1,720,986 research outputs found
Zafarani SERPENT report
No full textThe SERPENT Project (Scientific and Environmental ROV Partnership using Existing Industrial Technology) carried out an investigation into deep-sea ecology and the effects of disturbance from hydrocarbon exploration at Statoil’s Zafarani Prospect in Block 2 offshore Tanzania. SEPRENT visited the Ocean Rig Poseidon which drilled the Zafarani well in 2600 m water depth in the western Indian Ocean off Tanzania, an area largely neglected by deep-sea science and exploration, and therefore lacking in the background information required to predict and understand anthropogenic effects on the fauna associated with the seabed.The fieldwork involved the use of the ship’s remotely operated vehicles during standby time to survey the seabed using high definition video cameras in order to describe the seabed environment and quantify the deep-sea organisms encountered around the drilling operations. Quantitative straight line video transect surveys were carried out to determine the abundance and diversity of the fauna and map the distribution of drill cuttings visible on the seabed. Sediment samples were also collected in four headings in order to verify the findings of the video survey.The water column temperature reduced from 28?C at the surface to 2?C at the seabed with relatively consistent salinity with depth. The seabed was characterised by soft sediment which, in undisturbed areas, showed abundant signs of the activity of seabed organisms in the form of burrows, tracks and traces. Forty three species of larger organism (megafauna – visible in video footage) were encountered. Xenophyphores, echinoderms and sponges dominated the benthic megafauna. Ten species of deep-sea fish were recorded in the video observations.Visual observations showed that drilling disturbance had a noticeable effect causing a layer of drill cuttings to overlie the natural seabed. This reduced the variability of the seabed obscuring the evidence of faunal activity. This was predominantly to the north of the well, in which heading it was not possible to reach natural seabed at the full extent of the ROV tether (150 m). In other headings the cuttings disturbance reached approximately 30-50 m from the well. Chemical analysis of the sediment samples verified the observations from ROV video, showing high levels of barium to the north of the well. Examination of the sediment using scanning electron microscopy also showed evidence of high levels of barium sulphate (a key component of drilling mud). In comparison, samples taken in all other headings showed low barium concentration and the sediment samples were dominated by the remains of phytoplankton such as coccolithophores which naturally settle to the seabed.The abundance of megafaunal organisms was significantly reduced within the area impacted by the drill cuttings, this was of particular importance in the area up to 20 m from the BOP in all headings and for the entire survey length to the north of the well. Other measures of the megafaunal community (species diversity and multivariate analysis of the megafaunal assemblage composition) suggested similar patterns but beyond the visible cuttings the initial effects of drilling disturbance appeared to be local, however it is not clear how far this extends to the north. The presence of lebensspuren (animal tracks and traces) may be a more sensitive measure of drilling disturbance than megafaunal abundance in deep, soft-sediment environments such as Zafarani.This project provides valuable data about the deep water fauna of the area around the deep water drilling operations at Zafarani that was highlighted as lacking in pre-drilling assessments. It also verifies the predicted impacts of top- hole drilling suggested by modelled discharge calculations, providing local scale resolution to predicted effects
Lavani SERPENT report
No full textIn follow-up to work at Zafarani a field study was carried out to describe the deep-sea fauna and the effects of disturbance from seabed discharges associated with exploration drilling at Statoil’s Lavani location, at 2400 m depth in Block 2 offshore Tanzania.The fieldwork was carried out from the drillship Ocean Rig Poseidon during drilling operations at Lavani. The ship’s remotely operated vehicles were used during standby time to survey the seabed using high definition video cameras. Nine quantitative straight line video transect surveys (up to 260 m in length) were used to determine the abundance and diversity of the fauna, describe the seabed environment and map the distribution of drill cuttings visible on the seabed. Replicated sediment samples were also collected in at five locations up to 180 m from the BOP in order to quantify the disturbance gradient and verify the findings of the video survey.The background