Abstract:
A method and apparatus for the decomposition of hydrogen peroxide, particularly for use as a hydrocarbon well bore and pipeline cleaning and maintenance aid. The apparatus includes a decomposition engine having an inlet manifold extending centrally within the housing and having means for passage of hydrogen peroxide through the manifold wall through a catalyst stack. The decomposition products produced are directed through an exit venturi. The decomposition products are passed through a piping system which allow the selective venting or introduction of the products into a facility to be cleared. Control means are coupled to the engine and valving to allow for the selective adjustment of temperature and or pressure of the decomposition products, as well as the introduction and diversion of the blend into the facility.

Description:
[0001]    The present application claims the priority of Provisional Application 60/841,417 filed Aug. 31, 2006. 
     
       [0002]    The present invention relates to a new and improved apparatus and method for decomposing hydrogen peroxide, particularly for use as a hydrocarbon well bore and pipeline cleaning and maintenance aid. 
       BACKGROUND OF THE INVENTION  
       [0003]    As oil and gas wells age their production often decreases. While a portion of such diminution is the obvious result of depletion of the hydrocarbon reservoir which is being tapped, the decrease of flow is often the result of the collection of higher weight hydrocarbons, such as paraffins in and near the bore hole and in the fractured hydrocarbon-bearing ground formation, which inhibit the hydrocarbon flow. In addition, the introduction of chemicals into the borehole for a variety of desired effects can, over the long term, cause flow blockage. In a similar manner, hydrocarbon pipelines may collect deposits which, over the long term, diminish the effective inner diameter of the pipe and thus limit its flow capacity. 
         [0004]    A variety of techniques are known and have been applied to remediate such blockage conditions. These techniques include mechanical procedures, such as scraping, the introduction of further chemical treatments to react with and dissolve blockages, as well as, more recently, the application of sonic energy to attack the blockages. Each of such techniques have their advantages and disadvantages. 
         [0005]    It is known to utilize hydrogen peroxide (H 2 O 2 ) as a stimulation vehicle. As an active oxidizer, the direct injection of hydrogen peroxide into a well serves as a chemical reactant. Because of its high reactivity, however, the injection of hydrogen peroxide into a well is fraught with difficulties and potential hazards. In addition, ever-tightening environmental standards preventing the discharge of hazardous materials into the environment further mitigate against the direct injection of hydrogen peroxide. 
         [0006]    It is also known to use hydrogen peroxide as a decomposition agent. The decomposition products of hydrogen peroxide are water and oxygen. The decomposition of hydrogen peroxide by use of an appropriate catalyst generates a high temperature mixture of oxygen and water in the form of water vapor or steam, and the injection of such a mixture into a well has found some measure of commercial value. As decomposition products, both oxygen and water can be vented to the environment without the environmental risk or harm associated with other agents. 
         [0007]    U.S. Pat. No. 3,235,006 to Hujsak discloses the direction of hydrogen peroxide into a well pipe. A catalyst is located within the well at the lower end of the pipe. Upon contact with the catalyst the injected peroxide decomposes, the decomposition products performing a stimulation treatment. Such methodology requires care to keep the peroxide free of potential reactants as it is delivered down the piping. The decomposition reaction is also difficult to monitor and is uncontrolled. U.S. Pat. No. 4,475,596 to Papst utilizes a similar system in which a decomposition reaction is initiated within the borehole at or above the level of the formation to be treated. 
         [0008]    U.S. Pat. No. 4,967,840 of Nov. 6, 1990 to Miller discloses an apparatus for decomposing hydrogen peroxide especially for use as a flow stimulation media for hydrocarbon-bearing formations and discloses a basic system and method for its use in association therewith, in which the decomposition is performed outside the well, and the reaction products directed into the well. As the introduction of any stimulation product into a hydrocarbon well must be carefully controlled and monitored, however, the &#39;840 patent is deficient in that it neither provides an apparatus for efficient control or generation of the decomposition products, nor allows supervision or control over the metering of the decomposition products into a well or other facility. 
         [0009]    It is accordingly a purpose of the present invention to provide a method and apparatus for performing a decomposition reaction for hydrogen peroxide outside a well or other structure to which the decomposition products are to be introduced and utilizing the decomposition products in connection with well stimulation and pipeline cleaning. 
