scholarly journals Geohazard detection using 3D seismic data to enhance offshore scientific drilling site selection

2020 ◽  
Vol 28 ◽  
pp. 1-27 ◽  
Author(s):  
David R. Cox ◽  
Paul C. Knutz ◽  
D. Calvin Campbell ◽  
John R. Hopper ◽  
Andrew M. W. Newton ◽  
...  
Keyword(s):  
Site Selection ◽  
Seismic Data ◽  
Seismic Survey ◽  
3D Seismic ◽  
Seismic Reflection Data ◽  
Scientific Drilling ◽  
The North ◽  
Reflection Data ◽  
3D Seismic Data ◽  
Geohazard Assessment

Abstract. A geohazard assessment workflow is presented that maximizes the use of 3D seismic reflection data to improve the safety and success of offshore scientific drilling. This workflow has been implemented for International Ocean Discovery Program (IODP) Proposal 909 that aims to core seven sites with targets between 300 and 1000 m below seabed across the north-western Greenland continental shelf. This glaciated margin is a frontier petroleum province containing potential drilling hazards that must be avoided during drilling. Modern seismic interpretation techniques are used to identify, map and spatially analyse seismic features that may represent subsurface drilling hazards, such as seabed structures, faults, fluids and challenging lithologies. These hazards are compared against the spatial distribution of stratigraphic targets to guide site selection and minimize risk. The 3D seismic geohazard assessment specifically advanced the proposal by providing a more detailed and spatially extensive understanding of hazard distribution that was used to confidently select eight new site locations, abandon four others and fine-tune sites originally selected using 2D seismic data. Had several of the more challenging areas targeted by this proposal only been covered by 2D seismic data, it is likely that they would have been abandoned, restricting access to stratigraphic targets. The results informed the targeted location of an ultra-high-resolution 2D seismic survey by minimizing acquisition in unnecessary areas, saving valuable resources. With future IODP missions targeting similarly challenging frontier environments where 3D seismic data are available, this workflow provides a template for geohazard assessments that will enhance the success of future scientific drilling.

Why 3D seismic data are an asset for exploration and mine planning? Velocity tomography of weakness zones in the Kevitsa Ni-Cu-PGE mine, northern Finland

Geophysics ◽  
2018 ◽  
Vol 83 (2) ◽  
pp. B33-B46 ◽  
Author(s):  
Alireza Malehmir ◽  
Ari Tryggvason ◽  
Chris Wijns ◽  
Emilia Koivisto ◽  
Teemu Lindqvist ◽  
...  
Keyword(s):  
Seismic Data ◽  
Mine Planning ◽  
Seismic Survey ◽  
Open Pit ◽  
3D Seismic ◽  
Reflection Data ◽  
Northern Side ◽  
Weakness Zone ◽  
Weakness Zones ◽  
3D Seismic Data

Kevitsa is a disseminated Ni-Cu-PGE (platinum group elements) ore body in northern Finland, hosted by an extremely high-velocity ([Formula: see text]) ultramafic intrusion. It is currently being mined at a depth of approximately 100 m with open-pit mining. The estimated mine life is 20 years, with the final pit reaching a depth of 500–600 m. Based on a series of 2D seismic surveys and given the expected mine life, a high-resolution 3D seismic survey was justified and conducted in the winter of 2010. We evaluate earlier 3D reflection data processing results and complement that by the results of 3D first-arrival traveltime tomography. The combined results provide insights on the nature of some of the reflectors within the intrusion. In particular, a major discontinuity, a weakness zone, is delineated in the tomography results on the northern side of the planned pit. Supported by the reflection data, we estimate the discontinuity, likely a thrust sheet, to extend down approximately 600 m and laterally 1000 m. The weakness zone terminates prominent internal reflectivity of the Kevitsa intrusion, and it is associated with the extent of the economic mineralization. Together with other weakness zones, a couple of which are also revealed by the tomography study, the discontinuity forms a major wedge block that influences the mine bench stability on the northern side of the open pit and likely will cause more issues during the extraction of the ore in this part of the mine. We argue that 3D seismic data should routinely be acquired prior to commencement of mining activities to maximize exploration efficiency at depth and also to optimize mining as it continues toward depth. Three-dimensional seismic data over mineral exploration areas are valuable and can be revisited for different purposes but are difficult to impossible to acquire after mining has commenced.

