Reconstruction of 3D-horizons from 3D-seismic data sets

Extensive, Gas-charged Quaternary Sand Accumulations of the Northern North Sea and North Sea Fan

10.5194/egusphere-egu2020-18701 ◽

2020 ◽

Author(s):

Benjamin Bellwald ◽

Sverre Planke ◽

Sunil Vadakkepuliyambatta ◽

Stefan Buenz ◽

Christine Batchelor ◽

...

Keyword(s):

North Sea ◽

Seismic Data ◽

Data Sets ◽

3D Seismic ◽

Fine Grained ◽

The North ◽

Northern North Sea ◽

Well Data ◽

Sea Fan ◽

3D Seismic Data

Sediments deposited by marine-based ice sheets are dominantly fine-grained glacial muds, which are commonly known for their sealing properties for migrating fluids. However, the Peon and Aviat hydrocarbon discoveries in the North Sea show that coarse-grained glacial sands can occur over large areas in formerly glaciated continental shelves. In this study, we use conventional and high-resolution 2D and 3D seismic data combined with well information to present new models for large-scale fluid accumulations within the shallow subsurface of the Norwegian Continental Shelf. The data include 48,000 km2 of high-quality 3D seismic data and 150 km2 of high-resolution P-Cable 3D seismic data, with a vertical resolution of 2 m and a horizontal resolution of 6 to 10 m in these data sets. We conducted horizon picking, gridding and attribute extractions as well as seismic geomorphological interpretation, and integrated the results obtained from the seismic interpretation with existing well data.The thicknesses of the Quaternary deposits vary from hundreds of meters of subglacial till in the Northern North Sea to several kilometers of glacigenic sediments in the North Sea Fan. Gas-charged, sandy accumulations are characterized by phase-reserved reflections with anomalously high amplitudes in the seismic data as well as density and velocity decreases in the well data. Extensive (>10 km2) Quaternary sand accumulations within this package include (i) glacial sands in an ice-marginal outwash fan, sealed by stiff glacial tills deposited by repeated glaciations (the Peon discovery in the Northern North Sea), (ii) sandy channel-levee systems sealed by fine-grained mud within sequences of glacigenic debris flows, formed during shelf-edge glaciations, (iii) fine-grained glacimarine sands of contouritic origin sealed by gas hydrates, and (iv) remobilized oozes above large evacuation craters and sealed by megaslides and glacial muds. The development of the Fennoscandian Ice Sheet resulted in a rich variety of depositional environments with frequently changing types and patterns of glacial sedimentation. Extensive new 3D seismic data sets are crucial to correctly interpret glacial processes and to analyze the grain sizes of the related deposits. Furthermore, these data sets allow the identification of localized extensive fluid accumulations within the Quaternary succession and distinguish stratigraphic levels favorable for fluid accumulations from layers acting as fluid barriers.

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Mesozoic tectonostratigraphic evolution of the North Carnarvon Basin unlocked using regional 3D seismic

The APPEA Journal ◽

10.1071/aj15070 ◽

2016 ◽

Vol 56 (2) ◽

pp. 564

Author(s):

Daniel Bishop ◽

Megan Halbert ◽

Katherine Welbourn ◽

Ben Boterhoven ◽

Stacey Mansfield ◽

...

Keyword(s):

