Abstract:
A well configuration is provided comprising an injection well ( 102 ) completed relatively high in an oil reservoir ( 100 ) and a production well ( 103-106 ) completed relatively low in the reservoir ( 100 ). The production well has a horizontal leg ( 107 ) oriented generally perpendicularly to a generally linear and laterally extending, upright combustion front propagated from the injection well ( 102 ). The leg ( 107 ) is positioned in the path of the advancing front. Oil upgrading catalyst has been emplaced along the horizontal leg. The production well ( 103-106 ) is maintained open, thereby providing a low pressure sink which induces the front to advance along the leg. The hot combustion gases react with the commingled oil over the catalyst to provide in situ upgrading.

Description:
This application claims benefit of provisional application No. 60/069,182 filed Dec. 11, &#39;97 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a catalytic in situ process for upgrading hydrocarbons in an underground reservoir. More particularly, it relates to a process in which a catalyst is placed along the horizontal segment of a horizontal production well operating in a toe-to-heel configuration, which enables carbon monoxide and/or hydrogen produced in the reservoir or injected into the reservoir with steam, to pass sequentially with reservoir oil over the catalyst, immediately prior to being produced. 
     BACKGROUND OF THE INVENTION 
     Large supplies of heavy oil (ca. 8 to 15 degrees API) and medium oil (ca. 15-25 API) exist throughout the world, most notably in Venezuela, Canada and the U.S.A. Significant deposits are also to be found in the North Sea, China and Romania. The composition of the crude oil barrel is inexorably moving towards this heavier material, but it is relatively uneconomic to produce. Without upgrading to produce an oil of lighter composition, i.e. containing more white oil distillates (gasoline, diesel, etc.), heavy oil has very limited potential, historically trading at around $9.00 below the price of conventional oil. While surface upgrading technology (H-Oil, Vega-Combi or LC Fining processes) is possible, the payout time on the very large investment required is long (ca.ten years), which is discouraging to commercialization. 
     In situ oil upgrading has several advantages over conventional surface upgrading technologies. Because in situ upgrading (reaction occurring underground) can be implemented on a well-by-well basis, there is no need for large capital-intensive projects. Rather, the size of an in situ project for a particular field can be tailored to available production rates. Thus, in situ upgrading is practical even for those fields deemed too small to provide sufficient production for conventional surface upgrading processing. Additional advantages for in situ upgrading include the production of a more desirable and valuable product, ease in shipping and pipelining (minimum of 22 degree API gravity), and less demanding downstream processing (processable by a conventional refinery). 
     The requirements for an in situ upgrading process include: provision or a downhole bed of catalyst, achievement of appropriate high reaction temperatures and pressure at the catalyst bed, and mobilization of oil and co-reactants over the catalyst. Although the technologies to accomplish each of these tasks separately are known, their combination into a unified effective underground process has yet to be demonstrated in practice. 
     Because it is the most efficient method to achieve high temperatures in a reservoir without the direct application of heat, in situ combustion (ISC) is a promising oil recovery process to exploit in the development of an efficient and economical in situ upgrading process. 
     In-situ combustion processes are applied for the purpose of heating heavy or medium oil to mobilize it and drive it to an open production well for recovery. In general, the usual ISC technique used involves providing spaced apart vertical injection and production wells completed in a reservoir. Typically, an injection well will be located within a pattern of surrounding production wells. Air, or other oxygen-containing gases are injected into the formation. The mixture of air or oxidizing gas and hydrocarbons is ignited, a combustion front is generated in the formation and the resulting combustion front is advanced outwardly toward the production wells. Or, alternately, a row of injection wells may feed air to a laterally extending combustion front which advances as a line drive toward a parallel row of production wells. 
     In both cases the operator seeks to establish an upright combustion front which provides good vertical sweep and advances generally horizontally through the reservoir with good lateral sweep. However the processes are not easy to operate and are characterized by various difficulties. One such difficulty arises from what is referred to as gravity segregation. The hot combustion gases tend to rise into the upper reaches of the reservoir. Being highly mobile, they tend to penetrate permeable streaks and rapidly advance preferentially through them. As a result they fail to uniformly carry out, over the cross-section of the reservoir, the functions of heating and driving oil towards the production wells. The resulting process efficiency therefore is often undesirably low. Typically the volumetric sweep efficiencies are less than 30%. 
     Weissman et al (Energy and Fuels. 1996, 10.883,889) have recently proposed a modified in situ combustion process using a vertical well production strategy, in which a catalyst bed is emplaced around the production well. They have reported the results of two ISC tests, from which they concluded that a heated bed of hydrocracker catalyst placed in the bottom section of an 1.8 m long, 0.1 m diameter combustion tube (a special thin-walled reactor to simulate reservoir conditions), was effective in converting carbon monoxide, produced at the combustion front, and water, into carbon dioxide and hydrogen, via the water gas shift reaction. Not only was 50% of the sulphur removed by hydrodesulfurization (“HDS”), but there were also decreases in the oil density and viscosity obtained by the catalytic reaction. However, there were two main problems foreseen with this process: (1) the high retention of oil in the catalyst bed/gravel-pack (a large, one-place volume, with a vertical producer well), would lead to severe coking of the catalyst; and 2) the need to operate in either a cyclic mode (backflow on the injector well), or with a severe gas override condition to provide heat to the catalyst bed. Both processes possibly require supplementary downhole heating, which is both expensive and risky. Also, very importantly, the extremely acidic process gases (carbon dioxide and sulfur dioxide) entering the vertical production well, in combination with a temperature of over 300 degrees Celsius, will cause severe corrosion to the vertical well, through which all production fluids must pass. In the case of deliberate combustion-gas override (which is used to achieve high temperatures at the vertical well), very poor reservoir sweep will be achieved and the possibility of oxygen breakthrough is increased, which could cause a serious explosion hazard. In the case that the proposed cyclic combustion process is used (again to achieve high temperatures at the vertical production well), the production rates will be at least halved because of the required air injection time in the same well. In summary, the two proposed catalytic in situ processes appear expensive and difficult to operate, and so are not felt to be feasible. 