environment was soft sediment consisting of typical deep-sea ooze. It comprised planktonic material such as coccoliths settled to the seabed from the surface water. Many tracks and burrows created by seabed organisms covered the surface of undisturbed sediment. The deep-sea animals observed at the site were similar at Lavani to Zafarani. At Lavani abundance of organisms was lower but more diverse that at Zafarani. The assemblage was dominated by Xenophyophores, Sponges and Echinoderms. Notable observations not encountered at Zafarani include large echinothuriid sea urchins, a large skate and a diverse community associated with sunken wood.Drilling disturbance resulted in coverage of the seafloor with drill cuttings. This generally extended to approximately 60 m from the well. A pilot well was drilled to the east of the main well and to the east and north east disturbance was visible to a distance of 140 m from the BOP. Within this area the abundance of the megabenthic assemblage was significantly reduced. Distribution of cuttings extended furthest to the east of the well but there was not a single direction in which the cuttings were dominantly distributed as at Zafarani. In contrast to Zafarani, at Lavani background seabed could be observed in all headings. The increased disturbance documented to the east of the well likely results from the drilling of a pilot well in this area rather than the effects of seabed currents. The pilot hole was visible in the video surveys and clearly extended area of disturbed seabed. Sediment sampling showed that there was significantly elevated barium concentration close to the well (indicative of drill mud), which reduced with distance from the BOP.The abundance and diversity of megafauna was significantly reduced in close proximity to the well following smothering disturbance. Further from the well there was great variability in both parameters owing to varying degrees of disturbance. It is expected that the abundance and diversity of megafauna beyond 140 m from the BOP at Lavani is representative of the background for the area
Whirlwind Recovery SERPENT report
No full textThis document reports the results of SERPENT’s work at Hurricane’s Whirlwind site at 185 m depth in the north east Atlantic, west of Shetland, UK. The report focuses on the work carried out over two visits to the semisubmersible drilling rig Wilphoenix in 2011. These visits were the latest in a series of four visits to the Whirlwind location and part of a wider collaboration with Hurricane at Whirlwind and Lancaster involving six visits to Hurricane’s offshore operations in the area since 2009.The Whirlwind project used work-class and observation-class remotely operated vehicles (ROV) launched directly from the drilling rig to explore marine biodiversity at the seabed in the vicinity of the drilling operations and monitor changes in biodiversity over time. Surveys took place immediately after drilling began, a month later and after a year of no further disturbance.In total sixty one megafaunal species have been observed at Whirlwind and Lancaster since 2009. Most species have been recorded at both sites. Quantitative video surveys suggest the dominant species are the cnidarians Metridium sp. and hormathiid anemones, the crustaceans Pagurus sp. and Munida sp. and the echinoderm Porania pulvillus.In 2011 there was evidence of a reduction in area of seabed visibly impacted by drill cuttings. The area of complete coverage of the seabed around the well reduced from 7054 m2 to 1433 m2. A relatively stable area of cuttings persisted close to the well, extending to approximately 20 m. Comparison of measurements from marker buoys deployed before drilling suggest that the vertical accumulation of cuttings had not reduced.Megafaunal abundance and diversity were both higher in 2011 compared to 2010 suggesting evidence for recovery, although abundance remained low in the area closest to the well. There was photographic evidence for colonisation of the cuttings close to the well in the form of polychaete tube worms that were abundant on the soft sediment of the drill cuttings.At Whirlwind a protective structure had been placed over the well for the period between the end of drilling in 2010 and when the operations began again in 2011. This had been colonised by numerous organisms including a coverage of hydroids which provided a habitat for many invertebrates and fish. Most notable were at least 10 large European Conger that were living within the structure
Haklang SERPENT visit report
