Patent Publication Number: US-10760394-B2

Title: System and method of producing oil

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present Application is a continuation application of U.S. patent application Ser. No. 14/594,467 filed on Jan. 12, 2015, which claims the benefit of U.S. Provisional Application Ser. No. 61/927,148 filed on Jan. 14, 2014 entitled “System and Method of Producing Oil”, the contents of which are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to a system and method for the recovery of crude oils within the earth and, in particular, to a system and method for recovering highly viscous oils. 
     The world depends heavily on hydrocarbon fuels, such as petroleum, as an energy source. Petroleum hydrocarbons, or “oil,” may be recovered from reservoirs within the earth using a variety of methods, such as drilling for example. Drilling works well for certain categories of oil where the oil viscosity allows the fluid to flow within the well casing to the surface. Where deep oil reserves are being exploited, pumps and other auxiliary equipment may be used to assist the extraction of oil. 
     One category of oil, sometimes referred to as “heavy oil” or “extra-heavy oil” or “bitumen” (hereinafter called “heavy oil”), is highly viscous oil that does not readily flow through the reservoir or production well casing, even with the assistance of pumps or other equipment. This flow or mobility issue may also be caused by compounds such as wax or paraffin. Heavy oil may be extracted using a variety of non-thermal techniques such as mining and cold heavy oil production with sand (CHOPS). However, most of these heavy oil reserves are positioned at depths greater than that from which it may be recovered using mining techniques, and other non-thermal methods such as CHOPS do not produce a high enough fraction of the original oil in place. In an effort to extract this oil, so-called “thermal methods” such as cyclic steam (“huff and puff”), steam flooding, and steam assisted gravity drainage (“SAGD”) have been developed. In these, steam is generated at the surface and transferred down into the well into contact with the oil reserve. The steam heats and reduces the viscosity of the oil enough to allow flow and displacement of the treated oil toward the production wellhead. 
     It should be appreciated that while such surface steam based generating processes do allow for the extraction of heavy oil from reservoirs that were previously unrecoverable by mining techniques, surface steam generation processes generally do incur high energy costs and there is a limit to the depth at which these techniques may be used. It should be appreciated that these processes involve energy losses at several stages: in the steam generation process; in distributing the steam at the surface; and, as the steam is transferred from the surface. Past a certain depth, the cost or technical feasibility of using surface generated steam is prohibitive. Even before that depth is reached, the energy and other costs of producing the oil can be very high. As a result, a large volume of the world&#39;s oil reserves are classified as “unrecoverable” due to the depth and viscosity of the oil, and even recoverable oil may face high production costs. It should further be appreciated that other geographic locations or geologic formations also may not be conducive to surface steam based methodologies. For example, in permafrost areas, surface heat based generation may not be acceptable as the heat may cause a thawing of the ground supporting the oil recovery equipment. Surface steam based generation systems may also be of limited use in oceanic reserves where the loss of thermal energy between the surface heat generator to the ocean floor may make the use of surface steam techniques economically and technically infeasible. 
     Accordingly, it should be appreciated that while existing heavy oil extraction techniques are suitable for their intended purposes a need for improvement remains, particularly in providing a system and method for extracting heavy oil reservoirs located deep within the earth. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the invention, a system for producing oil from an oil reservoir is provided. The system comprising a support module and a steam generator. The support module including an air module, a water module, and a fuel module, wherein the air module, water module and fuel module configured to provide air, water and fuel to an oil well. The steam module includes a steam generator including an injector having a plurality of tubes having an oxidizing catalyst thereon, a combustor is fluidly coupled to the injector to receive air and an air-fuel mixture and burn the air and an air-fuel mixture, a steam generator portion is fluidly coupled to receive combustion gases from the combustor, the steam generator portion having at least one nozzle configured to direct water from the water module into the combustion gases to generate steam, the steam generator is configured to direct the steam and combustion gases in the direction of the oil reservoir. A connector configured to fluidly couple the air module, water module and fuel module to the steam generator. 
     According to another aspect of the invention, a method of producing oil from an oil reservoir is provided. The method includes supplying air, water and fuel to a steam generator. The supplied air is divided into a first portion and a second portion. The second portion is mixed with the supplied fuel. The first portion of air flows through reactor tubes, the reactor tubes having an oxidation catalyst on an outer surface. The mixed second portion of air and supplied fuel lows over the outer surface of the reactor tubes. The first portion of air and the mixed second portion of air and supplied fuel are mixed in a combustor. The mixed first portion of air and the mixed second portion of air and supplied fuel are burned to produce combustion gases. Water is sprayed onto the combustion gases to form steam. The steam and combustion gases are directed in the direction of an oil reservoir. 
