A summary of the geology and oil habitat of the Eastern Flank Hydrocarbon Province of South Oman     

Aley Al-Marjeby  David Nash 《Marine and Petroleum Geology》1986,3(4)

The Eastern Flank Hydrocarbon Province borders the southeastern edge of the South Oman Salt Basin in the southern part of Oman. An intensive exploration programme by PDO over the past seven years has led to the discovery of almost 2 × 10⁹ m³ of oil with current production of some 15000 m³/d from six fields.In stark contrast to other oil habitats of the Arabian Peninsula, the main play involves rock units and geological events ranging in age from Late Precambrian to Quaternary Times, while trap development and charging are closely related to syn-tectonic salt dissolution.The principal reservoirs and seals are poorly consolidated, Palaeozoic clastics which drape, due to salt dissolution, over residual ‘cores’ principally composed of either Lower Palaeozoic sandstones (Haima Group), or Late Proterozoic carbonates (Huqf Group), or some combination of these. Oils have been geochemically correlated with algal source rocks of the Huqf Eastern Flank. Structures are considered to have been ‘charged’ from Late Mesozoic times onwards in conjunction with progressive subsurface salt removal and the onset of maturation of local source rocks. The effectiveness of ‘charging’ along the retreating salt edge is indicated by the small percentage of dry wells.Major oil zones are found in both anticlinal and truncation traps which are commonly developed around sandstone (Haima Group) cores. Oils show a wide range of characteristics but are typically heavy, early expulsion crudes, high sulphur with little associated gas. Bacterial transformation is not uncommon.Producing reservoirs mainly occur at relatively shallow depths (600–1200 m). Primary recovery factors of around 7% reflect the high density and viscosity of the Eastern Flank crudes and have initiated interest in Enhanced Oil Recovery (EOR) techniques. Two such pilot projects, involving steam and polymer flooding, are due to commence in 1984 and, if successful, will substantially increase the reserve base of these fields.  相似文献   

On the sulphur chemistry of a super-anoxic fjord, Framvaren, South Norway     

Leif G. Anderson  David Dyrssen  Per O.J. Hall 《Marine Chemistry》1988,23(3-4)

The concentrations of total carbonate (C_t), sulphate, sulphide, thiols and oxygen, the ratio between the stable sulphur isotopes ³⁴S and ³²S in sulphate and sulphide, and the density (used to calculate salinity) were determined on samples from the water column of Framvaren, a superanoxic fjord in southern Norway. From a depth of 18m (the oxic-anoxic boundary) the initial sulphate concentration, ([SO₄]_init), as calculated from salinity, is significantly higher than the sum of the measured sulphur species. This is attributed to a loss of sulphur from the water column. The amount of total carbonate produced, corrected for the initial concentration (C_t - 2.4 Sal/35) is found to be proportional to the amount of sulphate consumed, ([SO₄]_init - [SO₄]), according to the following relation C_t- 2.4 Sal/35 = 1.84 ([SO₄]_init - [SO₄]). Isotopic fractionation caused by bacterial sulphate reduction in the anoxic part of the water column produces sulphide with a δ³⁴S 40‰ lower than the δ³⁴S for sulphate at corresponding depths. The isotopic fractionation also results in δ³⁴S value for the remaining sulphate at depths below 80 m being considerably higher than the mean value for ocean water, which is close to + 20‰. The δ³⁴S values for sulphate at depths between 10 and 50 m were lower than + 20‰ which indicates oxidation of sulphide, which follows upon diffusion of sulphide from deeper parts of the water column and inflow of oxygenated seawater over the sill into the anoxic water of the fjord. A conclusive scenario of the Framvaren sulphur chemistry is presented.  相似文献   

Chalk shore platform erosion in the vicinity of sea defence structures and the impact of construction methods     

Uwe Dornbusch  David A. Robinson  Rendel B.G. Williams  Cherith A. Moses 《Coastal Engineering》2007

Erosion of the intertidal chalk platform in the vicinity of groynes and seawalls is evident to the naked eye along many stretches of the engineered coastline of southeast England, leading to undermining and eventually failure of these structures. However, quantification of the magnitude and spatial extent of the erosion has been difficult to date because of a lack of data about the past elevation of the platform. The application of softcopy photogrammetry makes it possible to recreate past platform elevations from historic air photographs and to compare these with elevations from modern air photographs. Coastal sea defence structures have been installed along the chalk coast east of Brighton at various dates over the past 70 years. During this period, the construction methods have changed from predominantly manual labour to a reliance on heavy machines. The analysis of erosion patterns around structures built since the 1970s using heavy machinery show that surface lowering is 4 to 25 times greater in the vicinity of these structures than across the platform as a whole. In contrast, there is no similar pattern of increased erosion around structures built using predominantly manual labour in the 1930s. A four fold increase in average surface lowering is found also along a vehicle trackway that crosses the mid platform. Depressions developed by enhanced lowering in the front of seawalls generate their own dynamic of increased erosion by trapping pebbles and cobbles that enhance the abrasion of the chalk through bedload transport under standing waves in front of the walls.  相似文献   

Understanding mackerel migration off Scotland: Tracking with echosounders and commercial data, and including environmental correlates and behaviour     

Walsh  Martin; Reid  David G.; Turrell  William R. 《ICES Journal of Marine Science》1995,52(6):925-939

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Voracious planktonic hydroids: unexpected predatory impact on a coastal marine ecosystem     

