WELL LOGGING TECHNIQUES AND FORMATION
EVALUATION
Work Shop on
Technology Imperatives For Exploration &
Production of oil& Gas
By
ONGC Academy
26-29th March 2012
Rajahmundry
Presentation By
CENTRE FOR EXCELLENCE IN WELL LOGGING TECHNOLOGY (CEWELL)
ONGC, BARODA
Life of a Well
Seismic
Drilling
Logging
Data Mgmt
Production
Testing
Cementing
Perforating
INTRODUCTION
• THE LOGGING SERVICES – REQUIRED FROM THE DAY OF
SPUDDING (Exploration) TO THE LAST DROP OF PRODUCTION.
• ANSWERS HOST OF QUERIES;
 DEPTH OF POTENTIAL RESERVOIR
 RESERVOIR / PETROPHYSICAL PARAMETERS viz.
POROSITY, PERMEABILITY etc.
 FLUID CONTACT (OIL/ GAS/ WATER)
 HYDROCARBON SATURATION, ESTIMATION OF INPLACE &
RECOVERABLE RESERVES
 DESCRIPTION OF RESERVOIR ROCKS
 GEOCHEMICAL STUDIES AND HELP IN BASIN EVALUATION
INTRODUCTION
Contd….
 PROVIDES FLOW RATES, FLUID TYPE
 RESERVOIR PRESSURE, TEMPERATURE
 CASED HOLE OIL & GAS SATURATION
 POINT OF FLUID ENTRY IN PRODUCING WELLS
 FACILITATES IN SMOOTH AND TROUBLE FREE DRILLING
& COMPLETION OF WELLS
 DETECTION OF ABNORMAL PRESURES, QUALITY OF
CEMENTATION ETC.
APPLICATIONS OF LOGGING SERVICES
WITH THE SUCCESS OF SYNERGISTIC APPROACH, LOGGING
SERVICES GO HAND-IN-HAND WITH EXPLORATION, DRILLING &
PRODUCTION
(1) APPLICATIONS IN EXPLORATION
 KEY TO INTERPRETATION OF
ATTRIBUTE ANALYSIS & AVO
PETROPHYSICS
SEISMIC INVERSIONS,
STUDIES LIES WITH
 NEARBY WELL LOG DATA COMES HANDY IN ALL THESE
STUDIES
 LOGS
ARE
EXTENSIVELY
USED
IN
SEISMOGRAM AND TIME-DEPTH CONVERSION
SYNTHETIC
(2) APPLICATIONS DURING DRILLING:
 OPEN HOLE LOGGING SERVICES HELP IN FORMATION
EVALUATION
 IDENTIFICATION & DEPTH OF POTENTIAL RESERVOIR

RESERVOIR CHARACTERIZATION, FLUID SATURATION &
RESERVE ESTIMATION
 BACKING OFF DRILLING STRING IN CASE OF STUCK-UP
 PLACING OF CASING SHOE, EVALUATION OF CEMENTING
QUALITY etc
 PERFORATION FOR CEMENT SQUEEZE & PRODUCTION
(3) APPLICATIONS DURING PRODUCTION:
 WELL TEST & PRODUCTION LOGGING FOR RESERVOIR
MONITORING
 RECORDING OF PRODUCTION PROFILES
 IDENTIFICATION OF UNWANTED FLUID ENTRY
 WORK OVER JOBS FOR PRODUCTION ENHANCEMENTS,
EOR SCHEME etc
 CASED HOLE LOGS FOR FORMATION EVALUATION &
IDENTIFICATION OF MISSED ZONES
 RECORDING OF INJECTION PROFILES FOR PRESSURE
MAINTENANCE
Birth of Logging
On September 5, 1927
H Doll & Schlumberger brothers,
Conard & Marcel made semi
continuous
resistivity
measurement in 1600 ft deep
well of France`s Pechelbronn
field
First Electric log
recorded on Sep 5,1927
Modern day LOG
LINEAR SCALE
LOG DISPLAY
LOGARTIHMIC SCALE
Technology Advancement
in 1950’s and 1960’s
 Penetration of electronics industry into Logging
 Entry tools
• Flushed zone measurements
• Porosity measurements
• Acoustic measurements
 Developments aided
• Better depth control in perforations,
• Evaluation of rock properties & cement
• Log correlations.
Technology Advancement
during 1970’s
Era of digital data
• Computerized processing and interpretation
• Introduction of digital image logs
• Computerized logging units with facility to transmit the
recorded log-data to the bases
• Tool designers and analysts used power of the computer to
bring to the surface more quality data
• Signal processing theory to log data fundamentally altered
usage of logs
• Introduction of tool strings, a combination of logging tools.
