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Downhole Production Logging Tools
Production Logging Fundamentals
Learning Objectives
By the end of this lesson, you will be able to:
Demonstrate the principles and operation of the logging toolsassociated with flowmeter tools
Demonstrate the principles and operation of the basic temperaturelogs
Demonstrate the principles and operation of basic radioactivetracer logs
Discuss the added value of running a downhole video log inaddition to production logs
Present the principles and operation of basic spinner flowmeterlogs
Present the principles and operation of the gradiomanometer log
Illustrate the performance of cased hole logs in single phase flow
Understand the interest of running multiple tools within aProduction Combination Tool
Blades Monitors wellbore condition (open or cased hole)
After a drilling phase, caliper data are integrated to determine the volume of the open hole
Caliper offers a qualitative indication of the condition of the wellbore and the degree to which the mud system has maintained hole stability
Very useful with any Production Logging run
The caliper measurement point corresponds exactly to the measurement point of the flowmeter impeller
Caliper
A B
Moving caliper
arm
or multi-finger types
Caliper tool: Variable resistance
Caliper arm
Variable resistor
Main Applications Limitations
1. Correct the flowmeter readings for diameter variations due to either heavily scaled tubulars or differences in open hole completions
2. Locate packer seats in open hole sections
3. Determine restrictions for future tubing or casing work (workover planning)
4. The caliper data can be used independently for determining general internal corrosion, paraffin buildup, or mineral scaling
• Normal two or four arm calipers will only give general indications of corrosion and other more sophisticated tools need to be run to examine the corrosion issues further
Blades
Caliper
A B
Moving caliper
arm
or multi-finger types
Caliper tool: Variable resistance
Caliper arm
Variable resistor
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Blades Monitors wellbore condition (open or cased hole)
After a drilling phase, caliper data are integrated to determine the volume of the open hole
Caliper offers a qualitative indication of the condition of the wellbore and the degree to which the mud system has maintained hole stability
Very useful with any Production Logging run
The caliper measurement point corresponds exactly to the measurement point of the flowmeter impeller
Caliper
A B
Moving caliper
arm
or multi-finger types
Caliper tool: Variable resistance
Caliper arm
Variable resistor
Main Applications Limitations
1. Correct the flowmeter readings for diameter variations due to either heavily scaled tubulars or differences in open hole completions
2. Locate packer seats in open hole sections
3. Determine restrictions for future tubing or casing work (workover planning)
4. The caliper data can be used independently for determining general internal corrosion, paraffin buildup, or mineral scaling
• Normal two or four arm calipers will only give general indications of corrosion and other more sophisticated tools need to be run to examine the corrosion issues further
Multi-finger Calipers• Motorized Centralizers to ensure effective centering force
– Equipped with rollers to prevent casing and tubing damage
For cased hole logging, the caliper will give indications about: • Conditions inside the casing• Damage• Scale• Paraffin deposits
• Hydrodynamic characterization of reservoirs
• Identification of production and injection intervals
Noise Log
• Well integrity analysis
Spectral Noise Logging (SNL) is an acoustic noise-measuring technique used in oil and gas wells for:COPYRIG
Spectral Noise Logging (SNL) • Records acoustic noise generated by fluid or gas flow • Tool listens passively to downhole noise such as gas bubbling up
through liquid in the wellbore– Behind pipe, a channeling flow passes through “tight spots”, which
cause higher velocities, sudden pressure reductions and significant flow turbulence
– The noise-logging tool listens for noise associated with the turbulence
• The tool includes piezoelectric crystal transducers which convert the oscillating pressure of wellbore sound to corresponding oscillating voltage
