Triassic mudstones of the Central North Sea: cross-border characterization, correlation and their palaeoclimatic significance

2020 ◽  
pp. SP494-2019-61
Author(s):  
Stuart G. Archer ◽  
Tom McKie ◽  
Steven D. Andrews ◽  
Anne D. Wilkins ◽  
Matt Hutchison ◽  
...  
Keyword(s):  
North Sea ◽  
Large Scale ◽  
Regional Scale ◽  
Climatic Conditions ◽  
Fluvial Systems ◽  
Correlation Lengths ◽  
Cross Border ◽  
The Uk ◽  
Stratigraphic Nomenclature ◽  
Central North Sea

AbstractThe Triassic of the Central North Sea is a continental succession that contains prolific hydrocarbon-bearing fluvial sandstone reservoirs stratigraphically partitioned by mudstones. Within the Skagerrak Formation of the UK sector, hydrocarbon accumulations in the Judy, Joanne and Josephine Sandstone members are top sealed by the Julius, Jonathan and Joshua Mudstone members, respectively. However, UK and Norwegian stratigraphic correlations have been problematical for decades, largely due to biostratigraphic challenges but also due to the non-uniqueness of the lithotypes and because the cross-border stratigraphic nomenclature differs and has yet to be rationalized. This study focuses on mudstones rather than sandstones to unify cross-border correlation efforts at a regional scale. The mudstone members have been characterized by integrating sedimentological, petrophysical and geophysical data. The facies are indicative of playa lakes that frequently desiccated and preserved minor anhydrite. These conditions alternated with periods of marshy, palustrine conditions favourable for the formation of dolostones. Regional correlations have detected lateral facies changes in the mudstones which are important for their seismically mappable extents, resulting palaeogeographies and, ultimately, their competency as intraformational top seals. Significant diachroneity is associated with the lithological transitions at sandstone–mudstone member boundaries and although lithostratigraphic surfaces can be used as timelines over short distances (e.g. within a field), they should not be assumed to represent timelines over longer correlation lengths. Palaeoclimatic trends are interpreted and compared to those of adjacent regions to test the extent and impact of climate change as a predictive allogenic forcing factor on sedimentation. Mudstone member deposition occurred as a result of the retreat of large-scale terminal fluvial systems during a return to more arid ‘background’ climatic conditions. The cause of the member-scale climatic cyclicity observed within the Skagerrak Formation may be related to volcanic activity in large igneous provinces which triggered the episodic progradation of fluvial systems.

The MacCulloch Field, Block 15/24b, UK North Sea

2003 ◽  
Vol 20 (1) ◽  
pp. 453-466 ◽  
Author(s):  
C. Gunn ◽  
J. A. MacLeod ◽  
P. Salvador ◽  
J. Tomkinson
Keyword(s):  
North Sea ◽  
Water Contact ◽  
Northern Flank ◽  
Recoverable Reserves ◽  
Average Porosity ◽  
Oil Water ◽  
The Witch ◽  
The Uk ◽  
Clay Formation ◽  
Central North Sea

AbstractThe MacCulloch Field lies within Block 15/24b in the UK Central North Sea and is located on the northern flank of the Witch Ground Graben. It was discovered by Conoco well 15/24b-3 in 1990.MacCulloch Field is a four-way dip closure at Top Paleocene over a deeper Mesozoic structure. The reservoir consists of Upper Balmoral Sandstones containing 32-37° API oils derived from Kimmeridge Clay Formation shales and sealed by shales belonging to the Sele Formation. The field contains recoverable reserves of 60-90 MMBOE.Reservoir quality is generally very good, with an average porosity of 28% and core permeabilities (Kh) between 200 mD and 2D. AVO anomalies and a seismic flat spot are associated with oil filled reservoir and the oil-water contact in certain areas of the field.