     A new viscous oil recovery process has recently been developed which provides a substantial increase in reservoir sweep efficiency over that of the traditional ISC process. A combination of wells is used wherein the toes of horizontal production wells are the first segments to provide hydrocarbon production and to come into contact with the injected gases. Greaves and Turta, in U.S. Pat. No. 5,626,191, disclose such a well configuration, which they call the “toe-to-heel” oil displacement process. The patent applies to any process where gases are injected to reduce the viscosity of oil in an underground reservoir, and includes oxidizing gases for in situ combustion, steam injection, steam injection along with other gases, and hydrocarbon solvent gases. 
     Many oilfield operators are reluctant to apply the in situ combustion process because of historically poor performance when used in a traditional vertical well drive mode, and so an in situ upgrading process that uses steam would be more appealing. Since some heavy or medium gravity oil reserves are found in relatively deep and hot reservoirs, for example in the Orinoco Belt in Venezuela, high temperature steam can be utilized to provide the heat for an in situ upgrading process in some cases. 
     In summary of the prior art, it has been recognized as very desirable to achieve oil upgrading in an underground reservoir and the ISC process has been proposed as a possible heat source, but an effective process for implementing these steps has not yet been developed. The work underlying the present invention was undertaken to reach this objective. The present invention will now be described. 
     SUMMARY OF THE INVENTION 
     Considering the disclosure of U.S. Pat. No. 5,626,191 of Greaves and Turta that: 
     1. if a generally linear and laterally extending, upright combustion front is established and propagated high in an oil-containing reservoir: and 
     2. if an open production well is provided having a horizontal leg positioned low in the reservoir so that the well extends generally perpendicularly to and lies in the path of the front and has its furthest extremity (“toe”) spaced from but adjacent to the injection sources; then 
     3. the production well will provide a low pressure sink and outlet that functions to induce the lateral sweep front to advance in a guided and controlled fashion, first intersecting the toe and then proceeding along the length of the horizontal leg - under these circumstances, the oil displacement front will remain generally stable and upright and be characterized by a relatively high reservoir sweep efficiency; and 
     4. the unreacted injectant gases and reaction gases will flow through the swept portion of the reservoir and through the vertical reaction front and react with the oil at the front. Streamlines of the gases will bend towards the horizontal leg, due to the downward flow gradient created by the action of the production well as a sink, but will also rise due to gravity phase segregation, resulting in a net vertical front advancing laterally without significant over-riding. In the case of steam injection, the condensed water and heated oil will, along with any gases present, likewise flow down to the low pressure sink. In the case of in situ combustion the gases will be combustion gases: carbon monoxide, carbon dioxide, sulphur dioxide and water vapor. 
     Now, in accordance with the present invention: 
     if an appropriate oil upgrading catalyst is placed along the horizontal leg of a production well arranged in toe-to-heel configuration, including any of within the leg, on the leg or in the reservoir around the leg; then 
     hot combustion gases from an ISC process, or steam from a steam injection process combined with injected reducing gases, such as carbon monoxide or hydrogen, will react with the commingled oil over the catalyst at appropriate temperature and pressure and the oil will be substantially upgraded. 
     When compared in experimental runs with a conventional toe-to-heel (“TTH”) in situ combustion process in accordance with the Greaves and Turta patent, without catalyst in the vicinity of the horizontal leg of the oil producing well, the present invention was found to be relatively characterized by: 
     increased average API gravity of produced oil; 
     reduced oil viscosity; 
     reduced oxygen and carbon monoxide and increased carbon dioxide levels in the produced gas stream; 
     extensive hydrodesulfurization of the oil; and 
     extensive hydrodemetallization of the oil. 
     Additionally, the present process benefits from being a single pass catalytic process so that the reactant oil and gases continuously access fresh catalyst. The distributed catalyst along the horizontal well maintains high conversion activity by virtue of sequential catalyst exposure caused by the advancing movement of the combustion front from the toe to the heel of the horizontal well. 
     Therefore, in broad terms, the invention is a process for upgrading oil in an underground reservoir while the oil is recovered through a production well, comprising: providing an injection well for injecting a gaseous fluid into the reservoir to form an advancing, laterally extending displacement front operative to reduce the viscosity of reservoir oil; providing at least one open production well having a horizontal leg completed relatively low in the reservoir and positioned substantially perpendicular to and in the path of the advancing front; emplacing oil upgrading catalyst along the leg&#39;s length; injecting the gaseous fluid into the injection well and advancing the displacement front along the leg; and producing the production well to recover upgraded oil from the reservoir. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view schematically showing a sand pack with simulated vertical injection wells and a perpendicularly arranged, horizontal production well, said injection wells and production well being completed relatively high and low in the pack, respectively, as in the base case of the Greaves and Turta prior art, and reported below for Runs  971  and  972 ; 
     FIG. 2 is a perspective view schematically showing a sand pack with simulated vertical injection wells and a perpendicularly arranged, horizontal production well, said injection wells and production well being completed relatively high and low in the pack, respectively, as in FIG. 1, but with the placement of upgrading catalyst around the horizontal segment of the horizontal well, and reported below for Runs  975  and  976 ; 
     FIGS. 3 a,    3   b,    3   c  are top, side and end views of the test cell employed in demonstration of the present invention for the toe-to-heel process when operated in the catalytic upgrading mode in Runs  975  and  976 ; 
