cement bond log

1 11/16” CBL CEMENT BOND TOOL

1 11/16" Cement Bond Tool

APPLICATION OF SERVICE TOOL RESPONSE 9–3

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Cement Bond Response 9–3 Acoustic Wave Propagation 9–6 Acoustic Losses in Liquids 9–6 Gamma Ray Curve Response 9–8 Neutron Detector Response 9–8 Casing Collar Locator 9–8 Gamma Ray Calibration Principles 9–9 GR Primary Calibration 9–9 Neutron Calibration Principles 9–11 Neutron Primary Calibration 9–11 CBL Amplitude Calibration Principles 9–12 CBL Travel Time Calibration Principles 9–13 AMPLITUDE AND TRANSIT TIME DETECTION METHOD 9–14 Peak Amplitude Detection 9–15 Peak Transit Time Detection 9–15 Acoustic Waveform Digitization 9–15 Tool Calibration Principles 9–16 Standard Two-Point Linear Calibration 9–16 Gain 9–16 Offset 9–16 Calculating Log Results 9–17 GR Shop Calibration Summary 9–18 CBL Shop Calibration Summary 9–19 Block Diagrams 9–20 Tool Specifications 9–21 Casing Collar Locator Section 9–22 Gamma Ray Section 9–22 Cement Bond Section 9–22 Neutron Detector Section 9–22 Gamma Detection 9–24 SCINTILLATION DETECTORS 9–24 The Scintillating Crystal 9–25 The Photomultiplier Tube (PMT) 9–26 Neutron Detection 9–26 Thermal Neutron Detectors 9–26

CASING COLLAR LOCATOR BLOCK DIAGRAM ANALYSIS

9–27 9–29

Mechanical 9–29 Special Features - Mechanical 9–30 Electronics 9–30 Simplified Block Diagram 9–32 Casing Collar Locator: 9–32 Power Supply: 9–32 Transmit/Receive Logic: 9–32 Receiver Signals: 9–33 Gamma Ray/Neutron Anti-Coincidence Circuits:

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HARDWARE CONFIGURATION 9–38 BOOT UP SYSTEM 9–39 LAUNCH CLASS LOGGING SOFTWARE ii

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Select Tool Service Configuration 9–42 PRIMARY CALIBRATION 9–45 Enter tool data: 9–46 1 11/16" Tool 9–47 Tool Power UP 9–48 GR Calibration 9–48 CCL Check 9–49 Neutron Shop Calibration 9–49 Log Presentation 9–50 Downhole Operational Checks & Verification Repeat Section 9–56 Main Run 9–57 Rigdown 9–57

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iii

Section

9 1 11/16” Cement Bond Tool Application of Service The Cement Bond Log Combination Tool provides a cement bond log, a casing collar locator signal, a gamma ray log, and a neutron log simultaneously. This combination of logs offers the user economy of operation since all data may be gathered on one trip into the borehole. These logs assist in determining the quality and extent of the physical bond between the casing and the surrounding cement sheath, and provide depth, porosity, and lithology correlation data as well as gas detection, casing collar and other anomaly detection. A Cement Bond Log combination tool (CBL) is used to simultaneously run a cement bond log, a gamma ray log, a neutron log and a casing collar log. In its simplest form, a combination tool could consist of a CCL device, a gamma ray detector, a neutron source/detector and a sonic device capable of generating sonic pulses and detecting the travel time of the pulses as they pass from transmitter to receiver through the formation. The sonic return signal may be recorded as a continuous waveform or as an intensity pattern to allow additional interpretation of the bond log.

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1 11/16" Cement Bond Tool

Adding a 1 11/16” GNT tool provides data used for lithology, correlation, and porosity determinations. A Cement Bond Log combination tool (CBL) is used to simultaneously run a cement bond log, a gamma ray log, a neutron log and a casing collar log. In its simplest form, a combination tool consists of a CCL device, a gamma ray detector, and a sonic device capable of generating sonic pulses and detecting the travel time of the pulses as they pass from transmitter to receiver through the formation. The sonic return signal may be recorded as a continuous waveform or as an intensity pattern to allow interpretation of the cement bond log. The GR curve may be used as an aid in identification of lithology. The CCL curve is used to locate casing collars with respect to formation lithology breaks, providing depth control when running perforating or bridge plug/packer services.

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Tool Response Cement Bond Response The bond section primarily determines the quality and extent of the physical bond between the casing and the surrounding cement sheath. The function of the bond circuit relates to the difference in sound transmission between free pipe (pipe not bonded to cement) and pipe partially or totally cement bonded. The sonic section measures travel time of sonic pulses from the transmitter to the receiver. The travel time is related in a known fashion to the type of formation between the cement sheath and the surrounding formation. Bond logs are enhanced by the use of photographic recordings of either the complete sonic wave shape or by transforming the amplitude peaks of the wave shapes into equivalent intensity patterns (MSG). This information is useful in interpretation of structural anomalies in the surrounding formation. Cement bond logs typically combine some form of the full wave display (MSG, XY plot) with the pipe amplitude curve and a Travel Time (TT) curve. The travel time curve is the measurement of the time in microseconds it takes for the acousitc energy pulses to travel from the transmitter to a receiver. The TT curve is useful for checking the centering of the tool in the wellbore in areas of poor bonding. The pipe amplitude curve is a measurement of the acoustic energy magnitude received at the receiver. As cement bonding increases the acoustic energy attenuation increases thus less energy is “seen” at the receiver. For an acoustic tool consisting of a transmitter and receivers, there is a mathematical relationship between the measured E1 amplitude at the receivers and the attenuation of the acoustic energy or acoustic wave. This is expressed as: a = ( 20 / Z ) log 10( A1 /A2 )db The equation shows that the attenuation is a logrithmic function of the amplitudes. Here “a” is the “attenuation factor” or the attenuation rate of the medium. It is measured in decibel/length. A1 and A2 are the amplitudes (in millivolts) of the E1 peaks at two different receivers separated by a distance “Z”. In actual logging the transmitter is A1 and A2 is the receiver, making the “Z” the distance from the transmitter to the receiver. How acoustic waves propagate down the pipe is not a well-understood phenomenon. Difficulty arises because the pipe thickness is much less than the wavelength of the acoustic signal, i.e. the pipe can not be viewed as a “thick” medium. What is known is that a pipe or casing

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wave is transmitted and its velocity can be closely approximated by us the following equation.

Here Vp = compressional velocity in the bulk casing material. Vs = shear velocity in the bulk casing material. Notice from the above equation that the casing wave velocity is independent of the bounding and adjacent formation. For cement bond logging, this implies that the casing arrival time should be constant for a given casing I.D. regardless of the degree of cement bonding. This arrival time can be estimated for a centered tool by Tcasing = I.D. casing (in feet x delta-T fluid + L x delta-t casing. L = tool offset. The acoustic signal excites leaky and normal modes in the cased borehole in a manor analogous to that in the open hole. Although the steel and cement layers slightly complicate the picture, the wave’s generation and propagation are still caused by constructive interference effects between reflected and refracted waves. Stoneley waves are generated in the casing much like it is in the open hole case. Now though the casing and cement flexes with the borehole wall to produce the propagating wave. In the mid sixties Welex introduced the Micro-Seismogram (MSG).* For the first time all of the acoustic arrivals were presented on a log that combined a modified oscilloscope presentation with the standard amplitude curves. The variable density presentation, utilized by Welex, was not new but had been used by the seismic industry and was called a variable density seismogram. Since the spacing used in downhole surveys are small compared to those used in seismic exploration, Welex coined their Variable Density Log (VDL) as a Micro-Seismogram™. ™ of Halliburton Energy Services

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With the MSG, acoustic coupling at the pipe-cement interface and the cement-formation interface is easily investigated. Where good cement bond exists the MSG also provides much information regarding the formation character. Figure 4 shows a bond log that uses the MSG with the pipe and formation amplitude curves. Figure 5 shows the conversion of the acoustic signal to the MSG presentation.

