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Oil & Gas

Drilling in ­sensitive areas A guideline for “best practices” keeping focus on the seabed environment


02 Oil & Gas Drilling in sensitive areas




Visual mapping



What is sensitive fauna?

Impact assessment



International and national legislation

Environmental monitoring



Planning a drilling operation

DNV GL environmental risk management services

Drilling in sensitive areas Oil & Gas 03

This brochure is intended as a quick reference manual and guidance for companies venturing into areas in Norway that might be considered as sensitive. It will answer the following key questions: ■■ What are regarded as sensitive fauna and habitats, and where can one expect to find it? ■■ What should be taken into consideration when planning for operations and applying for discharge permission in areas regarded as sensitive? ■■ How can we monitor the impact our activities have on the marine seabed environment? The brochure will also give a best practice approach to drilling operations step by step, keeping focus on the seabed environment. In addition it will provide an overview of relevant DNV GL services that can be tailored to address these challenges.

Situation: The offshore industry is moving closer and into protected, sensitive seabed a ­ reas on the Norwegian shelf. Areas with cold water corals, deep sea sponge aggre­gations or spawning grounds for sand eel and other benthic resources. Complication: Many energy companies are new or unacquainted with drilling in sensitive seabed areas, are unaware of requirements, rules and best practices for operating (drilling, anchor handling etc.) and have limited environmental ­knowledge. Question: How can oil and gas companies uphold the value of conducting ­business in an environmentally sound and responsible manner following requirements and best practices for operating in sensitive areas? This guideline will focus on drilling in sensitive areas, providing info and guidance to our customers.

04 Oil & Gas Drilling in sensitive areas

BACKGROUND During offshore activities and other physical/mechanical interventions on the ­seabed, there are many potential environmentally harmful processes, from oil leakage to smothering by sedimentation. By implementing a risk-based environmental strategy, work can be carried out efficiently at low risk for the environment.

If sensitive fauna is found in the area, there might be a call for environmental impact assessments and monitoring of activities affecting the seabed habitats. Adverse effects from drilling discharges, anchor operations, seabed construction, and pipe laying should be held as low as possible. Increased need for mapping and monitoring of sensitive fauna Inventories of red-listed species and vulnerable habitat types in Norway are growing, as is public awareness, and the companies’ corporate responsibility. When companies plan activities in areas with possible sensitive or red-listed marine fauna, the government generally demands visual mapping of the seabed habitats within the expected area of the activities. This focus on corals and other potentially vulnerable natural resources has led to a profound increase in the need for sensitive species mapping and environmental monitoring during petroleum operations. Necessary extra surveying, baseline surveys and monitoring depends on the geographical areas in which activities are taking place.

Benthic communities with sponges and corals and similar are difficult to identify or monitor with the methods used in traditional sediment monitoring (e.g. grab sampling). Destructive sampling and monitoring methods like trawling and benthic sledges are also not suitable, because of the sensitive nature of vulnerable habitats. Visual surveys using an ROV (Remotely Operated Vehicle), drop camera, or towed video platform is favourable methodological options for investigating potentially vulnerable areas of the seabed without damaging it. A standard for visual surveys has been developed (NS-EN 16260:2012, Norsk Standard, 2012), to ensure quality of work and to allow for repeatability assuring that comparable studies can be implemented. One of the challenges of visual research and analysis of benthic communities is to identify the individual species’ tolerance to impacts in relation to seasonal variation, distribution patterns, age/life stage, behavioural and biological properties, and then draw conclusions in a larger context. Comparisons of data from side scan sonar, multibeam echosounder, catch statistics from trawling activity, and comparison of research results and surveys conducted in the region, are important elements in understanding the big picture.

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Impacts and effects to sensitive fauna from offshore activities

Pipelaying Drilling



Subsea construction


Pile driving Anchor operations

Habitat deterioration




Physical damage

Noise and vibration


06 Oil & Gas Drilling in sensitive areas

WHAT IS SENSITIVE FAUNA? The following section will provide information of important characteristics and where special care generally needs to be taken in the planning of drilling activities.

