Patent ID: 7328743

Claim:
A process for recovering oil from a reservoir in an underground formation, comprising: a) providing a vertical injection well completed in the lower part of the reservoir or a horizontal injection well located and completed in the lower part of the reservoir, and a production well having a generally vertical pilot portion and a generally horizontal leg which is completed relatively high in the reservoir and oriented toward the completed part of the injection well; b) injecting a liquid heavier than oil into the reservoir through the injection well to establish a body of said liquid low in the reservoir and underlying the horizontal leg of the production well; c) continuing to inject liquid with the production well open, so that oil is produced through the horizontal leg, and the leg creates a low pressure sink which causes a displacement front to advance either or both laterally and upwardly through the reservoir toward the horizontal leg of the production well, thereby driving oil through the horizontal leg of the production well, the open portion of the horizontal leg at which most of the production takes place being termed the producing toe portion of the horizontal leg; d) after a time, placing a chemical blocking agent at the producing toe portion of the horizontal leg of the production well to create a blockage in the producing toe portion and to create a new producing toe portion in an open portion of the horizontal leg adjacent to the blockage, through which production may take place; e) continuing production through the new producing toe portion and the open portion of the horizontal leg of the production well; and f) optionally repeating steps d) and e) to progressively block producing toe portions in a direction toward the pilot portion of the production well.