Patent Publication Number: US-2007115756-A1

Title: Valve for Gases As Used In Automated System for Setting Chamber Gas Pressures

Description:
BACKGROUND OF THE INVENTION  
      Since the late 1930s the so-called acoustic sounding, or echometering, method has been used in the oil industry for taking distance measurements in an oil well or borehole, see U.S. Pat. No. 2,927,301, Booth, Measurement of liquid levels in wells. The acoustic sounding method involves sending a short, sharp, clear, loud bang sound down an oil well or borehole and using a transducer to “listen” to the echoes reflected back. The signal from the transducer is usually recorded for analysis which is usually performed by a separate device: see U.S. Pat. 2,209,944, Walker, Method of measuring location of obstructions in deep wells, and U.S. Pat. 2,232,476, Ritzmann, Method and apparatus for measuring depth in wells.  
      As explained in these patents and other literature, the acoustic sounding method not only determines the distances between the source of the sound and the causes of the echoes, but also determines the physical nature of the causes of the echoes based on the frequency, amplitude, and other attributes of the sound being reflected back. For example, in its application in oil wells the acoustic sounding method can not only determine the distance to the “bottom” of the well, i.e. the fluid level of the well, but it can also determine other attributes and anomalies, such as wax, scale, or gas build-up and other obstructions, encountered down the well based on the nature of the echoes received at the wellhead by the transducer.  
      Further the acoustic sounding method itself has other distance measuring and obstruction analysis applications beyond its use in oil wells. As an example, an early application of the acoustic sounding method was used by the postal service in New York City in the early 1900s to locate mail bags stuck in mail transportation tubes.  
      One common method for generating the sound needed for the acoustic sounding method is to use an air or gas pressurized chamber which is discharged at or near the wellhead or the void to be analyzed. As described in U.S. Pat. 4,750,583 and 4,646,871, Wolf, Gas-Gun for Acoustic Well Sounding (hereinafter “Wolf”) the sound generated by the pressurized chamber comes from the energy released by the equilibration of the different pressures between the chamber and the wellhead or the void. A different, earlier method for generating the sound needed for the acoustic sounding method was to fire a blank cartridge from a firearm at the wellhead. Accordingly the oil industry has coined the term “sound gun”, “echo gun”, “acoustic gun”, or simply “gun” to generally describe devices that produce the sound needed for the acoustic sounding method.  
      Although acoustic generators, acoustic guns using a pressurized gas chamber, have been used for many years, these acoustic generators have failed to address a number of issues in their use and have failed to yield the full benefits of the acoustic sounding method as an analytical tool for measuring distances and analyzing physical attributes.  
     BRIEF SUMMARY OF THE INVENTION  
      The current invention is the application of the acoustic sounding method by using a vastly improved acoustic generator and surveyor unit. The benefits of the current invention include, but are not limited to: 
      a device for automatically setting gas pressures in various chambers for numerous uses and applications including, but not limited to, setting the pressures for the various chambers in an acoustic generator;     a mechanism for automatically setting the gas pressures of various chambers in a device based on a control gas pressure for numerous uses and applications including, but not limited to, a mechanism for automatically setting the gas pressures for the various chambers of an acoustic generator based upon the void gas pressure;     a unique differential regulator that is used in a mechanism for automatically setting the gas pressures of various chambers in a device based on a control gas pressure;     an acoustic generator with the ability to automatically set the pressure chamber of the acoustic generator to any desired pressure;     an acoustic generator with the ability to automatically set the pressure chamber of the acoustic generator to a suitable pressure with respect to the void pressure for firing the acoustic generator in either the explosion mode or implosion mode;     an acoustic generator with the ability to automatically set the pressure chamber of the acoustic generator to a gas pressure difference that is relative to, and based upon, the void gas pressure at the time of automatic setting;     an acoustic generator with the ability to automatically set the pressure chamber of the acoustic generator to a gas pressure difference that is relative to, and based upon, the void gas pressure for any void gas pressure;     an acoustic generator with the ability to automatically set the pressure chamber of the acoustic generator to a gas pressure difference that is relative to, and based upon, the void gas pressure for any gas pressure difference;     an acoustic generator with the ability to fire the pressure chamber of the acoustic generator at any pressure setting;     an acoustic generator with the ability to fire the pressure chamber of the acoustic generator for any pressure difference between the pressure chamber and the void;     an acoustic generator with the ability to fire the pressure chamber of the acoustic generator for any void gas pressure;     an acoustic generator with the ability to automatically set the arming and firing mechanism of the acoustic generator;     an acoustic generator with a firing mechanism that will fire for any pressure in the pressure chamber;     an acoustic generator with a firing mechanism that will fire the pressure chamber for any void gas pressure;     an acoustic generator with a firing mechanism that will fire for any gas pressure difference between the pressure chamber and the void;     an acoustic generator with an automated mechanism for controlling the timing of the arming and firing of the acoustic generator;     an acoustic generator with a unique outlet or portal design from the pressure chamber for the efficient and effective generation of the desired sound needed for the acoustic sounding method;     an acoustic generator with a unique design and configuration of the microphone element and unit for the efficient and effective detection of echoes from the void;     an acoustic generator that produces a shorter, sharper, and clearer sound wave than any prior art acoustic generator; and     a surveyor unit used in the acoustic sounding method with unique attributes for analyzing echo information and data retrieved from the application of the acoustic sounding method.    

      The current invention is also a component of a real time control system for oil well pumping operations. The objective of the real time control system being to optimize oil production from an oil field. The current invention is a key component to this real time control system because it provides a practical method for providing the oil field operator real time information and feedback about the fluid level status and other physical statuses of the wells in their oil field. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1   a  is a cross sectional view of the Acoustic Generator with Main Body Housing (Portable Unit) in a preferred embodiment of the current invention.  
       FIG. 1   b  is a cross sectional view of the Main Body Housing (Stationary Unit) in a preferred embodiment of the current invention.  
       FIG. 2  is a cross sectional view of the internal module of the Acoustic Generator in a preferred embodiment of the current invention.  
       FIG. 2   a  is a cross sectional view of two different versions of the Stable Pressure Regulator Shaft used in preferred embodiments of the current invention.  
       FIG. 2   b  is a cross sectional view of three different versions of the Nub Bobbin and Piston used in preferred embodiments of the current invention.  
       FIG. 2   c  is a rear face view of two different versions of the Piston Section used in preferred embodiments of the current invention.  
       FIG. 2   d  is a side and cross sectional view of two different versions of Pressure Chamber Sleeves used in preferred embodiments of the current invention.  
       FIG. 2   e  is a side view of the Stable Pressure Regulator Spring Guide Spacer used in a preferred embodiment of the current invention.  
       FIG. 2   f  is a side view of the Fire Bobbin Spring Guide Spacer used in a preferred embodiment of the current invention.  
       FIG. 2   g  is a perspective view of the microphone element and microphone wires used in a preferred embodiment of the current invention.  
       FIG. 2   h  is a cross sectional view of the microphone element and microphone wires used in a preferred embodiment of the current invention.  
       FIG. 3  is a cross sectional exploded view of the internal components of the Acoustic Generator in a preferred embodiment of the current invention.  
       FIG. 3   a  is a cross sectional exploded view of the components of the Stable Pressure Regulator used in a preferred embodiment of the current invention.  
       FIG. 3   b  is a cross sectional exploded view of the components of the Differential Regulator used in a preferred embodiment of the current invention.  
       FIG. 3   c  is a view of the components of the Microphone Area of the Acoustic Generator used in a preferred embodiment of the current invention.  
       FIG. 4   a  is a view of the rear of the Top Section in a preferred embodiment of the current invention with the figures denoting the locations of the components placed in the Top Section.  
       FIG. 4   b  is a view of the front of the Top Section in a preferred embodiment of the current invention with the figures denoting the locations of the components as placed in the Top Section.  
       FIG. 4   c  is a view of the rear of the Piston Section in a preferred embodiment of the current invention with the figures denoting the locations of the components as placed in the Piston Section.  
       FIG. 4   d  is a view of the front of the Piston Section in a preferred embodiment of the current invention with the figures denoting the locations of the components as placed in the Piston Section.  
       FIG. 5  is an exploded view of the rear of the Piston Section used in a preferred embodiment of the current invention showing components as placed in the Piston Section.  
       FIG. 6   a  is a schematic depiction of the components, chambers and passages of an embodiment of the Acoustic Generator in the armed position (explosion mode).  
       FIG. 6   b  is a schematic depiction of the components, chambers and passages of an alternative embodiment of the Acoustic Generator in the armed position (explosion mode).  
       FIG. 7   a  is a schematic depiction of the components, chambers and passages of an embodiment of the Acoustic Generator in the standby/fired position (explosion mode).  
       FIG. 7   b  is a schematic depiction of the components, chambers and passages of an alternative embodiment of the Acoustic Generator in the standby/fired position (explosion mode).  
       FIG. 8   a  is a schematic depiction of the components, chambers and passages of an embodiment of the Acoustic Generator in the armed position (implosion mode).  
       FIG. 8   b  is a schematic depiction of the components, chambers and passages of an alternative embodiment of the Acoustic Generator in the armed position (implosion mode).  
       FIG. 9   a  is a schematic depiction of the components, chambers and passages of an embodiment of the Acoustic Generator in the standby/fired position (implosion mode).  
       FIG. 9   b  is a schematic depiction of the components, chambers and passages of an alternative embodiment of the Acoustic Generator in the standby/fired position (implosion mode).  
       FIG. 10  is a face view of a Surveyor Unit in a preferred embodiment of the current invention.  
       FIG. 11  is a flowchart depicting the instructions executed by the signal processor, main processor, and i/o processor of a Surveyor Unit in a preferred embodiment of the current invention.  
       FIG. 12  is a block diagram depicting the components of a Surveyor Unit in a preferred embodiment of the current invention.  
       FIG. 13  is a copy of a typical strip chart printed by a preferred embodiment of the current invention from an acoustic sounding of a 12,000 foot well.  
       FIG. 14   a  is a view of the setup between the wellhead, Acoustic Generator, Compressed Gas Source, and Surveyor Unit in applying the acoustic sounding method in a preferred embodiment of the current invention.  
       FIG. 14   b  is a view of the Surveyor Unit and a programmed computer for downloading the data collected by the Surveyor for offsite analysis of the data collected in the acoustic sounding method in a preferred embodiment of the current invention.  
       FIG. 15  is a graph depicting the sound generated by a preferred embodiment of the current invention at 10 Hz under the benchmark test conditions described herein.  
       FIG. 16  is a graph depicting the sound generated by a preferred embodiment of the current invention at 20 Hz under the benchmark test conditions described herein.  
       FIG. 17  is a graph depicting the sound generated by a preferred embodiment of the current invention at 40 Hz under the benchmark test conditions described herein.  
       FIG. 18  is a graph depicting the sound generated by a preferred embodiment of the current invention at 70 Hz under the benchmark test conditions described herein.  
       FIG. 19  is a graph depicting the sound generated by a SONOLOG D-6C2 at 10 Hz under the benchmark test conditions described herein.  
       FIG. 20  is a graph depicting the sound generated by a SONOLOG D-6C2 at 20 Hz under the benchmark test conditions described herein.  
       FIG. 21  is a graph depicting the sound generated by a SONOLOG D-6C2 at 40 Hz under the benchmark test conditions described herein.  
       FIG. 22  is a graph depicting the sound generated by a SONOLOG D-6C2 at 70 Hz under the benchmark test conditions described herein.  
       FIG. 23  is a graph depicting the sound generated by an ECHOMETER COMPACT GAS GUN at 10 Hz under the benchmark test conditions described herein.  
       FIG. 24  is a graph depicting the sound generated by an ECHOMETER COMPACT GAS GUN at 20 Hz under the benchmark test conditions described herein.  
       FIG. 25  is a graph depicting the sound generated by an ECHOMETER COMPACT GAS GUN at 40 Hz under the benchmark test conditions described herein.  
       FIG. 26  is a graph depicting the sound generated by an ECHOMETER COMPACT GAS GUN at 70 Hz under the benchmark test conditions described herein. 
    