Cold water coral reefs and -gardens Main areas Mid Norway/ Haltenbanken Description Corals are most abundant on the continental shelf in mid-Norway at 200–400 m depth. The highest densities occur along the continental break and on edges of shelf-crossing trenches (Fosså et al 2002). The reef building stony coral Lophelia pertusa is regarded as a threatened species according to the Norwegian Red List for species (Kålås et al., 2010, based on UICN definitions) and OSPAR 2008a. Also, according to OSPAR 2008b, and according to Norwegian Red List for habitats (Lindegaard and Henriksen 2011), “Coral gardens” are defined as a relatively dense aggregation extending over at least 25 m2 of colonies or individuals of one or more coral

species, such as leather corals (Alcyonacea), gorgonians (Gorgonacea), sea pens (Pennatulacea), black corals (Antipatharia), hard corals (Scleractinia) and, in some places, stony hydroids (lace or hydrocorals: Stylasteridae). Other red-listed species such as redfish (Sebastes) are often found inhabiting the coral reef systems in Norway. Considerable knowledge on the corals at the Norwegian Continental Shelf has been assembled in recent years, due to impacts the offshore and fishery industry may have on corals. Governmental measures like establishment of mapping programs (MAREANO), protection of specified areas and regulations have been developed. Sensitivity Corals, in particular Lophelia, are sensitive to smothering/sedimentation and physical damage from e.g. anchor operations. Chemical effluents and accidental spills will also have the possibility of adversely influencing coral health and reproductive capability. CORAL AREAS CORAL REEFS

The cold water coral Lophelia pertusa

Lophelia pertusa The cold water coral Lophelia pertusa is the most common reef building stony coral in the North Atlantic Ocean, creating a diverse habitat for more than a thousand different species. L. pertusa is found on both sides of the Atlantic Ocean from 30 m down to 3,000 m, but generally found deeper than 300 m. L. pertusa is known for being relatively slow-growing, and the largest reef structures are more than 9,000 years old. L. pertusa requires temperatures between 4 and13°C and salinities of around 35—38 psu, with oxygen concentrations >3 ml l-1 (Freiwald et al. 2004; Taviani et al. 2005; Dodds et al. 2007; Davies et al. 2008).

Drilling in sensitive areas Oil & Gas 07

Deep-sea sponge aggregations Main area The Barents Sea Description High densities of sponges are mainly found in the north of Norway, like Tromsøflaket and the Barents Sea, but spread communities of sponges are also found at Haltenbanken and in the North Sea. Sponges are benthic and filter-feeding animals that mainly live in the marine environment. Within Norwegian waters there are 260 species of sponges, with the class Demospongia accounting for most of the species present. Water depths where sponges are usually found are between 250 and 1,300 m (Bett and Rice, 1992). Sponges occur on both hard substrata, such as boulders and cobbles, or on soft substrate. Higher densities are usually found in higher aggregates on hard bottom substrat. Sponges are often found on iceberg plough-mark zones because stable boulders and cobbles provide attachment for sponges. Deep-sea sponge aggregations are on the OSPAR list of threatened and/or declining species and habitats (OSPAR Agreement 2008 – 7). Deep-sea sponge aggregates are primarily composed of the classes Hexactinellida and Demospongia (OSPAR 2010). There are 33 sponge species that are classified on the Norwegian Red List (Kålås et al., 2010), and all but one species are classified as Data Deficient (DD). Twenty of the species on the Red List belong to Demospongia, with 19 classified as (DD) and one as Near Threatened (NT) (Norwegian Red List 2010). Sensitivity Sponge bed habitats are sensitive to sedimentation and smothering, and disturbance and removal by trawling.

Soft bottom sponge habitat

high density sponge aggregations

08 Oil & Gas Drilling in sensitive areas

Sand eel spawning grounds Main area The North Sea Description The lesser sand eel has been an important commercial fish with landings of over 300,000 tons/year in Norway. Due to overfishing the stocks have fallen; in the Norwegian economic zone the stocks were reduced 88–94% between 2003 and 2005, and today the sand eel fishery is closed except for a smaller experimental quota of 40,000 tons (2012). The active measures made by the Norwegian government have though, resulted in a positive increase in sand eel stocks and in 2010 it was no longer critically threatened, and so removed from the Norwegian Red List. Sensitivity Caution must be taken when operating in areas with potential sand eel populations. Sand eels are shown to be sensitive to seismic shootings (Hassel et al., 2004), and fishermen have repeatedly reported that

trawl catches decrease when a seismic ship is operating in the area. The potential impact by pollution and sedimentation due to drilling operations is high because of their stationary habits. Sand eels are also potentially sensitive to noise pollution from drilling activities.


