USER GUIDE-Production Logging Toolstring

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PLT








STANDARD LENGTH
AND
SHORT COMPACT
PRODUCTION LOGGING TOOLSTRINGS

User Guide

































This User Guide is intended as a general reference source for the UltraWireTM Production Logging toolstrings and principles of production
logging relating to them. The information and data provided has been checked for accuracy where possible. However Sondex and its employees
do not accept responsibility for any decisions made by the reader or results obtained from the use of this document and its associated materials.

For more information please refer to our manuals or contact [email protected]

Version 1.0, September 2006
Copyright © Sondex Wireline Ltd 2006. All Rights Reserved.



Production Logging Toolstring

PLT
_____________________________________________________________________________
Sondex manufactures both standard length and short compact production logging strings. This user guide
addresses the principles of measurement, logging operations and use of the data for both strings.

Functional Description

Production Logging Tools (PLT) are used to gather fluid data which is used by oil companies to maximize
hydrocarbon recovery or manage fluid profiles for injection wells.

Log data is used to

Identify producing zones and the fluids from them – oil, water, gas or mixtures.

Detect leaks, low pressure zones or problem zones that require remedial work to repair the
damage or block off zones

Calculate qualitatively the flowrates of oil, gas and water from each producing zone

Profile injection fluids - these are typically water or gas.

Production logging (PL) is an essential part of reservoir management. During the life of a field problems will occur
that reduce oil or gas production, in many cases the wells are old and the reservoir is mature. PL information helps
towards correcting these problems.

A typical breakdown of 100 logging operation analysed by the prime reasons for the job is illustrated below. Often
there are secondary reasons.

Mec
e h
c a
h n
a ic
i a
c l
a
l P
ro
r bl
b e
l m
e s
Pr
P od
o uc
u t
c io
i n
o P
r
P of
o ile
l s
e
7%
7
24
2 %
4
In
I j
n ec
e t
c io
i n
n P
r
P ofil
i es
e
Wat
a er
e P
r
P ob
o le
l m
e s
10
1 %
0
45
4 %
5
Ex
E c
x e
c s
e s
s
s ga
g s
a
s P
r
P ob
o le
l m
e s
14
1 %
4




Production Profiling
To profile the well to check how it is performing against expectations. Includes the
determination of layer pressure in multi zone wells.
Injection Profiling
To determine the injection profile of a water or gas injection well.
Water Problems
The majority of PL jobs are performed because large volumes of unwanted water are
produced. Water production is very expensive because it limits hydrocarbon production
and has to be treated and disposed of safely. Locating the source of the water production
is vital towards planning remedial work in wells that produce water.
Excessive Gas Problems
This limits the flow of oil. In some cases this gas has to be flared which is a waste of
energy and detrimental to the environment. Locating the source of the gas production is
important when planning remedial work in these wells.
Mechanical Problems
Gross mechanical problems such as holes in tubing can be located using production
logging tools. Leaks through damaged casing or tubing strings must be repaired. Blocked
perforations can also be identified.

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Production Logging Toolstring

PLT
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Example of water production due to fingering

In this example of a reservoir with strong water drive, the most permeable layers are depleting faster than the less
permeable layers. As oil moves from the high permeability zone water replaces it and eventually flows into the
wellbore resulting in reduced oil production. Water viscosity is lower than oil, as such it is produced preferentially
which lowers the overall flowrate by loading up the well and causes disposal problems at surface. Production
logging tools are used to identify from which perforated zones the water is coming from.

Subsequent remedial work to shut-off the water zone will increase the oil production from zones which remain open
by allowing the bottom hole pressure to be lowered i.e. increase the drawdown.


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Production Logging Toolstring

PLT
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Short Compact Production Logging Toolstring components.

The main elements of the Short Compact Toolstring (SCT) are the Quartz Pressure/CCL (QPC) tool and the
Capacitance/Temperature/Flowmeter (CTF) tool. By combining multiple sensors the overall tool length is reduced
compared to a standard length PLT string using similar sensors. Uing a shorter toolstring is particularly important in
operations where rat-hole and rig-up height are critical such as tractor or coiled tubing logging and on very small
platforms. The SCT is available in two sizes, 111/16in (43mm) OD and 13/8in (35mm) OD. The combination of
sensors provide complementary information for wellbore fluid analysis.

Combined
The Quartz Gauge measures changes in downhole flowing and
Pressure and
shut-in pressures. This information indicates the efficiency of the
CCL tool
well and performance of the reservoir. In the absence of a
(QPC)
dedicated density tool it can also be used to estimate density.

