Echometer Model-M
Digital Dual Channel Fluid Level Instrument

Introduction

This operating manual contains information about the Echometer Model M Fluid Level Instrument including operating procedures, maintenance, shooting problem wells, chart interpretation and technical papers relating to the optimization of producing wells. Please read the first 25 pages and view the example of the strip chart output forms and charts on wells before operating the instrument. Additional technical papers can be accessed from the Echometer Web page, www.echometer.com, these articles offer additional information on the use of acoustic fluid level instruments to optimize production. Please read these papers at your convenience.

Limits of Liability

Echometer Company reserves the right to revise its software and publications with no obligation of Echometer Company to notify any person or any organization of such revision. In no event shall Echometer Company be liable for any loss of profit or any commercial damage, including but not limited to special, consequential, or other damages.

Information in this document is subject to change without notice and does not represent a commitment on the part of Echometer Company. The software described in this document is furnished under a license agreement or nondisclosure agreement. It may be used or copied only in accordance with the terms of the agreement. It is against the law to copy the software or any medium except specifically allowed in the license or non-disclosure agreement.

Copyright Notice

Copyright 1997,1998,1999,2000,2001,2002,2003 Echometer Company. All rights reserved. Federal copyright law protects this manual. No part of this manual may be copied or distributed, transmitted, transcribed, stored in a retrieval system or translated into any human or computer language, in any form or by any means, electronic, mechanical, magnetic, manual, photographic, photocopy, scanning, or otherwise, or disclosed to third parties without the express written permission of Echometer Company.

Trademarks

AWP, TWM, Q-Rod, EchoPUMP, Compact Gas Gun are trademarks of Echometer Company

1 - Safety Considerations

Echometer Schools

Additional Information

2 - Principles of Acoustic Measurements

Recording and Interpretation of Signals

Depth Calculation

3 – General Description – Model M

Instrument Panel

Wellhead Attachments

Remote Fire Gas Gun

High Pressure Gas Guns

Accessories

4 - Operation

General Recording Procedure

Operation of the Model M with the Compact Gas Gun

Operation of the Model M with the Remote Fired Gas Gun

Recommendations for Optimum Performance

Automatic Gain Setting (AGS) Mode Characteristics

Manual Gain Setting (MGS) Mode Characteristics

Collar Channel Automatic Gain Control (AGC)

Liquid Level Channel Gain Control

5 - Interpretation

6 - Problem Wells

7 - Battery and External Power Information

Important Notes and Instructions for Rechargeable Batteries

8 - Testing/Troubleshooting

Amplifiers Check

Filters Check

Microphone Cable check

Microphone Check

9 - Maintenance

Compact Gas Gun Pressure Rating

Compact Gas Gun Disassembly and Assembly Special Precautions

Remote Fire Gas Gun Pressure Rating

Remote Fire Gas Gun Disassembly and Assembly Special Precautions

10 – Calculation of Bottomhole Pressures

11 – APPENDIX

Fig. 1a - Compact Gas Gun Assembly Drawing

Fig. 1b - Remote Fire Gas Gun Assembly Drawing

Fig. 2 - Echometer Panel

Fig. 3 – Initial Header and System Test (Shown ½ Scale)

Fig. 4 – Data Information Form and Time Stamp

Fig. 5 – Upper/Lower Collars Accented

Fig. 6 – Prove Liquid Level

Fig. 7 – Well With Liner

Fig. 8 – Records of Compression/Rarefaction Initial Pulse

Acoustic Responses from Downhole Anomalies

Amplifiers And Filters Test

Microphone Cable Test

Microphone Test

Rate of Fill-up Graph

Use of Rate of Fill-up Information

Carbon Dioxide Cylinder

Carbon Dioxide Information (CO2)

Nitrogen Information (N2)

Fig. 9 – CO2 Cylinder w/ Hose

Fig. 10 –Filler Connector for 7.5 OZ. CO2 Cylinder

1 - Safety Considerations

Read this manual before operating the equipment.

Please observe all safety rules in operating this equipment. The pressure ratings of the Echometer gas gun and all fittings, hoses, etc. should always exceed actual well pressure. Because the casing pressure normally increases during a build-up test, caution should be exercised that the well pressure does not exceed equipment pressure ratings.

Do not use worn or corroded parts. A used or corroded fitting may not withstand original pressure rating.

All safety precautions cannot be given herein. Please refer to all applicable safety manuals, bulletins, etc. relating to pressure, metal characteristics, temperature effects, corrosion, wear, electrical properties, gas properties, etc. before operating this equipment.

The tests should not be undertaken if the operator, the test equipment and the well are not in conditions to operate safely. This equipment should not be used if the operator is tired, ill or under the influence of alcohol, drugs or medication.

Echometer Schools

Echometer Company offers schools on the use and applications of this equipment. You are invited to attend free of charge. A list of the schools, which are taught throughout the United States and Canada, will be sent upon request or can be viewed at http://www.Echometer.com

Additional Information

Please contact Echometer Company to obtain additional information or to clarify any questions that you may have in regard to the use of this instrument. The street and mailing address, phone number, fax number and e-mail address are given on the first page.

2-Principles of Acoustic Measurements

Acoustic liquid level instruments were developed in the 1930's. An acoustic wellhead attachment is connected to an opening in the casing annulus at the surface of a well as shown in Figure 1 in the appendix. The acoustic wellhead attachment consists of an acoustic pulse generator, a microphone and optionally a pressure gage. Throughout the years, acoustic pulse generators have included a dynamite cap, 45-caliber blank, 10 gauge black powder blank, a compression gas pulse and a rarefaction gas pulse. The explosive dynamite caps and blanks are a safety hazard and have resulted in damage to wells and environment. While these explosive sources should not create a problem if the casing annulus contains only hydrocarbon gas, major explosions have occurred when oxygen was allowed to enter the casing annulus during work-overs or when special conditions resulted in a vacuum in the casing annulus

The versatility, economy and convenience of gas guns have resulted in widespread use of this type of acoustic pulse generator. The expansion of gas from a volume chamber into the well generates the acoustic pulse. In most cases, compressed CO₂ or N₂ gas is loaded into the volume chamber, which is charged to a pressure greater than the well pressure. A valve in the wellhead attachment is opened rapidly, either manually or electrically, resulting in a pressure pulse being generated in the casing annulus gas. The acoustic pulse travels through the gas in the casing annulus and is partially reflected by changes in cross sectional area such as tubing collars, tubing anchors, casing perforations, etc. The remaining pulse energy is then reflected by the gas/liquid interface at the depth of the liquid level. The reflected signals travel back to the surface of the well where they are detected by the microphone.

The microphone within the wellhead attachment converts the reflected acoustic signal into an electrical signal consisting of a series of pulses, which correspond to the sequence of reflections. The microphone must operate over a wide pressure range from a vacuum to the maximum pressure that exists in the wells being tested. The microphone should be designed to cancel the mechanical vibrations of the wellhead while remaining sensitive to the acoustic signal reflections.