    
     DETAILED DESCRIPTION OF INVENTION  
      The following table is a list of the various components that are used in a various preferred embodiments of the current invention as described herein. Note that some of the components listed are optional or are used in some preferred embodiments of the current invention but in other preferred embodiments:  
               TABLE 1                          List of Components                             No.   Name                        0   Acoustic Generator            1   Main Body Housing            1a   Main Body Housing (Portable Unit)            1b   Main Body Housing (Stationary Unit)            2   Handle Plate            3   Handle            4   Handle Leg            5   Lanyard            6   Lanyard Ring            7   Lanyard Guide            8   Modified Female Quick Connect            9   Modified Male Quick Connect            10   Lock Ring            11   Fire Bobbin O-ring            12   Piston Valve            13   Threaded hole in Nub            14   Nub O-ring            15   Piston Flange O-ring            16   Piston Shaft O-ring            17   Piston Section O-ring for Piston Shaft            18   Set screws on Piston Section            19   Piston Section O-ring            20   Piston Section            21   Top Section            22   Piston Shaft            23   Fire Bobbin            23c   Fire Bobbin Cylinder            24a, b, c   Slide Bobbins            25   Differential Regulator Shaft            26   Stable Pressure Regulator Shaft            27   Stable Pressure Regulator Seat            28   Filter Spacer/Tool            29c   Nub Channel            29   Piston Nub            30   Fire Tube            31   Wave Guide Nut            32   Microphone Holder            33   Microphone Cap            34   Microphone Element            35a, b, c   Filter Screens            36   Set Screw for Microphone Nut            37   Set Screw for Tubes            37s   Piston Nub Set Screw            38a, b, c   Split Bobbin O-ring            39   Fire Tube O-ring            40   Support Tube            40s   Support Tube Socket            41   Support Tube Sleeve            42   Support Tube Anchor Set Screw            43   O-ring for Support Tube            44   Filter Spacer/Tool O-ring            45   Differential Regulator            45c   Differential Regulator Cylinder            46   Microphone Cavity            46s   Microphone Cavity Section            47   Differential Regulator Relief Spring            48   Stable Pressure Regulator            48a   Stable Pressure Regulator Chamber            48b   Stable Pressure Regulator Channel            48c   Stable Pressure Regulator Cylinder            49   Top Section Piston Cylinder O-ring            50   Fire Bobbin Spring            50g   Fire Bobbin Spring Guide Spacer            51   Differential Regulator Spring            52   Stable Pressure Regulator Spring            52g   Stable Pressure Regulator Spring Guide Spacer            53   Stable Pressure Regulator Seat O-ring            54a, b   Differential Regulator O-rings            55a, b, c   Filter Screen O-rings            56a, b, c, d   Stable Pressure Regulator O-rings            57a   Stable Pressure Regulator E-clip            57b   Differential Regulator E-clip            58a, b   Microphone Wires            59   Solenoid Wire            60   Data Connector            60r   Data Connector Receiver            61   Data Cable            61w   Wiring Compartment            62   Data Channel            63   Microphone Wire Channel            64   Solenoid Wire Channel            65   Cap Screws            66   Male Quick Connect            66c   Top Section Gas Inlet            66r   Male Quick Connect Receiver            67   Top Section Gas Connect O-ring            68   Data Connector Set Screw            69   Cap Screw Receiver Hole            70   Solenoid            70c   Solenoid Passage            71a, b   Solenoid O-rings            72   Piston Cylinder            73   Piston Flange            73a   Piston Flange O-ring            74   Piston Screen            75   Nub Top Section O-ring            76   Screwdriver Slot            77   Pressure Transducer            77s   Pressure Transducer Seat            78   Pressure Transducer O-ring            79   Pressure Transducer Wire            80   Pressure Chamber            80s   Pressure Chamber Section            81b, c   Vent Chamber Channels            82   Piston Cylinder Guide            83   Nub Chamber            84   Fire Tube Valve            85a   Filter Screen Chamber            85b   Filter Screen and Tool Chamber            86   Microphone Element O-rings            87   Zanier Diode            88   Resistor            89   Edge Bevel            90   Pneumatic Computer            90   Pneumatic Computer Section            91a, b, c   Spring Chambers            92   Wave Guide O-ring            93   Small Pressure Chamber Sleeve            93a   Small Pressure Chamber Sleeve O-rings            94   Large Pressure Chamber Sleeve            94a   Large Pressure Chamber Sleeve O-rings            99   Compressed Gas Source           100   Surveyor Unit           102   Panel Mount Jack           103   Display Window           104   Face Panel           105   Acoustic Velocity Knob           106   Depth/Changeover Knob           107   Off/On Gain Menu Knob           108   Fire Button           109   Measured Segment Knob           110   Feet in Segment Knob           111   Inches to Fluid Knob           112   Compact Printer           113   Printer Port           114   12v Power Jack           115   USB Port           116   Hold-down Bracket           121   Surveyor Unit Lid           125   Surveyor Unit Latch           130   Preamp           132   Solenoid Driver           134   A/D Converter           136   Gain Stage 1           138   Gain Stage 2           140   CPU           142   RAM           144   Flash Memory           150   RS-232 Interface           152   Real-Time Clock           154   USB Interface           160   Power Supply           162   LEDs           164   Encoders           166   Battery           168   External Power Supply                      
 
 Configuration of the Acoustic Generator and Surveyor Unit 
 
      As depicted in  FIG. 14   a , in a preferred embodiment of the current invention the Acoustic Generator  0  is connected to the well annulus at the wellhead by a ½ inch NPT Modified Female Quick Connect  8  on the Main Body Fitting (Portable Unit)  1   a . A 2 inch pipe threaded end is normally used for an Acoustic Generator  0  with a Main Body Fitting (Stationary Unit)  1   b . For either the portable or stationary configurations the Acoustic Generator  0  is connected to a Compressed Gas Source  99  via the Male Quick Connect  66  using a hose or mounting. The Male Quick Connect  66  is connected to the Top Section Gas Inlet  66   c  in the Acoustic Generator  0 .  
      The Surveyor Unit  100  is electronically connected to the Acoustic Generator  0  via a Data Cable  60   c  and controls all of the automatic functions of the Acoustic Generator  0 .  
      In a preferred embodiment of the current invention the connections between all the components can be completed prior to installing the Acoustic Generator  0  to the well annulus thus allowing single-hand installation of the Acoustic Generator  0 .  
      As explained above acoustic soundings for oil wells are normally made within the inside wall of the casing pipe and the exterior of the production tubing string hanging within the casing pipe. The casing pipe is normally cemented in place within the oil producing borehole. The production tubing is normally formed from relatively uniform sections of steel tube screwed together using joints known as collars. As explained herein, the average distance between collars and the echoes created by the collars are used to calibrate readings obtained by an acoustic generator.  
      Acoustic Generator  
      In a preferred embodiment of the current invention, the Acoustic Generator  0  has two static positions, the fired/standby position and the armed position. In operation the Acoustic Generator  0  is initially at rest in the fired/standby position, is moved to the armed position, and is fired to return to the fired/standby position.  
      As depicted in  FIG. 1   a  in a preferred embodiment of the current invention the Acoustic Generator  0  is made of an internal module, see  FIG. 2 , which is placed inside a Housing  1  and secured by a Lock Ring  10  at the rear of the Acoustic Generator  0 .  
      The Acoustic Generator  0  also has several alternative embodiments and optional parts depending on the needs of the acoustic sounding for a particular well or void. As explained above and shown in  FIG. 1   a  and  FIG. 1   b , the Acoustic Generator  0  has alternative housings for alternative configurations and connections at the wellhead. Further as shown in  FIGS. 2   a  to  2   h  inclusive,  FIGS. 6   a  to  9   b  inclusive, and as explained further herein, several components in the Acoustic Generator  0  have alternative designs depending on the needs of the acoustic sounding method being applied. Also, as explained further herein, there are several optional components with the Acoustic Generator  0  to assist in use and operation, such as the Filter Spacer/Tool  28  which is used for disassembling and reassembling the Acoustic Generator  0  for maintenance and repair purposes.  
      In addition, unless stated otherwise, the components in the preferred embodiments of the Acoustic Generator  0  are made of high quality stainless steel and the O-rings identified are of Buna-N. Also stainless steel E-clips, screws, and springs have been used in preferred embodiments of the current invention. However, the Acoustic Generator  0  can use alternative comparable materials and alternative comparable components that provide the same functions as O-rings, E-clips, valves, screws, springs, flanges and stops. For example, in a preferred embodiment of the current invention, the four springs used in the Acoustic Generator  0  are all commercially available but can easily be replaced by alternative components that produce the same function and performance. In a preferred embodiment of the current invention the specifications of the springs are as follows:  
               TABLE 2                          Spring specifications in a preferred embodiment of the current invention                                                                         Solid                   Part       Free   Wire   Total   Coil   Solid   Spring       Component   Number*   OD   Length   Diameter   Coils   Height   Load   Rate                                                         Differential Regulator   C180-500-19000   0.180   0.500   0.024   8.5   0.228   5.16   19.00       Relief Spring 47       Fire Bobbin Spring 50   C180-875-14500   0.180   0.875   0.026   14.5   0.403   6.84   14.50       Differential Regulator   C300-687-62000   0.300   0.687   0.045   7.5   0.382   18.87   62.00       Spring 51       Stable Pressure   C300-687-62000   0.300   0.687   0.045   7.5   0.382   18.87   62.00       Regulator Spring 52                 *MSDivisions, a division of Commercial Communications LLC of Middletown, NY             
 
