Abstract:
A method and system of providing compressed low NO x  exhaust gas for industrial purposes including for use in augmenting crude oil production including the steps of extracting exhaust gas from an engine consuming a controllable mixture of hydrocarbon fuel and air, compressing and cooling the exhaust gas to condense water therefrom, measuring the pH of the condensed water, employing the measured pH to adjust the ratio of the hydrocarbon fuel and air supplied to the engine to achieve a substantially neutral pH measurement and thereby obtain compressed exhaust gas having a low NO x  content.

Description:
CROSS-REFERENCE TO PENDING APPLICATIONS 
     This is a continuation-in-part of U.S. patent application Ser. No. 10/195,604 filed Jul. 15, 2002 entitled “A Method And System For Providing Compressed Substantially NO x -Free Exhaust Gas For Industrial Purposes” which is a continuation-in-part of U.S. patent application Ser. No. 09/681,601 filed May 4, 2001 entitled “A Method And System For Providing Substantially Water-Free Exhaust Gas”, now U.S. Pat. No. 6,893,615. 
    
    
     CROSS-REFERENCE TO MICROFICHE APPENDIX 
     This application is not referenced to any microfiche appendix. 
     FIELD OF THE INVENTION 
     The present invention concerns a method of providing compressed substantially NO x -free exhaust gas for augmenting crude oil production. More specifically, the present invention is a system for providing substantially dry NO x -free exhaust gas from an engine that employs a mixture regulator to control the ratio of hydrocarbon fuel and air consumed by the engine wherein the mixture regulator is controlled in response to the pH of condensate water produced during compression of the exhaust gas. 
     BACKGROUND OF THE INVENTION 
     Most oil producing subterranean formations are characterized by pressurized gas. In some parts of the work hydrocarbon bearing formations have pressures sufficient to force liquid hydrocarbons (crude oil) to the earth&#39;s surface. In other parts of the world, the gas pressure is not sufficient to force liquid hydrocarbons to the earth&#39;s surface. However, in such formations, the presence of gas is nevertheless important since in many formations a gas drive is required to move liquid hydrocarbons from within the formation to the site of a producing well or wells. 
     As crude oil is extracted from a subterranean reservoir, the reservoir gas pressure decreases. As the gas pressure decreases, crude oil production rates usually fall. For these and other reasons, it has been found desirable in producing many subterranean formations to maintain gas pressure within the formations. 
     The characteristics of gas injected into a well can be critical. Water or free oxygen contained in gas can cause plugging of formations. Further water or free oxygen can result in bacteria growth that can plug a producing formation. 
     Ideally, gas injected into a reservoir to augment the production of liquid hydrocarbons should be water-free. Therefore, when treating gas prior to injection, a most important step is to remove substantially all water. 
     Perhaps even more important than dryness of exhaust gas to be injected into a reservoir to augment the production of hydrocarbons, it is important that the exhaust gas be as free as possible of nitrous oxide, usually referred to in the industry as “NO x ”. When nitrous oxide is present in exhaust gas it inevitably comes into contact with water which can be any water vapor that is left within the exhaust gas after efforts are made to improve the dryness of the exhaust gas as much as practically possible, or water that is encountered in subterranean hydrocarbon-producing formations. When nitrous oxide gas encounters water, nitric acid is formed. Nitric acid is exceedingly deleterious to metal and particularly to iron, that is, steel, as used in casing, tubing, pump parts and so forth. Therefore, exhaust gas used to stimulate the production of hydrocarbons should be, to the extent possible, free of NO x . 
     The present invention provides a process for generating substantially water-free and NO x  free exhaust gas that is particularly useful for injection into hydrocarbon bearing formations. 
     Examples of the use of exhaust gas from an engine for industrial purposes and examples of the use of exhaust gas to augment liquid hydrocarbon production are found in the following United States patents: 
     
       
         
               
               
               
             
           
               
                   
               
               
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                 1,868,755 
                 Mount 
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                 Process of Purifying Gases 
               
               
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                 Conlon, Jr. 
                 Method of Retuning Gas to Gas-Producing Formations 
               
               
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                 Watson 
                 Oil Recovery By Subsurface Thermal 
               
               
                   