         [0010]    A further purpose of the present invention is to provide such an apparatus which allows the decomposition reaction to be controlled, monitored and adjusted in an efficient and ongoing manner. 
       BRIEF DESCRIPTION OF THE INVENTION  
       [0011]    In accordance with the foregoing and other objects and purposes, the present invention comprises a hydrogen peroxide decomposition engine with a decomposition chamber having a central pathway into which concentrated hydrogen peroxide is introduced, a catalyst shell through which the hydrogen peroxide passes and is converted into its decomposition products, and an exit venturi for controlling the flow of the hot, high-pressure, decomposition products. The control system of the present invention comprises a series of valves and pumps for the hydrogen peroxide as well as air, water and actional chemicals that may be added to the injected steam/oxygen mixture as well as valve and pump control means. Gauges and control means are preferably arrayed on a master control panel, the main control means for delivery of the hydrogen peroxide into the decomposition element being an electro-hydraulic joystick coupled to a pump for the peroxide. The decomposition products are thus monitored and metered into the well or other targeted structure in an efficient, safe and controlled manner. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0012]    A fuller understanding of the present invention will be achieved with consideration of the annexed drawings, wherein: 
           [0013]      FIG. 1  is a cross-sectional view of a hydrogen peroxide decomposition engine in accordance with the invention; 
           [0014]      FIG. 2  is an elevation view of the inlet port assembly thereof; 
           [0015]      FIG. 3  is a plan view of the bottom outlet plate thereof; 
           [0016]      FIG. 4  is a plan view of a catalyst element thereof; 
           [0017]      FIG. 5  is a diagrammatic representation of a system for injecting the hydrogen peroxide decomposition products into a well utilizing the inventive engine and control system; 
           [0018]      FIG. 6  is a diagrammatic representation of the supply piping for the configuration depicted in  FIG. 5 ; and 
           [0019]      FIG. 7  is an illustration of a control panel for the control system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    With initial reference to  FIGS. 1-4 , hydrogen peroxide decomposition engine  10  comprises a generally cylindrical housing  12 , which may be on the scale of approximately  2  feet long. The housing is formed with a generally cylindrical central bore  14  which carries the decomposition reactor, as described infra. The central bore  14  terminates at its rear end in a converging/diverging venturi  17  formed in the housing through which the decomposition products exit the engine. As further depicted in  FIGS. 1 and 2 , the inlet side of the catalyst engine  10  has top plate  16  which is bolted to the top of the housing  12  through aligned bolt holes  19  and to which central perforated cylinder  18  is mounted, such as by welding. A sealing ring  21  is mounted in aligned circumferential notches in the top of the housing and on the bottom of the top plate to seal the top plate to the housing. The ring  21  may be of copper or other appropriate material to withstand the high temperature of the engine when in operation. Concentrated hydrogen peroxide is introduced through the top plate  16  and into the center of cylinder  18  through entranceway  20  in top plate  16 . The bottom end  22  of cylinder  18  is also perforated, whereby the introduced hydrogen peroxide flows outwardly through the perforations in the cylinder sidewall and bottom end. 
         [0021]    Surrounding the cylinder  18  within the engine&#39;s central bore  14  are a series of stacked catalyst elements  24 . As seen in  FIG. 4 , each of the catalyst elements  24  is preferably ring-shaped, and are thus stackable within the central bore  14 , fitting between the housing wall and the perforated cylinder  18 . As known in the art, the catalyst elements  24  may be formed of a porous silver mesh, the contact of concentrated hydrogen peroxide with the silver resulting in immediate decomposition of the hydrogen peroxide in an exothermic reaction to gaseous oxygen and water in the form of water vapor or steam. A catalyst disc  24 A, as shown in  FIG. 1 , against which the bottom of the cylinder  18  contacts, provides the catalyst bed for the peroxide exiting through the perforated cylinder bottom  22 . 
         [0022]    Located at the bottom end of the central bore  14  is perforated bottom plate  26  further depicted in  FIG. 3 . Plate  26  supports the catalyst element stack, and also provides for an exit way for the decomposition products from the stack. The parallel bores through the bottom plate eject the decomposition products generally downward, along the major axis of the engine, into the tapering portion of venturi  17 , which increases the velocity and lowers the pressure of the decomposition products as they are exhausted from the engine. 
