Abstract:
A method for the integrated production and utilization of synthesis gas for production of mixed alcohols, for hydrocarbon recovery, and for gasoline/diesel refinery, has the following steps: forming a hydrocarbon fuel including coal and/or gas oil; gasifying the hydrocarbon fuel to form synthesis gas that includes hydrogen and carbon monoxide; directing the carbon monoxide and a stoichiometric amount of the hydrogen to an alcohol synthesis unit for the synthesis of mixed alcohols; combusting the remaining hydrogen with oxygen via a downhole gas combustion unit; and adding the water to the combustion to produce high-pressure steam for the recovery of crude oil from the hydrocarbon bearing formation.

Description:
CROSS-REFERENCE TO RELATE APPLICATIONS 
       [0001]    This application for a utility patent claims the benefit of U.S. Provisional Application No. 61/161,503, filed Mar. 19, 2009. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    This invention relates generally to methods of producing gasoline and related fuels, and more particularly to a method for the integrated production and utilization of synthesis gas for production of mixed alcohols, for hydrocarbon recovery, and for gasoline/diesel refinery. 
         [0005]    2. Description of Related Art 
         [0006]    Vinegar et al., U.S. Pat. No. 7,461,691 (Shell Oil), teaches an in situ hydrocarbon recovery system that utilizes a wide variety of heating systems to heat hydrocarbons for enhanced recovery. The reference discusses in great length the gasification of hydrocarbons (including lignite coal) for the production of synthesis gases. This reference teaches the use of the hydrogen for hydrogenation of the oil formation for enhanced recovery. It also discusses the use of hydrogen as a fuel for combustion and for making steam, but particularly for electricity generation. Also, it teaches the use of the hydrogen for use as a feedstock for a Fischer-Tropsch process. 
         [0007]    The production of hydrogen from a reformer process, from hydrocarbons such as oil and coal, is also taught in various other references, such as Stine, U.S. Pat. No. 4,448,251. Stine specifically discusses producing hydrogen from the hydrocarbon formation for use in extracting oil from that formation; however, the hydrogen is used for hydrogenation, not fuel in an in situ combustion system. 
         [0008]    Gregoli et al., U.S. Pat. No. 6,016,867 (and other related patents to World Energy Systems, Inc.), teaches a downhole combustion unit that burns hydrogen and oxygen with steam for in situ hydrovisbreaking This reference specifically discusses the production of the necessary hydrogen from hydrocarbons recovered from the site. Related references include Hamrick, U.S. Pat. Nos. 4,078,613, and 3,982,591. 
         [0009]    DeFrancesco, U.S. 2008/0257543 (application published Oct. 23, 2008), teaches an enhanced hydrocarbon recovery process that includes burning a hydrocarbon rich fuel with O2 to form a hot CO2 and steam mixture that is then injected into a reservoir of heavy oil/bitumen. The produced hydrogen may be used to fuel a turbine, or for hydrogenation of bitumen. 
         [0010]    Clark, U.S. Pat. No. 4,458,756, teaches the wet oxidation of coal slurry, in situ, for producing steam and carbon dioxide for force heavy oil from a formation. 
         [0011]    Rose et al., U.S. Pat. No. 4,159,743, teaches a process for recovering hydrocarbons that includes burning methane in a combustion unit in situ. The methane produces CO2 and H2, and water may be added to produce steam. In one embodiment, O2 is added to also combust the H2 for increased temperature. 
         [0012]    Other references of interest include Gondouin, U.S. Pat. No. 4,706,751, Steinberg, U.S. 2006/0219403 (application), and Shirley, U.S. Pat. No. 5,332,036. All of the above-described references are hereby incorporated by reference in full. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention teaches certain benefits in construction and use which give rise to the objectives described below. 
         [0014]    The present invention provides a method for the integrated production and utilization of synthesis gas for production of mixed alcohols, for hydrocarbon recovery, and for gasoline/diesel refinery. The method comprises the steps of forming a hydrocarbon fuel including coal and/or gas oil; gasifying the hydrocarbon fuel to form synthesis gas that includes hydrogen and carbon monoxide; directing the carbon monoxide and a stoichiometric amount of the hydrogen to an alcohol synthesis unit for the synthesis of mixed alcohols; directing remaining hydrogen to the downhole gas combustion unit positioned underground within a hydrocarbon bearing formation; directing oxygen to the downhole gas combustion unit; combusting the remaining hydrogen with the oxygen via the downhole gas combustion unit; and adding water to the combustion to produce high-pressure steam for the recovery of crude oil from the hydrocarbon bearing formation. 