     FIG. 4 is a flow diagram showing the laboratory set-up, including the test cell of FIGS. 3 a - 3   c,  used to conduct the experimental runs reported on below; 
     FIGS. 5 a  and  5   b  show gas chromatographic spectra for Wolf Lake crude oil used in the test runs, and produced oil from the catalytic wet ISC Run  976  of the present invention, respectively; 
     FIG. 6 is a plan view showing a preferred field embodiment of the well layout; 
     FIG. 7 is a side cross-section taken along the line XII—XII of the well arrangement of FIG. 6; and 
     FIGS. 8 a,    8   c  and  8   e  are horizontal thermal contour plots for three layers in the sand pack after 6 hours of operation during Run  7 —FIGS. 8 b,    8   d  and  8   f  are vertical cross-section thermal contour plots. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention was developed in the course of carrying out an experimental investigation involving test runs carried out in a test cell or three dimensional physical model. 
     More particularly, a test cell  1 , shown in FIGS. 3 a,    3   b  and  3   c  was provided. The cell comprised a rectangular, closed, thin-walled stainless steel box  2 . Dimension-wise, the box  2  formed a chamber  3  having dimensions 40×40×10 cm (total volume 16,000 c.c.). The thickness of each box wall was 4 millimeters. The chamber  3  was filled with a sand pack  4  consisting of a mixture of sand, clay, oil and water. The composition of the uniform mixture charged into the chamber  3  and other bed properties shown below in Table 1. 
     The porosity of the sand pack  4  was about 38.5% and the permeability was about 1.042 darcys. 
     The loaded cell box  2  was placed inside a larger aluminum box  5  and the space between them was filled with vermiculite powder insulation. 
     Sixty type K thermocouples  6 , positioned at 6 cm intervals as shown in FIGS. 3 a,    3   b,    3   c  and  4 , extended through the wall of the cell  1  into the sand pack  4 , for measuring the three dimensional temperature distribution in the sand pack  4 . 
     To compensate for heat losses, the cell  1  was wound with heating tape (not shown). This heat source was controlled manually, on demand, in response to the observed combustion peak temperature and adjacent well temperature values. The temperature at the wall of the cell was kept a few degrees Celsius less than the temperature inside the sand, close to the wall. In this way, the quasi-adiabatic character of the run was assured. 
     A cell heater  7  was embedded in the top section of the sand pack  4  at the air injection end, for raising the temperature in the region of the injection well  8  to ignition temperature. 
     Simulated air injection wells  8  were provided at the injection end of the cell  1 . A simulated production well  9  was provided at the opposite or production end of the cell  1 . 
     For Runs  975  and  976 , a 0.25 inch diameter cylindrical catalyst bed was placed around the horizontal leg, whereas, for Runs  971  and  972 , which constitute demonstrations of prior art for comparison purposes, the catalyst bed was omitted. 
     The positioning and vertical or horizontal disposition of the wells  8 ,  9  are shown schematically in FIGS. 1,  2  and  3   a - 3   c  for the four test runs reported on below. This well configuration is referred to as the direct line drive configuration. However, other well configurations are also contemplated, such as staggered line drive where the vertical injection wells are placed between the horizontal legs, or a horizontal injection well is placed relatively high in the reservoir to simulate the effect of a number of vertical injectors by having periodic perforations as a means to distribute the injectant gas. In the case that the reservoir heating is accomplished by injection of steam, the appropriate location of the steam injectors will be reservoir-specific and may not be high in the reservoir. 
     As shown in FIG. 1 for non-catalytic Runs  971  and  972 , a horizontal injection well  8  was placed relatively high in the cell, while the production well  9  was horizontal and placed relatively low in the test cell with its toe slightly displaced from the injection well. Non-catalytic Runs  971  and  972  were a demonstration of prior art (Greaves and Turta) and were conducted for comparison purposes only. Run  971  was a dry ISC process, and Run  972  was a wet ISC process. There was no catalyst present for these Runs. 
     As shown in FIGS. 2 and 3 a - 3   c,  for catalytic Runs  975  and  976 , a horizontal injection well  8 , positioned laterally across the sand pack  4 , was provided. The injection well was located relatively high in the sand pack. The production well  9  was horizontal, elongated, positioned low in the sand pack and had its toe adjacent to but spaced from the injection well. The horizontal production well  9  was arranged to be generally perpendicular to a laterally extending combustion front developed at the injection source. However, the toe  10  of the production well was spaced horizontally away from a vertical projection of the injection well. An elongated ring of catalyst,  11 , was placed around the horizontal well  9 . 
     The oil upgrading catalyst employed in Runs  975  and  976  was a standard hydrotreating/HDS catalyst manufactured by Akzo Chemie Nederland bv. Amsterdam, and identified as Ketjenfine 742-1, 3AQ. 
     Each of the injection and production wells  8 , 9  were formed of perforated stainless steel tubing having a bore 4 mm in diameter. The tubing was covered with 100 gauge wire mesh (not shown) to exclude sand from entering the tubing bore. 
     The combustion cell  1  was integrated into a conventional laboratory system shown in FIG.  4 . The major components of this system are now shortly described. 
     Air was supplied to the injection well  18  from a tank  19  through a line  20 . The line  20  was sequentially connected with a gas dryer  21 , mass flowmeter  22  and pressure gauge  23  before reaching the injection well  8 . Nitrogen could be supplied to the injection well  8  from a tank  24  connected to line  20 . Water could be supplied to the injection well  8  from a tank  27  by a pump  25  through line  26 . Line  26  was connected with line  20  downstream of the pressure gauge  23 . A temperature controller  28  controlled the ignition heater  7 . The produced fluids passed through a line  30  connected with a separator  31 . Gases separated from the produced fluid and passed out of the separator  31  through an overhead line  32  controlled by a back pressure regulator  33 . The regulator  33  maintained a constant pressure in the test cell  1 . The volume of the produced gas was measured by a wet test meter  34  connected to line  32 . The liquid leaving the separator was collected in a cylinder  40 . 
     Part of the produced gas was passed through an oxygen analyzer  36  and gas chromatograph  37 . Temperature data from the thermocouples  6  was collected by a computer  38  and gas composition data was collected from the analyzer  36  and gas chromatograph  37  by an integrator  39 . 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 BED PROPERTIES 
               
