Seawater Flooding Research Articles

Sea ice algae in the White and Barents seas: composition and origin

To examine algae populations, three expeditions (in March 2001, April 2002 and February 2003) were conducted in the Guba Chupa (Chupa Estuary; north-western White Sea), and one cruise was carried out in the open part of the White Sea in April 2003 and in the northern part of the Barents Sea in July 2001. Sea ice algae and phytoplankton composition and abundance and the content of sediment traps under the land-fast ice in the White Sea and annual and multi-year pack ice in the Barents Sea were investigated. The community in land-fast sea ice was dominated by pennate diatoms and its composition was more closely related to that of the underlying sediments than was the community of the pack ice, which was dominated by flagellates, dinoflagellates and centric diatoms. Algae were far more abundant in land-fast ice: motile benthic and ice-benthic species found favourable conditions in the ice. The pack ice community was more closely related to that of the surrounding water. It originated from plankton incorporation during sea ice formation and during seawater flood events. An additional source for ice colonization may be multi-year ice. Algae may be released from the ice during brine drainage or sea ice melting. Many sea ice algae developed spores before the ice melt. These algae were observed in the above-bottom sediment traps all year around. Three possible fates of ice algae can be distinguished: 1) suspension in the water column, 2) sinking to the bottom and 3) ingestion by herbivores in the ice, at the ice-water interface or in the water column.

Sea ice algae in the White and Barents seas: composition and origin

To examine algae populations, three expeditions (in March 2001, April 2002 and February 2003) were conducted in the Guba Chupa (Chupa Estuary; north-western White Sea), and one cruise was carried out in the open part of the White Sea in April 2003 and in the northern part of the Barents Sea in July 2001. Sea ice algae and phytoplankton composition and abundance and the content of sediment traps under the land-fast ice in the White Sea and annual and multi-year pack ice in the Barents Sea were investigated. The community in land-fast sea ice was dominated by pennate diatoms and its composition was more closely related to that of the underlying sediments than was the community of the pack ice, which was dominated by flagellates, dinoflagellates and centric diatoms. Algae were far more abundant in land-fast ice: motile benthic and ice-benthic species found favourable conditions in the ice. The pack ice community was more closely related to that of the surrounding water. It originated from plankton incorporation during sea ice formation and during seawater flood events. An additional source for ice colonization may be multi-year ice. Algae may be released from the ice during brine drainage or sea ice melting. Many sea ice algae developed spores before the ice melt. These algae were observed in the above-bottom sediment traps all year around. Three possible fates of ice algae can be distinguished: 1) suspension in the water column, 2) sinking to the bottom and 3) ingestion by herbivores in the ice, at the ice-water interface or in the water column.

A deterministic/stochastic model to predict the variation in bulk modulus of chalk

Ekofisk, located 200 km west of the Norwegian coast, is one of the main oilfields in the North Sea. Since the early 1980s severe compaction of chalk reservoir layers has been observed as a consequence of reservoir depletion during oil production. Subsequently, this compaction has been amplified by assisted oil recovery using seawater flooding. The development of our understanding of the inherent mechanisms of this phenomenon has been the objective of extensive experimental investigations in the last two decades. Owing to the very high cost of cored material from the reservoir, experiments are usually performed on chalk samples from an outcrop in Belgium lying at the same stratigraphic level as the Ekofisk reservoir chalks. However, even at the laboratory sample scale, experimental variability of material response is observed. From a theoretical and numerical point of view, the determination of the mechanical properties of the material is of utmost importance for accurate modelling at both sample scale (laboratory tests) and reservoir scale. The aim of this paper is to introduce a stochastic approach within a deterministic constitutive model of chalk to enable the influence of material heterogeneity to be included in analyses for the range of observed mechanical responses. In modelling the random distribution of material parameters, the time-consuming Monte Carlo simulation method is replaced by a more efficient stochastic modelling technique. The results are given in the form of statistical parameters for the experimental laboratory test responses. The parameters of the distribution law (mean value, range of variation, spatial correlation structure) are fitted to reproduce the range of experimental responses observed at sample scale. Interest is focused on the variability of the chalk bulk modulus, as observed during isotropic compression tests. The proposed methodology provides a satisfactory explanation for the variability of response observed at the sample scale. The potential for extending the proposed approach to reservoir scale is briefly discussed.

