| 摘要 |
<p>CYCLIC SOLVENT FLOODING TO RECOVER VISCOUS OILS Oil is recovered from a viscous oil-containing formation, including a tar sand deposit, by providing at least one injection well and at least one spaced-apart production well which extend downwardly from the earth's surface to the bottom of the formation and which at their lower portions extend generally horizontally through and in communication with the formation. Solvent is injected into the injection well and fluids including oil are recovered from the production well until the fluid recovered contains an unfavorable amount of solvent, preferably at least 90 percent. After injection of the solvent is terminated, both the injection well and the production well are shut-in and the formation is allowed to undergo a soak period for a predetermined time, preferably for a time of between 2 to 20 days per foot of formation thickness. After the soak period, solvent is injected into the production well and fluids including oil are recovered from the injection well until the fluid recovered contains an unfavorable amount of solvent, preferably at least 90 percent. After injection of the solvent into the production well is terminated, both wells are shut-in and the formation is allowed to undergo a second soak period for a predetermined time, preferably for 2 to 20 days per foot of formation thickness. Thereafter, a driving fluid is injected into the formation via the injection well to effect a fluid drive of the oil through the formation and oil is produced from the production well until the oil being produced contains an unfavorable amount of driving fluid, preferably at least 90 percent.</p> |