         [0023]    As depicted in  FIG. 5 , the exit venturi of catalyst engine  10  is coupled to main delivery line  30  which delivers the decomposition products through knockoff coupler  32  to a well or other facility as appropriate. A temperature sensor, such as thermocouple  34 , is positioned at the exit of the engine to monitor the exhaust temperature. Delivery lines  36  and  38 , for water and air respectively, are connected to the main delivery line. A second temperature sensor  40  and a pressure sensor  42  are located in the delivery line  30  downstream of the air and water inlets, while a pair of electro-pneumatically activated (EPA) valves  44  and  46  are provided for pressure buildup and venting purposes. Valves  48 ,  50  and  52  control the admission of peroxide, air and water, respectively into the system as depicted. 
         [0024]    The valves  48 ,  50  and  52  are on the output lines from supply system  69 , depicted in  FIG. 6 . As depicted therein, system peroxide, air and water are stored in respective tanks  54 ,  56  and  58 . In addition, a tank  70  may be provided for auxiliary chemicals desired to be injected into the well bed. The peroxide line is provided with pump  60 , while the water line is provided with low pressure pumps  64 A, B and C and high pressure pumps  66 A, and B. The low and high pressure water pumps  64 A-C and  66 A, B may each be a tandem assembly of multiple pumps to insure continuity of operation. The high pressure pumps  66 A, B are blending pumps, allowing the chemicals in tank  70  to be combined with water as may be appropriate for well introduction. The system further includes appropriate piping and valving to allow pressurized air from tank  56  as well as water from tank  58  to be introduced to various lines for purging purposes as may be required. The valves themselves may be pneumatically operated, and the operating air line system for the valves is shown in dotted. The interconnections between the valves and the controllers therefor are conventional and are not otherwise shown. Disconnect fittings  71  may be utilized as appropriate to facilitate system interconnection and disassembly. 
         [0025]      FIG. 7  depicts a control panel for the operating system for the engine and piping system depicted in  FIGS. 5 and 6 . The control panel may be embodied in a free-standing cabinet-like structure, or may be located in a trailer or other appropriate housing near the well or other facility to be treated and is connected to a suitable source of power and to the sensors, valves and the like for the system in a conventional manner. As may be seen, it includes a series of valve operators, represented by the ovanls, corresponding to and for controlling the valves depicted in  FIG. 6 , along with gauges “G”  35 ,  43 , and  45  for displaying the temperature and injection pressure monitored by the sensors  34 ,  40  and  42  as well as gauge  37  for monitoring the water pressure injected through line  36  and gauge  41  for monitoring the pressure at peroxide pump  60 . Full operating status data of the decomposition engine and well injection components is continuously available to the system operator. 
         [0026]    Electro-hydraulic joystick  62  is the operator control element for the peroxide pump  60  and proportionally controls the operation of the pump through an electro-hydraulic valve-controlled hydraulic motor  63 . The output flow and pressure of H 2 O 2  pump  60  is proportional to the setting of joystick  62 , allowing continued and precise metering of the peroxide into the engine. At the same time, control over the other valves, and particularly the valve in water line  36 , allows precise control over the temperature and pressure of the oxygen/water vapor mixture being injected into the well. As may be seen in  FIG. 5 , water from line  36  may be mixed with the decomposition products exiting from the engine. The high temperature steam-oxygen output of the catalyst engine  10  may be of too great a temperature for well introduction. The mixing of its decomposition products with additional water in delivery line  30  allows both the lowering of the blend temperature as a result of the heat of vaporization energy needed to convert the added water to steam, while also having pressure effects resulting from the further generation of gaseous water. By appropriate operation of the system both the temperature and pressure of the injected oxygen/steam blend can be precisely controlled. 
       EXAMPLE  
       [0027]    The following is a further explanation of a typical control sequence for the operation of the peroxide decomposition and injection system of the invention incorporating the elements of the control panel of  FIG. 7 . 