     In accordance with another embodiment of the invention, a system for producing oil from an oil reservoir having a well is provided. The system including a support module having: an air module; a water module; and a fuel module. A steam module is provided having: a system casing; a mixer portion disposed within the system casing. The mixer portion having a housing and conduit centrally disposed within the housing, an outside periphery of the conduit and the inside periphery of the housing cooperating to define a hollow interior portion. The conduit has a plurality of openings disposed about a periphery of one end of the conduit, the plurality of openings arranged to fluidly couple the hollow interior portion with an interior portion of the conduit. A first inlet is arranged on one end of the housing arranged to fluidly couple to the fuel module to the hollow interior portion. A second inlet on the end of the housing arranged to fluidly couple the air module to the hollow interior portion. 
     In accordance with still another embodiment of the invention, a system for producing oil from an oil reservoir having a well is provided. The system including: a system casing; a combustor arranged within the system casing and configured to combust a fuel during operation; a diluent generator having a first end fluidly coupled to receive combustion gases from the combustor, the diluent generator further having a second end fluidly coupled to the oil reservoir; a diluent conduit fluidly arranged between the inner surface of the system casing and an outside surface of the combustor and the diluent generator; and at least one nozzle coupled to the outside surface of the diluent generator and configured during operation to spray a diluent fluid into the combustion gases in the diluent generator, a direction of spray being at least partially towards the first end. 
     In accordance with still another embodiment of the invention, a system for producing oil from an oil reservoir having a well is provided. The system having: a system casing; a fuel conduit ( 115 ) and an oxidant conduit ( 114 ) movably arranged within the system casing; a mixer arranged within the system casing and configured to receive an oxidant and a fuel from the fuel conduit and the oxidant conduit, a combustor portion disposed within the system casing and operably coupled to an end of the mixer and configured to form combustion gases; a diluent generator portion disposed within the system casing and operably coupled to the combustor portion opposite the mixer, the diluent generator portion having a terminal end coupled to the system casing; and at least one centering member slidably engaging an inside surface of the system casing and is operably coupled to a periphery at least one of the mixer, the combustor portion and the diluent generator portion. 
     In accordance with still another embodiment of the invention, a system for producing oil from an oil reservoir having a well is provided. The system including: a system casing; an injector disposed within the system casing and fluidly coupled to a fuel conduit, the injector having a plurality of tubes having an oxidizing catalyst thereon, the injector having at least one igniter integrally formed therein, the at least one igniter having a spark mechanism on one end; a combustor disposed within the system casing and fluidly coupled to the injector adjacent the spark mechanism, the combustor configured to receive during operation an air-fuel mixture and burn the air-fuel mixture in response to the spark mechanism being activated; and a diluent generator disposed within the system casing and arranged to receive combustion gases from the combustor and mix a diluent fluid with the combustion gases. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is perspective view, partially in section, of an oil extraction system at three stages of a cyclic steam stimulation or cyclic steam injection process; 
         FIG. 2  is a side schematic view of the oil extraction system of  FIG. 1 ; 
         FIG. 3  is a side schematic view of a steam flood oil extraction system; 
         FIG. 4  is a perspective view, partially in section, of a steam assisted gravity drainage (SAGD) system; 
         FIG. 5  is a schematic illustration of an in situ heavy oil steam extraction system in accordance with an embodiment of the invention; 
         FIG. 6  is a side view, partially in section, of a downhole apparatus for generating steam in accordance with an embodiment of the invention; 
         FIG. 7  is a side sectional view, partially in section, of the downhole apparatus of  FIG. 6  within a well casing; 
         FIG. 8  is a side section view, partially in section, of the downhole apparatus of  FIG. 6 ; 
         FIG. 9  is a partial side sectional view of the interface section of the downhole apparatus of  FIG. 6 ; 
         FIG. 10  is a partial side sectional view of an embodiment of the air fuel mixing portion of the downhole apparatus of  FIG. 6 ; 
         FIGS. 11A and 11B  are a partial side sectional views of the catalytic reactor portion of the downhole apparatus of  FIG. 6 ; 
         FIGS. 11C and 11D  are views of the catalytic reactor portion of the downhole apparatus of  FIG. 6  in accordance with an embodiment of the invention; 
         FIG. 12  is a partial side sectional view of a combustor portion of the downhole apparatus of  FIG. 6 ; 
         FIG. 13  is a partial side sectional view of the steam generation portion of the downhole apparatus of  FIG. 6 ; and 
         FIG. 14  is a partial enlarged side sectional view of the steam generation portion with a water injector. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention provide advantages in extracting heavy oil by in situ generation of a diluent such as steam within an oil reservoir. Further embodiments of the invention provide advantages in reducing the loss of thermal energy between the location of the steam generation and the oil reservoir. Still further embodiments of the invention provide advantages in reducing the costs and emissions associated with the extraction of heavy oil from a reservoir. Yet still further embodiments of the invention provide advantages in allowing the sequestration of carbon dioxide (CO 2 ) generated during oil production within the earth. 
