book

1. Cased Hole Logging
• Surveillance and by-passed pay

2. Cased Hole – Fluid Composition
Capacitance, Fluid Di-elect. Fluid type - hydrocarbon vs. water.
Fluid Resistivity Fluid type - hydrocarbon vs. salt water.
Pulsed Neutron Capture 3-phase ID in well, req. homogeneous formation
Gradiomanometers Fluid type - oil and water, looses resolution in high deviation,
limited in high rate and high oil cut.
Fluid Density Fluid type- oil vs. water, better in high GLR.
Temperature Fluid entry (zones/leaks) rate/temp limits.
Noise Leak/zone entry. Channel flow behind pipe, depending on
rate.
Fluid Level Survey Fluid level only, confused by foams, froths and emulsions.
Spinners Total flow rates and entry/exit points. Deviated wells are a
challenge.
Radioactive Tracer Tool Total flow rates and entry/exit points. Not useful in deviated
wells.
Oxygen Activation Velocity of water phase. Holdup and leak detection.

3. Cased Hole – Casing/Cement Inspection
Caliper Log Accuracy depends on number of
fingers, speed, tool type.
Casing Inspection
Eddy Current Inner wall investigation. Shows some
smaller flaws, measures ID
Casing Inspection
Flux Leakage Casing body inspection. Id of inner /
outer wall, and body casing
problems, not in OBM
Casing Inspection
Ultrasonic Casing body inspection. Affected by
fluids, used in thicker wall pipe
(>0.2”)
Casing Inspection
Electromagnetic Phase Shift Casing body inspection. ID and wall
thickness, averaging tool may
miss small defects
Casing Inspection
Conventional Acoustic Cement presence. Averaged data, not
really useful for most problem
identification
Cement Evaluation
Segmented Acoustic Channels, Bond. 360o, channels and
voids, bond under right
conditions.
Cement Evaluation
Ultrasonic Casing and Cement bond. 360o,
channels, voids, bond, pipe
conditions w/ right application.
Cement Evaluation

4. Cased Hole – Correlation/Evaluation
Gamma Ray Lithology and correlation
Inexpensive. No porosity.
Correlation
Neutron log – single detector Lithology and correlation
Inexpensive. No porosity.
Correlation
Neutron log – dual detector Porosity. RA source needed,
accuracy less than OH log.
Formation
Evaluation
Acoustic Porosity. Limited in cased wells,
requires good bonds for accuracy
Formation
Evaluation
Pulsed Neutron Capture
PNC
Water saturation. Does not work in
low or changing salinity, or low
porosity
Formation
Evaluation
Pulsed Neutron
Spectrometry PNS C/O
Water saturation. Does not work
well in low porosity
Formation
Evaluation
Cased Hole Resistivity Water Saturation. Salinity
dependent, stationary reading,
relative deep reading
Formation
Evaluation

5. Problem or
Information Needed
Rec. Logging Tools
Procedure/Level of Detail
Detection of
Crossflow or
Underground
Blow out
Temperature
Survey
Difference in slope of temperature gradient – will
detect flow rates down to 25 BPD if liquid and
temperatures of fluids are different. Figures on
temperature vs. flow distance help estimate water
flow in the annulus.
Noise Log Best performance of noise logs is with gas flow.
Gas flow to about 10 actual ft3/D (Note – not
standard ft3/day). At very low gas flow rates
(q<400 actual ft3/D), gas flow can be estimated
from millivolts of noise between the 200-Hz and
600-Hz frequencies:
q = 0.35 (N200 – N600). Where q is the actual gas
flow in ft3 and N = noise log cut at that frequency.
Oxygen
Activation Survey
Open hole or channels behind single string.
Accuracy is sharply reduced for investigating
channels behind two strings (use temp or noise
tools).
Detection of Crossflow