Ammodytes marinus The lesser sand eel (Ammodytes marinus) is a north Atlantic fish species found from the Barents Sea down to the Baltic Sea and Great Britain. The sand eel spends most of its time buried in sandy sediment of preferable depth of 30â&#x20AC;&#x201C;70 m (Wright et al., 2000), but can be found at 15â&#x20AC;&#x201C;120 m. It is only active during the light hours of the year hunting pelagic and feeding on zooplankton, fish eggs and fry. During the wintertime the sand eel goes into dormancy, buried in the sand, and except for spawning which occurs in December to January, it remains inactive until spring time, usually April. The lesser sand eel is selective in which type of sediments it burrows, not too fine so that the pore water can be oxygenated and not a too high content of fine gravel or larger, making digging difficult. A mixture of coarse and medium fine sand with a low silt and pelite content (<10%) and small amounts of gravel (<10%) is a preferable substrate (Wright et al., 2000; Holland et al., 2005). The sand eel reaches a maximum length of 24 cm, lives a maximum of ten years, and is an important food source for many fish, mammals and sea birds.

Š Rudolf Svensen

Drilling in sensitive areas Oil & Gas 09

10 Oil & Gas Drilling in sensitive areas

International and national legislation Relevant to marine conservation in Norwegian waters. Petroleum Safety Authority, 2011 Duty to monitor and record data from the external environment according to Section 48 of the Framework Regulations, as specified in Chapter X (Sections 52 to 59) of the Norwegian Activities Regulations (Petroleum Safety Authority, 2011), particularly the surveying of vulnerable environmental resources (defined by Section 53 of the Activities Regulations), which include coral reefs, sponge havens, spawning grounds and other. Stortingsmelding no. 8, 2006 In the management plan for the Barents Sea, vulnerability is defined as the ability of a species or the area where it is living to maintain its natural state related to external, often anthropogenic influences. Habitatshaping or forming species like corals and sponges are clearly addressed as potentially vulnerable. The Norwegian Red list for species (Kålås et al., 2010), the Norwegian Red List for Habitat types (Lindegård and Henriksen, 2011). The Norwegian Red List includes 4,599 species (Lindstrøm et al., 2010).

The Norwegian nature diversity act (Law 2009-06-19 no. 100) applies to the continental shelf and impel that a precautionary principle is used when carrying out activities that might damage or disturb the seabed habitats (§9). The Pollution Control Act to protect against pollution and waste Under Section 49 of the Act of 13 March 1981 No. 6 there is a duty “to provide the pollution control authority or other public bodies with any information necessary to enable them to carry out their tasks pursuant of this Act”. The Marine Resources Act (2008) The Marine Resources Act aims to ensure sustainable and economically profitable management of wild living marine resources and genetic material derived from them, while minimising impact upon non-target species. The Nature Conservation Act (1970) The Act aims to protect natural habitats and wild flora and fauna of Norway. 2,700 km2 of Norway’s marine waters and 68 species (terrestrial and aquatic) are protected under this Act.

Drilling in sensitive areas Oil & Gas 11

The Wildlife Act (1981) The Act was formed to protect the external ­environment from pollution and to reduce existing pollution, this applies to exploration, for recovery and exploitation of submarine natural resources on the continental shelf, including the cessation of such activities. OSPAR (2008, 2008a) Habitats and species listed as threatened or declining by OSPAR. Norway has an international responsibility to safeguard a representative selection of fjord and coastal areas types not found anywhere else in the world. The Bern Convention (1979) The aims of this Convention are to conserve wild flora and fauna and their natural habitats, especially those species and habitats whose conservation requires the cooperation of several states, and to promote such cooperation. The Norwegian Water Management Regulations This incorporates the EU Water Framework ­Directive into Norwegian law. The objective is to achieve good ecological and chemical status for

