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ENHANCED RESERVOIR
CHARACTERISATION BASED UPON
BOREHOLE
IMAGES
&
DIPMETER
DATA
SAADALLAH GEOCONSULTANT AS
A. SAADALLAH Dr.
Misjonsveien 39, N-4024 Stavanger Norway
Tel. + (47) 51 52 62 65 (office)
Email: [email protected]
website: www.saadgeo.com
WARNING !
THIS PRESENTATION WAS
PREPARED IN 2005
IT HAS TO BE UPDATED BY
INCLUDING NEW TOOLS (such as
those of Weatherford) AND OTHER
ELEMENTS OF INTERPRETAION
ENHANCED RESERVOIR
CHARACTERISATION BASED UPON
BOREHOLE IMAGES & DIPMETER
DATA
OVERVIEW
1 Introduction
2 Dipmeter Tools
3 Imaging Tools
4 Borehole Map
5 Stereographic Projections
6 From Raw Data to Geologically Interpretable Outputs
7 Basic Interpretation
8 Clastic Reservoirs
9 In Situ Stress Issue
10 Fractured Reservoirs
11 Key Features to keep in mind
12 Key References
INTRODUCTION
From Logging & Petrophysic
point of view
to
a Geologic Mapping of the
Borehole Wall concept
Curve:
ONE value (Rock Propriety)
vs.
ONE Depth (MD)
From Logging & Petrophysic point of view to a Geologic
Mapping of the Borehole Wall concept
Dip needed very early in
Logging industry (Seismic not
yet performed or/and poor, Oil
goes up!)
From Logging & Petrophysic point of view to a Geologic
Mapping of the Borehole Wall concept
Curve: a value (Rock Propriety) vs. Depth (MD)
Dip needs a set of at least 3
measurements of the SAME
FEATURE: Dipmeter tool: 4
curves
From Logging & Petrophysic point of view to a Geologic
Mapping of the Borehole Wall concept
Curve: a value (Rock Propriety) vs. Depth (MD)
Dip needed very early in Logging industry (Seismic not yet
performed or/and poor, Oil goes up!)
Technology improvements: more data,
magnetometers, accelerometers, transmission
of data (pulse within mud) IMAGING
TOOLS: ca 100 000 measurements per Meter
MD: MAPPING OF THE BOREHOLE
WALL.
From Logging & Petrophysic point of view to a Geologic Mapping of
the Borehole Wall concept
Curve: a value (Rock Propriety) vs. Depth (MD)
Dip needed very early in Logging industry (Seismic not yet
performed or/and poor, Oil goes up!)
Dip needs a set of at least 3 measurements of the SAME FEATURE:
Dipmeter tool: 4 curves
From Logging & Petrophysic point of view to a
Geologic Mapping of the Borehole Wall concept
Curve: a value (Rock Propriety) vs. Depth (MD)
Dip needed very early in Logging industry (Seismic
not yet performed or/and poor, Oil goes up!)
Dip needs a set of at least 3 measurements of the
SAME FEATURE: Dipmeter tool: 4 curves
Technology improvements: more data,
magnetometers, accelerometers, transmission of
data (pulse within mud) IMAGING TOOLS: 100
000 measurements per Meter MD: MAPPING OF
THE BOREHOLE WALL.
From1 Dip in 1 day (1969
Sidi Ferruch Algiers)
1250 Dips measured (2004) a fractured reservoir
From 1 Dip in 1 day (1969
Sidi Ferruch Algiers)
To
1250 Dips measured (2004
fractured reservoir)
From FEW to
THOUSANDS of
MEASUREMENTS
That’s
DIGITAL GEOLOGY
New ways of thinking,
managing data, processing,
interpreting…and more
and more data…in real
time …new challenges for
geoscientists
Logging History Mile Stones: 1927 Figure 1.The first electric
log was obtained Sept.
27, 1927, on the
Diefenbach 2905 well,
Rig.No. 7,
at Pechelbronn,Alsace,
France.The resistivity
curve
was created by plotting
successive readings.