      As depicted in  FIG. 1   a , in a preferred embodiment of the current invention the Acoustic Generator  0  is cylindrical in shape and can be viewed as having three distinct areas (moving from the rear to front): the Pneumatic Computer area, the Pressure Chamber area, and the Microphone Cavity area. These three areas can be loosely associated with the three basic functions of the Acoustic Generator  0 , i.e. arming a pressure chamber, firing the pressure chamber, and detecting the echoes received, but as explained herein each area of the Acoustic Generator  0  plays a role in each of the three basic functions.  
      Pneumatic Computer Area  
      In a preferred embodiment of the current invention the Pneumatic Computer  90  not only controls the arming and firing of the acoustic generator&#39;s Pressure Chamber  80  but also controls of the functions of gas pressure regulation, control, timing, delivery, and evacuation for the other chambers, cylinders, channels and passages in a preferred embodiment of the Acoustic Generator  0 . As shown in  FIGS. 3, 4   a  to  4   d , and  5 , in a preferred embodiment of the current invention the Pneumatic Computer  90  area contains most of the components of the Acoustic Generator  0 .  
      Top and Piston Sections  
      As shown in  FIG. 3 , in a preferred embodiment of the current invention the two largest components of the Pneumatic Computer  90  are the Top Section  21  and the Piston Section  20 . As shown in  FIGS. 3, 4   a  to  4   d , and  5 , in a preferred embodiment of the current invention the Top Section  21  and the Piston Section  20  are joined together by three Cap Screws  65  located in the Cap Screw Receivers  69  in the Top Section  21  and the Piston Section  20 . The three Cap Screws  65  are accessible, and can be removed from, the rear of the Top Section  21 . When the Cap Screws  65  are removed, the Top Section  21  and Piston Section  20  spring apart as a result of the spring pressure that exists between the various components of the Pneumatic Computer  90 .  
      In separating the Top Section and Piston Section the first noticeable aspect of the interior of the Pneumatic Computer  90  is that there are no tubes, pipes, or other fallible connections. The pneumatic connections in the body of the Pneumatic Computer  90  are all made by machined cross channels, holes, and cylinders which are conjoining each other within the Top Section  21  and Piston Sections  20 .  FIGS. 6   a  through  9   b  schematically depict the components and the relationship between the chambers, cylinders, channels and passages used in two preferred embodiments of current invention.  
      Where the Top Section  21  and Piston Section  20  face together there are five O-rings  49 ,  67 ,  75 ,  71   a  and  71   b  to seal the pressure channels between the two Sections. A Piston Cylinder O-ring  49  is set around a raised Piston Cylinder Guide  82  and used to seal the Fire Piston Cylinder  72 . The other four O-rings  67 ,  71   a ,  71   b  and  75  seal the rest of the pneumatic passages in between the Top Section  21  and the Piston Section  20 . This assembly configuration of a preferred embodiment of the Pneumatic Computer  90  allows the components and working parts of the Pneumatic Computer  90  to be removed, replaced, or cleaned quickly. When the two Sections are apart, every component and working part can be removed from the Top Section  21  and Piston Section  20  by hand. In disassembly there may be working parts or components in either Section, but generally all will remain with the Piston Section  20 .  
      As shown in  FIG. 3   b , on the front side of the Top Section  21  are Spring Holes  91   a - c  for the springs over several components, and O-ring slots for the various O-rings. There is also a machined Solenoid Wire Channel  64  for the control wires coming from the Solenoid  70  and going over to the Data Cable  61  in the Top Section  21 . In the Top Section  21 , there are two small machined Vent Channels  81   b  and  81   c  being attached to various component Spring Chambers  91   b  and  91   c  and over to the outer edge of the Top Section  21 . The Vent Channels allow the gas from the internal components to be dissipated into an Edge Bevel  89  surrounding 180 degrees around the outer circumference of the rear end edge of the Piston Section  20 . In a preferred embodiment of the current invention a flat surface of the Edge Bevel  89  can be between 0.03 inches to 0.30 inches with a bevel angle of 30 to 60 degrees, with 0.085 inches and a 45 degree Edge Bevel  89  working the best. This is a safety feature of a preferred embodiment of the current invention as gas pressure released from the two Vent Channels  81   b  and  81   c  to the atmosphere is rendered harmless by being bled down through the Edge Bevel  89  and disbursed into the space that is left between the outer diameter of the Top Section  21  and the inside diameter of the Lock Ring  10 .  
      Pneumatic Computer Components  
      The following is a description of the components present in a preferred embodiment of the current invention starting with the components in the Top Section  21 .  
      Piston Nub  
      As shown in  FIG. 1 , in a preferred embodiment of the current invention inside the center of the Top Section  20  is a Nub Bobbin  29 . In a preferred embodiment of the current invention the Nub Bobbin  29  is about ½ in diameter. The Nub Bobbin  29  acts as a pressure compensation bobbin for the Piston Shaft  22 . The Nub Bobbin  29  pushes down on the top of the Piston Shaft  22  with the same void pressure entering into the front of the Acoustic Generator  0 . In a preferred embodiment of the current invention the void pressure that might affect the operation of the instrument is balanced and neutralized against itself by utilizing the Nub Bobbin  29 . The nub pressure comes directly from the void pressure to equalize and compensate for the well pressure entering the front of the Acoustic Generator  0  and pressuring the front of the Piston Shaft  22 . This compensation or equalizing allows the Piston Shaft  22  to be operated with a separate Stable Pressure gas driven firing system as described herein.  
      As shown in  FIG. 2   b  there are three alternative versions of the Nub Bobbin  29  for various preferred embodiments of the current invention. In Version A, the Nub Bobbin  29  is solid and completely free and separate from the Piston Shaft  22 . In Version A the void pressure is fed to the rear the Nub Bobbin  29  through the Pneumatic Computer  90 . This is achieved by using Version A of the Piston Section  20  as shown in  FIG. 2   c , which links the inlet from the Pressure Transducer  77  to the Nub Port  29   c . Schematically this is depicted in  FIG. 6   a  which shows the inlet from the void to the Pressure Transducer  77  being continued to the rear of the Nub Bobbin  29 . Version B and Version C as shown in  FIG. 2   b  work by connecting a Nub Bobbin  29  with a passageway as an extension of a Piston Shaft  22  with a passageway, the passageways of the Piston Shaft  22  and Nub Bobbin  29  allowing the void gas to pass through the Piston Shaft  22  to the rear of the Nub Bobbin  29 . As the void gas does not need to pass through the Pneumatic Computer  90  in this arrangement, the channel from the Pressure Transducer  77  to the Nub Port  29   c  is omitted, as depicted in Version B of the Piston Section  20  as shown in  FIG. 2   c  and schematically depicted in  FIG. 6   b.    
      In a preferred embodiment of the current invention the Nub Bobbin  29  may be removed for maintenance or Nub O-ring  14  replacement with the same Filter Screen/Tool  28  threaded tool that is used for removing the Filter Screens as described herein.  
      Wire Components  
      As shown in  FIGS. 1 and 5 , in a preferred embodiment of the current invention the Pneumatic Computer  90  has a commercially available Pressure Transducer  77  to read the void pressure at any given time. The Pressure Transducer  77  sends its results through its wires to any electronics in sync with its specifications. The Pressure Transducer  77  may be easily removed from its Seat  77   s  and replaced after the Top Section  21  and the Piston Section  20  have been separated and the Pressure Transducer Wires  79  have been disconnected from the Data Connector  60 . The Top Section  21  has a Data Channel  62  on the outer edge of the Data Connector Receiver  60   r . The Data Cable  61  which includes the Pressure Transducer Wires  79 , the Microphone Wire  58 , and the Solenoid Wire  59  can be brought out through the Data Channel  62  after the Data Connector Set Screw  68  is unscrewed from the Data Connector  60  and released. This allows the sections to be moved further apart without unduly disturbing the wiring. The only wire still attached to the Top Section  21  is the Solenoid Wire  59  which is coiled into the open wiring compartment space around the Data Connector  60  when assembled.  
      Piston Section Components  
      As shown in  FIG. 5 , in a preferred embodiment of the current invention the major components that are housed in the Piston Section  20  will be described as viewed in order clockwise beginning at the Filter Screen/Tool  28 .  
      Note although it is a component in the Piston Section  20  as depicted, the Piston Shaft  22  is more fully described in the Pressure Chamber area.  
      Filter Screen/Tool and Filter Screens  
      In a preferred embodiment of the current invention the Pneumatic Computer  90  houses a Filter Screen/Tool  28  which is a spacer for the Filter Screen  35   b  below it. It also has a threaded shaft on one end which is used as a removal tool for the Filter Screens,  35   a  and  35   b , and the Piston Nub  29  which is located inside the Top Section  21 . The threaded shaft of the Filter Screen/Tool  28  is used to remove the Filter Screens  35   a  and  35   b  by inserting it into the exposed end of the Filter Screen, turning the tool clockwise and pull up and out to remove. Pulling the stainless steel Filter Screen  35   b  out for cleaning is also the first step for a complete breakdown of the Acoustic Generator  0 . This enables the sections to be submerged in solvent and the channels within the Top and Piston Sections cleaned in total. The Filter Screen  35   a  filters the Stable Pressure gas from the Stable Pressure Regulator  48  into the center or feed of the Solenoid  70 .  
      Differential Regulator  
      A component within the Pneumatic Computer for a preferred embodiment of the current invention is the Differential Regulator  45 , as shown in  FIG. 3   b . In a preferred embodiment of the current invention the Differential Regulator  45  is an assembly of components that is a little over an inch in length. The Differential Regulator  45  consists of a Center Shaft  25  with shoulders or stops at both ends and the following assembled components, starting from the rear moving to the front: a small Relief Spring  47  resting on the rear shoulder of the Center Shaft  25  with the front end of the Relief Spring  47  compressing against the rear end of a Slide Bobbin  24   b . Against the front end of a Slide Bobbin  24   b  is the rear end of a Differential Pressure Spring  51  which has another identical but inverted Slide Bobbin  24   c  on its front end and an E-clip  57   b  or other similar stop holding the assembly to the front end of the Center Shaft  25 . The Slide Bobbins have holes through their centers and are used as valves in conjunction with O-rings  54   a ,  54   b  on the Center Shaft  25 . The Slide Bobbins also have external O-rings  38   b ,  38   c  which will allow the bobbins to be used as valves when the Differential Regulator  45  is inside the Differential Regulator Chamber  45   c . The Differential Regulator Chamber  45   c  having two inlets: a front inlet for the void and a rear inlet for the Compressed Gas Source  99 . The Differential Pressure Spring  51  determines the pressure differential in the Pressure Chamber  80  in relation to the void pressure, and the Relief Spring  47  holds the whole assembly in place and rapidly moves air by moving the assembly&#39;s components before their intended usage. The Relief Spring  47  also holds the front Slide Bobbin  24   c  down, using O-ring  54   b  as a closed valve awaiting pressure movement. In a preferred embodiment of the current invention there are two outlet or feed channels connected to the Differential Regulator Chamber  45   c . The front channel feeds the Stable Pressure Regulator  48  and the rear channel feeds the Pressure Chamber  80 . As the regulator is shifted from front to rear and vise versa, the gas pressure flowing into these feed channels is shifted from one source to another. In this configuration of a preferred embodiment of the current invention the Differential Regulator  45  is able to perform several different functions in the operation of the Acoustic Generator  0 .  
      Automated Explosion Vs. Implosion Mode Selection Function  
      As shown in  FIGS. 6   a  through  9   b , one function of the Differential Regulator  45  is that of assessing the operations of the Acoustic Generator  0  for explosion or implosion mode. Depending on the void pressure, a gas pressurized acoustic generator can be armed and fired in one of two modes: the explosion or implosion mode. The explosion mode requires an external source of gas pressure to arm the gun&#39;s chamber to a pressure above the void pressure. In firing the gun the sound is generated by the higher pressure gas in the chamber entering the void. Alternatively, the implosion mode sets the gun&#39;s chamber to a pressure below the void pressure. In firing the gun the sound is generated by the higher gas pressure in the void entering the chamber.  
      In a preferred embodiment of the current invention the question of whether to arm the Acoustic Generator  0  in the explosion or implosion mode is automatically determined by the Pneumatic Computer  90  through the Differential Regulator  45  which responds to the source of the greater pressure: the void pressure at the front or the Compressed Gas Source  99  at the rear of the Differential Regulator  45 . In a preferred embodiment of the current invention the Compressed Gas Source  99  also provides the preset gas pressure used to charge the Pressure Chamber  80  in the explosion mode. When the rear of the Differential Regulator  45 , at Slide Bobbin  24   b , is subjected to a greater pressure than the front of the Differential Regulator  45 , at Slide Bobbin  24   c , the entire Differential Regulator  45  acts like a shuttle valve and shifts forward in the Differential Regulator Chamber  45   c . As shown in  FIG. 6   a , with the Differential Regulator  45  in the forward position, the gas from the Compressed Gas Source  99  can flow into the Pressure Chamber and into the Stable Pressure Regulator Chamber  48   a . When the gas pressures are reversed with respect to each other, i.e. void pressure at the front is greater than the Compressed Gas Source  99  pressure at the rear, the Differential Regulator  45  will move to the rear to a position where the Slide Bobbin  24   b  is restrained from further movement by the front face of the Top Section  21 . As shown in  FIG. 8   a , in this position the pressure feed for both channels shifts. The feed channel for the Pressure Chamber  80  is now positioned to feed or vent from the center section of the Differential Regulator  45 . The feed channel for the Stable Pressure Regulator  48  is now in front of the entire Differential Regulator  45  allowing the void pressure to flow freely into this feed channel. As explained herein, in a preferred embodiment of the current invention the Compressed Gas Source  99  provides the basis for a preset gas pressure from which the automatic determination of explosion or implosion mode is made. The Compressed Gas Source  99  can also provide a predetermined gas pressure to charge the Pressure Chamber to in the explosion mode.  
      Implosion Mode Differential Regulation Function  
      The next function in a preferred embodiment of the current invention is the differential regulator function that occurs in the implosion mode. The Differential Regulator  45  maintains a regulated differential pressure between the void and the Pressure Chamber  80  for firing in the implosion mode. In a preferred embodiment of the current invention the Pressure Chamber  80  is ported by the Differential Regulator  45  through Slide Bobbin  24   b  to maintain a constant balance pressure difference between the Pressure Chamber  80  and the void. This regulation is accomplished by the opposing pressures being applied on Slide Bobbin  24   c  when the Differential Regulator  45  is at the rear of the Differential Regulator Chamber  45   c  in the implosion mode as explained above. With the Differential Regulator  45  in this position the void pressure on the front side of Slide Bobbin  24   c  is opposed by the combined pressure of the Pressure Chamber  80  and the Differential Regulator Spring  51  on the rear Slide Bobbin  24   c . In this function the compression resistance of the Differential Regulator Spring  51  determines the relative pressure of the Pressure Chamber  80  to the void. In a preferred embodiment of the current invention, in this function the Differential Regulator Spring  51  can be selected to produce pressure in the Pressure Chamber  80  of 25 pounds per square inch (psi) up to the maximum rated working pressure of the Acoustic Generator  0 , with a range of 50 psi to 500 psi being good and sufficient for acoustic soundings for most oil wells. In a preferred embodiment of the current invention one guide for setting the Pressure Chamber  80  is to set it at a pressure difference of 100 psi plus 10 psi per 1,000 feet of well. In a preferred embodiment of the current invention a pressure difference of approximately 150 to 300 pounds less than the void pressure is found to be the optimum pressure difference for an acoustic sounding of an average oil well. In circumstances when the void pressure is higher than 1000 psi, the chamber pressure area can also be reduced in size using either Version A or Version B of the Pressure Chamber Sleeves shown in  FIG. 2   d  and the differential pressure between the void and the chamber area can be varied anywhere from 150 psi up to the void pressure.  
      Implosion Mode Pressure Chamber Setting Function  
      As shown in  FIG. 9   a  or  9   b , in the standby/fired position in the implosion mode of a preferred embodiment of the current invention the Pressure Chamber  80  is open and has the same gas pressure as the void. In the implosion arm cycle the pressure in the Pressure Chamber  80  needs to be reduced with relationship to the void. This is done by releasing an appropriate amount of gas through the center valve of Slide Bobbin  24   b  into a suitable containment area. In a preferred embodiment of the current invention, as shown in  FIG. 1 , the Pressure Chamber  80  is armed in the implosion mode by the Piston Shaft  22 , which has a Piston Flange  73  and Piston Valve  12 , moving forward to close the Fire Tube Valve  84 . As the Piston Shaft  22  moves forward the Piston Valve  12  opens allowing the gas pressure in the Pressure Chamber  80  to equalize with the gas pressure that exists between the Slide Bobbins  24   b  and  24   c  in the Differential Regulator  45 . When the gas pressure between the Slide Bobbins, along with the pressure from the Differential Spring  51  and the Relief Spring  47 , spreads the two Slide Bobbins  24   b  and  24   c  sufficiently apart the front Slide Bobbin  24   c  meets the Differential Regulator E-clip  57   b  on the Center Shaft  25 . This draws the Center Shaft  25  forward opening the O-ring  54   a  from inside the rear Slide Bobbin  24   b  allowing gas to escape through this channel and the Male Quick Connect  66 . When a sufficient amount of gas from the Pressure Chamber  80  has escaped gas pressure along with the compression tension of both the Differential Spring  51  and the Relief Spring  47 , moves the O-ring  54   a  into Slide Bobbin  24   b  thus closing the path for the escaping gas.  
