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S C A L I N T E R P R E T A T I O N
We have particular expertise in routine and Special Core Analysis
interpretation, including residual hydrocarbon and saturation-height
definition using both laboratory and field data.
Studies carried out typically follow the processes outlined below,
resulting in the applications presented. These applications typically
have the benefits shown for clients. Some notes are given to clarify
some of the processes, while an example is included to illustrate what
is possible.
Processes
Data Collation
Check Data Representative
Corrections & Conversions
Quality Control & Consistency
Data Analysis
Uncertainty Determination
Reconciliation with Logs
Software Implementation
Applications
Grain Density Definition
Ambient to In-Situ Porosity and Permeability Transforms
Porosity-Permeability Relations (ambient and in-situ)
Clay Conductivity Correction
Cementation and Saturation Exponent Definition
Residual Hydrocarbon Definition
Irreducible Water Saturation Definition
Drainage Saturation-Height functions
Imbibition Saturation-Height functions
Benefits
Core-Based Wireline Log Evaluation Parameters
Independent Check on Wireline Log Evaluations
Hydrocarbon Saturations when Resistivity Logs Absent or Unreliable
Water Saturations in Thin-Bedded Reservoirs
Contact Location
Uncertainties at Required Probability Limits
Differentiation of Swept Zones from Poor Quality Reservoir
Static (Geological) & Dynamic (Simulation) Model Initialisation
Improved HCIIP & Reserves Definition
Notes
Different laboratory measurement techniques of various vintages and
origins can normally be interpreted in a consistent way. Even
“old” data has some value.
Data must be in a common reference frame before being compared i.e. at
the same stress conditions and using the same fluids. Transforms are
used to move data measured in one system to another.
Quality control is usually implemented using a data consistency
approach i.e. measurements that diverge from Formation trends suggested
by the majority of the data are examined and discarded if appropriate.
The number of samples discarded should be minimised, with the
uncertainty analysis dealing with most variation.
Uncertainty is a key component of data analysis. The range of possible
values is defined where possible. The uncertainty bands used can be
customised to suit client requirements.
Saturation-height functions can be based on porosity or permeability in
addition to height (above a FWL). Permeability based models typically
have a smaller uncertainty range.
Models must always be tested against Field data.
Example
Porosity based drainage and imbibition saturation-height functions are
compared with the client’s wireline log evaluation. The red SWT
curve is the log-based water saturation, while the green SWI curve
shows the residual hydrocarbon relation at the base of the column and
the imbibition based water saturation at the top of the column. The
blue SWD curve is the drainage saturation-height function i.e what the
column would have looked like had there been no production. The match
is excellent.
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