Preliminary results from investigations of seismic and petrophysical properties of Faroes basalts in the SeiFaBa project

Japsen, Peter; Andersen, C.; Andersen, Heidi Lie; Andersen, Morten Sparre; Boldreel, Lars Ole; Mavko, Gary; Mohammed, Nedham; Pedersen, Jens Myrup; Petersen, Uni K.; Rasmussen, R.; Shaw, F.; Springer, Niels; Waagstein, Regin; White, R. S.; Worthington, M. H.

doi:10.1144/0061461

Cited by 16 publications

(20 citation statements)

References 22 publications

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“…This generates a cyclic pattern of properties that produces numerous subhorizontal layers with strong contrasts in physical properties. Such a pattern is typical of lavas extruded on the Atlantic margin ͑Planke, 1994; Christie et al, 2002;Japsen et al, 2005͒. This repeated sequence of strong physical contrasts creates problems with subbasalt seismic imaging.…”

Section: Measured Seismic Attenuation Of Basalts Using Vsp Datamentioning

confidence: 99%

Seismic attenuation of Atlantic margin basalts: Observations and modeling

et al. 2006

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Paleogene basalts are present over much of the northeastern Atlantic European margin. In regions containing significant thicknesses of layered basalt flows, conducting seismic imaging within and beneath the volcanic section has proven difficult, largely because the basalts severely attenuate and scatter seismic energy. We use data from a vertical seismic profile ͑VSP͒ from well 164/07-1 that penetrated 1.2 km of basalt in the northern Rockall Trough west of Britain to measure the seismic attenuation caused by the in-situ basalts. The effective quality factor Q eff of the basalt layer is found from the VSP to be 15-35, which is considerably lower ͑more attenuative͒ than the intrinsic attenuation measured on basalt samples in the laboratory. We then run synthetic seismogram models to investigate the likely cause of the attenuation. Full waveform 1D modeling of stacked sequences of lava flows based on rock properties from the same well indicates that much of the seismic attenuation observed from the VSP can be accounted for by the scattering effects of multiple thin layers with high impedance contrasts. Phase-screen seismic modeling of the rugose basalt surface at the top-of-basalt sediment interface, with the magnitude and wavelength of the relief constrained by a 3D seismic survey around the well, suggests that surface scattering from this interface plays a much smaller role than internal scattering in attenuating the seismic signal as it passes through the basalt sequence.

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Section: Measured Seismic Attenuation Of Basalts Using Vsp Datamentioning

confidence: 99%

Seismic attenuation of Atlantic margin basalts: Observations and modeling

et al. 2006

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“…Its original total depth was 660 m, but in 2002 it was reamed and logged to 590 m as part of the SeiFaBa project (Japsen et al 2005) 3. Principles of interpreting wireline log data.…”

Section: Analysis Of the Lopra-1/1a Vestmanna-1 And Glyvursnes-1 Bomentioning

confidence: 99%

Flood basalt facies from borehole data: implications for prospectivity and volcanology in volcanic rifted margins

Nelson

Jerram

Hobbs

2009

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Flood basalt successions cover many potentially prospective sedimentary basins world-wide, and a few instances exist of intra-basalt petroleum discoveries. However, little is known about the architecture and rock properties of the lava flows, intrusions and other lithologies that make up these successions. We present a simple, effective method of obtaining information from borehole data on the different volcanic facies within a flood basalt succession. Our aims are: (1) to provide a means of determining proportions of different volcanic facies without detailed examination of borehole data or where borehole data are limited; (2) to explore the relationship between onshore and offshore observations. The facies classification scheme providing the framework for this research includes tabularclassic lava flows, compound-braided lava flows, hyaloclastites and intrusions. We show how this scheme can increase our knowledge of the offshore succession and can be useful in hydrocarbon exploration.In the Faroe Islands, three different basalt formations display a range of facies onshore. Boreholes have been drilled through these, and several kilometres' depth of log data collected. The proximity of these boreholes to onshore observations allows the identification of different facies within the wireline log data. This work demonstrates that histograms of P-wave velocities provide an efficient method of identifying the different facies, and we also explore why these distributions are so different. When applied to borehole data from published ODP wells and one commercial well, it is possible to estimate proportions of the different volcanic facies using the velocity distributions alone.