Figure 0–1

Most cement bond logs usually combine some form of the full wave display (VDL, XY plot, etc.) with the pipe amplitude curve and a travel time. The travel time curve is essential for verifying the centering of the tool in the wellbore, as well as indicating fast formations

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Acoustic Wave Propagation In acoustic cased hole logging the usual method of obtaining attenuation information is by recording the amplitude of an acoustic signal at a receiver located a distance from the transmitter. Figure 7 illustrates the path of this signal through casing. From the figure we see the measure of the attenuation involves the ratio, AT /AR, of the amplitude of the initial wave at the transmitter to the wave's amplitude AR at the receiver. The actual attenuation of the signal, assuming a constant transmitter output, is due to the composite effects of various travel paths.

Figure 0–2

Acoustic Losses in Liquids The term "M" in Equation 2 represents the acoustic attenuation in the wellbore fluid. Attenuation and transmission of sound waves in the wellbore depend on the viscous damping of the wellbore fluid. For different types of completion fluids, the attenuation effect can differ drastically. Traditionally, the difference in fluid attenuation effects has been considered negligible in cased hole logging. Nomographs and charts have been developed assuming the wellbore fluid to be fresh water. Recent studies by Schlumberger have shown the differences in fluid attenuation effects must be considered. The often used nomographs for determining cement strength from CBL amplitude measurements. can be in considerable error if completion fluids such as CaC12 , ZnBr2 , and CaBr2 are used instead of water.

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Schlumberger's results show that bond log amplitudes vary dramatically with the wellbore fluid acoustic impedance; there was a 70% increase in signal amplitude for 11.5 lb/gal (1370 kg/m3) CaC12 over the signal amplitude that would have resulted from fresh water (all other conditions kept constant). Figure 0–3 Fluid Attenuation Effect shows the attenuation effect, as measured by the amplitude, for different types of completion fluids in free pipe.

Figure 0–3 Fluid Attenuation Effect

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Gamma Ray Curve Response The gamma ray section of the tool counts the number of natural gamma rays present in the logged formation. The scintillation detector crystal senses the presence of gamma rays by producing an electrical pulse from these accelerated or excited electrons for each ray that passes through the detector.

Neutron Detector Response The combination tool may be run with or without the neutron section. If the neutron section is not to be used, it is recommended that it be removed and replaced with the bull plug. This will prevent accidental over-current conditions. When installed, the neutron section uses a 5 curie Americium 241-Beryllium source. The source-to-detector spacing is fixed at nineteen inches thus providing a greater depth of investigation. The neutron log is used as a depth correlation curve when the gamma ray curve is featureless. The purpose of the correlation curve is to establish the depth relationship between open hole logs and casing collars. This allows a perforating gun, which is normally run with a collar locator on top, to be positioned accurately from the zone to the nearest casing collar, instead of from the surface. The combination CBL tool provides depth correlation and cement bonding information on one run through a wide variety of formation conditions.

Casing Collar Locator The Casing Collor Locator (CCL) requires no calibration. The permanent magnets should be charged at least quarterly. The magnetic field created by the two magnets induces a small voltage in the coil positioned between the two magnets. The signal to noise ratio is critical to obtaining reliable repeatable collars. As the tool is drawn up the well the increase in metal mass at the pipe joints will cause a disruption in the magnetic field resulting in a variation of the induced coil voltage. The variations of voltage must be of great enough magnitude to be differentiated from noise by the surface equipment.

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Gamma Ray Calibration Principles The 3 1/4” CBL gamma section consists of a detector, counter and electronics. The detector is a scintillation type that outputs a discrete electrical pulse for each gamma ray detected. Although the height of the pulses are proportional to incident gamma energy, the basic gamma tool does not sort the pulses, it merely counts those above some discrimination level. Therefore the processed information is merely the count rate (counts/second) per depth sample. In order to output a standard result log, independent of tool systems, a unit of measurement called the API Gamma Ray Unit is used for the log output. The 3 1/4” CBL is a gross gamma tool and as such records the total gamma activity in the wellbore without regard to the source, while tools such as the spectral gamma tool is a spectral analyzer that identifies the source and gives the contribution (concentration) of each of the elements (potassium, uranium and thorium) to the overall spectrum (countrate).

GR Primary Calibration The Primary Calibration is the API standard Pit constructed at the University of Houston. The details of the Pit are written in section 4 of this manual. The API standard defines the difference in radioactivity between the neat cement and the radioactive cement mixture as 200 API units. Any logging service company may place its tool in this pit to make a calibration. In doing so, a sensitivity factor, G', would be computed from the definition: [Tool Response (Hot) - Tool Response (Cool)] G' = 200 API or 200 API ' G = ----------------------Tool Response (Hot) - Tool Response (Cool) Here, Tool Response is usually in CPS, and Hot and Cool refer to the radioactive and non-radioactive zones respectively. Once calibrated in the test pit, the tool's log response is now given by: GRLog = G' (Tool Response) and is independent of the type of tool and other instrumental factors, and thus satisfies the purpose of a standard calibration. The thorium blanket is constructed and calibrated back to the API Primary pit and is used for Shop calibrations and Field verifications. With this calibration source, field calibration of all natural gamma tools involves determining a gain factor from: Calibrator value in API (as seen by standard tool)

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G= ---------------------------------------Calibrator value in field tool units Since the calibrator value was established by the standard tool calibrated in the API test pit, the calculated G (which is proportional to G') enables all field tools to give standard results (logs) in API units. Thus the modified log response is: GRLog = G (field tool response)

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Neutron Calibration Principles The Neutron Sub consists of a chemical source, an He3 detector and the associated electronics that process the information for transmission to the surface via a wireline cable. The source is a chemical mixture of radioactive elements that when combined, will produce a stream of neutrons. Neutrons are electrically neutral particles having approximately the same mass as hydrogen nuclei with an energy level of 4.6 MeV. The 3 1/4” CBL neutron detector will record only thermal neutrons in the .025 eV energy range. The neutron source used in the 3 1/4” CBL is a chemical mixture of americium 241 and beryllium. The americium decays and emits large quantities of alpha particles. Alpha particles are double ionized helium nuclei, consisting of two protons and two neutrons. These alpha particles then collide with the intermixed beryllium causing the beryllium to emit medium energy neutrons. The 3 1/4” CBL Neutron is a single detector type and is only used as a correlation type log. It is useful in areas where the GR is non definitive for formation correlation and to indicate possible gas zones.

