Production logging tools
1 - Reference, date, place
Tool Summary : Main Measurements
The selection of the tool depends on the purpose of the PLT
Each tool has its role
1. Depth Matching
1. Gamma Ray (could help to locate radioactive scales)
2. CCL
2. Flowrate computation , Completion integrity (scales)
1. Caliper
2. Centralisers
3. Single phase profiles (i.e. injector)
1. Temperature (PVT, Liquid indicator)
2. Pressure (PVT & Res. Pressure)
3. Spinner Flowmeter (fluid velocity)
4. For a Multi-phase production
1. Density measurement
2. Fluid mixture hold up tool
2
- Reference, date, place
Typical PL Tool string
Sondex
MPLT
3
- Reference, date, place
PLT Tools – Standard tools
Gamma- Ray
▪ Usually, the depth matching is done thanks to the GR log
▪ Needs to load the open hole GR
▪ Could give good indications of water source if scales are radioactives
▪ With gravel pack, Frac-Pack, the natural radioactivity is not more visible.
CCL
▪ CCL could help in depth matching if particular completion elements can be identified
▪ Perforations may sometimes
Caliper
▪ Caliper diameter is measured thanks to 2 perpendicular arms
▪ Diameter is mandatory to compute flow rate
▪ Even with an accurate completion sketch, caliper data has to be examined
▪ Scales could be observed thanks to the caliper
Centralisers
▪ To keep the tool in the middle of the wellbore is important to get a representative data (downhole
recirculation)
4
- Reference, date, place
PLT Tools - Flowmeter
In line Flowmeters
▪ small spinner
▪ good for high flowrates
▪ Mainly used as backup spinner
Full bore Flowmeters
▪ maximum spinner blade size
▪ best for wide range of flowrates
▪ For injection wells could be
replaced by turbine
Petal Basket
▪ stationary measurement
▪ good for low flowrates
▪ May affect flow regime
In line
5
Fullbore
- Reference, date, place
Petal Basket
PLT Tools – Flowmeter types
Turbine
Spinner
Fullbore Spinner
3-arm
6
Fullbore Spinner
6-arm
- Reference, date, place
Continuous
Spinner
In-line Spinner
Diverter
Flowmeter
PLT Tools – Temperature tools
Temperature is one of the most useful “auxiliary”
measurements made in production logging.
Temperature is very important as it is a good liquid indicator
in gas wells
The temperature can be more sensitive to small flows than
the flowmeters
Combined with pressure it helps compute the PVT
parameters.
SCHLUMBERGER - RTD
SPECIFICATION
RANGE
Temperature (max)
150 C
Pressure (max)
15000 psi
Range
Ambient – 150 deg c
Length
12.5”
Accuracy
1 deg C
Resolution
0.006 deg C
The response time is very important more than the resolution
itself (especially for quantitative temperature analysis)
In addition, it will detect very small fluid entries:
▪The derivative of temperature wrt depth (dT/dZ) can
be used to clarify fluid entries in complex
environments.
▪Gas entries, for example, are characterized by a
sharp reduction in temperature.
It is the only tool in the string that “sees” behind casing,
hence it can be used to detect channeling.
7
- Reference, date, place
SONDEX - PRT
SPECIFICATION
RANGE
Temperature (max)
177 C
Pressure (max)
15000 psi
Range
10-177 deg C
Length
12.5”
Response time
< 0.5 second
Accuracy
0.5 deg C
Resolution
0.003 deg C
PLT Tools - Density
Density is used to determine liquid source entry
Three technology are available on the market :
▪ Gradiomanometer
▪ Tool measure the difference in pressure between two points
▪ Nuclear fluid density tool
▪ Gamma ray absorption
▪ Tuning fork density (New technology not yet tried)
▪ Frequency measure
Derivative of pressure data gives another density log
8
- Reference, date, place
PLT Tools - Gradiomanometer
Silicon oil
r so
P2 - P1
(tool specific)
Differential
Pressure
TransducerDiaphragm
PB - PA
(friction, deviation)
Density
In gas wells, frictions are very important as dependant of fluid velocity
Despite friction gradient is supposed to be corrected, by experience, frictions are not
well corrected (uncertain parameter : roughness)
Deviation will also affect the accuracy of measurement
9
- Reference, date, place
SCHLUMBERGER - Gradiomanometer Issues
INFORMATION :
O-114 is main gas producer
(1.8 MMscfd)
Only 15 bbls/d of water at surface +
25 bbls/d of condensate can not
match such density increase
Well deviation is ~28 deg
Gradio response shows increase in
density
WATER SOURCE OR NOT?