             
          
           
               
                 Run Code 
                 971 
                 973 
                 975 
                 976 
               
               
                   
               
               
                 Bed Type 
                 Uncon 
                 Uncon 
                 Uncon 
                 Uncon 
               
               
                 Sand Type 
                 Silica. W50 
                 Silica. W50 
                 Silica. W50 
                 Silica. W50 
               
               
                 Sand wt % 
                 97 
                 97 
                 97 
                 97 
               
               
                 Clay wt % 
                 3 
                 3 
                 3 
                 3 
               
               
                 kaolinite 
               
               
                 Porosity % 
                 38.5 
                 38.5 
                 38.5 
                 38.5 
               
               
                 Permeability 
                 1042 
                 1042 
                 1042 
                 1042 
               
               
                 (md) 
               
               
                 S oi  % 
                 76 
                 76 
                 76 
                 76 
               
               
                 S wi  % 
                 17 
                 17 
                 17 
                 17 
               
               
                 S gi  % 
                 7 
                 7 
                 7 
                 7 
               
               
                 Initial 
                 18 
                 17 
                 18 
                 17 
               
               
                 Temperature 
               
               
                 (Deg C.) 
               
               
                   
               
             
          
         
       
     
     Air was injected at a rate of approximately 6.0 l/m. and ignition was initiated using the heater  7 . The tests were typically continued for up to 11 hours for the dry ISC Runs  971 ,  975  and for 7.5 hours for the wet ISC Runs  972 ,  976 . In the runs where water was added, its rate was 0.025 l/m. Details of the operating conditions are provided in Table 2. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 OPERATING CONDITIONS 
               
             
          
           
               
                 Run Code 
                 971 
                 972 
                 975 
                 976 
               
               
                   
               
               
                 Combustion 
                 Dry 
                 Wet 
                 Dry 
                 Wet 
               
               
                 Mode 
               
               
                 Catalyst 
                 no 
                 no 
                 yes 
                 yes 
               
               
                 Air flux 
                 9 
                 9 
                 9 
                 9 
               
               
                 (m 3 /m 2  · hr) 
               
               
                 Oxygen flux 
                 1.89 
                 1.89 
                 1.89 
                 1.89 
               
               
                 (m 3 /m 2  · hr) 
               
               
                 Air Injection 
                 6 
                 6 
                 6 
                 6 
               
               
                 Rate (l/min) 
               
               
                 Water Air 
                 0 
                 0.0042 
                 0 
                 0.0042 
               
               
                 Ratio (m 3 /m 3 ) 
               
               
                 Water 
                 0 
                 0.025 
                 0 
                 0.025 
               
               
                 injection rate 
               
               
                 (l/min) 
               
               
                 Initial 
                 18 
                 17 
                 18 
                 17 
               
               
                 Temperature 
               
               
                 (Deg C.) 
               
               
                 Operating 
                 25 
                 25 
                 25 
                 25 
               
               
                 pressure 
               
               
                 (psig) 
               
               
                 Well Type 
                 HI-HP 
                 HI-HP 
                 HI-HP 
                 HI-HP 
               
               
                 Well 
                 Line Drive 
                 Line Drive 
                 Line Drive 
                 Line Drive 
               
               
                 Configuration 
               
               
                 Back 
                 24.4 
                 24.3 
                 24.5 
                 24.4 
               
               
                 pressure set 
               
               
                 point (psig) 
               
               
                   
               
             
          
         
       
     
     Legend 
     HI=Horizontal Injector 
     HP=Horizontal Producer 
     Following completion of each run, an analysis of the cell sand pack  4  was undertaken to determine the volumetric sweep efficiency. The analysis comprised a physical removal of successive vertical layers of the sandpack at 3 cm intervals and determining the extent of the burned zone by measuring the oil and coke content. In this way the volumetric sweep of the burning front was determined postmortem and compared with that obtained from the peak temperature profiles during the run. The results of the four Runs are set forth in Table 3. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 SUMMARY OF RESULTS 
               
             
          
           
               
                 Run Code 
                 971 
                 972 
                 975 
                 976 
               
               
                   
               
               
                 Combustion 
                 Dry 
                 Wet 
                 Dry 
                 Wet 
               
               
                 Mode 
               
               
                 Catalyst? 
                 no 
                 no 
                 yes 
                 yes 
               
               
                 Overall 
                 12.7 
                 7.5 
                 12.5 
                 7.3 
               
               
                 period (hrs) 
               
               
                 Pre-ignition 
                 1.98 
                 2.00 
                 2.30 
                 1.98 
               
               
                 period (hrs) 
               
               
                 Air injection 
                 10.7 
                 5.5 
                 10.2 
                 5.3 
               
               
                 period (hrs) 
               
               
                 Dry phase 
                 10.7 
                 2.4 
                 10.2 
                 2.6 
               
               
                 period (hrs) 
               
               
                 Wet phase 
                 0 
                 3.1 
                 0 
                 2.7 
               
               
                 period (hrs) 
               
               
                 Peak temp 
                 621 
                 625 
                 629 
                 627 
               
               
                 (dry phase) 
               
               
                 (deg C.) 
               