Neutron Primary Calibration The Primary Calibration is the API PIT at the University of Houston, the details of the Pit are written in Section 4 of this manual. The API Neutron Unit is defined as 1/1000 of the log reading in the 19% porosity Indiana limestone section. The Shop Calibrator is the Fiberglass sleeve which has been constructed and calibrated to the API Pit.

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CBL Amplitude Calibration Principles The amplitude calibration principle is to measure the actual tool receiver signal * in free pipe of known outside diameter and to compute a constant which will convert the measured response to the reference (Amplitude Calibration Standard) free pipe signal value for that diameter of casing. The relationship between the 3' receiver signal amplitude (in millivolts) and steel casing outside diameter (in inches) is derived from an article in the May, 1963 Journal of Petroleum Technology” Cement Bond Log A study of Cement and Casing Variables”. Tool Receiver Signal =

−0.6044 201.54( in mv) ∗ O. D. ( inches)

* "Tool receiver signal" is the signal, in millivolts, measured directly at the output of the receiver transducer. Exact primary calibration reference (or Amplitude Calibration Standard) values for some typical casing outside diameters are: Casing O.D. (inches) 4.50 5.50 7.00 8.625 9.625 13.375 Calibration Standard (mV)

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71.93

62.17

54.80

51.28

42.04

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CBL Travel Time Calibration Principles To calculate first arrival travel time: (pipe I.D. - tool O.D.) X (15.75) + (spacing X 57) + Lt = Travel Time I.D. = Casing I. D. O. D. = Tool O. D. 15.75 = Fluid Travel Time per inch (189 µs per ft in fresh water) Spacing = Distance from Xmitr to Rec in feet (3’) 57 = Sound velocity in steel (57 µs per ft) Lt = Tool constant ( travel time from Xmtr Xtal to tool O.D. + travel time from tool O.D. to Rec Xtal) use 70 for 3 1/4” CBL tool Using an angle of 17 degrees at Xmitr and Rec Xtals TYPE OF FLUID Fresh Water Salt Water Oil

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TRAVEL TIME 210 189 240

CHLORIDES PPM 200,000 ppm

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AMPLITUDE AND TRANSIT TIME DETECTION METHOD

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EXCELL 2000-A determines pipe amplitude and transit time values from the same reference point on E1. The figure below will be used to describe the method of transit time measurement. The EXCELL 2000-A measurement technique does not allow for transit times or amplitude readings to be taken from any signal other then E1.

Travel Time

0

AMPLITUDE

Window

100

1000 TIME

Figure 0–4

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Peak Amplitude Detection A positive going waveform arrival (usually E1) is selected to read amplitude from. A gated interval is marked on the waveform. Then a fixed marker is set on the peak of E1, which is dependant upon casing size, weight, wellbore fluid, and particular tool type. The gated portion of the waveform is scanned from this marker to determine the maximum amplitude sampled within this "window". The maximum amplitude is determined by interpolating the data within the window to determine peak position. Only positive going arrivals are used from this window.

Peak Transit Time Detection The fixed marker set in the peak amplitude detection setup is also used to determine the transit time to E1. The peak is determined by interpolating the data sampled in the 10 µsec "window" and measuring transit time from transmitter fire to this peak. A discrimination (threshold) level is set to serve as a signal level cutoff. If E1 signal drops below this level, the transit time value will automatically default to the maximum transit time scale for the curve plot: it will not be allowed to accidently trigger on the fore-runner or any subsequent arrival other than E1.

Acoustic Waveform Digitization EXCELL 2000-A digitizes both the 3 foot and 5 foot receiver signals. The 3 foot receiver signal is digitized for 100 µsec at 1 µsec intervals and saved to disk. The 5 foot receiver signal is digitized for 500 samples at 4 µsec intervals and saved to disk.

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Tool Calibration Principles Standard Two-Point Linear Calibration The terms "Gain" and "Offset" appear in the calibration report or "tail" for the EXCELL 2000-A log. The Gain and Offset are numerical values that define a straight line calibration through two known points.

Gain The Gain is the slope of the line between the two calibration points. It is a conversion from tool values to engineering units. The tool values are sent to the system computer by the logging device during the calibration process. The numerical values of the Gain and Offset displayed by the computer will be rounded off. The example above displays more significant digits than will be displayed.

Offset This is the tool value that would be obtained at zero engineering units. Since it is not always possible to calibrate at zero engineering units, the Offset is calculated from the straight line equation and the Gain. The Offset tells us the offset in tool value that is present when engineering units are zero. The Offset is given by: Offset = (Tool Value) - ((Eng. units) x (1 / Gain)) The numerical values of the Gain and Offset displayed by the computer will be rounded off. The example above displays more significant digits than will be displayed. Note: The Gain and Offset are the results of a calibration that allows conversion of TOOL VALUES to ENGINEERING UNITS, where tool values are the output of the downhole service system (such as millivolts or counts per second). Engineering units are defined as the results displayed on the log that have been calculated and calibrated, and are displayed in units such as microseconds or API units. Linearity - The two-point calibration assumes a linear response (straight line) from the logging sensor downhole. If the response is not a straight line, then additional processing is required by the computer. One example of this is a Temperature Tool that has equations built into the software. Another example is a Pressure Tool, which may use operator input to the software equations to calculate pressure. Additional processing is

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applied after the Gain and the Offset are known from the twopoint calibration.

Calculating Log Results Log Results values are calculated in Engineering Units. Results that are calculated from the TOOL VALUES acquired during logging are computed by the system using the equation shown below. For each Tool Value point, the computer applies the Gain and the Offset to the straight line equation and calculates a corresponding CALIBRATED ENGINEERING UNIT. Any additional processing required, such as additional linearizing of the sensor response, is applied next. The linearized, calibrated data is displayed on the log mat. The equation used for calculation is: Engineering Units = (Tool Value - Offset) x Gain These gains and offsets calculated during the Shop calibration are stored in the system computer. When the tool data arrives at the computer during the survey, the gains, offsets and tool data are substututed into the equation shown below to solve for m and produce the calibrated outputs. The simple representation of the calculation method is shown below: y2 − y1 m= x 2 − x1

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GR Shop Calibration Summary

Figure 0–5 Gamma Ray Calibration Summary

The MEASURED and CALIBRATED columns contain converted API Units. Data in the TOOL VALUE column of the calibration report contains the averaged raw gamma ray counts read from the tool during the Background, Background pulse Blanket readings taken during the calibration process. The API CONVERSION FACTOR is the computed Gain value that is used to adjust the tool values to the Input Signal Reference value input by the operator. In the STD DEVIATION column is the amount of count deviation recorded during the calibration time.

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CBL Shop Calibration Summary

Figure 0–6 CBL Calibration Summary

The EXCELL 2000 CBL Shop Calibration Summary is similar to the GR Cal Summary format but with the data collected from the CBL shop calibration process.