     Embodiments of the present invention also provide advantages in the rate of oil production and in the total amount of oil produced of the original oil in place (OOIP). The combination of combustion products and the injected diluent (steam or other) provide a mechanism for achieving oil mobility, which offers opportunity for improved production. In addition, the downhole injection offers the opportunity to precisely target the release of steam into the reservoir by location of the tool potentially augmented by other techniques such as the use of packers and wellbore perforations to further target the injection zone. 
     An embodiment of the present invention involves the use of CO 2 , Nitrogen or other diluent in place of liquid water. In the case of CO 2 , the CO 2  provides advantages in cooling the combustion gas flow to a more moderate temperature while also having the advantage that a greenhouse gas is injected downhole for potential sequestration for example. The use of CO 2  may also provide a fluid to carry the heat from the combustion process to the oil. As used herein, the term “steam” should be understood to refer to the diluent carrier fluid delivering heat to the oil. 
     An embodiment of the present invention also involves the co-injection of additive materials into the heated product from the tool at some stage. In one embodiment, the co-injection of additive materials occurs at the surface for feeding into the fluid&#39;s umbilical line or subsequently through a separate umbilical line. Such co-injection of additive materials could be helpful for a variety of purposes, including for startup or for anti-corrosive purposes or for downhole injection of a heated solvent for example. 
     Other embodiments of the present invention involve the capability to use water of lower levels of water treatment than that now used for surface boilers or once-through steam generators (OTSRs). These embodiments also offer differing susceptibilities to scaling and corrosion than those involved in boilers and once-through steam generators, providing for use of less costly water treatment processes in conjunction with the system. 
     In accordance with embodiments of the subject invention, a direct-fired downhole diluent system, such as steam system  20  for example, may be used in a variety of oil production configurations, shown in  FIGS. 1-4 , for the extraction of heavy oil from an oil reservoir. As used herein, the term heavy oil means a hydrocarbon based petroleum material having a reservoir viscosity of greater than 1000 centipoise (cP) to greater than 100,000 cP. It should be appreciated that while embodiments herein describe the use of the direct-fired downhole steam system  20  in connection with the extraction of heavy oil from deep reservoirs, this is for exemplary purposes and the direct-fired downhole steam system  20  may be used in any application where generation and injection of a diluent, such as steam for example, into a material or other enclosed space is desired. For example, embodiments of the subject invention may also be used in underwater, permafrost-regions and arctic/Antarctic applications where thermal losses from surface generated steam adversely impact the feasibility or extraction costs of the well. Embodiments of this invention may further be used with the extraction of bitumen, bituminous sands, oil sands and tar sands having a viscosity of less than 1,000 cP or secondary or tertiary production of conventional reservoirs. Embodiments of the invention may also offer advantages for surface steam generation or generation in the well bore at a position above the oil reservoir. 
     Embodiments of the invention may further be used with the downhole apparatus  90  ( FIG. 5 ) located at the surface, retaining the ability to direct fire the combustion process with the steam so that the gases injected into the reservoir contains both steam and combustion gases. While such a device will incur heat losses along the wellbore, it retains other advantages. This may be desirable in some locations rather than placing the downhole apparatus deep within the well. It should be appreciated that while embodiments herein refer to use of the direct-fired downhole steam system  20  with heavy oil, this is for exemplary purposes and embodiments of the invention should not be so limited. Embodiments of the invention may further be used to produce oil of lesser viscosity than heavy oil, where the combustion gas and/or the heat addition prove advantageous in mobilizing such oil in non-primary production processes. Embodiments of the invention may further be used with the downhole apparatus operating at close to atmospheric pressure for direct-fired generation of steam at the surface. 
