Method for Recovering Hydrocarbons from Subterranean Formations

Abstract

Recovery of viscous hydrocarbon from subterranean formations is assisted by using a plurality of novel U-tube type wells, each with dual wellheads, a moveable wellbore packer, a lateral section with a concentric communication zone and with sequential injection production perforations in which heat is injected into the proximal perforations and hot oil and produced fluids are produced from the distal perforations, the whole process being controlled by modulating the production flow where the wellbore fluids are controlled to act as a hydraulic seal to limit bypass of injected fluids. The injection-production displacement process moves axially along the wellbore in a sequential manner as hydrocarbon volumes are depleted by injected fluid displacement of oil and oil and water production.

1 . A method for recovering hydrocarbons from a subterranean formation containing viscous oil or other heavy hydrocarbons; the method comprising the steps of: 
 (a) drilling at least one wellbore comprising a vertically drilled downward section, a lateral section and an upward section, in the hydrocarbon bearing formation by penetrating the formation with conventional drilling equipment;    (b) providing a wellhead at the entrance or proximal end of the wellbore and another wellhead at the exit or distal end of the wellbore;    (c) providing a plurality of perforations in the wellbore at pre-selected intervals;    (d) installing a downhole wellbore packer between upper and lower perforations;    (e) forming an annular hot zone of increased fluid conductivity near the said wellbore in the said formation to facilitate vertical flow of heated low viscosity oil and hot water produced from condensed steam, towards lower production perforations;    (f) heating the said formation by injecting a displacing fluid into the formation;    (g) lifting the produced oil and displaced fluids to the surface.    
   
   
       2 . The method of  claim 1 , wherein the said formation is heated by injecting steam through upper perforations as a displacing fluid.  
   
   
       3 . The method of  claim 2 , wherein the injected steam heats the wellbore and surrounding formation for sufficient time and at a calculated temperature.  
   
   
       4 . The method of  claim 1 , wherein the said hot annular zone is formed by installing and initiating a downhole heater for a predetermined time greater than 24 hours, and at a predetermined temperature.  
   
   
       5 . The method of  claim 1 , wherein the said formation is heated by transmitting heat energy to the said formation by using a combustion front.  
   
   
       6 . The method of  claim 1 , wherein the said formation is heated by transmitting heat energy to the said formation by using a steam chamber or steam bank.  
   
   
       7 . The method of  claim 1 , wherein the driving pressure of produced oil and displaced fluids is sufficiently high to push the produced oil and displaced fluids to the surface.  
   
   
       8 . The method of  claim 1 , further comprising the steps of: 
 installing a fluid recovery system to lift the produced oil and displaced fluids to the surface, wherein the produced oil and displaced fluids are lifted to the surface by using the said fluid recovery system.    
   
   
       9 . The method of  claim 8 , wherein the said fluid recovery system comprises a production pump.  
   
   
       10 . The method of  claim 1 , wherein the step of drilling the upward section of the wellbore comprises the steps of: 
 drilling a small pilot hole upwards to the exit end of the wellbore with a small drilling assembly and bit; and    enlarging the upward section of the said wellbore.    
   
   
       11 . The method of  claim 10 , wherein the step of enlarging the upward section comprises the steps of: 
 installing a back-reamer bit, connected to the pull back drill rig at the entrance of the wellbore by a drill pipe; and    pulling the said back-reamer bit to travel from the exit end of the wellbore through the small pilot hole to the entrance, to enlarge the upward section of the said wellbore.    
   
   
       12 . The method of  claim 10 , wherein the step of enlarging the upward section comprises the steps of: 
 installing a forward-reamer bit, connected to the drill rig at the exit end of the wellbore by a drill pipe; and    rotating the said forward-reamer bit and pushing it forward to travel from the exit end of the wellbore through the small pilot hole to the entrance, to enlarge the upward section of the said wellbore    
   
   
       13 . The method of  claim 1 , further comprising the step of cementing a steel casing in the wellbore in the said formation.  
   
   
       14 . The method of  claim 1 , wherein the wellhead at the proximal end of the wellbore is an injection wellhead.  
   
   
       15 . The method of  claim 1 , wherein the wellhead at the distal end of the wellbore is a production wellhead.  
   
   
       16 . The method of  claim 1 , wherein the perforation zones in the wellbore are positioned as paired groups or couplets.  
   
   
       17 . The method of  claim 16 , wherein the proximal perforations in the pair group form an injector set of perforations.  
   
   
       18 . The method of  claim 16 , wherein the next or distal set of perforations in the pair group forms a producer set of perforations.  
   
   
       19 . The method of  claim 1 , wherein the downhole packer in the wellbore is placed between the injector and producer pair of perforations separating the injection and production zones.  
   
   
       20 . The method of  claim 1 , wherein the downhole packer forces the injection fluid to be to exit the wellbore and be injected into the hydrocarbon bearing formation.  
   
   
       21 . The method of  claim 1 , wherein the downhole packer is retractable and be either solid or inflatable.  
   