6. Problem or
Information Needed
Rec. Logging
Tools
Procedure / Level of Detail
Location of Cement
Top
Temperature
Survey
OK if run within 12 to 24 hrs of cement job.
Little temperature variation with the formation
may make cement top difficult to see.
CBL (cement
bond log)
Best results after 3 days or when cement has
developed 70%+ of the compressive strength.
These tools may be too large for slim hole wells.
Gravel-pack
logging (GR)
Tool response depends on density difference
between cement and annular fluid.
Location of Cement Top

7. Problem or
Information Needed
Rec. Logging
Tools
Procedure / Level of Detail
Evaluation of Cement
Placement
Open hole
caliper
Accuracy depends on caliper and hole roughness
and washouts. Caliper tools with more than 4
arms are needed for hole volume measurement
accuracy.
Sweeps with
markers after
running casing
Sweeps give decent estimates of hole volume, but
sweeps may not reach all of the annular space in
uncentralized cased holes. Useful for swept hole
% analysis.
Temperature
Survey
OK if run within 12 to 24 hrs of cement job.
Little temperature variation with the formation
may make cement top difficult to see.
Gravel Pack Log Good if fluid density difference greater than 0.3
gm/cc (0.13 lb/bbl). Could run before and after
cement for background data.
CBL – both
regular and
segmented
Semi-quantitative contact measurement of
pipe/cement and cement/formation. Affected by
casing pressure and tool calibration.
Evaluation of Cement Placement and Bond

8. Problem or
Information
Needed
Rec. Logging
Tools
Procedure / Level of Detail
Detection of
casing wear
from drilling
E-line calipers Multi-arm calipers generally good, but slick line
calipers may rotate and “over-report” the bad
spots.
EM – eddy
current tool that
measures wall
thickness
Highly accurate if the hole is filled with a non
conductive fluid.
Acoustic wall
thickness tool
Qualitative indicators of wear (thickness
numbers are not very accurate)
Casing Inspection

9. Problem or
Information
Needed
Rec. Logging
Tools
Level of Detail
Detect casing
collapse
EM – eddy
current wall
thickness survey
Investigation is to 8 to 10” radius. Investigation
ability falls off after the first string encountered.
Qualitative investigation. Splits are more
difficult to see.
Gravel-pack (GR
– density)
Depth of investigation depends on source
strength – may range from 4” to 16”. Splits are
more difficult to see.
Determination of External Casing Corrosion

10. Problem or
Information
Needed
Rec. Logging
Tools
Procedure / Level of Detail
Annular Flow Temperature
Survey
Useful where the well has active annular flow.
Can spot flows on the order of 1 bpd (after 24
hrs) if temperature of formation at
measurement and source of water is sufficiently
different. Two surveys, 12 hrs apart is usually
adequate to spot presence of a channel.
OA - oxygen
activation
Accurate, but don’t swap out muds. Migration
of fluids in pipe may be seen as “channel”.
Noise logging Accuracy depends on channel variations to
accelerate flow and change sound.
Flow Behind Pipe

11. Problem or
Information
Needed
Rec. Logging Tools Procedure / Level of Detail
Determine
annular flow
in injector
RA Tracer Survey
- inject slug of I-
131 in brine.
Track from surface to annulus until slug is
completely pumped away. Track any flow that
goes behind pipe and moves up.
OA- oxygen
activation survey
Not as reliable as the chemical tracer, due to
fluctuations in the injection rate.
Temperature
survey
Three temperature surveys are needed: one before
annular injection (base line), one during and one 4 to 6
hours after injection (decay).
Borax Log Pumping borax/water solution down tbg into the liner,
allowing mix to invade perfs & any channels in
casing/formation annuli. Initial pass, before borate
injection, is w/ Pulsed Neutron log (no Borax),
followed by passes at 20bbls, 40bbls, and 60bbls as
borax mix pumped. Borax affects neutron capture,
leaving a characteristic signature. Overlays of the
Sigma/CNL counts reveal the zones of borax
penetration, and identifies channels taking fluid.
Determination of Flow Behind Pipe for Injector

