M5 Log Upscaling

Module 5

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Upscaling of Well Logs

Objectives



Gain an understanding of the concept and process



Understand and use discrete logs

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Averaging methods

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Facies weighting.



Understand and use continuous logs

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Averaging methods

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Biasing to a discrete log.



Look at different Scale-up settings

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Treat log as lines or points

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Method of which penetrated cells to use.

Overview

Cells exist along the well path. Values assigned to cells based on well log values along the well path.

Upscaled logs used to fill in the 3D grid.

The Scale-up well logs process averages the values to the cells in the 3D grid

that are penetrated by the wells. Each cell gets one value per upscaled log.

These cells are later used as a starting point for Property modeling.

Scale-Up Well Logs

Note: Upscaled logs will be part of the 3D property at the well

positions. The Property modeling processes will NOT overwrite upscaled cell values!

1. Create a new property.

3. Choose a log from the drop-down list (captured from Input pane > Global well logs folder) 4. Set the best scale-up Settings, depending on

the type of log (continuous or discrete). 2. Select Input from Well logs.

5. Click Apply or OK.

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Commonly used Averaging Methods

Averaging

method

Description

Most of Used together with discrete logs, it selects the discrete value that is most represented in the log for each particular cell.

Arithmetic mean Typically used for additive properties, such as porosity, saturation, and net/gross.

Harmonic mean Gives the effective vertical permeability if the reservoir is layered with constant

permeability in each layer. It works well with lognormal distributions and is sensitive to lower values.

Geometric mean Normally a good estimate for permeability if it has no spatial correlation and is lognormally distributed. It is sensitive to lower values.

Averaging Discrete Logs

Discrete logs, such as facies, have only

integer values (0,1,2, etc.).

2. The Average method is normally Most of, which uses the value most represented in the cell. 3. In some situations, it may be necessary

to use the Weighting option. Click Use

weighting and fill in the Weighted tab.

1. Choose an input from a Facies well log to create a new property.

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Averaging Continuous Logs

Continuous logs, such as porosity, have real

number values (decimals).

4. Specify that there should be a Minimum number of well log samples in a cell for it to be included in the upscaling.

2. Set the Average method (here Arithmetic for porosity). 3. It is possible to bias to an already upscaled facies log.

1. Choose an input from a continuous Well log to create a new property (here, porosity).

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Biasing to a Discrete Log

Raw porosity

Upscaled facies Raw facies Upscaled porosity

Sand

Settings: Treat Log as Lines or Points

Treat log

Description

As points All sample values within each cell are used for averaging.

As Lines If the midpoint of a line between two sample points is inside a cell the point outside the cell will be used in the calculation.

Settings: Method of Which Penetrated Cells to Use

Method Description

Simple All cells penetrated by the well trajectory are included.

Through cell The well trajectory must penetrate two opposite cell walls.

Neighbor cell All penetrated cells are used but cells in the same cell layer are averaged.

Quality Checking Upscaled Logs

When upscaling is done, it is a good practice

to QC the upscaled cells with the original log

in a Well section window.

1. Click the Show result in well section button in

the Scale up well logs dialog.

2. Display the upscaled log in the same track.

Right-click on the upscaled log (Models pane>

Properties folder) and click Add to template in

the existing raw log track.

Alternatively, set up a Well section display on

your own. Choose raw logs (Global well logs

folder > Input pane), right-click, and select Add

to template in a new track.

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Averaged values for each cell in the model on top of the original log

Upscaling of Well Logs: QC of Upscaled Logs

Synthetic logs resemble the properties (Upscaled logs) but are stored as physical

logs under Global Well Logs.

1. Click the Make logs tab of settings for Wells.

2. Choose the property from which the log will be made. 3. Click the Make logs button. The log is stored in the Global

Averaging Methods for Discrete Logs

Averaging method Description

Most of Will select the discrete value which is most represented in the log for each particular cell

Median Will sort the input values and select the center value.

Minimun/Maximum Samples the min/max value of the well log for the cell.

Mid Point Pick Will pick the log value where the well is halfway through the cell.

Averaging Methods for Continuous Logs

Averaging method Description

Arithmetic mean Typically used for additive properties such as porosity, saturation, and net/gross.

Harmonic mean Gives the effective vertical permeability if the reservoir is layered with constant

permeability in each layer. It works well with log normal distributions. It is sensitive to lower values.

Geometric mean Normally a good estimate for permeability if it has no spatial correlation and the is log normally distributed. It is sensitive to lower values.

Median Sorts the input values and select the center value.

RMS (Root Mean Squared)

Provides a strong bias towards high values.

Minimun/Maximum Samples the min/max value of the well log for the cell.

Mid Point Pick Picks the log value where the well is halfway through the cell.