Logging History Mile Stones: 1947
1941: logging took another major step forward with the
introduction of the Spontaneous-Potential
Dipmeter.
1947: This measurement was improved further with the
Resistivity Dipmeter
1952: Continuous Resistivity Dipmeter
Logging History Mile Stones:
Imaging Tools 1968 BHTV (BoreHole TeleViewer) Mobil Acoustic...
1986: FMS (Formation MicroScanner) Schlumberger Electric...
1991 FMI (Fullbore Formation Microscanner) Schlumberger...
1994 RAB (Resistivity at the Bit) LWD Schlumberger...
2001 OBMI (Oil Base MicroImager) Schlumberger...
NEXT: high resolution imaging LWD tools (technical issue to
transmit data while drilling solved: WO (2007??)
Followed by other logging companies: Baker Hughes, Halliburton
MAIN DIPMETER TOOLS
Tool Name Main Technical
Characteristics Resolution
Logging Company
Name & Mud
Environment
SHDT
(Stratigraphi
c Dipmeter)
8 microresistivity electrodes on
4 pads (2 per pads)
Sampling: 0.1 in
Vertical
resolution: 1-2
cm
Schlumberger’s tool
Water-base mud
HEXDIP
(Hexagonal
Diplog)
6 microresistivity electrodes on
6 pads
Baker Hughes’ tool
Water-base mud
SED (Six
Arm
Dipmeter)
6 microresistivity electrodes on
6 pads
Halliburton’ tool
Water-base mud
TOOL Example:
SED (Halliburton)
HIGH RESOLUTION IMAGING TOOLS
Electrical and Acoustic
of the main logging companies
in petroleum industry BAKER HUGHES:
- STAR (electrical & acoustic)
- CBIL
SCHLUMBERGER:
- FMI (FMS)
- UBI
HALLIBURTON:
- XRMI (EMI)
- CAST
EMI FMI STAR
Use electrical responses of the formation to create Images.
Pad-based Microresistivity (conduct. mud),
sensitive to poor pad contact. Depth of investigation: 1 in.
Resolution linked with electrical contrast:
Bedding ca. 1 cm; Fracture ca. 1 mm (Resistivity Contrast)
4 Pads & Flaps
2 X 12 Sensors
192
75% of 8.5”
Arm configuration
Sensors
Coverage
Logging Speed 1800/1500 ft/hr
X-, Y-Spacing 0.1-0.2 in.
6 Pads
2 X 12 Sensors
144
56% of 8.5”
1200/2400 ft/hr
0.1 in.
6 Pads, 2 rows
25 Sensors
150
0.2 in.
58% of 8.5”
1800 ft/hr
Main Characteristics of Electrical Imaging Tools
CAST UBI CBIL
Acoustic response of the formation to build up images
Rotating transducer (Transmitter-Receiver)
Ultras. pulse 250-500 kHz. Water- and Oil-based mud,
100% borehole coverage, sensitive to borehole shape,
Depth of investigation: 0, Travel Time and Amplitude Attenuation
Resolve feature down to 1 in.