all ­water bodies by 2021. The regulations apply to inland and coastal waters out to the baseline. Norway is also making management plans for its jurisdictional areas of the North Sea, the Norwegian Sea and the ­Barents Sea (State of the Environment Norway, 2007). H ­ owever, The Water Management Regulations are not intended as a tool for regulating harvesting of fish stocks or other marine resources, nor for r­egulating the aquaculture industry along the coast. Havmiljø.no Cooperation between central administrative b ­ odies and research institutions to establish a common ­database on natural resources and their vulnerability. ■■ Havforskningsinstituttet (HI) ■■ Norsk institutt for naturforskning (NINA) ■■ Norwegian Environment Agency ■■ Norsk polarinstitutt (NP) ■■ Norges geologiske undersøkelser (NGU) ■■ Statens kartverk sjø ■■ DNV GL as consultant for the analysis system

12 Oil & Gas Drilling in sensitive areas

PLANNING A DRILLING OPERATION For drilling in sensitive areas, a precautionary approach is important. DNV GL can ­assist in planning and monitoring the environmental impact, and we deliver a series of services that can contribute to a successful drilling operation, with the smallest possible impact on the environment. Early planning More than often, environmental regulations are overlooked by the oil and gas companies and therefore are addressed too late in the process, resulting in costly additional work. An environmental pre-study is a simple measure that can reduce cost, structure and simplify the workflow. If you are a new actor on the Norwegian Shelf or otherwise need advice on how to proceed when awarded a field in a sensitive area, DNV GL can conduct a desktop pre-study based on our

extensive data and knowledge gained from years of experience. A pre-study can include an introduction to Norwegian environmental legislation, interpretation of data, identification of sensitive areas and recommendations on how to proceed. Site survey and baseline data A natural first step of a monitoring program is to start with a site survey, mapping the location with side scan sonar and multibeam echosounder.

Recommended workflow with timeline

36–6 months in advance

12–6 months in advance

6–3 months in advance

1–0 months in advance

PLANNING Pre-study

Resource mapping

Impact assessment

Finalisation of plans

Gather existing data/ information

Mapping of environmental resources

Best fit analysis

Mitigating advisory

Perform anchor analyses

Verify data with visual mapping

Plan spud location Perform discharge planning Other

Coral/sponge risk assessment Dispersion modelling

Monitoring program Discharge application to Norwegian Environment Agency (Miljødirektoratet)

DRILLING Discharge permission from Norwegian Environment Agency


Baseline/ before drilling/ anchor operations

During drilling

After drilling

Deployment of monitoring equipment


Visual mapping

Sediment sampling Selected coral structures at risk visually examined and documented

Current Turbidity Sedimentation rate

Sediment sampling Retrieval of monitoring equipment

Drilling in sensitive areas Oil & Gas 13

Colour codes

Site survey results

DNV GL service

Are potential coral structures identified within the site?

Action required Norwegian Environment Agency



Treat all potential structures as worthy of protection?

Based on: Pre-cautionary distances/ dispersion models Planned technical solutions

E.g. Move spud site Use of CTS Move anchor corridors Use DP rig Transport cuttings to shore Reroute pipe corridors Reduce drill bit size

Corals within 500 m of drill location?


Corals within 10 m of pipe laying corridor?


NO Discharge application + permit

E.g. Drilling discharges Plume impact Accidental discharges Anchors and chain impact Pipe laying impact


Develop monitoring program

Monitor activities

Perform visual mapping

Corals within 30 m of anchor corridors?

