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Drill Cuttings in the Barents Sea and their Environmental Footprint. A Visual Assessment of the Seabed Condition

Bachelor Thesis 2016 70 Pages

Environmental Sciences

Excerpt

Contents

List of Abbreviations

List of Figures

List of Tables

1 Introduction
1.1 Problem statement and objectives
1.2 The history of the oil exploration in the Barents Sea . .
1.3 Environmental impact of drill cuttings
1.4 Description of the projects BARCUT and Petromaks II .
1.5 Summary of objectives

2 Theoretical background
2.1 Study area
2.2 Thematic definitions
2.2.1 Drill cuttings
2.2.2 ROV
2.2.3 Underwater hyper-spectral imaging
2.2.4 Grab sampling
2.2.5 Core sampling
2.3 Survey design

3 Methodology
3.1 Available data
3.1.1 Video survey
3.1.2 UHI survey
3.1.3 Grab sampling
3.1.4 Core sampling
3.2 Data analysis
3.2.1 Analysis of video data
3.2.2 Comparison with available data

4 Results and discussion
4.1 Video survey results
4.2 Comparison with existing data
4.2.1 UHI technology
4.2.2 Macrofaunal assessment
4.3 Comparison with previous investigations
4.4 Prospect
4.4.1 Autonomous Underwater Vehicle

5 Conclusions

6 Summary

List of References

A Appendix

List of Abbreviations

illustration not visible in this excerpt

List of Figures

1.1 The history of the well exploration in the Barents Sea

2.1 Study area of the examined drilling sites

2.2 How drill cuttings emerge

2.3 Different appearances of drill cuttings

2.4 Magnified drill cuttings

2.5 Necessary devices for a marine sediment surface sampling campaign

2.6 Locations of the sampling campaign for the BARCUT project

3.1 Blurred view of the marine sediment surface

3.2 Necessary devices for a UHI sampling campaign and the generated UHI output

3.3 Grab station positions

3.4 Grab sampling procedure

3.5 Core sampling procedure

3.6 Sediment conditions of by drill cuttings smothered areas

3.7 Sediment conditions of areas of visible deposition of drill cuttings .

3.8 Sediment conditions of transition zones

3.9 Sediment conditions of areas of no visible deposition of drill cuttings .

3.10 Spotted organisms on the video transects of the seabed in the south- western Barents Sea in September 2015

3.11 Example of correlation images from the UHI results

3.12 An extract of a taxon list

4.1 The directions of the surface water currents in the Barents Sea

4.2 Results of the visual sediment surface analysis of the drilling site GF 2015 in the south-western Barents Sea in September 2015

4.3 Results of the visual sediment surface analysis of the drilling site GI 2015 in the south-western Barents Sea in September 2015

4.4 Results of the visual sediment surface analysis of the drilling site G 2000 in the south-western Barents Sea in September 2015

4.5 Trace of an anchor

4.6 Results of the visual sediment surface analysis of the drilling site S 2012 in the south-western Barents Sea in September 2015

4.7 Results of the visual sediment surface analysis of the drilling site E 1991 in the south-western Barents Sea in September 2015

4.8 Results of the visual sediment surface analysis of the drilling site T 1987 in the south-western Barents Sea in September 2015

4.9 Comparison of the sediment condition results of the visual assessment to the UHI analysis

4.10 Comparison of the sediment condition results of the visual assessment to the UHI analysis

4.11 Comparison of the spotted organism results of the visual assessment to the UHI analysis

4.12 Comparison of the results of the visual assessment to the macrofaunal assessment of drilling site GF 2015 in September 2015

4.13 Sediment conditions at two grab/core stations at drilling site GF 2015 in September 2015

4.14 Comparison of the results of the visual assessment to the macrofaunal assessment of drilling site GI 2015 in September 2015

4.15 Comparison of the results of the visual assessment to the macrofaunal assessment of drilling site G 2000 in September 2015

4.16 Comparison of the results of the visual assessment to the macrofaunal assessment of drilling site S 2012 in September 2015

4.17 Comparison of the results of the visual assessment to the macrofaunal assessment of drilling site E 1991 in September 2015

4.18 Comparison of the results of the visual assessment to the macrofaunal assessment of drilling site T 1987 in September 2015

4.19 Sediment condition at 30 m from the drill hole at drilling site T 1987 in September 2015

4.20 An illustration of the different flight patterns of an AUV

List of Tables

3.1 Classification of the four different sediment condition categories

4.1 List of age categories of the investigated drilling sites

4.2 Visual assessment: spatial extent of impacts of drill cuttings on the surrounded sediment of the investigated oil-well bores

4.3 Results of the visual assessment validated with the results of the macrofaunal assessment of the spatial extent of impacts of drill cut- tings on sediments around four different drilling locations

5.1 Pros and cons of the three different assessment techniques: video survey, UHI survey and macrofaunal assessment

A.1 Positions of grab stations of investigated drilling sites i

A.2 Positions of core stations of investigated drilling sites i

A.3 Details about the six investigated oil-well bores ii

Abstract

The centre of interest for this Bachelor thesis is the visual assessment of drill cuttings at the sea floor around oil and gas drilling locations in the Barents Sea. The purpose is to detect the spatial extent of impacts on the sediments. In order to validate the reliability of visual assessments, the method is compared to the results of benthic macrofaunal analysis, which are an approved indicator of sea-floor assessments. The results of the visual assessment are also compared with Underwater Hyper-spectral Imaging (UHI), which is a tool under development for sea-floor assessments.