New insights into North Sea tunnel valley infill and genesis from high-resolution 3D seismic data

2020 ◽  
Author(s):  
James Kirkham ◽  
Kelly Hogan ◽  
Robert Larter ◽  
Ed Self ◽  
Ken Games ◽  
...  
Keyword(s):  
High Resolution ◽  
North Sea ◽  
Seismic Data ◽  
3D Seismic ◽  
Seismic Reflection Data ◽  
North West ◽  
The North ◽  
Reflection Data ◽  
Order Of Magnitude ◽  
Subglacial Meltwater

<p>Tunnel valleys are large (kilometres wide, hundreds of metres deep) channels incised into bedrock and soft sediments by the action of pressurised subglacial meltwater. Discovered over a century ago, they are common across large swathes of North-West Europe and North America. However, many aspects of tunnel valley formation, and the processes by which they are infilled, remain poorly understood. Here, we use new high-resolution 3D seismic reflection data, collected by the geohazard assessment industry, to examine the infill lithology and architecture of buried tunnel valleys located in the central North Sea. The spatial resolution of our seismic data (3.125-6.25 m bin size) represents an order of magnitude improvement in the data resolution that has previously been used to study tunnel valleys in this region, allowing us to examine their infill in unprecedented detail. Inside the tunnel valleys, we identify a suite of buried subglacial landforms, some of which have rarely been reported inside tunnel valleys before. These landforms include a 14-km-long system of segmented eskers, crevasse-squeeze ridges, subsidiary meltwater channels and retreat moraines. Their presence suggests that, in some cases, tunnel valleys in the North Sea were reoccupied by ice following their initial formation, casting doubt on hypotheses which invoke catastrophic releases of water to explain tunnel valley creation.</p>

Detailed Geomorphology of Cold Seeps Associated with a Buried Salt Diapir, Offshore Nova Scotia, Canada

2020 ◽  
Author(s):  
Calvin Campbell ◽  
Alexandre Normandeau ◽  
Paul Fraser ◽  
Adam MacDonald
Keyword(s):  
Nova Scotia ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Cold Seep ◽  
Salt Diapir ◽  
Cold Seeps ◽  
3D Seismic ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
3D Seismic Data

<p>Cold seeps occur where fluids, such as hydrocarbons, migrate from depth and escape at the seabed. They are relatively common features in petroleum basins around the world. Cold seeps often host unique biological communities and are a potential geological hazard as they can indicate excess pore fluid pressures in shallow sediments. In addition, they can provide critical information about fluid migration pathways and fluid source. This study presents the detailed geomorphology and seismic stratigraphy of recently discovered cold seeps in 2700 metres water depth offshore Nova Scotia, Canada. </p><p>Petroleum industry 3D seismic reflection data, high-resolution single channel G.I. gun and sparker seismic reflection data, Autonomous Underwater Vehicle (AUV) sidescan, swath bathymetry, and sub-bottom profiler data were used to investigate the geomorphology of the cold seep and surrounding seabed. Piston core samples and seabed photography were also acquired in the study area.</p><p>The geomorphology in the study area is dominated by the seafloor expression of a salt diapir (L. Triassic to E. Jurassic). Despite being buried by ~1700 m of Cretaceous to Holocene sediment, the diapir forms an oblong mound, 10 km long by 5 km wide that rises 200 m above the surrounding seabed. Two major orthogonal faults are apparent on the seabed that cut the mound along its major and minor axes. Several crestal faults are imaged in the 3D seismic data but do not have a seabed expression. AUV data acquired over the crest of the diapir reveal a 500 m by 200 m fissure on the western flank of the diapir. The fissure is composed of a blocky central zone along its axis, and radiating “cracks” that show backscatter variation, possibly indicating recent fluid expulsion. Integration of the AUV data with the 3D seismic data show that the fissure is fed by a vertical chimney that intersects a bottom simulating reflection above the diapir. Remarkably, the chimney does not appear to be related to any of the sub-vertical crestal faults. Another seep occurs on the eastern flank of the diapir crest and, in contrast, coincides with a crestal fault. There is also evidence for mass wasting down-dip from the fault. Core samples recovered from the second seep contained gas hydrate. In both cases, the cold seeps present as very subtle features on the 3D seismic reflection data and are only positively identified in the AUV datasets. This study shows that conventional surface-acquired acoustic data are potentially insufficient for detecting cold seep morphologies in deep-water settings.</p>