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Block Diagrams A Cement Bond Log combination tool (CBL) is used to simultaneously run a cement bond log, a gamma ray log, a neutron log and a casing collar log. In its simplest form, a combination tool could consist of a CCL device, a gamma ray detector, a neutron source/detector and a sonic device capable of generating sonic pulses and detecting the travel time of the pulses as they pass from transmitter to receiver through the formation. The sonic return signal may be recorded as a continuous waveform or as an intensity pattern to allow additional interpretation of the bond log. The 1 11/16” Cement Bond Log combination tool consists of a multisection tool composed of a CCL section;, upper electronics, lower electronics section, an isolator section containing the receiver coils and , below the receiver section is the section containing the transmitter;. Two receivers are located in a special isolator section which prevents the transmitted signal from passing down the tool to the receivers. The 1 11/16” GNT may be added to the bottom of the CBL tool to provide the GR and Neutron data for correlation. When the GNT is added to the tool string the CCL signal in either the CBL or GNT must be prevented from occuring.

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Tool Specifications DIMENSIONS AND RATINGS o

Max Temp: 350 F Max Press: 20,000 psi Max O.D. 3.25 in Min Csg/Tbg ID: 4 in Length(W/O Neu) 16.83 ft Max Csg/Tbg ID: 13.38 in Length (W Neu) 18.0 ft Weight: 245 lbs *The length does not include any centralizers, usually 3 to 5 in line or slip-over centralizers are required.

BOREHOLE CONDITIONS Borehole Fluids: Salt ¦ Fresh¦ Oil ¦ Air Recommended Logging Speed: 30 ft/min Tool Positioning: Centralized ¦ Eccentralized

HARDWARE CHARACTERISTICS Source Type: One 20 - kHz Magnetostricitve Sensor Type Two 20 - kHz Magnetostrictive Sensor Spacings: 3, 5 ft Firing Rate: 64 ms Digitizing Interval: Waveform Length: 2.5 ms Recording Time: 2.5 ms Combinability: None

MEASUREMENT Sonic Waveform E1 Peak Amplitude Principle Sonic Wavetrain attenuation Range 0 -2500 µs 0 - 100 mV Vertical Resolution 5 ft 3 ft Depth of na na Investagation Sensitivity na < 1 mV Accuracy na ± 4 mV Primary Curves: Amplitude, Travel Time, MSG Secondary Curves GR, CCL & Neutron

CALIBRATION Primary: API CBL Test Facility Secondary: Pressure Test Pit of Free Pipe Wellsite Verifier: Free Pipe

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Casing Collar Locator Section The casing collar locator section detects the presence of a casing collar. When the magnet passes the thicker portion of the casing, the magnetic lines of force are disturbed, setting up a slow dc shift on the line voltage. Casing collar location data is used for precise depth correlation.

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Gamma Ray Section The gamma ray section of the tool counts the number of gamma rays present in the logged formation. The scintillation detector offers outstanding temperature and shock resistance along with high-amplitude pulses. Since the level of gamma rays occurring in different natural formations is well known, detailed formation data can be derived from these logs, aiding in lithology correlation.

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Cement Bond Section The bond section primarily determines the quality and extent of the physical bond between the casing and the surrounding cement sheath. The function of the bond circuit relates to the difference in sound transmission between free pipe (pipe not bonded to cement) and pipe partially or totally cement bonded. The sonic section measures travel time of sonic pulses from the transmitter to the receiver. The travel time is related in a known fashion to the type of formation between the cement sheath and the surrounding formation. Bond logs are enhanced by the use of photographic recordings of either the complete sonic wave shape or by transforming the amplitude peaks of the wave shapes into equivalent intensity patterns (VDL). This information is useful in interpretation of structural anomalies in the surrounding formation.

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Neutron Detector Section The combination tool may be run with or without the neutron section. If the neutron section is not to be used, it is recommended that it be removed and replaced with the bull plug. This will prevent accidental over-current conditions. When installed, the neutron section uses a 5 curie Americium 241-Beryllium source. Neutrons are emitted from the source at a speed of about 107 meters per second. As they collide with the nuclei in the formation, they lose speed until they are traveling at about 2000 meters/second. At this speed, called "thermal", they are either captured in the formation and lost, or captured in the detector and counted. The Helium-3 neutron detector is insensitive to captured gamma rays. The atom most effective at slowing the neutron in a collision within the formation is the hydrogen atom, since the single proton of the atom is very nearly the same size and mass as the neutron. Therefore, a high concentration of hydrogen

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in the formation will cause a low count rate at the detector. low hydrogen concentration in the formation produces a high detector count rate. Most formation hydrogen exists in water and oil. Therefore, the count rate is inversely proportional to the amount of fluid-filled pore space (porosity). The presence of gas represents a special case, and when formation porosity is known, a neutron log can be used to identify gas. The neutron log is used as a depth correlation curve when the gamma ray curve is featureless. The purpose of the correlation curve is to establish the depth relationship between open hole logs and casing collars. This allows a perforating gun, which is normally run with a collar locator on top, to be positioned accurately from the zone to the nearest casing collar, instead of from the surface. The combination CBL tool provides depth correlation and cement bonding information on one run through a wide variety of formation conditions.

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Gamma Detection Gamma radiation is measured in terms of events per unit time. An event occurs when a gamma ray is absorbed by the detector. The GNT-AD tool treats all events equally; it makes no distinction between low and high energy gamma particles. This unit detects gamma pulses in a like manner to other gamma tools. Gamma rays are first detected with a NaI scintillation crystal which emits light-photons. These light pulses are then converted to an electric pulse by a photomultiplier tube (PMT). The anode of the PMT appears electrically as an AC-coupled current source that produces negative pulses.

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SCINTILLATION DETECTORS To detect gamma rays, most gamma tools use scintillation type detectors. Figure 0–7 Scintillation Detector shows the basic components of a typical scintillation counter (detector). A scintillating transparent crystal, normally sodium iodide, is optically coupled to a photomultiplier tube. The crystal will give off a minute burst of light when struck by a gamma ray. The photon energy (light) strikes a photo-sensitive surface or cathode causing electron emission. The electrons so produced are accelerated to an anode which upon impact, releases additional electrons which are directed to another anode. Those anodes are called Dynodes and they are Supplied with progressively higher voltages by an internal or external resistor divider chain. there are several stages of such multiplication which finally yield a sufficiently high flow of electrons to be measured and recorded as an indication of the incident gamma ray radiation. Proper manipulation of this electronic signal results in a voltage signal that is nearly proportional to the energy deposited in the crystal by the detected photon.

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The Scintillating Crystal The operation of the scintillation detector depends on the fact that certain materials, called phosphors, emit visible light when struck by particles (e.g. photons). The mechanism by which this happens is a well understood quantum phenomenon that involves pair production, Compton scattering and photoelectric effects. As a photon enters the crystal it produces electrons and positrons by the above interactions. These particles excite the crystal into generating flashes of light (scintillation’s). The sum of the intensity of these scintillation’s is related to the energy deposited in the crystal by the bombarding photons. The light flashes fall on the photocathode surface of a photomultiplier tube, liberating electrons via the photoelectric effect. The tube amplifies the electronic charge and provides a voltage signal strong enough to be analyzed.

Figure 0–7 Scintillation Detector Gamma Ray

γ

Optical Coupling Grease

ee-

P eePhoto-Cathode

Scintillating Crystal

eVacuum Tube

Photo-Multiplier Tube

The output voltage pulse from the photomultiplier tube is very nearly proportional to the energy of the photon that initiates scintillation in the crystal; then not only can photons be detected with a scintillation detector, but also their energies can be measured.