No full textThe SERPENT project made two visits to the Transocean Leader semisubmersible drilling rig to studyseabed disturbance at the Statoil operated Haklang prospect in the Norwegian Sea in the autumn of 2008.Seabed depth at Haklang was 1250m and the water temperature was -1?C.Using the Oceaneering Magnum ROV seabed disturbance was assessed by visual observations andsediment sampling immediately after drilling impact. Megafaunal community observations were used todetermine the ecological changes. Video showed a cuttings pile with complete coverage of the seabed andabsence of megafauna extending 25-55m from the well. Beyond this seabed coverage was heterogeneouswith cuttings visible to at least 100m to the north west. Mean megafaunal abundance was low to a distanceof 40 m. Cerianthids were the dominant organisms and were present closer to the well than other taxa,perhaps because of their burrowing habit. The longer term effects of this disturbance are unclear.In addition specimens of the invertebrate megafauna were collected at Haklang
Shell South Uist SERPENT final report
No full textThis report presents the results from the SERPENT project collaborative research with Shell at the SouthUist deep-water exploration oil well, drilled from the Leiv Eiriksson semisubmersible rig in the Faroe-Shetland Channel. The study was designed to investigate seabed disturbance resulting from the drillingactivities at South Uist and the effects of these activities on the benthic environment and megafaunalorganisms.The remotely operated vehicle (ROV) was used to take video transects of at least 100m in length fromwhich the extent of drill cuttings and megafaunal densities were assessed. Cuttings were clearly visible onthe seabed and were over a metre deep close to the well with a shallower layer extending to beyond 100mto the west. Twenty-five megafaunal taxa from seven phyla were observed at South Uist and species densityand diversity were reduced close to the well.In addition sediment samples for subsequent chemical analysis were collected at 25, 50, 75 and 100m fromthe well and specimen samples of the characteristic megafauna were obtained
Asterix SERPENT visit report
No full textThis report presents the results from the SERPENT project collaborative research with StatoilHydro at theAsterix deep-water exploration oil well, drilled from the Transocean Leader in the Norwegian Sea. Thestudy was designed to investigate seabed disturbance resulting from the drilling activities at Asterix and theeffects of these activities on the benthic environment and megafaunal organisms.The ROV Magnum 018, was used to take eight video transects of at least 100m in length which were usedto assess visually the extent of drill cuttings and to determine megafaunal densities. Also a series sedimentsamples were collected using ROV operated push cores at 50, 80 and 100m from the well to determineheavy metal concentrations, total organic matter and particle size distribution.Comparison of these methods suggested disturbance was variable depending on heading but suggestedcomplete coverage of the seabed up to 60m from the well and partial coverage to 100m. Analysis of thesediment showed elevated Barium concentration in surface sediments at all sample locations, decreasingwith distance and with depth sections. At the site closest to the well mean particle size increased incomparison to the background sediment. These physical changes were associated with significantreductions in megafaunal abundance and changes in the megafaunal community structure, with very fewanimals observed in a 50m radius of the well. Small ophiuroids were extremely abundant at the sitereaching up to 20m-2. Similar to the megafauna, their numbers were reduced by the disturbance event anddensity was significantly reduced within 80m of the well.Details of a short documentary film made by StatoilHydro about the SERPENT collaboration on board theTransocean Leader are also given here
Chevron Rosebank North SERPENT final report
No full textThis report documents the SERPENT project collaborative research with Chevron at the Rosebank North exploration drilling site at 1100m water depth in the Faroe-Shetland Channel. The opportunity enabled access to the Magnum 156 remotely operated vehicle (ROV) on the Stena Carron drill ship to carry out a detailed biodiversity survey.Video transects were carried out in high definition extending to approximately 500m. Twenty-eight megafaunal taxa were observed at Rosebank North with representatives from 8 phyla and combined imaging and sampling ensuredthat the taxonomic resolution was high. SNAPS, a novel device for preservation of nucleic acids of specimens collected at depth, developed through SERPENT was tested during this visit and push core samples of the sediment were collected to assess drilling disturbance.During this visit video footage of deep-sea fauna and interviews with offshore staff were collected for use in anepisode of the BBC television series “Coast”
Lancaster SERPENT visit report