7.5 Rot /Sec
180 samples /rev
Vertical Sampling
rate & Logg. speed
Image Resolution 0.4 in at 250 kHz
0.2 in at 500 kHz
Main Characteristics of Acoustic Imaging Tools
1 in. 2100 ft/hr
0.4 in 800 ft/hr
0.2 in 400 ft hr
Measurements
0.3 in
1200 ft/hr
200 samples/rev 6 Rot/Sec
12 (STAR)
250 samples/rev
0.2 in
2400 ft/hr
TOOL Example:
FMI (Schlumberger)
BOREHOLE MAP
BoreHoleMap Borehole
Tool
Projection: Boreholemap
Tool within the Borehole: RB
Attitude of a plane in Space
Attitude of an axis in Space
Boreholemap representation: Sinecurve
Tadpole
BoreHoleMap: Orientation Borehole Axis DEVI: Deviation (inclination): Angle 00-90 Deg (from vertical to horizontal axis)
HAZI: Borehole axis azimuth: Angle 000-360 Deg (from N-000- to N -360 clockwise)
MD: Measured Depth
Tool Axis (Sonde Axis) DEVI: Sonde Deviation: Angle 00-90 Deg (from vertical to horizontal axis)
Sonde DEVI = Borehole DEVI
P1AZ: Ref PAD (PAD1): Azimuth PAD1 = Angle 000-360 Deg from North (000) or
from the BOREHOLE HIGH SIDE clockwise
MD: Measured Depth
0 90 180 270 3600
Y-A
xis
: M
D
X-Axis: Azimuthal & Perimeter
ORIENTATION of the BOREHOLE MAP
Y-AXIS:
- Borehole High Side
- Tool Frame
- North
& MD
X- AXIS:
- Borehole Perimeter
& Azimuthal
ORIENTATION of the
TOOL WITHIN the Borehole
Tool ROTATES (around the AXIS) its
EXACT position INSIDE the BOREHOLE
has to be known at EVERY measurement
RB: Relative Bearing:
Angle between the referenced-arm (P1AZ) and a fixed feature
(North, High side of the Borehole) is recorded at
every measured point
AXIS ATTITUDE in SPACE:
Dip/Dip-Azimuth
1. - Projection of core-features
onto a borehole map
2. - Projection of a planar-feature
onto the borehole map (Fault…)
3. - Projection of a linear-feature of a surface
onto the borehole map
(Striation on Fault-Surface)
Core Goniometry
Methodology
Projection of Core: Borehole Map
A reference line parallel
to the core axis
= master calibration line
with the MD
= Y-Axis
Orthogonal projection onto
a cylindrical surface = Borehole Map
Perimeter
= 2 P R
= 3600
= X-Axis (cm & Deg)
Projection of a Planar-feature
DIP-AZIMUTH
900 1800 2700
2P PR PR/2 3PR/2
PR
PR
Sine curve TOP
Sine curve BOTTOM
=DIP-AZIMUTH
Perimeter
=3600
=2PR R-0 cm
360-00
Master Calibration Line
DIP-AZIMUTH (cm or Deg)
relative to the master calibration line
Projection of a Planar-feature
DIP
900 1800 2700
2P PR PR/2 3PR/2 R-0 cm
360-00
Sine Curve
Amplitude
Tang DIP = Core Diameter
DZ
DZ
AXIS On Borehole Map
Fault Surface with Striation (Sandstone clast) in Shale
Projection of a Linear-feature
of a Surface onto the Borehole Map
900 1800 2700
2P
PR PR/2 3PR/2
R-0 cm
360-00
Tang DIP = Diameter of the Core
PR
DZ
DZ
DIP-AZIMUTH of the line relative
to the master calibration line
Projection of a Linear-feature
of a Surface onto the Borehole Map
900 1800 2700
2P
PR PR/2 3PR/2
R-0 cm
360-00
DIP-AZIMUTH of the LINE relative
to the master calibration line
TADPOLE
0 Deg 90 Deg
N (000Deg)
E (090 Deg)
S (180 Deg)
W (270 Deg)
15/225 Deg
10/135 Deg
STEREOGRAPHIC
PROJECTION
We are dealing
with DIP POPULATIONS
NOT with
INDIVIDUAL DIP
Analysing Dip Populations:
Stereographic Projections
SCHMIDT PROJECTION
Upper Hemisphere
Only ORIENTATION Matters
NOT the Spatial POSITION
UPPER HEMISPHERE
Vertical & Horizontal lines
Girdle of Lines
Vertical &
Horizontal
Planes
One Pop. Dipping
increasingly South:
GIRDLE
Lines
Schmidt
Net
Projection of a
Plane: Pole &
Cyclographic
Planes
Schmidt Net
Schmidt Net
Unimodal
Population
Unimodal Population
Bimodal
Population
GIRDLE: Population Related to Fault
GIRDLE: FOLD
Compass Rose 348.75 011.25
033.75
056.25
078.75
101.25
123.75
146.25
168.75
191.25
213.75
236.25
258.75
281.25
303.75
326.25
EE--WW EE--WW
NN--SS
NN--SS
NENE--S
WSW
NE
NE--S