               
                 Stabilized 
                 452 
                 455 
                 455 
                 451 
               
               
                 temp (dry 
               
               
                 phase) (deg C.) 
               
               
                 Peak temp 
                 N/A 
                 477 
                 N/A 
                 468 
               
               
                 (wet 
               
               
                 phase) (deg C.) 
               
               
                 Stabilized 
                 N/A 
                 393 
                 N/A 
                 402 
               
               
                 temp (wet 
               
               
                 phase) (deg C.) 
               
               
                 CO2 % (dry 
                 14.3 
                 14.2 
                 16.5 
                 16.5 
               
               
                 stabilized) 
               
               
                 CO % (dry 
                 4.0 
                 4.0 
                 2.4 
                 2.3 
               
               
                 stabilized) 
               
               
                 O2 % (dry 
                 1.10 
                 1.18 
                 0.85 
                 0.93 
               
               
                 stabilized) 
               
               
                 CO2 % (wet 
                 N/A 
                 13.9 
                 N/A 
                 17.1 
               
               
                 stabilized) 
               
               
                 CO % (wet 
                 N/A 
                 3.5 
                 N/A 
                 0.3 
               
               
                 stabilized) 
               
               
                 O2 % (wet 
                 N/A 
                 2.3 
                 N/A 
                 1.6 
               
               
                 stabilized) 
               
               
                 H2 % 
                 N/A 
                 N/A 
                 1.9 
                 5.8 
               
               
                 (calculated 
               
               
                 for 975 &amp; 976 
               
               
                 CO/CO + 
                 0.220 
                 0.200 
                 0.130 
                 0.017 
               
               
                 CO2 
               
               
                 H/C 
                 0.73 
                 0.71 
                 0.44 
                 0.33 
               
               
                 Air to Fuel 
                 9.485 
                 9.544 
                 9.457 
                 9.810 
               
               
                 requirements 
               
               
                 (Sm 3/kg) 
               
               
                 O2 to fuel 
                 2.00 
                 2.00 
                 2.00 
                 2.06 
               
               
                 requirements 
               
               
                 (Sm 3/kg) 
               
               
                 Fuel burned 
                 0.384 
                 0.186 
                 0.371 
                 0.181 
               
               
                 (kg) 
               
               
                 Fuel burned 
                 9.10 
                 4.40 
                 8.74 
                 4.27 
               
               
                 (% of OOIP) 
               
               
                 Oxygen 
                 94.8 
                 89.0 
                 96.0 
                 92.3 
               
               
                 utilization % 
               
               
                 (Average) 
               
               
                 Volumetric 
                 40.7 
                 43.0 
                 39.0 
                 38.7 
               
               
                 sweep 
               
               
                 efficiency % 
               
               
                 Fuel 
                 65 
                 30 
                 65 
                 32 
               
               
                 combustion 
               
               
                 (kg/m3) 
               
               
                 Air Oil ratio 
                 1328 
                 744 
                 1428 
                 738 
               
               
                 (m 3 /m 3 ) 
               
               
                 Water Air 
                 0 
                 0.0042 
                 0 
                 0.0042 
               
               
                 ratio (m 3 /m 3 ) 
               
               
                 Oil recovery 
                 67.9 
                 62.3 
                 60.4 
                 53.2 
               
               
                 % of OOIP 
               
               
                 Water 
                 91.3 
                 80.4 
                 71.1 
                 69.8 
               
               
                 recovery % of 
               
               
                 OOIP 
               
               
                 Combustion 
                 0.016 
                 0.024 
                 0.015 
                 0.022 
               
               
                 front velocity 
               
               
                 (m/hr) 
               
               
                   
               
             
          
         
       
     