No liquid entry indication by
temperature and water hold up
sensors
Major density increase gives
misinterpretation of water source
Friction, deviation and jetting effect
shows water source as if from this
reservoir.
Friction →
dP frV 2 S
=

dZ
8
A
f = friction factor (Re, roughness)
V = speed of fluid
S = surface contact with fluid
A = area opened to flow
ρ = density
Gradiomanometer is very sensitive to frictions, deviation and jetting
effect
Need to be confirmed by other sensors
10
- Reference, date, place
PLT Tool – Nuclear Density tool
The main advantage of the nuclear density tool is that the reading is not affected by wellbore
friction, deviations
Give a true fluid mixture density value
Based on TEPI experience, success ratio very good
Main disadvantage is the presence of nuclear source
g-ray
Direct density measurement
Count rate measured at the detector is a function of the
electron density in the fluid around the tool
Some RA Density tools measure the density in a cavity,
within the diameter of the density tool itself, and
consequently the density measurement is measured
according to the tool position in the wellbore.
11
- Reference, date, place
PLT tools - Pseudo-density
dp/dZ calculated from p vs Z
Needs:
- correction for pipe friction
- correction for deviation
12
- Reference, date, place
PLT Tools – Density tools in TEPI
SONDEX - FDR
SCHLUMBERGER - Gradiomanometer
Object of measurement :
Radioactive Emission
SPECIFICATION
RANGE
SPECIFICATION
RANGE
Temperature (max)
350 F
Temperature (max)
350 F
Pressure (max)
15000 psi
Pressure (max)
15000 psi
Diameter
1 11/16 in
Deviation (max)
70 degree
Length
585 mm
Diameter
1 11/16 in
Range
0-1.25 g/cc
Length
51.9 in
Accuracy
+/- 0.03 g/cc
Range
0-1.5 g/cc
Resolution
0.01 g/cc
Accuracy
+/- 0.03 g/cc
Not affected by well bore deviation
Advantages
Center tool – problem with flow regime
Fluid circulation – design problem
- Reference, date, place
More stable than pressure gauge derivative
Big error in fluid density estimation
Give instantaneous fluid density
Use nuclear source (Am-241)
13
Advantages
Not affected by friction
Close 100% success ratio
Drawbacks
Object of measurement :
Pressure Differences
Center tool –flow regime problem
Drawbacks
Affected by wellbore deviation
Affected by wellbore friction
Sensitive to ‘jetting effect’
Quite ‘frequently’ failure – silicon oil problem
PLT Tools - Density
The density measurement give an instant picture of the fluids in the well
▪ As quicklook, do not interpret systematicaly density increase as a water
source (especially for gradio-manometer tool)
To confirm the validity of data, uses the derivative of pressure as a second
density profile
The slowest pass is best, as there are less effects on the curve.
Look for changes which will indicate entries of different fluids.
The sump may give confusing readings due to completion fluid
14
- Reference, date, place
PLT Tools – Fluid Hold up tools
The purpose of this tool is to determine the mixture hold up and
determine the relative proportions of the phases present
Two main way to measure it
▪ Single sensor in the “middle” of the wellbore
▪ Capacitance/Impedance tools
▪ Imaging tools that allow you to have a complete view of the borehole with several
probes : Multi array tool
▪ Two main manufacturers are
▪ Sondex :
▪ Multi Capacitance (CAT)
▪ Multi Resistivity (RAT)
▪ Schlumberger : 4 probes
▪ Multi Resistivity (flowview)
▪ Optical probes (GHOST)
15
- Reference, date, place
PLT Tools - Capacitance
This tool use the difference between the
dielectric constant of water (78) and that of oil
or gas (4).
