Enhanced hydrocarbon recovery by steam injection of oil sand formations

Abstract

The present invention involves a method and apparatus for enhanced recovery of petroleum fluids from the subsurface by injection of a steam and hydrocarbon vaporized solvent in contact with the oil sand formation and the heavy oil and bitumen in situ. Multiple propped hydraulic fractures are constructed from the well bore into the oil sand formation and filled with a highly permeable proppant. Steam, a hydrocarbon solvent, and a non-condensing diluent gas are injected into the well bore and the propped fractures. The injected gas flows upwards and outwards in the propped fractures contacting the oil sands and in situ bitumen on the vertical faces of the propped fractures. The steam condenses on the cool bitumen and thus heats the bitumen by conduction, while 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 mobilize the bitumen in a predominantly circumferential, i.e. orthogonal to the propped fracture, diffusion direction at a nearly uniform rate into the oil sand deposit. The produced product of oil and dissolved solvent is pumped to the surface where the solvent can be recycled for further injection.

1 . A method for in situ recovery of hydrocarbons from a hydrocarbon containing formation, 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 proppant and diluent filled hydraulic fractures from the bore hole to create a process zone within the formation by injecting a fracture fluid into the casing;    c. injecting steam into a section of the bore hole connected to the hydraulic fractures;    d. recovering a mixture of diluent and hydrocarbons from the formation.    
   
   
       2 . A hydrocarbon production well in a formation of unconsolidated and weakly cemented sediments, 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 source for delivering the fracture fluid into the injection casing with sufficient 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; and    d. a steam source for injecting steam into the casing and the hydraulic fractures to produce hydrocarbons from the formation.