Method for improved gravity drainage in a hydrocarbon formation

A method for improved gravity drainage in a hydrocarbon formation, the method comprising:

• drilling a production well through a first substantially horizontal production layer of a reservoir, wherein the production well is substantially horizontal and wherein the production layer comprises oil sand;
• drilling a perforation well above the production well in a layer separated from the production layer by a fluid barrier, wherein the perforation well is substantially horizontal, wherein the perforation well is disposed adjacent the fluid barrier, wherein the layer comprises oil sand, and wherein the fluid barrier is substantially horizontal and comprises shale;
• perforating the formation adjacent the perforation well and perforating said fluid barrier to provide perforations, which form a fluid flow path to the production layer, wherein the perforation well is positioned above the fluid barrier and the perforations are directed downwardly through the perforation well and through the fluid barrier and wherein each perforation extends vertically from the perforation well through the oil sand and through the fluid barrier;
• inducing gravity drainage from the perforation well through the fluid flow path to the production well by injecting steam into the layer surrounding the perforation well to cause hydrocarbons in the oil sand formation to lose viscosity and flow through the fluid path provided by the perforations downwards under the action of gravity into the production well;
• producing fluids collected in the production well;
• wherein the formation is constituted by an oil sand formation comprising a stacked reservoir having multiple layers with intermediate fluid barriers, and
• wherein the step of perforating the formation adjacent the perforation well is performed radially outwards from the perforation well into the formation.