         [0015]    A primary objective of the present invention is to provide a method for the integrated production and utilization of synthesis gas for production of mixed alcohols, for hydrocarbon recovery, and for gasoline/diesel refinery, the method having advantages not taught by the prior art. 
         [0016]    Another objective is to provide a method for using lignite coal and/or gas oil and/or other undesirable carbon sources as feedstocks for syngas production. 
         [0017]    A further objective is to provide a method for utilizing syngas for the production of both low octane gasoline and mixed alcohols which can then be blended together to form an optimal high octane gasoline that is ready for sale and utilization. 
         [0018]    A further objective is to provide an integrated process for the production of high octane gasoline that provides optimal efficiency and limited waste and/or environmental impact. 
         [0019]    Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The accompanying drawings illustrate the present invention. In such drawings: 
           [0021]      FIG. 1  is a flow diagram of one embodiment of a synthesis gas generation process to produce mixed alcohols; 
           [0022]      FIG. 2  is a flow diagram of one embodiment of a synthesis gas utilization process wherein synthesis gas generated in the generation process of  FIG. 1  is utilized to recover hydrocarbons from a hydrocarbon bearing formation via a recovery well; and 
           [0023]      FIG. 3  is a flow diagram illustrating one method of processing crude oil recovered from the recovery well of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    The above-described drawing figures illustrate the invention, a method for the integrated production and utilization of synthesis gas for production of mixed alcohols, for hydrocarbon recovery, and for gas/diesel refinery. 
         [0025]      FIG. 1  is a flow diagram of one embodiment of a synthesis gas generation process  10  utilized for generating a synthesis gas  30  for use in the production of mixed alcohols, and for hydrocarbon recovery (as described in greater detail below, and illustrated in  FIG. 2 ). 
         [0026]    As illustrated in  FIG. 1 , the synthesis gas generation process  10  includes a lignite preparation unit  20  in which lignite coal is prepared for gasification. The lignite preparation unit  20  processes the coal to form the hydrocarbon fuel  22  that is sent to a lignite gasifier  24 . The hydrocarbon fuel  22  may include crushed coal, and may further include gas oil  23  generated in later stages of the process. The hydrocarbon fuel  22  may be processed to a dry and powdered form; however, in alternative embodiments it may be mixed with water to form a lignite slurry. In addition to lignite coal, other syngas feedstocks may also be used (e.g., hydrocarbons, biomass, or other carbohydrates synthesized to hydrogen/carbon). 
         [0027]    The hydrocarbon fuel  22  is transported to the lignite gasifier  24 , so that it may be converted to synthesis gasses (e.g., hydrogen, carbon dioxide, carbon monoxide). An air separation plant  26 , or suitable process, separates oxygen  28  from ambient air, and the oxygen  28  is transported for use in the lignite gasifier  24 . Since the construction of the air separation plant  26  is well known in the art, it is not discussed in greater detail herein. 
         [0028]    The lignite gasifier  24  produces synthesis gas  30  using techniques known in the art. For example, the lignite gasifier  24  meters high temperature combustion to produce the synthesis gas  30 . The synthesis gas  30  includes hydrogen (H2), carbon monoxide (CO), and carbon dioxide (CO2). Typical lignite coal, although considered low-quality coal, produces a large amount of hydrogen. Furthermore, a water gas shift reactor  29  may be utilized to increase the proportion of hydrogen produced. 
         [0029]    In the preferred embodiment, the lignite gasifier  24  is a small, skid-mounted, modular, and portable construction. While prior art devices are adapted for generating electricity, and are therefore very large and expensive, the current plant is many times smaller and easily portable. 