      In an alternative preferred embodiment of the current invention by restraining the movement of the Center Shaft  25  when the Differential Regulator  45  is in its rearmost position in the armed position any backward movement of the front Slide Bobbin  24   c  caused by an increase in void pressure enables additional gas to enter between the Slide Bobbins  24   b  and  24   c  to the Pressure Chamber  80 . Accordingly in this alternative preferred embodiment of the current invention the difference between the pressure in the Pressure Chamber  80  and the void is constantly maintained even if the void pressure suddenly increases or decreases during the arming cycle.  
      Implosion Mode Differential Regulator Pressure Function  
      In a preferred embodiment of the current invention, when the gas pressure in Pressure Chamber  80  is reduced for firing in the implosion mode, there is also a slight pressure difference between the two Slide Bobbins  24   b  and  24   c  of the Differential Regulator  45  and the Pressure Chamber  80  due to the presence of the Relief Spring  47 . The additional tension of the Relief Spring  47  to the tension of the Differential Regulator Spring  51  will determine the release pressure at which the Differential Regulator Chamber  45   c  gas is allowed to equalize with the Pressure Chamber  80 . In a preferred embodiment of the current invention a range difference of 2 to 50 psi is a possible difference, with a range difference of 3 to 15 psi being good, and a range difference of 5 to 10 psi being the best. The presence of this gas pressure between the two Slide Bobbins  24   b  and  24   c  is sufficient to prevent any chattering effect and to prevent any pressure blast from the Compressed Gas Source  99  from moving the rear Slide Bobbin  24   b  and closing its center passage at an inappropriate time.  
      Safety Bleed Function  
      Another function of the Differential Regulator  45  in a preferred embodiment of the current invention is that of a safety bleed function. If the Acoustic Generator  0  needs to be removed from the well annulus and either the void pressure, i.e. the gas pressure in the chamber around the front of the Microphone Section  74 , and/or the Pressure Chamber  80  is above atmospheric pressure, then either excess pressure can be relieved by putting a rod or other similar device into the Male Gas Quick Connect  66  inlet and gently pushing on the top of the Differential Regulator  45 . This will relieve the excess pressure after the well is shut off and before the Acoustic Generator  0  is removed from the well annulus. This bleed function is important for proper safety and operation of the Acoustic Generator  0 .  
      An alternative way to bleed off unwanted gas pressure is to simply fire the Acoustic Generator  0  when the void pressure is at atmospheric pressure or when the Well Depth is set to “000” on the Surveyor Unit  100 . As explained herein because the firing mechanism is an independent mechanism, the Acoustic Generator  0  can be fired at anytime to equilibrate any gas pressure differences.  
      Stable Pressure Regulator  
      As shown in  FIG. 5 , moving clockwise from the Differential Regulator  45  in the Piston Section  20  is the Stable Pressure Regulator  48 . In a preferred embodiment of the current invention the Stable Pressure Regulator  48  is depicted in  FIG. 3   a . The Stable Pressure Regulator  48  is housed in the Pneumatic Computer  90  in a Stable Pressure Regulator Chamber  48   a , the top of which is vented through the Pneumatic Computer  90  to outside atmospheric air pressure. A Stable Pressure Regulator Spring  52  is placed on the rear of the Stable Pressure Regulator  48  in the Stable Pressure Regulator Chamber  48   a . The Stable Pressure Regulator Spring  52  may also use an optional Stable Pressure Regulator Spring Guide Spacer  52   g , at  FIG. 2   e, for adjusting its spring tension accordingly.    
      In a preferred embodiment of the current invention the Stable Pressure Regulator  48  provides a consistent stable gas pressure for operation of the internal processes in the Acoustic Generator  0 . This stable gas pressure can be from 25 to 1000 psi, with 70 to 500 psi being better, and 70 to 150 psi being optimum for most of the time. In disassembling the Pneumatic Computer  90 , the Stable Pressure Regulator Shaft  26  along with the Slide Bobbin  24   a  may be removed, as with previous items, by simply grasping the upper portion of the stem and pulling them straight out of the Piston Section  20 . The Stable Pressure Regulator Shaft  26  has two identical exposed O-rings: one spaced near the center  56   b , and the other  56   c  spaced near the front of the Stable Pressure Regulator Shaft  26 .  
      In a preferred embodiment of the current invention the O-ring  56   b  regulates the air from the high pressure source to the Stable Pressure system by sealing off incoming gas pressure when the O-ring  56   b  meets the Stable Pressure Regulator Seat  27 . The O-ring  56   c  located at the front end of the Stable Pressure Regulator Shaft  26  goes into a Stable Pressure Regulator Valve Cylinder  48   c  located underneath the Seat  27 , As shown in FIG.  2   a , the O-rings can be either single or doubled as there is a slight improvement in performance using doubled O-rings. The other end of the Stable Pressure Regulator Valve Cylinder  48   c  is vented through the Pneumatic Computer  90  to the outside atmospheric air pressure. Because of this configuration with the venting of the Stable Pressure Regulator Chamber  48   a  and the Stable Pressure Regulator Valve Cylinder  48   c  the rear and front ends of the Stable Pressure Regulator Shaft  26  are at the same atmospheric pressure. The front and rear ends of the Stable Pressure Regulator Shaft  26  being at the same atmospheric pressure, and isolated from the higher pressures that exist in the Acoustic Generator  0  during its operation, enable the accurate control of the Stable Pressure Regulator Shaft  26  by the Stable Pressure Regulator Spring  52 . In a preferred embodiment of the current invention, this same pressure compensation technique is used on the Piston Nub  29 .  
      In a preferred embodiment of the current invention there is an O-ring  56   a  underneath the Slide Bobbin  38   a  which provides the Stable Pressure Regulator Shaft  26  flexibility in operation by allowing it to self align with its respective seats that are further inside the Piston Section  20 . The Slide Bobbin  24   a  is held in position over this O-ring  56   a  by an E-clip  57   a  around the Stable Pressure Regulator Shaft  26 .  
      In front of the Stable Pressure Regulator Shaft  26  and Slide Bobbin  24   a  in the Stable Pressure Regulator Chamber  48   a  is the Stable Pressure Regulator Seat O-ring  53  which sits on Stable Pressure Regulator Seat  27 .  
      In a preferred embodiment of the current invention the Stable Pressure Regulator  48  works by taking any higher gas pressure from the void or from the Compressed Gas Source  99  and reduces it to the working pressure for the Solenoid  70 , Fire Bobbin  23 , and the Piston Shaft  22 . The Stable Pressure gas system created by the Stable Pressure Regulator  48  can be from 25 to 1000 psi, with 70 to 200 psi being better, and 70 to 150 psi being optimum.  
      As shown in  FIG. 2   a , in one preferred embodiment of the current invention single O-rings can be used for each of the 3 sections on the Stable Pressure Regulator Shaft  26 . However, it is found that when the front section uses two O-rings, as shown in  FIG. 2   a , there is a slight improvement in operation.  
      In a preferred embodiment of the current invention the Stable Pressure Regulator Seat  27  has a Screwdriver Slot  76  for ease of removal and replacement for maintenance.  
      In a preferred embodiment of the current invention some of the components in the Pneumatic Computer  90  are identical. For example, the Slide Bobbins ( 24   a, b , and  c ) in the Differential Regulator  45  and Stable Pressure Regulator  48  are identical, as are O-rings on the shafts of both regulators and as are the O-rings on the Slide Bobbins.  
      Fire Bobbin  
      As shown in  FIG. 5 , moving clockwise on the Pneumatic Computer  90  the next component in a preferred embodiment of the current invention is the Fire Bobbin  23 . In the preferred embodiment of the current invention the Fire Bobbin  23  is a little over an inch long and has 3 sections of O-rings  11 . Although single O-rings can be used for each of the 3 sections on the Fire Bobbin it is found that when the top two sections have two O-rings, as shown in  FIG. 5 , there is a slight improvement in operation.  
      The Fire Bobbin  23  is spring loaded at its rear end by a Fire Bobbin Spring  50  which fits in the center of the Fire Bobbin  23  and protrudes out above the Fire Bobbin  23 . The preferred embodiment of the current invention also permits an optional Fire Bobbin Stable Pressure Regulator Spring Guide Spacer  50   g  at  FIG. 2   f  to be used for adjusting the tension of the Fire Bobbin Spring  50  as needed.  
      On the front end of the Fire Bobbin  23  is a nub that is designed to alStable pressure to pass around it quickly in the arming process. The nub also suspends the Fire Bobbin  23  away from the blunt end of the Fire Bobbin Cylinder  23   c  as an anti-jamming feature. In a preferred embodiment of the current invention the Fire Bobbin  23  can be removed from the Pneumatic Computer  90  using any shaft of appropriate size to dislodge and remove the Fire Bobbin  23 . This is accomplished by inserting the end of the shaft into the hole where the Fire Bobbin Spring  50  was removed and, with a small side pressure to create some resistance, pulling the Fire Bobbin  23  out of the Fire Bobbin Cylinder  23   c.    
      Solenoid  
      In the preferred embodiment of the current invention moving clockwise on the Pneumatic Computer  90  the next component is the Solenoid  70  which is located on the rear end of the Acoustic Generator  0  secured to the Top Section  21 . This Solenoid  70  is used to initiate both the arming and firing of the Acoustic Generator  0 . In a preferred embodiment of the current invention the Solenoid  70  has two positions to control the Acoustic Generator  0 . In the off-position the internal valve in the Solenoid  70  is closed and Acoustic Generator  0  is in the fired/standby mode. In the on-position the internal valve in the Solenoid  70  is open allowing the various gases to enter the Acoustic Generator  0  to switch it to the armed mode. Several benefits arise from this arrangement. One benefit is safety as the Acoustic Generator  0  can only become armed when an electrical signal from an outside source activates the magnetic field in the Solenoid  70  to open the internal valve in the Solenoid  70 . This means that if no electrical signal is sent to the Solenoid  70  the Acoustic Generator  0  will remain in the fired/standby position and the electrical connection is only needed when the Acoustic Generator  0  needs to be armed and fired. As shown in  FIG. 14  there are several potentially hazardous connections to be made in order to set up the Acoustic Generator  0 . Many prior art acoustic generators use the opposite configuration, i.e. the solenoid is to remain on at all times and only turned off to fire the acoustic generator. Other prior art acoustic generators were even more hazardous by requiring the operator to first charge the pressurized chamber and then set up the connections as depicted in  FIG. 14 .  
      As shown in  FIGS. 6   a  to  9   b , when activated the valve in the Solenoid  70  allows the Stable Pressure gas from the Stable Pressure Regulator  48  through the Solenoid Channel  70   c  and Filter Screen  35   a  to the nub end of the Fire Bobbin  23 . Because the rear end of Fire Bobbin  23  is vented to atmospheric pressure in the fired/standby mode the Fire Bobbin  23  is pushed backward which allows Stable Pressure gas from the Stable Pressure Regulator  48  to be directed to exhaust port of the Piston Cylinder  72  and the rear face of the Fire Piston Flange  73  which is pushed forward closing the Fire Tube Valve  84  between the Pressure Chamber  80  and the void as the Piston Shaft O-ring  16  seals inside the Fire Tube  30 . When the Solenoid  70  is closed the gas pressure is released through the solenoid vent, the Fire Bobbin Spring  50  pushes the Fire Bobbin  23  down, which redirects the Stable Pressure gas to the pressure supply port of the Piston Cylinder  72  and the front face of Fire Piston Flange  73  pulling the connected Piston Shaft  22  to the rear and the Piston Shaft O-ring  16  out of the Fire Tube  30  and opening the Pressure Chamber  80  to the void for rapid pressure equalization.  
      As further shown schematically in  FIGS. 6   a  to  9   b , the firing mechanism is the same regardless of the gas pressures that exist in the Pressure Chamber  80 , void, or Compressed Gas Source  99 .  
      The Solenoid  70  can easily be removed by disconnecting the Solenoid Wire  59  and unscrewing the unit while the Top Section  21  is separated from the Piston Section  20 . With the sections separated O-rings  49 ,  67 ,  71   a, b , and  75  can be removed or replaced.  
      Pressure Chamber Area  
      As shown in  FIG. 1 , in a preferred embodiment of the current invention the Pressure Chamber  80  is formed between the Piston Section O-ring  19  and the Fire Tube O-ring  39  sealing against the inside diameter of the Acoustic Generator Housing  1 . As shown in  FIG. 1  the Pressure Chamber  80  also has Support Tubes  40  and the Piston Shaft  22  running through its length from rear to front. The Piston Shaft  22  with its Piston Shaft O-ring  16  forms the Fire Tube Valve  84  and seals the Pressure Chamber  80  from the void when the Piston Shaft  22  is inserted into the Fire Tube  30 . The Support Tubes, which are used as a conduit for the wire components and to provide atmospheric pressure to the inside of the Microphone Unit, as further described herein, have O-rings  43  on both of their ends to seal the Pressure Chamber  80 , and are suspended between the Piston Section  20  and the Fire Tube  30 , which has a flange plate at the rear. In alternative embodiments of the current invention Support Tubes  40  may have Support Tube Sleeves  41  and may be held in position at either end by an E-clip or Anchor Set Screw  42 . The use of Anchor Set Screws  42  at the front end of the Support Tube  40  for securing to the Fire Tube  30  eliminates the need for Support Tube Sleeves  41  and O-rings on the set screw ends.  
      As the Pressure Chamber area is the main portion associated with the firing mechanism of the Acoustic Generator  0 , the following not only describes the various components in the Pressure Chamber area in a preferred embodiment of the current invention, but also describes the firing mechanism of the Acoustic Generator  0 .  
      Firing Mechanism  
      As described in Wolf, a gas pressurized acoustic generator works by isolating a chamber from the wellhead or void, changing the gas pressure in the chamber to be different than the void pressure, and connecting the chamber to the void to equilibrate the pressure difference. The energy released in the gas pressure equalization process generates the sound needed for making the echoes from the borehole.  
      Without being bound by any theory or hypotheses the sharpness, duration, clarity, and intensity of the sound made by a gas pressured acoustic generator are related to the time taken for the gas pressure difference to equilibrate. Essentially, the shorter the time to equilibrate the better the sharpness, duration, clarity, and intensity of the gunshot sound for acoustic sounding purposes. The preferred embodiment of the current invention is designed to use a number of systems to improve time taken for the gas pressure difference to equilibrate.  
      One of the systems used in a preferred embodiment of the current invention is the firing mechanism, which is an actuating system that uses a separate force, other than the force created by the unequal gas pressures, to continue to open the firing valve past the initial moment the unequal gas pressures meet, i.e. past the moment the firing valve is cracked open.  
      By using this actuating system, the current invention does not use nor rely upon the gas pressure difference between the pressure chamber and the void in order to effectuate a quick time to equilibrate. In fact the actuating system is designed not only to be independent of the pressures of the pressure chamber, void and external source but also to reduce the effects of any force created between the pressure chamber and void when firing the Acoustic Generator  0 .  
      Accordingly the actuating system will operate regardless of the pressure chamber, the void, the external gas source, and the pressure difference between the pressure chamber and the void. As a direct outcome of using this actuating system, the current invention removes any effects of the difference in gas pressures on the firing mechanism. As a result the current invention can produce a suitable sound at any pressure within the device&#39;s physical limitations. As the actuating system is not dependent on the pressure difference, the current invention can be used in either explosion or implosion mode. Further the magnitude of the unequal gas pressures can be made very high for deep wells, or very low for an acoustic sounding of the top of a well or for shallow wells.  
      In the preferred embodiment of the current invention the actuating system is driven by the Stable Pressure gas system as defined herein. This is a gas-powered pneumatic system, but it is not the only type of system that can provide the actuating force. The actuating force could be provided by hydraulic, electromechanical, or any other type of mechanism that could provide an actuating force to open the pressure chamber to the void.  
      Further, as shown herein, the independent firing mechanism is just one of the systems used in a preferred embodiment of the current invention to eliminate, reduce or offset the effects that the unequal gas pressure force has on the time taken for the gas pressures to equilibrate. As shown in the Benchmark Test results herein, the interesting and unexpected phenomena of the current invention is that the preferred embodiment of the current invention not only produces an equilibration time shorter than any prior art gas pressurized acoustic generator but also produces a sharper, shorter, clearer, and more intense sound for acoustic soundings than all prior art gas pressurized acoustic generators.  
      Firing Mechanism Components  
      The following describes the components that make the firing mechanism in a preferred embodiment of the current invention.  
      Piston Shaft  
      The Piston Shaft  22  provides the platform for several functions in the pressure chamber setting and firing mechanisms. As shown in  FIG. 2   b  there are alternative embodiments of the Piston Shaft depending on the path for providing void gas to the rear of the Nub Bobbin  29  as described herein. In  FIG. 2   b , Version A of the Piston Shaft  22  is solid and the rear of the Nub Bobbin  29  is set to the void pressure by gas sent through the Pneumatic Computer  90  as described herein. In  FIG. 2   b , Versions B and C of the Piston Shaft  22  show the rear of the Nub Bobbin  29  being set to the void pressure by gas sent through passageways in both the Piston Shaft  22  and the Nub Bobbin  29 . In both versions the Piston Shaft  22  has a filter screen on the front of the channel to prevent material from the void entering the Acoustic Generator  0 . The difference between Versions B and C being the connection between the Piston Shaft  22  and the Nub Bobbin  29  which can be temporary by using a hollow Piston Nub Set Screw  37   s  or permanent by machining the Piston Shaft  22  and Nub Bobbin  29  together as a single unit.  