No full textThe SERPENT project carried a collaborative research mission with Hurricane Exploration (HEX) at theLancaster exploration well in August 2009. The well was drilled from the Byford Dolphin, west ofShetland. The study was designed to investigate benthic biological diversity with particular reference to theeffects of disturbance on the seabed resulting from the drilling activities. Photographic and quantitativevideo methods were used to observe benthic megafauna and demersal fish using a Spartan workclassindustrial ROV, collecting digital stills images and close-up video when possible. Physical data werecollected throughout the mission. In addition bait was deployed to attract fish to the ROV cameras. Theobservations are archived in the SERPENT database. An experiment was carried out to assess the effects ofphysical disturbance on the asteroid Porania pulvillus.Mean seabed temperature was 10.2oC and salinity was 35.4. Maximum water temperature was 13.9oC in thesurface waters (9m) and the thermocline was at 100m. Current data were collected for a 48 hour periodduring the visit. The current was tidally reversing with a mean velocity of 10.52 cm s-1 with dominant watermovement from southwest to northeast.Drill cuttings extended to at least 60m from the BOP and beyond 100m to the north and west. The cuttingspile was a maximum of 2m in height around the BOP reducing to around 400mm at 7m from the BOP andwas between 50 and 150mm at 15m from the BOP.This disturbance resulted in a reduction in megafaunal density within 30m of the well and an increase in thescavenging hermit crab Pagurus prideaux in impacted areas of sediment, particularly between 30-50m fromthe BOP and measures of species diversity (S and H’) increased with distance from the source of thedisturbance
Total Akpo Nigeria SERPENT report
No full textThe ecology of the deep waters off Nigeria is poorly understood but the area attracts increasinghydrocarbon exploration. Through collaboration with a variety of offshore oil and service companiesSERPENT carried out novel deep-water science at the Akpo site offshore Nigeria. This visit to the JackRyan drilling rig was the first visit of its type in Nigerian waters and the most comprehensive visitundertaken by SERPENT in Africa. The aim of the visit was to make initial assessment of Nigeriandeep-water biodiversity through collection of both images and physical samples of the benthic fauna.Seabed water temperature at 1366 m was 5.3?C. Video analysis revealed 36 taxa representing 5 phylaand 22 specimens were collected. As there is limited knowledge of the Nigerian deep-water fauna, ataxonomic phase will be important to reinforce detailed future ecological research and to provide astrong baseline against which to assess changes in the deep-water environment
Recovery at Morvin: SERPENT final report
Full text linkRecovery from disturbance is poorly understood in deep water, but the extent of anthropogenic impacts is becoming increasingly well documented. We used Remotely Operated Vehicles (ROV) to visually assess the change in benthic habitat after exploratory hydrocarbon drilling disturbance around the Morvin well located at 380m depth in the Norwegian Sea.An ROV, launched directly from the rig drilling the well in 2006 was used to carry out video transects around the well before drilling and immediately after. On a return to the site three years after disturbance a larger survey was conducted with a ship-launched ROV in 2009. Transects were repeated at the disturbed area and random background transects were taken. Visible drill cuttings were mapped for each survey, and positions and counts of epibenthic invertebrate megafauna were determined, revealing a fauna dominated by Cnidaria (45% of total observations) and Porifera (33%).Immediately after disturbance a visible cuttings pile extended to over 100m from the well and megafaunal density was significantly reduced (0.07 individuals m-2) in comparison to pre-drill data (0.23 ind. m-2). Three years later the visible extent of the cuttings pile had reduced in size, reaching 60m from the well and considerably less in some headings. In comparison to background transects (0.21 ind. m-2), megafaunal density was significantly reduced on the remaining cuttings (0.04m-2), but beyond the visible disturbance there was no significant difference (0.15m-2). The investigation at this site shows a return to background densities of megafaunal organisms over a large extent of the area previously disturbed. However a central area, where the initial cuttings pile was deepest, demonstrated reduced sessile megafaunal density which persisted three years after disturbance. Elevated Barium concentration and reduced sediment grain size suggests persistence of disturbance beyond the remaining visibly impacted area which may result in changes to the infaunal communities undetectable by ROV video survey
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