                   
                 Processing 
               
               
                 3,000,707 
                 Barstow 
                 Process For Generating Inert Gas 
               
               
                 3,004,601 
                 Bodine 
                 Method and Apparatus for Augmenting Oil 
               
               
                   
                   
                 Recovery from Wells by Refrigeration 
               
               
                 3,100,528 
                 Plummer, et al. 
                 Method for Using Inert Gas 
               
               
                 3,137,344 
                 Wiemer 
                 Minimizing Loss of Driving Fluids in Secondary 
               
               
                   
                   
                 Recovery 
               
               
                 3,381,523 
                 Nettles 
                 Method and Apparatus for Supplying Gas Under 
               
               
                   
                   
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                 3,653,438 
                 Wagner 
                 Method of Recovery of Petroleum Deposits 
               
               
                 3,908,762 
                 Redford 
                 Method for Establishing Communication Path in 
               
               
                   
                   
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                 Including Tar Sand Deposits for Use in Oil 
               
               
                   
                   
                 Recovery Operations 
               
               
                 4,324,291 
                 Wong et al. 
                 Viscous Oil Recovery Method 
               
               
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                 Haag 
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                 Martin et al. 
                 Enhanced Oil Recovery Process 
               
               
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                 Burke 
                 Carbon Dioxide Well Injection Method 
               
               
                 4,891,939 
                 Brighenti 
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                 Storage of Combustion Products of Heat 
               
               
                   
                   
                 Engines 
               
               
                 5,232,049 
                 Christiansen, et 
                 Sequentially flooding a Subterranean 
               
               
                   
                 al. 
                 Hydrocarbon-Bearing Formation with a 
               
               
                   
                   
                 Repeating Cycle of Immiscible Displacement 
               
               
                   
                   
                 Gases 
               
               
                 5,953,907 
                 Kato et al. 
                 Method of Controlling An Engine Exhaust Gas 
               
               
                   
                   
                 System and Method of Detecting Deterioration 
               
               
                   
                   
                 Of Catalyst/Absorbing Means 
               
               
                 5,988,280 
                 Crawford et al. 
                 Use of Engine Heat in Treating a Well Bore 
               
               
                 6,039,116 
                 Stevenson et al. 
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                 Injection 
               
               
                   
               
             
          
         
       
     