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9–25

1 11/16" Cement Bond Tool

The Photomultiplier Tube (PMT) The two major elements of the PMT are the photocathode and the electron-multiplier structure (Dynodes). The photocathode can be made sensitive to almost any region of the electromagnetic spectrum. For logging tools we are interested in having PMs with peak sensitivities around 400 nano-meters (109 m) (blue) to match the emission spectra of the NaI(T1) scintillation crystal. The electron multiplying network (through the process of secondary emission) greatly increases the number of electrons with each dynode stage. A typical scintillation pulse will give rise to 107 - 1010 electrons.

20

Neutron Detection The 1 11/16” GNT neutron detector section contains a helium (He3) four-atmosphere proportional counter: a (1” x 4”) detector. The signal conditioning board consists of an amplifier and discriminator, and a high voltage regulator. When a neutron strikes the detector, the detector assembly responds by producing a voltage pulse.

21

Thermal Neutron Detectors To detect thermal neutrons, He3 gas proportional counters are used. These are cylindrical tube type detectors that belong to the ionization chamber family. Neutrons interact with the Helium-3 nucleus according to the reaction: Equation 1: 1 0

9–26

n + 23He →

EXCELL 2000-A Downhole Tools

H + 11H + (0.765 MeV )

3 1

30-Apr-02

1 11/16" Cement Bond Tool

The triton ( 3H ) and proton ( 1H ) are the products that ionize the gas. They share the reaction energy of 0.765 MeV and as these positive charges move through the gas, ionization occurs which causes a stream of electrons to flow to the center high voltage anode, refer to Figure 0–8 He3 Detector. Figure 0–8 He3 Detector

3

He

Anode

The streaming electrons will collide with orbital electrons Cathode causing secondary ionization. This increased electron flow accumulates at the anode and moves on in the form of current to cause a pulse outside the counter. The pulse height is proportional to the energy of the neutron that initiated the ionization process. A thermal detector is essentially 100% efficient for thermal neutrons when He3 gas pressure is four atmosphere or above.

Casing Collar Locator The casing collar locator section detects the presence of a casing collar. When the magnet passes the thicker portion of the casing, the magnetic flux lines are disturbed. This sets up a low frequency dc voltage shift on the wireline voltage. Casing collar data is used for precise depth correlation.

30-Apr-02

EXCELL 2000-A Downhole Tools

9–27

1 11/16" Cement Bond Tool

BLOCK DIAGRAM ANALYSIS CAUTION Assembly and disassembly should be performed as per print 001-3100-211 (707.01024). ONLY 1-1/2" open end wrenches should be used with this tool. DO NOT use "Cheaters" or long wrenches.

22

Mechanical Standard 4-1/2", 5-1/2" and 7" rubber standoffs may be used on this tool with adapters 707.00982 (3 sets required and installed at the three standoff subs on the tool). A standoff tool (001-0001-000) should be used to install and remove these standoffs. Production logging centralizers may be used at the top and bottom of this tool. If a GR Neutron tool is run without the Neutron being required, a third PL centralizer may be run in place of the source spacer. Each transducer (the two receivers and the transmitter) has a piston/oil compensation system which compensates for thermal expansion of the oil to temperatures greater than 420°F (tool operating limit is 375°F). Fill the three cavities with Dow Corning 200 silicon oil. The oil levels are self calibrating and internal at each transducer housing. NOTE Extra care should be taken with the O-rings when installing or removing the plugs. The four socket head cap screws (1/4-20 x 1/4") between the 5' receiver and the spacer housing should be checked before and after each job. The isolator is the weakest point on the tool. DO NOT allow bending forces at the isolator beyond the weight of the 1-11/16" CBL tool, the 1-11/16" GR/Neutron tool and centralizers. Combined tool weight may bend or break the isolator.

23

9–28

EXCELL 2000-A Downhole Tools

30-Apr-02

1 11/16" Cement Bond Tool

Special Features - Mechanical CCL - The "CCL" amplifier is contained in the bottom sub of the CCL assembly. It is completely self contained and operates independently of the rest of the tool. Its power requirement is 6 mA at 100 Vdc. Upper Electronics - This electronics section consists of logic, power supply, line driver, preamp-filter and GR/Neutron anticoincidence boards plugged into a Motherboard. Spacer Harness - The spacer harness which is located in the spacer housing has orientation designations ("Top" and "Bottom" of tool) which must be aligned when assembled. (Threaded strain-relief sections are used at each end to prevent vibration from causing the plugs to disconnect.) Isolator - The rubber inserts are provided for additional strength in the isolator and to give the tool a uniform diameter (111/16"). If this section becomes "gas cut" it will not affect the operation of the tool whatsoever. Transducer Housings - The housings which protect the transducers (receivers and transmitter) are similar to those housings which protect the electronics and are therefore unaffected by well pressure and most well conditions ("gas cut" mud, etc.) along with the electronics. The oil is only used to acoustically couple the signals to the transducers. The oil is not used to compensate for well pressure. Oil fill should be done with vacuum fill system.

24

Electronics This CBL tool was designed to operate with the 1 11/16" Gamma Ray/Neutron tool (GNT-AD) attached to the bottom. No gamma ray should be attached above the CBL-FB. NOTE When connected in this manner, the CCL in the GR/N tool will not pass signals to the logging line. It is disabled and is not used.

30-Apr-02

EXCELL 2000-A Downhole Tools

9–29

1 11/16" Cement Bond Tool

The output of some GR/N Tools in the field may be insufficient to trigger the GR/Neutron circuit in the CBL tool. Their output amplitude may need to be slightly boosted. The primary acoustic frequency of this tool is approximately 34 kHz, which may appear compressed on the VDL. This tool must be run centralized. For acoustic reasons. 7" diameter pipe is the maximum recommended size. This tool also has the ability to select two levels, "high gain" and "low gain", from the surface to optimize signal levels for various well conditions. To select this feature, the tool head voltage must be lowered to approximately 84 Vdc (from the 100 Vdc nominal) for the automatic selector to function. At a period of approximately 8 to 10 seconds, the gain will alternate between its two levels. This allows the operator to view the signal and determine the range needed for a job. To disable the automatic sequence, simply adjust the tool head voltage back to 100 Vdc during the period in which the signal is in the acceptable range. Do NOT forget the voltage drop in the line. The CBL tool operates at 100 Vdc and switches at 84 Vdc at the top of the tool, not at the surface. Do NOT lower voltage below the point where the transmitter stops firing, i.e. below 84 Vdc. NOTE Some distortion will appear in the signal at 84 Vdc. The signal will return to normal when the head voltage is restored to 100Vdc. The Lower Electronics contain all of the transmitter power and firing circuits. The transmitter firing pulse is adjusted to approximately 350 Vdc (it requires 190).

25

9–30

EXCELL 2000-A Downhole Tools

30-Apr-02

1 11/16" Cement Bond Tool

Simplified Block Diagram The CBT-FB is a monocable tool which requires tool power and signals to be present simultaneously on the wireline. Signals are applied to the logging line by transformer T1 on the motherboard. The transmitter fires and a sync pulse pair is produced every 64 milliseconds that the tool is powered over 84 V at the head. The transmit-receive cycle is considered to begin 4 milliseconds before the transmitter fire. During the first 4 milliseconds of each cycle, the receiver gates are OFF to produce a quiet state ready to receive the return waveform. After transmitter fire, the receive gate is ON for 2 milliseconds. Following the return to OFF of the receive gate, there is a dead time of 2 milliseconds before the gamma ray gate is turned ON. The gamma ray gate remains open for 56 milliseconds.

