Detailed visual seabed survey at drilling site 7218/11-1

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Figure2. ROVtransectsandrecordsof spongesfoundat Darwinduringthe baselinesurveyin 2011. Therelative amountsof the variouscategoriesof spongedensitiesare shownin the pie chart.Sedimentsamplesweretaken at the red dots (axescrosses).TheSPUDlocation is markedwith a blue triangle (seearrow). Figurefrom DNV (2011). The baseline survey did not reveal the presenceof soft or hard corals at the Darwin field. Furthermore,no red-list specieswere identified. The specieswith the highestregistereddensities were the squat lobster Munida spp. as well as spongespeciessuch as Geodia. Relatively high densitiesof soft bottom spongespecieswererecordedin the area, with 85.2%of the benthichabitat containing "scattered" to "high densities"of sponges.Darwinhad the highestrecordingsof sponge densities,relativeto other nearbyfieldssurveyedin 2011. (text modifiedfrom DNV2011). Qualitativeabundanceclassesappliedby DNVare: 1. Singlespecimen/rare, 2. Scattered,3. Common and4. Highdensity.Illustrationsof thesedensityclassificationsare givenin Section2, Materialsand methods. 1.2.2 Additional studies 2012 Basedon the resultsfrom the BaselineSurvey,duringthe planningof the well RENASaskedDNVto go deeperinto the data and try to identify areaswith low densityof spongeswere a CTSsolution could be deployedfor cuttingsdeposition.In addition SINTEFwas askedto model the spreadingof cuttingsby different cuttingshandlingsolutions. DNV(2012) summarizetheir findings:"Thescopeof work wasto assessthe distribution of deepsea spongesat Darwinby data interpolations.Byusingspongedensitydata from the BarentsSeavisual survey2011, interpolated maps were made, showingcalculatedvaluesof spongedensitiesin the drilling area.Backgrounddata like spongedensitiesfrom other fields and sedimentsamplingdata was included in the evaluation of the sponge situation at the Darwin field". DNV have made recommendationsfor locationsfor drill cutting depositionthat were estimatedto havethe lowest impacton the spongeassemblages . Akvaplan-niva AS, 9296 Tromsø 6 www.akvaplan.niva.no
1.3 Aims and challenges for present survey RENAScommissioneda new and more detailed visual sea bed surveyin the vicinity of the SPUD location (ED50UTM34N 8.001.215,E 411.870)for the well at Darwin (PL531). The survey was performed with parallel ROVlines 25 m apart, coveringa square of 800 times 800m within the coordinates(ED50UTM34)E 411.600to E 412.400,and N8.000.800 to N 8.001.600,around the plannedDarwin explorationwell, 7218/11-1. The estimatedtotal surveydistancefor the proposed programis28 km (15nm). Theprimaryaimsof the environmentalsurvey,asgivenby RENASare: Map the presenceof spongesand other vulnerable specieson the sea bed around the planned spud location with a higher resolution than during the 2011 visual survey (DNV 2011).If possible,the extentof areaswith sponge aggregationsis to be defined; Distinguishbetweensoft benthosandhardbenthosspeciesandcommunities; Identify asmuchaspossibleof the observedfaunato specieslevel; Givea descriptionof the generalvulnerabilityof the area. Secondaryaims: Map areaaccordingto coverage,accordingto table in NS9435:2009,and identify speciesor subgroupsin the area; Adviseand report on suitable cuttings deposition sites for a CTSsolution basedon fauna observations(spongedensities). RENASfurther specified:"The mappingshall have the highest spatial resolution closeto the well locations(combinationof 2011and2012survey).Themappingshallfollow the proposedpath, but it shall also take actual observationsinto accountduring ROVsurveying.The onboard biologistsare responsiblefor the path optimization. Thesurvey will be conductedwith an ROVthat asa minimum havea video camerawith sufficient lights and subseapositioningsystem.It is preferableto haveHDstill picture camerawith flashlight, HD video camera and laser for distance measurements(two laser beams with a set distance between). HD still and camerashould be connected. The surveylog shall provide geo-referenced biologicalregistrations.". Note:in practiceit is not alwayspossibleto provideall thesespecificationsunderthe time restrictions whichapply, but theseshallbethe aim. Detailed site survey at PL531 Darwin Akvaplan-niva AS Rapport 6051 - 1 7
Page 1 and 2: Detailed visual seabed survey at dr
Page 3: Akvaplan -niva AS Rådgivning og fo
Page 6 and 7: List of figures and tables FIGURE1.
Page 8 and 9: Preface In August,2012,Akvaplan-niv
Page 12 and 13: 2 Materials and methods 2.1 Vessel
Page 14 and 15: 2.3 Survey track and waypoints Thep
Page 16 and 17: Akvaplan-niva haspreviouslyworked w
Page 18 and 19: Figure7. Over4 tonnesof sponges(pre
Page 20 and 21: Figure10. BarentsSea.Spongebycatchi
Page 22 and 23: Somespongesform densereefs,and prov
Page 24 and 25: Figure14. Photosfrom Mercier(2012)s
Page 26 and 27: Figure16. Imagefrom Salina,2010,cla
Page 28 and 29: It is clear that Cochraneadopted a
Page 30 and 31: 5.2 Seafloor conditions 5.2.1 Sedim
Page 32 and 33: 5.3.2 Plots of sponge distribution
Page 34 and 35: Figure24. Locationof the 30 imagess
Page 36 and 37: Position16. 0-1 % coverage Position
Page 38 and 39: Position15. 1-5 % coverage.Geodiaan
Page 40 and 41: 5.3.3 Overall assessment of sponge
Page 42 and 43: 5.3.5 Dominant sponge species recor
Page 44 and 45: Hymedesmia Hymedesmia Polymastia Po
Page 46 and 47: Figure34. Observationsof the yellow
Page 48 and 49: Figure36. Observationsfor the blues
Page 50 and 51: Figure38. Upper:spottedwolffishrest
Page 52 and 53: Figure40. Largestonein foreground,w
Page 54 and 55: Table 6. Summaryof environmentalcos
Page 56 and 57: 5.4.2.2 Deposition Case 2: to seafl
Page 58 and 59: 5.4.2.4 Deposition Case 7: Depositi
Page 60 and 61:
5.4.3 Comparative assessment Table7
Page 62 and 63:
6 References Auster, P.J. 2007. Lin
Page 64:
Appendices Anelectronicsupplement(o
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Detailed visual seabed survey at drilling site 7218/11-1

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