Multi 2D-Line InversionUsing STRATA

Irfan Saputra, Simon VoiseyHRSNovember, 2008, CE8R2.1

This document illustrates the multi-2d lines inversion in CE8R2.1. Some essential points before started :

• It is better to load the lines in two ways: group volume[1] and merge

volume[2].[ ]

• To avoid a long horizon list, we should import horizons into a merge volume

rather than a group volume.

• Each horizon have all line entries in a single file (and this could be based on

X,Y coordinates or CDP number).

• If we load an horizon based on CDP, we have to renumber both of seismic and

horizon to unique CDP number (see: data conditioning for CDP)

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Data Conditioning For CDP

1. Merge the horizon from all lines into one file.

2 Column 1 represents the line2. Column 1 represents the line number.

3. Column 2 is the modified CDP. We create a unique CDP

Original Edited

qnumber using the formula:[line number] * 10000 + CDP

4. Column 3 is the amplitude picks which remain unchanged.

3

Data Conditioning (SEG-Y header)

• Modify the value of byte 25 using a SEG-Y editor (such as Seisloader) and(such as Seisloader) and using the same formula when we modified the horizon.• This process should be conducted for all lines.

Seismic Data Loading [Group]

• Seismic data files are selected by navigating to the location on disk and adding them from the left column toadding them from the left column to the right column of the window.

• The files for each 2D may be in different directories although it isdifferent directories although it is easiest if they are all together.

• The SEG-Y files will need X and Y co-ordinates present in the traceco ordinates present in the trace header.

• The seismic data loaded in two steps:

[1] G l[1] Group volume

[2] Merge volume

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Seismic Data Loading [Group]

1 1. We chose the option to load seismic data as 2D Line as we

t t di l th li2

want to display the lines individually.

2. We select Grouped Volume and give an appropriate volumeand give an appropriate volume name.

3. For 2D lines, the geometry will be assigned by x and ybe assigned by x and y coordinates

4. We will use the original CDP number so we don’t need to3 number so we don t need to renumber.

3

4

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Seismic Data Loading [Group]

5. Insert the byte location. Use “Header Dump” to find this

7 information.

6. Ignore receiver x and y coordinates because we deal

ith t t k d t

7

with post-stack data.

7. If we have files with different formats, we can specify for

h fil t l O if th

56

each file separately. Or if they are all the same, we can “Apply Format to all files”

8 Use this slider to make sure the

8

8. Use this slider to make sure the header values are sensible for each line.

7

Note: the CDP byte location should point to the unique CDP location.

Seismic Data Loading [Group]

9

10

• After the seismic scanning process is finished, the geometry page will show up. Press OK to bring it into the active projectbring it into the active project

• The program will create the volume group [9] and individual volumes [10]

8

volumes [10].

Seismic Data Loading [Merge]

• After finishing the group volume then we go back to import data again for the merged option [1]merged option [1].

• Keep all parameters the same as the previous method, except we activate

1p , pthe option to Display in new seismic window [2].

9

2

Seismic Data Loading

Grouped Volume

10Merged Volume

Horizon Importing

• The horizon should be imported into the merge volume [1].1

• To import by CDP number matching [2], we must initially edit the horizon and SEG-Y header to create a unique number. If using the X,Y coordinate [3], we don’t have to perform that editing

2perform that editing.

• The horizon that has been imported into the merged volume

3

imported into the merged volume can also be used in the group volume.

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Horizon picking

• It is better to pick the horizon in each individual line.

• After all lines has been picked, export them in an ASCII file and merge all to a single file conditioning assingle file, conditioning as needed (See data conditioning).

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Wavelet Extraction

• Wavelet extraction can be conducted from the grouped [1] or the merged volume[2][1] or the merged volume[2].

1Statistical Well

2Statistical Well

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Well Correlation

• We can extract composite traces from a group volume. STRATA will choose the closestSTRATA will choose the closest line based on the capture radius or distance specific (in this example is line 14770).

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Build Model

• The model building flow is identical to the 3d inversion process

• An initial model is created from the wells• An initial model is created from the wells and distributed to all lines. The horizons are used as guidance for this interpolation.

Note : an error message will appear telling

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Note : an error message will appear telling us about a geometry difference. Select the option to continue.

Inversion Analysis

• Select the group volume. The program will do the analysis for the line that intersects the well. This example is done in the CE8R2.1 version of our software If using the CE8R3 version we recommend using the merge volumesoftware. If using the CE8R3 version, we recommend using the merge volume instead (see page 20).

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Inversion

1. All 2D lines may be inverted at the same time using the same model.

2 To use horizons as boundaries of a2. To use horizons as boundaries of a target zone to be inverted, select the horizon from the list.

Since we imported the horizon into the merge volume, then the top sand horizon from all lines is represented by only one list.

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Inversion

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Working on Multi Vintage data

• In some case our seismic data comes from different vintages which could have different phaseLine2_00 Li

ne3_

00

Line

4_00

which could have different phase, frequency content, datums, etc.

• This difference can make lines Vi t 1

Line1_00

Line1_01

01

mistie.

• We can still perform inversion by

Vintage 1Vintage 2Vintage 3Wells

Line

2_0 Line1_02

grouping the lines which have the same vintage and creating multiple models, wavelets and horizons.

MistieMistie

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Create Volume Group

• First step to do is to create a volume group.

1• The volume group is

created by loading the lines which have the

1

same vintage into one group.

• Later, if we need to modify or create a new volume group [1], we can do it in Data Explorer by2 do it in Data Explorer by simply dragging and dropping the volume into the group folder, then

2

change Multi2D option to “yes” [2].

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Create Volume Group

• If we have a vintage with no well associated on it then we can group it with another vintageLine2 00 Li

ne3_

00

Line

4_00

can group it with another vintage [1] which has a well.

• But sometimes we need to

Line1_00

Line2_00

Line1_01

conditioning the lines first (balancing with reference line), using resampling, time and phase shifting

Vintage 1Vintage 2Vintage 3Wells

Line

2_01 Line1_02

phase shifting.

1

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Create Model, Wavelet & Horizon

• The next step is to create a model, extract a wavelet and pick horizons for each

Wavelet

pick horizons for each vintage. Then invert the lines using the appropriate model, wavelet and h i

Initial Model Inverted Volume

horizons.

Volume Group 1

Volume Group 2Volume Group 2

Wavelet

Initial Model Inverted Volume

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