Changes

  | part    = Predicting the occurrence of oil and gas traps

  | part    = Predicting the occurrence of oil and gas traps

  | chapter = Interpreting seismic data

  | chapter = Interpreting seismic data

  | frompg  = 12-1

  | frompg  = 12-21

  | topg    = 12-29

  | topg    = 12-24

  | author  = Christopher L. Liner

  | author  = Christopher L. Liner

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch12/ch12.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch12/ch12.htm

Follow the steps listed below to make a classic structural [[seismic interpretation]].

Follow the steps listed below to make a classic structural [[seismic interpretation]].

# Preview data for quality and consistency with acquisition and processing reports.

# Make structure [[contour]] maps for key horizons using well control only.

# Identify online wells with velocity control.

# Compute a synthetic seismogram for each online well with a sonic or [[density log]].

# Associate reflectors at each online well with stratigraphic horizons using [[Checkshots_and_vertical_seismic_profiles#Vertical_seismic_profiles|vertical seismic profile (VSP)]], synthetic seismogram, or time-stretched logs.

# Interpret seismic data using color identifiers (tracking) by extending reflection events across the entire survey area.

| Preview data for quality and consistency with acquisition and processing reports.

# Mark faults and key structural details.

| Make structure contour maps for key horizons using well control only.

| Identify online wells with velocity control.

| Compute a synthetic seismogram for each online well with a sonic or density log.

| Associate reflectors at each online well with stratigraphic horizons using VSP, synthetic seismogram, or time-stretched logs.

| Interpret seismic data using color identifiers (tracking) by extending reflection events across the entire survey area.

| Mark faults and key structural details.

==Step 1: Preview data==

==Step 1: Preview data==

[[file:interpreting-seismic-data_fig12-9.png|thumb|{{figure number|1}}. Copyright: Liner; courtesy PennWell.]]

[[file:interpreting-seismic-data_fig12-9.png|300px|thumb|{{figure number|1}}Each 3-D seismic survey has a unique outline of live traces or image area. Use the outline of the image area with the processing report and well spots to confirm correct orientation of the survey. Copyright: Liner;<ref name=Liner>Liner, Chris, Elements of 3-D Seismology: Tulsa, PennWell, 1999.</ref> courtesy PennWell.]]

Preview seismic data for quality and consistency using acquisition and processing reports that come with the data. Note any geological conditions that might cause the interpretation method listed in the procedure to fail. As shown in Figure 12-9A, each 3-D seismic survey has a unique outline of live traces or image area. Use the outline of the image area with the processing report and well spots ([[:file:interpreting-seismic-data_fig12-9.png|Figure 1B]]) to confirm correct orientation of the survey. This might sound silly but it is very easy to get the orientation wrong since there are many ways to orient a cube.

Preview seismic data for quality and consistency using acquisition and processing reports that come with the data. Note any geological conditions that might cause the interpretation method listed in the procedure to fail. As shown in [[:file:interpreting-seismic-data_fig12-9.png|Figure 1A]], each 3-D seismic survey has a unique outline of live traces or image area. Use the outline of the image area with the processing report and well spots ([[:file:interpreting-seismic-data_fig12-9.png|Figure 1B]]) to confirm correct orientation of the survey. This might sound silly but it is very easy to get the orientation wrong since there are many ways to orient a cube.

==Step 2: Create well control maps==

==Step 2: Create well control maps==

A depth structure map should be constructed using all available well control to the horizon of interest. There are many ways of gridding or contouring depth points. Whatever the method, it should also be used in the depth conversion velocity map (next section). The wells-only depth structure map is a useful baseline.

A depth structure map should be constructed using all available well control to the horizon of interest. There are many ways of gridding or [[contour]]ing depth points. Whatever the method, it should also be used in the depth conversion velocity map (next section). The wells-only depth structure map is a useful baseline.