Field map

2003 ◽  
Vol 20 (1) ◽  
pp. 132-132
Keyword(s):  
North Sea ◽  
Oil And Gas ◽  
Median Line ◽  
Moray Firth ◽  
The Uk ◽  
Central North Sea ◽  
International Border

AbstractMap depicting the position and names of the main oil and gas producing fields located in the Viking Graben and eastern parts of the Outer Moray Firth rift arms, Northern and Central North Sea. The international border (median line) between the UK and Norway is highlighted as are the producing fields in the Norwegian sector. The boxed areas show the extent of licensed acreage in the region.

The Machar Field, Block 23/26a, UK North Sea

2020 ◽  
Vol 52 (1) ◽  
pp. 523-536 ◽  
Author(s):  
Zoë Sayer ◽  
Jonathan Edet ◽  
Rob Gooder ◽  
Alexandra Love
Keyword(s):  
North Sea ◽  
Debris Flows ◽  
Water Injection ◽  
Salt Diapir ◽  
Reservoir Quality ◽  
Complex Interplay ◽  
Light Oil ◽  
High Matrix ◽  
The Uk ◽  
Central North Sea

AbstractMachar is one of several diapir fields located in the Eastern Trough of the UK Central North Sea. It contains light oil in fractured Cretaceous–Danian chalk and Paleocene sandstones draped over and around a tall, steeply-dipping salt diapir that had expressed seafloor relief during chalk deposition. The reservoir geology represents a complex interplay of sedimentology and evolving structure, with slope-related redeposition of both the chalk and sandstone reservoirs affecting distribution and reservoir quality. The best reservoir quality occurs in resedimented chalk (debris flows) and high-density turbidite sandstones. Mapping and characterizing the different facies present has been key to reservoir understanding.The field has been developed by water injection, with conventional sweep in the sandstones and imbibition drive in the chalk. Although the chalk has high matrix microporosity, permeability is typically less than 2 mD, and fractures are essential for achieving high flow rates; test permeabilities can be up to 1500 mD. The next phase of development is blowdown, where water injection is stopped and the field allowed to depressurize. This commenced in February 2018.

3D basin and petroleum system modelling in the North Sea Central Graben - a Dutch, German, Danish cross-border study

2020 ◽  
Author(s):  
Rüdiger Lutz ◽  
Jashar Arfai ◽  
Susanne Nelskamp ◽  
Anders Mathiesen ◽  
Niels Hemmingsen Schovsbo ◽  
...  
Keyword(s):  
Pilot Study ◽  
North Sea ◽  
Large Scale ◽  
Petroleum System ◽  
Source Rocks ◽  
System Model ◽  
Geochemical Data ◽  
System Modelling ◽  
Horizon 2020 ◽  
Cross Border

<p>A Geological Analysis and Resource Assessment of selected Hydrocarbon Systems (GARAH) is carried out as part of the overarching GeoERA project. Here, we report first results of a 3D basin and petroleum system model developed in a cross-border area of the Dutch, Danish and German North Sea Central Graben area. This pilot study reconstructs the thermal history, maturity and petroleum generation of potential Lower, Middle and Upper Jurassic source rocks. The 3D pilot study incorporates new aggregated and combined layers from the three countries. Results of the study feed back into the 3DGEO-EU project of GeoERA.</p><p>Eight key horizons covering the whole German Central Graben and parts of the Dutch and Danish North Sea Central Graben were selected for building the stratigraphic and geological framework of the 3D basin and petroleum system model. The model includes depth and thickness maps of important stratigraphic units as well as the main salt structures. Petrophysical parameters, generalized facies information and organic geochemical data from well reports are assigned to the different key geological layers. The model is further calibrated with temperature and maturity data from wells of the three countries and from publications. The time span from the Late Permian to the Present is represented by the model including the most important erosional phases related to large-scale tectonic events during the Late Jurassic to Late Cretaceous. Additionally, salt movement through time expressed as diapirs and pillows is considered within the 3D basin and petroleum system model.</p><p>This is a part of an ongoing EU Horizon 2020 GeoERA project (The GARAH, H2020 grant #731166 lead by GEUS).</p>

