Dual underground tunnel system for hydrocarbon exploitation

Abstract

A system for recovering hydrocarbons from a subterranean formation includes an upper tunnel extending through the formation. In addition, the system includes a lower tunnel extending through the formation below a portion of the upper tunnel. Further, the system includes a plurality of conduits extending from the upper tunnel through the formation to the lower tunnel. Still further, the system includes a plurality of wellbores extending from the lower tunnel into a hydrocarbon-bearing portion of the formation.

What is claimed is: 
     
         1 . A system for recovering hydrocarbons from a reservoir contained in a subterranean formation, comprising:
 an upper tunnel extending through the formation;   a lower tunnel extending through the formation below a portion of the upper tunnel;   a plurality of conduits extending from the upper tunnel through the formation to the lower tunnel; and   a plurality of wellbores extending from the lower tunnel to the reservoir in the formation.   
     
     
         2 . The system of  claim 1 , further comprising:
 an access tunnel extending through the formation; and   a connection tunnel connecting the access tunnel to the upper or lower tunnel.   
     
     
         3 . The system of  claim 1 , wherein each wellbore is coaxially aligned with one conduit. 
     
     
         4 . The system of  claim 3 , wherein the conduits are vertically oriented, parallel, and arranged in a row. 
     
     
         5 . The system of  claim 2 , further comprising:
 a drilling rig disposed in the upper tunnel over a first of the conduits; and   a BOP disposed in the lower tunnel over one of the wellbores that is coaxially aligned with the first of the conduits.   
     
     
         6 . The system of  claim 5 , further comprising:
 a first rail system disposed along a floor of the upper tunnel or the lower tunnel; and   a second rail system coupled to a ceiling of the upper tunnel.   
     
     
         7 . The system of  claim 6 , wherein the drilling rig is disposed on a rail car of the first rail system. 
     
     
         8 . The system of  claim 1 , wherein the lower tunnel extends parallel to the portion of the upper tunnel. 
     
     
         9 . The system of  claim 8 , wherein the upper tunnel has a longitudinal axis and the lower tunnel has a longitudinal axis, and wherein the longitudinal axis of the upper tunnel lies in a first vertical plane and the longitudinal axis of the lower tunnel lies in a second vertical plane;
 wherein the second vertical plane intersects the portion of the upper tunnel;   wherein the second vertical plane is laterally spaced from the first vertical tunnel along the portion of the upper tunnel.   
     
     
         10 . The system of  claim 1 , wherein the upper tunnel has a diameter D 1  and the lower tunnel has a diameter D 2 ;
 wherein the ratio of D 2  to D 1  is between 0.3 and 1.0.   
     
     
         11 . The system of  claim 10 , wherein the upper tunnel laterally overlaps the lower tunnel by a horizontal distance D o ;
 wherein the ratio of distance D o  to the diameter D 1  is between 0.1 and 1.0.   
     
     
         12 . A method for recovering hydrocarbons from a reservoir in a subterranean formation, the method comprising:
 constructing an upper tunnel that extends through the formation;   constructing a lower tunnel that extends through the formation and is disposed below a portion of the upper tunnel; and   drilling downward from the upper tunnel through the lower tunnel and into the formation toward the reservoir.   
     
     
         13 . The method of  claim 12 , further comprising:
 producing hydrocarbons in the reservoir through the formation to the lower tunnel.   
     
     
         14 . The method of  claim 12 , further comprising:
 constructing an access tunnel that extends through the formation; and   constructing at least one connection tunnel connecting the access tunnel to the upper or lower tunnel.   
     
     
         15 . The method of  claim 14 , further comprising:
 positioning a drilling rig in the upper tunnel over a first drilling location;   positioning a BOP in the lower tunnel over the first drilling location; and   advancing a drillstring from the drill rig through the BOP to drill at the first drilling location.   
     
     
         16 . The method of  claim 15 , further comprising:
 moving the drilling rig through the upper tunnel to a second drilling location;   moving the BOP in the lower tunnel to the second drilling location; and   advancing a drillstring from the drill rig through the BOP to drill at the second drilling location.   
     
     
         17 . The method of  claim 12 , wherein the lower tunnel is parallel to the upper tunnel. 
     
     
         18 . A method for recovering hydrocarbons from a reservoir in a subterranean formation, the method comprising:
 (a) positioning a drilling rig at a first location in an upper tunnel traversing the formation;   (b) positioning a BOP at a first location in the lower tunnel that is below the first location in the upper tunnel;   (c) advancing a drillstring from the drilling rig through the BOP; and   (d) drilling a first wellbore downward from the lower tunnel with the drilling rig and drillstring.   
     
     
         19 . The method of  claim 18 , further comprising:
 (e) moving the drilling rig to a second location in the upper tunnel;   (f) moving the BOP to a second location in the lower tunnel that is below the second location in the upper tunnel; and   (g) advancing a drillstring from the drilling rig through the BOP; and   (h) drilling a second wellbore downward from the lower tunnel with the drilling rig and drillstring.   
     
     
         20 . The method of  claim 18 , wherein (a) comprises transporting the drilling rig to the first location in the upper tunnel with one or more rail cars, and wherein (b) comprises transporting the BOP to the first location in the lower tunnel with a rail car. 
     
     
         21 . The method of  claim 18 , wherein (a) comprises moving the drilling rig through an access tunnel connected to the upper tunnel; and
 wherein (b) comprises moving the BOP through the access tunnel connected to the lower tunnel.   
     
     
         22 . The method of  claim 18 , further comprising:
 (e) producing hydrocarbons in the reservoir through the formation and the first wellbore.