Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253...
-
Upload
julia-randall -
Category
Documents
-
view
214 -
download
0
Transcript of Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253...
![Page 1: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/1.jpg)
Geology 5660/6660Applied Geophysics
19 Feb 2014
© A.R. Lowry 2014For Fri 21 Feb: Burger 200-253 (§4.4-4.7)
Last Time: Reflection Data Processing• Step IV: Migration return reflection energy to its “true” location on the two-way travel-time image… Depth migration uses velocity structure from NMO correction to convert travel time to depth (improving image resolution; removing e.g. velocity pull-ups/pull-downs)• Sometimes additional steps as well: Amplitude adjustments Frequency adjustments Transmission adjustments Depth Migration (The latter especially is important for velocity effects!)
Seismic Reflection Interpretation• Data collection: Huge quantities of data! Redundancy is key!• 2D profiling still used for initial reconnaissance, but 3D is industry standard for prospects
![Page 2: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/2.jpg)
Haakon Fossen 2010
2D Seismic Data• 2D lines are long profiles that are processed independently
• Generally collected now for regional reconnaissance studies
• Covers large areas and gives an overall picture of the geology
![Page 3: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/3.jpg)
Haakon Fossen 2010
![Page 4: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/4.jpg)
Haakon Fossen 2010
![Page 5: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/5.jpg)
Haakon Fossen 2010
Deep seismic profiling• Imaging depth range from 0-50 km
Strongest & most continuous impedance contrasts below sedimentary cover are lithologic changes ~mid-crust and at the Moho
![Page 6: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/6.jpg)
Haakon Fossen 2010
Other reflectivity within crystalline crust can relate to lithologic changes (e.g. across a low-angle normal fault) but also often represents mineral alignment in ductile shear zones
![Page 7: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/7.jpg)
Haakon Fossen 2010
![Page 8: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/8.jpg)
Haakon Fossen 2010
• Better resolution
• Better positioning
• 3D view options
3-D seismic cubes
![Page 9: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/9.jpg)
Haakon Fossen 2010
3D seismic3D data: • collected by shooting many parallel lines ~25 m apart• migrated together to increase accuracy and to create a coherent data volume (cube) • collected over all offshore oil and gas fields• underpin the geometric understanding of an oil field
![Page 10: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/10.jpg)
Haakon Fossen 2010
![Page 11: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/11.jpg)
Haakon Fossen 2010
Data acquisition
![Page 12: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/12.jpg)
Haakon Fossen 2010
Resolution
• Vertical
• Lateral
![Page 13: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/13.jpg)
Haakon Fossen 2010
Vertical resolution
Relationship between bedthickness and acousticimpedance contrast forseismic resolution of alayer.
Vertical seismic resolution in terms oftuning thickness: When top to baseof a layer is less than 1/4 wavelength,constructive/destructive interferenceresults in apparent single wavelet.
![Page 14: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/14.jpg)
Haakon Fossen 2010
Color convention: Blue for positive amplitude, red for negative…
![Page 15: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/15.jpg)
Haakon Fossen 2010
![Page 16: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/16.jpg)
Haakon Fossen 2010
![Page 17: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/17.jpg)
Haakon Fossen 2010
![Page 18: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/18.jpg)
Haakon Fossen 2010
Lateral positioning
• Choice of migration velocities affects horizontal positioning of signals• Horizontal resolution typically 50-100 m• Serious concern when drilling high-precision wells, e.g. close to faults. • Resolution may depend heavily on pilot wells
![Page 19: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/19.jpg)
Haakon Fossen 2010
Directional drilling/steering technology is another reason for accurate depth migration!
![Page 20: Geology 5660/6660 Applied Geophysics 19 Feb 2014 © A.R. Lowry 2014 For Fri 21 Feb: Burger 200-253 (§4.4-4.7) Last Time: Reflection Data Processing Step.](https://reader036.fdocuments.in/reader036/viewer/2022062804/56649f125503460f94c25899/html5/thumbnails/20.jpg)
Haakon Fossen 2010
Seismic qualityDepends on:
• Acoustic impedance contrast
• Depth ( frequency)
• Layer thickness ( interference)
• Properties of overlying layers
• Source energy
• Processing parameters
• Acquisition direction
• Instrumentation