High vertical conformance steam drive oil recovery method

Claim 1

A method of recovering viscous oil from a subterranean, permeable, viscous oil-containing formation, said formation being penetrated by at least three wells, one injection well and one production well, said injection well being in fluid communication with a substantial portion of the formation, said production well containing two flow paths from the surface, the first being in fluid communication with the upper 2/3 or less of the formation, and the second being in fluid communication with the bottom 1/3 or less of the formation, and an infill well located between the injection well and production well in fluid communication with no more than the lower 50 percent of the recovery zone defined by the injection and production wells, comprising: (a) injecting a thermal oil recovery fluid comprising steam into the injection well and recovering fluid including oil from the formation by the first flow path in the production well until the fluid being recovered from the production well comprises a predetermined amount of steam or water; (b) simultaneously injecting a predetermined volume of a solvent or a mixture of solvent and hot water or steam, said solvent being liquid at injection conditions, into the formation via the second flow path of the production well; (c) recovering fluids including solvent and petroleum from the formation via the second flow path; (d) repeating steps (b) and (c) for a plurality of cycles; (e) thereafter continuing injecting a thermal oil recovery fluid into the injection well and recovering fluids including oil from the formation by the infill well until the fluid being recovered comprises a predetermined fraction of steam or water; (f) thereafter injecting hot water into the infill well while continuing injecting a thermal recovery fluid into the injection well and recovering fluids from the formation by means of the second flow path in the production well until the percentage of water in the fluids being recovered reaches a predetermined value; and thereafter (g) injecting a thermal recovery fluid comprising steam into the infill well and injecting a fluid into the injection well and recovering fluids from the formation via both flow paths in the production well initially until the fluids being recovered comprise at least 80 percent water.

Claim 2

A method of recovering viscous oil from a subterranean, permeable, viscous oil-containing formation, said formation being penetrated by at least three wells, one injection well and one production well, said injection well being in fluid communication with a substantial portion of the formation, said production well containing two flow paths from the surface, the first being in fluid communication with the upper 2/3 or less of the formation, and the second being in fluid communication with the bottom 1/3 or less of the formation, and an infill well located between the injection well and production well in fluid communication with no more than the lower 50 percent of the recovery zone defined by the injection and production wells, comprising: (a) injecting a thermal oil recovery fluid comprising steam into the injection well and recovering fluid including oil from the formation by the first flow path in the production well until the fluid being recovered from the production well comprises a predetermined amount of steam or water; (b) simultaneously injecting a predetermined volume of a solvent or a mixture of solvent and hot water or steam, said solvent being liquid at injection conditions, into the formation via the second flow path of the production well; (c) recovering fluids including solvent and petroleum from the formation via the second flow path; (d) repeating steps (b) and (c) for a plurality of cycles; (e) thereafter continuing injecting a thermal oil recovery fluid into the injection well and recovering fluids including oil from the formation by the infill well until the fluid being recovered comprises a predetermined fraction of steam or water; (f) thereafter injecting hot water into the infill well while continuing injecting a thermal recovery fluid into the injection well and recovering fluids from the formation by means of the second flow path in the production well until the percentage of water in the fluids being recovered reaches a predetermined value; and thereafter (g) injecting a thermal recovery fluid comprising steam into the infill well and injecting a fluid into the injection well and recovering fluids from the formation via both flow paths in the production well initially until the fluids being recovered comprise at least 80 percent water.