      Piston Cylinder  
      In a preferred embodiment of the current invention as shown in  FIG. 1   a , the Piston Cylinder  72 , which is a part of the firing mechanism, is at the rear of the Piston Section  20 . As shown in  FIGS. 2 and 3  in a preferred embodiment of the current invention the Piston Cylinder  72  is of a size and diameter so as to utilize an actuating force created by the Stable pressure system created in the Pneumatic Computer  90  in order to drive the Piston Flange  73  and the Piston Shaft  22  forward and backward at a very high rate of speed. In a preferred embodiment of the current invention the Piston Cylinder  72  has an exhaust port and a pressure supply port fed through the Fire Bobbin  23 . In a preferred embodiment of the current invention the Piston Cylinder  72  cavity can be from 0.5″ to 1.5″ in diameter and 0.2″ to 1.5″ in depth with a 0.850″ diameter by 0.850″ depth working well and a 1.0″ diameter by 0.750″ depth working the best.  
      Piston Shaft  
      In a preferred embodiment of the current invention as shown in  FIG. 1 , with the Top Section  21  and the Piston Section  20  separated the Piston Shaft  22 , which has a Piston Flange  73  and Piston Valve  12 , may be removed by pushing the Piston Shaft  22  up through the Piston Section  20  to exit the rear of the Piston Section  20 .  
      Piston Flange  
      In a preferred embodiment of the current invention the Piston Flange  73 , which sealed against Piston Cylinder  72  wall by an O-ring  73   a  is moved by the differences and changes in gas pressure on either side of the Piston Flange  73 . The changes in the gas pressure on either side of the Piston Flange  73  in turn moves Piston Shaft  22  between the fired/standby and armed positions. In the fired/standby position the Piston Flange  73  is to the rear of the Piston Cylinder  72  as the result of a higher gas pressure being applied to the front face of the Piston Flange  73 . As described herein by moving to the armed position the pressures on the exhaust and pressure supply channels to the Piston Cylinder  72  are reversed, with the higher gas pressure on the rear face of the Piston Flange. This moves the Piston Flange and Piston Shaft forward closing the Fire Tube Valve  84  isolating the Pressure Chamber  80  from the void and enabling the Pressure Chamber  80  to be charged to the appropriate pressure via the Piston Valve  12  which is now open to the Differential Regulator  45 . The forces on the Piston Flange  73  provide a power stroke when pushing the Piston Shaft  22  forward to close the Fire Tube Valve  84  and a speed stroke when moving the Piston Shaft  22  back to release the pressure wave created between the Pressure Chamber  80  and the void. The size and diameter of the entrance and exit passages directly relates to the power and speed strokes. A small diameter is used to create a back pressure brake for the power stroke and a larger diameter passage is used for the speed stroke. This prevents damage to the internal parts and alleviates any unwanted sounds from metal contact.  
      As further described herein, in a preferred embodiment of the current invention the void pressure that might affect the operation and firing of the Acoustic Generator  0  is offset against itself by utilizing the Nub Bobbin  29  which sits behind the Piston Flange  73  in the Pneumatic Computer  90  as described herein. The nub gas pressure comes directly from the void pressure to equalize and compensate for the void pressure entering the front of the Acoustic Generator  0  and pressuring the front of the Piston Shaft  22 . This compensation or equalizing allows the Piston Shaft  22  to be operated with the separate Stable Pressure gas system as described herein.  
      Piston Valve  
      As shown in  FIG. 2  and  5 , in a preferred embodiment of the current invention there is a Piston Valve  12  on the Piston Shaft  22 . The Piston Valve  12  is the link between the firing mechanism and chamber pressure setting mechanism in the Acoustic Generator  0 . The function of the Piston Valve  12  is to open the Pressure Chamber  80  to the Differential Regulator  45  in order for the Pressure Chamber  80  to be automatically set to the appropriate pressure for firing. In a preferred embodiment of the current invention the Piston Valve  12  is formed by a curved indent completely around a portion of the Piston Shaft  22 .  
      In a preferred embodiment of the current invention when moving from the fired/standby position to the armed position the Piston Shaft  22  moves forward and closes the Fire Tube Valve  84  resulting in the Pressure Chamber  80  being isolated from the void. After the Fire Tube Valve  84  closes the Piston Shaft  22  continues to move forward opening the Piston Valve  12 . The opening of the Piston Valve  12  allows gas to flow past the Piston Section O-ring  17   a  to gaseously link the void-isolated Pressure Chamber  80  to the Differential Regulator  45 . As described herein the Differential Regulator  45  performs either one of two functions in setting the pressure of the Pressure Chamber  80 . In the implosion mode, excess gas will follow from the Pressure Chamber  80  through the Differential Regulator  45  to the appropriate lower pressure as determined by the mechanisms of the Differential Regulator  45  as explained herein. In the explosion mode, gas from the Compressed Gas Source  99  will follow to the Pressure Chamber  80  via the Differential Regulator  45  as explained herein.  
      In a preferred embodiment of the current invention the indent of Piston Valve  12  allows required gas to flow either in or out, depending on the mode of firing, around and past the O-ring  17   a  to fill or empty the Pressure Chamber  80 . When the Piston Shaft  22  is pulled backward, i.e. to fire the gun and return to the fired/standby position, the shaft portion without the indent, seals against the Piston Section O-ring  17   a  and the Piston Valve  12  is closed.  
      In a preferred embodiment of the current invention the radius of the cut for the Piston Valve  12  can be from 0.1″ to 0.4″; we have found 0.25″ to work well with 0.261″ being best. The depth of this machine cut radius can be from 0.01″ to 0.5″; it has been found that 0.350″ to works well and 0.339″ to works the best. In a preferred embodiment of the current invention the Piston Valve  12  curve completely encompasses the Piston Shaft  22  in order to disperse the gas uniformly, to reduce turbulence, and to prevent any tendency to lift out of place or pit the Piston Section O-ring  17   a.    
      Fire Tube Valve  
      As shown in  FIG. 1 , in a preferred embodiment of the current invention the Fire Tube Valve  84  is inside the rear of the Fire Tube  30  and is formed when the Piston Shaft O-ring  16  at the front of the Piston Shaft  22  seals inside the rear of the Fire Tube  30 . In a preferred embodiment of the current invention the Piston Shaft  22 , with Piston Shaft O-ring  16 , is propelled forward by the Piston Flange  73  so as to insert the front end, approximately ¼ inch in a preferred embodiment of the current invention, into the Fire Tube  30  center shaft hole at the flange end completely sealing off and isolating the Pressure Chamber  80  from the void. When the Piston Flange  73  is propelled backward the Piston Shaft  22  and Piston Shaft O-ring  16  are extracted from the Fire Tube  30  and the valve is opened. As described herein in the explosion mode the Pressure Chamber  80  is charged with pressurized gas from an outside gas source, the Fire Piston Flange  73  is fired, pulling the Piston Shaft  22  and the Piston Shaft O-ring  16  out of the Fire Tube  30  opening the Fire Tube Valve  84  and expelling the pressured gas charge into the void. As described herein in for the implosion mode the Pressure Chamber  80  is set to a pressure lower than the void, the Fire Piston Flange  73  is fired, pulling the Piston Shaft  22  and the Piston Shaft O-ring  16  out of the Fire Tube  30  instantly opening the Fire Tube Valve  84  and allowing the higher pressure void gas to fill the Pressure Chamber  80 .  
      The firing mechanism operation is shown in  FIGS. 6   a  to  9   b . The figures show the various components, channels, passageways, and gas pressures at the fired/standby and armed positions for both the explosion and implosion mode in two alternative embodiments of the current invention. There are differences in position of various components in the explosion and implosion mode due to the Pressure Chamber  80  pressure setting mechanism. But the firing mechanism for both modes is the same and is not influenced by the pressures in the Pressure Chamber  80 , Compressed Gas Source  99 , void, or any part of the Pressure Chamber  80  pressure setting mechanism.  
      In a preferred embodiment of the current invention the time of the firing mechanism to be set from the fired/standby to armed position is determined by an electrical supply that is sent through the Data Cable  61  to the actuating side of the Solenoid  70 . This electrical supply opens the internal valve in the Solenoid  70 . In a preferred embodiment of the current invention the electrical supply is left on for ½ to 5 seconds duration, with 2 seconds being optimum. During this time the Stable Pressure gas from Stable Pressure Regulator  48  then travels through the Solenoid  70  and into the Pneumatic Computer  90  to apply pressure to the actuating end of the Fire Bobbin  23  which in turn compresses the Fire Bobbin Spring  50  located inside the opposite end of the Fire Bobbin  23 . The movement of the Fire Bobbin  23  reverses the exhaust and pressure supply ports which are applied to the rear and front of the Piston Cylinder  72  respectively, the exhaust port being increased from atmospheric to the Stable pressure, the pressure supply port being decreased from the Stable pressure to atmospheric. This pressure difference moves the Piston Flange  73  with its Piston Shaft  22  forward to seal off the Pressure Chamber  80  from the void by utilizing the Piston Shaft O-ring  16  seated inside the rear end of the Fire Tube  30  creating the High Pressure Fire Valve  84 . When the Fire Valve  84  closes the Piston Valve  12  opens and the Pressure Chamber  80  is then set to the appropriate pressure as determined by the Pneumatic Computer  90  as described herein.  
      In a preferred embodiment of the current invention when the electrical supply is shut off to the Solenoid  70  the pressure supply to the passageway for the actuating end of the Fire Bobbin  23  vents to atmospheric pressure. The compressed Fire Bobbin Spring  50  pushes the Fire Bobbin  23  forward which in turn reverses the pressures in the exhaust and the pressure supply ports of the Piston Cylinder  72 , the exhaust port returns to atmospheric pressure and the pressure supply port is increased from atmospheric pressure to the Stable pressure. This change in pressure moves to the Piston Flange  73  back to its original fired/standby position pulling the Piston Shaft  22  with the Piston Shaft O-ring  16  out of the Fire Tube  30  to close the Piston Valve  12  and open the Fire Valve  84  thus enabling the pressure difference between the Pressure Chamber  80  and the void to equilibrate. In a preferred embodiment of the current invention the complete cycle time is just over 2 seconds.  
      Microphone Cavity Area  
      In a preferred embodiment of the current invention the Microphone Cavity area at the front of the Acoustic Generator  0  contains the Fire Tube  30  which sends the sound into the void, and the Microphone unit ( 32 ,  33 , and  34 ) which receives echoes from the well and sends the appropriate electrical signal to the Surveyor Unit  100 .  
      As mentioned before in a preferred embodiment of the current invention there are systems used to eliminate, reduce or offset the effects that the unequal gas pressure force has on the time taken for the gas pressures to equilibrate. This includes the portal structure design and the design of the components in the Microphone Cavity area which are made for the efficient and effective firing of sound and the accurate recording of the echoes generated.  
      Fire Tube  
      As shown in  FIG. 1  in a preferred embodiment of the current invention the Fire Tube  30  is set in its position against the Housing  1  at the front of the Pressure Chamber area and is sealed from the void by the Fire Tube O-ring  39 . The rear flange plate of the Fire Tube  30  and the Housing  1  form the front wall of the Pressure Chamber  80 . As shown in  FIG. 2  in a preferred embodiment of the current invention the rear flange plate of the Fire Tube  30  also secures the Support Tubes  40 .  
      Without being bound by any theory or hypotheses due to the design of the Acoustic Generator  0  in a preferred embodiment of the current invention the barrel or portal of the Fire Tube  30  has a number of features which shorten the time taken for the gas pressure difference to equilibrate.  
      First, in a preferred embodiment of the current invention the diameter of the barrel or portal of the Fire Tube  30  is as large enough so as to shorten the time to equilibrate and yet not too large so as to create unwanted or excess turbulence. In a preferred embodiment of the current invention the opening has an area of 0.1 to 2.5 square inches.  
      Second, in a preferred embodiment of the current invention the portal of the Fire Tube  30  is in the center of the front face of the Pressure Chamber  80 . In a preferred embodiment of the current invention the front face of the Pressure Chamber  80  is symmetrical with the Fire Tube  30  in the center to ensure a symmetrical release of the gases when the Acoustic Generator  0  is fired.  
      Third, in a preferred embodiment of the current invention barrel of the Fire Tube  30  is a hollow cylinder which provides a straight shot of the sound wave into the void. In a preferred embodiment of the current invention when the Piston Shaft  22  is pulled back to fire the Acoustic Generator  0  the sound generated is directly channeled by the barrel of the Fire Tube  30  into the void.  
      Another option for a preferred embodiment of the current invention is for the barrel of the Fire Tube  30  to be rifled, i.e. to have cut or machined in any number if spiral grooves to the inside surface.  
      Microphone Unit and Wave Guide  
      As shown in  FIG. 2  and  3   c , in a preferred embodiment of the current invention the Microphone unit ( 32 ,  33 , and  34 ) is a hollow cylindrical design that is fits over the barrel of the Fire Tube  30  and is secured into place with the Wave Guide Nut  31  screwed on to the front end of the Fire Tube  30 . The Wave Guide Nut  31  is further locked down from unscrewing with a Set Screw  36 . As shown in  FIG. 2 , in a preferred embodiment of the current invention the Microphone Element  34  is parallel to the barrel of the Fire Tube  30  and perpendicular to the front of the barrel. The Wave Guide Nut  31  has a symmetrical bevel on the front so as to correspond and be parallel to the angle of the internal symmetrical bevel of the Housing  1 . The Wave Guide Nut  31  is larger in diameter than the outside surface of the Microphone Element  34 . This design allows any incoming pressure waves that might affect the signals from the Microphone unit to be deflected around the Wave Guide Nut  31  into the main part of the Microphone Cavity  46  area as they ricochet against the rear flat side of the Wave Guide Nut  31 . This design permits the Microphone Unit to be extremely sensitive in order to enhance and improve the quality of the echoes detected. In a preferred embodiment of the current invention the bevel of the Wave Guide Nut  31  can be 20 to 45 degrees, depending on other internal characteristics of the Acoustic Generator  0  and microphone. Thirty degrees works well but twenty-five degrees works the best for acoustic sounding purposes.  
      In a preferred embodiment of the current invention the Microphone unit itself consists of a Microphone Element  34  made of a cylindrical Ceramic Piezo material which is suspended between the Microphone Holder  32  and the Microphone Cap  33  with Microphone O-rings  86  on the ends and inside diameter. There are alternative embodiments for the Microphone Element  34 . As shown in  FIGS. 2   g  and  2   h  one embodiment has two separate oppositely charged conductive coatings on the inside of the Microphone Element  34  with the outer surface having a neutral coating. A Lead Wire,  58   a  and  58   b , is connected to each of the conductive coatings on the inside.  
      As shown in  FIG. 3   c  in another embodiment the Microphone Element  34  has two separate oppositely charged conductive coatings, one on the outside and the other on the inside with both Lead Wires  58   a  and  58   b  being connected to the inside coating through a Zener Diode  87  and a Resistor  88  respectively.  
      For either embodiment of the Microphone Element  34  described the Lead Wires,  58   a  and  58   b , run through a Support Tube  40  to the Data Channel  61  as shown in  FIG. 1 . The Microphone unit ( 32 ,  33  and  34 ) is assembled with specific torque specifications for resonant frequency response and sufficient sensitivity. The cavity made in the Microphone unit by its three components is air-tight but is constantly at the atmospheric pressure due to the air passageway through the Support Tube to the rear of Acoustic Generator  0 . Maintaining atmospheric pressure in the cavity of the Microphone unit maintains the quality of the echoes received regardless of the void gas pressure.  
      Surveyor Unit  
      The following is a description of the components and operation of the Surveyor Unit  100 .  
      Components and Operations of the Surveyor Unit  
      As shown in  FIGS. 10 and 11 , the following describes the components and operations of the Surveyor Unit  100  in a preferred embodiment of the current invention.  
      As shown in  FIG. 10 , in a preferred embodiment of the current invention there are two input signals and one output signal from the Surveyor Unit  100  to the Acoustic Generator  0 . The analog signals from the Pressure Transducer  77  are digitalized by an A/D Converter  134  for processing by the Surveyor Unit CPU  140 . The analog signal from the Microphone  34  is sent to a Preamp  130  and two Gain Stages  136  and  138  for input to the CPU  140  where it is digitalized by the A/D converter inside the CPU  140 . There are two gain stages to maximize the signal and minimize gain errors although more could be used if needed. The CPU  140  also controls the Solenoid  70  by using a Solenoid Driver  132 .  
      The CPU has two additional outputs, an Interface  150  to the Compact Printer  112  component of the Surveyor Unit  100 , and a USB Interface  154 , shown as the USB Port  115  in  FIG. 13 , to connect the Surveyor Unit  100  to a computer for further analysis of the data stored in the Surveyor Unit  100 .  
      There are two types of memory. Flash memory  144  is used for storing long term data such as settings and shot files. Data in a flash memory is not lost when power is removed. Ram memory  142  is used for temporary storage and data is lost when power is removed.  
      The Encoders  164  are rotary encoders and their function is similar to potentiometers. They are used when a user turns a knob. A digital signal is sent to the I/O Processor CPU  140  to input settings such as velocity and well depth into the Surveyor  100 .  
      There are various parameters and functions performed by the I/O Processor CPU  140  which are shown in  FIG. 11  and saved in a Surveyor shot file. These functions are: 
      Well pressure     Changeover depth     Well depth     Acoustic velocity     Decay rate     Peak averaging time     Threshold multiplier     Autostart setting     Filter frequencies     Preamp gain     Minimum gain     Maximum gain     Start gain knob setting     End gain knob setting    