The CCL sensor responds to changes in metal volume such as
at casing joints, completion items or perforations. It is mainly
used for depth correlation though can be used to detect holes
and perforations.
Gamma Ray Measures natural gamma ray radiation levels in the wellbore.
tool
Used for depth correlation, lithology and radioactive scale
identification which is associated with water production.
Inline Spinner The ILS flowmeter is used as a back up flowmeter in conjunction
(ILS)
with a CFS or CFB and when it is necessary to log in tubing and
casing in one logging run. (combined with a fullbore flowmeter)
Density
Oil, water and gas have different densities. By measuring the
overall density of the wellbore fluid the fraction or holdup of each
phase can be calculated.
Combined
Oil, water and gas have different dielectric responses The
Capacitance,
Capacitance sensor responds to the dielectric properties of the
Temperature
fluids in the wellbore. The tool has different frequencies in gas,
and
oil and water but it is principally used to measure the water
Flowmeter
fraction in the mixture.
(CTF)
The Temperature sensor responds to small temperature
changes - indicating fluid movement inside and/or outside of the
completion. Temperature changes can be used to qualitatively
identify fluid type, volume and direction of flow.
The Flowmeter measures well fluid velocity using a turbine
(spinner) impeller, the higher the fluid velocity, the faster the
spinner rotates. Knowing the fluid velocity and tubing size,
volumetric flowrate can be calculated. Spinner mechanical
sections should be selected to suit completion size and fluid
velocity. However in general, the largest spinner impeller that
can be used will give the best results.

Caged Fullbore Flowmeter: The spinner impeller is
closed in tubing and opens up in casing to present a
large diameter impeller, giving high sensitivity. It is
protected by a springbow cage.

Continuous Spinner Flowmeter: This spinner rotates
continuously. It is typically used in tubing and in casing
for high rate gas wells. It has roller bearings.


Jewelled Spinner: This spinner rotates continuously. It
has jeweled bearings which give superior performance
at very high fluid velocity and in wells with sand or
solids polluting the well fluids (which can jam up roller
bearings).

The 1 3/8in (35mm) diameter SCT is recommended for small diameter tubing. There is a wide range of additional
tools which can be run with the ultrawire SCT to enhance the results.
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Production Logging Toolstring

PLT
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Standard Length Production Logging string components

Unlike the SCT, the standard length PL string consists of single sensor tools and is available with 111/16in (43mm)
OD. Although the standard string is longer - 20.5ft (6.2m) compared to 16.2ft (4.9m) for the SCT - it offers greater
flexibility of use.

Quartz
Measures changes in flowing and shut-in pressures, this
Pressure
information indicates the efficiency of the well and performance
gauge, QPS
of the reservoir. In the absence of a dedicated density tool it can
also be used to estimate density.
CCL
The CCL sensor responds to changes in metal volume such as
at casing joints, completion items or perforations. It is mainly
used for depth correlation though can be used to detect holes
and perforations.
Gamma Ray
Measures natural gamma ray radiation levels in the wellbore.
Used, for depth correlation, lithology and radioactive scale
identification which is associated with water production..
Inline Spinner The ILS flowmeter is used as a back up flowmeter in conjunction
(ILS)
with a CFS or CFB and when it is necessary to log in tubing and
casing in one logging run. (combined with a fullbore flowmeter)
Density
Oil, water and gas have different densities. By measuring the
overall density of the wellbore fluid the fraction or holdup of each
phase can be calculated.
Capacitance
Oil, water and gas have different dielectric responses, the
capacitance tool has different frequencies in gas, oil and water
but it is principally used to measure the water fraction in the
mixture. .
Temperature
The temperature sensor responds to small temperature
changes - indicating fluid movement inside and/or outside of the
completion. Temperature changes can be used to qualitatively
identify fluid type, volume and direction of flow.

Flowmeters
The flowmeter measures well fluid velocity using a turbine
(spinner) impeller, the higher the fluid velocity, the faster the
spinner rotates. Knowing fluid velocity and tubing size,
volumetric flowrate can be calculated. Spinner mechanical
sections should be selected to suit completion size and fluid
velocity. However in general, the largest spinner impeller that
can be used will give the best results.

Caged Fullbore Flowmeter: The spinner impeller is
closed in tubing and opens up in casing to present a
large diameter impeller, giving high sensitivity. It is
protected by a springbow cage.

Continuous Spinner Flowmeter: This spinner rotates
continuously. It is typically used in tubing and in casing
for high rate gas wells. It has roller bearings.