In September 2015 six drilling sites of different age categories were investigated: recent (less than 8 weeks, post-drill), average (3 to 15 years) and old (more than 20 years). Video transects were carried out, and grab and core samples were obtained by a Remotely Operated underwater Vehicle (ROV). For sampling the UHI transects a push-broom scanner was attached to the ROV. The visual inspection of the video transects was recorded in a log file and plotted onto a geographical map.

As a result of the different assessments the spatial extent of the impact of drill cuttings is for old (drilled before 1993’s prohibition of discharging drill cuttings containing more than 1 % of oil) drilling sites of maximal 125 m, for average drilling sites of maximal 60 m and for recently drilled sites of maximal 250 m from the drill hole.

In general, the visual assessment was mostly reliable (variance of about 10 m) to detect the spatial extent of impacts of drill cuttings. However, for locations drilled before 1993 the variance was higher, because natural sedimentation had occurred during the intervening period, and so the sediment surface did not always show the impacts which remained below the surface of the habitat. Thus visual assessments can be regarded as reliable for capturing visible depositions of drill cuttings, but at older sites additional validation will be needed to assess the full spatial extent of disturbance. The UHI analysis detects differences in a set of pre-defined categories of the surface sediment conditions, but the necessary software is still in development and not yet fully operational.

Outline

Introduction

The motivation behind the thesis work, the history of oil exploration in the Barents Sea and an introduction to the environmental impact of drill cuttings are presented. The two involved projects of the work are described. Also, a depiction of the structure of the thesis is given.

Theoretical background

For the geographical classification a brief depiction of the study area is given. Further the different thematic definitions (drill cuttings, ROV, UHI, grab sampling) are explained. A survey design displays the choice of the investigated oil-well bores as well as the arrangement of the 4-lines-investigation-pattern.

Methodology

First, the sampling campaign methods are listed. Starting with the video transects through to the hyper-spectral imaging and lining up with the grab samples. They are followed by an explanation of the data analysis of each of them.

Results

The results of the different assessment techniques are presented and compared. The main focus of interest is the visual analysis of the video transects obtained by ROV.

Conclusions

The results of the presented work are interpreted and the main findings are sum- marised.

Acknowledgments

This study has been carried out with data kindly supplied by Eni Norge, within the research project Barents Sea drill cuttings research initiative (BARCUT) led by University of Tromsø, and Akvaplan-niva as work package leader. Further collabo- ration was carried out with Ecotone AS, Trondheim, Norway, within a Norwegian Research Council Petromaks II joint industry-funded project for developing UHI techniques.

My sincere thanks to my supervisor in Norway, Sabine J. K. Cochrane, for giving me the opportunity to gain this enriching experience and for providing me with all the necessary facilities. I am grateful for her encouraging guidance, her open and welcoming nature and her valuable knowledge which she shared with me. I also thank Stefan Ekehaug for collaboration with UHI data.

I also would like to express my gratitude to my two supervisors in Germany Prof. Dr.-Ing. O. Reul, University of Kassel, Department of Geotechnical Engineering and Prof. Dr. M. Gaßmann, University of Kassel, Department of Water Quality Management Modelling and Simulation, for their constant guidance.

Moreover I would extend my gratitude to my dear friend Sulabh Tiwari for valuable feedback and support in writing this report without which this report would not have been existed in its present form.

I take this opportunity to record my sincere thanks to my parents and friends for their unceasing encouragement and support.

Chapter 1 Introduction

1.1 Problem statement and objectives

During the past few decades oil and gas exploration in the Norwegian part of the Arctic has gained increasing momentum. Petroleum activities in the Arctic pro- vokes political debate, mostly due to the risk of accidental discharges in potentially sensitive habitats. Cold temperatures and proximity to ice requires extra safety measures to reduce risks. At the sea-floor, drilling causes the deposition of drill cut- tings, which can give rise to localized disturbances to the bottom-living, or benthic fauna [[Gray, 2015]].

The Norwegian government requires that a baseline survey is carried out at the sea floor in advance of exploratory drilling, and at production sites, follow-up mon- itoring is carried out every three years (coordinated across specified geographical regions) [[The petroleum sector on the Norwegian Continental Shelf, 2011]]. Tradi- tionally, physical samples of sea-floor sediments were, and still are, collected using grabbing and/or coring devices. The content of petroleum compounds and heavy metals are analysed, and interpreted against known background values and calcu- lated levels of significant contamination (LSC). The small benthic organisms living on and in the sediment are collected and the community composition used as an indicator of sediment disturbance. However, these methods are time-consuming and labour-intensive. With increasing availability of technology, new survey techniques are in demand, such as visual assessment using ROVs, and automated image recog- nition (such as using UHI). Before adopting new methods, it is important to conduct validation and comparison with existing techniques to assess compatibility and re- liability.

