Sedimentology and reservoir potential of a ‘marginal facies’ limestone from the Cretaceous of the North Sea

The lower Cretaceous section of UK North Sea well 3/16-1, on the eastern flank of the Shetland Platform, drilled by Sovereign Oil & Gas plc, is dominated by marine ‘shelf-type’ limestones with a very low argillaceous content. In this respect it differs both from the typical open-sea coccolith-rich Chalk and from the argillaceous Cretaceous of the Viking Graben (the Cromer Knoll and Shetland Groups). Diagenesis has resulted in crystal overgrowths, corrosion, and development of very fine to coarsely crystalline void filling calcite. Cavities, of stromatactis type and the result of shell dissolution, are filled with radiaxial fibrous calcite. Porosity is mostly intercrystal with possible contributions from fractures and vugs.Hydrocarbon staining is confined to patches of void-filling calcite and partially cemented fractures. No oil staining was observed in the carbonate matrix. It therefore appears that oil migrated through the rock via fractures but was unable to penetrate the main fabric of the rock.The lithological and petrophysical characteristics of the interval are similar to the Chalk Group of Norwegian well 1/3-1. The thickness is considerably less in 3/16-1, probably as a result of deposition on a topographic high such as existed along the margins of the Viking Graben and the East Shetland Platform during the Cretaceous.     

Diagenetic evolution of the upper Cretaceous limestone and sandstone exhumed reservoirs in the western Basque–Cantabrian Basin,North Spain

The Basque–Cantabrian Basin (NE Spain) has been considered one of the most interesting areas for hydrocarbon exploration in the Iberian Peninsula since the 60th to 70th of last century. This basin is characterized by the presence of numerous outcrops of tar sands closely associated with fractures and Triassic diapirs. The aims of this work is to establish the diagenetic evolution of the Upper Cretaceous reservoir rocks with special emphasis in the emplacement of oil and their impact on reservoir quality. The studied rocks are constituted of carbonates and sandstones that contain massive quantities of bitumen filling vugs and fractures.Petrographic results indicate that the carbonate rocks from Maestu outcrops are bioclastic grainstones and wackestones, whereas the tar sandstones from Atauri and Loza outcrops are dominated by quartzarenites and subordinated subarkoses. The paragenetic sequence of the main diagenetic phases and processes include, pyrite, bladed and drusy calcite cement, calcite overgrowths, silicification of bioclasts and microcrystalline rhombic dolomite cement, and first stage of oil emplacement, blocky calcite cement, coarse crystalline calcite cement, calcitized dolomite, calcite veins, saddle dolomite and stylolites filled by the second phase of oil entrance. Together with the above mentioned diagenetic alterations, the arenites are affected by early kaolinitization of feldspars and the scarce formation of clay rim and epimatrix of illite. All sandstones and dolomitized carbonate rocks show high intercrystalline and intergranular porosity which is full by biodegraded hydrocarbons (solid bitumen). The biodegradation affects alkanes, isoprenoids and partially hopanes and steranes saturated hydrocarbons. Aromatics hydrocarbons, like naphthalenes, phenanthrenes, dibenzothiophenes and triaromatics are also affected by biodegradation. Results indicate that the first HC emplacement corresponds to early stage of calcite and dolomite cementation, and the second and more important emplacement is related to fracturation processes resulting in the formation of excellent reservoirs.     

Aims and Scope

China Ocean Engineering takes as its prime function the integration of new research concepts, equipment, technology, materials and structures and other scientific advances within the field of ocean engineering, with particular reference to developments in China. Tne Journal is concerned with all engineering aspects involved in the exploration and utilization of ocean resources, such as offshore engineering, coastal engineering, dive and salvage, utilization of marine energy, resourees and underwater engineering.     