A simple way to find the dielectric constant of
a fluid is to use the fluid as the dielectric
between the plates of a capacitor
The capacitance may be found by classical
methods such as including it in an RC network
and finding the resonant frequency
Hence the tool measures frequency… counts
/sec
This tool needs a calibration
▪ Before job (in air and water)
▪ During job (in water and hydrocarbon from shut-in pass)
So not possible with memory PLT and never done with E-line jobs (no witnessing)
16
- Reference, date, place
PLT Tools – Capacitance Limitations
0
This class of tools works
well as long as
hydrocarbon are the
continuous phase
Satisfactory
Yw
Yw = 0.4
0.5
The tool goes into
“conductive” mode when
the water becomes the
dominant phase
1
6000
cps
3000
This tool needs calibration (surface check, and downhole in-situ calibration)
In practice they become unreliable if the water cut is above 30% - 40%
Filming and wetting effect could affect the interpretation
17
- Reference, date, place
PLT Tools – Multi probe tools
The purpose of this tool is to determine the mixture hold up and
determine the relative proportions of the phases present thanks
to several probes
Imaging tools that allow you to have a complete view of the
borehole with several probes : Multi array tool
▪ Two main manufacturers used in TEPI
▪ Sondex :
▪ Multi Capacitance (CAT) : trial done on PCK
▪ Multi Resistivity (RAT)
▪ Schlumberger : 4 probes
▪ Multi Resistivity (flowview)
▪ Optical probes (GHOST)
18
- Reference, date, place
PLT Tools – Flowview (DEFT) - Probe principle
Used to differentiate water and
hydrocarbon
4 probes located on the caliper arms
▪
▪
Relative bearing recorded
Several position are possible
Based on resistivity measurement
▪
▪
Need a saline water
Distinct fluids (no emulsions)
Flow not affected by presence of the tool
(down pass)
▪
It is not unusual to discard up passes
Only differentiates between water and
hydrocarbons
▪
▪
▪
19
Cannot differentiate between condensate
and gas
Better gas bubble estimation in water column
Possibility to obtain wellbore image
- Reference, date, place
PLT Tools – DEFT Limitations
DEFT sensibility depends on main phase
▪ Water continuous phase
▪ Current is emitted from the probe tip and returns to the tool
body
▪ A small droplet of HC will break the circuit and will be
recorded
▪ Gas continuous phase
▪ A droplet of water touching the probe tip will not provide an
electrical circuit.
▪ Instead, the water droplet must connect the electrical probe
to the earth wire. Thus a larger droplet is needed for gas or
oil detection than in a water-continuous phase
The fluid response is affected by the fluid
velocity especially in gas column
▪ ➔ DEFT is not recommanded for high flowrate
The signal from the FloView probe lies between two baselines,
the continuous water-phase response and the continuous
hydrocarbon-phase response.
To capture small transient bubble readings a dynamic threshold
is adjusted close to the continuous phase and then compared
with the probe waveform.
The number of times the waveform crosses the threshold is
counted and divided by 2 to deliver a probe bubblecount
20
- Reference, date, place
PLT Tools – Hold up tools in TEPI
SCHLUMBERGER – DEFT/FLOW VIEW
SONDEX - CWH
Object of measurement :
Fluid dielectric constant
Advantages
Drawbacks
21
Object of measurement :
Fluid Resistivity
SPECIFICATION
RANGE
SPECIFICATION
RANGE
Temperature (max)
177 C
Temperature (max)
-25 – 150 C
Pressure (max)
15000 psi
Pressure (max)
15000 psi
Diameter
1 11/16 in
Length
1.75 m
Length
666 mm
Weight
11 kg
Accuracy
1.0%
Accuracy
Resolution
0.1%
5%
bubble >2 mm
Dev < 30 deg
▪Good for vertical well
▪Dedicated to “3 phase” identification
▪
▪
▪
▪
▪
Center tool – problem with flow regime
Limited in BSW (40%)
Measured in single point
Need down hole in-situ calibration
Wetting Effect
- Reference, date, place
Advantages
▪ Multi point sensors (4 probes)
▪ Dedicated to water detection (in gas
and oil well)
Drawbacks
▪ Limitation in fluid velocity
▪ Limitation in water salinity (2000 ppm)
Sondex – Capacitance Array Tool (CAT)
Same technology as capacitance
12 capacitances positioned on centralizing arms
▪
All sensors are located on the periphery
Same limitation as capacitance
Trials done in TEPI concluded in overestimation of
water
SONDEX - CAT
12 Probes
22
- Reference, date, place
PLT Tools – GHOST - Probe principle
Used to differentiate gas and liquid
4 optical probes positioned on centralizing arms
▪
▪
Relative bearing recorded
0.1 mm diameter sensing area
No wetting effects
No maximum phase velocity limitation
Reflection of light to photodiode is
high in gas and low in liquid.