WSWN
WN
W--SESE
N.N
EN
.NE
--S.S
WS
.SW
N.N
EN
.NE
--S.S
WS
.SW
E.NEE.NE--W
.SWW.SW
E.NEE.NE--W
.SWW.SW
N.N
WN
.NW
--S.S
ES.S
E
N.N
WN
.NW
--S.S
ES
.SE
W.NWW.NW--E.SE
E.SE
W.NWW.NW--E.SE
E.SE
NW
NW
--SESE
090270
180
360/0
045
135
225
Dipping Striking
348.75…011.25: N E-W
011.25…033.75: N.NE W.NW-E.SE
033.75…056.25: NE NW-SE
056.25…078.75: E.NE N.NW-S.SE
078.75…101.25: E N-S
101.25…123.75: E.SE N.NE-S.SW
123.75…146.25: SE NE-SW
146.25…168.75: S.SE E.NE-W.SW
168.75…191.25: S E-W
Dipping Striking
168.75…191.25: S E-W
191.25…213.75: S.SW W.NW-E.SE
213.75…236.25: SW NW-SE
236.25…258.75: W.SW N.NW-S.SE
258.75…281.25: W N-S
281.25…303.75: W.NW N.NE-S.SW
303.75…326.25: NW NE-SW
326.25…348.75: N.NW E.NE-W.SW
348.75…011.25: N E-W
315
From RAW Data to
GEOLOGICALLY
Interpretable Outputs
Main Processes
Raw data, microresistivity measurements recorded by electrode tool,
need to be processed:
Speed correction,
Magnetic declination correction,
Depth shift offset (when it is needed)
Generation of image/dip logs.
Main Processes Speed correction, convert data, recorded vs. time into data vs. depth
&
correct depth offset due to oscillations along the axis tool.
Oscillations are caused by irregularities of the borehole or in fact due
to the none-constant speed of the tool while running the logs.
Generally, a sliding window of 10 ft is used for an average cable speed
of 1600 ft/hr.
SPEED CORRECTION: is applied
to correct for erratic tool motion
& convert data recorded in time to depth
T0 T0
T1 T1
T2-7 T2-7
T8
Y A
xis
: M
D
0 90 180 270 3600
T0 T0
T1 T1
T2 T2
T3 T3 0.2 in.
IN THEORY: Tool moves up the
borehole recording measurement-sets
At regular timing (T0 – T3)
IN REALITY: Tool moves ERRATICALLY up
the borehole recording measurement-sets at
regular timing (T0 – T3)
Main Processes
Magnetic declination correction, applied to inclinometry measurements
recorded by the tool (relatively to the
magnetic North) to convert them to
Geographic North.
Main Processes Depth shift offset (when it is needed)
Correlation of GR from another Run (Wireline Log) & GR from FMI
Geological Feature determined from other sources
Main Processes Generation of images Static normalised images (called Static Images):
computation carried out in a window covering all the
logged section.
Dynamically normalised images (called Dynamic Images):
sliding window (5 Ft).
Scale in the range white-yellow-brown-dark :
white-yellow: minimum conductivity
To
brown-dark: maximum conductivity.
QC: Depth Match, Static & Dynamic Images
Geological Features: Bed Boundary, Bedding
Dynamic Image
QC: Depth Match, Static & Dynamic Images
Geological Features: Bed Boundary, Bedding
Dynamic Image Static Image
QC: Depth Match, Static & Dynamic Images
Geological Features: Bed Boundary, Bedding
Dynamic Image Static Image
Calipers
QC: Depth Match, Static & Dynamic Images
Geological Features: Bed Boundary, Bedding
Dynamic Image Static Image
Calipers
GR
QC: Depth Match, Static & Dynamic Images
Geological Features: Bed Boundary, Bedding
Dynamic Image Static Image
Calipers
GR
RHOB
QC: Depth Match, Static & Dynamic Images
Geological Features: Bed Boundary, Bedding
Dynamic Image Static Image
Calipers
GR
RHOB
NPHI
QC: Depth Match, Static & Dynamic Images
Geological Features: Bed Boundary, Bedding
PROCESSING of
DIPMETER
DATA
Measurements
recorded by pads
during the run
Represented by
resistivity curves
specific to each
pad
are correlated
during
the process
(spikes)
Correlation
process will fit a
plane & compute
its dip/dip-
azimuth
Processing Dipmeter Data: -1 m sliding window (1600 ft/hr average cable speed
- Corresponding step: 0.5 m
- Search angle 70 Deg
Window
length (cm)
Step length
(cm)
Max. Search
Angle relative
to borehole
Deg.