Perform impact assessment

Technical mitigation measures/ risk reducing measures


Drilling campaign

14 Oil & Gas Drilling in sensitive areas

VISUAL MAPPING Sonar and echosounder data collected during a site survey are analysed, and the results act as the basis for further decisions to conduct an eventual visual mapping operation. To measure the benthic footprint of a drilling campaign, it is crucial to know the environmental conditions before drilling – The Baseline. There are no general requirements to perform a baseline survey prior to exploration drilling. However, according to the Activity Regulations (Requirements for Environmental Monitoring of the Petroleum Activities on the Norwegian Continental Shelf regulation 2010-04-29 no. 613) baseline surveys need to be performed prior to: ■■ Exploration drilling in new areas with unknown nature types, or where presence of vulnerable environmental resources has been proven to be found in association with sediments. ■■ In other areas, prior to production drilling and development start at each of the fields. Depending on where and what sensitive environmental resources are expected, different parameters can be included in the baseline survey: ■■ Visual mapping, with ROV or drop camera, of potentially vulnerable resources. ■■ Sediment chemical and grain size characterising from sediment core samples. ■■ Turbidity. ■■ Benthic fauna diversity. ■■ Currents. ■■ Background noise. DNV GL has extensive experience in conducting baseline surveys and can help with both planning and execution. Mapping of seabed features Side scan sonar and multi-beam echo sounder are commonly used during site surveys in order to ­collect data of the seabed features in an efficient way. The area covered using these methods may vary, but a typical size is at least 4x4km. The data provided from the side scan sonar in a mosaic image, create the basis for interpretation of potential coral structures within the surveyed area. The multibeam echosounder primarily collects depth data, and will reveal seabed features such as ice scouring plough marks.

Interpretations of side scan mosaic All potential coral structures down to the limitation of the resolution of the mosaic should be: ■■ Circled as accurately as possible around the outermost edges of the structure. ■■ Geo referenced in the middle of the structure (for tabulated purposes). ■■ Area for each structure calculated (for tabulated purposes). ■■ Labelled with a unique number (for tabulated purposes). ■■ A buffer around each structure should be made to reflect the limits of accuracy of the positioning of the mosaic. Visual mapping Potential coral structures or general sponge distributions identified by multibeam echosounder and/or sidescan sonar survey should be surveyed by visual methods. Techniques and methods to be followed are given in Norwegian Standard NS-EN 16260:2012 (Norsk Standard, 2012). When conducting a visual mapping, the use of a ROV is highly recommended, documenting possible coral structures and sponges detected in the planned drilling area. The size and condition of these are registered and categorised in groups in accordance to condition and coverage. DNV GL has high competence and experience with visual mapping from numerous operations. We offer mapping with our own ROV, or provide guidance and advisory from the survey vessel. Our Marine ­Biologists are highly skilled in interpreting under­ water film and footage.

Drilling in sensitive areas Oil & Gas 15





“GOOD“ refers to apparently intact L. pertusa.



“MODERATE“ refers to reefs containing both dead and living colonies of L. pertusa.



“POOR“ indicates an area dominated mostly by dead corals with relative small patches of living L. pertusa.



“DEAD“ No living colonies of Lophelia pertusa are observed in these areas.



16 Oil & Gas Drilling in sensitive areas

Impact Assessment It is recommended to perform an impact assessment in relation to anchor operations and discharges and spreading of drill cuttings and mud.


Optional or mandatory


Drilling plan


A plan describing the drilling operation, volumes of mud and cuttings expected, duration for each section, location and more.

Map showing potential coral structures


This kind of map is normally based on sonar data and interpreted by qualified personnel in order to point out potential coral structures.

Coral survey data


Data confirming the presence of corals, coral condition, coral species and distribution. Such data are not available from sonar data (map) only. These data make it possible to distinguish coral structures which will strengthen the risk assessment.

Current data


Important data in order to as good as possible assess the current regime at a given location which is important with regards to spreading of discharges.

Modelled dispersion plume


A modelled plume gives an overview of dispersion and sedimentation rates which are essential when assessing possible impacts inflicted upon CWC. Should be based on input from current measurements from the location if possible. If not available, one has to refer to experiences from similar operations.

Anchor analysis


Location of anchor, anchor chains, pennant wires etc. A description of pre lying, pick up and more. These are important data in order to assess the risk inflicted upon CWC with regards to anchoring.

Noise pollution analysis


Acoustic modelling and measurements analysing possible impact on sensitive species like fish and marine mammals from drilling and seismic activities.

