Enhanced hydrocarbon recovery by convective heating of oil sand formations

Abstract

The present invention involves a method and apparatus for enhanced recovery of petroleum fluids from the subsurface by convective heating of the oil sand formation and the heavy oil and bitumen in situ by a downhole electric heater. Multiple propped vertical hydraulic fractures are constructed from the well bore into the oil sand formation and filled with a diluent. The heater and downhole pump force thermal convective flow of the heated diluent to flow upward and outward into the propped fractures and circulating back down and back towards the well bore heating the oil sands and in situ bitumen on the vertical faces of the propped fractures. The diluent now mixed with produced products from the oil sand re-enters the bottom of the well bore and passes over the heater element and is reheated to continue to flow in the convective cell. Thus the heating and diluting of the in place bitumen occurs predominantly circumferentially, i.e. orthogonal to the propped fracture, by diffusion from the propped vertical fracture faces progressing at a nearly uniform rate into the oil sand deposit. In situ hydrogenation and thermal cracking of the in place bitumen can provide a higher grade produced product. The heated low viscosity oil is produced through the well bore at the completion of the active heating phase of the process.

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. providing heat form a heat source to a section of the bore hole containing the diluent;    d. circulating the diluent in the formation; and    e. 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 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 for delivering a diluent in the casing above the elevation of the highest hydraulic fracture; and    e. a heat source positioned within the casing and in contact with the diluent for heating the diluent.