      The filters used in the Surveyor Unit  100  are digital filters. The “top” filters filter sound collected from the start of the shot until the changeover depth is reached. The “bottom” filters are used the rest of the time. Digital filters are implemented by multiplying the current and previous sound readings by a set of stored coefficients. The output of the filter is the sum of the products. Frequencies, “sharpness” and stop band attenuation are determined by the coefficients used and can be changed by software at any time. The calculations are performed by the CPU so no additional components are needed.  
      The actual gain of the amplifiers is determined by the knob settings and the minimum and maximum gain settings. The amplifier gain with a knob setting of 1 is equal to the minimum gain setting and the gain at a knob setting of 10 equals the maximum gain. Minimum and maximum gains will be set when the Surveyor is initially setup and probably will not be changed by the user.  
      The fluid hit algorithm is a set of steps taken by the Signal Processor to find the reflection from the fluid surface. The background sound during the shot is filtered and a threshold is determined. The threshold is found by first tracking the instantaneous peak sound amplitude. Between peaks, this amplitude is “bled away” by the decay rate. The threshold is the average of previous peaks multiplied by the threshold multiplier. The characteristics of the threshold can be changed to work in a particular well by changing the decay rate, averaging time, and threshold multiplier.  
      Last, each sound sample is compared to the current threshold. When the sound amplitude reaches the threshold in a negative direction, the fluid reflection has been found.  
      The depth calculation performed by the Surveyor is the following:
 
