day 4 m14 log upscaling 2008

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WellCorrelation

Petrel Workflow Tools

5 Day Introduction CourseFault

Modeling

Well DesignVolume

CalculationPlotting

Pillar Gridding

Depth ConversionEdit of Input

I n t r o t o P e t r e l

E d i t I n p u t D a t a

I m p o r t d a t a

W o r k f l o w E d i t o r

Seismic

Introdution to Property

Modeling; Log Upscaling



Upscaling of Well LogsObjectives

Gain Understanding of Concept and Process

Understand and Use Discrete Logs

± Averaging

Understand and Use Continuous logs

± Averaging ± Biasing to a discrete log

± Different averaging methods

Look at Different Scale-Up Settings

± Treat log as lines or points

± Method of which penetrated cells to useQC of Upscaled Logs

± Using well section window



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.

Upscaling assigns values to the cells in

the 3D grid that are penetrated by the

well logs. It averages the values so that

one cell gets one value only. These cells

are later used in Property modeling.



Process

Select the Scale up well logs process under the

Property Modeling folder in the Process Diagram.

NOTE: The upscaled logs will be part of the 3D

property at the well positions. Property Modeling

processes will NOT overwrite upscaled cell values!

1. Cr eate new pr oper ty and Select input

from: W ell logs.

2. Select log: from drop-down menu

(captured from Global well logs folder)

3. Select the best Scale up settings



Discrete Logs ² Averaging

Discrete logs, such as facies, have only

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

1. The Averaging method is normally

Most of (will use the value which is most

represented in the cell).

2. In some situations it may be necessary

to use the weighting option. Click the Use

weighting and fill in Weighted tab.



Continuous Logs ² Averaging

Continuous logs, such as porosity, have real

number values (decimals).

3) You can specify that there

should be a Min. number of points passing through a

cell for it to be populated

with a value.

1. Select the Average method. It is

normally Arithmetic for porosity (averages

all the values in the cell equally).

2) It is usually necessary to bias to facies.

Use the biasing option, to bias against a

discrete upscaled log (see next slide).



Biasing to a Discrete Log

Raw facies Raw porosityUpscaled facies Upscaled porosity

Sand



Settings ² Treat Log

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

As lines: Data between points will be interpreted (points outside the

cell may affect the result).

vi: weighted value of eachpoint involved

ni: log value of the point



Settings ² Method

Simple: All cells penetrated by the well

trajectory are included

Through cell: The well trajectory must

penetrate two opposite cell walls (top and

base - opposite sidewalls) to be included

Neighbor cells: Cells in the same cell

layer are averaged.

Option to set aminimum number

of data points in a

cell for it to be

included.



QC of Upscaled Logs

Once upscaling is done it is a good habit to QC

the upscaled cells with the original log:

Press the Show results in Well Section or set up

a Well Section display on your own (discussed

below).

View the logs and Upscaled cells of interest; check

for inconsistencies. Review Upscaling if necessary.

If setting up a well Section; select raw logs from

Global well logs and upscaled properties from

Properties folder. Add a new track if desired.



More Upscaling in Petrel

Property Modeling course (3 days)

Data analysis and basics of geostatistics

Data preparation, including well

correlation

Facies Modeling; sequential indicator

simulation, facies transition simulation,

object facies modeling (adaptive channel),

interactive facies modeling

Petrophysical modeling; data analysis,

porosity modeling, permeability modeling Modeling based on seismic attributes



EXERCISE

Scale Up Well LogsQC Upscaled Properties



Upscaling of Well LogsAveraging Methods for Continuous Logs

Arithmetic mean - Typically used for properties such as porosity, saturation and

net/gross because these are additive variables.

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

used for permeability because it is sensitive to lower values.

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

RMS (Root Mean Squared) - Will provide a strong bias towards high values.

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

Mid Point Pick ² Will pick the log value where the well is halfway through the

cell. Essentially a random choice and is therefore more likely to give a property with the

same distribution of values as the original well log data.

Random Pick ² Picks a log point at random from anywhere within the cell. This random option avoids

the smoothing tendency of other methods and is therefore more likely to give a property with the same

distribution of values as the original well log data.

Generally:

RMS > Arithmetic

Arithmetic > Geometric

Geometric > Harmonic



Upscaling of Well LogsQC of Upscaled Logs

Create Synthetic logs; these will resemble the

properties (Upscaled logs) but are stored as

physical logs under Global Well Logs

1. Go to the Make logs tab of settings for Wells.

2. Select the property to make log from.

3. Press Make logs button; the log is stored in

the Global Well Logs folder and can be toggled

on from there.

day 4 m14 log upscaling 2008

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