     With reference to  FIGS. 1-2 , a vertical well configuration is shown where the direct-fired downhole steam system  20  is used to extract heavy oil from a reservoir  22 . In this embodiment, a well  24  is formed at a desired location through several layers  26  of earth into a section that includes reservoir  22 . In general, as used herein, the reservoir  22  is located at depth where the viscosity of the oil (or the presence of wax or paraffin therein) within the reservoir is too high to allow removal via conventional pumping or mining techniques. As will be discussed in more detail below, a downhole apparatus  90  is inserted at a first stage  28  ( FIG. 2 ) within the casing of the well and positioned within the reservoir  22 . Fuel, liquid water, air, and control signals are transferred to the steam generator and steam is produced within the well  24  and the reservoir  22 . Steam and combustion gases (including carbon dioxide (CO 2 )) from the steam generator are injected into the reservoir  22  heating the heavy oil. It should be appreciated that as the heavy oil is heated the viscosity of the heavy oil is reduced. It is also contemplated that the injection of CO 2  into the reservoir  22  also increases oil volume and further reduces the oil viscosity. Nitrogen from the combustion gases also assists with reservoir pressurization. 
     In the second stage  30  of production, the steam and hot condensed water heat the oil in an area  32  surrounding the well  24 . Typically in a cyclic steam process, this stage  30 , sometimes referred to as a “soak phase” is held for a period of time to allow the heat to permeate the reservoir. In some oil reservoirs, no soak time is used. It should be appreciated that in the second stage  30 , the downhole apparatus  90  may remain or may be removed from the well  24 . Finally, in the third stage  34 , the heated oil and condensed water are extracted from the well  24  using conventional pumping or extraction techniques as is known in the art. 
     Referring now to  FIG. 3 , another extraction configuration is shown which uses a steam injector well  36  and an extraction or production well  38 . In this embodiment, an injector well  36  is formed through the layers  26  into the reservoir layer  22 . A parallel extraction well  38  is formed adjacent the injection well  36 . The direct-fired downhole steam system  20  is inserted into the injector well  36  to produce steam within the reservoir layer  22 . As the steam is produced, hot water condenses  40  into the layer  22  reducing the viscosity of the oil. As the oil viscosity lowers, the extraction well  38  may be used to pump the heavy oil from the reservoir layer  22 . It should be appreciated that in applications that allow use of the configuration of  FIG. 3 , that steam heating and oil extraction may occur in parallel. 
     It should be appreciated that the above description of oil extraction is exemplary and the claimed invention should not be so limited. The claimed invention may be used with any technique wherein the application of heat, pressure, co-injection of diluents, chemicals or solvents, or injections of H 2 O, CO 2 , N 2  or other gasses will facilitate the extraction of oil. It should be further appreciated that the application of steam to the oil reservoir may be cyclic steam stimulation, continuous (steam flood) or continuous (SAGD). 
     A third configuration for oil extraction is shown in  FIG. 4 , which is similar to the configuration of  FIG. 3  where both an injector well  36  containing the direct-fired downhole steam system  20  and an extraction well  38  are used in parallel. In this configuration, the injector well  36  is formed initially in a vertical orientation. As the well  36  extends from the surface, the direction of the well  36  changes to a more horizontal orientation and extends along the length of the reservoir layer  22 . The extraction well  38  is formed in a similar manner. In the embodiment shown, the horizontal portion of the extraction well  38  is positioned vertically below the injector well  36 . By heating the oil in an area vertically above the extractor well  38 , gravity may be used to assist the flow of oil into the extractor well  38 . 
     Referring now to  FIG. 5 , an embodiment is shown of the direct-fired downhole steam system  20  that includes a sub-surface module  42  and a support or surface module  44 . The surface module  44  includes all of the balance of plant components used to support the operations of the sub-surface module  42 . In an embodiment, the surface module  44  includes a control module  46  that is electrically coupled to an air module  48 , a water module  50 , a fuel module  52  and a production module  54 . The control module  46  may have distributed functionality (comprised of a plurality of individual modules), such as a data acquisition system  56  and a processing system  58  for example, or may be an integrated processing system. Control module  46  may also control the distribution of electrical power from the surface to the steam generator location. The fluid conduits along with the power and transmission lines from the surface module  44  are bundled together to extend from the surface to the location where the steam generator will operate. This group of conduits and lines is sometimes referred to as a capillary. In one embodiment, at least a portion of the conduits or lines are bundled prior to the well head to minimize the number of openings or ports in the well head. 