       1) Initial Activation 
       [0028]    In an initial step the system is powered up. As the system will be used at an oilfield that may be without a source of electric power, a self-contained electrical power source, typically a generator (not shown), is powered up. A skid-mounted compressor (not shown) is actuated and brought up to operating pressure, typically 120 PSI, to provide compressed air for storage in air tank  56 , and a hydraulic gas drive engine (also not shown) connected to a hydraulic motor (not shown) is turned on to provide hydraulic line pressure for the pumps. Control panel master switch  75  is turned on, and a visual check is performed to confirm that that all gauges appear to be functioning properly. 
       2) H 2 O Low Pressure Pumps Check 
       [0029]    Low PSI H 2 O delivery line  73  is drained to scavenge any water in the line. With main water valve  59  open, low PSI H 2 O EPA delivery valve  52  is opened, and each low PSI H 2 O pump  64 A, B and C is activated individually to make sure that each pump is functioning correctly. Once the check is completed, valve  52  is closed. The first low PSI H 2 O pump ( 64 A) is then activated and remains on until the well stimulation procedure is completed. If there is a pump failure, one of the parallel backup pumps,  64 B or C, can be activated. Once a pump  64  is operating, low PSI H 2 O EPA delivery valve  52  may be opened at any time to retrieve low-pressure water. 
       3) Catalyst Engine Start Up 
       [0030]    The speed of the hydraulic system&#39;s drive engine is adjusted as needed to maintain proper hydraulic line pressure. EPA valve  53  in the H 2 O 2  line is closed and main H 2 O 2  reciprocating EPA valve  55  from tank  54  is opened, allowing peroxide to flow to pump  60 . H 2 O 2  delivery valve  48  is also opened. Control joystick  62 , coupled to the electro-hydraulic motor/controller  63  for pump  60 , is slowly throttled on and off in slight increments to initially introduce H 2 O 2 to the catalyst engine  10 . 
         [0031]    As this process is continued decomposition proceeds and catalyst temperature gauge  35  starts reading above 250° F. Once this temperature is achieved, the catalyst engine  10  is preheated enough to allow the introduction of a steady flow of H 2 O 2  to the engine. This is accomplished by slightly easing the joystick  62  for the electro-hydraulic valve controller forward (open). H 2 O 2  pump PSI gauge  41  allows the operator to monitor the pressure at which H 2 O 2  is being fed into the catalyst engine  10 . The temperature on the catalyst engine gauge  35  will momentarily climb to between 800° F. and 900° F. Well injection temperature, as monitored on temperature gauge  43 , will also rise and equal out to the catalyst engine temperature. Depending on the operator&#39;s location, the operator can hear the catalyst engine on the tree assembly  11  as shown in  FIG. 5 , and can also visually verify its exhaust through normally open EPA valve  44  passing into the atmosphere. 
         [0032]    It is to be recognized that joystick  62  for the electro-hydraulic motor/controller  63  for peroxide pump  60  is a “dead man” operator, meaning that it is normally in the off or closed position and returns to the off position automatically when hand operating pressure is removed from the joystick. Thus, the controller  63  is also normally closed or off, and open and on only when the joystick gets pushed forward. Once operator pressure is let off the joystick, the controller will immediately and automatically return to the closed off position, shutting off the pump  60 . 
       High PSI H 2 O Check 
       [0033]    With the catalyst engine  10  running at the desired operating temperature, high PSI H 2 O delivery EPA valve  72  is opened, and high PSI H 2 O pumps  66 A and B are activated individually. The operator will see volumes of steam, resulting from the contact between the introduced water and the high temperature engine exhaust products, exhausting to atmosphere from catalyst tree assembly  11 . H 2 O high PSI gauge  37  on the control panel, monitoring the pressure of the injected water, will also confirm the pressure at which the water is being introduced. As water is introduced, well injection temperature gauge  45  will read lower than catalyst temperature gauge  35 . After the high PSI check is completed, high PSI H 2 O pump  66 A/B is turned off to stop introduced water flow. (If one of the high PSI H 2 O pumps  66 A, B has a failure, the other pump can be used.) 
         [0034]    Joystick  62  is released to shut off peroxide pump  60 , and main H 2 O 2  reciprocating EPA valve  55  and high PSI H 2 O delivery EPA valve  72  are closed. H 2 O 2  reciprocating pump EPA valve  53  is opened. 