Recording and Interpretation of Signals

An amplifier/recorder filters and amplifies the electrical signal from the microphone and records the enhanced signals on a strip chart. Modern instruments use analog to digital converters and microprocessors to improve the signal quality and print the chart. The frequency content of the reflected acoustic signals varies depending on the characteristics of the initial pulse, the pressure in the gas, the distance traveled and the type of cross sectional area change. In general, as the pulse travels in a gas, the amplitude of the signal decays. The high frequency energy decays more rapidly than the low frequency energy. Thus, the acoustic response from the collars at the top of the well contains high frequency energy, the response from deep collars contains medium frequency and the signal from the liquid level is mostly low frequency energy. This is especially apparent in deep wells with low casing pressure. Fluid level instruments are designed to include various filters, which can be used to accent signals that correspond to these frequency ranges. The Model M records the signal on the dual channels. One channel is tuned to higher frequencies from the collars while the second channel is tuned to low frequencies from the liquid level. Single channel instruments can be operated in any of these modes and it is possible to switch from one frequency response to another while the instrument is recording. Initially, the single channel instrument is operated in the collar mode (high or medium frequency), which is then switched to the liquid level mode (low frequency) when the collar signal fades. Switching may be manual or automatic.

Depth Calculation

In most cases, once a strip chart record has been obtained and the liquid level signal has been identified, the operator must count the number of tubing collar reflections from the surface to the liquid level in order to calculate its depth. The corresponding number of tubing joints, multiplied by the average joint length yields the distance to the liquid level.

Other techniques are available for determining the liquid level depth. When other signals are identified on the chart, such as those generated by gas lift mandrels, liner tops, tubing anchors or perforations, the known depth of these anomalies can be used to calculate the depth to the deeper liquid level by the ratio of chart distance or elapsed time. When the lengths of tubing joints vary considerably, so that an average joint length is not representative, some operators placed an over-sized tubing collar (marker) to serve as a depth reference.

When the specific gravity or the composition of the gas in the annulus is known with some accuracy, then the velocity of sound in the gas can be calculated. The acoustic wave round-trip travel time from the initial pulse to the liquid level reflection is read directly from the strip chart, which displays timing marks. The round-trip travel time is divided by two and multiplied by the acoustic velocity to calculate the depth to the liquid level.

Still another technique involves measuring the acoustic velocity of the gas by sampling the casing gun into a tube of sufficient length to measure the velocity of sound in the gas by pulse testing. This technique is applicable only if the well continuously vents gas from the annulus so that a representative sample of the gas sample obtained at the top of the well will not be representative of the gas in the well.

The most common application of an acoustic liquid level instrument is to measure the distance to the liquid level in the casing annulus of a well. However, it can also be applied to measurements inside tubing. Other applications include determination of the distance to the mud or kill liquid level during drilling and work-overs. The acoustic instruments can be used to measure the distance to any change in cross-sectional area inside pipe or in the annulus.

3 – General Description – Model M

The Echometer Model M is a dual channel, microprocessor controlled amplifier/recorder. It permits better interpretation of reflections from downhole anomalies since two different filters are used to improve the signal. Processing and simultaneously recording reflected signal using two separate amplifiers having different frequency response, improve the ability of the operator to distinguish downhole obstructions from enlargements. The response from the liquid level (orreduction in annulus area) is opposite to the response from an enlargement such as a hole in the casing. The Model M uses modern electronics, integrated circuits, chart drive system and a thermal printhead, which result in a very compact and lightweight system.

The dual channel Model M accents and records collars on one channel, and the liquid level response on a second channel. The collar channel can be set to record sharp upper collars or deep collars. Selecting the proper collar filter will result in more accurate determination of the number of tubing collar reflections from the surface to the liquid level. The lower trace accents the signals from the liquid level, tubing anchor, gas-lift mandrels, casing perforations and other major anomalies.

A microprocessor is used with an analog to digital converter, memory chip, amplifiers, clock, timing circuit and other electronic components to improve the performance and utility of the instrument. When an acoustic pulse is generated in the well, the signals reflected from the collars at the top of the well are large but rapidly attenuate. The microprocessor is programmed to evaluate the signal level and increase or decrease the collar amplifier gain as necessary to optimize the quality of the recording. The collar and other signals will be recorded at a width of approximately 0.6-inch (12-mm), which simplifies the manual counting of the collars since the amplitude of the collar signal is maintained automatically. The automatic control of the recording level is called automatic gain control.

The microprocessor is used in conjunction with a timer. Since these instruments are used throughout the world, the universal coordinated time and date are printed on the strip chart. Also, the timing capabilities of the microprocessor, clock and timing circuit are used to place labeled markers at one-second intervals beginning from the instant the acoustic pulse is generated. This allows the operator to determine the round trip travel time very accurately. The travel time and the distance to the liquid level are used to compute the acoustic velocity of the gas in the annulus. The acoustic velocity the casing pressure and average temperature can be input to the utility program AWP for Windows to compute the gas gravity and the pressure distribution in the well, including the pump intake pressure and the pressure at the perforations.

In addition to recording both collar and liquid level signals simultaneously, the digital printhead generates a header, an analysis form, and prints the values of background noise, battery voltage and special instructions on the strip chart.

The entire instrument is contained in a waterproof, dustproof plastic housing having dimensions of 11 by 10 by 5 inches and weighs 11 pounds (5 kg). The following section describes the instrument panel and the function of the various controls.

Instrument Panel

The instrument panel is shown schematically in Figure 2 in the appendix. The following controls are used for operating the instrument and for checking that it is operating correctly:

Power Switch:

Momentarily placing the switch in the ON position energizes the amplifier, activates a red light that indicates that the battery is powering the electronics and records a header on the strip chart. The microprocessor performs a system test and checks the battery voltage. If the battery voltage is low, a message is printed to charge the battery. If the system is OK, the chart drive stops after printing the battery voltage and test signals on the collar and liquid level channels, and the message " TURN ON CHART DRIVE TO TEST WELL". The power can be turned off manually, or the power will automatically turn off after approximately 15 minutes of non-use.

Upper Collars/Lower Collars Switch:

This two-position switch selects whether the collar channel is connected to the high frequency (Upper Collars) or medium frequency (Lower Collars) filter circuits.

Collars Gain

This knob controls the gain of the collar channel. The most counter-clockwise position (AUTO) activates automatic gain setting and should be used first always. In the AUTO mode, the gain is set automatically. Having the gain indicator on a value greater than 1 when the chart drive is turned on allows the operator to control the amplifier gain by setting the gain control knob as desired before the “shot” is detected. After the “shot” is detected, the instrument uses the gain setting when the shot is detected and the operator cannot adjust the gain.

Liquid Level Gain

This knob controls the gain of the liquid level channel. The most counter-clockwise position (AUTO) activates automatic gain setting and should be used first always. In the AUTO mode, the gain is set automatically. Having the gain indicator on a value greater than 1 when the chart drive is turned on allows the operator to control the amplifier gain by setting the gain control knob as desired before the “shot” is detected. After the “shot” is detected, the instrument uses the gain setting when the shot is detected and the operator cannot adjust the knob.