Exploration well failures from the UK North Sea

2016 ◽  
Vol 8 (1) ◽  
pp. 267-272 ◽  
Author(s):  
Christian J. H. Mathieu
Keyword(s):  
Peer Review ◽  
North Sea ◽  
Primary Reason ◽  
Success Rates ◽  
Moray Firth ◽  
The Uk ◽  
Central North Sea ◽  
Exploration Well ◽  
Play Context

AbstractThe UK Oil & Gas Authority carried out post-well failure analyses of exploration and appraisal wells in the Moray Firth and the UK Central North Sea to fully understand the basis for drilling the prospects and the reasons why the prospects failed.The data consisted of Tertiary, Mesozoic and Palaeozoic targets/segments associated with 97 wells drilled from 2003 to 2013. Seal was the primary reason for failure followed by trap, reservoir and charge. Root causes for failure were a lack of lateral seal, the absence of the target reservoir and the lack of a trap. The main pre-drill risk was not accurately predicted in over one-third of the cases and a third of the segments were targeted on the basis of perceived Direct Hydrocarbon Indicators.This study identified a number of interpretation gaps and pitfalls that ultimately contributed to the well failures. These included poor integration, improper application of geophysics, lack of regional play context, and absent or ineffective peer review. Addressing these gaps in a comprehensive and systematic way is fundamental to improving exploration success rates.

scholarly journals Resolving the spatial distributions of Dipturus intermedius and Dipturus batis—the two taxa formerly known as the ‘common skate’

2021 ◽  
Author(s):  
Maisie Bache-Jeffreys ◽  
Bárbara Lins Caldas de Moraes ◽  
Rachel E. Ball ◽  
Gui Menezes ◽  
Jónbjörn Pálsson ◽  
...  
Keyword(s):  
North Sea ◽  
Large Scale ◽  
Species Distribution Modelling ◽  
Distribution Model ◽  
Nominal Species ◽  
Spatial Distributions ◽  
The North ◽  
Control Region Haplotype ◽  
Northern North Sea ◽  
The Uk

AbstractBatoid fishes are among the most endangered marine vertebrates, yet conservation efforts have been confounded by incomplete taxonomy. Evidence suggest that the critically endangered ‘common skate’ actually represents two species: the flapper skate (Dipturus intermedius) and the blue skate (Dipturus batis). However, knowledge of the geographic range of these two nominal species is limited. Here, DNA sequencing is used to distinguish these species, allowing their spatial distributions to be clarified. These records were also used as the basis for species distribution modelling, providing the first broad scale models for each species across the Northeast Atlantic. Samples were obtained from Iceland, the UK (specifically Shetland), the North Sea and the Azores. Results suggest that D. batis was commonly distributed in the Western Approaches and Celtic Sea, extending out to Rockall and Iceland. D. intermedius generally appears to be less abundant, but was most frequent around northern Scotland and Ireland, including the northern North Sea, and was also present in Portugal. Two individuals were also identified from seamounts in remote areas of the Atlantic around the Azores, the furthest south and west the species has been found. This supports reports that the flapper skate historically had a much wider distribution (which was also highlighted in the distribution model), emphasising the large scale over which fisheries may have led to extirpations. Furthermore, these Azorean samples shared a unique control region haplotype, highlighting the importance of seamounts in preserving genetic diversity.