The risk assessment should be used as decision support with regards to drilling location, discharges of drill cuttings and sediment, location of anchors, anchor chains, pennant wires, pipeline routing etc. By systematically evaluating the risk inflicted upon corals or other fauna in an exploration area, operators can plan for exploration drilling with the lowest possible environmental impact. Also, by working out an overall risk picture it’s easier to tailor the monitoring program, focusing on those coral structures/ habitats that may be at risk. To perform an impact assess­ment, it is important to have proper background data. Dispersion modelling of drill cuttings Drill cuttings and drilling fluids may affect sensitive habitats by an increased sedimentation and particle exposure. The positioning of the well and the deposit site is therefore important. Calculating the particle

dispersion depending on the currents and finding the least harmful area to deposit drill cuttings is recommended. Deposition can be made far away from the well using e.g. a CTS (Cuttings Transport System). If it is impossible to secure the safety of the sensitive habitats, it could be necessary to bring the cutting residues back to the rig for alternative disposal. Anchor and mooring handling Corals and sponges are especially sensitive to the mechanical disturbances that anchor and mooring handling inflict. The mandatory anchor and mooring analysis should consider corals and other protected habitats when planning for positioning and handling, e.g. a “best fit analysis” calculating the best anchor line positions in order to avoid coral damage. Pipe laying Laying and maintaining pipes have a relatively large local environmental impact. The biggest risks to sen-

Drilling in sensitive areas Oil & Gas 17

An environmental resources map (coral condition from interpretation of SSS mosaic and visual mapping).

Deposition distances for discharges given in mm (based on imperical data or worst case dispersion modelling).

0.1–1 mm NO > SLIGHTLY


















1–10 mm

50 mm

10–50 mm

Probability plot based on historical current measurements.





25–50% 50–75%







sitive fauna by pipes are physical disturbances and leakage. A risk assessment based on the site survey should present the best route, avoiding sensitive ­areas. Reducing the risk of leakage due to anchor and other physical damages to the pipe is also important mitigating measures. Mitigating measures After the site survey and risk assessment are con ducted, potential measures to mitigate the drilling operations impact on sensitive fauna should be planned. Examples of risk-reducing measures are: © 3DGroundline

■■ CTS (Cuttings Transport System) ■■ DP drilling rig (Dynamic Positioning) ■■ Reduced drill bit size ■■ Onshore disposal of discharges Deposition of discharges from drilling.

18 Oil & Gas Drilling in sensitive areas

ENVIRONMENTAL MONITORING Possible impact on sensitive fauna is documented by monitoring anchor handling and drilling operations. Evaluating status before, during and after operations. Monitoring program When drilling in sensitive areas, it is important to monitor the different effects on the surroundings, before, during and after drilling. Which method and equipment to use depends on the sensitive resources

present and what operations are being conducted. The figure below shows the threats, effects and an overview of monitoring methods and when they are best applied. Details on applicable monitoring methods are given in the table to the right.

Environmental monitoring

Drilling Threats

Effect on sensitive fauna

Monitoring methods


Subsea construction

Pile driving Anchor operations

Smothering by sedimentation

Contamination from chemicals (accidental spills etc)

Physical/ mechanical damage

Turbidity measurements

Hydrocarbon sniffers

ROV visual inspection

Sediment sampling

Passive samplers

ROV inspection

Current measurements



Noise/ vibration impact

Hydrophones Geophones

Current measurements

Sediment traps

Sediment traps

Sediment sampling

Drilling in sensitive areas Oil & Gas 19

Suggested applicable monitoring methods for each of the identified sources with potential of influencing coral communities SAMPLE/ ANALYSES



Sediment traps

Vertical cylinders “trapping” sinking particles in the water column.

Collect particles to be analysed for grain size distribution, barium and other metals. Increased levels will indicate spreading of drill cuttings.

Sediment samples

Core samples which can be cut in various depth intervals, e.g. surface sediments and deeper sediments.

Samples to be analysed for drill cutting constituents, thus ­mapping the spread of drill cuttings.

ROV inspection

Use camera on ROV.

Visual evaluation of the particle dispersion in water and at the seabed. Observe excessive sedimentation. Used in sediment sampling and deployment of equipment.


Sensors measuring the transpar- Indicate particle concentrations in the water to reveal spreading ency of the water, thus indicating of drill cuttings. particle concentrations. The data are stored in the sensor.

Water currents

Sensors measuring water ­currents (velocity and direction). Can be of profiling type ­(measuring in the whole ­water column) or single depth ­measurements.

