Sub-basalt seismic imaging is very challenging due to large impedance contrasts at sediment-basalt interfaces. The impedance of basalt usually gives a strong reflection coefficient at the top of basalt, and thus generates strong multiples. Offshore western India, this issue is compounded by short-period seabed multiples generated by the shallow sea …

FIGURE 11-1. The relationships among sound source coordinate s, geophone sound receiver coordinate g, offset coordinate f = g - s, and midpoint coordinate y = (g + s)/2. Theoreticians generally use s and g as coordinates of the wave-pressure field, but interpreters generally use f and y.

Basalts usually have very high seismic velocities compared to surrounding rocks and high density in comparison to most sediments. As a consequence, wave propagation through basalt layers is very complex and conventional reflection seismic surveying is less …

technical article first break volume 20.10 October 2002 Faeroe sub-basalt seismic imaging: a new iterative time processing approach L. Barzaghi, D., Calcagni, M. Passolunghi and S. Sandroni Introduction Converted wave terminology The main problem for seismic imaging in the Faeroe Basin is the presence of a widespread basalt body of variable ...

The top boundary of the basalt sequence is defined by a strong reflection with a steep velocity increase from 3.5 km s −1 to 4.5 km s −1 in the c. 200 m thick layer above it. The basalt sequence here is c. 2.5 km thick. Beneath the base of the basalt there is a velocity decrease from 5.8 km s −1 to 5.2 km s −1.

Data acquisition and processing Stacked basalt flows typically exhibit a low-pass character to seismic waves ... Velocities in the basalt layer are consistent with those seen in the Lopra borehole (Christie et al., 2005). ... and White, R. S. 2001. Seismic structure of basalt flows from surface seismic data, borehole measurements, and synthetic ...

The conventional (short offset) seismic data acquisition, processing and modeling techniques adopted by the oil industry generally fails to image hydrocarbon-bearing sub-trappean Mesozoic sediments hidden below …

To overcome this difficulty of sub-basalt imaging, we have generated dense synthetic seismic data with the help of elastic finite-difference full-wave modeling using staggered-grid scheme for the ...

Request PDF | Sub-basalt seismic imaging using optical-to-acoustic model building and wave equation datuming processing | The presence of highly heterogeneous basalt layers has a detrimental ...

Maximum offset=10 km. Green dashed lines indicate top and base of basalt layer. Fig. 5. Example stack image after several key pre-migration processing stages: (a) after SRME multiple attenuation; ... Example processing flow used to reprocess 2D seismic data in the West of Shetland region. The flow chart indicates the position of the noise ...

High-quality seismic profiles across the Faroes volcanic continental margin and the adjacent continental shelf show contrasting styles of basalt emplacement across two …

Conventional seismic acquisition and processing of a 2D seismic line provide poor results. However, upgoing reflections from layers below the basalt are clearly evident in the VSP survey and prestack depth migration is able to improve the continuity of the reflectors beneath the basalt.

base of basalt layer. SIGNAL PROCESSING FOR SUB-BASALT IMAGING 165 ... Example processing flow used to reprocess 2D seismic data in the West of Shetland region. The flow chart

Imaging below the basalt for hydrocarbon exploration is a global problem because of poor penetration of seismic energy. There is significant loss of energy due to scattering, attenuation, absorption and mode-conversions when the seismic waves encounter a highly heterogeneous and rugose basalt layer.

ABSTRACT. High-quality seismic profiles across the Faroes volcanic continental margin and the adjacent continental shelf show contrasting styles of basalt emplacement across two major structural boundaries. At the rifted continental margin, the basalts form promi-nent seaward dipping reflector sequences up to 5 km thick.

New seismic reflection data have been used to image intra- and sub-basalt features beneath the Faroe–Shetland Basin in the North Atlantic, where the highly reflective top and base boundaries of flood basalts and their complex internal structure make successful seismic imaging difficult. This study demonstrates that appropriate …

The thin layers in the basalt act as a low-pass filter to the seismic wave. For the real-data acquisition, even the topbasalt reflection is a low frequency event.

The presence of highly heterogeneous basalt layers has a detrimental effect on seismic imaging of underlying structures. Due to the prevalence of basalt, the challenge of imaging below basalts impinges on a broad spectrum of geological problems, from hydrocarbon exploration to volcano seismology.Both internal basalt characteristics and …

The seismic data on the left have been acquired beneath a thick, near-surface basalt layer. The high-velocity layer attenuates the seismic energy as it propagates down to the target coal layers, and again on its return to the seismic receivers. ... The successful integration of 3D seismic into the mining process: Practical examples from Bowen ...

Sub-basalt imaging continues to provide a challenge along the northwest European Atlantic Margin. Successful imaging is being achieved on 2D seismic, acquired with conventional source array and ...

We vary basalt layer thickness and source frequency to generate a synthetic model that produces seismic that is similar to real sub-basalt seismic, i.e. high amplitude top basalt reflector and the absence of base basalt and sub-basalt events. ... In this situation, standard seismic processing is often unable to resolve the structure beneath ...

Near-Surface Basalt Models The noise generated in near-surface basalt depends on the attenuation properties of the basalt. Figure 2 shows the synthetic obtained when a near-surface high-velocity basalt layer (VP = 3750 m/s, VS = 2170 m/s, ρ = 2.5 g/cc, thickness = 50 m, depth = 4 m) is added to the reference model.

Sub-basalt PP reflections are often swamped by mode conversions at the basalt-sediment interface (Purnell, 1992; Barzaghi et al., 2002). These are proving to be major problems for seismic imaging ...

Down to top basalt the models are fairly consistent while there are deviations of up to 1 km s-1 in basalt velocities and sub-basalt sediment velocities, 2 km in basalt thickness, 3.2 km in depth ...

This success supports seismic potential for subsurface basalt characterization and a path forward for developing seismic and wireline monitoring …

In this paper we summarize the acquisition and processing o f the multi-component seismic swath, and present observations on the integration of P- and S- waveform sonic logs with information from resistivity-based image logs to determine regional and local stress tensors and to improve identification of subsurface basalt lithofacies. 2. Seismic ...

thickness of the basalt layer may be under or over-estimated when compared to the true thickness, indicating that simple ray-tracing based on the assumption of turning rays is not appropriate when considering long-offset refractions from data over regions affected by extrusive basalt sequences. Keywords: Seismic, modelling, sub-basalt, ray ...

Sub-basalt imaging continues to provide a challenge within the West of Shetland region. Successful imaging is being achieved through the reprocessing of 2D reflection …

processing software while learning seismic data processing procedures and exercises. An advanced learner should try to write computer code for important processing steps to allow an in-depth comprehension of the practical issues and limitations. 1.1 Seismic data and their acquisition, processing, and interpretation

A map of basalt and sub-basalt sedimentary layer thickness beneath the Faroe Islands and surrounding area, compiled from published wideangle seismic data, indicates that basalt thickness is ...