     The produced gas analyses provide support for occurrence of the water gas shift reaction in the catalyst zone. The reaction is: CO+H2O=CO2+H2. Comparing the non-catalytic and catalytic dry ISC Runs,  971  and  975  respectively, the CO produced gas is 40% lower for the catalytic case (2.4% vs 4.0%). 
     Comparing the produced CO for the wet combustion cases, Runs 972 and  976 , the CO level is 91% lower when catalyst is present (0.31% vs 3.50%). 
     The CO2 levels are higher in the two catalyst Runs  975  and  976 , compared with the corresponding non-catalytic Runs  971  and  972 , which provides further support for the water gas shift reaction as a primary source of hydrogen in catalytic in situ upgrading. 
     The differences in recovery of the original water in place can be used to calculate the amount of hydrogen produced and consumed during in situ upgrading reactions; the result is 1.91% of the total produced gas phase for Run  975  dry catalytic ISC, and 5.8% for wet catalytic ISC Run  976 . 
     The results described above make it clear that any catalyst that has water gas shift activity would be beneficial and could be employed by itself or in any proportion in admixture with the hydrotreating/HDS catalyst used in Runs  975  and  976  or other such catalyst. 
     Since the water gas shift reaction produces the hydrogen required for oil upgrading, the process can be carried out by injecting high temperature steam and carbon monoxide. A carbon monoxide source, for example, oxygen-starved combustion of natural gas, will produce a gas elevated in CO which can be injected into the reservoir. In this way the key ingredients for effective in situ upgrading will be provided: these are heat, hydrogen and active catalysts. 
     Also to be noted as a benefit of catalytic ISC is the lower level of produced oxygen. Since each pair of non-catalytic and catalytic Runs were conducted under the same conditions, the oxygen reduction can be attributed to the presence of catalyst. 
     The analyses of produced oil are presented in Tables 4 and 5 for API gravity, density and viscosity at each half-hour interval. 
     The prior art toe-to-heel ISC process of Greaves and Turta provides considerable thermal upgrading as measured by the three aforementioned parameters (Runs  971  and  972 ), but still fall very short of the performance of the catalytic Runs  975  and  976  of the present invention. The average results are summarized in Table 6. Wet catalytic ISC improved the oil gravity from 11.0 API to 20.7 API and reduced the viscosity from 100,000 cps to 46 cps. Therefore the upgraded oil at a viscosity of 46 cps will be easily pipelined without the need for a diluent. Since diluent light hydrocarbons are expensive and in short supply this is a valuable benefit of the present invention. 
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 DRY NORMAL AND CATALYTIC 
               
             
          
           
               
                   
                 Run 971 (Dry Normal) 
                 Run 975 (Dry Catalytic) 
               
             
          
           
               
                 Time 
                 API 
                 Density 
                 Viscosity 
                 API 
                 Density 
                 Viscosity 
               
               
                   
               
             
          
           
               
                 0.5 
                 11.0 
                 0.993 
                 100000 
                 11.0 
                 0.993 
                 100000 
               
               
                 1 
                 11.0 
                 0.993 
                 100000 
                 11.3 
                 0.991 
                  97780 
               
               
                 1.5 
                 11.0 
                 0.993 
                 100000 
                 14.2 
                 0.971 
                  8220 
               
               
                 2 
                 11.1 
                 0.992 
                  98873 
                 14.6 
                 0.969 
                  7830 
               
               
                 2.5 
                 12.4 
                 0.983 
                  20234 
                 20.6 
                 0.930 
                   40 
               
               
                 3 
                 12.8 
                 0.981 
                  14060 
                 20.5 
                 0.931 
                   43 
               
               
                 3.5 
                 15.3 
                 0.964 
                  7435 
                 19.8 
                 0.935 
                   62 
               
               
                 4 
                 14.8 
                 0.967 
                  7675 
                 19.5 
                 0.937 
                   68 
               
               
                 4.5 
                 14.5 
                 0.969 
                  8020 
                 19.3 
                 0.938 
                   74 
               
               
                 5 
                 14.1 
                 0.972 
                  8430 
                 19.2 
                 0.939 
                   82 
               
               
                 5.5 
                 14.3 
                 0.971 
                  8160 
                 18.9 
                 0.941 
                   97 
               
               
                 6 
                 14.0 
                 0.973 
                  8570 
                 18.6 
                 0.943 
                   104 
               
               
                 6.5 
                 13.8 
                 0.974 
                  9010 
                 18.4 
                 0.944 
                   111 
               
               
                 7 
                 13.7 
                 0.945 
                  9035 
                 18.3 
                 0.945 
                   117 
               
               
                 7.5 
                 13.9 
                 0.973 
                  8660 
                 18.2 
                 0.945 
                   123 
               
               
                 8 
                 14.0 
                 0.973 
                  8550 
                 18.5 
                 0.943 
                   106 
               
               
                 8.5 
                 13.8 
                 0.974 
                  8990 
                 18.0 
                 0.946 
                   133 
               
               
                 9 
                 13.6 
                 0.975 
                  9050 
                 18.3 
                 0.945 
                   118 
               
               
                 9.5 
                 13.2 
                 0.978 
                  9780 
                 18.4 
                 0.944 
                   110 
               
               
                 10 
                 13.4 
                 0.977 
                  9580 
                 18.2 
                 0.945 
                   123 
               
               
                 10.5 
                 13.5 
                 0.976 
                  9440 
                 18.3 
                 0.945 
                   118 
               
               
                 11 
                 13.3 
                 0.977 
                  9630 
                 18.1 
                 0.946 
                   129 
               
               
                 11.5 
                 13.4 
                 0.977 
                  9560 
                 18.0 
                 0.946 
                   132 
               
               
                 12 
                 13.1 
                 0.979 
                  9820 
                 18.3 
                 0.945 
                   118 
               
               
                 12.5 
                 13.2 
                 0.978 
                  9770 
                 18.4 
                 0.944 
                   109 
               
               
                 Average 
                 13.8 
                 0.972 
                  8903 
                 18.7 
                 0.948 
                   101 
               
               
                 (3.5-12.5 hrs) 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 WET NORMAL AND CATALYTIC 
               
             
          
           
               
                   
                 Run 971 (Dry Normal) 
                 Run 975 (Dry Catalytic) 
               
             
          
           
               
                 Time 
                 API 
                 Density 
                 Viscosity 
                 API 
                 Density 
                 Viscosity 
               
               
                   
               
             
          
           
               
                 0.5 
                 11.0 
                 0.993 
                 100000 
                 11.0 
                 0.993 
                 100000 
               
               
                 1 
                 11.0 
                 0.993 
                 100000 
                 11.7 
                 0.988 
                  95760 
               
