Viscous oil recovery method

Claim 1

A method of recovering viscous oil from a subterranean, low transmissibility, viscous oil-containing formation comprising: (a) penetrating the formation with at least one injection well and establishing a cavity in the bottom portion of said formation adjacent said injection well and extending horizontally from one-third to one-half the distance between the injection well and the production well and vertically up to one-fifth the thickness of the formation and having a void space not greater than 0.10 pore volume, said injection well being in fluid communication with said cavity; (b) penetrating the formation with at least one production well spaced apart from said injection well, said production well being in fluid communication with the upper two-thirds or less of the vertical thickness of the formation; (c) injecting 0.35 to 0.45 pore volume of steam at an injection rate within the range of 4.5 to 6.5 barrels/day/ac.-ft. into the cavity in the lower portion of the formation via said injection well and recovering fluids including oil from the formation via said production well; (d) subsequently shutting in said injection well and continuing to recover fluids including oil from the formation via said production well for a predetermined period of time and recovering fluids including oil from the formation via the production well without steam breakthrough; (e) injecting a predetermined amount of hot water or low quality steam into the formation via said injection well; and (f) continuing to recover fluids including oil from the formation via said production well until the recovered fluids contain an unfavorable amount of steam or water.

Claim 2

A method of recovering viscous oil from a subterranean, low transmissibility, viscous oil-containing formation comprising: (a) penetrating the formation with at least one injection well and establishing a cavity in the bottom portion of said formation adjacent said injection well and extending horizontally from one-third to one-half the distance between the injection well and the production well and vertically up to one-fifth the thickness of the formation and having a void space not greater than 0.10 pore volume, said injection well being in fluid communication with said cavity; (b) penetrating the formation with at least one production well spaced apart from said injection well, said production well being in fluid communication with the upper two-thirds or less of the vertical thickness of the formation; (c) injecting 0.35 to 0.45 pore volume of steam at an injection rate within the range of 4.5 to 6.5 barrels/day/ac.-ft. into the cavity in the lower portion of the formation via said injection well and recovering fluids including oil from the formation via said production well; (d) subsequently shutting in said injection well and continuing to recover fluids including oil from the formation via said production well for a predetermined period of time and recovering fluids including oil from the formation via the production well without steam breakthrough; (e) injecting a predetermined amount of hot water or low quality steam into the formation via said injection well; and (f) continuing to recover fluids including oil from the formation via said production well until the recovered fluids contain an unfavorable amount of steam or water.

Claim 7

A method of recovering viscous oil from a subterranean, low transmissibility, viscous oil-containing formation comprising: (a) penetrating the formation with at least one injection well and establishing a cavity in the bottom portion of said formation adjacent said injection well and extending horizontally from one-third to one-half the distance between the injection well and the production well and vertically up to one-fifth the thickness of the formation and having a void space not greater than 0.10 pore volume, said injection well being in fluid communication with said cavity; (b) penetrating the formation with at least one production well spaced apart from said injection well, said production well being in fluid communication with the upper two-thirds or less of the vertical thickness of the formation; (c) injecting 0.35 to 0.45 pore volume of steam at an injection rate within the range of 4.5 to 6.5 barrels/day/ac.-ft. into the cavity in the lower portion of the formation via said injection well; (d) simultaneously injecting a predetermined amount of steam or solvent into the upper two-thirds or less of the formation via said production well; (e) recovering fluids including oil from the formation via said production well; (f) repeating steps (d) and (e) for a plurality of cycles; (g) shutting in said injection well and continuing to recover fluids including oil from the formation via said production well for a predetermined period of time and recovering fluids including oil from the formation via the production well without steam breakthrough; (h) injecting a predetermined amount of hot water or low quality steam into the formation via said injection well; and (i) continuing to recover fluids including oil from the formation via said production well until the recovered fluids contain at unfavorable amount of steam or water.

Claim 8

A method of recovering viscous oil from a subterranean, low transmissibility, viscous oil-containing formation comprising: (a) penetrating the formation with at least one injection well and establishing a cavity in the bottom portion of said formation adjacent said injection well and extending horizontally from one-third to one-half the distance between the injection well and the production well and vertically up to one-fifth the thickness of the formation and having a void space not greater than 0.10 pore volume, said injection well being in fluid communication with said cavity; (b) penetrating the formation with at least one production well spaced apart from said injection well, said production well being in fluid communication with the upper two-thirds or less of the vertical thickness of the formation; (c) injecting 0.35 to 0.45 pore volume of steam at an injection rate within the range of 4.5 to 6.5 barrels/day/ac.-ft. into the cavity in the lower portion of the formation via said injection well; (d) simultaneously injecting a predetermined amount of steam or solvent into the upper two-thirds or less of the formation via said production well; (e) recovering fluids including oil from the formation via said production well; (f) repeating steps (d) and (e) for a plurality of cycles; (g) shutting in said injection well and continuing to recover fluids including oil from the formation via said production well for a predetermined period of time and recovering fluids including oil from the formation via the production well without steam breakthrough; (h) injecting a predetermined amount of hot water or low quality steam into the formation via said injection well; and (i) continuing to recover fluids including oil from the formation via said production well until the recovered fluids contain at unfavorable amount of steam or water.