     BRIEF SUMMARY OF THE INVENTION 
     This invention is a method and a system for providing substantially water-free exhaust gas useful for industrial purposes and particularly useful for injection into subterranean formations to augment the production of liquid hydrocarbons. The method includes the steps of: 1) extracting exhaust gas from hydrocarbon fuel consuming engine; 2) passing the gas from Step 1 through a catalytic converter; 3) cooling the gas from Step 2 to provide a cooled exhaust gas; 4) passing the cooled exhaust gas from Step 3 through a liquid separator by which entrained water is extracted to provide dry exhaust gas; 5) chilling the dryer exhaust gas from Step 4 to below the dew point temperature to cause water to condense out; 6) extracting the condensed water from Step 5 to provide substantially water-free exhaust gas; and 7) compressing the substantially water-free exhaust gas for industrial purposes such as for injecting into a hydrocarbon producing formation. 
     A system for practicing the method of this invention includes a hydrocarbon fuel consuming engine that produces exhaust gas. A catalytic converter is connected to receive the exhaust gas from the engine. A compressor/chiller is employed by which the exhaust gas from the catalytic converter is compressed and chilled below the dew point temperature to cause water vapor entrained therein to condense out, the condensed water being extracted to thereby provide substantially water-free exhaust gas that is compressed for injection into a subterranean formation. 
     This invention also provides a method of providing compressed substantially NO x -free exhaust gas for industrial purposes. This method includes the steps of extracting exhaust gas from an engine consuming a controllable mixture of hydrocarbon fuel and air. Water is extracted from the exhaust gas. The pH, that is negative ion concentration, of the extracted water is measured. This pH measurement is used to regulate the ratio of hydrocarbon fuel and air consumed by the engine to minimize the level of NO x  in the exhaust gas. The exhaust gas, having minimal NO x , and having passed through a sequence of compression and cooling steps in which the exhaust gas is compressed and cooled below the dew point temperature thereof to cause entrained water vapor to condense out. The extracted water vapor is separated and after measuring the pH thereof is disposed of to provide substantially dry and substantially NO x -free exhaust gas, which is then compressed so that it can be used industrially, such as for injecting into a producing oil-bearing formation. 
     A better understanding of the invention will be obtained from the following description and claims taken in conjunction with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a method and a system employing an internal combustion engine having a drive shaft connected to a multi-stage compressor. Exhaust gas from the engine is passed through a catalytic converter, cooled and then subjected to multiple steps of compression and cooling below the dew point temperature thereof. Condensed water is extracted to provide a substantially water-free exhaust gas consisting essentially of nitrogen and carbon dioxide ideally suited for compression and injection into an underground hydrocarbon producing formation. 
         FIG. 2  illustrates a method and a system employing an internal combustion engine that runs on a mixture of hydrocarbon fuel and air, the engine having a drive shaft connected to a multi-stage compressor as in  FIG. 1 . Exhaust gas from the engine is passed through a catalytic converter. An instrument is used at this point to measure the level of NO x  in the exhaust gas. Using this measurement the ratio of fuel and air consumed by the engine is regulated so that the NO x  content of the exhaust gas passing out of the catalytic converter is reduced to a minimum. This substantially NO x -free exhaust gas is then cooled and subjected to compression and chilling below the dew point temperature thereof to cause water entrained therein to condense out. The condensed water is extracted to provide a substantially NO x -free and water-free exhaust gas consisting essentially of nitrogen and carbon dioxide that is ideally suite for compression and injection into an underground hydrocarbon producing formation. 
         FIG. 3  is an illustration of a method and system employing an internal combustion engine that provides a source of exhaust gas that can be treated for use in industrial purposes.  FIG. 3  is substantially similar to the system and method illustrated in  FIG. 2  with one important difference. In  FIG. 2  the fuel/air mixture control that regulates the mixture of fuel and air that is consumed in the internal combustion engine is controlled by a NO x  analyzer whereas in  FIG. 3  a NO x  analyzer is not employed. Instead, in  FIG. 3  the fuel/air mixture is controlled in response to detected pH of water extracted from the exhaust gas. In  FIG. 3  a system is shown using a plurality of air coolers and in which a pH monitor provides a measure of pH of water from each separator. Further, a pH monitor is provided for monitoring the pH of water collected in the disposal tank that receives water from all of the separators. Obviously it is not necessary to have a plurality of pH monitors—only one is necessary.  FIG. 3  shows the various positions at which a pH monitor may be located in practicing the principals of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, and first to  FIG. 1 , a system that can be used for practicing a method of this invention is shown. The system makes use of the exhaust gas output of an internal combustion engine, the engine being indicated by the numeral  10 . Such an engine can be the kind utilized in an automobile, a truck or an industrial engine. The size of the engine will be determined by the quantity of gas required. If more gas is required than can be produced by a single engine, then multiple separate engines may be utilized. The fuel burned by engine  10  can be a hydrocarbon liquid such as gasoline, jet engine fuel, diesel fuel or so forth or the fuel may be a gas such as natural gas or gas derived from liquefied natural gas, such as propane, butane, etc. The engine  10  may be of the piston type as commonly used in automobiles and trucks or may be of the turbine type as frequently used for driving electrical generators. The engine  10  utilizes fuel mixed with ambient air that is combusted within the engine to produce energy output in the form of a rotating drive shaft  12 . As a consequence of the combustion of the fuel and air within engine  10 , exhaust gas is produced at an exhaust  14 . 
