vsp

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Vertical Seismic Profiling(definition)

• Vertical seismic profiling (VSP) is a form of seismic reflectionSurveying that utilizes borehole.

Vertical Seismic Profiling(Sorts)

• Description of an zero offset VSP.

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• Description of an offset VSP.


• Description of an walk away VSP.

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• Description of an reverse VSP.

Vertical Seismic Profiling(zero offset VSP)

• If the surface shot location lies at the wellhead vertically above the borehole detector locations, so that the recorded rays have travelled along vertical ray paths, the method is known as zero –offset VSP.

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Vertical Seismic Profiling( Offset VSP)

• If the surface shot locations are offset laterally, so that the recorded rays have travelled along inclined ray paths, the method is known offset VSP.

Vertical Seismic Profiling(Feature of VSP)

• Removal of multiple reflection.

• Shortening the overall path length of reflected rays.

• Reducing the effects of attenuation.

• Reducing the dimensions of the Fresnel zone.

VSP data leads to much improved reliability in geological interpretation of seismic sections recorded at the surface in the vicinity of the borehole.

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Vertical Seismic Profiling(Feature of VSP)

Each trace being recored at different depth.

Separation downgoing and upgoing events

by f-k filtering.

Time correction to each trace.

Stacked seismogram produced by stacking in shaded corridor zone.

Vertical Seismic Profiling(The nature of VSP data)

A synthetic zero-offset

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(a) Synthetic VSP section (downgoing waves removed by f-k filterling)

(b) Each trace has been time shifted by the relevant uphole time to simulate a surface recording.

(c) Stacked seismogram produced by stacking in the shaded corridor zone of (b) to avoid multiple events

corridor zone

(a) (b) (c)


Comparison of the VSP stack with the surface recorded data enables the primary events in the seismic section to be reliably distinguished from multiple events.

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Application of seismic refletion surveying

• Reflection surveying was concerned almost exclusively with the search for hydrocarbon and coal, oil etc.

• Reflection profiling at crustal and lithospheric scale si now being carried out by many countries.

• The use of reflection seismics for high-resolution studies of shallow geology is a field of growing importance in which developments are linked directly to recent technical advances.

Application of seismic refletion surveying(Example 1)

• Interpreted seismic section across the Noth Viking gas field, North Sea.

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(a) Seismic section (courtesy Shell UK Ltd.)

(b) Line interpretation across the Brent oilfield, North Sea.

G: gas, O: oil, W: water.

(a)

(b)


A non-migrated crustal reflection section from the 1986/87 GRID survey of BIPS programme, collected along a west-east line about 30km north of Scotland, UK, and a migrated line drawingof the main reflection events. The main structure are interpreted to be of Caledonian age with later re-activation.

(FL: Flannan reflection; OIF:Outer Isles fault; MT: Moine thrust; NT: Naver thrust; M: Moho)

vsp

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