Y-grade ngl steam assisted gravity drainage

Abstract

A method of recovering hydrocarbons from a (non-bitumen) heavy crude oil bearing reservoir with structural relief uses the combination of Y-Grade NGL and steam assisted gravity drainage. The method includes injecting steam and Y-Grade NGL into the reservoir through a vertical injection wellbore, displacing hydrocarbons within the reservoir using a combination of the steam, the unfractionated hydrocarbon mixture, and gravity drainage, and then producing the displaced hydrocarbons from the reservoir through a horizontal production wellbore that is positioned structurally lower than and offset from the vertical injection wellbore.

We claim: 
     
         1 . A method of recovering hydrocarbons from a non-bitumen, hydrocarbon bearing reservoir with structural relief, comprising:
 injecting steam and an unfractionated hydrocarbon mixture through a vertical injection wellbore and into the reservoir to form a steam chamber;   displacing hydrocarbons within the reservoir using a combination of the steam, the unfractionated hydrocarbon mixture, and gravity drainage; and   producing the displaced hydrocarbons from the reservoir through a horizontal production wellbore that is positioned structurally lower than and offset from the vertical injection wellbore.   
     
     
         2 . The method of  claim 1 , wherein the hydrocarbons within the reservoir comprise heavy crude oil. 
     
     
         3 . The method of  claim 1 , wherein the reservoir has a thickness greater than 30 feet. 
     
     
         4 . The method of  claim 1 , further comprising displacing the hydrocarbons by reducing the viscosity of the hydrocarbons to less than about 300 centipoise at reservoir conditions. 
     
     
         5 . The method of  claim 1 , wherein the average permeability of the reservoir is greater than about 50 millidarcies. 
     
     
         6 . The method of  claim 1 , wherein the unfractionated hydrocarbon mixture comprises Y-Grade NGL. 
     
     
         7 . The method of  claim 1 , wherein the unfractionated hydrocarbon mixture is injected periodically into the reservoir with steam. 
     
     
         8 . The method of  claim 1 , wherein the unfractionated hydrocarbon mixture is injected simultaneously into the reservoir with steam. 
     
     
         9 . The method of  claim 1 , further comprising increasing pressure within the reservoir by the injection of the steam and the unfractionated hydrocarbon mixture. 
     
     
         10 . The method of  claim 1 , further comprising increasing the API gravity of the hydrocarbons within the reservoir by the injection of the steam and the unfractionated hydrocarbon mixture. 
     
     
         11 . The method of  claim 1 , further comprising reducing the viscosity of the hydrocarbons within the reservoir by the injection of the steam and the unfractionated hydrocarbon mixture. 
     
     
         12 . The method of  claim 1 , further comprising reducing the steam to oil ratio (SOR) within the reservoir by the injection of the steam and the unfractionated hydrocarbon mixture. 
     
     
         13 . The method of  claim 1 , further comprising injecting carbon dioxide with the unfractionated hydrocarbon mixture through the vertical injection wellbore and into the reservoir. 
     
     
         14 . The method of  claim 1 , further comprising injecting nitrogen with the unfractionated hydrocarbon mixture through the vertical injection wellbore and into the reservoir. 
     
     
         15 . The method of  claim 1 , further comprising monitoring the production of hydrocarbons from the horizontal production wellbore and adjusting the injection rate of at least one of the steam and the unfractionated hydrocarbon mixture into the reservoir to optimize hydrocarbon production. 
     
     
         16 . The method of  claim 1 , wherein the hydrocarbons within the reservoir have an API gravity within a range of about 25 degrees to about 10 degrees.