               
                 1.5 
                 11.0 
                 0.993 
                 100000 
                 13.4 
                 0.977 
                  10043 
               
               
                 2 
                 11.2 
                 0.967 
                  99020 
                 15.1 
                 0.965 
                  6320 
               
               
                 2.5 
                 14.8 
                 0.971 
                  7690 
                 19.8 
                 0.935 
                   65 
               
               
                 3 
                 14.2 
                 0.975 
                  8210 
                 20.4 
                 0.932 
                   46 
               
               
                 3.5 
                 13.7 
                 0.976 
                  9015 
                 19.7 
                 0.936 
                   63 
               
               
                 4 
                 13.5 
                 0.974 
                  9460 
                 19.6 
                 0.936 
                   65 
               
               
                 4.5 
                 13.8 
                 0.977 
                  9000 
                 19.4 
                 0.938 
                   72 
               
               
                 5 
                 13.4 
                 0.977 
                  9560 
                 22.2 
                 0.930 
                   24 
               
               
                 5.5 
                 13.2 
                 0.978 
                  9760 
                 20.7 
                 0.921 
                   37 
               
               
                 6 
                 12.5 
                 0.983 
                  10170 
                 21.4 
                 0.925 
                   31 
               
               
                 6.5 
                 13.0 
                 0.979 
                  9900 
                 20.7 
                 0.930 
                   37 
               
               
                 7 
                 12.9 
                 0.980 
                  9960 
                 21.0 
                 0.928 
                   33 
               
               
                 7.5 
                 12.8 
                 0.981 
                  10040 
                 21.3 
                 0.926 
                   32 
               
               
                 Average 
                 13.4 
                 0.980 
                  9342 
                 20.6 
                 0.931 
                   46 
               
               
                 (2.5-7.5 hrs) 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 SUMMARY OF UPGRADING RESULTS (AVERAGES) 
               
             
          
           
               
                   
                   
                   
                 API 
                 Density 
                 Viscosity 
               
               
                   
                 Run # 
                 Condition 
                 Gravity 
                 g/cc 
                 mPa · s 
               
               
                   
                   
               
             
          
           
               
                   
                 Base 
                 no ISC 
                 11.0 
                 0.993 
                 100,000 
               
               
                   
                 971 
                 Dry Normal 
                 13.8 
                 0.972 
                 8,903 
               
               
                   
                 975 
                 Dry Catalytic 
                 18.7 
                 0.948 
                 101 
               
               
                   
                 972 
                 Wet Normal 
                 13.4 
                 0.980 
                 9,342 
               
               
                   
                 976 
                 Wet Catalytic 
                 20.7 
                 0.931 
                 46 
               
               
                   
                   
               
             
          
         
       
     
     Further important upgrading benefits are demonstrated in Table 7, where XT004466 is clean dry Wolf Lake crude oil which was used in the four test Runs  971 ,  972 ,  975  and  976 , and XT004467 is produced oil from the wet catalytic Run  976  of the present invention. 
     An extensive desulfurization and demetalization of the base oil was achieved in the catalytic Run  976  of the present invention. Sulfur was reduced 88% from 43,400 ppm to 5,100 ppm; nickel 96% from 73 ppm to 3 ppm and vanadium 96% from 195 ppm to 8 ppm. Other metals, such as iron and molybdenum were also partially removed in the catalytic process. It should be noted that the increase in silicon is not a consequence of the presence of catalyst: all high temperature steam processes give rise to elevated silicon levels. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 7 
               
             
             
               
                   
               
               
                 OIL SULFUR AND METAL ANALYSIS (by ICP, mg/kg) 
               
             
          
           
               
                   
                 Sample ID 
                 XT004466 (10 API) 
                 XT004467 (20.7 API) 
               
               
                   
                 Customer ref: 
                 Base Wolf Lake oil 
                 Run 976 product 
               
               
                   
                   
               
             
          
           
               
                   
                 Silver 
                 &lt;1 
                  &lt;1 
               
               
                   
                 Aluminum 
                 &lt;1 
                 &lt;1 
               
               
                   
                 Boron 
                 2 
                 3 
               
               
                   
                 Barium 
                 &lt;1 
                 &lt;1 
               
               
                   
                 Calcium 
                 2 
                 2 
               
               
                   
                 Chromium 
                 &lt;1 
                 &lt;1 
               
               
                   
                 Copper 
                 &lt;1 
                 &lt;1 
               
               
                   
                 Iron 
                 5 
                 &lt;1 
               
               
                   
                 Potassium 
                 &lt;8 
                 &lt;8 
               
               
                   
                 Magnesium 
                 1 
                 &lt;1 
               
               
                   
                 Manganese 
                 &lt;1 
                 &lt;1 
               
               
                   
                 Molybdenum 
                 7 
                 3 
               
               
                   
                 Sodium 
                 &lt;6 
                 &lt;6 
               
               
                   
                 Nickel 
                 73 
                 3 
               
               
                   
                 Phosphorus 
                 &lt;2 
                 &lt;2 
               
               
                   
                 Lead 
                 &lt;2 
                 &lt;2 
               
               
                   
                 Sulphur 
                 43400 
                 5100 
               
               
                   
                 Silicon 
                 1 
                 69 
               
               
                   
                 Tin 
                 &lt;2 
                 &lt;2 
               
               
                   
                 Titanium 
                 1 
                 &lt;1 
               
               
                   
                 Vanadium 
                 195 
                 8 
               
               
                   
                 Zinc 
                 2 
                 5 
               
               
                   
                   
               
