Indicators offshore

The half-life of radium 226 makes its abundance in the upper layers of ocean sediments, which settled within the past 10,000 years (Holocene epoch), convenient to measure. A comparison of 226Ra abundance to 228Ra in various ocean locations allows for determination of ocean current directional flow Because 228Ra is produced more strongly in shallow areas, and its lifetime is so much shorter, observation of radium 228 far from shore can indicate offshore currents that are otherwise difficult to measure. 

User experience of monitoring techniques in oil and gas production has been reviewed and indicates success and failure for the same methods by different operators. A survey of current monitoring practice in UK offshore fields has been published and other experience related to oil/gas production has be reported . A draft document has been prepared by CEA Task Group E2-5 providing guidelines for monitoring sea-water injection systems. 

The first reports of plastic in the North Atlantic indicated the presence of 50-12,000 particles/km in the Sargasso Sea in 1972 (52) and from 0-14.1 particles per m in coastal waters of southern New England (42), where the main source was river-borne effluents from plastic fabrication plants (44). Plastic objects discarded from boats and from recreational activities on beaches were the main sources of debris in Narragansett Bay, being deposited at a rate of 9.6 g m of beach front per month (53). During a detailed survey off the southeast coast of the United States (43, 54), fragments of plastic were present in about 70% of the samples collected from the waters of the continental shelf, the continental slope and the Gulf Stream between Florida and Cape Cod, 50% of those from the Caribbean Sea, and 60% of those from the Antilles Current. Since unprocessed plastic was more prevalent in continental shelf waters and fabricated objects were common offshore but rare near land, the authors surmised... 

The authors of this study divided their dataset into harbour and offshore sediments, assuming that the latter are contaminant-free, and used Li as the normalizing agent. All samples were compared to the regression equation based on the offshore sediments, which indicated considerable Zn contamination -with some samples >3 times background... 

Fig. 3. Biplots of log-ratio factor loading for Aegean Sea sediments. Upper plot, complete dataset lower plot, offshore samples. Percentages indicate variance accounted for by factor.

Subsea pipeline emergency isolation valves for offshore facilities are provided where a risk analysis indicated topside isolation may be considered vulnerable. They should be protected from ship impacts, anchor dragging, flammable liquid spills and heavy objects that may be dropped from the offshore facility. 

Areas of the North and South Atlantic, and North and South Pacific present continual extreme and hostile ambient conditions that make survival exposed to such conditions a very limited probability with adequate protection measures. In these locations the probability of survival is increased with the provision of a fixed safe refuge rather than the provision of an immediate means of escape. For offshore facilities historical evidence indicates that both helicopter and lifeboat mechanism may be unavailable in some catastrophic incidents. Remote onshore facilities may also experience severe winter conditions that also render this philosophy applicable. 

Firewater supply sources can be the city public water main, a dedicated storage tank and pumps, or the most convenient lake, river or if an offshore installation the open sea. Brackish or salt water supplies can be used if suitable corrosion protection measures are applied to the entire firewater system if it is planned to be used for an extended life (i.e., grater than five years). If a short life span of the facility is expected, short corrosion resistant materials may be used (i.e., carbon steel, galvanized steel, etc.), provided periodic testing indicates their integrity is still adequate and scale or corrosion particles do not affect operational efficiency. 

Iceland could also develop wind power with coastal or offshore facilities. A study indicated that 240 wind power plants could produce the electricity needed to replace fossil fuel from vehicles and fisheries. 

October 19,1988), in addition to biogenic dominance in ocean hydrates (Dillon and Max, 2000), with sporadic mixtures of biogenic and thermogenic gas in Alaska, Russia, offshore Canada, and the Gulf of Mexico. It is possible to have both means (in place generation and fast fluxes) of supplying biogenic gas, indicated by Kvenvolden et al. (1984) and Kvenvolden and Claypool (1985) at DSDP Site 570 in the Middle America Trench. 

Flow assurance engineers for a major energy company (Mehta et al., 2003) indicate that for a two year periods, one of their offshore gas flowlines operated well inside the hydrate formation region. The problem arose from increased water production (to >1000 BPD) over the field life, with limited methanol delivery. Their approach was to inject as much methanol as possible, in the knowledge that they were underinhibiting the system. Due to under-inhibition, there was a gradual increase in the pressure drop (A P) in the line over a period of about 2 weeks, indicating a hydrate build-up on the walls. 

Complicated biological systems (bioassays) at trace element concentration levels typical for offshore waters, are subject to serious danger of contamination. Without extreme precautions e.g. Carpenter and Lively (1980) and Fitzwater et al. (1982) found the toxic effect (inhibition of primary production) of contamination by the incubation bottles. Effects of adsorption to walls and particulate matter (sediment) should not be underestimated. Use of clean lab techniques and regular check of the trace element concentrations throughout the (biological) experiments is necessary to get an indication of the actual concentration and possible distribution of the different elements. Depending on the type of experiments it could be possible that other parametes should be known or even controlled pE, PO2, ionic strength, temperature, DOC etc. 

Fig. 1. Model depicting nitrogen flows in a kelp bed community. Primary production by macrophytes is partitioned into particulate (POM) and dissolved (DOM) components. Filter-feeders feed on detritus consisting of POM, bacteria and animal faeces. Recycling of nitrogen via the feedback loop provided by faeces is indicated by heavy lines. Fig. la) shows the model under downwelling conditions, when phytoplankton is imported with surface water from offshore. Fig. lb) shows the model under upwelling conditions when it is assumed that phytoplankton in the upwelling water is negligible and excess detritus is exported in surface water.

A nationwide comparison indicates that elevated levels of OCs were found in the samples collected from Java Island than Sumatra and Sulawesi Islands (Table 13.2 Fig. 13.1). In Belawan (North Sumatra), Hurun Bay (Lampung), and Maros (South Sulawesi) residue levels of OCs were low. Such a pattern is understandable because Java Island is the most populated and industrialized island with intense agricultural activities, and the results could reflect the usage status of OCs in this island. Levels of OCs are still low in remote areas of Sumatra offshore waters as exemplified by less contamination in tuna (Ueno et al., 2003b). 

Figure 18.3. Geographical distribution of PCBs, DDTs and PBDEs in Asian cetaceans. Black and white bars indicate coastal and offshore species, respectively.

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