Computed log
name Comments
100 50 80 Hex100X50X8
0
Computed log
used for
interpret dips
stored in a new
log named
INTERPR100
60 30 60 Hex60X30X60
20 10 40 Hex20X10X40
Processing Dipmeter Data: -1 m sliding window (1600 ft/hr average cable speed
- Corresponding step: 0.5 m
- Search angle 70 Deg
Dip Log: Computed Dips Only
High & Low Confidence
Noise
Poor Data Intervals
From Atlas of Borehole Imagery Ed L.B. Thompson Aapg 2000
QUALITY CHECK
From LOADING
To
FINAL INTERPRETATION
Dynamic Image Static Image
Calipers
GR
RHOB
NPHI
QC: Depth Match, Static & Dynamic Images
Geological Features: Bed Boundary, Bedding
Other Points:
Repeat Section (200 ft MD)
Tool Rotation (less than one turn per 30 ft)
Slip-Stick Behaviour
Raw data in original format (LIS, DLIS)
Field Print (orientation, Pad#, Magnetic
Declination Value, Correction (Not Done)
IF Orientation Don’t Fit with Previous Field Model ?
Comparison with OTHER RUNS
Geology is the BEST QC
Tool has picked the “wrong” North?
Rotation of the Dip Log, around the borehole axis
(Same Methodology as in Core Goniometry)
Assume the Same Error during all the RUN
ROTATION Vertical Borehole
DIP remains the Same
DIP-Azimuth Changes
ROTATION Deviated Borehole
BASIC
INTERPRETATION
INTERPRETATION:
3 Steps
1: Collecting Geologic Data
2: Analysing Dip Populations
3: Correlating Geologic Features
INTERPRETATION Step 1
Collecting Geologic Data
-1) Diptype Listing
-2) Image Quality
-3) Zonation Based on Image Fabric
Highlighting:
-4) Lithology (Sedimentology) Facies
-5) Deformation Facies
DIPTYPE LISTING:
3 Geologic Surface Types:
-1) Sedimentologic
-2) Structural
-3) In Situ Stress Features
Identification of Geological Features Picked out directly from images &/or inferred
Sedimentological features:
- Bedding planes Structural-Dip, Paleo-Horizontal Dip
- Cross-bedding Paleo-Transport Directions, Deposi-
- Unconformities tional environments
- Image facies Help define reservoir units
Tectonic features:
- Faults: Fault-block rotation, strike-slip component
- Fractures: Fracture analyses of reservoir:
Fracture population characterisation, fracture
densities, Maximum fracturing directions
- In-situ Stress features: Breakout, Tensile Fractures
In Horizontal wells: syncline & anticline structures,
younging direction, Bedding-plane-correlation
to constrain reservoir zonation
SEDIMENTOLOGIC Features Listing PARTICULAR to a RESERVOIR
Related to data from other sources (Cores,
Petrophysics, Seismic, Field Studies) to help
CORRELATE
Dynamic Image Static Image
Calipers
GR
RHOB
NPHI
Bed Boundary
QC: Depth Match, Static & Dynamic Images
Geological Features: Bed Boundary, Bedding
FMI
Dynamic Image Static Image
Calipers
GR
RHOB
NPHI
Bed Boundary
Bedding
QC: Depth Match, Static & Dynamic Images
Geological Features: Bed Boundary, Bedding
FMI
Calipers
GR
RHOB
NPHI
Foreset Boundary
Cross
Bedding
Bed Boundary
Foreset
Foreset, Foreset Boundary & Cross Bedding
FMI
Calipers GR
RHOB
NPHI
SS
Bedding
Heterolithic
Bedding
Shale
Bedding
Shale Bedding, SS Bedding & Heterolithic Bedding
FMI
TECTONIC Features Listing PARTICULAR to a RESERVOIR
Related to data from other sources (Cores,
Petrophysics, Seismic, Field Studies) to help
CORRELATE
Part of a Diptype List (Fractured Reservoir)
Diptype Name,
(Correspondent
Geological Notion),
colour used in plots
and Fig., and
Illustration (Go to Fig
#)
Description & Correlation with Geological
Feature Comments
FAULT
(Fault), Red
GoToFig11
Narrow or large, and discrete resistive or
conductive anomaly displayed along a sub-
planar feature cutting sedimentologic planes.