       4) System Run 
       [0035]    The system is now ready for well injection. At this point a desired well injection temperature is determined, and a main gate valve (not shown) on the well, attached to the catalyst tree assembly  11  by means of knockoff coupler  32 , must be open. H 2 O 2  reciprocating pump EPA valve  53  is closed, and H 2 O 2  valves  55  and  48  are opened. Joystick  62  for the electro-hydraulic motor/controller  63  is throttled to start up catalyst engine  10 . Once the catalyst engine  10  is at operating temperature, typically 800° F,-900° F.), observed on the catalyst temperature gauge  35 , high PSI H 2 O delivery EPA valve  72  is opened and high PSI H 2 O pump  66 A or B is activated. When the determined well injection temperature is met and maintained by observing well injection temperature gauge  43  (and is obtained by cycling high PSI H 2 O pump  66 A or B) the normally closed (N/C) tree EPA valve  46  is opened and the normally open (N/O) tree EPA valve  44  is closed, stopping venting and allowing the engine exhaust and introduced water blend to enter the well. Joystick  62  is throttled as required to maintain pressure. N/C tree EPA valve  46  must be opened before N/O tree EPA valve  44  is closed. By the operator throttling forward on the joystick  62 , appropriate delivery pressure into the well can be controlled and maintained as the operator observes the well injection PSI gauge  45 . 
       6) Chemical Injection 
       [0036]    While the system is running down hole, chemical additives can be injected by blending them with injected water. Chemical EPA valve  68  is opened to feed the additive to pumps  66 . The additive is introduced into the high pumps through a suction port. 
       7) Shutdown and Peroxide Line Flush 
       [0037]    Well stimulation is typically completed when the well PSI gauge  45  shows a spike in pressure. Once the injection is completed, N/O tree EPA valve  44  is re-opened and N/C tree EPA valve  46  is closed. High PSI H 2 O pump  66 A or B is shut down, high PSI delivery EPA valve  72  is closed, joystick  62  is released, H 2 O 2  delivery EPA valve  48  is closed, H 2 O 2  reciprocating pump valve  55  is opened and H 2 O 2  tank EPA valve  53  is closed. 
         [0038]    To flush the H 2 O 2  fuel line H 2 O 2  tank EPA valve  55  must be closed. The H 2 O 2  fuel line is disconnected from catalyst engine  10 , and the disconnected end of the line is placed in a bucket half full of water. H 2 O flush EPA valve  59  is opened, and the line is flushed out until only H 2 O is present. H 2 O flush EPA valve  59  is then closed. Air flush EPA valve  57  is opened until the remaining water in the line is removed, and the air flush EPA valve is then closed. The now clean H 2 O 2  delivery line is capped and disconnected for storage. The peroxide-containing flush bucket is topped off with water and the diluted H 2 O 2  discarded as appropriate. 
         [0039]    Low PSI H 2 O pump  64 A, B or C is shut down. Master power switch  75  for the control panel is turned off. The hydraulic gas drive, compressor, and generator are shut down. Tree  15  is disconnected from the well. A backup manual override system may be provided to activate the low PSI H 2 O pump and delivery line if water is needed at any time. 
         [0040]    The present system provides for effective and precise control over peroxide decomposition, blending of the decomposition products with water and additives as desired, and monitoring of injection of the resulting high temperature blend into a well or other facility. It also allows for efficient trouble shooting and shutdown in the unlikely event of a problem. 
         [0041]    If the catalyst temperature radically declines, H 2 O 2  pump PSI gauge  41  can be checked for pressure. 
         [0042]    If there is a large decrease in pressure, a normal shutdown sequence can be followed, as there is no available H 2 O 2 . If pressure reads correct, joystick  62  should be immediately released. High PSI H 2 O pump  66 A or B should remain active for approximately five seconds to assist in cooling the system; N/O tree EPA valve  44  is then opened to vent the system to the atmosphere while N/C tree EPA valve  46  is closed to cap the well. 
         [0043]    If there is a loss of H 2 O pump  66 A or B pressure, N/O tree EPA valve  44  should be opened N/C tree EPA valve  46  closed. Joystick  62  is released and H 2 O low and high PSI checks performed. Once the checks are completed, shut down any defective pump and energize back ups.