A MULTI-STEP SOLVENT EXTRACTION PROCESS FOR HEAVY OIL RESERVOIRS

摘要

An in situ extraction process for heavy oil reservoirs using solventcomprises removing liquids and gases from areas contacting with theheavy oils to increase an interfacial area of unextracted heavy oilcontactable by the solvent. Solvent vapour is injected into the areas toraise the reservoir pressure until sufficient liquid solvent is present tocontact the increased interfacial area. The reservoir is shut in for asufficient time for the solvent to diffuse into the unextracted oil across theinterfacial area in a ripening step to create a reduced viscosity blend ofsolvent and oil. One or more reservoir characteristics is measured toconfirm the extent of solvent dilution that has occurred of the unextractedoil in the reservoir. Gravity drainage based production is commenced fromthe reservoir upon the blend having a viscosity low enough to permit theblend to drain through the reservoir to a production well.