     Gas from exhaust  14  is passed through a catalytic converter  16 . In the catalytic converter, heated catalysts react with deleterious components of the exhaust gas to substantially neutralize such components to provide an output from the catalytic converter that is more environmentally acceptable. 
     The exhaust gas having passed through catalytic converter  16  is reduced to a lower temperature in an air cooler  18 . From air cooler  18 , the exhaust gas is fed into a scrubber/separator  20  in which any entrained water is separated with the water passing out through a discharge line  22  and the exhaust gas passing through a conduit  24 . Next, a refrigeration chiller  26  cools the exhaust gas below the dew point temperature thereof and additional water is extracted from it, water passing out through a water drain  28  and the cooled dry exhaust gas through a pipe  30 . A screw compressor  32  compresses the gas. As a consequence of compression, the temperature of the gas is raised. The warm gas passes by conduit  34  to the input of an air cooler  36  where the temperature of the gas is brought down. The output at  38  is then fed into the input of a multi-stage compressor  40 , driven by drive shaft  12  from engine  10 . In compressor  40 , the dry exhaust gas is passed through multiple stages of compression. In the arrangement as illustrated, compressor  40  has four stages of compression with intermediate coolers  42 ,  44  and  46 . Cooler  42  is between first compression stage one and second compression stage two; cooler  44  between compression stage two and compression stage three; and cooler  46  between compression stage three and compression stage four. Each of the coolers cools the compressed gas. The compressed gas at the output  48  of the fourth compression stage is substantially water-free and at an elevated pressure suitable to be used for industrial purposes. As previously stated, an example of an ideal use of the substantially water-free exhaust gas at output  48  is injection into a subterraneous hydrocarbon producing formation to maintain the pressure of the formation to thereby augment the production of liquefied petroleum. 
     Representative temperatures of the gas at various stages are indicated in  FIG. 1 . The gas at exhaust  14  of engine  10  is typically about 850° F. and is typically raised to about 1100° F. in catalytic converter  16 . Air cooler  18  preferably reduces the temperature to about 115° F. The temperature of the gas passing out of scrubber/separator  20  is also preferably about 115° F. The temperature of the gas from refrigeration chiller/separator  26  is reduced to near the freezing point—that is, about 32° F. however the gas coming out of compressor  32  is typically about 200° F. This is reduced by air cooler  36  to about 115° F. and each of air coolers  42 ,  44  and  46  are designed and operated so that the exhaust gas emerging therefrom is at about 115° F. These temperatures are not critical. 
     Water that is extracted from the exhaust gas must be properly disposed of, therefore discharge line  22  from scrubber/separator  20  and drain  28  from refrigeration chiller/separator  26  are fed to a water disposal site  50 . The water from disposal  50  can be injected separately into a non-producing subterranean formation or otherwise disposed of in a proper, environmentally acceptable manner. 
     The substantially water-free exhaust gas produced by the system and method of this invention, as illustrated in  FIG. 1 , is composed of about 85% nitrogen and 15% carbon dioxide. Thus the system, when used to provide gas that is injected back into a subterranean formation also reduces the amount of carbon dioxide that would otherwise pass into the atmosphere. 
       FIG. 2  shows an alternate and improved embodiment of the invention. In the system of  FIG. 2 , all of the essential components of the system of  FIG. 1  are employed as illustrating one example of a way of practicing the invention. Engine  10  is shown having a carburetion system  52  as is required on all internal combustion engines. The carburetion system  52  may be carburetor of the well-known type that draws liquid fuel in response to the passage of air through the carburetor and in which a mixture of atomized liquid fuel and air passes into an intake manifold. On the other hand, the carburetion system  52  may be of the fuel injection type that is currently employed on most automobile and truck engines or the type injection system long employed with diesel engines. In addition, the carburetion system  52  can be of the type that employs the use of natural gas in which natural gas is combined with air to produce the combustion mixture that is consumed by the engine. 
     The carburetion system  52  includes the use of a mixture regulator  54  that controls fuel and air input. The mixture regulator  54  is representative of a system that may be integral with carburetor system  52  that permits regulation of the ratio of fuel and air that is employed by engine  10  according to changing conditions and circumstances. Mixture regulator  54  is controlled or operated by a fuel/air mixture control  56  which in turn is governed by the output of a NO x  analyzer  58 . 