A deterministic/stochastic model to predict the variation in bulk modulus of chalk

Ekofisk, located 200 km west of the Norwegian coast, is one of the main oilfields in the North Sea. Since the early 1980s severe compaction of chalk reservoir layers has been observed as a consequence of reservoir depletion during oil production. Subsequently, this compaction has been amplified by assisted oil recovery using seawater flooding. The development of our understanding of the inherent mechanisms of this phenomenon has been the objective of extensive experimental investigations in the last two decades. Owing to the very high cost of cored material from the reservoir, experiments are usually performed on chalk samples from an outcrop in Belgium lying at the same stratigraphic level as the Ekofisk reservoir chalks. However, even at the laboratory sample scale, experimental variability of material response is observed. From a theoretical and numerical point of view, the determination of the mechanical properties of the material is of utmost importance for accurate modelling at both sample scale (laboratory tests) and reservoir scale. The aim of this paper is to introduce a stochastic approach within a deterministic constitutive model of chalk to enable the influence of material heterogeneity to be included in analyses for the range of observed mechanical responses. In modelling the random distribution of material parameters, the time-consuming Monte Carlo simulation method is replaced by a more efficient stochastic modelling technique. The results are given in the form of statistical parameters for the experimental laboratory test responses. The parameters of the distribution law (mean value, range of variation, spatial correlation structure) are fitted to reproduce the range of experimental responses observed at sample scale. Interest is focused on the variability of the chalk bulk modulus, as observed during isotropic compression tests. The proposed methodology provides a satisfactory explanation for the variability of response observed at the sample scale. The potential for extending the proposed approach to reservoir scale is briefly discussed.

Agroforestry and its application in amelioration of saline soils in eastern China coastal region

Some environmental problems, especially soil salinity hinder the regional sustainable development of eastern China coastal region. Salinity mainly comes from tide weave, seawater flooding and seawater intrusion. Over exploitation of groundwater, which is the result of unfitful land use systems, leads to seawater intrusion and salt concentration increase. Agroforestry systems can enrich soil fertility and prevent soil salinization, furthermore help maintain biodiversity and enhance productivity. For the intergrated multiple ecosystems the most critical issue is to select optimum tree species and rationally arrange these plants. The basics of this multiple ecosystem is that different plants will occupy variable ecological niches within an area, both in space and in soil depth. Shelterbelts and trees intercropping with agricultural crops are major types of the multiple ecosystem. Shelterbelts can reduce wind speed and consequently lessen evaporation and erosion of the soil, increase pasture growth by up to 60% on exposed sites, increase crop yields by up to 25%. Besides intercropping with jujube, other agroforestry multiple ecosystem such as forestry plus agriculture, forestry plus agriculture plus fishery, and forestry plus animal husbandry are the most appropriate ways to utilise land resource in this region.

선회중 전복한 저건현 내항 탱커의 복원성에 관한 연구 (2) -갑판상 해수 침입이 경사 모멘트에 미치는 영향에 대한 실험적 조사 -

내항 탱커가 비교적 정온한 해역에서 타선을 피하기 위해 대각도 조타론 행한 결과, 선회 중에 전복하는 사고가 발생하였다. 저자들은 전 논문에서 비중량이 큰 액체화물의 자유표면영향에 의한 중심상승과 전진 항해 중에 발생하는 선체 침하와 이로 인하여 생기는 선체 트림의 변화 때문에 발생하는 복원력 감소를 고려하여 사고선박의 복원력 곡선을 계산하였다. 본 논문에서는 먼저 전복사고를 당한 선박의 모형선을 제작하여 자항 선회실험을 실시하고 전복선박의 정상 선회시의 선회반경, 편류각 및 선속을 계측한다. 그리고 자항 선회실험을 통하여 얻은 선회반경, 선속 및 횡 편류각을 기초로 하여 각 경사각에 따른 측 압력과 경사 모멘트에 관한 실험을 실시하고, 갑판상 해수 침입이 측 압력과 경사 모멘트에 미치는 영향에 대해서 파악한다. 마지막으로 선회시 해수 침입으로 인해 발생하는 외측 경사 모멘트와 측압 중심의 변화론 조사함으로써 전복사고가 발생한 저건현 내항 탱커의 복원성에 대하여 검토를 하였다. A coastwise chemical tanker sailing at full speed has capsized during turning in calm water. In the previous paper, we investigated the reasons of the accident by demonstrating the proper correction for the free surface effect of the liquid cargo and the bow-sinkage effect. In this paper, we also carry out model experiments of a transverse pressure under the seawater and an outward heel moment according to the heel angle and rudder angle, on the basis of radius of turning circle, ship's speed and drift angle of model ship occurring in turning. It is also shown that the flooding of seawater onto the deck occurring in turning generated a significant outward heel moment and increased the vertical distance between the center of gravity of the ship and the center of lateral water drag.

