Elasticity of high‐porosity sandstones: Theory for two North Sea data sets

Geophysics ◽  
1996 ◽  
Vol 61 (5) ◽  
pp. 1363-1370 ◽  
Author(s):  
Jack Dvorkin ◽  
Amos Nur
Keyword(s):  
Lower Bound ◽  
North Sea ◽  
Pressure Dependence ◽  
Laboratory Data ◽  
Confining Pressure ◽  
The Other ◽  
Data Sets ◽  
High Porosity ◽  
Critical Porosity ◽  
The North

We have analyzed two laboratory data sets obtained on high‐porosity rock samples from the North Sea. The velocities observed are unusual in that they seem to disagree with some simple models based on porosity. On the other hand, the rocks are unusually poorly‐cemented (for laboratory studies, at least), and we investigate the likelihood that this is the cause of the disagreement. One set of rocks, from the Oseberg Field, is made of slightly cemented quartz sands. We find that we can model their dry‐rock velocities using a cementation theory where the grains mechanically interact through cement at the grain boundaries. This model does not allow for pressure dependence. The other set of rocks, from the Troll Field, is almost completely uncemented. The grains are held together by the applied confining pressure. In this case, a lower bound for the velocities can be found by using the Hertz‐Mindlin contact theory (interaction of uncemented spheres) to predict velocities at a critical porosity, combined with the modified Hashin‐Strikman lower bound for other porosities. This model, which allows for pressure‐dependence, also predicts fairly large Poisson’s ratios for saturated rocks, such as those observed in the measurements. The usefulness of these theories may be in estimating the nature of cement in rocks from measurements such as sonic logs. The theories could help indicate sand strength in poorly consolidated formations and predict the likelihood of sand production. Both theoretical methods have analytical expressions and are ready for practical use.

The other price of Britain's oil: Safety and Control in the North Sea

Marine Policy ◽  
1982 ◽  
Vol 6 (4) ◽  
pp. 335-337
Author(s):  
Patricia Birnie
Keyword(s):  
North Sea ◽  
The Other ◽  
The North ◽  
The North Sea ◽  
And Control

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

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

<p>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 km<sup>2</sup> of high-quality 3D seismic data and 150 km<sup>2</sup> 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.</p><p>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 km<sup>2</sup>) 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.</p>

scholarly journals Report on the Surface Collections made by Mr. W. T. Grenfell in the North Sea and West of Scotland

1890 ◽  
Vol 1 (4) ◽  
pp. 376-381 ◽  
Author(s):  
Gilbert C. Bourne
Keyword(s):  
Sulphuric Acid ◽  
North Sea ◽  
Deep Sea ◽  
Early Spring ◽  
The Other ◽  
The West ◽  
The North ◽  
The North Sea

Mr. Wilfrid Grenfell, the Superintendent of the Mission to Deep Sea Fishermen, has most kindly arranged to carry on a series of observations on the pelagic fauna and the fishes of the seas traversed by the Mission boats in the course of their work. The following report gives an account of the pelagic fauna collected in the North Sea during the early spring, and in the west of Scotland and Kinsale Harbour during the summer. The collections were preserved in picro-sulphuric acid and spirit, and were forwarded to Plymouth for examination. Owing to pressure of work, and to my leaving Plymouth somewhat unexpectedly, I have not been able to make a thorough investigation of all the collections, but have worked out the Copepoda with care, and have confined myself to short notes on the other species.

scholarly journals On the tides, bed and coasts of the North Sea or German Ocean

1854 ◽  
Vol 6 ◽  
pp. 201-202
Keyword(s):  
The Netherlands ◽  
North Sea ◽  
The Other ◽  
Great Similarity ◽  
Shetland Islands ◽  
Norwegian Coast ◽  
The North ◽  
The North Sea ◽  
The Baltic ◽  
Long Channel

The author commences his paper by remarking that great similarity of outline pervades the western shores of Ireland, Scotland and Norway, and then observes that the great Atlantic flood-tide wave, having traversed the shores of the former countries, strikes with great fury the Norwegian coast between the Lafoden Isles and Stadland, one portion proceeding to the north, while the other is deflected to the south, which last has scooped out along the coast, as far as the Sleeve at the mouth of the Baltic, a long channel from 100 to 200 fathoms in depth, almost close in shore, and varying from 50 to 100 miles in width. After describing his method of contouring and colouring the Admiralty chart of the North Sea, he traces the course of the tide-wave among the Orkney and Shetland Islands along the eastern shores of Scotland and England to the Straits of Dover, and along the western shores of Norway, Denmark and the Netherlands, to the same point.