Chart Drive Switch

This switch is used to turn on and off the chart drive. Turning the switch to ON begins the data acquisition sequence. This consists of printing the data forms followed by the gain settings and the noise level on both channels, followed by the statement GENERATE PULSE and the recording of the two channels. The chart drive continues on until the switch is turned OFF.

Input Connector

This BNC INPUT connector is the input to the amplifiers. When acquiring data, this INPUT connector must be connected to the microphone connector on the acoustic wellhead using a good coaxial cable with clean connectors.

Remote Fire Connector

Connects the instrument to the solenoid valve of a remote fire gas gun if a remote fire gun is utilized.

Remote Fire Switch

Depressing this switch operates the solenoid valve on a remote fired gas gun by applying 12 volts to the solenoid coil. Depress the switch for 1 second to fully release gas from the chamber.

Battery Charger Connector

Attaching the 110 VAC or the 220 VAC battery charger or the 12V-car battery power cable to this connector charges the built-in battery.

Test Connector and Test Switch

This TEST connector should be attached to the INPUT connector using the coaxial cable in order to check that the instrument and the coaxial cable are operating correctly. Depressing the test switch applies a test signal to the input of the amplifier via the TEST connector and the coaxial cable.

· Chart Paper Drive

Pushing the spring-loaded aluminum plate cover towards the right and lifting it from the left side accesses the chart paper. The paper is dropped into the cavity so that it unrolls counter-clockwise. After inserting the paper roll, the aluminum cover is replaced. The printed Echometer logo on the paper should face up since only this side of the paper is heat sensitive. The heat sensitive paper supplied by Echometer Company operates over a wide temperature range and is made for the Echometer Chart drive system. The chart drive has a paper sensor to determine when paper exists in the drive. If the sensor detects that paper is not present, power is not supplied to the printhead. If paper is not present in the drive system and power is supplied to the printhead, the printhead will be damaged because the small heating elements in the printhead will be overheated. Using paper that is not of the proper width may result in printhead failure. Use only Echometer paper to insure proper operation of the printhead and chart drive system.

Wellhead Attachments

Compact Gas Gun

The Compact Gas Gun consists of a microphone and a ten cubic inch volume chamber with a ¼” outlet valve. The outlet valve will open rapidly when the trigger is pulled. This generates a pressure pulse. If the pressure is greater in the volume chamber than in the casing annulus, a compression pulse is generated. If the pressure is greater in the casing annulus than in the volume chamber, a rarefaction pulse is created. A differential pressure must exist between the volume chamber and the casing annulus for a pressure pulse to be generated. The operator has the choice of using an explosion or implosion pulse.

Compression (Explosion) Pulse

Explosion utilizes an external gas supply to generate an acoustic pulse in the well. In the explosion mode, the volume chamber is charged from an external gas supply to a pressure in excess of the well pressure. Operating in the explosion mode keeps the inside of the chamber cleaner and results in less maintenance.

Rarefaction (Implosion) Pulse

If the well’s casing pressure is greater than 200 PSI, implosion can be used. This method uses the well’s pressure to generate a pulse. Use the gas gun filler/bleed valve to release gas from the volume chamber. An external gas supply is not necessary to operate in the implosion mode. Operation in this mode forces sand, moisture and other debris into the gas gun volume chamber and thus requires more maintenance including frequent replacement of “O” rings.

Description of Compact Gas Gun Control Functions (refer to drawing)

Volume Chamber Pressure Gauge

The volume chamber pressure gauge measures the pressure in the gas gun volume chamber. During normal operation, the volume chamber is charged to 100-psi more than the casing pressure. Use additional pressure if required for satisfactory results. If the internal gas valve is open, the gauge indicates the pressure between the gas gun and the casing annulus valve. If the casing annulus valve is open, the gauge indicates the casing pressure.

Casing Pressure Gauge Quick Connector

The quick connector is located on the side of the housing. A precision pressure gage having a range close to the pressure being measured will fit into the quick connector to enable the operator to obtain the casing pressure and casing pressure change with sufficient accuracy to perform calculations of producing BHP and casing gas flow rate.

Cocking Arm

The cocking arm is lifted to depress and close the valve between the gas chamber and the casing.

Casing Pressure Bleed Valve

This valve allows bleeding the pressure between the casing valve and the compact gas gun. Turn the knob counter clockwise to release the pressure. Verify that the casing valve is closed before opening the bleed valve.

Gun Filler-Bleed Valve

The filler-bleed valve is used to pressurize the gas gun volume chamber or to remove gas from the gas gun volume chamber. Gas is added to the chamber from a pressurized external gas source by insertion of mating quick connector, into the filler & bleed valve. Gas is bled from the chamber by rotating the knob clockwise. This action depresses the internal valve core and releases the gas from the volume chamber to the atmosphere.

Trigger Pawl

The Trigger Pawl is pulled to release the gas valve between the gas gun volume chamber and the casing. If sufficient pressure exists in the volume chamber or on the end of the gas valve, the gas valve will open.

Microphone

The microphone is a twin-disc pressure sensitive device that is vibration canceling.

Remote Fire Gas Gun

The remotely fired gas gun generates an acoustic pulse and detects the downhole reflections. The gas gun contains a volume chamber, which is filled with compressed gas to deliver the acoustic pulse to the well. A microphone housed in the gas gun detects the shot, collars and other wellbore reflections, and liquid level. The standard unit has a working pressure of 1500 PSI.

Gas Valve and Solenoid

The solenoid serves as a trigger mechanism to initiate the acoustic pulse. When energized, the solenoid lifts a small plunger and allows gas pressure to bleed off the top of the gas valve. Gas pressure then forces the gas valve open, causing an acoustic pulse to be delivered to the well as the gas flows from the volume chamber into the well, (see the remote fire gun diagram.) The gas valve does not hold pressure from the well. Therefore, gas pressure must be applied to the volume chamber inlet port in order to close it. Whenever the valve is left open, well fluids will flow backwards through the gun and into the volume chamber. This flow may entrain sand and other debris. These deposits may prevent the gas gun from operating properly. To minimize this potential problem, it is advisable to charge the volume chamber with clean gas before the casing valve is opened and as soon as the strip chart from any shot has been recorded. This will prevent the well fluids and debris from entering the solenoid gas valve mechanism and causing a malfunction of the firing mechanism.

Volume Chamber Pressure Gauge

The volume chamber pressure gauge measures the pressure in the gas gun volume chamber. It should be used to determine if the chamber pressure is sufficiently high (explosion mode) to generate the acoustic pulse. The volume chamber pressure should be approximately 100-psi in excess of casing pressure unless additional pressure is required to obtain desire results.

Casing Pressure Gauge or Optional Transducer

The casing pressure and casing pressure buildup during the acoustic test must be measured with an accurate and sensitive pressure gauge or sensor. The Remote Fire Gas Gun supplied with the Echometer Model M is equipped with a quick connect gauge that covers the range 0-200 psig. The user should consider the option of obtaining several gauges covering different pressure ranges.