Pleistocene cyanobacterial mounds in the Perachora Peninsula, Gulf of Corinth, Greece: structure and applications to interpreting sea-level history and terrace sequences in an unstable tectonic setting

Large Pleistocene cyanobacterial mounds in the Perachora Peninsula, Gulf of Corinth, Greece, occur on a cut terrace and are interpreted to have formed in freshwaters on the basis of the principal constructing element, a freshwater cyanobacterium Rivularia haematites [Richter et al. (1979) Neues Jahrb. Geol. Paläontol. 159, 14–40], which pre-dates all other biota in and on the mounds. However, because of corals dated at ca. 125 ka in marine debris engulfing the mounds, the cut terrace has also been considered to be the erosional component of the Tyrrhenian Stage 5 highstand, an episode when the Gulf of Corinth was flooded by marine water from the Mediterranean Sea via the Rio Strait. This contradiction is addressed by consideration of mound ecology. Mounds are up to 10 m high, and several tens of metres wide, with simple dome to bulbous morphology, commonly coalesced with neighbouring mounds. Mounds consist of accreted layers of a branched structure of R. haematites, and encrusted by coralline alga Lithophyllum pustulatum, which can tolerate brackish water. No examples of the alga encrusted by Rivularia were found. The remaining space is filled with clotted microbial structure, and layers of micrite containing peloids, shell fragments and planktonic foraminifera. The mounds formed submerged in water, indicated by their accreted structure and rounded morphology. The terrace and mounds are bounded by steeply dipping coastal faults, with several hundred metres of water depth on neighbouring subsided hangingwall blocks. Thus the mound field grew on a triangular promontory protruding into the eastern end of the gulf, surrounded on two sides by deep water. The mounds are here interpreted to have grown when the Gulf of Corinth was a fresh to brackish lake, when Mediterranean sea level was below the contemporaneous depth of the threshold at the Rio Strait. Therefore the cut terrace on which the mounds occur cannot be the Tyrrhenian highstand. Relative sea-level rise permitted seawater flooding, to allow, firstly, colonisation by brackish water-tolerant L. pustulatum, followed by fully marine Tyrrhenian highstand biota, thus indicating that the mounds grew in a glacial phase, probably Stage 6, prior to marine Tyrrhenian deposits. This work has important implications for the relative dating of cut terraces and the deposits on them. Therefore: (1) not all cut terraces in coastal settings are necessarily the result of sea-level rise; and (2) terrace deposits are not necessarily always genetically related to the cut surface beneath them.

Effects of burial by sand and inundation by fresh- and seawater on seed germination of five tropical beach species