Approach to Geohazard Assessment Based on 2D/3D Seismic Data on The Pechora Sea Shelf

2021 ◽  
Author(s):  
M.A. Solovyeva ◽  
Y.E. Terekhina ◽  
O.A. Khlebnikova ◽  
M.Yu. Tokarev ◽  
S.V. Gorbachev ◽  
...  
Keyword(s):  
Seismic Data ◽  
3D Seismic ◽  
3D Seismic Data ◽  
Geohazard Assessment

DEMETER HIGH RESOLUTION 3D SEISMIC SURVEY—REVITALISED DEVELOPMENT AND EXPLORATION ON THE NORTH WEST SHELF, AUSTRALIA

2006 ◽  
Vol 46 (1) ◽  
pp. 101 ◽  
Author(s):  
K.J. Bennett ◽  
M.R. Bussell
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
New Technologies ◽  
Seismic Survey ◽  
Future Application ◽  
3D Seismic ◽  
Gas Field ◽  
North West ◽  
The North ◽  
Exploration And Development

The newly acquired 3,590 km2 Demeter 3D high resolution seismic survey covers most of the North West Shelf Venture (NWSV) area; a prolific hydrocarbon province with ultimate recoverable reserves of greater than 30 Tcf gas and 1.5 billion bbls of oil and natural gas liquids. The exploration and development of this area has evolved in parallel with the advent of new technologies, maturing into the present phase of revitalised development and exploration based on the Demeter 3D.The NWSV is entering a period of growing gas market demand and infrastructure expansion, combined with a more diverse and mature supply portfolio of offshore fields. A sequence of satellite fields will require optimised development over the next 5–10 years, with a large number of wells to be drilled.The NWSV area is acknowledged to be a complex seismic environment that, until recently, was imaged by a patchwork of eight vintage (1981–98) 3D seismic surveys, each acquired with different parameters. With most of the clearly defined structural highs drilled, exploration success in recent years has been modest. This is due primarily to severe seismic multiple contamination masking the more subtle and deeper exploration prospects. The poor quality and low resolution of vintage seismic data has also impeded reservoir characterisation and sub-surface modelling. These sub-surface uncertainties, together with the large planned expenditure associated with forthcoming development, justified the need for the Demeter leading edge 3D seismic acquisition and processing techniques to underpin field development planning and reserves evaluations.The objective of the Demeter 3D survey was to re-image the NWSV area with a single acquisition and processing sequence to reduce multiple contamination and improve imaging of intra-reservoir architecture. Single source (133 nominal fold), shallow solid streamer acquisition combined with five stages of demultiple and detailed velocity analysis are considered key components of Demeter.The final Demeter volumes were delivered early 2005 and already some benefits of the higher resolution data have been realised, exemplified in the following:Successful drilling of development wells on the Wanaea, Lambert and Hermes oil fields and identification of further opportunities on Wanaea-Cossack and Lambert- Hermes;Dramatic improvements in seismic data quality observed at the giant Perseus gas field helping define seven development well locations;Considerably improved definition of fluvial channel architecture in the south of the Goodwyn gas field allowing for improved well placement and understanding of reservoir distribution;Identification of new exploration prospects and reevaluation of the existing prospect portfolio. Although the Demeter data set has given significant bandwidth needed for this revitalised phase of exploration and development, there remain areas that still suffer from poor seismic imaging, providing challenges for the future application of new technologies.