12. Problem or
Information Needed
Rec. Logging Tools
Procedure / Level of Detail
Certification
for annular
disposal
Radioactive Tracer
Survey with RA
isotope in brine,
pumped into annulus
while logging with a
GR tool in tubing.
Can distinguish entry points and limited detail
on up or down movement of the inject slug.
Oxygen activation
survey
Not as accurate as RA logging. Fluctuations in
rate create problems.
Temperature
survey
Can determine channels and entry points.
Needs 3 runs – before, during and after.
Borax Log Pumping borax/water solution down tbg into the liner,
allowing mix to invade perfs & any channels in
casing/formation annuli. Initial pass, before borate
injection, is w/ Pulsed Neutron log (no Borax), followed by
passes at 20bbls, 40bbls, and 60bbls as borax mix pumped.
Borax affects neutron capture, leaving a characteristic
signature. Overlays of the Sigma/CNL counts reveal the
zones of borax penetration, and identifies channels taking
fluid.
Location of Annular Leak

13. Problem or
Information
Needed
Rec. Logging
Tools
Procedure / Level of Detail
Location of leak
to annulus or
crossflow behind
pipe
Temperature
survey
Relatively accurate at rates of at 1 bpd or more. Need
minimum of 2 runs, before and during injection. A
third run may help define a qualitative level of leak
rate. Run at 1oF/in sensitivity. Will not see small gas
leak rates through liquid.
Noise log Best for gas leak detection. Run static log and then
again during flow or negative test. Upward gas
movement (percolation) at actual 10 ft3/D or more
should be detectable.
Oxygen
activation log
Can detect flows of 20 to 40 bpd in the annulus of a
single string well if the leak is directly opposite the
tool. Resolution drops to >200 bpd when two strings
are present
Borax Log Pumping borax/water solution down tbg into the liner,
allowing mix to invade perfs & any channels in
casing/formation annuli. Initial pass, before borate
injection, is w/ Pulsed Neutron log (no Borax),
followed by passes at 20bbls, 40bbls, and 60bbls as
borax mix pumped. Borax affects neutron capture,
leaving a characteristic signature. Overlays of the
Sigma/CNL counts reveal the zones of borax
penetration, and identifies channels taking fluid.
Location of Source of Annular Leak

14. Gamma Ray Tool (Basically a
Geiger Counter)
• Uses a scintillation crystal and a photomultiplier tube to
measure naturally occurring and artificially induced
gamma-ray radiation.
• The gamma-ray radiation is a signature of the formations
in a well – very useful in depth control. Used in open hole
or pipe
• Also used to spot changes in radiation (NORM scale) and
radioactive tracers.
• GR is sensitive to logging speed and factors/statistics that
govern radioactive decay.
• Used as one measurement of shaliness, correlation tool for
stacked beds and in shales, seal/barrier location, id of
organic rich zones, gross and net reservoir thicknesses.

15. Multi-sensor caliper (cased hole)
• Multi-arm feeler – gauges the shape and
smoothness of the casing id.
– Corrosion and pit detection
– Pipe collapse and deformation
– Pipe wear

16. Production Logging (PLT)
• Spinner or radioactive tracer ejector that is
useful for identifying and quantifying fluid
entry and exit points in the well.
• Challenged by deviated wells if the tool is
not in the predominant flow stream.