             
          
         
       
     
     FIG. 5 shows gas chromatographic analyses of samples XT 004466 Wolf Lake crude oil and Run  976  wet catalytic ISC product. Very extensive oil upgrading is apparent from the large decrease in heavy components observed in the catalytic Run. 
     The wet combustion test of Run  976  demonstrated the preferred form of the invention. Either moderate wet combustion or superwet combustion may be applied. However, in oil reservoirs where water injectivity is too low, the catalytic dry combustion process may be applied as well. 
     Test of NCC Type Catalyst 
     Run  986  was conducted using NCC catalyst placed around the horizontal leg of the producer for the purpose of comparison with an otherwise identical non-catalytic Run  985 . 
     The original test cell was modified to have 6-band heaters and computer control to provide a better approach to adiabatic conditions. 
     The catalytic Run  986  used the catalyst FCC-RESOC-1 BU, a rare earth alumino silicate supplied by Grace Davison, and having the following physical characteristics. 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 Composition 
                 42% Al2O3, 1.0% Rare Earth oxide, 
               
               
                   
                 0.2% Na2O 
               
               
                 Surface area (square meters/gm) 
                 300 
               
               
                 Bulk density (g/ml) 
                 0.7 
               
               
                 Average particle size (microns) 
                 72 
               
               
                   
               
             
          
         
       
     
     Results showed that the Run  986  with NCC catalyst produced Wolf Lake oil (11 API) of 21.0 degrees API, which was 7 degrees API higher than the thermally cracked oil in the absence of catalyst in Run  985 . 
     The effect of vertical heterogeneity of the reservoir on fluid channeling was tested in a specially-packed cell in Run  7 . Three layers of sand were packed sequentially using fine, coarse and fine-grained sands to see whether air would advance ahead of the vertical combustion front in the high-permeability central layer. Table 8 gives the details of the stratified model. FIGS. 8 a - 8   f  shows the results in terms of thermal contours. The vertical axis represents temperature in all cases. Lowest temperatures are shown in dark color. The combustion front remained substantially vertical, with no preferred advancement into the central zone. The explanation may be that the vertical drainage of the hot cracked oil provides a “self-healing” phenomenon where air advancement into the central high permeability streak is blocked by draining oil. This demonstrates that the process of the present invention has a major advantage over processes of the prior art in which both the injected air and produced fluids flow substantially horizontally between vertical wells and fingering of air into high permeability layers causes early oxygen breakthrough and safety hazards. Layers of varying permeability are a very common feature of clastic reservoirs and often prohibits the use of traditional in situ combustion as an oil recovery process. The present invention removes this limitation. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 8 
               
             
             
               
                   
               
               
                 RUN 7 
               
               
                 DRY IN SITU COMBUSTION IN A STRATIFIED MODEL; 
               
               
                 CLAIR OIL, 19.8 API, 200 CPS AMBIENT 
               
             
          
           
               
                   
                   
                 Sand Grain 
                 Permeability 
               
               
                   
                 Layer 
                 Size 
                 MD 
               
               
                   
                   
               
             
          
           
               
                   
                 Top 
                 fine 
                 616 
               
               
                   
                 Middle 
                 coarse 
                 3000 
               
               
                   
                 Bottom 
                 fine 
                 616 
               
               
                   
                   
               
             
          
         
       
     
     In the preferred field embodiment of the invention, the direct line-drive application illustrated in FIGS. 6 and 7, a reservoir  100  is characterized by a downward dip and lateral strike. A row  101  of vertical air-water injection wells  102  is completed high in the reservoir  100  along the strike. At least two rows  103 ,  104  of production wells  105 ,  106  having generally horizontal legs  107 , are completed low in the reservoir and down dip from the injection wells, with their toes  108  closest to the injection wells  102 . The toes  108  of the row  103  of production wells  105  are spaced down dip from a vertical projection of the injection wells  102 . Catalyst particles are emplaced along the horizontal well by a well-known operation called “gravel packing”. The second row  104  of production wells  106  is spaced down dip from the first row  103 , and is similarly gravel packed. Generally, the distance between wells, within a row, is considerably lower than the distance between adjacent rows. In the first phase of the process, a generally linear combustion front is generated in the reservoir  100  by injecting air or air-water through every second well  102 . Preferably a generally linear lateral combustion front is developed by initiating combustion at every second well and advancing these fronts laterally until the other wells are intercepted by the combustion front and by keeping the horizontal production wells closed. Then, air is injected through all the wells  102  in order to link these separate fronts to form a single front. Only during this initiation phase of the field exploitation process, and only once in the lifetime of a producing reservoir, is non-upgraded oil produced. The front is then propagated by injecting air and water down dip toward the first row  103  of production wells  105 . The horizontal legs of the production wells  105  are generally perpendicular to the front. The production wells  105  are open during this step, to create a low pressure sink to induce the front to advance along their horizontal legs  107  and to provide an outlet for the heated oil. When the front approaches t he heel  109  of each production well  105 , the well is closed in. The horizontal legs  106  ( 107 ) of the closed-in wells  105  are then filled with cement. The wells  105  are then perforated high in the reservoir  100  and converted to air-water injection, thereby continuing the propagation of a combustion front toward the second row  104  of production wells  106 . Preferably, the first row  101  of injection wells is converted to water injection for scavenging heat in the burnt out zone and bringing it ahead of the combustion zone. This process is repeated as the front progresses through the various rows of production wells. By the practice of this process, a guided combustion front is caused to move through the reservoir with good volumetric sweep efficiency, and the production of upgraded oil.