     The air module  48  provides combustion and cooling air to the sub-surface module  42 . The air module  48  may include an air treatment module  60  that receives the intake air and removes/filters undesirable contaminants. The treated air is then compressed with an air compressor  62  and stored in a high pressure storage module  64 . The water module  50  includes a water treatment module  66  that receives intake water. In one embodiment, the water module  50  receives water separated from the extracted oil from the production module  54 . The water treatment module  66  filters the water and removes undesired contaminants and transfers the cleaned liquid water into a storage module  68  where the water remains until needed by the sub-surface module  42 . The liquid water is removed from storage module  68  by a pumping module  70  which is fluidly connected to the sub-surface module  42 . Further, in other embodiments, it is contemplated that water may be supplied from a subterranean source, such as an aquifer or nascent water with little or no treatment for steam production at the oil reservoir level. 
     The fuel module  52  provides a fuel, such as but not limited to natural gas, propane, butane, produced/associated-gas, and syngas (including syngas derived from oil) for example, to the sub-surface module  42 . The fuel module  52  includes a storage module  72 , a fuel compressor  74  and a high pressure fuel storage module  76 . The production module  54  receives oil from the well  24 ,  38 . It should be appreciated that the direct-fired downhole steam system  20  may be used either with the single well configuration of  FIGS. 1-2  or the injector/extraction well configuration of  FIGS. 3-4 . The production module  54  may include a gas separation module  78  that receives a composition from the well  24 ,  38  that may include oil, water and gaseous by-products (N 2 , CO 2 ). The gas separation module  78  removes the gaseous products from the composition and transfers these by-products to a cleaning module  80  which processes the gases prior to exhausting to the atmosphere. In one embodiment, a pressure energy recovery system (not shown) may be used instead of exhausting the gases, with potential use of the energy in the compression subsystems or otherwise. The energy recovered from the pressure recovery system could then be used to offset compression power or provide electrical power for support equipment. 
     The de-gassed composition exits the gas separation module  78  and is transferred to a water separation module  82 . As discussed above, the water separation unit  82  may be used to remove water from the oil and transfer the water to the water module  50 . In one embodiment, make up water  83  may be added to the water supply prior to or in connection with the inlet to the water module  50 . The oil from water separation unit  82  is transferred to an oil treatment module  84  prior to being transferred offsite applications. These treatments may include processes such as de-sulphurization, cracking, reforming and hydrocracking for example. In one embodiment, a monitoring module  86  provides data acquisition and monitoring of the oil reservoir. It should be appreciated that the monitoring module  86  may be integrated into control module  46 . It should be appreciated that the water separation or other processes could occur before or simultaneously with the de-gassing operation as may be advantageous. 
     Referring now to  FIG. 5  and  FIG. 6 , the data, power, air, water and fuel conduits from the surface modules  46 ,  48 ,  50 ,  52 ,  54  are transferred via a connection  88 , sometimes referred to as an umbilical or capillary, to a downhole apparatus  90 . As discussed above, portions of the conduits may be bundled together before or after the well-head. When installed, the downhole apparatus  90  is positioned within a well casing  98  ( FIG. 7 ) near the location where the steam is injected into the formation/reservoir. This could be near the terminal end of the well or at an intermediate location along its length. At the intermediate location, the well casing may have a packer utilized to prevent steam from bypassing the injection zone by preventing or inhibiting steam from flowing along the casing. The downhole apparatus  90  shown in  FIGS. 6-8  receives the air and fuel from the umbilical  88  at an interface  92  where it is transferred into a mixer portion  94 . The mixer portion  94  divides the supplied air into a first portion and a second portion. As will be discussed in more detail below, the first portion is mixed with fuel while the second portion is used for cooling prior to combustion. The interface  92  further allows the supplied diluent (e.g. water) to flow into the system casing  95  where the diluent flows along the length of the steam generator towards an opposing end. 
     From the mixer portion  94 , the fuel-air mixture and cooling-air flow through an injector portion  96  where the fuel-air mixture flows over a catalytic reactor while the cooling air passes over the conduits carrying the fuel. The injector portion may be similar to that described in commonly owned U.S. Pat. Nos. 6,174,159 or 6,394,791 entitled “Method and Apparatus for a Catalytic Firebox Reactor”, both of which are incorporated herein by reference in their entirety. The fuel-air mixture and cooling air are recombined at an end  99  where the recombined flows are ignited and burned within the combustor  100  generating temperatures up to 3992° F. (2200 C) for example. It should be appreciated that the temperature of the combustion gasses may be higher or lower depending on the fuel and oxidant used. The hot combustion gas flows into a steam generator portion  102  where water from the system casing  95  flows through spray nozzles  104  into the combustion gas to generate steam. It should be noted that in another embodiment oxygen or oxygen enriched air could be substituted for air in the combustion process. 