– The oscillating voltage is applied to a speaker at the surface, as well as each of four high-pass filters
• Each high-pass filter detects nothing below its filter range• Log noise filters for 200, 600, 1000 & 2000 Hz• Two-phase flow occurs at about 200 to 600 Hz• High rate single phase flow occurs above 1000 Hz• Sound is highly attenuated by gas• Tool works best for low rate gas leaks
Noise Spectrum
200
600
1,000
2,000
Differential Pressure
Single phase
Two phase
Rel
ativ
e am
plit
ud
e
Frequency, hz
Rel
ativ
e am
plit
ud
e
Frequency, hz
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High noise amplitudes indicate locations where the flow path is submitted to turbulence
The noise log has been used as an indicator of channeling behind pipe
• Flow through channel is indicated on a noise log by the presence of high amplitude noise at places where restrictions in the channel causes throttling of fluid
Flow through a leak results in a pressure drop that generates detectable noise
Filter’s output consists of positive excursions from neutral alternating with negative excursions
Amplitude is measured two ways1. Measure from peak of positive excursions to trough of following
negative excursion– “Peak to peak” amplitude
– “Standard gain” or “Standard sensitivity” recording
2. Measure from the peak of a positive excursion to neutral– “Peak” amplitude
– “One-half standard gain” recording
Noise Log Principle
Piezoelectric Crystal
Microphone
2000
1000
600
200 HZ
5.7
14.1
27.3
55.0
Millivolts
High PassFilters
Filter’s output consists of positive excursions from neutral alternating with negative excursions
Amplitude is measured two ways1. Measure from peak of positive excursions to trough of following
negative excursion– “Peak to peak” amplitude
– “Standard gain” or “Standard sensitivity” recording
2. Measure from the peak of a positive excursion to neutral– “Peak” amplitude
– “One-half standard gain” recording
Measurements• A single station measurement lasts 3 to 4 minutes• Relocating the tool requires 1 minute• Thus, the logging rate is approximately 15 stations per hour, and
a 4-hour logging run accommodates 60 measurements• 30 measurements are used for a course-measurement grid, with
successive measurements separated by 1/30th of the total survey interval
• The remaining 30 measurements are used for detailing areas of interest
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In desert conditions, surface temperature may initially decrease, reach a neutral point, and then increase
The geothermal temperature profile varies significantly from area to area, and the slope of the geothermal temperature varies from formation to formation
COOKING LAKE
Example of Geothermal Gradient
Knowledge of the geothermal temperature profile is necessary for temperature log interpretation
• Record one baseline log within a well shut-in and stabilized, before production start-up
The geothermal gradient is generally assumed to be constant when interpreting temperature logs in a given area
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Production zones may or may not be clearly identified on a temperature log
When free gas is flowing from the reservoir, pressure drawdown will induce a significant cooling of the gas in the near-wellbore vicinity due to Joule-Thomson effect
• Gas entry locations are identified by cool anomalies on a temperature log
Record a full (top to bottom) reliable geothermal gradient log (base line log) during the first Production Logging run
Routine: stabilize rate for 48 hours, log, shut in for about 24 hours
Record temperature profiles, well shut-in, at repeated time intervals
Log down and up, make re-runs (after 1-2 hrs), check log response
Analyze temperature log versus flowmeter log
Temperature profiles can be used for flow rate estimation
Document results and recommendations
Remember: in high rate gas wells, with low compressibility, the Joule-Thomson effect may be reversed and create a local heating at the fluid entry point (molecular friction effect)
Radioactive Tracer Logs
Use peak-to-peak transit time
Require precise well diagram
Techniques: controlled time and interval
Typically use iodine I-131 (8 day half-life)
Investigates only about 1 ft (0.31 m) deep outside casing
The spinner flowmeter is the most commonly used device for measuring flow profiles, both in injection and production wells.