Plants growing on the beach are exposed to substrate mobility, freshwater inundation, and immersion in seawater, which greatly affect germination and species spatial distribution. In greenhouse experiments, we tested whether the most abundant species on the beach at La Mancha (on the Gulf of Mexico) were tolerant to burial and flooding. We buried seeds of Canavalia maritima, Ipomoea pes-caprae, Chamaecrista chamaecristoides, Palafoxia lindenii, and Ambrosia artemisiifolia at different depths. We used fresh- and seawater flooding with two frequencies: permanent and intermittent. The hard-coated seeds of Canavalia, Ipomoea, and Chamaecrista were left scarified and not scarified to test if dormancy was broken by the flooding regimes. Germination decreased as burial depth increased. We calculated a tolerance index for the burial responses, which indicated that Chamaecrista was the most tolerant species, followed by Canavalia and Palafoxia. Flooding inhibited germination, but more so permanent seawater flooding; it was especially lethal for species closest to the ocean such as Canavalia and Ipomoea. After transfer to freshwater, seeds of Chamaecrista, Palafoxia, and Ambrosia germinated. There was no evidence that hard-coat dormancy was broken by flooding. Tolerance to burial seems to be related to the spatial distribution of species but not to germination responses to flooding.Key words: germination, sand burial, freshwater, seawater, flooding, Gulf of Mexico.

A one‐dimensional percolation model of flooding and snow ice formation on Antarctic sea ice

A one‐dimensional thermodynamic sea ice growth model is developed with emphasis on seawater flooding and snow ice formation on Antarctic sea ice. To examine the possibility that flooding is the result of brine percolation through a porous ice matrix, and the consequences of this percolation on the salinity structure and mass balance of the ice, flooding is modeled in a semiheuristic fashion by examining two possible regimes for seawater and brine infiltration through the porous ice into the snowpack. A standard model assumes that the upward flow of brine is horizontally homogeneous and brine flow is modeled using a Darcian scheme. A simple model assumes that the infiltrating brine does not interact with the internal ice brine network, but instead percolates upward through cracks, or is restricted in spatial extent. Results of simulations are shown for the climatology in the Ross Sea and compared to field data from one autumn and one winter cruise aboard the R/V Nathaniel B. Palmer in 1995. Sensitivity studies are performed to show the effects of variations in climate forcing. The dependence of brine percolation and snow ice formation on key thermophysical parameters is investigated. Results indicate that the mass balance depends very strongly on the brine flow regime. In the standard model, ice salinities and brine volumes are greatly affected by brine percolation, creating a strong feedback between flooding and future snow ice production. Snow ice formation for the simple model was much more predictable and depended primarily on snow load. Comparison of results with field data indicate that if brine percolation is the major mechanism for flooding and snow ice formation, then there must be either substantial convective redistribution of salt to maintain ice porosity, or the flow must be spatially inhomogeneous.

Shoot Population Dynamics of Carex kobomugi on a Coastal Sand Dune in Relation to its Zonal Distribution

Shoot population dynamics of Carex kobomugi Ohwi, a rhizomatous perennial sedge with a guerilla-type growth form, dominating on Japanese coastal dunes, were examined to detect factors generating the zonal distribution pattern of the plant species. Relative growth rate of shoot (RGRS) and number of branching shoots formed by a mother shoot in a year (NBr) were measured in three populations occurring at three different distances from the shoreline. In 1992, Carex kobomugi shoots at the most inland site (90 m from the shoreline), where Imperata cylindrica var. koenigii dominated and soil-water salinity is always low, showed the lowest RGRS (0.0172 g g-1 day-1 from April to June and 0.00079 g g-1 day-1 in July) and the smallest NBr (1.3 shoots shoot-1 year–1 averaged for 3 years). Shoots of the species at the most seaward site (40 m from the shoreline), where the soil-water salinity is always higher than that of more inland sites, showed the highest RGRS (0.0228 g g-1 day-1 from April to June and 0.0093 g g-1 day-1 in July) and the largest NBr (2.5 shoots-1). However, Carex kobomugi population at the 40 m site had a high fraction of injured shoots (46% of total shoots sampled), which were recorded as shoots without any greenish above-ground part, and high mortality (0.34) due to temporal flooding of sea water caused by storms. In the intermediate site (70 m from the shoreline), Carex kobomugi had intermediateRGRS and NBr with low injury rate. The NBr value, however, showed a decreasing trend over the 3 years of observation, suggesting deteriorating effects of intraspecific competition on population dynamics. In the spring of the fourth year, shoots of Carex kobomugi at 70 m and 90 m from the shoreline produced 1.2 to 2.0 times higher number of buds per shoot than the 3-year-averaged NBrs. This suggests that some fractions of the buds were terminated or became dormant through intra- and/or inter-specific competition. The sparse distribution of Carex kobomugi at the 90 m site may be dictated by its competitive inferiority to Imperata cylindrica which has a denser root system and an aggressive growth form of a phalanx type.