17. PLT in Gas Lift Wells
• Very common to run PLTs in gas lift wells – w/ precautions.
• W/ fullbore spinners, choke the well back and reduce or shut-in the lift gas
to reduce the chance of getting the tool stuck. Make sure the well is stable
before logging.
• Run in at 50 to 75 ft/min. A pressure / density log may show some gas lift
problems that a flowing gradient survey will not.
• There is very little chance of getting the PLT stuck in a GLM if a series of
gauging runs is made immediately prior to the log (insures full ID).
• The fullbore centralizer collapses to the tubing ID and the tool is run with
the spinner centralized so the point / bull-nose on the tool does not contact
the walls of the tubing. There is a possibility of the centralizer holding up
in the mandrel, but picking up and running a little faster should take care
of this.
• Adhere to the service companies recommendation on minimum tool
clearance.
Sources: Duane Toth and Franklin Bohla

18. PLT Sticking Hazard
• Greatest risk of tool hang-up is in the tubing tail (TT).
• Also watch the reservoir (may not be able to run a full ID drift gauge) for
scale build up. Running a slim hole GR prior to the spinner to look for
potential barium scale deposits is a good idea. Other scales and non-
NORM BaSO4 scale may require a tool-sized drift.
• Lost Tool Experiences (from Duane Toth):
– Lost one in Alaska where we didn't shut-in the well before going from the 7"
production casing into 2-7/8" tubing. The tool was off center, hung-up on
the TT, and the wire came loose. We were able to fish this tool.
– The other was in Algeria where we lost the tool across the reservoir section.
Believed to be result of excessive barium scale deposition, but fill may have
also been a problem. This tool string was never recovered, and since it had
the GHOST tool, it was an expensive mistake.
Source – Duane Toth

19. Cement Bond Tool
• Transmitter-receiver tool measures the
signal received back from a segment. Helps
assess cement presence and bond to the
formation and the pipe.

20. Temperature Tool
• A recording of the wellbore temperature.
– Identify fluid entry or exit
– Gas channeling
– Tubular leaks
– Hydraulic frac height
– Cement top
– Fluid levels
– Differential temperature curve

21. Down Hole Static Temperature Varies with
Depth - Effect of the Geothermal Gradient
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
50 100 150 200 250 300
Temperature, F
Depth,ft
"cellar effect - temperature normally cools from surface
temperature to about 100 ft below surface, then temperature
begins to increase with increasing depth. Watch for
anomolies.
This response is about 2.1o
F per 100
ft

22. Temperature log – Saaman Well –
Trinidad. Leak at packer using
annular injection after base line at
same rate.

26. Gradiomanometer
• Measures the differential pressure of a 24”
column of fluid – calculates the fluid
density.
– Determine gas or liquid entry points
– Identify static fluid interfaces
– Determine exact depth of fluid density change
– Assist production logs

27. Flow meter
• Measures fluids moving past the tool.
Moving fluids turn the spinner
– To determine fluid entry or exit points
– Evaluate perforations
– Evaluate cross-flow occurrence
– Helps evaluate completion design

28. Tension Measurement Device
• A component of the tool string that records the
tension during logging in various parts of the
wellbore. Helps spot increased drag and break
free points (tool jumps) that may signal poor
logging tool records.
• Used for quality control on logs, as an indicator of
depleted zones (fluid loss sticking), dog-legs,
location of sticking (above or below tool when
compared with a surface record).

29. Logging Behind Casing
• Key Elements:
– Understand the condition of the casing
– Understand the connection of casing to the
formation – cement bond.
– Inclination, diameter, geometry

30. Information Sought Logging Tools Used
Casing Condition USIT, Multi-arm Calipers, Sonic Calipers, Downhole TV
Cement Condition Cement Bond Logs (sonic)
Saturation Resistivity Tools (CH), C/O Logs, Reservior Saturation Tools, DSS
Lithology Gamma Ray, Density, Neutron, Sonic
Porosity Resistivity Tools (CH), Porosity (CH), CNL, Dipole Shear Sonic
Formation Strength Dipole Shear Sonic,
Oil Resistivity, Casing Wall Coring Tools,
Gas Neutron and Sonic Tools
By-passed Pay Resistivity, O/C Logs,
Pressure Casing Wall Coring Tools
Partial List of Information Sought and
Cased Hole Logging Tools