23
- Reference, date, place
Water Flow Log
Based on Oxygen activation of the water with a neutron emitter
▪
Gamma rays are transported by water and are detected by Near and Far detectors)
Detect water movement
▪
▪
Either inside or outside tubing
Whatever the salinity
Two runs to detect
▪
▪
▪
Emitter up : detect water circulation downward
Emitter down : detect water production
Used during stationary
Allow to evaluate a water velocity
▪
Rates are difficult to estimate due to unknown diameter of the channeling
Succesfully recorded in TEPI (SNB-201, TN-AA21)
24
- Reference, date, place
Backup
25
- Reference, date, place
Three-Phase Holdup Measurements
GHOST measures
gas holdup
FloView measures
water holdup
26
- Reference, date, place
Combining FloView
& GHOST provides
oil holdup
PLT Tools - Flowmeter
RELATIVE
BEARING
FLOVIEW or
GHOST PROBES
X-Y CALIPER
CENTRALIZER
ELECTRONICS
SPINNER
ROLLER or SKID
27
- Reference, date, place
PFCS Schlumberger
More Spinners
28
- Reference, date, place
More Spinners
29
- Reference, date, place
Temperature: Flowing Well
Temperature
flowing
In this standard well the
gradient is shown in
green.
4
3
2
1
30
Geothermal Gradient
perforated zone
- Reference, date, place
Fluid enters the well
through the perforations
and continues up the
well.
The hotter fluid increases
the temperature away
from the geothermal
gradient.
Temperature: Gas Flow
Gas expands as it enters
the wellbore.
The expansion is
adiabatic
This creates a cooling and
hence a lower
temperature.
31
- Reference, date, place
Temperature: Channeling
Spinner
geothermal
Water flow
behind casing
32
- Reference, date, place
Temperature
Schlumberger FSI Tool
FloScan Imager Tool
5 Micro-spinners
6 GHOST gas holdup sensors
6 FLOVIEW (DEFT) water holdup sensors
33
- Reference, date, place
FSI - Tool Configuration
Tool bottom
34
- Reference, date, place
Flow Profile Behavior
Vertical – low deviation wells
Smooth velocity and holdup profile across the pipe
Conventional centered measurements generally provide the solution.
Low – high deviation wells
Some areas of the wellbore can be monophasic, but segregation
effects can create very complex flow regimes and varied profiles across
the wellbore. Shear forces between fluids gives instabilities and large
velocity and holdup gradients across the wellbore.
High deviation – horizontal wells
Flow regimes are generally stratified even at higher velocities.
However small changes in deviation will dramatically change the velocity
and holdup profiles.
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- Reference, date, place
FSI – Image views
Linear: simple linear interpolation,
Spline: cubic spline though all the points with no
curvature at the end points.
Smooth spline: cubic spline though the end points
and one point along each intermediate segment.
36
- Reference, date, place
Three Phase Holdup
N/F Ratio
Inelastic Spectrum
Casing
YG
Inelastic N/F Ratio
Gas Hold-Up Response
YG = 0.00
YG = 0.33
YG = 0.67
YG = 1.00
YG
Carbon
Oxygen
YO
YW
Energy (MeV)
Near & Far C/O
C/O Model Response
Far C/O Ratio
Counts
Porosity
Near C/O Ratio
37
- Reference, date, place