells are switched to a SAGD-like mode: steam or other injectants are injected into the top well and reservoir fluids are produced from the bottom well. The process preferentially produces the relatively lower viscosity oil from the upper portions of the reservoir in the early stages of the process. Later, as the steam chamber expands downwards into the reservoir along the wells, the produced oil contains higher amounts of the heavier, higher viscosity oil found nearer the bottom of the reservoir. The process is particularly useful in the recovery of heavy oil or bitumen from a reservoir that exhibits vertical and lateral areal oil phase viscosity variations. The method is also very useful in reservoirs with bottom water.