The Mungo Field, Blocks 22/20a and 23/16a, UK North Sea

2020 ◽  
Vol 52 (1) ◽  
pp. 537-549 ◽  
Author(s):  
G. M. Baniak ◽  
Z. Sayer ◽  
H. Patterson ◽  
R. Gooder ◽  
N. Laing ◽  
...  
Keyword(s):  
North Sea ◽  
Water Injection ◽  
Salt Diapir ◽  
Submarine Fans ◽  
Central Processing ◽  
Economic Production ◽  
Light Oil ◽  
Early Paleocene ◽  
The Uk ◽  
Central North Sea

AbstractThe Mungo Field is a mature producing asset located in the UK Central North Sea. Discovered in 1989 and brought on production in 1998, it is the largest field within the Eastern Trough Area Project (ETAP). Production occurs via a normally unattended installation and is tied back to the ETAP Central Processing Facility. It is a pierced, four-way dip closure against a salt diapir. Light oil is present within steeply dipping Late Paleocene sandstone and Early Paleocene–Late Cretaceous chalk intervals. The vertical relief of the salt stock is around 1500 m TVDSS and top of the salt canopy lies at about 1350 m TVDSS.The Paleocene sandstones (Forties Sandstone Member of the Sele Formation, Lista Formation and Maureen Formation) make up the primary reservoir and have been extensively developed in three phases since 1998 under water injection and natural depletion. The sandstones were deposited as deep-water turbidite complexes (submarine fans with local channels) on and around the flanks of the rising salt diapir. More recently, successful stimulation of the Chalk Group, coupled with re-evaluation of core and well-log data, has indicated that economic production rates could also be achieved from the underlying fractured chalk reservoir.

Diagenesis of the shallow marine Fulmar Formation in the Central North Sea

Clay Minerals ◽  
1986 ◽  
Vol 21 (4) ◽  
pp. 537-564 ◽  
Author(s):  
D. J. Stewart
Keyword(s):  
Clay Mineral ◽  
North Sea ◽  
Large Scale ◽  
Shear Zones ◽  
Upper Jurassic ◽  
Burial Diagenesis ◽  
Secondary Porosity ◽  
Shallow Marine ◽  
History Of ◽  
Central North Sea

AbstractThe diagenetic history of the Upper Jurassic Fulmar Formation of the Central North Sea is described with emphasis on the Fulmar Field. The Fulmar Formation was deposited on a variably subsiding shallow-marine shelf under the influence of halokinetic and fault movements. The sediments are extensively bio-destratified although large-scale cross-bedding is locally preserved. The dominant mechanism of deposition is thought to have been storm-generated currents. Soft-sediment deformation structures are common and are attributed to syn- and post-depositional dewatering of the sandstones. The dewatering was associated with fractures and shear zones which reflect tectonic instability resulting from periodic salt withdrawal and/or graben fault movements. The dewatering may have been initiated by repacking of the sediments during earth movements or by the gradual build-up and sudden release of overpressures due to compaction and/or clay mineral dehydration during rapid burial at the end of the Cretaceous. The formation is composed of arkosic sandstone of similar composition to Triassic sandstones from which it was probably derived. The sandstones also contain limited amounts of marine biogenic debris including sponge solenasters, bivalve shells, rare ammonites and belemnites. Initial diagenesis began with an environment-related phase during which quartz and feldspar overgrowths and chalcedony and calcite cements were precipitated. These cements appear to form concretions adjacent to local concentrations of sponge debris and shell debris, respectively, and were disturbed after their formation by fracturing and dewatering. This was followed by an early burial stage of diagenesis which resulted in extensive dolomite cementation and minor clay mineral authigenesis (illite and chlorite). The last phase of mineral growth was probably pyrite. During early burial diagenesis, secondary porosity after feldspar and/or carbonate was produced, although the exact timing is not clear. The lack of both stylolitic developments and extensive illitization indicates that the late burial diagenesis stage was never reached, although sufficient clay diagenesis occurred to destroy all traces of mixed-layer illite-smectite (present in some shallower wells). The main control on reservoir behaviour is primary depositional fabric. Diagenesis only overprints these controls. Locally-cemented fracture sets act as baffles to fluid flow, but they are not extensive and the reservoir acts as one unit.

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