     The diluent (e.g. steam) and combustion gas exit the downhole apparatus at a terminal end  106  where the diluent and combustion gas enter the well casing  98  and may exit into the oil reservoir via perforations  108  ( FIG. 7 ). The perforations  108  allow the diluent (e.g. steam) and heat to penetrate the heavy oil reservoir as described herein above. In other embodiments, the well casing  98  may not have perforations and the diluent (e.g. steam) flows through an end of the well casing (open hole configuration) or the terminal end  106  is placed directly in the oil reservoir. In still other embodiments, the well casing may have slotted openings or screens. 
     It should be appreciated that due to the temperatures generated by the downhole apparatus  90 , thermal expansion may cause components of the mixer  94 , injector  96 , combustor  100  and d generator portion  102  to expand, bend or otherwise deform. In one embodiment, to accommodate this expansion, a plurality of ribs  107  are disposed between the injector  96  and the inner surface of the system casing  95 . In an embodiment, there are three sets of ribs arranged along the length of the downhole apparatus  90 , each set having three ribs disposed (equidistant) about the circumference of the mixer  94 , injector  96  and the steam generator portion  102 . The ribs  107  function to maintain the mixer  94 , injector  96 , combustor  100 , and steam generator portion  102  centered within the system casing  95 . The ribs  107  have a curved outer surface that allows the ribs  107  to slide along the system casing  95  as components expand. In one embodiment, the mixer  94 , injector  96 , combustor  100  and steam generator portion  102  are fixed to the system casing  95  at the terminal end  106 . As a result, thermal expansion will move the mixer  94 , injector  96 , combustor  100  and steam generator portion  102  towards the inlet. The use of flexible tubing within the interface  92  accommodates expansion of components during operation. In other embodiments, thermal expansion may be accommodated using a bellows system or other means. 
     Referring now to  FIG. 9 , an embodiment of the interface  92  is shown. In this embodiment, the interface  92  includes an end  110  having a plurality of ports on the end of the system casing  95 . The ports provide a point of entry for the conduits, data and power lines of the umbilical  88  ( FIG. 5 ). In one embodiment, the system casing  95  is a 3 inch (76.2 mm) stainless steel pipe. Diluent, such as water, is received into the casing from conduit  112 , such as a 1.5 inch (38.1 mm) tube for example. The water is received into an interior  113  of the system casing  95  and flows through a conduit defined by the inner surface of the system casing and the outside surfaces or the combustor and steam generator towards the opposite end  106  ( FIG. 8 ) where the water is sprayed into the combustion gas to generate steam. It should be appreciated that the flow of water over the components in the downhole apparatus  90  facilitates cooling of the injector  96 , combustor  100  and steam generator portion  102 . Air is received from a pair of conduits  114  (only one air conduit is shown for purposes of clarity), while fuel is received via conduit  115 . In an embodiment, the conduits  114 ,  115  are fabricated from flexible tubing. In an embodiment, the conduits  114 ,  115  are made from 0.5 inch (12.7 mm) stainless steel tube for example. As discussed above, the flexible tubing allows the interface  92  to accommodate thermal expansion that occurs during operation. 
     The ports in end  110  further allow data and electrical port transmission lines  117  to enter the system casing  95 . These lines may be used for transmitting electrical power, such as to a spark igniter or a resistance heater for example. Other lines may be used for transmitting data, such as from thermocouples for example, that allow the control module  46  to monitor the operation of the downhole apparatus  90 . Other lines may also be used to control valves or other flow components for system control. 
     Referring now to  FIG. 10  an embodiment of mixer  94  is shown that mixes the fuel from conduit  115  with a portion of the air from conduits  114 . In one embodiment, the fuel is received into a fuel injection bar  124  that injects the fuel into an interior cavity  127  via a plurality of nozzles  125 . Simultaneously, air is received from conduits  114  into a balancing chamber  118  which divides the air into a first and second fluid path. The balancing chamber includes a plurality of openings  122  and an outlet  123 . The openings  122  are disposed about the inner tube circumference of the chamber  118 . In this embodiment, the size of the openings  122  and the outlet  123  are configured to allow a first portion of the air to flow along a first fluid path through the gaps  121  between the fuel injection bar  124  and the housing  120 . The first portion of air then flows into cavity  127  while the second portion of air passes through the openings  122  along a second fluid path to the output port or outlet  123 . In one embodiment, the first portion comprises 20% of the air and the second portion comprises 80% of the air. As will be discussed in more detail below, the second portion of air is cooling air for the injector  96 . The cavity  127  allows air and fuel to mix and is defined by the cooling air conduit  128  and a housing  130 . The air-fuel mixture then flows along the length of the mixing portion  94  to outlet ports  126 . 