Charging the Gas Volume Chamber

To charge the volume chamber, first connect the filler adapter to a 7.5 oz. CO₂ bottle. Then, press the adapter against the filler fitting on the gun. When these two fittings are pressed together, a valve core in the bottle is depressed and gas will flow from the bottle into the volume chamber. Charge the chamber to at least 100 PSI above casing pressure before attaching the gas gun to the casing annulus valve to prevent debris from entering the gas gun internal valve parts. The volume chamber pressure can be read on the gun-mounted gauge. A 5-LB, CO₂ bottle and hose with connector can be used to change the gun, if desired.

High Pressure Gas Guns

The 5000-psi gas gun is normally used in the implosion mode. It has an excellent noise-canceling microphone and generates a very good pulse when the ¹/₂-inch ball valve is opened rapidly and the well pressure exceeds 200-psi. When the 5000-psi gas gun becomes dirty due to debris imploding from the wellbore, the volume chamber and the microphone assembly can be easily flushed with a solvent. The 5000-psi gas gun requires very little maintenance. It is excellent for gas lift, flowing and high-pressure shut-in wells. It can be used in the explosion mode by charging the gas gun volume chamber to a pressure in excess of the well pressure.

The 15000-psi High Pressure Gas Gun operates in the implosion mode only. Excellent results have been obtained at pressures above 1500-psi through needle valves with 1/8-inch orifices, which are standard in most high-pressure wells.

For more details please refer to the Gun-Microphone Assemblies brochure in the appendix.

Accessories

Battery Charger (110 V- AC) or (220 V - AC if requested)

Automobile Battery Cable

Automobile Cigarette Lighter Cable

Casing Pressure Gauges

Precision Test Gauge

Precision Digital Gauge

Gas Cylinders

2-1/2 LB CO₂

5 LB CO₂

Nitrogen Cylinder

4 - Operation

Operation of the instrument is simple. First the acoustic wellhead should be attached to the casing annulus valve, and the cable connected between the microphone and the instrument. The valve between the casing annulus and the flow line should be closed to prevent the casing annulus gas from venting into the flow line causing excessive noise.

General Recording Procedure

When the power switch is turned on, a red LED light indicates that the battery is powering the electronics. The chart drive turns on and a header is printed as shown in Figure 3 in the appendix. Next, a system test is performed which also displays the battery voltage. If the battery voltage is low, a message to charge the battery is displayed. Then, the message is printed to "Turn on the chart drive to test well" and the chart drive stops until the chart drive switch is turned to the ON position. At this point the operator selects the type of collar response (filter) desired. Sharp upper collars can be selected for special applications such as shallow wells, irregular tubing length, dual tubing strings and other special applications. The lower collar position is selected for most deep wells especially with low casing pressure. Normally, both gain controls are set to the AUTO position and only changes from these settings are necessary for those cases when satisfactory recordings are not obtained in the automatic position. When the chart drive is activated, the form shown in Figure 4 is printed on the strip chart. This form is designed to insure that the operator will write all the pertinent information about the well and the test. This includes the well designation, the casing pressure, the casing pressure buildup rate and the latest well production test results. The universal coordinated time stamp is beneficial for tracking the sequence of shots and calculating the exact time interval between shots. The time interval is necessary when calculating rate of change in liquid level from which can be computed the well influx (or injectivity) rates or to compute pressure buildup rates. Next, the acoustic analysis form is printed on the strip chart. During the time that the forms are being recorded on the strip chart, the instrument measures the background noise on both channels and then analyzes the noise in terms of peak to peak amplitude and records the AUTO position when the chart drive is turned on, later adjustment of the gain control does not affect amplifier gain. Then, a message to generate the pulse is printed on the strip chart. When the shot is generated, the instrument detects the large signal and prints a vertical dotted line to mark zero time on the chart. Each second thereafter another mark is recorded and labeled with the corresponding elapsed time in seconds. If the “shot” is not detected by the electronics (which is indicated by the zero time mark), a larger pulse must be generated so that the electronics will detect the initial pulse. After the zero time mark is printed on the chart, operator adjustments of the gain control do not affect amplifier gain. This prevents the operator from increasing the gain, which might result in noise being mistaken for a liquid level kick. The operator turns off the chart drive after the liquid level response and other desired information is observed on the chart. The acoustic liquid level test can be repeated by reloading the gas chamber, turning on the chart drive, and generating another acoustic pulse. If the operator desires to manually select the amplifier gain, the gain control knob must be set at a value greater than one before the chart drive is turned on. The collar channel gain should be set so that the response is approximately 1/8 inch (3 mm) before the shot. The liquid level channel gain should be set so that the response is 1/16 inch (1 mm) before the shot. Operator adjustment of the gain control after the “shot” is detected and the zero time mark is recorded does not affect amplifier gain. If the recording level is excessive from downhole anomalies such as a tubing anchor or perforations, a lower gain setting should be used. Both channels may be set in AUTO gain setting mode or both in manual gain mode or one channel may operate in manual while the other is set to AUTO. Figure 5 shows two records. The upper record is with the filter setting on upper collars and the lower record shows the response when the filter setting is lower collars.

Operation of the Model M with the Compact Gas Gun

The compact gas gun is to be operated in the COMPRESSION (Explosion) or RAREFACTION (Implosion) mode. The operator should use the Compression (explosion) technique when the casing pressure is less than approximately 100 psig. The Rarefaction (implosion) technique may be used whenever the casing pressure is sufficient to obtain a good record.

COMPRESSION (EXPLOSION) MODE

Expansion of gas from the Echometer gas gun is used to generate a pressure pulse. The pressure pulse is positive since the gas chamber is charged to a pressure that exceeds the well pressure by at least 100-psi.

1. Securely attach the Echometer Gas Gun to the Casing Valve.

2. Close the Casing Pressure Bleed Valve and Filler Bleed Chamber Valve.

3. Lift the Cocking Arm to close the internal gas valve. This prevents debris from entering the volume chamber.

4. Open the Casing Valve to the Echometer Gas Gun slowly and Close the casing valve to the flow line.

5. Measure the Casing Pressure using the precision pressure gauge.

6. Record Time and Casing pressure.

7. Fill the volume chamber with gas (CO2 or N2) to at least 100-psi in excess of the Casing Pressure.

8. Connect the coaxial cable from the microphone to the Input of the Model M.

9. Turn Power Switch to ON.

10. Select the type of collar response desired and set the gain controls to AUTO.

11. Turn chart drive ON.

12. Generate pressure pulse by pulling Trigger Ring, after “Generate Pulse” is displayed on chart.

13. Turn chart drive OFF after detecting the liquid level signal.

14. Inspect the record and repeat the shot if the signal quality is not satisfactory.

15. Turn power switch to OFF after operation.

16. Record Time and Casing Pressure.

17. Close the Casing Valve between Echometer Gas Gun and the well.

18. Open the Casing Pressure Bleed Valve and release the pressure.

19. Open the Casing Valve to the flow line.

20. Remove the Echometer Gas Gun from the casing valve.

RAREFACTION (IMPLOSION) MODE

Gas is released from the well into the gas gun volume chamber to generate the initial pulse. Debris, moisture, corrosive liquids and chemicals, and other foreign material may be imploded into the gas gun volume chamber, which will increase maintenance requirements and may cause corrosion on the inside of the volume chamber.