     NO x  analyzer  58  is an instrument that is commercially available. It samples the output of catalytic converter  16  to determine the quantity of NO x  in the stream that passes on to air cooler  18  and then to a scrubber/separator  20  and so forth, to the end of the system that ultimately produces the processed gas at outlet  48 . 
     NO x  analyzer  58  detects the presence of and amount of nitrous oxide in the exhaust gas appearing at engine exhaust  14 . As previously explained, NO x  is a very deleterious component of exhaust gas used for industrial purposes since it reacts with water to form nitric acid and as also previously explained, nitric acid is highly reactive with metal and therefore, attacks piping systems, valves, pumps, etc. This is particularly true when exhaust gas is utilized for injecting into wells. While the exhaust gas produced by the system of this invention is substantially water-free, as previously explained, particularly with reference to  FIG. 1 , nevertheless, many applications of exhaust gas take place where water is inevitably present. This is particularly true when exhaust gas is used for pressurizing a subterranean hydrocarbon-bearing formation since substantially all formations that include hydrocarbon, either crude oil or gas, include some water. 
     In any event, the system of  FIG. 2  is intended to substantially reduce nitrous oxide in the exhaust gas. This is accomplished by the use of the NO x  analyzer  58  that detects the presence of NO x  in the exhaust gas. The signal from the analyzer  56  is applied to fuel/air mixture control  56  that controls mixture regulator  54  to regulate the ratio of fuel and air that is injected into carburetion system  52  of engine  10 . The fuel/air ratio is usually referred to as the “fuel mixture”. It has been discovered that by regulating the fuel mixture, the quantity of nitrous oxide produced in the exhaust gas can be controlled. By adjusting the fuel/air ratio, or fuel/air mixture, engine  10  can be operated such that NO x  appearing at exhaust  14  and ultimately at the output of catalytic converter  16  is minimized. In this way, the dry and substantially water-free exhaust gas that appears as processed gas at outlet  48  is substantially free of NO x . Thus, the objective of the system of  FIG. 2  is to provide dry (essentially water-free) and substantially NO x -free gas that can be used for industrial purposes, including, as an example, injecting into a hydrocarbon-bearing formation to augment the production of hydrocarbons. 
       FIG. 3  shows a different and improved system for obtaining exhaust gas for use in augmenting crude oil production. In this system the fuel/air mixture control  56  is operated in response to the detected pH of water condensed from the exhaust gas stream. In  FIG. 3 , six scrubber/separators are illustrated, that is, elements  20 ,  26 ,  60 ,  62 ,  64  and  66 . Each of these has a pipe to drain water that is separated by the scrubber/separator. The drain pipes are indicated by numerals  22 ,  28 ,  68 ,  70 ,  72  and  74 . Each of these drain pipes connects water that is condensed out of the exhaust gas to disposal  50 . A pH monitor can be positioned in any one of these drain pipe locations to detect the pH of water condensed out of the exhaust gas. The detected pH is used to actuated the fuel/air mixture control  56 . Specifically, to measure the pH in water in drain pipe  22  separated by scrubber/separator  20  a pH monitor  76  is employed. In like manner, a monitor  78  is connected to detect the pH of water in drain pipe  28 ; monitor  80  detects the pH of water in drain pipe  68 ; monitor  82  detects the pH in drain pipe  70 ; monitor  84  detects the pH of water in drain pipe  72  and monitor  86  detects the pH of the water in drain pipe  74 . In addition, a pH monitor  88  can be provided to detect the condensate water collected in disposal  50 . The pH monitor  88  may have a probe  90  that extends into the collected water. 
     By means of electrical signals generated from any one of the pH monitors  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88 , an electrical signal can be sent by way of electrical conductors  92  to the fuel/air mixture control  56  to regulate the ratio of fuel in the air employed by internal combustion engine  10 . 
     It has been discovered that when the fuel/air mixture supplied to engine  10  is controlled in a way so that the water condensed from the exhaust gas has a neutral pH then the NO x  contents of the engine exhaust gas is at a minimum. Thus the process gas appearing at  48  will be substantially water and NO x -free. 
     A single pH meter monitor is all that is required to practice the invention and it can be located at any one of the positions of pH monitors  76 ,  78 ,  80 ,  82 ,  84 ,  86  and  88 . In addition, a combination of two or more of the pH monitors may be employed to provide the control signal to fuel/air mixture control  56 . 
     The claims and the specification describe the invention presented and the terms that are employed in the claims draw their meaning from the use of such terms in the specification. The same terms employed in the prior art may be broader in meaning than specifically employed herein. Whenever there is a question between the broader definition of such terms used in the prior art and the more specific use of the terms herein, the more specific meaning is meant. 
     While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is to be limited only by the scope of the attached claims, including the full range of equivalency to which each element thereof is entitled.