Quaternary evolution of the northern North Sea

2020 ◽  
Author(s):  
Christine Batchelor ◽  
Dag Ottesen ◽  
Benjamin Bellwald ◽  
Sverre Planke ◽  
Helge Løseth ◽  
...  
Keyword(s):  
North Sea ◽  
Seismic Data ◽  
3D Seismic ◽  
Quaternary Sediments ◽  
The North ◽  
The North Sea ◽  
Data Coverage ◽  
Northern North Sea ◽  
2D And 3D ◽  
3D Seismic Data

<p>The North Sea has arguably the most extensive geophysical data coverage of any glacier-influenced sedimentary regime on Earth, enabling detailed investigation of the thick (up to 1 km) sequence of Quaternary sediments that is preserved within the North Sea Basin. At the start of the Quaternary, the bathymetry of the northern North Sea was dominated by a deep depression that provided accommodation for sediment input from the Norwegian mainland and the East Shetland Platform. Here we use an extensive database of 2D and 3D seismic data to investigate the geological development of the northern North Sea through the Quaternary.</p><p>Three main sedimentary processes were dominant within the northern North Sea during the early Quaternary: 1) the delivery and associated basinward transfer of glacier-derived sediments from an ice mass centred over mainland Norway; 2) the delivery of fluvio-deltaic sediments from the East Shetland Platform; and 3) contourite deposition and the reworking of sediments by contour currents. The infilling of the North Sea Basin during the early Quaternary increased the width and reduced the water depth of the continental shelf, facilitating the initiation of the Norwegian Channel Ice Stream.</p>

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>

Diapiric shale and coast-perpendicular, fault-related subbasins, south Texas Gulf Coast

2015 ◽  
Vol 3 (2) ◽  
pp. T43-T56 ◽  
Author(s):  
Osareni C. Ogiesoba ◽  
Rodolfo Hernandez
Keyword(s):  
Seismic Data ◽  
Gulf Coast ◽  
Structural Features ◽  
South Texas ◽  
3D Seismic ◽  
Texas Gulf Coast ◽  
Vertical Loading ◽  
The North ◽  
Visualization Tools ◽  
3D Seismic Data

Coast-perpendicular shale ridges are rare structural features worldwide, and their origin remains a subject of debate. We studied some coast-perpendicular shale ridges and faults within a minibasin located onshore in Refugio County in the Texas Gulf Coast. We used 3D seismic data, visualization tools, and seismic attributes to examine the geometry of coast-perpendicular diapiric structures associated subbasins (SBs) and faults, and coast-parallel listric faults. Our results indicated that the minibasin is subdivided into four SBs by five diapiric shale ridges that intrude through the fault heaves of down-to-the-basin (synthetic) and coast-perpendicular faults. Three of the SBs are oriented perpendicular to the coast, whereas the fourth has a curvilinear form trending northeast–southwest–southeast. Of the five diapiric shale ridges, three are coast-perpendicular. The other two are curvilinear to the coast. All five diapiric shale ridges are associated with coast-perpendicular faults that bound the flanks of the ridges. On the basis of our mapping results, we deduced that the origin of the coast-perpendicular faults in the study area are related to the coalescing of en echelon synthetic faults, as well as the coalition of synthetic and antithetic fault planes. We inferred that the origin of the shale diapirs is related to vertical loading and, possibly, local southwest–northeast lateral compression of interbedded, overpressured, shale-prone intervals. The coast-perpendicular faults within the Frio formed as a result of reactivation of the Eocene-Vicksburg coast-perpendicular faults. Synthetic faults dominate the pattern within the SB in the north where shale ridges are broad, whereas antithetic faults dominate the pattern in the south where shale ridges are narrow.

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