26

Casing Collar Locator: CCL signals are developed by a magnet and coil combination when the tool passes a change in magnetic permeability. The signal from the coil is amplified by the board in the lower sub of the CCL asssembly. The signal is then applied to the line by way of a current amplifier.

27

Power Supply: The power supply provides stepped down dc power for the analog and digital circuits. The 100 Vdc at the head of the tool is applied to a chopper circuit that converts the dc into ac. That ac is fed to the primary of transformer T1. Three secondaries from that transformer feed three full wave rectifiers. Their outputs are +5 and -5 Vdc for the digital logic circuits, +15 and -15 Vdc for the op amp analog circuits, and +30 Vdc for the logic board to produce the SCR trigger to fire the transmitter.

28

Transmit/Receive Logic: A 32 kHz oscillator provides the base frequency for use in the logic circuits. Its frequency is adjustable. Receiver timing is developed. The Gamma Ray/Neutron gate is developed. A transmiter timing pulse is generated every 64 milliseconds. Sync control signals are generated.

29

30-Apr-02

EXCELL 2000-A Downhole Tools

9–31

1 11/16" Cement Bond Tool

Receiver Signals: Acoustic return signals are picked up by the 3 foot and 5 foot receivers. These signals are sent through a receiver select switch controlled by the logic board. The receiver signals are amplified and filtered. They are passed through the logic board, gated, amplified by the line driver and transformer-coupled to the logging line.

30 Gamma Ray/Neutron AntiCoincidence Circuits: The GR and Neutron pulses are taken off of the power line feeding the GR/N tool, shaped by a R-C circuit and then sent to the anticoincidence circuit. The pulses are amplified and sent through two discriminator circuits. Gamma ray and neutron pulses are not gated into the logic board until 4 milliseconds after the transmitter fire. After passing through the logic board, the pulses are amplified by the line driver and sent through the line transformer. On the line, Gamma Ray pulses are negative and Neutron pulses are positive.

9–32

EXCELL 2000-A Downhole Tools

30-Apr-02

1 11/16" Cement Bond Tool

Figure 0–9 3 1/4" CBL Timing

30-Apr-02

EXCELL 2000-A Downhole Tools

9–33

1 11/16" Cement Bond Tool

Figure 0–10

9–34

EXCELL 2000-A Downhole Tools

30-Apr-02

1 11/16" Cement Bond Tool

MU X MU L T I

C H A N N E L

MU X

J 1

M U X

J 2

D A T A

A D D R /

MU X

J 8 C T MO

C A B L E C O N T R

A / D

I N T E R F A C E

R A M P

T R I

G G E R

G E N E R A

&

P U L S E

E

5

N A

T O R

E

N C O D E R A

A C D I S C R I MI

F

R A ME / A C

I

N F O

+ 5

D I S C .

P

O S I T I V E

P U L S E

( I N F O .

D E T .

)

D I S C .

N E G A T I V E

P U L S E

( F R A ME

D E T .

)

V

B

G R O U N D

C

E

N A T O R D

D I S P L A Y I N P U T

- 1 2 V

+ 1 2 V

+ 5 V

D I S P L A Y C O N T R O L P O WE R

ACOU TRIG LINE PULSE DISC

S U P

D I S P L A Y

P L Y

1 1 5

V

I N P U T

R A MP S MO N I

T O R

T O O L

S I G N A L

M S G

L

V E L

&

MC

V E L

T E N S I O N S P A R E

A

N A L O G C C L

M C

C 1

C A B L E 4 0 0

H z

F I L T E

R

C A B L E

L O G L I N E A D 3 L E N G T H D A S - 5 0

A D 2

A / D

A D 1 A D 0

S 1

A C O U S T I C F I L T E R

A

B

OPEN

SIMULATOR

S Y N C

Figure 0–11 SOIP Diagram

30-Apr-02

EXCELL 2000-A Downhole Tools

9–35

1 11/16" Cement Bond Tool

CBL TELEMETRY

DISC.

+ Pulse

INFO.

POS. DET.

NEG. DET.

Sorensen DC Power Supply

Disc. Pot

400hz Filter Sig. Sw. Ramp Gen.

CTMO5

Pass Filter Acoustic High

AT BUS LINE

POWER PC

Buffer Memory

MTGR

MONITOR

TMI CPU

- Pulse

TMI CPU

3 1/4" CBL

M/C DECODER

FRAME

HARD DRIVE

M/C Adapter

POS Pulse

Line Length

Sig. Sim.

Neg Pulse Ramps (Scope)

Figure 0–12 CBL Telemetry

9–36

EXCELL 2000-A Downhole Tools

30-Apr-02

1 11/16" Cement Bond Tool

HARDWARE CONFIGURATION The instructions that follow address the configuration of the EXCELL 2000A system to perform a monocable 3 1/4” Cement Bond Tool service NOTE: The following is a list of the physical switch positions to power the computer sub-system devices. This order can be changed except for the Rack-Mounted Work Station (RWS) it should always be powered last to protect the device and ensure that all the perphial devices will be available for use by the software after the boot-up sequence.

This completes the configuration of the surface system to operate the 3 1/4” CBL service.

30-Apr-02

EXCELL 2000-A Downhole Tools

9–37

1 11/16" Cement Bond Tool

Boot up system 1. Locate and switch ON the system surge protection panel 1. Ensure that the Plotter is switched ON NOTE Before turning on Uninterruptible Power Supply (UPS) Check to ensure that the ON/OFF switches on all panels are switched ON 3. Locate and switch ON the Uninterruptible Power Supply (UPS) 3. All panels in the XL2000-A system should now be powered up 3. Check to ensure that all panels are powered ON 3. The Rack Mounted Workstation (RWS) should now be in the Boot-Up process 3. The display window on the RWS will display a varying three digit number code indicating Boot-Up step sequence. 3. When the 3 digit display reaches c32 (< 2 min.) the monitor will become active and display system configuration information. 3. When the Boot-Up is complete and the login window appears type hes in the upper window and press the Enter ↵ key then type hes again in the lower window.

9–38

EXCELL 2000-A Downhole Tools

30-Apr-02

1 11/16" Cement Bond Tool

Launch CLASS Logging Software 1. Make the truck launcher window active by clicking on it with the mouse. a. The truck launcher window has three Icons: (1) Swiss Army Knife - launches Desktop Petrophysics (2) Logging Truck - launches Class logging software (3) Power Drill - launches Utilities 2. To launch Class logging software and begin a logging session: a. Highlight the logging truck icon in the Truck Launcher window by using the Up/Down arrow keys and double click on it with the mouse, or after highlighting the logging truck Icon press the Enter key. 3. A login window will be displayed for the operator to type in his name. The name typed in will be written in the system event file and on all shop calibrations performed during the session. ENTER NAME OF LOGGING ENGINEER Name: [ ] a.

30-Apr-02

Type in the operators name and press the ENTER key.