Early winter ice and snow thickness distribution, ice structure and development of the western Ross Sea pack ice between the ice edge and the Ross Ice Shelf

A study of early winter first-year sea ice conditions and development in the western Ross Sea in May and June 1995 included measurements of snow and ice thickness, freeboard, ice core structure and stable isotopic composition. These variables showed strong spatial variability between the Ross Ice Shelf and the ice edge 1400 km to the north, and indicate that the development of the Ross Sea pack ice is quite different from that observed in other Antarctic sea ice zones. The thinnest snow and ice occurred in a 200 km wide coastal zone. The thickest snow and ice were observed in a continental shelf zone 200–600 km from the coast where the average ice thickness (0.8 m) determined by drilling is as thick as first-year sea ice later in winter elsewhere in Antarctica. A zone of moderate snow and ice thickness occurred on the deep ocean from 600 km to the ice edge at 1400 km. Thermodynamic thickening of the ice in the inner pack ice, <800 km from the coast, was dominated by congelation ice growth, which occurred in a greater amount (65%) and in thicker layers (mean: 20 cm) than was observed in the outer pack ice >800 km from the coast (amount: 22%; mean layer thickness: 12 cm) and elsewhere in the Antarctic pack ice. The preponderance of congelation ice in the inner pack ice might be due to a low oceanic heat flux on the Ross Sea continental shelf, and a colder, less stormy environment which favours the more frequent and prolonged calm conditions necessary for significant congelation ice growth. In the outer pack ice, thermodynamic thickening occurred mainly by snow ice formation (mean layer thickness: 20 cm) while dynamic processes, i.e., rafting and ridging, caused the thickening of frazil ice and columnar ice (mean layer thickness: 14 cm and 12 cm respectively). A greater amount of snow ice (37%) occurred in the outer pack ice than in the inner pack ice (15%), and both values indicate that in the Ross Sea, unlike other Antarctic sea ice zones, there can be significant seawater flooding of the snow/ice interface and snow ice formation before midwinter.

Waterflood Geochemical Modeling and a Prudhoe Bay Zone 4 Case Study

Abstract Scale formation during waterfloods can damage reservoirs far beyond the wellbore region. A comprehensive analysis with geochemical modeling can improve waterflood design in the selection and/or mixing of source waters and thus, mitigate formation damage arising from injecting incompatible fluids. The method also predict the types of scales and their severity at various production stages. This will help optimize treatment schedules and reduce operation costs. In the case study of Zone 4, Prudhoe Bay Unit (North Slope, Alaska), the geochemical model was validated with the laboratory analyses of Zone 4 produced water samples. Then it was used to evaluate the impact of mixing formation brine and seawater on rock-fluid interactions and scale formation. The prediction is consistent with the observation of calcite formation in early production at Prudhoe Bay. The model also predicts the precipitation of iron carbonate and iron sulfide scales as the seawater flood continues.

The Mitigation of NORM Scale in the Gulf Coast Regions of Texas and Louisiana: A Laboratory and Field Study

ABSTRACT Some oil field scales have the potential to contain regulated levels of naturally occurring radioactive materials (NORM). It is estimated that between 300,000 and 1,000,000 tons of NORM scale are produced each year. In addition, scale deposition in producing facilities negatively impacts rates of production and is expensive to treat and remediate. The most common NORM containing scale is BaSO4, or barite. This paper presents the results of a Gas Research Institute study that investigates the causes of NORM scale formation and mitigation techniques employed in the field. Chemical threshold scale inhibitors are generally employed to inhibit scale formation in production systems. However, there is little agreement on which scale inhibitor is most effective with respect to differing water chemistries, temperatures and conditions encountered. Results using a GRI patented inhibitor evaluation apparatus can be used to determine the most effective inhibitor for a specific field application. Work in the Michigan Basin presented in the last conference indicated that a phosphinopolycarboxylate was most effective against NORM barium sulfate scale formation at low temperatures in relatively fresh water. Further work in this study identifies phosphonates as being more effective in the higher ionic strength (TDS) waters and higher temperature regimes that can be expected in the Gulf Coast. A matrix of ionic strength and temperatures with inhibition response is presented. Although more NORM fields were studied, two are presented in detail. In these fields, three causes of NORM scale were identified; 1) Incipient scale in a well due to production; 2) Scale formation due to previous seawater floods and; 3) The commingling of waters from different zones or wells. Field treatment techniques employed in the two fields studied are summarized in the paper. Inhibitor squeeze procedures were also studied in the laboratory and in the field. A squeeze simulation apparatus was constructed to research inhibitor squeeze practices in the laboratory. Results from this work resulted in successful inhibitor squeeze applications in the field. The inhibitor squeeze apparatus and the field results are discussed in the paper. Squeeze life has been extended from an average of two to six months to two to three years or more as a result of the work.

