scholarly journals Simulation of hydrocarbon generation and expulsion in the Northern North Sea and North West Shelf of Australia.

1998 ◽  
Vol 63 (1) ◽  
pp. 65-77
Author(s):  
Takeo Tateishi
Keyword(s):  
North Sea ◽  
Hydrocarbon Generation ◽  
North West ◽  
Northern North Sea

scholarly journals Coccolithophores on the north-west European shelf: calcification rates and environmental controls

2014 ◽  
Vol 11 (14) ◽  
pp. 3919-3940 ◽  
Author(s):  
A. J. Poulton ◽  
M. C. Stinchcombe ◽  
E. P. Achterberg ◽  
D. C. E. Bakker ◽  
C. Dumousseaud ◽  
...  
Keyword(s):  
North Sea ◽  
Growth Rates ◽  
Light Availability ◽  
Bay Of Biscay ◽  
Carbonate Chemistry ◽  
North West ◽  
The North ◽  
European Shelf ◽  
Northern North Sea ◽  
West European

Abstract. Coccolithophores are a key functional group in terms of the pelagic production of calcium carbonate (calcite), although their contribution to shelf sea biogeochemistry, and how this relates to environmental conditions, is poorly constrained. Measurements of calcite production (CP) and coccolithophore abundance were made on the north-west European shelf to examine trends in coccolithophore calcification along natural gradients of carbonate chemistry, macronutrient availability and plankton composition. Similar measurements were also made in three bioassay experiments where nutrient (nitrate, phosphate) and pCO2 levels were manipulated. Nanoflagellates (< 10 μm) dominated chlorophyll biomass and primary production (PP) at all but one sampling site, with CP ranging from 0.6 to 9.6 mmol C m−2 d−1. High CP and coccolithophore abundance occurred in a diatom bloom in fully mixed waters off Heligoland, but not in two distinct coccolithophore blooms in the central North Sea and Western English Channel. Coccolithophore abundance and CP showed no correlation with nutrient concentrations or ratios, while significant (p < 0.01) correlations between CP, cell-specific calcification (cell-CF) and irradiance in the water column highlighted how light availability exerts a strong control on pelagic CP. In the experimental bioassays, Emiliania-huxleyi-dominated coccolithophore communities in shelf waters (northern North Sea, Norwegian Trench) showed a strong response in terms of CP to combined nitrate and phosphate addition, mediated by changes in cell-CF and growth rates. In contrast, an offshore diverse coccolithophore community (Bay of Biscay) showed no response to nutrient addition, while light availability or mortality may have been more important in controlling this community. Sharp decreases in pH and a rough halving of calcite saturation states in the bioassay experiments led to decreased CP in the Bay of Biscay and northern North Sea, but not the Norwegian Trench. These decreases in CP were related to slowed growth rates in the bioassays at elevated pCO2 (750 μatm) relative to those in the ambient treatments. The combined results from our study highlight the variable coccolithophore responses to irradiance, nutrients and carbonate chemistry in north-west European shelf waters, which are mediated by changes in growth rates, cell-CF and species composition.

scholarly journals Coccolithophores on the north-west European shelf: calcification rates and environmental controls

2014 ◽  
Vol 11 (2) ◽  
pp. 2685-2733 ◽  
Author(s):  
A. J. Poulton ◽  
M. C. Stinchcombe ◽  
E. P. Achterberg ◽  
D. C. E. Bakker ◽  
C. Dumousseaud ◽  
...  
Keyword(s):  
North Sea ◽  
Bay Of Biscay ◽  
English Channel ◽  
Carbonate Chemistry ◽  
Growth Environment ◽  
North West ◽  
The North ◽  
European Shelf ◽  
Northern North Sea ◽  
West European

Abstract. Coccolithophores are a key functional group in terms of the pelagic production of calcium carbonate (calcite), although their contribution to shelf-sea biogeochemistry, and how this relates to environmental conditions, is poorly constrained. Measurements of calcite production (CP) and coccolithophore abundance were made on the north-west European shelf to examine trends in coccolithophore calcification along natural gradients of carbonate chemistry, macronutrient availability and plankton composition. Similar measurements were also made in three bioassay experiments where nutrient (nitrate, phosphate) and pCO2 levels were manipulated. Nanoflagellates (< 10 μm) dominated chlorophyll biomass and primary production (PP) at all but one sampling site, with CP ranging from 0.6–9.6 mmol C m−2d−1. Highest CP and coccolithophore cell abundance occurred in a diatom bloom in fully mixed waters off Helgoland, rather than in two distinct coccolithophore blooms in the central North Sea and Western English Channel. Estimates of coccolithophore contributions to total PP and nanoplankton PP were generally < 5%, apart from in a coccolithophore bloom at the Western English Channel Observatory (E1) where coccolithophores contributed up to 11% and at Helgoland where they contributed ~23% to nanoplankton PP. Variability in CP was influenced by cell numbers, species composition and cell-normalised calcification rates under both in situ conditions and in the experimental bioassays. Water column structure and light availability had a strong influence on cellular calcification, whereas nitrate (N) to phosphate (P) ratios influenced bulk CP. Coccolithophore communities in the northern North Sea and over the Norwegian Trench showed responses to N and P addition whereas oceanic communities in the Bay of Biscay showed no response. Sharp decreases in pH and a rough halving of calcite saturation states in the bioassay experiments led to decreased CP in the Bay of Biscay and Northern North Sea, but not over the Norwegian Trench. These variable relationships to nutrient availability and changes in carbonate chemistry highlight the complex response of coccolithophore physiology to growth environment.