EXCELL 2000-A Downhole Tools

9–39

1 11/16" Cement Bond Tool

The EXCELL-2000 MAIN MENU screen is displayed. The following options are available from the main menu. 1. 1. 1. 1. 1. 1. 1.

MAIN MENU LOGGING SETUP RELOG SETUP REPLAY SETUP CALIBRATION ONLY SYSTEM UTILITIES SYSTEM INSTALL [eng] EXIT EXCELL-2000 SYSTEM

4. Select option number 1 LOGGING SETUP by using the UP and DOWN Arrow keys to highlight and press the ENTER key. 4. The LOGGING SETUP menu will be displayed with the following options. 1. 1. 1. 1. 1. 1. 1.

LOGGING SETUP SERVICE SELECTION API LOG HEADER DGR/DISPLAY SETUP TOOL CALIBRATION TAPE INIT SETUP OPEN JOB LOG FILE LOG - PREVIEW - TEST

6. Use the UP and DOWN Arrow keys to highlight option #1 SERVICE SELECTION and press the ENTER key.

9–40

EXCELL 2000-A Downhole Tools

30-Apr-02

1 11/16" Cement Bond Tool

Select Tool Service Configuration In order to prepare the system to Calibrate the operator must load a Tool Service ConfigurationThe EXCELL 2000 System keeps a list of the most recently used tool services. If the service to run has been used within the last 14 services run it will be displayed in the entry table. The user may highlight the desired tool service press the Enter Key and the system will load the service selected.

30-Apr-02

EXCELL 2000-A Downhole Tools

9–41

1 11/16" Cement Bond Tool

The system tool service tables may be accessed by blanking out any tool service type and pressing the F11 Key. By repeatedly pressing the F11 Key the system will toggle through the various tool service tables. The default configuration may be used or if a local configuration exists it may be used.

A SERVICE & TOOL CONFIGURATION table will be displayed. If a tool service has not been selected during the current session the service number field will be blank A default tool service must be loaded first then the operator may edit it to match the tool configuration that is to be run. A default tool service may be recognized by its name which will have only four numbers in the first field provided for naming. The first step in this process is to use the Up Arrow key to highlight the SERVICE: SRV area of the screen and type in 6284 which is the CLASS tool service number for the 3 1/4” CBL tool

9–42

EXCELL 2000-A Downhole Tools

30-Apr-02

1 11/16" Cement Bond Tool

When the system completes loading the selected tool service it will display a screen showing the default tool string. The tool string displayed MUST be exactly the same tools and order as the physical tool string to be ran.

If required edit the tool string to match the actual tool string being used. If the Neutron sub is not in the tool string delete it from the MNENOMIC SERIAL# column. When finished exit by pressing the Escape Key and answer Yes to the quiry “EXIT SERVICE CONFIGURATION?”.

30-Apr-02

EXCELL 2000-A Downhole Tools

9–43

1 11/16" Cement Bond Tool

PRIMARY CALIBRATION The amplitude calibration principle is to measure the actual tool receiver signal* in free pipe of known outside diameter and to compute a constant which will convert the measured response to the reference (Amplitude Calibration Standard) free pipe signal value for that diameter of casing. The relationship between the 3' receiver signal amplitude (in millivolts) and steel casing outside diameter (in inches) is derived from Fig. 8 of the article "Cement Bond Log - A study of Cement and Casing Variables" in the May, 1963 Journal of Petroleum Technology. (-0.6044) Tool Receiver Signal = 201.54 * O.D. [mV]

[inches]

Exact primary calibration reference (or Amplitude Calibration Standard) values for some typical casing outside diameters are: Casing O.D. (inches) 8.625

4.500 9.625

5.500 13.375

Calibration Standard (mV) 81.20 71.93 54.80 51.28 42.04

7.000

62.17

The Cement Bond Tool receiver geometry is equivalent to that of the competitor tool referred to in the above article, and we assume a constant ratio between the amplitude of E1 and the amplitude of E2 which is typically used when logging the 1 11/16" CBL tool. The primary calibration standard is a steel casing calibrator as a primary reference, some locations have for convenience (size and weight) a secondary calibrator that is constructed of aluminum. Several CBL tools were first calibrated to the primary standard and then had their response measured in the secondary calibrator in order to establish a secondary calibration standard. "Tool receiver signal" is the signal, in millivolts, measured directly at the output of the receiver transducer.

Enter tool data:

9–44

TOOL

TYPE

LENGTH

OPTIONS/REMARKS

CCL

UN

19"

CBL-FB LENGTH = 148.5" = 19"(CCL) + 129.5"(CBL) UN = unspecified; need to specify length

EXCELL

2000-A

DOWNHOLE

TOOLS 1-Aug-01

1 11/16" Cement Bond Tool

CBL

FB

129.5"

X-mitter Delay : 0 µsec Waveform Mode : VDL

CENT

IN LINE

26.5"

Verify this length; 2 different length PL centralizers exist; other size is 21"; "CEN" or "CENT" are alternative mnemonics

GR

AA

38"

Scintillation GR, 350°F rating, part of GNT-AD 38" = 27" GR + 11" CCL No "AD" type GR exists; need to specify length

NEU

AA

48"

48" length is for "13 inch" neutron spacing with G-series source; GNT = 86" = 38" GR + 48" Neu

Enter the correct serial numbers. CCL and CBL will have the same serial number; GR and NEU will have the GNT serial number.

1-Aug-01

EXCELL 2000-A DOWNHOLE TOOLS

9–45

1 11/16" Cement Bond Tool

TRANSMITTER FIRE DELAY (0 µsec for 1 11/16") is the time between sync pulse and transmitter firing in the downhole tool. CORRECTIONS TO DEFAULT DEPTH OFFSETS MAY BE NECESSARY! Be careful to account for any in-line centralizers used. Assuming one 26.5 inches centralizer between CBL-FB and GNT-AD: SENSOR

DEPTH OFFSET IN INCHES

GR

75

NEU

18

TT3

166

AAMP

166

AMP

166

WF3

166

WF5

178

CCLR

252

CCL

252

1 11/16" Tool The receivers on the slimhole CBL are piezoelectric and do not require polarization. Connect the CBL tool sections: Top 48" CCL / UPPER ELECTRONICS Middle 69" RECEIVERS / ISOLATOR / TRANSMITTER Bottom 31" LOWER ELECTRONICS Be Careful! The electronics must rotate inside the pressure housing for both the upper and lower sections. The middle section must not be opened at the wellsite. From above the 5 foot receiver to below the transmitter, inclusive, the tool must remain intact. While the toolstring is horizontal, the Gamma Ray (part of the COSMOS GNT) may be attached for checkout. Ideally, it should be removed before hoisting the CBL from horizontal to 9–46

EXCELL

2000-A

DOWNHOLE

TOOLS 1-Aug-01

1 11/16" Cement Bond Tool

vertical. If the CBL and GNT are hoisted together, hold up the middle of the toolstring in order to not bend the acoustic isolator. This acoustic tool requires good centralization. Three centralizers, or two centralizers at the ends and a standoff in the middle, should be considered the minimum to provide good centralization. Fit the rubber standoffs to the tool with adapter 707.00982. Use the special tool to assist installation of the standoffs, but avoid contacting the transducers. If the Neutron log is not required, the neutron source sub may be removed to enable attaching a centralizer at the very bottom of the toolstring. Remember to correct depth offsets if in-line centralizers are installed.