Laurence P. Madin  Stephen M. Bollens  Erich Horgan  Mari Butler  Jeffrey Runge  Barbara K. Sullivan  Grace Klein-Macphee  Edward Durbin  Ann G. Durbin  Donna Van Keuren  Stphane Plourde  Ann Bucklin  M. Elizabeth Clarke 《Deep Sea Research Part II: Topical Studies in Oceanography》1996,43(7-8)

Hydroids are typically attached, benthic cnidarians that feed on a variety of small prey. During sampling on Georges Bank in spring 1994, we found huge numbers of hydroids suspended in the plankton. They fed on young stages of copepods that are an important prey for fish, as well as on young fish themselves. Two independent methods were used to estimate feeding rates of the hydroids; both indicate that the hydroids are capable of consuming from 50% to over 100% of the daily production of young copepods. These results suggest that hydroids can have a profound effect on the population dynamics of zooplankton and young fish on Georges Bank.  相似文献   

Properties of structure and function of cadmium-binding proteins/peptides from Euglena gracilis     

C Daniel Weber  Frank Shaw III  David H Petering 《Marine environmental research》1988,24(1-4)

Euglena gracilis makes two small Cd-binding proteins/peptides (Cd-BP I and Cd-BP II) in response to exposure to Cd²⁺. These proteins migrate slower than mammalian Cd-metallothionein (Cd-Mt) through Sephadex G-75, but like Cd-Mt also contain Zn and are separated into two species when chromatographed over a DEAE column. Both BPs are much less stable than Cd-Mt under acidic conditions. One source of this instability is that at least Cd-BP II contains acid-labile sulfide co-ordinated to the metals. It has been quantitated in Cd-BP II and shown to have a value of 1·25 ± 0·10 S²⁻/Cd. The reactivity of the Cd-binding sites in ligand substitution and thioldisulfide exchange reactions has been assessed. The reactions of Cd-BP I and II with pyridylazoresorcinol (PAR) were slow and displayed complex kinetic behavior. Similarly, both Cd-BPs react slowly and with complicated kinetics with 5,5′-dithiobis-(2-nitrobenzoate).  相似文献   

The vertical distribution of zooplankton in the western Irish Sea     

Sherard Scrope-Howe  David A. Jones 《Estuarine, Coastal and Shelf Science》1986,22(6)

Zooplankton diel vertical migration is evident on the mixed isothermal side of the western Irish Sea frontal system but is often influenced by large tides and persistent geostrophic currents. On the stratified side of the front, temperature acts as a controlling factor with most of the zooplankton occurring above the thermocline and carrying out pronounced vertical migration when chlorophyll a levels are low and diffuse. At higher chlorophyll levels, when discrete chlorophyll a maxima form, zooplankton vertical movement may be greatly modified with a large number of species and stages concentrating within these maxima at all times of the diel light cycle.  相似文献   

Sub-lethal effects of metal exposure: physiological and behavioural responses of the estuarine bivalve Macoma balthica     

Duquesne S  Liess M  Bird DJ 《Marine environmental research》2004,58(2-5):245-250

Variation in glycogen concentration, condition index (CI) and filtration activity were measured in the bivalve Macoma balthica buried in sediment and experimentally exposed to cadmium (Cd). The stress due to elevated but sub-lethal concentrations (300 ppb Cd) affected the overall fitness of the organism as all parameters monitored responded significantly. Lower concentrations tested (10, 30 and 100 ppb) only induced a significant decrease in filtration activity, which may play a protective role, enabling the organism to slow down its metabolic activity and preserving the integrity of its reserves (reflected by stable CI and glycogen levels). Hence, the various endpoints selected show different thresholds. Our results also demonstrate that under high exposure, small individuals loose proportionally more glycogen per unit of weight than larger ones, thus confirming the higher sensitivity of small individuals to metal contamination. Furthermore, exposure to intermediate concentration (30 ppb) seems to be beneficial to the small individuals as indicated by their high CI values compared to the control. These results showed thus that non-sigmoidal concentration-response relationship and sizes of individuals should be considered in monitoring programmes and risk assessment.  相似文献   

Determination of technical efficiency of fisheries by stochastic frontier models: a case on the Gulf of Cadiz (Spain)     

Garcia del Hoyo  Juan Jose; Castilla Espino  David; Jimenez Toribio  Ramon 《ICES Journal of Marine Science》2004,61(3):416-421

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An aromatase inhibitor and tamoxifen decrease plasma levels of o,p'-DDT and its metabolites in Nile tilapia (Oreochromis niloticus)     

Leaños-Castañeda O  Gold-Bouchot G  Van Der Kraak G  Lister A  Ceja-Moreno V  Simá-Alvarez R 《Marine environmental research》2004,58(2-5):337-342

The objective of this study was to determine if tamoxifen or an aromatase inhibitor (4-hydroxyandrostenedione; 4-OHA) affected plasma concentrations of o,p' -DDT and its metabolites, o,p'-DDD and o,p'-DDE, in mature tilapia. Male and female tilapia were injected 6 times intraperitoneally with o,p'-DDT (40 mg/kg) alone or in combination with 4-OHA (2 mg/kg) over a 12 day period. An additional group of male fish was injected with tamoxifen (5 mg/kg) plus o,p'-DDT. At the end of the treatment period, plasma samples were extracted and analyzed by GC/ECD. Females injected only with o,p'-DDT had significantly higher levels of o,p'-DDT compared with males. Interestingly, females and males treated concomitantly with o,p'-DDT and 4-OHA or tamoxifen had significantly lower concentrations of plasma o,p'-DDT (about 50%) compared with fish treated with only o,p'-DDT. These initial results suggest that an interaction between endocrine-active compounds occurs in vivo in tilapia and may involve alterations in metabolism of o,p'-DDT.  相似文献