Geo History, Thermal History and Hydrocarbon Generation History of the Northern North Sea Basin

1987 ◽  
Vol 5 (4) ◽  
pp. 315-355 ◽  
Author(s):  
Song Cao ◽  
Ian Lerche
Keyword(s):  
Fluid Flow ◽  
North Sea ◽  
Thermal History ◽  
Hydrocarbon Exploration ◽  
Geochemical Data ◽  
Hydrocarbon Generation ◽  
Similar Data ◽  
History Of ◽  
Northern North Sea

A one-dimensional, fluid flow/compaction model has been developed for petroleum explorationists to make quantitative studies of sedimentary basins. The following results can be obtained from the model: (1) basement subsidence (sediment load and tectonic effect); (2) structural evolution; (3) determination of erosion thickness of an unconformity; (4) changes of porosity, permeability, fluid flow rate and pore pressure with time and depth; (5) heat flow history; (6) temperature change with time and depth; (7) the value of thermal maturity indicators which change with time and depth; (8) hydrocarbon generation history including time and depth of peak hydrocarbon generation; and (9) prediction of possible directions of hydrocarbon migration and accumulation with time. The model is applicable to both frontier basins where only a few wells have been drilled and also to well-developed basins. The input data for the model are based mainly on commonly used geological and geochemical data from one well in a frontier basin or on similar data from many wells in a well-developed basin. Fifty-eight wells in the northern North Sea Basin have been used to reconstruct the geohistory, thermal history and hydrocarbon generation and migration history of the northern North Sea. The results accurately conformed to the well data, allowing determination of hydrocarbon generation amounts, migration times and accumulation sites, which are helpful for further hydrocarbon exploration in the northern North Sea Basin.

Depositional Environment Drive as Overpressure Generation: Study Case in “Gap” Field, North West Java Basin

2020 ◽  
Author(s):  
A., C. Prasetyo
Keyword(s):  
Clay Mineral ◽  
Depositional Environment ◽  
Mineral Content ◽  
Hydrocarbon Generation ◽  
Well Test ◽  
Burial History ◽  
The South ◽  
North West ◽  
The North ◽  
Geological Processes

Overpressure existence represents a geological hazard; therefore, an accurate pore pressure prediction is critical for well planning and drilling procedures, etc. Overpressure is a geological phenomenon usually generated by two mechanisms, loading (disequilibrium compaction) and unloading mechanisms (diagenesis and hydrocarbon generation) and they are all geological processes. This research was conducted based on analytical and descriptive methods integrated with well data including wireline log, laboratory test and well test data. This research was conducted based on quantitative estimate of pore pressures using the Eaton Method. The stages are determining shale intervals with GR logs, calculating vertical stress/overburden stress values, determining normal compaction trends, making cross plots of sonic logs against density logs, calculating geothermal gradients, analyzing hydrocarbon maturity, and calculating sedimentation rates with burial history. The research conducted an analysis method on the distribution of clay mineral composition to determine depositional environment and its relationship to overpressure. The wells include GAP-01, GAP-02, GAP-03, and GAP-04 which has an overpressure zone range at depth 8501-10988 ft. The pressure value within the 4 wells has a range between 4358-7451 Psi. Overpressure mechanism in the GAP field is caused by non-loading mechanism (clay mineral diagenesis and hydrocarbon maturation). Overpressure distribution is controlled by its stratigraphy. Therefore, it is possible overpressure is spread quite broadly, especially in the low morphology of the “GAP” Field. This relates to the delta depositional environment with thick shale. Based on clay minerals distribution, the northern part (GAP 02 & 03) has more clay mineral content compared to the south and this can be interpreted increasingly towards sea (low energy regime) and facies turned into pro-delta. Overpressure might be found shallower in the north than the south due to higher clay mineral content present to the north.

Hydrocarbon plays in the northern North Sea

1990 ◽  
Vol 50 (1) ◽  
pp. 441-470 ◽  
Author(s):  
R. M. Pegrum ◽  
A. M. Spencer
Keyword(s):  
North Sea ◽  
Northern North Sea
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