   
       22 . The method of  claim 1 , wherein the injected fluid is steam.  
   
   
       23 . The method of  claim 1 , wherein the injected fluid forms a steam bank or chamber in the hydrocarbon reservoir.  
   
   
       24 . The method of  claim 1 , wherein the said hot annular zone is formed by installing a reaming device and reaming out a portion of the said formation, thereby enlarging the said wellbore substantially.  
   
   
       25 . The method of  claim 24 , wherein the reamed zone is concentric to the wellbore.  
   
   
       26 . The method of  claim 24 , wherein the reamed zone forms an axial communication zone for fluid flow from the steam bank to the production zone perforations.  
   
   
       27 . The method of  claim 1 , wherein the downhole packer is moved axially along the wellbore to new hydrocarbon rich formations to carry out the said method, after each steam displacing zone is depleted of hydrocarbons.  
   
   
       28 . The method of  claim 1 , further comprising the step of: 
 installing a downhole backpressure valve in the said wellbore to create a backpressure to prevent the injected steam from bypassing downwards into the production perforations.    
   
   
       29 . The method of  claim 1 , wherein the accumulation of produced hot oil in the lateral section is controlled by controlling the fluid production rate at the distal end of the wellbore, to provide a hydraulic “P-trap” effect, which acts as a backpressure valve preventing the bypass of steam from the upper perforations to the lower perforations.  
   
   
       30 . The method of  claim 29 , wherein the said wellbore is pressured from the surface with natural gas or some inert gas to implement the “P-trap” effect pneumatically in addition to hydraulically.  
   
   
       31 . The method of  claim 1 , wherein the injected fluid is air.  
   
   
       32 . The method of  claim 1 , wherein the injected fluid is a combination of steam and heated water.  
   
   
       33 . The method of  claim 31 , wherein the injected air provides the oxygen needed for combustion front of the in-situ hydrocarbon.  
   
   
       34 . The method of  claim 1 , wherein the angle of the lateral section of the wellbore in the formation ranges between zero (0) degrees to 90 degrees from the horizontal.  
   
   
       35 . The method of  claim 4 , wherein the downhole heater remains in place substantially long enough to heat radially, a preferred annular distance of at least two feet around the wellbore.  
   
   
       36 . The method of  claim 4 , wherein the downhole heater is retractable and moveable.  
   
   
       37 . The method of  claim 1 , wherein the heating of the annular communication zone increases the porosity of the reservoir formation in the annular region.  
   
   
       38 . The method of  claim 1 , wherein the selective heating of the annular communication region increases the permeability of the reservoir formation in the communication zone.  
   
   
       39 . The method of  claim 1 , wherein the selective heating of the annular communication region decreases the water saturation of the reservoir formation in the communication zone.  
   
   
       40 . The method of  claim 37 , wherein the increased reservoir rock formation porosity increases the fluid transmissibility of the rock to oil flow in the annular communication zone.  
   
   
       41 . The method of  claim 38 , wherein the increased reservoir rock formation permeability increases the fluid transmissibility of the rock to oil flow in the annular communication zone.  
   
   
       42 . The method of  claim 39 , wherein the decreased reservoir rock formation water saturation increases the fluid transmissibility of the rock to oil flow in the annular communication zone.  
   
   
       43 . The method of  claim 1 , wherein the lateral wellbore section extends substantially below the hydrocarbon formation.  
   
   
       44 . The method of  claim 29 , wherein the P-trap is used for controlling the flow of produced oil in the wellbore.  
   
   
       45 . The method of  claim 1 , wherein the displacing fluid is injected intermittently.  
   
   
       46 . The method of  claim 1 , wherein the displacing fluid is injected continuously.  
   
   
       47 . The method of  claim 1 , wherein the produced fluids are recovered intermittently.  
   
   
       48 . The method of  claim 1 , wherein the produced fluids are recovered continuously.  
   
   
       49 . The method of  claim 19 , wherein the downhole retractable packer completely separates the injection perforations from the production perforation in the wellbore.  
   
   
       50 . The method of  claim 1 , wherein the heated annular zone extends substantially from below the base of the injection perforations to the top of the production perforations  
   
   
       51 . The method of  claim 1 , wherein maintaining a prescribed oil level in the wellbore controls the vertical steam flow.  
   
   
       52 . The method of  claim 51 , wherein maintaining a prescribed oil level in the wellbore prevents the flow of steam bypassing the cold formation and flowing to the production perforations.  
   
   
       53 . The method of  claim 1 , comprising a plurality of parallel wellbores simultaneously over a large areal extent to maximize oil recovery by minimizing the heat losses attributed to each wellbore.  
   
   
       54 . The method of  claim 4 , wherein the said temperature ranges between 300 deg. F and 600 deg. F.  
   
   
       55 . The method of  claim 3 , wherein steam is injected until the formation is depleted of movable oil.  
   
   
       56 . The method of  claim 3 , wherein the injected steam heats the formation to a temperature above 212 deg. F.