         [0030]    The synthesis gas  30  is then transported to a synthesis gas separation unit  32  for separation of the various components of the synthesis gas  30 . Some components and/or contaminants, such as sulfur  33  and carbon dioxide  40  are removed. Some of these components and/or contaminants may be utilized in a productive manner (e.g., the sulfur  33  may be used in the production of sulfuric acid  34 ). The carbon dioxide  40  may be removed by an amine tower, pressure reduction, or any other technique known to those skilled in the art. The carbon dioxide  40  may be directed to a CO2 storage  41  such as may be devised by those skilled in the art. Different techniques of CO2 sequestration known in the art may be utilized, and/or the carbon dioxide  40  may be used in hydrocarbon recovery efforts using techniques known in the art. The carbon dioxide  40  may also simply be stored and sold to those requiring carbon dioxide. 
         [0031]    The carbon monoxide  36  and the hydrogen  38  are then transported for further use. The carbon monoxide  36  and a stoichiometrically correct portion of the hydrogen  38  may be transported to an alcohol synthesis unit  42  for use in the synthesis of an alcohol mixture  44 , as described in greater detail below. The remainder of the hydrogen  38  is transported to the hydrocarbon recovery process  50 , illustrated in  FIG. 2 , for use in enhancing recovery of crude oil. The portion of the hydrogen  38  used in the hydrocarbon recovery process  50  may be separated from the rest using pressure swing absorption, ceramic filtering, or any other process or method known in the art. 
         [0032]    The carbon monoxide  36  and the hydrogen  38  transported to the alcohol synthesis unit  42  are used for the production of the alcohol mixture  44 . In one embodiment, the alcohol synthesis unit  42  utilizes a copper catalyst to produce methanol and higher aliphatic alcohols. In one embodiment, the mixed alcohols include C1-C8 alcohols. The C1-C8 alcohols may include a greater amount of methanol than ethanol, and in one embodiment the majority of the mixed alcohols is methanol. 
         [0033]    In one embodiment, a fixed bed copper catalyst is used to produce the alcohols, using a process disclosed in Schneider et al., U.S. Pat. No. 4,598,061, which is hereby incorporated by reference in full. In this embodiment, the catalyst includes, as an oxide precursor, copper oxide and zinc oxide, which is transformed into a catalytically active state by reduction with hydrogen. Aluminum oxide may be used as a thermostabilizing substance, and it further includes at least one alkali carbonate or alkali oxide. In other embodiments, a copper catalyst in a liquid bed is used in a process developed by Eastman Kodak, Inc. Other alternative methods may also be used to produce other fuels (e.g., Fischer-Tropsch, and other alternative processes), and such alternatives should be considered within the scope of the present invention. 
         [0034]    In one embodiment, the synthesis gas generation process  10  further includes a stabilization unit  46  that captures un-reacted synthesis gas components back to the alcohol synthesis unit  42 . The stabilization unit  46  may perform this process using techniques that are known in the art, to increase the efficiency of the process and increase the yield of the alcohol synthesis unit  42 . 
         [0035]    In one embodiment, the lignite gasifier  24  and related components are all located at an oilfield and the coal utilized is transported to the oilfield for use. This arrangement is useful because gas oil may be added to the coal to increase production of the synthesis gas  30 , as described in greater detail below. In another embodiment, the lignite gasifier  24  may be located adjacent a source of coal (e.g., a coal mine), and the hydrogen  38  may be piped or otherwise transported to the oilfield for use in the oil recovery processes. 
         [0036]      FIG. 2  is a flow diagram of one embodiment of the hydrocarbon recovery process  50 , wherein the synthesis gas  30  generated in the synthesis gas generation process  10  of  FIG. 1  is utilized to recover hydrocarbons from a hydrocarbon bearing formation  58 . As illustrated in  FIG. 2 , the hydrogen  38  is used to fuel a gas combustion unit  52  which is located downhole  54  adjacent the hydrocarbon bearing formation  58  (beneath an overburden  56 ). The gas combustion unit  52 , described in greater detail below, is used to generate sufficient heat and pressure to drive hydrocarbons from the hydrocarbon bearing formation  58  to a recovery well  60 . 
         [0037]    The gas combustion unit  52  also utilizes the hydrogen  38 , along with oxygen  64  and water, to generate super-heated steam to drive oil recovery. An air separation plant  62  removes the oxygen  64  from ambient air, and the oxygen  62  along with water from a water source  66  are transported to the gas combustion unit  52 , along with the hydrogen  38 . The gas combustion unit  52  may be similar to the gas combustion unit disclosed in Hamrick et al., U.S. Pat. No. 3,982,591, which is hereby incorporated by reference in full. The gas combustion unit  52  burns the hydrogen  38  and the oxygen  64  at an extremely high temperature, and the water is used to cool the combustion zone, thereby creating large quantities of high-pressure steam. 