     Air flowing through the outlet  123  passes into the interior of conduit  128 . In one embodiment, the conduit  128  is conically shaped having a first end adjacent the outlet  123  having a smaller diameter than the opposite end  134 . In one embodiment, the ignition device, such as spark igniter  133  or resistance heater  135  for example, may be arranged within the conduit  128 . It should be appreciated that ignition device may be connected to electrical power or data lines  117  (not shown in  FIG. 10  for clarity). It should further be appreciated that in some embodiments, the downhole apparatus  90  may only have one ignition device, such as either the spark igniter or the resistance heater for example. In other embodiments, the ignition source may be formed by injecting hydrogen into the fuel supply. The hydrogen reacts with the catalyst discussed below to auto-ignite the fuel air mixture. 
     In one embodiment, the air-fuel mixture flows radially as shown in  FIGS. 11A-11B  into the injector  96  from the mixer outlet port  126 . The injector  96  comprises a housing  136  which receives the second portion of air (cooling air flow) from the end  134  and routes the second portion of air into a fluid path defined by the interior surface of a plurality of tubes  138 . The exterior surface of the tubes  138 , which defines another fluid path, is coated with an oxidation catalyst as will be discussed in more detail below. In one embodiment, the tubes  138  are coupled to an end plate  140 . The end plate  140  causes the second air portion to flow into the tubes  138  and prevents intermixing of the cooling air with the air-fuel mixture. The air-fuel mixture enters the injector  96  via the ports  126  and flows along a space defined by the interior wall  142  of the housing  136  and the exterior surfaces of tubes  138 . As such, the fuel-air mixture contacts the oxidation catalyst. 
     The catalyst coating used in the present invention, where the fuel is a hydrocarbon and air or oxygen is the oxidizer, may include precious metals, group VIII noble metals, base metals, metal oxides, or any combination thereof. Elements such as zirconium, vanadium, chromium, manganese, copper, platinum, gold, silver, palladium, osmium iridium, rhodium, ruthenium, cerium, and lanthanum, other elements of the lanthanide series, cobalt, nickel, iron and the like may also be used. The catalyst may be applied directly to the substrate, or may be applied to an intermediate bond coat or wash coat composed of alumina, silica, zirconia, titania, manesia, other refractory metal oxides, or any combination thereof. 
     It should be appreciated that during operation, the fuel-air mixture reacts with the catalyst coating on the exterior surface of the tubes  138  forming an exothermic reaction. By flowing the air through the interior of the tubes  138 , the temperature of the injector  96  may be maintained within a desired operating range for the materials used while also preheating the cooling air prior to combustion. In the one embodiment, the injector  96  includes sixty-one (61) tubes  138  having an outer diameter of 0.125 inches (3.175 mm) and are made from a suitable high temperature material, such as utilized in an aerospace industry (e.g. titanium, aluminum, nickel or high temperature capable super alloys). Other number of and diameter of tubes could be utilized in the device depending on the desired output, diameter or the operating conditions. 
     In one embodiment shown in  FIGS. 11C and 11D , the injector  96  includes one or more igniter devices  133 . In this embodiment, the igniter devices  133  include a body member  137  and a conductive core  139 . The body member  137  is made from a heat resistant, electrically insulation material, such as a ceramic for example. The body member  137  extends from the mixer portion  94  through the injector  96  and has an end that extends to the end  144 . The igniter device  133  may be located on the periphery of the injector  96  adjacent to or interspersed between the outer-row of tubes  138 . 
     The conductive core  139  extends through the middle of the body member and has an electrode  141  arranged on one end that extends at least partially into the combustor  100 . The conductive core  139  is electrically coupled to a power source, such as via control module  46 , to a battery arranged internal to the downhole apparatus, or to an internal power generator such as a thermoelectric generator for example. Conductive core  139  is configured to generate an electrical arc from the electrode  141  to the housing  136 . In another embodiment, the electrode is oriented to generate the electrical arc to the end of tubes  138 . The generation of the electrical arc in the presence of the fuel-air mixture and the cooling air initiates combustion in the combustor  100 . 