Passive samplers (DGT etc)

Diffuse Gradients in Thin-film Detects increased consecrations of metals and can be used to (DGT). Passively measures monitor the discharge of metals from drilling operations. ­dissolved and particularly bound metals in the water over time.

Hydrophones/ geophones

Sensors measuring sound waves and vibrations.

Gives the main current direction and velocity at certain depths for a period of time. Main parameter regarding expected direction of dispersion, and when deciding where to place the measuring equipment/sampling stations.

Obtains data on possible noise pollution and impact from ­tremors and vibrations through the seabed.

20 Oil & Gas Drilling in sensitive areas

Drilling in sensitive areas Oil & Gas 21

With rising pressure on the ocean’s resources, demands on minimal environmental impact solutions are increasing. DNV GL assists the offshore industry in improving its drilling operations and environmental performance.

References Bett, B.J., & Rice, A.L. 1992. The influence of hexactinellid sponge (Pheronema carpenteri) spicules on the patchy distribution of macrobenthos in the Porcupine Seabight (bathyal NE Atlantic). Ophelia 36 (3): 217-226. Davies AJ, Wisshak M, Orr JC, Roberts JM. 2008. Predicting suitable habitat for the cold-water coral Lophelia pertusa (Scleractinia). Deep-Sea Res I 55:1048–1062 Dodds LA, Roberts JM, Taylor AC, Marubini. 2007. Metabolic tolerance of the cold-water coral Lophelia pertusa (Scleractinia) to temperature and dissolved oxygen change. J Exp Mar Biol Ecol 349:205–214 Fosså, J.H., P.B. Mortensen and D.M. Furevik. 2002. The deep-water coral Lophelia pertusa in Norwegian waters; distribution and fishery impacts. Hydrobiologia 417:1-12. Freiwald A, Fosså JH, Grehan A, Koslow T, Roberts JM. 2004. Coldwater coral reefs. UNEP-WCMC, Cambridge Holland G. J., Greenstreet S., Gibb I., Fraser H., Robertson M., 2005. Identifying sandeel Ammodytes marinus sediment habitat preferences in the marine environment. Mar Ecol Prog Ser 303: 269-282. Kålås, J.A., Viken, Å., Henriksen, S. and Skjelseth, S. (eds.) 2010. The 2010 Norwegian Red List for Species. Norwegian Biodiversity Information Centre, Norway.

OSPAR. 2008a. OSPAR Convention for the Protection of the Marine Environment of the North-East Atlantic. OSPAR List of Threatened and/or Declining Species and Habitats. (Reference Number: 2008-6) OSPAR, 2008b. OSPAR Convention for the Protection of the Marine Environment of the North-East Atlantic. Descriptions of Habitats on the OSPAR List of Threatened and/or Declining Species and Habitats (Reference Number: 2008-7, Replaces agreement 2004-7). OSPAR, 2010. Background Document for Deep-sea Sponge Aggregations. OSPAR Commission Biodiversity Series. Norsk Standard, 2012. Water quality – Visual seabed surveys using remotely operated and/or towed observation gear for collection of environmental data. NS-EN 16260:2012. Lindgaard, A. og Henriksen, S. (red.) 2011. Norsk rødliste for naturtyper 2011. Artsdatabanken, Trondheim. Wright, P.J., Jensen H, Tuck I., 2000. The influence of sediment type on the distribution of the Lesser Sand Eel, Ammodytes marinus. J. Sea Res 44:243–256. Havmiljø.no

22 Oil & Gas Drilling in sensitive areas


■■ Oil spill preparedness and response

■■ Environmental impact assessment

■■ Oil drift modelling (OSCAR)

■■ Coral/sponge risk assessment

■■ Environmental technology and engineering

■■ Drill cuttings dispersion modelling

■■ Well risk assessment

■■ Environmental monitoring

■■ Offshore leak detection systems advisory

■■ Environmental modelling and GIS

■■ Third party reviews

■■ Oil spill contingency services

Drilling in sensitive areas Oil & Gas 23

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Drilling in sensitive areas  

A DNV GL guideline for “best practices” keeping focus on the seabed environment

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