Aims and Scope

China Ocean Engineering takes as its prime function the integration of new research concepts,equipment,technology,materials and structures and other scientific advances within the field of ocean engineering,with particular reference to developments in Chi…     

Aims and Scope

正Being an international journal,China Ocean Engineering takes as its prime function the integration of new research concepts,equipment,technology,materials and structures and other scientific advances within the field of estuarial,coastal,offshore,and deepwater engineering with particular reference to developments.The Journal is concerned with all engineering aspects involved in the exploration and utilization of ocean resources.Topics regularly covered include research,design and     

Aims and Scope

China Ocean Engineering takes as its prime function the integration of new research concepts,equipment,technology,materials and structures and other scientific advances within the field of ocean engineering, with particular reference to developments in China.     

Aims and Scope

Being an intcrnational journal,China Ocean Engineering takes as its prime function the integration of new researchconcepts,equipment,technology,materials and structures and other scientific advances within the field of     

Aims and Scope

正China Ocean Engineering takes as its prime function the integration of new research concepts, equipment, technology, materials and structures and other scientific advances within the field of ocean engineering, with particular reference to     

Aims and Scope

China Ocean Engineering takes as its prime function the integration of new research concepts,equipment,technology,materials and structures and other scientific advances within the field of ocean engineering,with particular reference to developments in Chi     

Aims and Scope

由中国海洋工程学会主办,南京水利科学研究院承办,大连理工大学海岸和近海工程国家重点实验室协办的第十二届中国海岸工程学术讨论会于2005年10月16-19日在云南省昆明市召开。邱大洪名誉理事长、谢世楞、严以新、李润培、李京武、左其华等副理事长出席了会议。全国从事海洋工程研究包括高等院校、设计、科研、建设和施工等39个部门的近百名代表参加了学术交流。17日上午,严以新副理事长主持了开幕式,并致开幕词;窦希萍副秘书长作了学会近两年来的工作总结。严以新和左其华教授分别主持了大会主题报告。中国科学院院士邱大洪教授论述了沿海海…     

Aims and Scope

China Ocean Engineering takes as its prime function the integration of new research concepts, equipment, technology, materials and structures and other scientific advances within the field of ocean engineering, with particular reference to developments in     

Aims and Scope

China Ocean Engineering takes as its prime function the integration of new research concepts, equipment, technology, materials and structures and other scientific advances within the field of ocean engineering, with particular reference to developments in China. The Journal is concerned with all engineering aspects involved in the exploration and utilization of ocean resources, such as offshore engineering, coastal engineering, dive and salvage, utilization of marine energy resources and underwater engineering.[第一段]     

Aims and Scope

China Ocean Engineering takes as its prime function the integration of new research concepts, equipment,technology, materials and structures and other scientific advances within the field of ocean engineering, with particular reference to developments in China.     

Aims and Scope

China Ocean Engineering takes as its prime function the integration of new research concepts,equipment,tech-nology,materials and structures and other scientific advances within the field of ocean engineering,with particular refer-ence to developments in China.     

Seals and fisheries in South Africa — competition and conflict

There are two types of interactions between seals and commercial fisheries in South Africa: biological (potential competition for shared resources between the two "predators") and operational (conflicts during fishing operations). Using data for the 1980s, a comparison is made of relative consumption by different predators in South African waters. Seals and fisheries are not the major consumers in the system, but they do take comparable amounts. This has resulted in calls for a reduction in the seal population, but to date, no studies have shown that reducing seal predation of commercial species will make more fish available for the fisheries. Most fisheries are subject to some form of operational interaction with seals. These interactions include consumption of catches (operational consumption), disturbance of fishing operations (operational disturbance) and damage to fishing gear (operational gear damage); they vary in degree of severity, both seasonally and regionally. Estimates of the consumption by seals from fishing operations in South Africa show it to be a minimal percentage of fishery catches and a small proportion of the total predation by seals. Preliminary calculations of overall economic losses resulting from seal interference show this to be small in comparison with the wholesale value of the catches. Seals die as a result of fishing operations, and estimates of the potential mortality through entanglement, drowning and deliberate killing indicate this mortality to be of a magnitude that should be monitored.     