     The pair of igniter devices  133  may be located opposite each other (opposite corners), or substantially opposite (one in corner, the other arranged on the middle of an opposite side). It should be appreciated that while embodiments herein discuss the use of a pair of igniter devices  133  this is for example purposes and the claimed invention should not be so limited. The use of a pair of igniter devices is preferred for redundancy purposes; however combustion may be initiated with a single igniter device  133 . 
     Referring now to  FIG. 12 , the cooling air and the air-fuel mixture exit the injector  96  at the opposite end  144  and enter the combustor  100 . An igniter, such as igniter  133  for example, is arranged adjacent the end  144  and initiates combustion of the fuel and air. In an embodiment, the temperature of the combustion gas is about 3992° F. (2200 C). As discussed above, the combustion gas temperature may be higher or lower based on the fuel and oxidant used. The combustor  100  includes a liner  145  which receives the air and fuel and is where the combustion occurs. Adjacent the end  144 , a plurality of fins  146  extend radially about the periphery of the exterior of the liner  145 . It should be appreciated that the fins  146  facilitate heat transfer from the liner  145 . In one embodiment, the fins  146  extend along a portion of the liner  145 . In one embodiment, the fins  145  may be formed from a series of sequential fins (e.g. three), or may be formed from a single unitary and monolithic fin. Disposed between the fins  145  and the system casing  95  is a shroud  148 . The shroud  148  includes an inlet  150  that tapers from the inner diameter of the system casing  95  to the outer diameter of the fins  146 . It should be appreciated that the shroud  148  causes the diluent, such as water, flowing through the system casing  95  into a channel  154  defined between the inner diameter of the shroud  148  and the outer diameter of the liner  145 . The water flows through the channel  154  to an outlet  152  which tapers outward to the inner diameter of system casing  95 . 
     The combustion gases flow from the combustor  100  into the generation portion  102 . The generation portion  102  extends from the outlet  152  to the terminal end  106 . In an embodiment where the diluent is water, the generation portion  102  generates steam. In this embodiment, the steam generation portion  102  shown in  FIG. 13  includes a housing  156  having a plurality of nozzles  104  that spray water from the system casing  95  into the combustion gases. It should be appreciated that due to the high temperature of the combustion gases, the water sprayed into the housing  156  is vaporized into steam. The steam and combustion gas mixture exit the housing  156  at the terminal end  106 . 
     In one embodiment, the nozzles  104  are configured to spray water in a direction that is at least partially towards the combustor  100 . In other words, the stream of water from the nozzles  104  is directed upstream or in a counter-flow configuration. In one embodiment, six (6) nozzles  104  are arranged on 30° angle relative to the centerline of the steam generator portion  102  and configured to spray the water in a 60° cone. In one embodiment, the nozzles  104  are offset from each other both longitudinally and circumferentially about the housing  156 . In one embodiment, adjacent nozzles  104  are circumferentially offset 60° relative to each other. The nozzles  104  may be configured to operate with dissolved solids in the supply water. 
     Referring to  FIG. 14 , one embodiment is shown for the nozzle assembly  160 . The nozzle assembly  160  includes the nozzle  104  and a boss member  162 . The boss member  162  has a generally cylindrically body with a hole extending therethrough. A portion of the hole is threaded to receive the external threads on the nozzle  104 . The front surface of the boss member  162  extends into the interior of the housing  156 . The leading and trailing surfaces are angled to reduce the drag profile of the boss member  162  within the combustion-gas/steam stream. In one embodiment, the nozzle  104  includes a filter to reduce the risk of clogging. In still other embodiments, nozzles may be pointed perpendicular to the flow or downstream of the flow. 
     It should be appreciated that embodiments described herein provide advantages in extracting heavy oil from reservoirs deep within the ground. Substantially all of the thermal energy generated is applied to the oil reservoir with little or no losses. These embodiments further allow the extraction of heavy oil while reducing water-usage and emissions and provide for the sequestration of CO 2 . As a result, embodiments of the subject invention reduce the overall cost per barrel of produced heavy oil. 
     Further, the non-condensable portions of the steam and combustion gas mixture may pressurize the reservoir to facilitate flow of oil through the production/extraction well and may contribute to slowing the rate of heat loss to the overburden. Further, the increase of CO 2  within the oil from the combustion gas mixture increases oil volume and may reduce viscosity to further facilitate oil flow. As a result, the subject invention may provide advantages in reducing or eliminating the parasitic loads (e.g. pumps) used in the extraction of oil, and may provide a source of non-condensable gases and heat for the purpose of producing even lighter fractions of oil than heavy. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.