==Step 3: Identify wells with velocity control==

==Step 3: Identify wells with velocity control==

==Step 6: Track events==

==Step 6: Track events==

Interpret seismic data using color identifiers by extending reflection events across the entire survey area. This process is called tracking—following an event throughout the data volume.

Interpret seismic data using color identifiers by extending reflection events across the entire survey area. This process is called tracking—following an event throughout the data volume.

===Step 7: Mark faults===

===Step 7: Mark faults===

Mark faults and other structural details on the seismic sections. If necessary, jump-correlate picked events across faults. When a conflict exists, a well-tie correlation is preferred to seismic jump correlation across faults. The seismic section in [[:file:interpreting-seismic-data_fig12-10.png|Figure 2]] shows a jump correlation. A small panel of data, labeled A, is outlined on the right side of the fault. Two key horizons are marked. The data panel was copied, then moved across the fault and adjusted until a satisfactory fit was made at B. Note the apparently continuous event connecting the yellow dot at A with the blue dot at B. This is a false correlation.

Mark faults and other structural details on the seismic sections. If necessary, jump-correlate picked events across faults. When a conflict exists, a well-tie correlation is preferred to seismic jump correlation across faults. The seismic section in [[:file:interpreting-seismic-data_fig12-10.png|Figure 2]] shows a jump correlation. A small panel of data, labeled A, is outlined on the right side of the fault. Two key horizons are marked. The data panel was copied, then moved across the fault and adjusted until a satisfactory fit was made at B. Note the apparently continuous event connecting the yellow dot at A with the blue dot at B. This is a false correlation.

===Marking up key sections===

===Marking up key sections===

[[file:interpreting-seismic-data_fig12-11.png|thumb|{{figure number|3}}. Copyright: Liner, 1999; courtesy PennWell.]]

Beyond jump correlation, an important part of structural interpretation is to mark up a few key lines in detail. [[:file:interpreting-seismic-data_fig12-11.png|Figure 3]] shows part of such a marked-up section. Faults are marked in green, with line width denoting relative importance. Sense of throw is indicated as up (U) or down (D). Yellow dots indicate events used to calculate depth and fault throw, while yellow lines are events used for [[dip]] calculations. Fault numbers indicate relative age (1 = most recently active, etc.). Red arrows show stratigraphic bed terminations. The arrowhead indicates whether termination is from above or below. For depth, throw, and dip estimates, a simple linear velocity model was used: ''υ''(''z'') = 5,000 + 0.4*''z'', where ''υ'' is in ft/sec and ''z'' is depth in feet. This velocity model is often useful in basins that contain unconsolidated sediments, such as the [[Gulf of Mexico]]. The data for [[:file:interpreting-seismic-data_fig12-10.png|Figures 2]] and [[:file:interpreting-seismic-data_fig12-11.png|3]] come from Southeast Asia.

Beyond jump correlation, an important part of structural interpretation is to mark up a few key lines in detail. Figure 12-11 shows part of such a marked-up section. Faults are marked in green, with line width denoting relative importance. Sense of throw is indicated as up (U) or down (D). Yellow dots indicate events used to calculate depth and fault throw, while yellow lines are events used for dip calculations. Fault numbers indicate relative age (1 = most recently active, etc.). Red arrows show stratigraphic bed terminations. The arrowhead indicates whether termination is from above or below. For depth, throw, and dip estimates, a simple linear velocity model was used: ''υ''(''z'') = 5,000 + 0.4*''z'', where ''υ'' is in ft/sec and ''z'' is depth in feet. This velocity model is often useful in basins that contain unconsolidated sediments, such as the Gulf of Mexico. The data for [[:file:interpreting-seismic-data_fig12-10.png|Figures 2]] and [[:file:interpreting-seismic-data_fig12-11.png|3]] come from Southeast Asia.

==See also==

* [[Seismic data and mapping structure]]

* [[Seismic data - creating an integrated structure map]]

==See also==

==References==

==External links==

==External links==

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Interpreting seismic data]]

[[Category:Interpreting seismic data]]