Technology Advancement
1980’s and beyond
 Measurement While Drilling (MWD) started
 1988 Logging While Drilling (LWD)
 Conveying well logging tools into the borehole as part of the
Bottom Hole Assembly (BHA).
 Open hole measurements near the bit before invasion
becomes too serious.
 Enhanced Reservoir Description because of the
immediate acquisition of data and the reduced invasion
profile.
LWD
Zone 1
Zone 2
Zone 1
Sand A
Zone 2
Zone 3
Sand A
Zone 3
Zone 4 Sand B
Zone 4 Sand B
Zone 1
Zone 2
Sand A
Zone 3
Zone 4
Sand B
Tool Conveyance
Open - Cased Hole Measurements :
 The Traditional Wire-line Logging.
 LWD (Logging While Drilling)
 Logging on Drill Pipe (TLC)
 TRACTOR
6” Drain Hole length: 600 m.
Oil @ 800BOPD W/C 65 %
Density-Porosity
Resistivity
Gamma Ray
SWEET ZONE > 95 %
RIG TIME SAVING ABOUT TWO DAYS
Technology Advancement
1980’s and beyond
 New and improved sensors utilizing multiple array of
electrodes, coils, detectors & sources
 Downhole microprocessors to control measurements and
tele-metering
 Formation Evaluation While Drilling (FEWD)
 Surface acquisition and satellite transmission
 Interactive Workstations for interpretation
Technology Advancement
1980’s and beyond
IMAGE TOOLS
 High resolution measurements provide better insight into
formation
 Enhancement in resolution of thin-beds to resolve them to
about 1/3rd of the thickness of previous tools.
 The measurements require excellent borehole condition.
 These logs provide more megabytes of data than ever
before.
 Computer speed, memory size, and data storage capacity
of modern desktop computers have kept pace with these
developments.
Electrical methods
 Provide enhanced image of the borehole.
 Formation micro-scanner (FMS) or micro-imaging (FMI)
log - a super-micro, multi-electrodes, multi-pads
resistivity log, an offshoot of the dipmeter tool.
 Image enhancement software, similar to that used for air
photos, can be applied to help bring out subtle details.
Dipmeter & FMI
Overview
– Developed as successor to the FMS
(Formation Micro Scanner) in 1991
– Provides Microresistivity formation
images in Water Based Mud
– Combinable with other wire-line tools
• Benefits
– Electrical Core
– Can be used in deviated and
horizontal wells
– Detailed and reliable interpretation of
formation features and dips
– Improved reservoir description
Formation Micro Imager
4 Arms - 8 Pads
192 Electrodes
FMI: Estimation of Pay thickness
( Thinly Laminated Reservoir )
Static
Dips
Dynamic
Cum. Prod: 3800 Tons.
DEN
PHIN
RES
FMI Image with Open hole logs in clastics.
GR GR@ASCII_Load;1 [A326
0
6
300
DFL DFL@ASCII_Load;1 [A3
( gAPI )
CALI CALI@ASCII_Load;1 [
100
0.2
( in )
SP SP@ASCII_Load;1 [A327
16
0.2
( mV )
380
MD
1 : 200
m
200
( ohm.m )
HDRS HDRS@ASCII_Load;1 [
NPHI.WELLEDIT NPHI@ASCII
( ohm.m )
HMRS HMRS@ASCII_Load;1 [
200 0.54
( ohm.m )
200 1.8
0.2
1440
-0.06
( m3/m3 )
RHOB.WELLEDIT RHOB@ASCII
( g/cm3 )
DT DT@ASCII_Load;1
2.8 140
( us/ft )
40
K-IV Btm Coal
1450
KV-A
K-VA
K-VA Btm Coal
1460
KV-B
1470
K-VB
Drape
Scour Channel
Reworked distributary
channel sand
Reworked distributary
channel Sand
Base of channel
The red pattern indicates drape over the base of the
distributary channel.
Foreset beds
Foreset beds
Distributary Mouth
Bar
Foreset beds
Foreset beds
Bottom set
Bottom set
Change in dip azimuth in top and below of unconfirmity shows weathering took place
Unconfirmity
Thorium-Potassium plot indicate presence of Kaolinite &
Montmorillonite as main clay minerals in reservoir section
Highlighted points in thorium Vs potassium plot in Illitie
region are due to Coal present in the formation
Pulled by
Coal
Quartz to
Clay
Effect of
Montmorillonite
Pulled by Heavy
minerals
Formation water resistivity is 0. 23 ohm-m, also cross
checked by salinity of formation water
SRES SCALING PARAMETERS CROSSPLOT
Acoustic imager
It uses a rotating head that emits and receives an acoustic
signal. Both sound amplitude and its travel time are recorded,
giving images proportional to acoustic impedance and borehole
diameter respectively.