Tsunami deposits in a lacustrine sequence of the Sanriku coast, northeast Japan

Lacustrine deposits of the Pacific coast of northeast Japan, consisting mostly of black organic mud, contain intercalated thin beds of well-sorted medium sand. Examination of the deposits from a coastal site of Sanriku has revealed that sand grains are of marine origin and are fractions of deposits in marshy ponds, transported from the littoral environment by a great flooding of seawater. The mode of sedimentation shown in the thin beds of sand implies that they were deposited by tsunamis, each with a maximum rise of 1 m or more above sea level.

Crystal structure, stable isotopes (δ18O), and development of sea ice in the Ross, Amundsen, and Bellingshausen seas, Antarctica

The crystal structure and oxygen isotopic composition of ice cores obtained from floes at the end of summer in the eastern Ross Sea, the Amundsen Sea, and the western Bellingshausen Sea were investigated to determine the ice growth processes and conditions that contribute to sea ice development in the eastern Pacific sector of the southern ocean. The isotope data indicate that a moderate amount of snow contributes to the development of the sea ice. However, even the combined use of isotopes and crystal structure analysis does not unambiguously explain the means by which all of the snow is entrained in the ice. Nevertheless, it seems clear that much of the snow is contained in granular snow‐ice that results from seawater flooding of floes and the base of the snow cover. The snow cover in the Ross‐Amundsen region was as much as 2 m deep and supported by 7‐ to 8‐m‐thick floes primarily composed of frazil ice. In the Bellingshausen region the snow cover and the floes were thinner than in the Ross‐Amundsen region. The Bellingshausen cores were composed primarily of multiple layers of frazil and congelation ice. In addition, in both regions there were numerous tipped or inclined blocks of congelation ice and layers of rafted nilas in the cores. The data indicate that the sea ice develops by multiple mechanisms in a turbulent environment.

Depositional environment of the snow cover on West Antarctic pack-ice floes

The depth, density, load and isotopic (δ18O) composition of the snow cover on pack-ice floes were measured in late austral summer 1992 in the eastern Ross, Amundsen and western Bellingshausen Seas. Snow-density values commonly exceeded 350 kg m-3and some were as high as 500 kg m-3. The densification of the snow occurs quickly and is attributed to a windy environment. The high density and sometimes considerable depth of the snow on the floes accounts for loads of as much as 700 kg m-2and resultant sea-water flooding of the underlying sea ice. Lower mean δ18O values in the Ross/Amundsen Seas snow cover suggest that the region might have a cooler climate than the Bellingshausen Sea region. Snow depths on floes in the Bellingshausen Sea region were lower than those in the Ross/Amundsen Seas region, because the Bellingshausen Sea floes were first-year ice. Possible annual units in the isotope profiles of snow, as much as 2m deep, indicate that floes in the Ross/Amundsen Seas region were 2-3 years old.

