Enhanced hydrocarbon recovery by vaporizing solvents in oil sand formations

Abstract

The present invention involves a method and apparatus for enhanced recovery of petroleum fluids from the subsurface by injecting a hydrocarbon solvent vapor in contact with the oil sand formation and the heavy oil and bitumen in situ. Multiple propped vertical hydraulic fractures are constructed from the well bore into the oil sand formation. The hydrocarbon solvent vapor and a non-condensing diluent gas are injected into the well bore, fill the hydraulic fractures, and thus contact and diffuse into the in situ bitumen. The hydrocarbon solvent vapors diffuse into the bitumen from the vertical faces of the propped fractures. The bitumen softens and flows by gravity to the well bore, exposing fresh surface of bitumen for the process to progressively soften and mobilizes the bitumen in a predominantly circumferentially, i.e. orthogonal to the propped fracture, diffusion direction at a nearly uniform rate into the oil sand deposit. The mobile oil may be deasphalted by the condensed solvent, leaving the heavy asphaltenes behind in the oil sand pore space with little loss of inherent fluid mobility in the processed oil sands. The processed product is produced with the dissolved solvent along with a tail diluent gas. The tail diluent gas is enriched with hydrocarbon solvent and re-injected into the process zone and the cycle repeated.

1 . A method for in situ recovery of hydrocarbons from a hydrocarbon containing formation having an ambient reservoir pressure and temperature, comprising: 
 a. drilling a bore hole in the formation to a predetermined depth to define a well bore with a casing;    b. installing one or more vertical hydraulic fractures from the bore hole to create a process zone within the formation by injecting a fracture fluid at a reservoir fracturing pressure into the casing, wherein the hydraulic fractures contain a proppant;    c. injecting a vaporized hydrocarbon solvent, having a hydrocarbon solvent vapor phase, at a solvent pressure into a section of the well casing connected to the hydraulic fractures;    d. recovering a mixture of solvent and hydrocarbons from the formation.    
   
   
       2 . The method of  claim 1 , wherein the hydrocarbon solvent is one of a group of ethane, propane, butane, or a mixture thereof.  
   
   
       3 . The method of  claim 1 , wherein the hydrocarbon solvent vapor is dry.  
   
   
       4 . The method of  claim 1 , wherein the hydrocarbon solvent is injected at ambient reservoir temperature.  
   
   
       5 . The method of  claim 1 , wherein the hydrocarbon solvent pressure is close to the ambient reservoir pressure but substantially below the reservoir fracturing pressure.  
   
   
       6 . The method of  claim 1 , wherein the hydrocarbon solvent is mixed with a diluent gas.  
   
   
       7 . The method of  claim 6 , wherein the diluent gas is non-condensable under the process conditions in the process zone.  
   
   
       8 . The method of  claim 6 , wherein the non-condensable diluent gas has a lower solubility in the hydrocarbons in the formation than the saturated hydrocarbon solvent.  
   
   
       9 . The method of  claim 6 , wherein the diluent gas is one of a group of methane, nitrogen, carbon dioxide, natural gas, or a mixture thereof.  
   
   
       10 . The method  claim 6 , wherein the diluent gas is dry.  
   
   
       11 . The method of  claim 11 , wherein the hydrocarbon solvent vapor is maintained saturated at or near its dew point.  
   
   
       12 . The method of  claim 1 , wherein the dew point of the hydrocarbon solvent vapor in the injection gas is adjusted to the downhole conditions by injecting additional solvent at depth to add additional solvent to the injected gas.  
   
   
       13 . The method of  claim 1 , wherein the hydrocarbon solvent injection is sufficient to maintain a saturated state of the hydrocarbon solvent vapor in the process zone.  
   
   
       14 . The method of  claim 1 , wherein the hydraulic fractures are filled with proppants of differing permeability.  
   
   
       15 . The method of  claim 1 , wherein the hydrocarbon solvent injection is a pressure pulsed cyclic intermittent injection.  
   
   
       16 . The method of  claim 1 , wherein the hydrocarbon solvent injection is a continuous injection.  
   
   
       17 . The method of  claim 1 , wherein the hydrocarbons produced from the formation are replaced volume for volume with the hydrocarbon solvent.  
   
   
       18 . The method of  claim 1 , wherein the hydrocarbon solvent vapor saturation within a mixture of the hydrocarbon solvent and a diluent gas is monitored and adjusted, based on the dew point of the mixture of the hydrocarbon solvent and the diluent gas.  
   
   
       19 . The method of  claim 1 , wherein the temperature of the hydrocarbon solvent is raised above the ambient reservoir temperature.  
   
   
       20 . The method of  claim 1 , further comprising controlling the temperature and pressure in the majority of the part of the process zone, wherein the temperature is controlled as a function of pressure, or the pressure is controlled as a function of temperature.  
   
   
       21 . The method of  claim 1 , wherein the pressure in the majority of the part of the process zone is at ambient reservoir pressure.  
   