Also, a clear cut off the bulk resistivity,
highlighting a plane considered as a fault
plane.
Fault is differentiated from
Fracture.
BEDDING
(Bedding),
Green
GoToFig12
Change in the bulk conductivity along a
planar boundary at the lowest scale of the
image, i.e. centimetre scale. Regularly
repeated planar features corresponding to
current bedding planes.
The current bedding planes are
generally parallel to bed boundary
and regularly repeated in the bed or
layer.
Confusion sometimes with Shale
Bedding, Bed Boundary and
Stylolite
Fault, Bedding, BedBoundary m MD, Vertical Well, Scale: V=H FMI processed &
interpreted with
Recall
Reverse Minor Fault
with a ca 15 cm throw
Examples of
Geological Features
Bedding plane
in the Hangingwall Block
The same Bedding plane
in the Footwall Block
Minor Fault
Fault Interpreted as a
probable
Reverse Fault
FMI
From Atlas of Borehole Imagery Ed L.B. Thompson Aapg 2000
HORIZONTAL WELLS
Younging Direction in Horizontal Well Younging Direction
Downward Upward
Cross section
of anticline
drilled by a
Horizontal Well
Younging direction
inferred from
the shape of
the sine curve
TD
Inward direction Outward direction
Bedding Plan Correlation: a methodology to
help define reservoir units
Younging Direction -INTERVAL without fault
picked out
-SHORT interval
- A BEDDING PLANE ,
bounding reservoir units
picked and choosen as
STRATUM GUIDE
- Locations where Stratum
guide is cut
DOWNWARD
or UPWARD
are picked out To be Performed Carefully!
Bull’s eye structure in Borehole Images
of Horizontal Well:
= Anticline structure
= Inflexion of the well-track (concave profile)
Or Outward direction
Inward direction Inward direction
Borehole high side
Wood-Grain structure in Borehole Images
of Horizontal Well:
= Syncline structure
= Inflexion of the well-track (convex profile)
Or Outward direction
Inward direction Inward direction
Borehole high side
From Atlas of Borehole Imagery
Ed L.B. Thompson Aapg 2000
From Atlas of Borehole Imagery
Ed L.B. Thompson Aapg 2000
Cross Bedding, Closed Fracture m MD, Vertical Well, Scale: V=H FMI processed &
interpreted with Recall
Discontinuous & Continuous Fractures m MD, Vertical Well, Scale: V=H
FMI processed &
interpreted with
Recall
IN SITU STRESS
CHARACTERISATION
Tensile Fractures (Images)
Borehole Breakout (Images)
Borehole Breakout (Calipers)
Constrain the entire Population
Determination of the SHmax Direction
From Atlas of Borehole Imagery Ed L.B. Thompson Aapg 2000
Borehole Breakout (from Calipers)
Criteria to Constrain
1) Tool Rotation < 30 Deg
2) Caliper Difference > 0.5 in
3) Smaller Cal > BS-1.5 in
4) Bigger Cal > BS
5) Avoid Key Seat ovality (angle
> 15 Deg)
SHmax
Determination :
Plotting All to Get
Global Picture
QUALITY IMAGE ZONATION
Poor Intervals are flagged
IMAGE FABRIC ZONATIONS
Image Fabric might be related to Geological
Features… Interference of tool behaviour (&…)
Zonation Uncertainty…calibrated, correlated…
Zonation Helps define reservoir features:
1)Highlighting Matrix (Sedimentologic, Lithology): Thinly Bedded, Nodular, Vuggy…matrixes
2) Highlighting Deformation Facies (Stylolite
Associated Fractures, Fracture Zone 1…)
LITHOLOGY ZONATION
Highlighting Matrix (Sedimentologic, Lithology): Thinly Bedded, Nodular, Vuggy…matrixes
Example of Image Fabric Zonation
Highlighting Matrix Characteristic
Zonation Name & Colour
used to flag the
corresponding interval,
and Illustration (Fig)
Description & Correlation with
Geological Features and Events Comments
Thinly Bedded
Matrix (Red)
GoToFig11
Interbedded matrix with thinly bed including
cross bedding. It is possible to pick every 5
cm a bedding surface.