Impeller placed in well to measure fluid velocity
• Signal period on output coil • Frequency of rotation F• Measures in rps
Characteristics• rps are filtered before recording• Spin direction is now presented on logs
Continuous Flowmeter Sonde (CFS)• Maximum Pressure (psi) 15000 (103 mPa)
• Maximum Temperature (°F) 350 (177 °C)
• Makeup Length (inches) 24.0 (61 cm)
Lower Bearing
Spinner
Pickup Coil
Upper Bearing
Electrical Connection Flowmeters must be centralized in the
wellbore so that accurate flow velocity of flow stream center can be determined
Use a caliper for accurate flow determination
To determine the minimum fluid velocity required for spinner to rotate:
1. Multiple up and down passes are made and calibration chart is developed to determine fluid flow velocity and cable logging speed
2. Spinner velocity will be at fluid conditions at the point of measurement and will need to be converted back to stock tank conditions during final calculations
Magnet
Temperature and Flowmeter Logs – Example 1
Increased flow
Dep
th
Temperature
Dep
th
Temperature Log Continuous Flowmeter
G
TM
A’
A
T’
T
P
1° C.
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Maximum Flow, bbl/d (m3/d) 1800 (286.2) 1000 (159)
Maximum Pressure (psi) 15000 (103 mPa)
Maximum Temperature (F) 350 (177 C)
Weight (lbs) Makeup Length (in) 60 (152 cm)
Maximum Flow (bbl/d)• Basket Open 2000 (318 m3/d)• Basket Closed 10000 (1589.9 m3/d)
Maximum Deviation () 60
Single phase (bbl/d) >100 (15.9 m3/d)
Qo in two phases (bbl/d) > 30 (4.8 m3/d)
Qw in two phases (bbl/d) >400 (63.6 m3/d)
Accuracy (%) 10
Exit Ports
Spinner
Hold-up Meter
Water Resistivity
Cell
DC Motor
Metal Petals
Diverter Flowmeters
Diverter/Basket Flowmeter
Basket Size Small Large
Minimum Casing, in (cm) 4 ½ (11.4) 7 (17.8)
Maximum Casing, in (cm) 7 (17.8) 9 ⅝ (24.5)
Maximum Flow, bbl/d (m3/d) 1800 (286.2) 1000 (159)
Maximum Pressure (psi) 15000 (103 mPa)
Maximum Temperature (F) 350 (177 C)
Weight (lbs) Makeup Length (in) 60 (152 cm)
Maximum Flow (bbl/d)• Basket Open 2000 (318 m3/d)• Basket Closed 10000 (1589.9 m3/d)
Maximum Deviation () 60
Single phase (bbl/d) >100 (15.9 m3/d)
Qo in two phases (bbl/d) > 30 (4.8 m3/d)
Qw in two phases (bbl/d) >400 (63.6 m3/d)
Accuracy (%) 10
Exit Ports
Spinner
Hold-up Meter
Water Resistivity
Cell
DC Motor
The most accurate of the spinner devices when low total rates and multiphase flow occurs.
• Can detect flowrates as low as 10 to 15 bbl/d (1.6 to 2.4 m3/d).
– A typical 1-11/16-in (4.3 cm) tool has a barrel ID of approximately 1.45 in (3.9 cm).
– A flow of 10 bbl/d results in a velocity of 3.4 ft/min (1.04 m/min) inside the barrel.
– Because of the limited clearance between the spinner and the barrel, this velocity is enough to overcome friction and rotate the spinner.
– A flow of 100 B/D passes through the barrel at 34 ft/min (10.4 m/min) – enough to start the homogenization of the flow.
– In a casing, a rate of 2,000 bbl/d (318 m3/d)is needed to obtain the same effect around a continuous spinner.
– The tool can be calibrated directly for such flow.
Metal Petals
Small clearance between the spinner and the ID of the barrel assures almost no diversion of flow around the spinner.
As the spinner rotates, it generates a specific number of voltage pulses per revolution.
• The pulse rate from the tool can be transmitted through the logging cable for surface recording and determination of corresponding revolutions per second.
Typical basket flowmeters are rated for 320 – 350°F (160 – 177°C) temperatures and 15,000 to 20,000 psia (103 to 138 mPa).