Coral reef ecological pump for gathering and retaining nutrients and exporting carbon: a review and perspectives

How coral reefs with high productivity and biodiversity can flourish in oligotrophic tropical oceans has inspired substantial research on coral reef ecosystems. Increasing evidence shows that similar to water in an oasis in the desert, there are stable nutrient supplies to coral reefs in oligotrophic oceans. Here, with emphasis on the fluxes of organic matter, we summarize at the ecosystem level(1) the multiple input pathways of external nutrients,(2) the storage of nutrients in reef organisms,(...     

Repair and revitalisation of Australia׳s tropical estuaries and coastal wetlands: Opportunities and constraints for the reinstatement of lost function and productivity

Tropical fisheries are in decline around world as a result of diverse anthropogenic threats. These threats are intimately linked to biodiversity and conservation values because of the heavy dependence of both fisheries and high value marine and coastal wetlands on coastal ecosystem health. Consequently, if the widespread degradation of coastal ecosystems can be halted and remediated, there are substantial benefits to fisheries output, ecosystem resilience, food security, livelihoods, recreation and the protection of ecological assets of national and global significance. The extent, intactness and quality of Australia׳s tropical coastal ecosystems has declined markedly since European settlement, due to the cumulative impact of many small encroachments and local barrier construction on the extent and productivity of coastal wetlands, mangroves and seagrass meadows. Additionally, coastal ecosystem dependent biota has been excluded from large areas of critical habitats. Despite these changes, coastal fisheries show no clear declines that could not be explained by changes in effort. This lack of detectable decline is probably partly attributable to the short history of available fisheries catch data. However, it is also likely that it reflects the offsetting of lost natural productivity by greatly increased anthropogenic nutrient loads; a substantial problem as governments are committed to large scale, long term efforts to reduce discharges of nutrients to coastal waters. This possibility underlines the importance of rejuvenating lost coastal productivity. Evaluation of past remediation efforts show that documented success is rare, due to a complex of factors including ineffective prioritisation, a lack of necessary knowledge and resources, and inefficient monitoring and evaluation. Past experiences from Australia׳s tropics and around the world, together with current ecological understanding, suggests some generally desirable characteristics to enhance the likelihood of successful remediation and repair actions.     

Effect of body size and body mass on δC and δN in coastal fishes and cephalopods

Carbon and nitrogen isotopes have been widely used in the investigation of trophic relations, energy pathways, trophic levels and migrations, under the assumption that δ¹³C is independent of body size and that variation in δ¹⁵N occurs exclusively due to ontogenetic changes in diet and not body size increase per se. However, several studies have shown that these assumptions are uncertain. Data from food-webs containing an important number of species lack theoretical support on these assumptions because very few species have been tested for δ¹³C and δ¹⁵N variation in captivity. However, if sampling comprises a wide range of body sizes from various species, the variation of δ¹³C and δ¹⁵N with body size can be investigated. While correlation between body size and δ¹³C and δ¹⁵N can be due to ontogenetic diet shifts, stability in such values throughout the size spectrum can be considered an indication that δ¹³C and δ¹⁵N in muscle tissues of such species is independent of body size within that size range, and thus the basic assumptions can be applied in the interpretation of such food webs. The present study investigated the variation in muscle δ¹³C and δ¹⁵N with body size and body mass of coastal fishes and cephalopods. It was concluded that muscle δ¹³C and δ¹⁵N did not vary with body size or mass for all bony fishes with only one exception, the dragonet Callionymus lyra. Muscle δ¹³C and δ¹⁵N also did not vary with body size or mass in cartilaginous fishes and cephalopods, meaning that body size/mass per se have no effect on δ¹³C or δ¹⁵N, for most species analysed and within the size ranges sampled. The assumption that δ¹³C is independent of body size and that variation in δ¹⁵N is not affected by body size increase per se was upheld for most organisms and can be applied to the coastal food web studied taking into account that C. lyra is an exception.