Enhancing exploration results and reducing the risk in reservoir development
WesternGeco is the industry leader in multicomponent seismic technology and has completed many major 2D and 3D surveys worldwide. Multicomponent seismic has been demonstrated to be an effective technology for risk reduction in exploration and development. In an exploration setting multicomponent measurements offer improved imaging, direct hydrocarbon and lithology indication and multiple attenuation over conventional P-Wave seismic. In a development setting multicomponent measurements facilitate improved reservoir illumination and characterization.
Conventional surface seismic surveys record only compressional, or P-waves. Multicomponent seismic surveys record both P-waves and shear, or S-waves, this is achieved by recording all components of the returning wavefield. Each sensor within a multicomponent recording cable comprises three orthogonally oriented geophones for land acquisition, plus a hydrophone for marine acquisition (hence four-component or 4C). P-waves are detected primarily by the Z-component geophone and the hydrophone, while S-waves are detected primarily by the X- and Y-component geophones.
Marine multicomponent acquisition operations typically consist of two or three vessels, one acting as a source vessel and the others as a cable deployment and recording vessels. A seabed recording cable is required because S-waves cannot travel through water. The source vessel generates P-waves; however, at every interface, S-waves are reflected as well as P-waves. These are often referred to as mode-converted S-waves, or PS-waves.
Land multicomponent acquisition can utilize either conventional P-wave sources (dynamite or vibroseis) or S-wave sources, depending on the specific survey requirements.
WesternGeco land and offshore multicomponent seismic acquisition crews use state-of-the-art equipment and are available throughout the world. Our 4C ocean-bottom cable (OBC) crews are the most experienced in the industry and utilize the most advanced seafloor sensor technology available.
With the tools and experience to handle difficult multicomponent seismic processing challenges, our staff has processed many multicomponent surveys from around the world and can access a knowledge base to help deal with all types of acquisition and processing situations.
The Omega Seismic Processing System contains the most comprehensive and sophisticated multicomponent processing algorithms available, they include:
- PZ summation options
- CCP scanning capabilities
- Vp/Vs and S-wave splitting analysis tools
- Prestack time and depth migration
- Tomography ic inversion algorithms
- Anisotropic parameterization and imaging
WesternGeco also offers borehole-calibrated multicomponent processing services to extract the most from all your available subsurface information.
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Multicomponent seismic technology can be applied to many seismic and geological challenges, including:
Strong P-wave multiples
The combination of the signals recorded by the hydrophone and the Z-component geophone can help to reduce water-borne multiple contamination.
Fracture density and orientation
As a result of S-wave anisotropy S-waves usually split into two waves, a fast and a slow mode, these split S-waves are very sensitive to fractures and can provide information about fracture density (fracture porosity) and orientation (directions of preferred permeability).
P-wave reflections may be disturbed by gas trapped in the subsurface. S-waves can be used to help clarify the subsurface image because they are unaffected by pore fluids, an important attribute that can improve seismic imaging and highlight information valuable for reservoir characterization, reservoir monitoring, and well planning.
Direct hydrocarbon and lithology indication
S-waves can provide valuable insights into the nature of subsurface lithologies and pore-saturating fluids, highlighting reservoirs not previously visible using only P-waves.
Investigations into quantitative saturation and pressure changes
S-waves can help monitor time-lapse variations. During production or injection, reservoir fluid saturation and pressure can change dramatically.
Identifying drilling hazards
Methods such as pore-pressure prediction can highlight the presence of shallow gas. Improved illumination Subsurface imagine is often improved through wide azimuth illumination, multicomponent technology offers a cost effective means of acquiring such data in an offshore environment.