scholarly journals VALIDATION OF CROSS-SHORE TRANSPORT FORMULATIONS

1988 ◽  
Vol 1 (21) ◽  
pp. 124 ◽  
Author(s):  
Richard J. Seymour ◽  
David Castel
Keyword(s):  
Atlantic Coast ◽  
Laboratory Data ◽  
Time History ◽  
The Other ◽  
Data Sets ◽  
Beach Profile ◽  
Nearshore Sediment Transport ◽  
History Of ◽  
Profile Changes ◽  
Profile Position

Seymour and King (1982) evaluated eight models for predicting cross-shore transport using beach profile data from the Torrey Pines experiment of the Nearshore Sediment Transport Study (NSTS). None of the models showed useful skill in predicting the sense, or direction, of transport. Three more data sets were acquired under NSTS and have been used in the present work to re-evaluate the original four models as well as another six not previously tested. The three new data sets include two nominally plane West Coast beaches and a barred beach on the Atlantic coast, each under a variety of wave conditions. Six of the models evaluated claimed a capability to predict the sense of the cross-shore transport, two predicted the beach slope as a result of cross-shore movement, and two gave detail predictions of changes to the beach profile position and shape. The performance of the six models predicting direction of transport ranged from a skill factor of 0.49 (less than chance) to only 0.68. Five of the models required large changes to their calibration factor (usually based upon laboratory data) in order to have approximately the same skill in predicting erosion or accretion. One of the slope models was validated and the other gave no useful results. One of the two generalized models gave interesting results in predicting the time history of profile changes on the plane beaches for which it was developed. The other general model was not evaluated because it exhibited the lowest skill in predicting direction of transport.

scholarly journals LAND RECLAMATION AND GROIN-BUILDING IN THE TIDAL PLATS

1970 ◽  
Vol 1 (12) ◽  
pp. 66
Author(s):  
Hele Focken Erchinger
Keyword(s):  
The Netherlands ◽  
North Sea ◽  
Land Reclamation ◽  
Tidal Flats ◽  
The Other ◽  
The North ◽  
The North Sea

Along the North Sea eoast of Germany there are two large areas where land reclamation work in the tidal flats is being carried out. One is on the coast of Schleswig- Holstem and the other in Ostfriesland, on the coast and along the estuary of the river Ems near the border with the Netherlands. Conditions and working methods for land reclamation in tidal flats as well as the development of new groin constructions on the Ostfriesian coast are described below.

Pressure-dependent seismic velocities based on effective compliance theory and an asperity deformation model

Geophysics ◽  
2012 ◽  
Vol 77 (6) ◽  
pp. D229-D243 ◽  
Author(s):  
Kai Gao ◽  
Richard L. Gibson
Keyword(s):  
Pressure Dependence ◽  
Laboratory Data ◽  
Confining Pressure ◽  
Time Lapse ◽  
Hertzian Contact ◽  
Deformation Model ◽  
Seismic Velocities ◽  
Power Law Distribution ◽  
S Wave ◽  
Effective Compliance

Seismic velocities of rocks depend strongly on confining pressure, which is often explained by the fracture compliances changes within the rocks. It is important to have an accurate model describing the relations between confining pressure and seismic velocities for applications such as time-lapse reservoir characterization. We propose a new model to address this problem by combining the existing effective compliance theory with new solutions for the pressure dependence of fracture compliances. Specifically, we assume the fracture contact surface can be represented by a set of elastic hemispheres with radii following power-law distribution, and the pressure dependence of seismic velocities can be expressed through pressure-dependent normal and tangential fracture compliances that are derived from Hertzian contact theory. Joint data fittings of P- and S-wave velocity laboratory data show that our model is accurate. We also implement fluid substitution using our model to explain the similar stress-induced velocity variations of fluid-saturated fractured rocks.

Introduction to this special section: Case studies: Conventionals

2019 ◽  
Vol 38 (1) ◽  
pp. 10-10
Author(s):  
Shauna Oppert ◽  
Matthew Casey ◽  
Kyle T. Spikes
Keyword(s):  
Case Studies ◽  
North Sea ◽  
Reservoir Characterization ◽  
Special Section ◽  
Data Sets ◽  
The North ◽  
The North Sea ◽  
Well Data ◽  
Conventional Systems ◽  
Innovative Techniques

Case studies, with a focus on conventional systems, provide insight of seismic and well data sets in terms of characterizing reservoirs with innovative techniques and approaches. This special section contains three such papers from three different regions: offshore Brazil, the North Sea, and the Middle East. Each contribution presents a different geologic problem ranging from siliciclastics to volcanics to carbonates. The challenges faced in each paper were tackled using innovative approaches to reservoir characterization in complex geologic regions.

Sign in / Sign up

Export Citation Format

Share Document