1. Securely attach the Echometer Gas Gun to the Casing Valve.

2. Close the Casing Pressure Bleed Valve and Filler Bleed Chamber Valve.

3. Open the Casing Valve to the Echometer Gas Gun slowly and Close the casing valve to the flow line.

4. Pull Trigger Ring.

5. Lift the Cocking Arm to close the internal gas valve.

6. Measure the Casing Pressure using the precision pressure gauge.

7. Record Time and Casing Pressure.

8. Bleed the gas chamber pressure through the Filler-Bleeder Chamber Valve by rotating the knob clockwise until the gas gun pressure has decreased to approximately 200-psi below the casing pressure reading. Use greater or less differential pressure depending on the quality of the recording.

9. Connect the coaxial cable from the microphone to the INPUT of the Model M.

10. Turn Power Switch to ON.

11. Select the type of collar response desired and set the gain controls to AUTO.

12. Turn chart drive ON.

13. Generate pressure pulse by pulling Trigger Ring, after “Generate Pulse” is displayed on chart.

14. Turn chart drive OFF after detecting the liquid level signal.

15. Inspect the record and repeat the shot if the signal quality is not satisfactory.

16. Turn power switch to OFF after operation.

17. Record Time and Casing Pressure.

18. Close the Casing Valve between Echometer Gas Gun and the well.

19. Open the Casing Pressure Bleed Valve and release the pressure.

20. Open the Casing Valve to the flow line.

21. Remove the Echometer Gas Gun from the casing valve.

Operation of the Model M with the Remote Fired Gas Gun

The main differences in operating procedure are that the Remote Fired Gas Gun initial pulse is generated by depressing the Remote Fire Button on the control panel, and that this gun can only be used in the Compression (Explosion) Mode.

1. Securely attach the Echometer Remote Fire Gas Gun to the Casing Valve.

2. Charge the gas chamber to at least 100-psi in excess of the estimated well pressure to prevent debris from entering the volume chamber and the solenoid dart valve assembly.

3. Close the gas gun's Casing Pressure Bleed Valve.

4. Open the Casing Valve to the Remote Fire Gas Gun slowly.

5. Close the casing valve to the flow line.

6. Measure the casing pressure using the precision pressure gauge.

7. Record Time and Casing Pressure

8. Verify that the volume chamber pressure is at least 100-psi in excess of the Casing Pressure.

9. Connect the coaxial cable from the microphone to the Input of the Model M.

10. Connect the remote fire cable from the gun to the REMOTE FIRE connector.

11. Turn Power Switch to ON.

12. Select the collar FILTER and set the gain controls to AUTO.

13. Turn chart drive ON.

14. Generate pressure pulse by depressing the Remote Fire button for approximately one second to insure full opening of the solenoid valve.

15. Turn chart drive OFF after detecting the liquid level signal.

16. Inspect the record and repeat the shot if the signal quality is not satisfactory

17. Turn power switch to OFF after operation.

18. Record Time and Casing Pressure.

19. Close Casing Valve to the Remote Fire Gas Gun.

20. Open the Casing Pressure Bleed Valve and release the pressure.

21. Open the Casing Valve to the flow line.

22. Disconnect cables and remove the Echometer Gas Gun from the casing valve.

NOTES

1. On deep, low pressure wells; first select the lower collar position.

2. If the initial pulse is not detected which is indicated by the zero timing mark, use a larger initial pulse.

3. If the liquid level is not detected (especially in deep wells with low casing pressure), the volume chamber pressure should be increased in increments of 300-psi up to the limit of the available gas supply.

4. Do not use a larger volume chamber pressure than needed. Operating the gas gun at 300-psi requires twice as much gas as when operating at 150-psi. Only one half as many shots will be obtained from a gas cylinder.

5. When using CO₂ gas above 300-psi (at normal temperatures), liquid may form in the gas gun, which will result in considerably more gas being used per shot.

6. When using nitrogen gas, use a regulator so that the pressure will not exceed the working pressure rating of 1500-psi.

Recommendations for Optimum Performance

The Echometer wellhead should be as near as possible to the casing annulus (or the tubing) preferably within 5 feet. Short (5-10 ft) lengths of pipe can mask the desired downhole signals. Longer (20-60 ft) lengths will generate multiple reflections, which are hard to distinguish from collar reflections. Use a minimum of 90⁰ ells and tees and direct the blast straight into the well if possible. Two-inch connections are recommended, but one inch connections are generally satisfactory if the length of 1 inch pipe is kept to a minimum.

Proper sensitivity setting is very important. Select the AUTO gain setting for the first shot. The background noise level is indicated on the chart. Surface vibrations, leaking gas connections, gas “popping” out of the gas/liquid interface and other unstable conditions, cause this noise. This background noise is not a part of the signals when the pressure wave is generated. The instrument will automatically record the background noise at a low level and larger collar and liquid level signals will be recorded at larger amplitudes, which simplifies the interpretation of the chart. When operating in the AUTO mode, adjusting the sensitivity after the chart drive is tuned ON does not change the automatic gain selection made by the electronics and software.

The pressure pulse travels down the well and is reflected by tubing collars and the liquid level. The signals from upper collar reflections are strong, but the collar response becomes weaker as the pressure pulse travels long distances to the bottom of the well so that the reflections from the lower collars may be weaker than the background noise. The liquid level reflection varies from a strong signal in a shallow high pressure well to a very weak signal in a deep low pressure well. Only signals stronger than the background noise are meaningful in the recording. It is obvious that strong background noises must be reduced if the recording of lower collars and liquid level is to be obtained.

Background noise can be classified as surface mechanical vibration noise or acoustic noise. The source of noise can be determined easily by increasing the sensitivity until signal deflection is obtained. Closing the casing valve between the microphone and the annulus will cause a reduction in the noise level if its source is acoustic noise. If the signal level remains the same, then the noise is caused either by surface vibrations or by gas leakage from extraneous lines connected on the same side of the closed casing valve as the microphone. The microphone is shock mounted, but if the wellhead attachment vibrates excessively, unwanted signals are generated. Wellhead vibration result from running gas engines, chattering check valves and other reciprocating surface equipment. It may be necessary to eliminate wellhead vibrations to obtain better quality records in deep low-pressure wells. All other lines leading to the casing annulus should be closed.

The main source of down-hole acoustic noise is gas "popping" out of a gaseous annular liquid column or liquid falling into the wellbore. Downhole noise can also result from tubing and casing leaks. Generally, the down-hole acoustic noise can be reduced in relation to the desired reflected signals by causing an increase in the casing pressure. In order to do this, continue to pump the well with the casing vent valve closed. At low pressures, an increase of 10-psi in the casing pressure almost always improves the record and it only depresses the liquid level by 30 feet.

If the signal from the liquid level is not detected due to excessive surface vibration noise or down-hole acoustic noise, a larger signal from the liquid level can be obtained by generating a larger initial pressure pulse. Also, increasing the sensitivity so that the background noise level exceeds 1/8 inch, generally will make interpretation much more difficult and is not recommended.