This layer might be rich in
clay, shale, fine grain that
might be a horizontal barrier to
fluid displacement.
It can be used to determine the
Paleohorizontal dip if
necessary.
Nodular Matrix
(Green) GoToFig12
Conglomerate-shaped matrix with resistive
nodules. This might be related to
conglomerates or not, it has to be calibrated
with other data sources (cores, mud logs,
field studies…). Resistive nodules might be
related to some anisotropic proprieties of the
matrix or to some tight features.
The resistive spots are
considered as tight or close
therefore not used by fluids as
porosity.
On the contrary, the “matrix”
between the resistive spots is
conductive so it is considered
as actual/potential significant
porosity
Zonation Highlighting Sedimentology
Image Fabrics:
Thin Bedded
&
Bioturbed
m MD, Vertical Well, Scale: V=H FMI processed &
interpreted with Recall
Vuggy Matrix
Important Features:
Isolated
Interconnected
Size (Relatively)
Up Grading
Down Grading
(Correlation
with Flooding
Surfaces)
Intersected by
Deformed Zones
Scale
Rudist Shuaiba (Cr)
Bu Hasa Field (Abu
Dhabi)
DEFORMATION FACIES
ZONATION (Stylolite Associated Fractures, Fracture Zone 1…)
Example of Zonation Highlighting
Deformation Features, Stylolite & Karstic Associations, and Poor Images
Zonation Name &
Colour used to flag
the corresponding
interval, and
Illustration (Fig)
Description & Correlation with
Geological Features and Events Comments
Poor Image
(Red)
GoToFig11
Image is of poor quality, high to moderate
uncertainty in the interpreted features of the
flagged interval.
Poor quality of image correspond
often to washout intervals
Stylolite
Associated
Fractures
(Green)
GoToFig12
Tiny Fractures (up to 20 cm vertical-length)
sub perpendicular to Stylolite surface,
occurring in the lower side, or upper side or
both sides of the stylolite surface. Fractures
are striking in all azimuths (radial) or in
particular azimuths: it is not clear.
Sometimes a couple of stylolite surfaces
with their associated fractures are close
enough to constitute a Stylolite Zone
This zone, subhorizontal might play a
positive role in draining fluids
horizontally.
Such feature is known as used by fluid
paths in some carbonate reservoirs.
It might be considered as “pipe-layer”
parallel to the Stylolite surface.
If crossed by Fracture Zone or
Fractured/Cataclastic zone this might
increase the draining propriety.
The question is about the role
regarding vertical path of fluids:
obstacle or drain?
Stylolite Associated Fractures m MD, Vertical Well, Scale: V=H
FMI (Processed &
Interpreted with Recall)
INFERRED Features
By Analysing Dip Populations
Examples:
Girdle: Inferred faults
Bimodal: Unconformities
Paleohorizontal dip
Structural Dips: Per Units,
Logged Section
Structural Dip & / or Paleo-Horizontal Dip: ?
“...Dips with constant magnitude and azimuth in a low energy environment
can be selected. They correspond to the groups of beds, whose bedding planes have not
undergone any biogenic or tectonic alteration. It can reasonably be assumed that these
beds were deposited on nearly horizontal surfaces and that their present dips are the
result of tectonic stresses” Tire de Serra, O. 1985, “Sedimentary environments from
wireline logs”.