Seismic Data ◽

Regional Scale ◽

Depositional Environments ◽

Single Channels ◽

Data Sets ◽

3D Seismic ◽

The North ◽

Basin Scale ◽

3D Seismic Data ◽

Carnarvon Basin

Interpretation of regional scale merged 3D seismic data sets covering the North Carnarvon Basin has for the first time enabled a detailed description of Mesozoic stratigraphic and structural features on a basin scale. Isoproportional slicing of the data enables direct interpretation of Triassic depositional environments, including contrasting low-stand and high-stand fluvial channel complexes, marginal marine clastic systems and reef complexes. Channels vary dramatically between sinuous-straight single channels within low net:gross floodplain successions, to broad channel belts within relatively high net:gross fluvial successions. The latter can be traced from the inboard part of the basin to the outer areas of the Exmouth Plateau. 3D visualisation and interpretation has demonstrated the huge variety of structural styles that are present, including basement-involved extensional faults, detached listric fault complexes, polygonal faults, and regional scale vertical strike-slip faults with flower structures. Fault trends include north–south, north–northeast to south–southwest, and northeast–southwest, with deformation events occurring mainly between the Rhaetian and Valanginian. Extensional and compressional deformation has created multiple horsts, three-way fault closures, fold belts and associated four-way anticlinal traps. Wrench tectonics may also explain pock-mark trains with the interpreted transfer of over-pressure from Triassic to Early Cretaceous levels. The use of regional scale merged 3D seismic data sets is now shedding light on tectonostratigraphic features on a basin scale that were previously unrecognised or enigmatic on 2D seismic or local 3D seismic data sets.

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Stabilizing the phase of onshore 3D seismic data

Geophysics ◽

10.1190/geo2019-0695.1 ◽

2020 ◽

Vol 85 (6) ◽

pp. V473-V479

Author(s):

Rob Holt ◽

Andy Lubrano

Keyword(s):

Phase Stability ◽

Seismic Data ◽

Synthetic Seismograms ◽

Small Subset ◽

Data Sets ◽

3D Seismic ◽

Phase Instability ◽

Generate Surface ◽

High Level ◽

3D Seismic Data

When present, surface-consistent (shot and/or receiver) phase instability will generate surface-consistent time shifts that are at least partially removed from seismic data when surface-consistent residual statics corrections are applied. The phase instability will not be fully corrected and lingers undetected in the data throughout the remainder of the processing workflow. After processing finishes, seismic interpreters often need to apply laterally varying phase rotations to tie their onshore 3D seismic data to synthetic seismograms, before starting detailed stratigraphic interpretation projects. We have developed and tested a new surface-consistent seismic processing workflow that can be applied to increase the phase stability of our seismic data. It is run after the final pass of conventional surface-consistent residual shot and receiver statics corrections have been applied to optimally align the seismic traces. The phase stability corrections are estimated from an additional pass of surface-consistent residual shot and receiver statics corrections that are calculated on the phase-independent seismic trace envelopes. We demonstrate the application of the workflow using synthetic and real seismic data. We gained confidence that the workflow was performing as expected after we intentionally phase rotated a small subset of the shots and receivers in our seismic test data sets and observed that the workflow corrected these intentionally phase-rotated traces with a high level of accuracy.

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Unravelling an abandoned giant in Central Luconia Province, offshore Sarawak, Malaysia — Success story of Lang Lebah

The Leading Edge ◽

10.1190/tle39080566.1 ◽

2020 ◽

Vol 39 (8) ◽

pp. 566-573

Author(s):

Aqilah Amir Jamalullail ◽

Ong Swee Keong ◽

Nik Ruzaimi Akmal Nik Ruhadi ◽

Tengku Mohd Syazwan Tengku Hassan ◽

Detchai Ittharat ◽

...

Keyword(s):

Seismic Data ◽

Reservoir Quality ◽

Data Sets ◽

3D Seismic ◽

Success Story ◽

Seismic Acquisition ◽

Central Luconia ◽

Drilling Conditions ◽

3D Seismic Data ◽

Carbonate Buildup

In 1994, two exploration wells were drilled consecutively to explore for gas prospectivity in Lang Lebah, a Miocene carbonate buildup in the geologic province of Central Luconia located in the Sarawak Basin in Malaysia. High overpressure and operational problems prevented both wells from fully evaluating the target. Postdrill analysis concluded that Lang Lebah has limited potential due to poor reservoir quality, small gas column, and challenging drilling conditions. For these reasons, it was left dormant for 25 years. In 2016, new 3D broadband seismic acquisition and megamerge reprocessing of 3D seismic data sets followed by an integrated application of multidisciplinary workflows successfully derisked key petroleum system elements of the Lang Lebah structure, yielding a more optimistic view of its potential. A new well was justified at Lang Lebah and resulted in one of the major gas discoveries of 2019.

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