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“…The thin-layer model (Figure 2a, bottom) was created using well-log data based on the fact that the dominant lithology is parallel-bedded basalts (Japsen et al, 2005). Thick sections of each basalt formation have been drilled by three deep onshore wells: the Glyvursnes-1 well intersects both the UBF and MBF; the Vestmanna-1 well intersects the MBF and LBF and the Lopra-1/1A on the island of Suduroy intersects LBF.…”

Section: Model Buildingmentioning

confidence: 99%

“…Thick sections of each basalt formation have been drilled by three deep onshore wells: the Glyvursnes-1 well intersects both the UBF and MBF; the Vestmanna-1 well intersects the MBF and LBF and the Lopra-1/1A on the island of Suduroy intersects LBF. These provide an outstanding source of data for the determination of both the petrophysical and seismic properties of basalts in the Faroe Islands (Japsen, et al, 2005). These provide an outstanding source of data for the determination of both the petrophysical and seismic properties of basalts in the Faroe Islands (Japsen, et al, 2005).…”

Section: Model Buildingmentioning

confidence: 99%

Multiple Attenuation for the GlyVeST Seismic Data from the Faroes: An Integrated Workflow using Modeling and SRME

Nguyen

Brown

2009

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TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractMultiple is a long-standing problem in petroleum seismology. Despite significant achievements in developing advanced techniques to attenuate multiples, there is currently no single multiple-attenuation technique that can be applied to attenuate all the various types of multiples. The performance of each technique depends on the particular dataset. Selecting an optimal technique (or an optimal combination of schemes) lies in determining whether the Earth models implicit in a particular technique match the Earth model from which the seismic data were physically acquired. In this paper we present an integrated workflow using seismic modelling and SRME (Surface-Related Multiple Elimination) to attenuate multiples for the GlyVeST (Glyvursnes -Vestmanna Seismic Tie) seismic data, which were acquired in the Faore Islands. First, we carried out the GlyVeST seismic modelling, which has shown, among other things, that surface-related multiples are much stronger and more of a problem than internal multiples. Subbasalt seismic processing is well known to face challenges from severe scattering losses by impedance contrasts and rugose surfaces, geometrical spreading, velocity heterogeneity and strong multiples. As there can be great uncertainty in going from real data to interpretation, we gain insight by starting with an assumed or 'known' geology and generating synthetic data from it. Then, processing these data, knowing the correct result, guides us to an optimal processing strategy. The synthetic data, produced by an elastic finite-difference modelling scheme, offer excellent possibilities for detailed studies of how seismic waves interact with heterogeneous basalt flows, as well as better understanding of the multiple problem. Instead of resorting to trial-and-error, i.e. testing many different multiple-attenuation methods and picking the most pleasing result -wasteful of time and computer resources -the GlyVeST seismic modelling has helped us to determine a multiple-attenuation strategy for the Earth model from which the real GlyVeST seismic data were acquired. Based on the characteristics of our multiples (i.e. surface-related multiples much stronger than internal multiples), we have applied SRME, a technique that attenuates surface-related multiples as much as possible, followed by predictive deconvolution on the GlyVeST data. Finally, having conditioned the data for velocity analysis, we apply a high-resolution Radon demultiple routine in a series of iterative passes (velocity analysis -Radon demultiple -velocity analysis), progressively harsher as confidence in the velocity trend increases. As a result, multiples have been effectively attenuated without harming primary events in the data.

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Preliminary results from investigations of seismic and petrophysical properties of Faroes basalts in the SeiFaBa project

Cited by 16 publications

References 22 publications

Seismic attenuation of Atlantic margin basalts: Observations and modeling

Seismic attenuation of Atlantic margin basalts: Observations and modeling

Flood basalt facies from borehole data: implications for prospectivity and volcanology in volcanic rifted margins

Multiple Attenuation for the GlyVeST Seismic Data from the Faroes: An Integrated Workflow using Modeling and SRME

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