Automatic Gain Setting (AGS) Mode Characteristics

The Echometer Model M uses a microprocessor, which is programmed to evaluate the signal level before the shot and set the amplifier gain as necessary to optimize the quality of the recording. The AGS mode on either or both channels is activated by selecting the AUTO position before the chart drive is turned ON. Both channels are normally operated in the AUTO mode. Changing the gain control setting from AUTO after the chart drive is turned ON will not affect the amplifier gain. In both channels, the AUTO mode detects the noise level in the well and adjusts the GAIN SETTING of both amplifiers so that the noise signal is recorded at a width of ¹/₈ inch on the collar channel and 1/16 inch on the liquid level channel. The noise level in mV peak-to -peak and the gain settings (such as A: 7.1) is printed on the header just before the legend "GENERATE PULSE" is printed. The "A:" signifies the system was in the AUTO gain setting mode and the "7.1" indicates the gain setting.

Manual Gain Setting (MGS) Mode Characteristics

MANUAL gain setting mode is selected by locating the gain control knob to a value between than 1 before the chart drive is turned ON. When the acoustic traces are displayed, adjust the gain on the collar channel until ^1/₈^-inch response is obtained. Adjust the liquid level channel gain control until ^1/₁₆^-inch response is obtained. Lower gain settings may be beneficial when the traces are over-driven. Higher settings on the liquid level channel, so that the background noise is ^1/₈^-inch, may be beneficial if the liquid level response is weak. The gain controls should not be adjusted after the initial pulse is generated. Both channels can be set to manual mode, or either channel can operate in manual mode while the other channel is in AUTO mode, or both channels can be set to AUTO mode.

Collar Channel Automatic Gain Control (AGC)

The gain of the COLLAR channel amplifier is automatically controlled so that the signal level is maintained at 0.6 inch peak to peak until the amplifier gain is increased to the setting that results in the background noise being recorded at an amplitude of 1/8-inch. This results in a record showing collars at an amplitude of 0.6 inch when strong collar signals are received. When the collar signal level fades to the background noise level or less, the collar trace and noise will be recorded at 1/8-inch, which indicates to the operator that collars are no longer distinguishable on the trace.

Liquid Level Channel Gain Control

When operating in the AGS mode, that is, the liquid level gain control is in the AUTO position before the chart drive is turned ON, the LIQUID LEVEL channel amplifier gain is kept fixed at the setting that is established automatically by measurement of background noise prior to the shot. AGC is not used. For large, reflected signals after the shot, the liquid level channel recording will show that these peaks and valleys are clipped. This method will insure that even low amplitude reflections caused by minor changes in cross section of the annulus (or tubing) as well as the liquid level signal from deep low-pressure wells will be detected as long as their amplitude exceeds the noise level. Adjusting the liquid level gain control after the chart drive is turned ON will not affect the amplifier gain in the AUTO mode.

When operating in the MGS mode, that is, the liquid level gain is set greater than 1 before the chart drive is turned ON, the liquid level gain control should be manually set so that the noise response is ¹/₁₆-inch before the shot. The gain control knob controls the gain. AGC is not used. On deep low-pressure wells, the manual gain control can be set so that the background noise is recorded at ¹/₈-inch before the shot is desired. If reflections from downhole anomalies are excessive, use a lower gain setting. In manual gain mode, the proper gain should be set before the initial pulse is detected by the electronics, which is indicated by the zero timing mark. When the initial pulse is detected, the electronics maintains the gain setting selected by the operator at the time of the pulse detection, and does not permit an increase in gain by the operator, which could result in the background noise being amplified and mistaken for the liquid level.

5 - Interpretation

In an average well, the following events will be recorded on the chart: a kick will show the initial blast. A series of small kicks will indicate the tubing collars and then the liquid level kick will be recorded. If the chart is allowed to continue to run, another kick will often occur after the liquid level kick at twice the time of the first reflected liquid level kick. This is a signal that corresponds to the pulse traveling from the gun to the liquid level and then to the surface where it is reflected by the wellhead back down the well and is again reflected by the liquid interface back to the surface. In shallow and in high pressure wells there may be numerous other reflections from the liquid level. These are known as "multiples" of the pulse. Since all these signals have traveled the same distance at the same speed the distance (time) from the initial blast to the first liquid level reflection will be equal to the distance (time) between the first liquid level kick and the second reflected level kick. Multiple liquid level reflections on very shallow liquid levels, which are 20 to 60 ft from the surface, can be misinterpreted as collar reflections.

The normal chart has a kick at the start of the trace which corresponds to the initial pressure pulse, a series of small evenly spaced kicks indicating the collar signals and a large kick indicating the liquid level. On some charts the collars can be distinguished from the beginning of the chart to the liquid level signal and all the collars can be counted. The most accurate procedure is to use the eleven point dividers and to mark off groups of ten collars directly on the chart. On other charts the collars cannot be distinguished clearly all the way from the beginning to the liquid level reflection. In these cases it may be convenient to repeat the test trying to improve the signal to noise ratio so as to be able to count a large percentage (better than 60%) of the collars in the well. In these cases it is necessary to count the collars to the last discernible collar reflection signal and then extrapolate the count to the liquid level, using the eleven point dividers set on the last collar spacing. The total number of collars counted multiplied by the average tubing joint length results in the depth to the liquid level. This assumes that the range of tubing joints is similar for all tubing in the well. This procedure may not be used if there are significant differences in the lengths of tubing joints. Alternative methods to determine the depth to the fluid level are discussed in the following section.

On both channels, the direction of kick indicates enlargements and reductions in the cross sectional area of the annulus (or internal diameter of pipe if shooting down tubing). For an explosion signal, objects which reduce the cross sectional area of the annulus result in compression reflections and are recorded as downward kicks when the top of the chart is at the left of the operator. Such objects would be liners, tubing anchors, paraffin deposits or the liquid level. Conditions that increase the area of the annulus result in rarefaction reflected waves and are recorded as upward kicks. Such conditions include perforations, "shot" holes, parted casing, parted tubing and the end of the tubing casing annulus. If an implosion pulse is used, then the responses will be reversed from those of an explosion pulse.

Please refer to the appendix where several examples of traces corresponding to various wells and different cases of signals are presented.

For the explosion pulse the liquid level is recorded as a downward kick. If the liquid level is 20 feet or so in a "shot" hole, then the signal would first deflect upwards, then down as the sound wave is reflected from the liquid level. Recording the liquid level below a liner will show a downward kick at the liner and a downward kick at the liquid level then an upward kick if the recorder is still running. The upward kick corresponds to the signal generated at the liner by the wave which was reflected at the liquid level and which is returning to the surface. When the wave passes from the narrow liner to the larger casing a portion of the wave is converted to a rarefaction pulse, which then travels down to the liquid level and then to the surface where it is recorded.

6 - Problem Wells

Obtaining a good record is made more difficult by excessive surface vibrations, excessive down-hole noise from gaseous liquid columns, improper wellhead connections, dirty microphone and electrical connections, or low casing pressure.