Maximum Flow, bbl/d (m3/d) 1800 (286.2) 1000 (159)
Maximum Pressure (psi) 15000 (103 mPa)
Maximum Temperature (F) 350 (177 C)
Weight (lbs) Makeup Length (in) 60 (152 cm)
Maximum Flow (bbl/d)• Basket Open 2000 (318 m3/d)• Basket Closed 10000 (1589.9 m3/d)
Maximum Deviation () 60
Single phase (bbl/d) >100 (15.9 m3/d)
Qo in two phases (bbl/d) > 30 (4.8 m3/d)
Qw in two phases (bbl/d) >400 (63.6 m3/d)
Accuracy (%) 10
Exit Ports
Spinner
Hold-up Meter
Water Resistivity
Cell
DC Motor
The most accurate of the spinner devices when low total rates and multiphase flow occurs.
• Can detect flowrates as low as 10 to 15 bbl/d (1.6 to 2.4 m3/d).
– A typical 1-11/16-in (4.3 cm) tool has a barrel ID of approximately 1.45 in (3.9 cm).
– A flow of 10 bbl/d results in a velocity of 3.4 ft/min (1.04 m/min) inside the barrel.
– Because of the limited clearance between the spinner and the barrel, this velocity is enough to overcome friction and rotate the spinner.
– A flow of 100 B/D passes through the barrel at 34 ft/min (10.4 m/min) – enough to start the homogenization of the flow.
– In a casing, a rate of 2,000 bbl/d (318 m3/d)is needed to obtain the same effect around a continuous spinner.
– The tool can be calibrated directly for such flow.
Metal Petals
Small clearance between the spinner and the ID of the barrel assures almost no diversion of flow around the spinner.
As the spinner rotates, it generates a specific number of voltage pulses per revolution.
• The pulse rate from the tool can be transmitted through the logging cable for surface recording and determination of corresponding revolutions per second.
Typical basket flowmeters are rated for 320 – 350°F (160 – 177°C) temperatures and 15,000 to 20,000 psia (103 to 138 mPa).
The tool is lowered to the deepest measurement depth, then opened.
After recording the measurement depth, the tool is pulled up (while open) to the next measurement depth.
The risk of diverting flowmeter getting stuck in the hole is higher than it would be for a continuous flowmeter.
• If the tool is stuck, the cable can be pulled loose and retrieved.
• If the flowmeter is stuck in casing, it may be least expensive to leave the tool in the hole.
• If the flowmeter is stuck in tubing, it may be necessary to pull the tubing.
Spinner / Flowmeter Log Guidelines
Need to achieve stabilized flow rate
Calibrate tool
Record multiple passes at various speeds
Record stationary readings above and below perforations
Record repeat runs
The method is• Best for single-phase flow• Good for oil and water two-phase flow• Questionable under liquids and gas flow• Needs additional support (software, gauges, etc.) • Questionable for hole angles beyond 70°
Document all results
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Essential recording tools for single- or two-phase flow:• Thermometer (Temperature log)
• Spinner flowmeter
• Gradiomanometer Density log
As a standard configuration downhole diagnosis tool, the CombinationLogging Tool usually includes:
• Thru-Tubing Caliper• Temperature log
• Spinner flowmeter
• Pressure log• Gradiomanometer Density log
Other logs include: • The Noise log is useful in specific applications to diagnose flow issues
• The Radioactive tracer is used in injection wells
• The Thermal Decay Time log (Pulsed Neutron) is a reservoir engineering tool to monitor water saturations over well life
All these tools provide valuable information to be analyzed by qualified analysts
Downhole Video Alternative to Production Logs
Advances in downhole video equipment now offer this measurement as an alternative to the new class of production logging measurements.
A downhole video log is a means to directly identify location of fluid entries into the well, because almost all production wells contain water through which the hydrocarbons are passing.
High rate water entries can also be detected from the image distortion caused by high levels of turbulence.
This approach is qualitative and does not fully replace production logging tools.