Depth=Time to hit×(Velocity/2)
 
 Operating of the Surveyor Unit 
 
      As shown in  FIG. 10 , in a preferred embodiment of the current invention the Surveyor Unit  100  is in a protective case of approximately 7×8×5.5 inches. After opening the Latch  125  and lifting the Lid  121  of the Surveyor Unit  100 , various colored knob controls will be available for usage. The Compact Printer  112  is located above the top of the Face Panel  104  and is electronically connected through an Interface  150 , which is shown in  FIG. 13  as the Panel Mount Jack  102 . Additional optional functions can be supported through additional plugs next to the Panel Mount Jack  102 .  
      In a preferred embodiment of the current invention the Compact Printer  112  uses a frequency-controlled step-motor for a consistent, exact, and reproducible printer speed. The strip chart produced by the Compact Printer  112  shows time in seconds at the top of the tape along the edge to the bottom of the printed tape and likewise measurements in inches on the opposite edge with the zero for both being set at the face wave of the shot. As shown in  FIG. 13 , in the upper left hand corner of the Face Panel  104  there are plugs for the 12V PowerJack  112 , the USB Port  115 , and the Printer Port  113 . In the bottom left corner of the Face Plate  104  moving from left to right are control knobs and the fire button.  
      As shown in  FIG. 10 , in a preferred embodiment of the current invention the first knob on the left is the Acoustic Velocity Knob  105 , and is used to adjust the Acoustic Velocity measurement in feet per second. The Acoustic Velocity Knob  105 , like several other knobs in the Surveyor Unit  100 , has two height positions, up and down, with the up position being the default. In the up position the Acoustic Velocity Knob  105  is used to finely adjust the acoustic velocity setting by feet per second units. In the down position the Acoustic Velocity Knob  105  will make large adjustments to the acoustic velocity setting by one hundred feet per second units.  
      Moving to the right in  FIG. 10 , the next knob shown is the Depth/Changeover Knob  106 . In a preferred embodiment of the current invention the Depth/Changeover Knob  106  has three functions, in the default up position it changes the void or well depth distance, clockwise to increase and counter-clockwise to decrease in increments of 100 feet. In the down position the Depth/Changeover Knob  106  alters the frequency changeover depth, clockwise to increase and counter-clockwise to decrease. The third function of the Depth/Changeover Knob  106  occurs when it is used in conjunction with the Off/On Gain Knob  107  to enter desired numerical values into the Surveyor Unit  100  from the menu selection which is displayed on the Digital Readout Display  103 .  
      Moving to the right in  FIG. 10 , the Off/on Gain Knob  107  is the next knob and is commonly called the menu knob. In a preferred embodiment of the current invention the menu functions are shown in Table 3:  
               TABLE 3                          Off/On Gain Knob Menu for Surveyor Unit       Menu Function                             No. of Knob                   pushes   Mode   Default   Start/Stop               0   Off-On   Off   Off = Turn Right                   On = Turn Left           Ending Gain   Default   Turn Right or Left               Setting       1   Beginning Gain   Default   Depress and Turn Right or               Setting   Left       2   Setup Code   Default   Start = Fire               Setting   Stop = Tap Once       3   Auto-Fire Clock   Zero   Start = Fire                   Stop = Tap 3 Times       4   Pressure Transducer   Zero   Stop = Automatic           Zero Set                  
 