         [0038]    In one embodiment that is not illustrated, the carbon dioxide  40  may also be pumped into the hydrocarbon bearing formation  58 . Not only does this sequester the carbon dioxide  40  and remove it from the atmosphere, the carbon dioxide  40  also increases the production of the hydrocarbons. Since the carbon dioxide  40 , which is the only waste, may be sequestered in the hydrocarbon bearing formation  58 , the present process produces little to no pollution to the surrounding ecosystem. The negligible environmental impact, and its carbon neutrality, makes this process particularly attractive. 
         [0039]    The high-pressure steam, which is relatively pure and free of contamination, is a preferred method of light-oil steam-flooding to recover residual oil from water flooded light oil reservoirs. The high pressure and heat (typically around 650 degrees F., 3,000 psi, although the specifics will depend upon the depth, and other characteristics of the formation) of the steam produced using the current method are particularly effective at driving the hydrocarbons to the recovery well  60 , utilizing both distillation and re-pressurization. This process is notably more effective than processes used in the current state-of-the-art, wherein steam is produced by burning hydrocarbons, and which operate at much lower temperatures and pressures. 
         [0040]    It is also worth noting that the gas combustion unit  52  may be readily modified to lower or higher temperatures, and/or pressures, depending upon the characteristics of a given reservoir. 
         [0041]    While the above-described hydrocarbon recovery process  50  is particularly well-suited for the recovery of oil from water flooded light oil reservoirs, it may also be utilized in the recovery of heavy oils, and other hydrocarbon sources. The gas combustion unit  52  produces extremely high heat and pressure, which may be used to recover heavy oils using techniques well-known in the art. It is also possible to add additional hydrogen for the hydrogenation of the hydrocarbon bearing formation  58 , using techniques well-known in the art. The gas combustion unit  52 , or “downhole rocket,” can be utilized in many ways for the recovery of hydrocarbon sources because of its extremely high heat, high pressure, and massive production of extremely high quality steam. The downhole rocket  52  may include a restricted orifice, such as is disclosed in Hamrick. 
         [0042]      FIG. 3  is a flow diagram illustrating one method of processing crude oil recovered from the recovery well of  FIG. 2 . As illustrated in  FIG. 3 , the crude oil  70  recovered via the recovery well  60  (of  FIG. 2 ) is refined via steam distillation  73  to provide heavier gas oil  74  as well as lighter gasoline, typically a low octane gasoline  76  having an octane of approximately 80-85. For purposes of this application, the term “steam distillation” is hereby defined to include other suitable forms of distillation that are suitable for the present process. For purposes of this application, the term “gasoline” is defined to include similar and/or equivalent fuels, such as diesel, which may also be used to fuel engines, and which may be blended with varying amounts of the mixed alcohols  44 . 
         [0043]    The gas oil  74  is then used as a feedstock to the lignite preparation unit  20 , as described above. The low octane gasoline  76  may be blended with the mixed alcohols  44 , whose production is described above, to form high octane gasoline  78 . Likewise, diesel may be blended in a similar manner. 
         [0044]    In this manner, lignite coal and similar undesirable carbon sources, and also including gas oil  74  that is readily available at the site of production, are utilized as valuable feedstocks for syngas production, which is then utilized for the production of both low octane gasoline  76  and mixed alcohols  44  which can then be blended together to form an optimal high octane gasoline  78  that is ready for sale and utilization. The integrated nature of the production provides optimal efficiency and limited waste and/or environmental impact. 
         [0045]    As used in this application, the words “a,” “an,” and “one” are defined to include one or more of the referenced item unless specifically stated otherwise. Also, the terms “have,” “include,” “contain,” and similar terms are defined to mean “comprising” unless specifically stated otherwise. Furthermore, the terminology used in the specification provided above is hereby defined to include similar and/or equivalent terms, and/or alternative embodiments that would be considered obvious to one skilled in the art given the teachings of the present patent application.