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| | 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 = 12-6 |
− | | topg = 12-29 | + | | topg = 12-7 |
| | 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 |
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| | isbn = 0-89181-602-X | | | isbn = 0-89181-602-X |
| }} | | }} |
− | From the broad field of seismology, a few things seem to pop up with regularity. Some of these have been collected here. Keep them in mind when working with seismic data—in particular, 3-D seismic data. | + | From the broad field of seismology, a few things seem to pop up with regularity. Some of these have been collected here. Keep them in mind when working with [[seismic data]]—in particular, 3-D seismic data. |
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| ==The onion== | | ==The onion== |
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− | [[file:interpreting-seismic-data_fig12-1.png|thumb|{{figure number|1}}. Copyright: Liner, 1999; courtesy PennWell.]] | + | [[file:interpreting-seismic-data_fig12-1.png|thumb|300px|{{figure number|1}}Seismic data is built of several layers like an onion. Copyright: Liner;<ref name=Liner>Liner, C., 1999, Elements of 3-D Seismology: Tulsa, PennWell.</ref> courtesy PennWell.]] |
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| The knowledge required for working with seismic data is built of several layers like an onion. [[:file:interpreting-seismic-data_fig12-1.png|Figure 1]] illustrates the idea. At the heart of the onion are 1-D seismic concepts like [[wavelet]], [[convolution]], [[traveltime]], and [[reflection coefficient]]. All this shows up in the next layer, 2-D seismic, plus [[Seismic array|arrays]], [[offset]], [[dip]], and [[lateral velocity]] variation. The next layer, 3-D seismic, includes all of 2-D plus [[azimuth]], [[Components of a 3-D seismic survey#Bins|bins]], and the [[3-D seismic: the data cube|data volume]]. Finally, 4-D seismic is time-lapse 3-D, which introduces [[repeatability]], [[Fundamentals of fluid flow|fluid flow]], and [[difference volume]]. | | The knowledge required for working with seismic data is built of several layers like an onion. [[:file:interpreting-seismic-data_fig12-1.png|Figure 1]] illustrates the idea. At the heart of the onion are 1-D seismic concepts like [[wavelet]], [[convolution]], [[traveltime]], and [[reflection coefficient]]. All this shows up in the next layer, 2-D seismic, plus [[Seismic array|arrays]], [[offset]], [[dip]], and [[lateral velocity]] variation. The next layer, 3-D seismic, includes all of 2-D plus [[azimuth]], [[Components of a 3-D seismic survey#Bins|bins]], and the [[3-D seismic: the data cube|data volume]]. Finally, 4-D seismic is time-lapse 3-D, which introduces [[repeatability]], [[Fundamentals of fluid flow|fluid flow]], and [[difference volume]]. |
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| ==Edges== | | ==Edges== |
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− | [[file:interpreting-seismic-data_fig12-2.png|thumb|{{figure number|2}}. Copyright: Liner, 1999; courtesy PennWell.]] | + | [[file:interpreting-seismic-data_fig12-2.png|300px|thumb|{{figure number|2}}. Copyright: Liner;<ref name=Liner /> courtesy PennWell.]] |
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− | If you look at a rock outcrop, you see [[sandstone]], [[shale]], [[limestone]], etc. If you look at seismic data, you see the edges of rock units. The figure below shows the edge effect on a Gulf of Mexico [[salt dome]] example. Seismic analysis is, in effect, an edge detection technique. The bigger the [[velocity]] and/or [[density]] contrast between the rocks, the stronger the edge. | + | If you look at a [http://www.merriam-webster.com/dictionary/outcrop rock outcrop], you see [[sandstone]], [[shale]], [[limestone]], etc. If you look at seismic data, you see the edges of rock units. The figure below shows the edge effect on a [[Gulf of Mexico]] [[salt dome]] example. Seismic analysis is, in effect, an edge detection technique. The bigger the [[velocity]] and/or [[density]] contrast between the rocks, the stronger the edge. |
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| To be fair, seismic impulses respond to much more than just lithology. Any vertical variation in rock property that modifies the velocity or density can potentially generate [[seismic reflection]]s, including a [[Fluid contacts|fluid contact]], [[porosity]] variation, or shale density change. | | To be fair, seismic impulses respond to much more than just lithology. Any vertical variation in rock property that modifies the velocity or density can potentially generate [[seismic reflection]]s, including a [[Fluid contacts|fluid contact]], [[porosity]] variation, or shale density change. |
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| ==Event tracking== | | ==Event tracking== |
− | A key part of the interpretation process for 3-D seismic data is event tracking. To picture this, think of the 3-D seismic data volume as a block of vanilla ice cream with chocolate streaks. Tracking means we follow a streak into the cube and find out where it goes—this is structure mapping. We also keep track of how dark the chocolate is as we follow it—this is amplitude mapping. | + | A key part of the interpretation process for 3-D [[seismic data]] is event tracking. To picture this, think of the [[3-D seismic: the data cube|3-D seismic data volume]] as a block of vanilla ice cream with chocolate streaks. Tracking means we follow a streak into the cube and find out where it goes—this is [[Seismic structure map|structure mapping]]. We also keep track of how dark the chocolate is as we follow it—this is [[amplitude map]]ping. |
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| ==Computer limitations== | | ==Computer limitations== |
− | Available computer speed and memory impose severe limitations on the use of advanced 3-D seismic processing. Current hardware is sufficient for the interpretation process, but the software can be complicated and expensive ([[cost::5,000 USD]]-[[cost::180,000 USD]]). | + | Available computer speed and memory impose severe limitations on the use of advanced 3-D seismic processing. Current hardware is sufficient for the interpretation process, but the software can be complicated and expensive. |
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| ==See also== | | ==See also== |
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| * [[Components of a 3-D seismic survey]] | | * [[Components of a 3-D seismic survey]] |
| * [[3-D seismic data views]] | | * [[3-D seismic data views]] |
| + | |
| + | ==References== |
| + | {{reflist}} |
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| ==External links== | | ==External links== |
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| [[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]] |
| + | [[Category:Geophysical methods]] |
| + | [[Category:Treatise Handbook 3]] |