Tool Power UP Monitor the voltage at the head of the tool. The CBL-FB (1 11 /16") draws approximately 40 mA with 100 volts at the head of the tool. This is about 10 mA less than the large diameter CBL. With the GNT attached at the bottom, the pair draw 100 mA with 100 Vdc. Listen to the transmitter to confirm that it is firing. View the scope signal to setup the sync pulse height, gate width, and gamma ray discrimination level.

GR Calibration Gamma Ray Calibration and Verifications are performed exactly as done with the 1 11/16 GNT. Position the Gamma Ray calibration Blanket on the GR detector of the GNT pressure housing (not the middle, CCL, pressure housing) with the Up Arrow toward the UPHOLE end of the tool. Select Gamma Ray curve and Perform Calibration. If the API standard for GNT-AD scintillation is correct, Continue. The counts seen in the calibration screen are tool values and not API counts. Monitor the background count rate to confirm that the tool is working. If the count rate is too high (greater than 100 for GNT-AD scintillation when averaging), stop the calibration. Check that radioactive sources are away from the tool (many times it is easier to move the tool). Restart the background counts if necessary.

1-Aug-01

EXCELL 2000-A DOWNHOLE TOOLS

9–47

1 11/16" Cement Bond Tool

Place the calibration Blanket on the tool, clear all personnel at least 6 feet away from the tool and start background + Blanket check. If the count rate is out of tolerance, stop the averaging. Investigate the problem (perhaps another source has been introduced to the area), then restart the if necessary. When sampling is complete, the tool values and calculated Gain and Offset values will be displayed (if an Offset other than zero is shown recalibrate). Check that the Gamma Ray sensitivity (cps/API) is within tolerance. If the calibration is within tolerance, make a hardcopy and Save the Calibration to Disk. Remove the blanket from the tool and return to the appropriate storage area.

CCL Check Begin Time Drive. Slide a metal object (for example, a Cspanner) along the outside of the CCL. Observe the deflection of the CCL curve. The CCL signal will be processed thru the Cable Shooting Panel (CSP1-A) as a DC analog signal. The Amplifier adjust control on the front of the CSP1-A will adjust the gain of the CCL signal sent to the EXCELL 2000-A Operator Interface Panel.

Neutron Shop Calibration Place tall toolstands (≈ 3 feet high) under the CBL/NEU. The downhole end of the tool (the Neutron section) should extend ≈ 4 feet beyond the stand so that the fiberglass calibration sleeve may slide over the tool. At the uphole end of the tool, use rope or duct tape to tie down the tool to the tool stand to prevent tipping when the calibrator is installed over the downhole end. The Neutron Shop Calibration is performed exactly the same as when calibration the Neutron on the 1 11/16” GNT. Leave Curve Value #1 BLANK and read the Background. Monitor the background during reading there should be < 5 neutron cps. Input 1000 for Curve Value #2. Slide the calibration sleeve onto the tool. Install the 5 Curie Am Be source. Position the bottom end of the calibration sleeve 3 5/8" uphole from the bottom of the neutron source.

9–48

EXCELL

2000-A

DOWNHOLE

TOOLS 1-Aug-01

1 11/16" Cement Bond Tool

Perform the collect data to begin the sampling for background + calibrator for a SHOP Calibration. The counts should now be ≈ 800 in curve value #2 window.

Log Presentation Header. 5" (or 1/200) scale of CBL Main Log with comment 5" (or 1/200) scale of CBL Repeat Section with comment Parameter Identification Table Filter and Delay Table Tool Calibrations Customer Event File Tool Picture Wellbore Diagram

1-Aug-01

EXCELL 2000-A DOWNHOLE TOOLS

9–49

1 11/16" Cement Bond Tool

Example Log Heading

9–50

EXCELL

2000-A

DOWNHOLE

TOOLS 1-Aug-01

1 11/16" Cement Bond Tool

Example Log Data Table

1-Aug-01

EXCELL 2000-A DOWNHOLE TOOLS

9–51

1 11/16" Cement Bond Tool

Example Upper Insert & Main Log

9–52

EXCELL

2000-A

DOWNHOLE

TOOLS 1-Aug-01

1 11/16" Cement Bond Tool

Example Lower Insert & Main Log

1-Aug-01

EXCELL 2000-A DOWNHOLE TOOLS

9–53

1 11/16" Cement Bond Tool

Example Tool Calibrations

9–54

EXCELL

2000-A

DOWNHOLE

TOOLS 1-Aug-01

1 11/16" Cement Bond Tool

Calibrate the Line Load System. Attach standoffs and centralizers as appropriate for the casing to be logged. Rig up the tool. Care must be taken not to bend the isolator excessively. If practical, connect the GNT to the CBL vertically. Zero reference point of the tool is at its bottom (neutron source or bottom of lowest part of the tool). Align the zero reference point of the tool with the zero reference point of the well. Go to the Log Mode, input correct Depth in the Depth field and set the mechanical Depth counter.

Downhole Operational Checks & Verification Proceed downhole to a location with free casing. Check that the Amplitude curve response indicates free pipe but does not exceed the maximum value (mV) for the casing being logged. Keep in mind that Temperature, Fluid Type and Pressure will all affect the Amplitude signal. Log down from the calibration depth (in free casing) to TD depth and watch response of all curves. Run all CBL's at 30 fpm.

Repeat Section Standard practice is to run a preliminary repeat section over a zone of approximately 200' showing both bonded and free casing. By running a preliminary repeat section in free casing, which will show the casing arrivals very distinctly on the MSG, a sample log is available before descending into bonded casing, to assist in recognizing "fast formations". In a fast formation, the amplitude curve is not sampling the first arrival, but some later arrival that is often large. If these large amplitude readings are not recognized as fast formations, the bonding of the cement may incorrectly be considered poor. Make any depth adjustments necessary to tie in exactly with the reference Gamma Ray log and run a second 200' Repeat Section over the deepest portion of the well or any specified zone of interest. Verify that the second repeat section is on-depth (within ½ foot) with the reference log. Adjust CCL gain for desired output on log.

1-Aug-01

EXCELL 2000-A DOWNHOLE TOOLS

9–55

1 11/16" Cement Bond Tool

Main Run From a depth close to the casing shoe (or total depth if well is completely cased),record the Main Log up to a depth at least 200 feet above the top of cement (or to a depth of 100' if no free pipe exists). Carefully compare the Main Run with the Repeat Sections for repeatability.

Rigdown The CBL tool should be brought to surface, thoroughly washed and laid down without bending the isolator. Vertically disassemble the GNT from the CBL, if practical. Clean all threads and lightly apply lubricant to threads (NEVER APPLY DC-111 TO THREADS OR MECHANICAL COMPONENTS). Remove the standoffs from the tool string. Use the standoff tool with caution; avoid contact with transducer housings. All special items needed for the log should be returned to the appropriate location. All tools should have thread protectors and plugs.

9–56

EXCELL

2000-A

DOWNHOLE

TOOLS 1-Aug-01

1 11/16" Cement Bond Tool

1-Aug-01

EXCELL 2000-A DOWNHOLE TOOLS

9–57

1-Aug-01

EXCELL 2000-A DOWNHOLE TOOLS