“By Structural dip is intended the “general attitude of beds”. It is the dip that would
be measured at outcrop. It is usually the dip seen on seismic reflectors, themselves a
generalisation. It avoids any sedimentary structures of any size and is generally
considered to represent the depositional surface which also is considered to be
horizontal.” Tire de Rider, M. H. 1996 “The geological interpretation of well logs”
I call it: PALEO-HORIZONTAL DIP
I call it: STRUCTURAL DIP
Paleo-Horizontal Dip, as is suggested by the name, is the dip of bedding planes that
were originally deposited horizontally. Low energy sediments such as shale, planktonic
sediments and coals, in specific conditions, can be assumed to be deposited
horizontally.
Such bedding planes may be used to infer tectonic events such as uplift, tilting or fault
block rotation.
Structural dip is restricted to the mean dip of a lithological formation that can be used
in geological (structural) cross-section, or related to a specific marker that can be
correlated to a seismic one, avoiding detailed sedimentological structures at small
scale. The dip and associated dip-azimuth can be used to infer the geometry of the
units, for structural purposes at rather bigger scale, no matter what its genetic origin,
or what events the unit has previously undergone.
PALEO-HORIZONTAL DIP
STRUCTURAL DIP
The way I see it, and use it in my interpretation:
Paleo-Horizontal Dip: Interval of Low Energy Deposits
Paleo-Horizontal Dip: Whole Dip-type Population
of Low Energy Deposits
Structural Dip: Several Dip-type Populations: Bed
Boundary, ...
PALEOHORIZONTAL DIP Implemented to Rotate Out Dips
After Rotation
Before Rotation
CROSS
BEDDING
(After Gareth, G.; 2000, in PESGB Newsletter)
Terminology used in FMI image interpretation
Foreset Boundary
Cross-Bedding Planes
Foreset Boundary
Foreset Boundaries
&
Cross- Bedding
are Parallel (Planar
Cross Bedding)?
= SS Bedding
Track-tadpole presentation
Cross-section presentation
PALEOCURRENT
DIRECTIONS
Paleocurrent directions: ONE DIRECTION
in
ONE SET
Paleocurrent directions: DIRECTIONS in
ONE SET
PALEOCURRENT DIRECTIONS
GLOBAL
RESULTS
Major Minor
Cross Bedding
Interval Method
Whole Pop.
SS Bedding
Interval Method
Whole Pop.
Heterolithic
Whole Pop.
Paleocurrent directions: Global Results
PALEOCURRENT
DIRECTIONS
Vs
GEOLOGIC TIME
Ex. 1: SAME DIRECTION Paleocurrent directions are stacked up from
bottom to top:
-Bottom (Dark Blue)
-Middle of the unit (Green)
-Top (Yellow)
Ex. 2: CYCLE Re-Considering the previous example (Global
Result)
Major Minor
Cross Bedding
Interval Method
Whole Pop.
SS Bedding
Interval Method
Whole Pop.
Heterolithic
Whole Pop.
Paleocurrent directions: Global Results
Paleocurrent Directions (from O to 360 Deg)
S
N
N
E
W
Geological
Time
Northerly
Paleocurrent
Cycle
N
S
W-SW
S
Final Result: Distinct Stacked Paleocurrent cycles
W
N
PaleoHorizontal Dip Implemented to
Constrain Fault Block Rotation
PaleoHorizontal Dip Implemented to
Constrain Fault Block Rotation
Unconformity from Bimodal Bedding
Population: whole section
Unconformity from Bimodal Bedding
Population: Upper Unit
Unconformity from Bimodal Bedding
Population: Lower Unit
Geometry
of the
whole
section
INFERRING
GEOLOGIC
FEATURES:
FAULTS
Fault
Pattern
FAULT: Picked & Constrained (girdle) 1of2
FAULT: Picked & Constrained (girdle) 2 of 2
Constraining a Normal Fault with Roll Over 1of 2
Constraining a Normal Fault with Roll Over 2 of 2
Key References