Advances in Sub-Basalt P-Wave Imaging with Long Offset Streamer Data

Seismic energy that has been mode converted from pwave to s-wave in the sub-surface may be recorded by multi-component surveys to obtain information about the elastic properties of the earth. Since the energy converted to s-wave is missing from the p-wave an alternative to recording OBC multi-component data is to examine p-wave data for the missing energy. Since pwave velocities are generally faster than s-wave velocities, then for a given reflection point the converted s-wave signal reaches the surface at a shorter offset than the equivalent p-wave information. Thus, it is necessary to record longer offsets for p-wave data than for multicomponent data in order to measure the same information.A non-linear, wide-angle (including post critical) AVO inversion has been developed that allows relative changes in p-wave velocities, s-wave velocities and density to be extracted from long offset p-wave data. To extract amplitudes at long offsets for this inversion it is necessary to image the data correctly, including correcting for higher order moveout and possibly anisotropy if it is present.The higher order moveout may itself be inverted to yield additional information about the anisotropy of the sub-surface.

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Multi‐mode pre‐processing of long‐offset marine streamer data ‐ Faeroes‐Shetland Basin

10.1190/1.1845208 ◽

2004 ◽

Author(s):

Alexander Druzhinin ◽

Xiang‐Yang Li

Keyword(s):

Long Offset ◽

Streamer Data ◽

Multi Mode

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Separating quasi-P-wave in transversely isotropic media with a vertical symmetry axis by synthesized pressure applied to ocean-bottom seismic data elastic reverse time migration

Geophysics ◽

10.1190/geo2016-0108.1 ◽

2016 ◽

Vol 81 (6) ◽

pp. C295-C307 ◽

Cited By ~ 3

Author(s):

Pengfei Yu ◽

Jianhua Geng ◽

Chenlong Wang

Keyword(s):

Transversely Isotropic ◽

P Wave ◽

Ocean Bottom ◽

Receiver Side ◽

Reverse Time ◽

Reverse Time Migration ◽

Time Migration ◽

Isotropic Media ◽

Wave Imaging ◽

Obs Data

Quasi-P (qP)-wavefield separation is a crucial step for elastic P-wave imaging in anisotropic media. It is, however, notoriously challenging to quickly and accurately obtain separated qP-wavefields. Based on the concepts of the trace of the stress tensor and the pressure fields defined in isotropic media, we have developed a new method to rapidly separate the qP-wave in a transversely isotropic medium with a vertical symmetry axis (VTI) by synthesized pressure from ocean-bottom seismic (OBS) data as a preprocessing step for elastic reverse time migration (ERTM). Another key aspect of OBS data elastic wave imaging is receiver-side 4C records back extrapolation. Recent studies have revealed that receiver-side tensorial extrapolation in isotropic media with ocean-bottom 4C records can sufficiently suppress nonphysical waves produced during receiver-side reverse time wavefield extrapolation. Similarly, the receiver-side 4C records tensorial extrapolation was extended to ERTM in VTI media in our studies. Combining a separated qP-wave by synthesizing pressure and receiver-side wavefield reverse time tensorial extrapolation with the crosscorrelation imaging condition, we have developed a robust, fast, flexible, and elastic imaging quality improved method in VTI media for OBS data.

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MULTI-COMPONENT SEISMIC—THE TOOL FOR ALL REASONS

The APPEA Journal ◽

10.1071/aj01034 ◽

2002 ◽

Vol 42 (1) ◽

pp. 587

Author(s):

F.L. Engelmark

Keyword(s):

Fractured Reservoirs ◽

Time Lapse ◽

P Wave ◽

Converted Wave ◽

S Waves ◽

The North ◽

Impedance Contrast ◽

Seismic Sensors ◽

Wave Imaging ◽

Wave Modes

Marine multi-component seismic, known as 4C, is an emerging seismic technology providing improved and sometimes unique solutions to many common problems. In the marine environment the seismic sensors have to be placed on the sea-floor to capture converted or shear wave modes that cannot propagate through liquid media. Although this means increased acquisition cost, the improved information content makes it money well spent to better image and characterise reservoirs.The 4C solutions fall into two major groups of five. First there are the imaging solutions:Improved standard P-wave imaging. Improved converted wave (P-S) resolution in the shallow sediments. Converted wave imaging through gas clouds. Converted wave imaging of low impedance contrast reservoirs. Improved sub-salt and sub-basalt imaging with converted waves. The second group consists of the five characterisation solutions:Improved fracture characterisation by means of P-S waves. Qualitative 4D or time-lapse characterisation of fractured reservoirs with low intrinsic permeability. Improved lithology and fluid characterisation by combining the information in the two wave modes. Improved quantitative time-lapse evaluation of pressure and saturation changes. Improved characterisation of drilling hazards by combined evaluation of the two wave modes. So far the most popular 4C solutions are imaging through gas and improved P-wave imaging of Jurassic reservoirs in the North Sea, for example the Statfjord, Brent and Beryl fields. However, as the technology is developing and maturing, the characterisation solutions will probably be the most common applications of 4C in the near future.

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Directional P-wave Remote Acoustic Imaging in an Acoustically Slow Formation

The Open Petroleum Engineering Journal ◽

10.2174/1874834101508010333 ◽

2015 ◽

Vol 8 (1) ◽

pp. 333-343

Author(s):

Zhoutuo Wei ◽

Hua Wang ◽

Xiaoming Tang ◽

Chunxi Zhuan

Keyword(s):

Acoustic Imaging ◽

P Wave ◽

Reception Theory ◽

Dipole Source ◽

S Wave ◽

Wave Imaging ◽

Field Radiation ◽

Fundamental Radiation ◽

Similarities And Differences

Directional P-wave remote acoustic imaging in an acoustically slow formation is discussed to improve dipole remote acoustic applications. In this paper, we start from the fundamental radiation, reflection and reception theory of a borehole dipole source. We then simulate the elastic wavefield radiation, reflection and reception generated by a borehole dipole source in an acoustically slow formation, and analyze their similarities and differences of the far-field radiation directionality of a borehole dipole-generated P-wave and monopole-generated P-wave. We demonstrate its sensitivity and feasibility in conjunction with a numerical simulation of P-wave remote acoustic imaging. The analytical results show that the dipole-generated P-wave has obvious reflection sensitivity and it can be utilized for reflection imaging and determination of the reflector azimuth. Based on the theoretical analysis above, a field example is used to demonstrate these characteristics and the application effectiveness of dipole-generated P-wave imaging and monopole-generated P-wave imaging. The results substantiate that dipole-generated P-wave has highly reflected amplitude and obvious azimuth sensitivity in an acoustically slow formation, providing an important supplement for dipole-generated S-wave remote acoustic imaging.

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