      In a preferred embodiment of the current invention the Off/On Gain Knob  107  is also used as the off-on switch by turning to the right in the standard height position for “on” and left in the standard position for “off”. The selected menu function is displayed on the Display Window  103  and the Depth/Changeover Knob  106  is used to enter the numerical values into the electronic programming of the Surveyor Unit  100 . When using the Depth/Changeover Knob  106  in this mode, single digit units are selected in the up position and turning the Selector Knob  106  to the left or right to the desired number. The down position will change the values by multiples of tens or hundreds as appropriate.  
      Moving to the right in  FIG. 10 , in a preferred embodiment of the current invention the knob to the right of the Off/On Gain Knob  107  is the Fire Button  108 . This is a momentary contact push button used to arm and then fire the Acoustic Generator  0 . At a desired time after all numeric entries have been made into the Surveyor Unit  100  the Fire Button  108  is pressed and released initiating an electronic signal. This will immediately set all surveyor data entries and initiate the firing cycle. In a preferred embodiment of the current invention an electronic pulse travels through the Data Cable  61  to the Acoustic Generator  0  to automatically trigger the Solenoid  70  for two seconds for arming and then releases the Solenoid  70  to fire the Acoustic Generator  0  as explained herein. As also explained herein, the Fire Button is also used as a safety button for pressure bleed-off. When the Well Depth is set to “000” the Fire Button can be pressed to open the Solenoid  70  to relieve all excess pressures prior to Acoustic Generator  0  disconnection from a well.  
      In a preferred embodiment of the current invention as shown in  FIG. 13 , there are three smaller knobs in a triangular pattern in the upper right corner of the Face Panel  104 . These knobs are used as an alternate method to calculate and adjust the acoustic velocity reading. Starting on the top above the Fire Button  108  and slightly to the right is the Measured Segment Knob  109 . It is used for entering the number of inches measured on the printout tape which correlate to ten pipe collars or any other known distance measurement in the well. In a preferred embodiment of the current invention the default setting for the Measured Segment Knob  109  is set to a distance that represents ten normal collars, 2.123 inches. The next small knob to the right is the Feet in Segment Knob  110  which is used to enter the average number of feet for ten lengths of well tubing in the well being measured. In a preferred embodiment of the current invention the default setting for the Feet in Segment Knob  110  is 317.5 feet. The third knob is the Inches to Fluid Knob  111 . It is straight below the Feet in Segment Knob  110 . This Inches to Fluid Knob  111  is used to enter the total number of inches on the printout tape from the start of the shot fired to the fluid hit. When these values are entered into the Surveyor Unit  100  the fluid level is recalculated and shown on the Digital Readout Display  103 . In a preferred embodiment of the current invention the default setting for the Inches to Fluid Knob  111  is 22.34 inches which correlates with our standard demo shot. While this example is using 10 collar lengths to determine the overall acoustic velocity of the well, a much greater known distance to an anomaly deep in the well is preferred as it will give greater accuracy for the entire distance. The three knobs  109 ,  110  and  111  are used as a manual method for calculating acoustic velocity and fluid levels from the Surveyor Unit  100 .  
      In a preferred embodiment of the current invention the Compact Printer  112  will print a continuous line readout of the well shot feedback information as a positive bump or negative dip off of the centerline which when interpreted will show pipe collars, fluid level, and other well anomalies. This readout will have various control settings printed on the first portion of each shot tape prior to the shot feedback information.  
      In a preferred embodiment of the current invention the top lid of the protective case has a metal Hold-down Bracket  116  to restrain the Compact Printer  112  from unwanted movement while the Surveyor Unit  100  is being transported and to provide a storage place for digital calipers, the data cord, and the unit&#39;s instruction card.  
      Explosion and Implosion mode  
      In a preferred embodiment of the current invention the Acoustic Generator  0  will automatically determine the explosion or implosion mode through the Differential Regulator  45  by detecting the difference in pressure from the void compared to the external gas source. The greater of the two pressures will shift the Differential Regulator  45  forward or backward which in turn changes the pressure passages accordingly. The Surveyor arms and fires the Acoustic Generator  0  exactly the same for both the explosion and implosion modes.  
      Setting Shot Properties Manually  
      In a preferred embodiment of the current invention the properties and settings can be manually altered for specific desired results using one or more of the three larger knobs,  105 , 106 , and  107 . Typically the void or well depth is set first using the Depth/Changeover Knob  106  in the up position. Then the frequency crossover depth is set by using the same knob, pushing it down, and turning it right or left as desired, although this is not necessary as the default changeover will automatically be adjusted to one half of the entered well depth. Following this the beginning and ending gain settings can be changed using the Off/On Gain Knob  107 ; the ending gain in the up position and the beginning gain in the pushed down position. If the acoustic velocity is known it can be entered at any time prior to initiating the fire sequence, by turning the Acoustic Velocity Knob  105  right or left in the up position to achieve the desired result. Tapping any of these knobs once will display its current setting.  
      Using Set-Up Code Option  
      In a preferred embodiment of the current invention specific settings for any individual well or void can be entered as the default settings. This is done by pressing the Off/On Gain Knob  107  twice and then using the Depth/Changeover knob  106  to enter the numeric setup code. These new default settings will remain in the Surveyor Unit  100  until cleared by setting a new set-up code, by turning off the power, or by manual adjustment of Knobs  105 ,  106 , or  107 . When the power is turned back on, the original set-up codes will revert as the default codes.  
      Changeover  
      In a preferred embodiment of the current invention the changeover depth is the depth in feet where high frequency for readings in the upper portion of the well changes to a lower frequency for readings from the lower portion of the well. As explained herein, higher frequencies of 40 Hz to 100 Hz are normally used to measure the reflections from the collars. The measurement of the echoes from the collars is used to calibrate the echoes from the well as the distance between the collars is known. The lower frequency of 1 to 40 HZ is normally used to detect the fluid hit; i.e. the fluid level present in the well. However these frequency ranges may not be applicable for every well and so the frequencies being detected may need to be altered or adjusted accordingly.  
      In the Surveyor Unit  100  the results to be analyzed have a changeover point, at the place where the higher frequency detection changes over to the lower frequency detection. In a preferred embodiment of the current invention the Surveyor Unit  100  can change the changeover by using the Depth/Changeover Knob  106  when depressed and turned right or left as desired.  
      Setting Automated Firing Timer  
      In a preferred embodiment of the current invention the automated shot timer can be set by pressing the Off/On Gain Knob  107  three times. The Digital Readout Display  103  will show Hr 0.00. This represents the amount of time from one automatic firing to the next automatic firing. It can be set at regular intervals from 1 minute apart up to 24 hours apart in most cases. In other cases, depending on the nature of a well, an operator may want to set an irregular specific automatic firing time sequence to observe an unusual phenomena exhibited by the well.  
      Regardless of the regularity or irregularity of the firing time sequence, setting the Automated Firing Timer is accomplished with the Depth/Changeover Knob  106 ; in the up position, turning right or left will dial in the amount of minutes and in the depressed position, turning right or left will dial in the hours. After the desired time has been set, one press of the Fire Button  108  will start the sequence of automatic firing, or to cancel the automatic firing sequence tap three times on the Off/On Gain Knob  107  to revert to the default settings.  
      Well Depth Setting  
      In a preferred embodiment of the current invention the well depth is set using the Depth/Changeover knob  106  in the up position. Turning this knob right or left will dial in the desired well depth in 100 foot increments. Typically in the preferred embodiment of the current invention the well depth is set at or below the known well depth.  
      Acoustic Velocity  
      In a preferred embodiment of the current invention the default acoustic velocity is set at 1220 ft per second. Any known acoustic velocity can be entered by turning the Acoustic Velocity Knob  105  right or left in the up position for single units and depressed for hundreds of units to the desired amount.  
      Confirming Fluid Level  
      In a preferred embodiment of the current invention the fluid level depth will show on the Digital Readout Display  103  as the distance in feet from the top of the well to the fluid level at the conclusion of any shot fired. It is automatically calculated and determined through the internal computer electronics and is not subject to any direct manipulation or control externally other then recalculations from adjusted parameters. If no fluid level is determined from the internal electronics the Digital Readout Display  103  will read all  8   s.    
      Automated Marker Finder and the Corrected Acoustic Velocity Calculator  
      When shooting a well to ascertain the level of the fluid standing within the well, it is common practice to find a length of time encompassing a known distance. This length is extrapolated to the point where the fluid level is observed, while counting this number of lengths or segments and multiplying by the known length of the segment. This segment length is usually near the top of the well, where pipe collars of a known length are most visible.  
      This method does not account for the variations in Acoustic Velocity which occur when gas within the well settles into layers, often having differing Specific Gravity and therefore widely varying Acoustic Velocities. To get more accurate estimations of fluid levels, some professionals try to find the location of a known feature of the well which is close to the fluid level and measure the shorter distance from this feature to the fluid. These known features are commonly referred to as “Markers”. These Markers may be valves, anchors, casing liners and other objects within the well, or larger collars or other objects placed along the tubing or casing string for the purpose of generating an acoustic anomaly or a Marker anomaly.  
      In a preferred embodiment of the current invention, Marker anomalies are found automatically by the Surveyor Unit  100  much in the same manor as the automatic fluid level is determined described above with some variations. First, the Marker anomaly for which the program is searching is often a solid object, which will create an upward spike on the readout display, instead of the downward spike usually indicating the fluid level hit. Second, an upward spike anomaly is usually expected to be found within a narrow range, and this range may be set to about one second, or less of the shot recording to search only in this narrow range and ignore other similar anomalies. In a preferred embodiment of the current invention the range is set in the Surveyor Unit  100 . Another unique feature of this search is that its&#39; frequency may be set to one that best singles out the Marker anomaly. This unique frequency/filter applies only during the narrow range selected for this search. In a preferred embodiment of the current invention the range and threshold amplitude for the Marker anomalies are set in the Surveyor Unit  100 .  
      When the Marker anomaly is detected by the Surveyor Unit  100  it calculates the precise time from the beginning of the shot to the detection of the Marker anomaly, and use this time and known distance to ascertain an Acoustic Velocity which is calculated over as much of the well depth as possible for superior accuracy over previous methods which rely on the length of a few collars near the surface of the well.  
      About one tenth of a second prior to every automatic fluid level calculation, the Acoustic Velocity is determined and applied to the Acoustic Velocity calculation used for the current fluid level determination for maximum accuracy. Since many wells already have noticeable features which may be used as known Markers, this becomes very practical in many wells, and therefore is part of the standard Set-up Code criteria to be applied to each unique well situation by our instruments.  
      Viewing the Well Background Sounds  
      In a preferred embodiment of the current invention the well background noise can be seen directly in real time on the Surveyor Unit  100  from the Compact Printer  112  by pressing once and holding down the Off/On Gain Knob  107  until the desired amount of tape has been released for review from the Compact Printer  112 . This viewing will show any noise originating from the well itself.  
      Benchmarking the Invention  
      The main goal of any acoustic generator is to generate a sound that enables the microphone in the gun, or a separate transducer, to detect a clear range of echoes from the entire borehole. For the acoustic sounding method the sound to be generated by the gun should be similar to that of a gunshot, i.e. a sharp short loud bang. This is oversimplifying the situation, but the phrase “loud sharp short bang” is useful because it relates to the three measurable qualities of the sound&#39;s effectiveness in the acoustic sounding method: intensity (loud), the face angle (sharp), and the elapsed time (short). In addition to these criteria there is a fourth factor in determining the effectiveness of the sound generated for the acoustic sounding method: interference. Interference is a fourth measurement of a sound&#39;s effectiveness in the acoustic sounding method because it takes into consideration the effects that any interfering secondary sounds may have with the primary sound wave generated by the acoustic sounding equipment.  
      Intensity  
      Intensity is the initial power release rated in decibels (dB) which are easily measured with readily available electronic instruments and programs, such as a pressure transducer calibrated in a linear scale converted to millivolts and sent to a digital readout. But decibels are not an empirical measurement unit as the decibel value depends on the agreed upon reference. The decibel scale is a base 10 logarithmic scale, so from any given starting point it takes 10 times an increase in sound power to increase the dB readings by 10. As an example to increase 150 dBs to 160 dBs it takes 10 times greater power needed then at 150 dBs. To the average person a 10 dB increase in sound level is perceived as a doubling in loudness.  
      So although intensity is rated in decibels, intensity is related to pressure amplitude. Pressure amplitude being a measure of the size of the variation in air pressure caused by a sound wave. In particular, the energy in a sound wave is proportional to the square of the pressure amplitude. As an example, if the pressure amplitude of a sound wave is doubled then the energy carried by that wave is quadrupled. In pure silence there is a constant pressure—atmospheric pressure. It is fairly simple to understand how a calibrated measurement of the pressure amplitude can be made using a microphone to convert the pressure variations into an electrical signal. By applying known pressure variations to the microphone the electrical signal can be calibrated to directly measure the air pressure variations. With suitable processing this pressure variation can be converted into the pressure amplitude. This function is performed by Sound Pressure Level (SPL) meters.  
      Elapsed Time  
      The second is elapsed time. This equates to the exact amount of time measured in milliseconds from the first recordable pressure wave created by this rapid equalization to the end of any equalization activity which will create distortion in the echo return. The end of the equalization activity being defined as the point when the amplitude drops back to 0 db and does not produce a secondary wave afterwards, i.e. does not produce a subsequent positive reading of 155 dB or more.  
      Face Angle  
      The third factor determining the effectiveness of a sound wave intended for acoustic sounding purposes is the flatness of the front wave face. For the purposes of benchmarking, this is measured from the graph results as being the angle of the front wave face as compared to a horizontal line in sync with the base line of the wave trace.  
      Secondary Wave  
      The fourth factor to be determined is the clarity of the sound. The presence or absence of a secondary wave being an indicator of the clarity of the sound. To be effective the primary sound wave, i.e. the largest sound wave generated by the acoustic generator when fired must not encounter interference created by a secondary wave or a ripple in the primary or first wave. For the purposes of benchmarking, a secondary wave is defined as a second positive reading of 155 dB or more produced from the acoustic generator during the initial firing of the generator for at least one-half of the firings at the particular setting. A ripple is defined as a sharp dip or fall off in the front face of the first primary wave so as to separate the front face into two or more angles (see Sonolog  FIGS. 19, 20 , and  21 ).  
      Test Methodology  
      A preferred embodiment of the current invention was tested with two commercially available pressurized chamber acoustic generators, the SONOLOG D-6C2 from Keystone Development Corporation as described in Wolf and the COMPACT GAS GENERATOR from the Echometer Corporation. Each of the three generators was attached to a one meter long, two inch diameter stationary pipe with a threaded end at one end for attaching the generator. The generators were fired at room temperature using an external gas pressure source in the explosion mode and the sounds emitted from the generators were detected at the other end of the pipe by a Honeywell 30 psig microphone. The microphone output being sent to a computer programmed with a standard audio signal analysis program with the results being plotted on a graph such as the one shown in  FIG. 15  with time (in seconds) on the x-axis and the decibel (dB) logarithmic scale for the y-axis.  
      In the oil industry the acoustic sounding method uses very low audio to sub-audio sound wave frequencies. These sound frequencies can range from 100 Hz to 1 Hz, with a range of 80 Hz to 10 Hz being the norm. The different frequencies within these ranges are used to detect different attributes in the well, for example, collars are usually detected at the 80 Hz to 40 Hz range, whereas the fluid level is detected in the 30 Hz to 1 Hz range. Accordingly the results from the microphone were detected at 10, 20, 40 and 70 Hz for each firing to determine the sound generated by each generator at each frequency.  
      Further for the purposes of benchmarking the different generators, the generators were fired with their pressure chambers set at 150 psi and 100 psi to determine any change in performance at these different pressures and each generator was fired at least ten (10) times at each pressure setting for statistical accuracy.  
      Benchmark Results  
       FIGS. 15 through 26  show the results produce at 10, 20, 40 and 70 Hz from firing of each generator. The following are the benchmark results for the three gas pressurized acoustic generators:  
               TABLE 4                          SONOLOG D-6C2 Benchmark Results                                             Face               Intensity   Elapsed Time   Angle   Secondary           (dB)   (microseconds)   (degrees)   Wave                     Frequency   Chamber pressure (psi)                                                 (Hz)   100   150   100   150   100   150   100   150               10   153   163   25   21   78   77   Y   Y       20   155   165   22   18   82   82   Y   Y       40   157   166   20   23   85   84   Y   Y       70   158   166   19   33   85   85   Y   Y                    
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                   
               
               
                 ECHOMETER INC. COMPACT GAS GENERATOR - 
               
               
                 Benchmark Results 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                 Face 
                   
               
               
                   
                 Intensity 
                 Elapsed Time 
                 Angle 
                 Secondary 
               
               
                   
                 (dB) 
                 (microseconds) 
                 (degrees) 
                 Wave 
               
            
           
           
               
               
            
               
                 Frequency 
                 Chamber pressure (psi) 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 (Hz) 
                 100 
                 150 
                 100 
                 150 
                 100 
                 150 
                 100 
                 150 
               
               
                   
               
               
                 10 
                 148 
                 156 
                 33 
                 20 
                 75 
                 79 
                 Y 
                 — 
               
               
                 20 
                 152 
                 159 
                 20 
                 12 
                 82 
                 83 
                 Y 
                 — 
               
               
                 40 
                 154 
                 161 
                 19 
                 11 
                 84 
                 85 
                 Y 
                 Y 
               
               
                 70 
                 156 
                 162 
                 18 
                 14 
                 86 
                 86 
                 Y 
                 Y 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                   
               
               
                 PREFERRED EMBODIMENT OF THE CURRENT INVENTION - 
               
               
                 Benchmark Results 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                 Face 
                   
               
               
                   
                 Intensity 
                 Elapsed Time 
                 Angle 
                 Secondary 
               
               
                   
                 (dB) 
                 (microseconds) 
                 (degrees) 
                 Wave 
               
            
           
           
               
               
            
               
                 Frequency 
                 Chamber pressure (psi) 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 (Hz) 
                 100 
                 150 
                 100 
                 150 
                 100 
                 150 
                 100 
                 150 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 10 
                 156 
                 163 
                 11 
                 18 
                 83 
                 84 
                 — 
                 — 
               
               
                 20 
                 160 
                 165 
                 8 
                 13 
                 85 
                 86 
                 — 
                 — 
               
               
                 40 
                 163 
                 166 
                 6 
                 8 
                 87 
                 87 
                 — 
                 — 
               
               
                 70 
                 164 
                 169 
                 5 
                 7 
                 87 
                 88 
                 — 
                 — 
               
               
                   
               
            
           
         
       
     
      From the results in the following tables there are similarities and differences in the generators. All generators increased in both intensity and face angle with an increase in the chamber gas pressure. Also all generators increased in both intensity and face angle with an increase frequency of the sound.  
      The change in chamber pressure had a different effect on the elapsed time for the prior art gas pressurized generators when compared to a preferred embodiment of the current invention, providing proof of the effect of the different mechanisms and systems used in the current invention to speed up the equilibration time. For the SONOLOG D-6C2 and the ECHOMETER COMPACT GAS GENERATOR the elapsed time for a pressure chamber set to 150 psi was less than the elapsed time for a pressure chamber set to 100 psi. This result supports the theory that the performance of these gas pressurized acoustic generators is linked to the pressure difference between the chamber and the void.  
      The preferred embodiment of the current invention produced the opposite result in testing. An increase in the pressure chamber produced an increase in the elapsed time. But regardless of this trend, the preferred embodiment of the current invention produced significantly shorter elapsed times than the prior art gas pressurized acoustic generators for all chamber pressures at all frequencies measured.