Reservoir Correlation

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3D STATIC RESERVOIR MODELLING
COURSE
Reservoir Correlation
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2. RESERVOIR CORRELATION
This module includes the following topics:
Overview: Correlation Methods and Tools
 Sequence Stratigraphy
 Tools
Sequence Stratigraphic Correlation Methodology
 Flooding surfaces
 Sequence Boundaries
Correlation Techniques

3. Correlation = Connectivity
RESERVOIR CORRELATION: DEFINITION
Correlation is of fundamental importance to Reservoir Modelling
“A connection of points from well to well in which the data suggests that the
points were deposited at the same time (chronostratigraphic) or have similar
and related characteristics.”
- Schlumberger Oilfield Glossary
By creating a geologically realistic correlation
framework, you are defining the pathways of
static connectivity.
Correlation is the main process where
geological knowledge is input by the user to
control the architecture of the model.
Reservoir Geology Consultants
Reservoir Geology Consultants

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RESERVOIR CORRELATION IS MODEL DRIVEN
The depositional model is used to guide correlation. Make sure it is
correct!
Reservoir Geology Consultants
Reservoir Geology Consultants

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GEOLOGICAL KNOWLEDGE TO MAKE REALISTIC
CORRELATIONS
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Reservoir Geology Consultants

6. CORRELATION METHODS: SEQUENCE STRATIGRAPHY
Components and Hierachy
Seismic Driven
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7. CORRELATION TOOLS
Dating Typing/Tools
 Biostratigraphy
 Magnetostratigraphy
 Chemostratigraphy
 Mineral Provenance Studies
 Analysis of the Sm-Nd ratio
 Radiogenic Isotope Analysis
There are hardly any tools that work well on their own. It is always
better to use them in combination.
Most techniques are affected by diagenesis! 7

8. BIOSTRATIGRAPHIC CORRELATION: NELSON FIELD UK NS
Forties Formation Deepwater Turbidites
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BIOSTRATIGRAPHIC CORRELATION: MARMUL FIELD
OMAN
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Glacial Sediments (Carboniferous age 300 MA)
Heterogeneous
Variable poor to excellent reservoir quality (0 -
10D+)
Al Khalata Formation Glacial Deposits
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10. OTHER CORRELATION TOOLS
Reservoir/Production Data
 Pressure data
 Interference +/or tracer tests
 Geochemistry
 Well tests
 Minimum connected volume
 Distance to barriers
 Pressure support/recharge
 Cumulative production – minimum connected volume?
 PLTs – which zones flow, where are the vertical barriers?
Connection CW12- CP03
Indicated by:
Pressure interference test
Chemical tracer
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HEAVY MINERAL AND GEOCHEMICAL CORRELATION
TRIASSIC CNS
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CHRONOSTRATIGRAPHIC VS LITHOSTRATIGRAPHIC
CORRELATION
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FLOODING AND SEQUENCE BOUNDARIES:
IDENTIFICATION FROM LOGS
Look for the Major Flooding
Surfaces (MFS) to define the
correlation framework (may be
several stepped progradational
sequences)
How to recognize sequence
boundaries?
may sometimes be
recognised by sharp base?
recognised by field wide
occurrence?
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Reservoir Geology Consultants
Reservoir Geology Consultants
CORRELATION: HINTS AND TIPS

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Use well sections and
polygons
Start with a type log
Correlate in circular
polygons, since working
within adjoining polygons
ensures that a correlation is
robust in three dimensions,
which is a critical
requirement of modelling
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Reservoir Geology Consultants
CORRELATION: HINTS AND TIPS (CONT.)

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Plot 3-D facies distribution on a
map – helps to visualise reservoir
body extent.
Faulted-out
Faulted-out
F
F
Valley-Fill Sand
Upper Shoreface
Sand
Lower Shoreface
Sand
Shale
CORRELATION: HINTS AND TIPS (CONT.)
Reservoir Geology Consultants
Reservoir Geology Consultants

17. FACIES RECOGNITION FROM WELL LOGS
Log Character
 GR shape
 FDC/CNL seperation
 Sonic response
Can be subjective (geologist
dependant)
Neural Net work (Techlog)
 A computer aided facies reconition
 Trained on cored wells
Auditable and repeatable
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18. CORRELATION: COMMUNICATION BETWEEN DISCIPLINES
The description of the subsurface varies
between different disciplines:
Where is "top" reservoir?
 Geologist thinks depositional model
 Petrophysicist thinks reservoir
 Geophysicist thinks seismic
response
Potential mismatch between the
petrophysical, geological and acoustic
models.
 Leads to misties on surfaces
 Incorrect volumetrics
 Implications for drillingnse
Solution: Communicate!
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19. CORRELATION
What observations can you make from
these three Nigerian wells?
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20. CORRELATION AND GROWTH FAULTING
Impact of growth faults on deposition
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21. Reservoir Geology Consultants
FAULT IDENTIFICATION FROM WELL CORRELATION
Missing section due to fault
cut-out (dramatic thickness
change).
Correlate downward and
upward to find exact fault
position.
Check seismic for fault
position
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22. WHERE TO GET HELP?
https://a100.sharing.shell.com/sites/b056f6c266eb4512b0bc175608b7b302/clastic
s/knowledgeBank/principles/correlation/default.aspx
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