Array sonic logs
Allows visualization of the changes in amplitude and arrival time
of the three acoustic waves and emphasizes interference
patterns that indicate fractures.
Acoustic methods
DIPOLE sources
 Determine porosity and lithology in open & cased holes
 Fracture detection and characterization
 Obtaining mechanical properties- Bore hole stability during
drilling and production.
 Estimating permeability
 Gas Zone Identification/Evaluation
 Improving seismic processing and interpretation.
Rxo/Rt and SP
overlay
shows
good separation
in the gas bearing
layers
interval
2780-2812m and
2045-2055m
within 8 ½” and
12
¼”
holes.
VP/VS
vs.
Poisson’s
ratio
overlay
also
support the same
observation.
Correlation (PR & VPVS)
(Impedance - VpVs plot)
(Cambay Shale/Olpad/Trap)
Identified Olpad top
Prior
indicated Non-sanding zones: 2597-2602m, 2522-2532m Based
on Failure criteria derived from mechanical properties
Nuclear methods
 Improved determination of porosity and saturation in
both open and cased holes
 Major step toward lithology identification by a
combination of three types of nuclear spectroscopy
for in-situ determination of ten or more elements.
Nuclear Magnetic Resonance tools (NMR)
Actual working model (middle of 1990’s)
•
Nuclear magnetism log using spin echoes has made
possible for the first time measurements of lithology
independent porosity and irreducible water saturation
•
In-situ measurements of fluid diffusion coefficients,
estimation of permeability, and the most accurate
determination of residual oil saturation.
•
NMR and highly focused induction logs both come from
outside our industry
Why to use Nuclear Magnetic Resonance?





Lithology Independent porosity
Producible Fluid
Fluids Analysis
Capillary Bound And Free Fluid
Pore Size Spectrum
CMR
Light
Hydrocarbon
Sand with micro pores
where CMR 33msec
porosity matches with Elan
effective porosity(wet clay)
and CMR 3 msec porosity
matches with Elan effective
porosity (dry clay)
Clean water bearing sand
with CMR porosity (3msec
and 33msec) matching with
Elan effective porosity(wet
& dry clay)
Steps used
processing
in
ECS
1.
The
dry
weight
elemental
concentrations of Si,
Fe, Al, Ca and S are
used along with
neutron, density and
resistivity logs as
equations in the
inversion of mineral
and fluid volumes.
2.
Minerals
were
chosen based on
the
spectrolith
output volumes of
ECS along with core
data analysis in the
respective fields.
3.
ECS matrix density
was compared with
the Elan processing
output
matrix
density for the fine
tuning of the model.
MDT - Draw-Down Mechanism
Pressure
Invaded Zone
Quartzdyne Gauge (L)
Time
Drawdown
pump
Piston Position
Sensor
Packer
Back-up arm
Sample Isolation
Valve
Cased hole Scenario
 Reservoir description
 Completion integrity and fluid flow evaluations are much
enhanced over previous efforts
 Casing, tubing and cement image logs are readily
available. These can be used to their full extent in solving
well performance related problems.
 Production logging used in remedial work.
Analysis Behind Casing -Applications
Reservoir Analysis
 Find and Evaluate By-passed Pay / Un-swept Oil
 Re-evaluate after many years of Production
 Re-evaluate with new measurements
Reservoir Management
 Evaluate Depletion & Injection
 Evaluate Contact Changes
 Evaluate Saturation Changes
 Evaluate Pressure Changes
Analysis Behind Casing (ABC)
Well: A Mumbai Offshore
Services:
CHFR, CHFD, CHFP, RST,
DSI, ECS,USIT
Computes volumes of oil &
gas behind casing
• Reduced risk – Log after
lowering
casing
in
problematic wells (losses
etc.)
