Continental shelves

In recent years a new approach to contracting has evolved and Is gaining rapid acceptance In the United Kingdom Continental Shelf (UKCS). The concept has become known as partnering and can be seen as a progression of the incentive contract. Whilst the previously described contractual arrangements are restricted to a single well project... 

The fiscal system set by the host government determines the method by which the host nation claims its entitlement to income from the production and sale of hydrocarbons. The simplest fiscal system is the tax and royalty scheme, such as that applied to income from production in the UKCS (United Kingdom Continental Shelf). 

As shown in Table 8, U.S. distribution of oil and natural gas reserves is centered in Alaska, Cahfomia, Texas, Oklahoma, Louisiana, and the U.S. outer-continental shelf. Alaska reserves include both the Pmdhoe Bay deposits and the Cook Inlet fields. Cahfomia deposits include those in Santa Barbara, the Wilmington Eield, the Elk Hills Naval Petroleum Reserve No. 1 at Bakersfield, and other offshore oil deposits. The Yates Pield, Austin Chalk formation, and Permian Basin are among the producing sources of petroleum and natural gas in Texas. 

Deposits that can be recovered without having to use explosives or other primary energy sources to break up the material in place ate called unconsoHdated deposits. These may be found stratified or disseminated as sutficial or subsurface deposits on the continental shelf or in deep ocean basins. 

Continental Shelf. A variety of terms may be appHed to deposits in the continental shelf (conshelf) including beach, bank, alluvial, strand-line, heavy mineral, or placet. These contain mostly industrial materials, mineral sands, or precious metals (Table 1). 

Continental Shelf. Most consohdated mineral deposits found on the continental shelf are identical to those found on land and are only fortuitously submerged. Exceptions include those laid down in shallow marine seas or basins in earlier geochemical environments such as bedded ironstones, limestones, potash, and phosphorites. 

Fluid deposits are defined as those which can be recovered in fluid form by pumping, in solution, or as particles in a slurry. Petroleum products and Frasch process sulfur are special cases. At this time no vaUd distinction is made between resources on the continental shelf and in the deep oceans. However, deep seabed deposits of minerals which can be separated by differential solution are expected to be amenable to fluid mining methods in either environment. 

M. J. Cmickshank and C. L. Morgan, Synthesis andMnalysis of Existing Information KegardingEnvironmental Effects of Marine Mining, consulting report to Continental Shelf Associates for U.S. MMS Contract No. 14-35-0001-30588, U.S. Dept, of the Interior, Washington, D.C., 1992. 

To recover oil from the continental shelf of arctic Canada and Alaska, drilling and production platforms must be built some miles offshore, in roughly 40 m of water. This is not a great depth, and would present no new problems were it not that the sea freezes in winter to a depth of around 2 m. Wind blowing across the surface of the ice sheet causes it to move at speeds up to 1 m s pressing it against the structure. Ice is... 

Perkins, D. M. et al., 1980, Probabilistic Estimates of Maximum Seismic Horizontal Ground Motion on Rock in The Pacific Northwest and the Adjacent Outer Continental Shelf, U.S. Geological Survey No.80-471. 

Title 30, Oil and Gas and Sulfur Operations in the Outer Part 250 Continental Shelf... 

Performance of Pipework in the British Sector of the North Sea Offshore Oil and Natural Gas Failure rates based on 27 actual incidents from UK DOE reports Offshore oil. gas. and process fluid submarine pipelines within the UK Continental Shelf 109. 

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... 

Christensen J. P., Murray, J. W., Devol, A. H. and Codispoti, L. A. (1987). Denitrification in continental shelf sediments has major impact on oceanic nitrogen cycle. Glob. Biogeochem. Cycles 1,97-116. 

PCBs in cod, mussel and shrimp from Belgian continental shelf GC BCR CRM 349, PCBs in Cod liver oil Roose et al. 1998... 

Roose P, Cooreman K, Vyncke W (1998) PCBs in cod Gadus morhua), flounder (Platichthysflesus), blue mussel (Mytilus eduUs) and brown shrimp Crangon crangon) from the Belgian continental shelf relation to biological parameters and trend analysis. Chemosphere 37 2199-2210. 

Bugna GC, Chanton JP, Cable JE, Burnett WC, Cable PH (1996) The importance of ground water discharge to the methane budgets of near shore and continental shelf waters of the northeastern Gulf of Mexico. Geochim Cosmochim Acta 60 4735-4746... 

Moore WS (2000) Determining coastal mixing rates using radium isotopes. Cont Shelf Res 20 1995-2007 Moore WS, Shaw X J (1998) Chemical signals from submarine fluid advection onto the continental shelf J GeophysRes 103 21543-21552... 

Bacon MP, Belastock RA, Tecotzky M, Turekian KK, Spencer DW (1988) Lead-210 and polonium-210 in ocean water profiles of the continental shelf and slope south of New England. Cont Shelf Res 8 841-... 

McKee BA, DeMaster DJ, Nittrouer CA (1984) The use of Th-234/U-238 disequilibrium to examine the fate of particle-reactive species on the Yangtze continental shelf. Earth Planet Sci Lett 68 431-42 McKee BA, DeMaster DJ, Nittrouer CA (1986) Temporal variability in the portioning of thorium between dissolved and particulate phases on the Amazon shelf Implications for the scavenging of particle-reactive species. Cont Shelf Res 6 87-106... 

Figure 3. Distribution coefficient (Ka) versus particle concentration for Th. Note that, for typical open-ocean particle concentrations, Th is about lO times more likely to adhere to a mass of particles than to remain in the same mass of water. This tendency to be found in the particulate phase decreases with particle concentration, probably due to the presence of a larger number of colloids which, because they pass through filters, appear to be in the dissolved phase (Honeyman et al. 1988). Grey squares are " Th data from Honeyman et al. (1988) gray triangles are " Th data from the continental shelf from McKee et al. (1986) and black circles are a compilation of open ocean °Th data from Henderson et al. (1999a).

Anderson RF, Bopp RF, Buesseler KO, Biscaye PE (1988) Mixing of particles and organic constituents in sediments from the continental shelf and slope off Cape Cod SEEP-1 results. Cont Shelf Res 8(5-... 

Li YH, Mathieu G, Biscaye P, Simpson HJ (1977) The flux of Ra from estuarine and continental shelf sediments. Earth Planet Sci Lett 37 237-241... 

Kineke GC, Sternberg RW, Trowbridge JH, Geyer WR (1996) Fluid-mud processes on the Amazon continental shelf. Cont Shelf Res 16 667-696... 

Smoak JM, DeMaster DJ, Kuehl SA, Pope RH, McKee BA (1996) The behavior of particle-reactive tracers in a high turbidity environment " Th and °Pb on the Amazon continental shelf Geochim Cosmochim Acta 60 2123-2137... 

Figure 2 Quantities of debris per trawling tow (30 min) collected on the continental shelf and adjacent canyon of the Gulf of Lyons (Reprinted from Mar. Pollut. Bull, 30, 713. 1995, with permission from Elsevier Science)...

---