Depositional environment of the snow cover on West Antarctic pack-ice floes

The depth, density, load and isotopic (δ18O) composition of the snow cover on pack-ice floes were measured in late austral summer 1992 in the eastern Ross, Amundsen and western Bellingshausen Seas. Snow-density values commonly exceeded 350 kg m-3 and some were as high as 500 kg m-3. The densification of the snow occurs quickly and is attributed to a windy environment. The high density and sometimes considerable depth of the snow on the floes accounts for loads of as much as 700 kg m-2 and resultant sea-water flooding of the underlying sea ice. Lower mean δ18O values in the Ross/Amundsen Seas snow cover suggest that the region might have a cooler climate than the Bellingshausen Sea region. Snow depths on floes in the Bellingshausen Sea region were lower than those in the Ross/Amundsen Seas region, because the Bellingshausen Sea floes were first-year ice. Possible annual units in the isotope profiles of snow, as much as 2m deep, indicate that floes in the Ross/Amundsen Seas region were 2-3 years old.

Depositional environment of the snow cover on West Antarctic pack-ice floes

The depth, density, load and isotopic (δ18O) composition of the snow cover on pack-ice floes were measured in late austral summer 1992 in the eastern Ross, Amundsen and western Bellingshausen Seas. Snow-density values commonly exceeded 350 kg m-3and some were as high as 500 kg m-3. The densification of the snow occurs quickly and is attributed to a windy environment. The high density and sometimes considerable depth of the snow on the floes accounts for loads of as much as 700 kg m-2and resultant sea-water flooding of the underlying sea ice. Lower mean δ18O values in the Ross/Amundsen Seas snow cover suggest that the region might have a cooler climate than the Bellingshausen Sea region. Snow depths on floes in the Bellingshausen Sea region were lower than those in the Ross/Amundsen Seas region, because the Bellingshausen Sea floes were first-year ice. Possible annual units in the isotope profiles of snow, as much as 2m deep, indicate that floes in the Ross/Amundsen Seas region were 2-3 years old.

Scale Prediction and Laboratory Evaluation of BaSO4 Scale Inhibitors for Seawater Flood in a High-Barium Environment

Summary The potential for scale formation after seawater injection must be carefully studied when a new oil field is being developed in order to provide proper input data for the basic engineering design. This paper presents the results of a study of several facets of scale occurrence and control for a developing North Sea field characterized by a high-salinity, high-barium (up to 1, 000 ppm) formation brine. The results justify consideration of new technologies, such as treatment of the seawater to reduce the sulfate content.

The anatomy of an early Dinantian terraced floodplain: palaeo‐environment and early diagenesis

ABSTRACTThe lowermost Carboniferous rocks in the Cockburnspath area of east Berwickshire (southern Scotland) are interpreted as coastal floodplain sediments. A lower mudstone‐dominated unit is composed of silty mudstones and shales with subordinate sandstones and argillaceous ferroan dolomites (cementstones). These are interpreted as distal floodplain sediments with periodic crevasse‐splay deposition. The dark grey colour of the mudrocks suggests deposition in reducing conditions, probably in floodplain lakes. Most of the cementstones are concretionary, some with septarian cracks, suggesting an early diagenetic origin. An immature palaeosol suggests periodic pedogenesis under improved drainage. A synsedimentary erosion surface indicates incision of a valley into the floodplain, presumably in response to base‐level lowering.An upper sandstone‐dominated unit starts with fine‐grained rippled sandstones, cut by small channel sandstones. These are interpreted as floodplain lake deposits fed by crevasse channels. A distinctive conglomerate with cementstone clasts, wood fragments and fish remains is interpreted as a major overbank deposit, dumped into a pre‐existing floodplain lake. A bivalve fauna was established in the overlying mudstones, followed by a thin limestone with a restricted marine fossil assemblage, showing that seawater flooding of the lakes occurred at times.Mudrocks throughout the sequence contain no pyrite, except for the marine band which has an organic‐carbon/sulphur ratio and degree of pyritization value typical of marine sediments. The concretionary cementstones have δ13C values around —4 to —6%0/00 PDB which are interpreted as indicative of anaerobic oxidation of organic matter. The combined geochemical data suggest a significant involvement of iron reduction in cementstone formation, although the δ13C values are ambiguous in assessing the relative involvement of methanogenesis and methane oxidation. Limited seawater inundation of the floodplains might have supplied magnesium and calcium ions for dolomite formation assuming that any H2S derived as a result of sulphate reduction was oxidized by iron reduction. Alternatively a weathering source for solutes might have been involved.