• Potential to evaluate old
wells that did not have logs
and Depleted Layers
L-I Top
GR
CHFD
CHFR
CHFP
L-II B
Top
Sw
(CHFR)
Cum Prod: 292978 bbl
Current Prod: 705 bbl/
day with 10% WC
CHFR-CHFP-CHFD–USIT-CBL
GR
CCL
Cement Map
Internal/external radius
VDL
Casing Collars
Good
Casing
Condition
Open Hole
Resistivity
Cased Hole
Resistivity from CHFR
Good Cement Quality
Good match
between
Open & Cased hole
resistivity in
overlapped section
As per CHFR
interpretation the
different layers of
the reservoir are
showing varying
degree of depletion
Analysis based on :
CHFR-CHFD-CHFP logs
At the top of layer a
secondary gas cap
formation is seen with
current
GOC
at
2123m(1318m TVDSS)
CHFR–CHFP–CHFD–USIT–CBL
Job on TLC
CCL
Cement Map
Internal/external radius
Good match
between
Open & Cased
hole resistivity
in overlapped
section
Good
Casing
Open Hole
Resistivity
Condition
Casing Collars
Cased Hole
Resistivity from
CHFR
VDL
Good Cement Quality
GR
Production Logging




To identify Layer wise contribution.
To Locate source of water.
Identification of thief zones.
To record bottom hole pressures
temperatures.
&
Production logging
Examples
Production
Logging
Examples
Well#X
BROWN FIELDS
Tractor PLT:
Horizontal Well
Major
H/C Entry
INTEGRATION
Integrated Environment
 Internet - integrating as well as a liberating force.
• Databases are more easily accessible
• Results & reports can be shared
• Work from anywhere
 Major application software available on Net.
 Group work or consulting via the Internet reduces the need
for many meetings.
 The only perceived snags are data security and loss of
control over employees, but these are capable of solution
with a little effort.
Benefits of Integration
 Integrated interpretation of logging, petrochemical,
geological, geophysical, and production data by
interactive workstations offer better understanding
 Expert systems, neural networks and other adaptive
systems have expanded the interdisciplinary approach to
field evaluation and optimize reservoir management.
 Evaluation of unconventional reservoirs viz. Shale gas,
CBM, Fractured Basement/Igneous rocks
Integration of Basic, CMR, SONIC and
Image log
Comparison of Logs, Litho-Quick Look,
Clusters, XRMI &Core data
Log
s
LQL
Dendrogram
Cluster XRMI
CORE
s
CC#1
Siltstone
Shale
Sand
Siderite
Silty
shale
(Core calibrated Litho-Quick-look vis-à-vis Litho-facies from Clustering
results & FMI)
Methodology for Realistic Evaluation of SW in Low Resistivity Low Contrast Sand
Lithological Model : Based Upon Sedimentological Studies
carried out.
Sandstone
: Quartz+Feld+ Calcitic Cement
Clay
: Montmorrilonite/Kaolinite, Chloritized biotite
Rock Fragments
: Low grade Metamorphic (slates,mica Schist, phyllite)
Fe-Heavy
: Iron Oxide (Magnetite/Haematite)
ELAN Processing parameters for model minerals firmed up.
Archie’s Petrophysical Parameters, analysed vis-à-vis low resistivity
contrast problem and standardized for use.
Innovative Technique to integrate SP in KCl mud with resistivity for
realistic SW computation implemented through GEOFRAME & ELAN
PLUS.
SW improved from 90-95% to 70-90% without use of SP and to 55-70%
With after use of SP
OWC
Porosity and Swi validated core studies in nearby well.
Computed clay volume variations follows GR log which is actually not
used in the processing due to risk of contamination from KCl mud.
Effective porosity variations more representative of natural depositional
processes.
OWC matches with regional OWC
Evaluation of Unconventional Reservoirs
Identification of Prospective Zones using logs
ISOPACH MAP OF OCS FORMATION IN STUDY AREA
Fracture Identification From logs in A Well
1. LLD, LLS
separation and
high GR against
fractured zones
2. Discontinuities/
waveform
attenuation.
Skipping on
sonic log.
3. Breakouts on
caliper log.
4. Fracture
porosity
computed from
LLD and LLS
separation
5. Well gave
85m3/d oil
Healed
fracture
Massive
Vesicle
Healed
fracture
Brecciated
Altered
Healed small
fault
Vesicle
(a)
Massive basalt, top part is vesicled,
only few irregular fractures are observed
(b)
Upper part is massive, middle part may be brecciated,
lower part is vesicled, few heal fractures are observed
Real time Monitoring
EVOLUTION OF WIRELINE TECHNIQUES
EVOLUTION OF WIRELINE LOGGING TOOLS
GET EQUIPED BY UPDATING
KNOWLEDGE & PRACTICES
AND
BRING SUCCESS
IN MEETING THE CHALLENGES
WISH A SUCCESSFUL JOURNEY
3/20/2012
WLS,AHMEDABAD
74