Jewelled Spinner: This spinner rotates continuously. It
has jeweled bearings which give superior performance
at very high fluid velocity and in wells with sand or
solids polluting the well fluids (which can jam up roller
bearings).






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Page 5 of 24


Production Logging Toolstring

PLT
_____________________________________________________________________________


When running either the SCT or a standard PL toolstring some general points should be observed


Deployment items such as centralisers, knuckle joints and swivel joints, are required as necessary.

The spinner impellers and fluid ID tools should be run centralised.

The flowmeter mechanical section should be selected to match the completion ID and make sure it will go
through the minimum restriction in the well.

The tools can be run in surface readout mode by adding a telemetry cartridge or, in memory mode by adding a
memory recorder.

Key Points

Short Compact Toolstring:


Uses combined sensor tools (QPC and CTF) to reduce overall toolstring length

Available as 1 3/8" (35mm) and 1 11/16" (43mm) OD tools

Are portable and have reduced rig up height

The distance between sensors is reduced thus first readings are closer to the bottom of the logging interval

Has fewer tool connections than a standard length PL toolstring

Individual sensors on the QPC and CTF cannot be re-positioned or removed

Standard Length Toolstring:


Uses separate tools

111/16in (43mm) tool diameter

Separate tools offer more flexibility to configure toolstring but adds to the overall length.

Overall length is approximately 4.5 ft (1.4 m) longer than the SCT.

Has more tool connections than the SCT.

Individual sensors can be re-positioned or removed.


Sensor Specifications

Sensor
Range
Accuracy
Resolution
Remarks
Quartz Crystal Pressure
16,000 psi
+/ - 3.2 psi
0.01 psi
Very
accurate
pressure
measurements. Often perform
better than specification.
CCL
Not
Not applicable
Not

applicable
applicable
Gamma Ray
40,000 API
+ / - 5%
1 API

Temperature
180 deg C
0.5 deg C
0.003 deg C Response time better than 1 sec.
Density (Radioactive)
0-2 g/cc
0.02 g/cc
0.01 g/cc
Uses Am241 150 mCi RA source
Density
0-2 g/cc
0.03 g/cc
0.02 g/cc
Non radioactive. Pressure acts
(Differential Pressure)
on two ports separated by a
silicon fluid column inside the tool
Capacitance
Water 0-100%
Depends
on 1%
Optimum operating range 0-40%
Holdup
water
holdup
water holdup. Will work up to 100
% holdup but with reduced
accuracy.
Flowmeter:
0-60 RPS
+/- 2 ft/min
0.1 RPS
Servicing is critical for optimum
Caged Full-bore
performance.
Flowmeter:
0-100 RPS
+/- 7-10 ft/min
0.1 RPS
Servicing is critical for optimum
Continuous Spinner
performance.
Flowmeter:
0-115 RPS
+/- 7 ft/min
0.1 RPS

Jewelled Spinner
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Production Logging Toolstring

PLT
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Toolstring Dimensions (Typical toolstring):

Short Compact Toolstring:

Operating mode

Memory
Surface read-out
Communication
Battery Housing/Memory Recorder
Cable Head/Telemetry crossover
Combined sensors
Quartz Pressure / CCL
Quartz Pressure / CCL
Ancillary
Knuckle Joint
Knuckle Joint
Depth correlation
Gamma Ray
Gamma Ray
Ancillary
Knuckle Joint
Knuckle Joint
Ancillary
Centraliser
Centraliser
Density
Radioactive Density
Radioactive Density
Ancillary
Centraliser
Centraliser
Combined sensors
Capacitance / Temperature / Flowmeter
Capacitance/Temperature/Flowmeter
Length
17.0ft
5.2m
16.2ft
4.9m
Weight
81lbs
37kg
77lbs
35kg


Standard Length Toolstring

Operating mode

Memory
Surface read-out
Communication
Battery Housing/Memory Recorder
Cable Head/Telemetry crossover
Sensor 1
Pressure
Pressure
Sensor 2
CCL
CCL
Ancillary
Knuckle Joint
Knuckle Joint
Sensor 3
Temperature
Temperature
Ancillary
Knuckle Joint
Knuckle Joint
Ancillary
Centraliser
Centraliser
Sensor 4
Gamma Ray
Gamma Ray
Sensor 5
Radioactive Density
Radioactive Density
Sensor 6
Capacitance
Capacitance
Ancillary
Centraliser
Centraliser
Sensor 7
Caged Full-bore Flowmeter
Caged Full-bore Flowmeter
Length
21.3ft
6.5m
20.5ft
6.2m
Weight
107lbs
49kg
103lbs
47kg

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Production Logging Toolstring

PLT
_____________________________________________________________________________

Example Production Logs

Example 1: Oil and water and production.