   
       22 . The method of  claim 1 , wherein at least two vertical fractures are installed from the bore hole at approximately orthogonal directions.  
   
   
       23 . The method of  claim 1 , wherein at least three vertical fractures are installed from the bore hole.  
   
   
       24 . The method of  claim 1 , wherein at least four vertical fractures are installed from the bore hole.  
   
   
       25 . A hydrocarbon production well in a formation of unconsolidated and weakly cemented sediments having an ambient reservoir pressure and temperature, comprising: 
 a. a bore hole in the formation to a predetermined depth;    b. an injection casing grouted in the bore hole at the predetermined depth, the injection casing including multiple initiation sections separated by a weakening line and multiple passages within the initiation sections and communicating across the weakening line for the introduction of a fracture fluid to dilate the casing and separate the initiation sections along the weakening line;    c. a fracture fluid source for delivering the fracture fluid into the injection casing with sufficient reservoir fracturing pressure to dilate the injection casing and the formation and initiate a vertical hydraulic fracture, having a fracture tip, at an azimuth orthogonal to the direction of dilation to create a process zone within the formation, for controlling the propagation rate of each individual opposing wing of the hydraulic fracture, and for controlling the flow rate of the fracture fluid and its viscosity so that the Reynolds Number Re is less than 1 at fracture initiation and less than 2.5 during fracture propagation and the fracture fluid viscosity is greater than 100 centipoise at the fracture tip;    d. a source injecting a hydrocarbon solvent, having a hydrocarbon solvent vapor phase, into the casing, the hydraulic fractures and the formation; and    e. recovering a mixture of the hydrocarbon solvent and hydrocarbons from the formation through the casing.    
   
   
       26 . The well of  claim 26 , wherein the hydrocarbon solvent is one of a group of ethane, propane, butane, or a mixture thereof.  
   
   
       27 . The well of  claim 26 , wherein the hydrocarbon solvent vapor is dry.  
   
   
       28 . The well of  claim 26 , wherein the hydrocarbon solvent is injected at ambient reservoir temperature.  
   
   
       29 . The well of  claim 26 , wherein the hydrocarbon solvent is injected close to the ambient reservoir pressure but substantially below the reservoir fracturing pressure.  
   
   
       30 . The well of  claim 26 , wherein the hydrocarbon solvent is mixed with a diluent gas.  
   
   
       31 . The well of  claim 31 , wherein the diluent gas is non-condensable under the process conditions.  
   
   
       32 . The well of  claim 31 , wherein the non-condensable diluent gas has a lower solubility in the hydrocarbons in the formation than the saturated hydrocarbon solvent.  
   
   
       33 . The well of  claim 31 , wherein the diluent gas is one of a group of methane, nitrogen, carbon dioxide, natural gas, or a mixture thereof.  
   
   
       34 . The well  claim 31 , wherein the diluent gas is dry.  
   
   
       35 . The well of  claim 36 , wherein the hydrocarbon solvent vapor is maintained saturated at or near its dew point.  
   
   
       36 . The well of  claim 26 , wherein the dew point of the hydrocarbon solvent vapor is adjusted to the downhole conditions by employing a solvent injector at depth to add additional hydrocarbon solvent to the process zone.  
   
   
       37 . The well of  claim 26 , wherein the hydrocarbon solvent injection is sufficient to maintain a saturated state of the hydrocarbon solvent vapor in the process zone.  
   
   
       38 . The well of  claim 26 , wherein the hydraulic fractures are filled with proppants of differing permeability.  
   
   
       39 . The well of  claim 26 , wherein the hydrocarbon solvent injection is a pressure pulsed cyclic intermittent injection.  
   
   
       40 . The well of  claim 26 , wherein the hydrocarbon solvent injection is a continuous injection.  
   
   
       41 . The well of  claim 26 , wherein the hydrocarbons produced from the formation are replaced volume for volume with the hydrocarbon solvent and a diluent gas.  
   
   
       42 . The well of  claim 26 , wherein the hydrocarbon solvent vapor saturation within the injection gas is monitored and adjusted, based on the dew point of the hydrocarbon solvent and a diluent gas.  
   
   
       43 . The well of  claim 26 , wherein the temperature of the hydrocarbon solvent is raised above the ambient reservoir temperature.  
   
   
       44 . The well of  claim 26 , further comprising controlling the temperature and pressure in the majority of the part of the process zone, wherein the temperature is controlled as a function of pressure, or the pressure is controlled as a function of temperature.  
   
   
       45 . The well of  claim 26 , wherein the pressure in the majority of the part of the process zone is at ambient reservoir pressure.  
   
   
       46 . The well of  claim 26 , wherein at least two vertical fractures are installed from the bore hole at approximately orthogonal directions.  
   
   
       47 . The well of  claim 26 , wherein at least three vertical fractures are installed from the bore hole.  
   
   
       48 . The well of  claim 26 , wherein at least four vertical fractures are installed from the bore hole.