Excessive surface vibrations and downhole noise should be reduced as much as possible. The gain controls permit an actual measure of extraneous noise as described in Section 4.

Any well venting gas to the atmosphere, venting gas to the flow line or using casing gas to operate an engine, will have a gaseous liquid column if liquid exists above the pump or formation. The amount of liquid present in a gaseous liquid column can be determined by a casing pressure build-up test. Another technique is compression of the gaseous column with casing pressure to determine the gaseous column gradient. Additional information is presented in the papers "Producing Bottom Hole Pressures" and "Acoustic Foam Depression" in the appendix. Gaseous columns caused by gas bubbling through oil cause excessive down-hole noise and can be a problem in obtaining clear records of deep collars and liquid levels. Increasing the casing pressure by closing the flow line-casing valve will generally result in much improved signals. The pressure in the gas gun volume chamber may have to be increased to the maximum so as to increase the signal to noise ratio.

Whenever there are doubts that the correct liquid level signal has been identified the best way to differentiate it from other signals (such as signals from liners, paraffin rings, or liquid influx from perforations) is to cause the liquid level to move. The liquid level signal is the only signal that can move in a well and such movement identifies the liquid level. A high fluid level can be depressed by increasing the casing pressure. An increase of 10-psi in the casing pressure will depress a gas-free liquid level by approximately 30 feet. The liquid level will rise when a producing well is shut down. The rate of fill-up will vary with the productivity of the well and the annular volume. A Rate of Fill-up chart is presented in the appendix and may be used to estimate the amount of time required for liquid level rise. Note also that this chart may be used to estimate the production rate from a well by shutting in the well and measuring the change in fluid level as a function of time, then using the chart to estimate the production rate.

If a chart shows numerous "kicks" which are difficult to interpret, the shot should be repeated and the new chart compared with the first recording. All "kicks" should be duplicated on each chart. Signals that are not duplicated correspond to stray noises and other random signals. The source of these noises should be identified so as to eliminate them as described above.

The effect of casing pressure on signal quality is very important. Stronger signals are returned in high-pressure wells. It is especially difficult to obtain good recordings in deep wells with the casing pressure near or below atmospheric pressure.

On rare occasions, paraffin deposits, scaling, dirty tubing or other conditions can result in additional down-hole signals, which make it difficult to count collars or to determine the fluid level depth. In extreme cases it may be necessary to clean the tubing and casing to remove the foreign material.

7 - Battery and External Power Information

The Echometer Model M instrument will operate from the self-contained rechargeable battery or from a power cord, which is plugged into an automobile cigar lighter or is connected to an external 12-volt battery.

A sealed, rechargeable, lead cell, 2.5 amp/hour internal battery is used in the Echometer Model M instrument. The battery is similar to a 12 volt sealed automobile battery. The battery charger provided with the unit permits charging the battery from an AC power outlet. Either a 110 VAC or a 220 VAC unit can be specified at the time of ordering. The battery charger will charge the battery at a rate of 500 ma until the battery is almost fully charged then it will trickle charge at a 25 ma rate. The red light on the charger is ON when the charger is charging at high rate. When the charger is in trickle charge mode the light is OFF. Approximately 7 hours are required to charge a fully discharged battery. Continuous charging does not damage the battery.

When operating with the cigar lighter power cord, a low battery will be partially charged by an operating automobile system in 5 to 10 minutes and will be completely charged if the car is driven for four hours.

The battery should be charged when the operating voltage printed on the header of the strip chart drops to about 11.3 volts. The battery can be charged more often if desired. Best operating performance will be obtained with battery temperatures from 0 to 120 degrees F (-15 to +50 C). The battery has less capacity and voltage at lower temperatures.

Temperature ^oF	Temperature ^oC	Battery Life, Hours
104	40	4
77	24	3.5
32	0	3
-4	-20	2

The battery should be charged when the operating voltage printed on the strip chart drops to about 11.3 volts. Charging more often will improve battery life. A message to charge the battery is printed on the strip chart when the voltage drops to 11 volts. The amplifier current drain is 330 ma. The amplifier, chart drive, and print head current drain is approximately 800 ma. A fully charged battery in good condition should perform more than 200 tests before the battery will require recharging. The battery is rated at 2.5 amps/hour.

Long storage periods without charging will severely reduce service life. An unused, fully charged battery will discharge in 6 months at 113^oF, in 15 months at 77^oF (20^oC) and in 50 months at 23^oF (-5^oC). A discharged battery deteriorates rapidly. Experience has indicated that the battery should be recharged at least monthly using the AC charger. Charging the battery before it is fully discharged will result in longer battery life.

Battery Sulfonation

A very deeply discharged battery may not accept a charge normally. The red light on the AC charger does not come on when the AC charger is attached. After a period of time, up to 6 hours, the red light will come on indicating that charging has started. After 7 hours the red light will go out indicating the battery is charged. In some cases a battery will not accept a charge and will require replacement.

Important Notes and Instructions for Rechargeable Batteries

The battery is rated at 2.5 Amp-Hour. The Model M current drain with the chart drive on is 1 Amp. Thus the battery operating ON-time is approximately 2.5 hours and the unit would use about five rolls of paper.

1 - Charge battery before using. Use ONLY the CHARGER that is provided with the Echometer Model - M.

2 - When not in use for extended periods of time, remove battery from the instrument and store in a cool dry place or leave the AC charger connected continuously.

3 - Do not short-circuit the battery terminals.

4 - Keep away from fire and do not incinerate when disposing of battery ... it may explode.

5 - Under no circumstance should you attempt to open the battery case.

6 - Do not expose battery to moisture or rain.

7 - Do not drop, hit or abuse the battery, because it will break and may release electrolyte as well as expose cell contents, which are corrosive.

8 - It is perfectly normal for the battery to become warm to the touch during charging and discharging.

9 - Running time depends on the power demand and the operating temperature.

10 - The life of the battery under normal conditions may be as long as 1000 charge-discharge cycles.

11 - New batteries may require four or five charge-discharge cycles before achieving their designated capacities.

12 - Sealed lead-acid batteries may be stored as long as 12 to 18 months in a cool dry place. They should be recharged every 6 months.

13 - Always fully charge the battery before using it after it has been stored for over one week.

8 - Testing/Troubleshooting

The Echometer Model - M has an internal test circuit, which is used to verify that the electronics and the acoustic cable are operating correctly. The test circuit is activated automatically when the power is turned ON. A system test and battery voltage is displayed on the strip chart. (See Appendix Example).

In addition a test switch and connector allows testing the microphone cable in addition to the electronic circuits. Connecting the microphone cable from the TEST connector and to INPUT connector will verify that the cable is not open or shorted out.

After checking the operation of the electronic circuits the microphone sensitivity should be checked.

Amplifiers Check

This test verifies the proper response and gain of the liquid level and collars amplifiers. See Appendix.

Filters Check

This test verifies the proper response of the Upper collars and Lower collars filters. See Appendix.

Microphone Cable check

This test verifies the integrity of the microphone cable. See Appendix.