In this example, water production in an oil-producing well has increased reducing oil content per barrel of liquids
produced at surface. Before designing a programme of remedial work the oil company decided to run a production
logging survey to identify which perforated zones were producing high levels of water and should be plugged off.

The log, in Fig 1, is a composite log of spinner curves (all passes) plus other sensors (slowest down pass). The
spinner flowmeter gives the inflow profile and the density and fluid capacitance curves indicate the oil-water mixture
at different depths. These curves show high turbulence as you would expect from a flowing mixture of oil and water.
Scales for sensor curves have been expanded to show small changes, e.g. density is scaled from 1.0 to 1.2 g/cc.
Without high resolution tools it would be hard to detect these small changes. The temperature curve also indicates
the points of inflow and the gamma ray curve shows localized high levels of radioactivity which (in this case) are
associated with water production. The spinner curves show fast fluid entry from the high permeability layer – known
as jetting effect – at 11680. The next stage is to perform a numerical analysis of the data at a log interpretation
centre to determine the oil and water in-flow and water cut of each zone.

The interpretation of this well is shown on page 21 of this guide.

Fig 1. Composite PL log








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Production Logging Toolstring

PLT
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Example 2: High water production together with sand.

To shut off the water production in a well the sliding side door (SSD) at 4940ft was closed by slickline however the
well continued to produced water. A production log was run confirm the status of the SSD. The log shows the SSD
was closed but that there was a hole – caused by external sand erosion - in a blast joint at 5050ft adjacent to the
perforations. The water cut of the flow through the hole was calculated to be 85%.

Although the total fluids produced from this zone had an oil cut of 15% this equated to 50% of the well’s total oil
production, therefore if the zone had been plugged to shut off the water this would have resulted in a significant
reduction in oil produced at surface. The client decided not to carry out a remedial operation to patch the hole at
this stage and to come back later when this zone has watered out fully (to be determined by production logging).



Example Log 2: Hole in blast joint


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Production Logging Toolstring

PLT
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Sensor theory

Each of the sensors has a different principle of measurement.

Pressure: Wellbore fluid pressure acts directly on a quartz crystal
which is oscillating at its natural frequency - changes in oscillation
frequency are proportional to the changes in fluid pressure.
Simultaneously well temperature also affects the frequency of the
crystal, to compensate and correct temperature-associated changes a
second temperature crystal is included within the gauge to measure
the temperature of the pressure crystal but it is not exposed to well
pressure.

The reference crystal is used to reduce the output frequencies. In

Sondex tools this crystal is also used to count the pressure and
temperature frequencies enabling duplication of the original
manufacturer’s calibration accuracy.

An inconel bellows in the sensor arrangement acts to prevent well fluid
contamination of the pressure crystal.
CCL: Two powerful magnets are positioned with opposite poles
adjacent to each other, creating lines of magnetic flux which pass
through the tool, tubing and a coil between the magnets.

When there is a change in metal volume the lines of magnetic flux are
disturbed generating a small voltage in the coil which is converted to a
frequency by a voltage-to-frequency converter.

The CCL housing of the tool is non magnetic to prevent it effecting the

measurement.

Temperature: A tiny platinum resistor sensor is enclosed in an Inconel
probe needle exposed to the wellbore fluid. The resistance of the
sensor is affected by temperature changes causing a voltage
differential across the probe. This differential voltage is converted to a
frequency and output as a temperature measurement. This
measurement is then amplified electronically to give very high
resolution.

The rapid response time of the sensor makes it able to detect tiny
temperature changes. Therefore the tool has excellent resolution and

is very accurate. The effects of changing line speed are minimised
which allows for better temperature log overlays.


Scintillation Gamma Ray: When gamma rays from the formation or
elsewhere strike the Sodium-Iodide crystal of the gamma ray detector
Detector
photons of light are emitted (the crystal scintillates). The levels of light
High Voltage Power Supply
are very small so a photomultiplier tube (PMT) is used to amplify the
signals to the level that they can be detected.
Photo Multiplier Tube

The detector circuit detects and filters the amplified signals which are
then output from the tool as a gamma ray trace on the log.
Sodium Iodide Crystal

The PMT requires a high voltage power supply to amplify the photons

of light. The tool uses a large crystal.


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