Microphone Check

Proper operation and sensitivity of the microphone can be verified with this test. See Appendix.

9 - Maintenance

The Echometer Model –M instrument should be kept clean. The battery should be kept charged as described by the instructions in Section 7. Do not subject the unit to shock loads.

Using the Compact Gas Gun or the Remote Fire Gas Gun in the EXPLOSION mode (the preferred mode of operation) will require minimum maintenance. Clean and inspect threads of the Microphone Protector (2 inch threads). Replace this collar if it is worn or damaged.

The microphone cavity should be rinsed with a solvent (kerosene) periodically to remove any oil, grease or any foreign materials that may have accumulated. DO NOT REMOVE the microphone.

When using in wells that produce sour gas or oil (H₂S) it is recommended that the microphone cavity be coated with a fine layer of grease or corrosion resistant primer. This will retard the formation of corrosion pits.

If the gas gun does not operate properly it probably needs replacement of "O" rings and it should be disassembled. Be sure to check all threads, the moving gas valve and all other pieces thoroughly. If any signs of wear or deterioration exist replace the parts before reassembling. Replace the "O" rings when any sign of deterioration exist. Lubricate the gas valve and all "O" rings with light oil before assembly.

Compact Gas Gun Pressure Rating

The pressure rating of a NEW compact gas gun is 1500-psi. After the gun has been used, its pressure rating should be derated by the operator depending on the condition of the gun. The compact gas gun may have internal and external corrosion, deep external wrench marks, improperly tightened cap bolts or worn threads. Corrosion causes pitting and reduction in the strength of the remaining metal. Any corrosion should be examined visually and depending on its severity the maximum working pressure of the gas gun should be reduced. Marks and notches caused by pipe wrenches, any type of bending or denting of the metal will cause a reduction in strength. Derate the gas gun for any noticeable physical damage to the gas gun.

The stainless steel 2-inch line pipe thread on the housing will become worn after unprotected use. For this reason a knurled microphone protector has been added to the gun to protect the threads on the gas gun. This protector should be replaced whenever excessive corrosion or wear has occurred.

The compact gas gun can be operated in an implosion mode. That is, gas from the casing can be released into the compact gas gun to create the pressure pulse. Often times, the gas in the well contains sand, water vapor and corrosive gases. Thus, operating in the implosion mode will result in additional maintenance requirements.

The preferred mode of operation when an external gas source (CO₂ or N₂) is available is in the EXPLOSION mode. The gas gun chamber should be charged to a pressure in excess of the well pressure before the gas gun is exposed to well pressure (follow operating instructions in section 4). This will isolate the internal parts from the well fluids and they will have longer life and require less maintenance.

Compact Gas Gun Disassembly and Assembly Special Precautions

When the gas gun is disassembled, always REMOVE the MICROPHONE FIRST. The microphone is located at the lower end of the gas gun. It is removed by unscrewing a 10-32 x 1-1/4 cap screw. Then remove the Housing Cap by unscrewing the four Allen-head cap bolts.

When reassembling the gas gun, always FIRST attach the Housing Cap to the housing with the 4 bolts then INSTALL the MICROPHONE LAST. Do not over torque bolts.

The four cap bolts, Part No. GG-210, which hold the housing cap to the main gas gun housing should be properly tightened and periodically replaced. The proper torque for the bolts is approximately 50 inch-pounds. The "O" ring seal between the housing cap and the housing does not require excessive tightening of the bolts to properly seal. Do not over tighten bolts. If the bolts are excessively tightened, the bolts would be pre-tensioned to a stress such that when internal pressure is applied, the additional force on the housing cap generated by the internal pressure could cause the bolts to fail.

Remote Fire Gas Gun Pressure Rating

The pressure rating of a NEW Remote Fire gas gun is 1500-psi. After the gun has been used, its pressure rating should be derated by the operator depending on the condition of the gun. The Remote Fire Gas Gun may have internal and external corrosion, deep external wrench marks, or worn threads. Corrosion causes pitting and reduction in the strength of the remaining metal. Any corrosion should be examined visually and depending on its severity the maximum working pressure of the gas gun should be reduced. Marks and notches caused by pipe wrenches, any type of bending or denting of the metal will cause a reduction in strength. Derate the gas gun for any noticeable physical damage to the gas gun.

The Remote Fired Gas Gun cannot be used in the implosion mode. In order to protect the internal parts, the gas chamber should be charged to a pressure of at least 200-psi or a pressure greater than the well pressure (if known) before installing the gas gun onto the casing valve. This will insure that debris will not be admitted into the solenoid/dart valve mechanism. This will greatly reduce the need for maintenance.

Remote Fire Gas Gun Disassembly and Assembly Special Precautions

When disassembling DO NOT REMOVE the MICROPHONE unless results of the troubleshooting tests have shown that it is not operational.

All internal parts can be accessed from the end where the volume chamber is attached.

Removing the volume chamber will expose the retaining nut that gives access to the gas valve. Remove with a socket wrench. Use the threaded rod (provided with the repair kit) to pull the gas valve from the housing. Inspect and replace if needed. Replace the "O" rings as needed.

All other connectors, ports, and the solenoid valve can be serviced without need to remove the volume chamber.

10 – Calculation of Bottomhole Pressures

Bottomhole pressure calculation in static and producing wells is described in technical papers and is facilitated by the use of software, which is supplied with the Echometer Model M. Details of the calculation methods used by the software are found in technical papers on the internet at www.echometer.com . Various versions of the programs are available for use in conjunction with DOS and Windows based computers. The available programs include:

BHP and AWP in DOS for calculation of static and producing BHP

AWP2000 for Windows 9x, ME, NT, 2000 and XP for calculation of static and producing BHP can be downloaded for free from the Echometer Web page, www.echometer.com.

The programs have been designed to be easy to use and they require a minimum of data. The user should however remember that the results from computer calculations are only as good as the data that is entered. Thus, make sure that the data input is accurate or the results will be meaningless.

11 – APPENDIX

Fig. 1a - Compact Gas Gun Assembly Drawing

Fig. 1b - Remote Fire Gas Gun Assembly Drawing

Fig. 2 - Echometer Panel

Fig. 3 – Initial Header and System Test (Shown ½ Scale)

Fig. 4 – Data Information Form and Time Stamp

Fig. 5 – Upper/Lower Collars Accented

Fig. 6 – Prove Liquid Level

Fig. 7 – Well With Liner

Fig. 8 – Records of Compression/Rarefaction Initial Pulse

Acoustic Responses from Downhole Anomalies

Amplifiers And Filters Test

Microphone Cable Test

Microphone Test

Rate of Fill-up Graph

Use of Rate of Fill-up Information

Carbon Dioxide Cylinder

Carbon Dioxide Information (CO2)

Nitrogen Information (N2)

Fig. 9 – CO2 Cylinder w/ Hose

Fig. 10 –Filler Connector for 7.5 OZ. CO2 Cylinder


Echometer Company 5001 Ditto Lane Wichita Falls, Texas 76302 U.S.A.	Phone: (940) 767-4334 Fax: (940) 723-7507 E-Mail: info@echometer.com
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