This bachelor thesis has its main focus on visual assessment of the spatial extent of spreading of drill cuttings around six drilling locations in the south-western part of the Barents Sea. The objective is to quantify the environmental footprint of the drilling events on the sea-floor around the drilling location. Thus this work specif- ically documents the visually detectable extent of the affected area, using video footage obtained by ROV. In order to validate the reliability of the visual assess- ment, it is compared to the macrofaunal analyses conducted at the same survey areas, which are an internationally approved assessment technique. ROV and fau- nal data are used with permission from Eni Norge and Akvaplan-niva.

Because the human eye has a limited range of colour recognition, and both natu- ral sediment and drill cuttings are brown in colour, a trained biologist will use a range of indicators to help distinguish areas of artificial deposition from natural sed- iments. The question arises whether a biologist’s subjective assessment is reliable enough to use for environmental surveillance. The visual assessment was therefore compared with underwater hyperspectral imagery (UHI) data, collected along the same transects as the video material (Ecotone AS data; by kind permission).

1.2 The history of the oil exploration in the Bar-ents Sea

The first exploratory drilling event in the Barents Sea was carried out in 1980. Over the past decades more and more locations were drilled over a slow development (see Figure 1.1). Until 1985 each year more locations were drilled. Within those five years the number of drilled sites per year increased from 2 to 8. In 1986 4 sites and in 1987 only 3 sites were drilled. The number raised again in 1988 to 6 drilled wells in the Barents Sea. The following three years the oil and gas exploration decreased again to 2 drilled locations per year in 1991. In 1992 two more sites were drilled than the year before. As it was prohibited to discharge drill cuttings containing more than 1% of oil after 1993 [[Research Council of Norway, 2012]], the oil exploration activ- ity paused until the new millennium started. Another reason for the interruption of the oil and gas exploration was the ‘zero discharge’ goal implemented in the White Paper 58 in 1996/1997 [[Iversen et al., 2015]]. For two years new wells followed. Nevertheless, the oil exploration in the Barents Sea had to face another change in the regime. In 2003 the ‘zero discharge policy’ was “refined to mean zero discharge of environmentally hazardous substances, using Best Available Techniques, and fol- lowing the precautionary principle (White Paper 25, 2002/2003)”, [Iversen et al., 2015]. Hence in 2003 and 2004 no new locations were drilled. From 2005 on the oil and gas exploration increased again, until 2010 when not a single site was drilled. Since the agreement of the end of the maritime delimitation in the Barents Sea be- tween Russia and Norway in April 2010 [[Moe et al., 2011]; [Government of Norway, 2015]], the number of exploration wells is growing abundantly. The new available area in the Barents Sea allowed both parties to increase the oil and gas exploration. Thus the Norwegian government decided to open the south-east Barents Sea for oil and gas activities in 2013 [[Norwegian Ministry of Petroleum and Energy, 2013]].

illustration not visible in this excerpt

Figure 1.1: The history of the well exploration in the Barents Sea

This figure presents the number of wells drilled in the Barents Sea from 1980 to 2016. Data source: [Norwegian Petroleum Directorate, 2016]

1.3 Environmental impact of drill cuttings

With the increase in drilling activities in the south-western Barents Sea in recent years, the amount of emerging drill cuttings increased likewise. Accordingly, it is of major importance to monitor the environmental footprint of those. So, what exactly happens to a drill cuttings affected area?

Drill cuttings smother the seabed of the affected area and change the sediment com- position once released to the sea. The top layer of the influenced sediment consists of deposited material and turns a natural heterogeneous sediment composition into a homogeneous condition. Signs of life from benthic or burrowing organisms are mostly absent in smothered areas. Thus, released drill cuttings make it difficult for the benthic and burrowing organisms to survive (see chapter 2.2.1 for more details of drill cuttings).

Hence it is important to detect the spatial extent of the affected area around a drill hole that is smothered by those drill cuttings. A reliable and cost-efficient assess- ment will help to locate this spatial extent of the environmental footprint of drill cuttings, in order to take responsible and sustainable decisions in future.

With the increase in drilling activities in the south-western Barents Sea in recent years, decisions need to be made on the appropriate strategy for both drilling fluid used and the optimal waste disposal strategy. Drill cuttings are the particles of sediment and rock which are displaced from the drilling hole, and emerge to the sediment surface. In general, there are four main strategies for disposal of drill cut- tings - 1) simply leave everything on the seabed, 2) leave the ‘top-hole’ section (the upper section of the hole, drilled without casings to line the hole and pump up the cuttings from deeper sections and transport these to land for disposal) or 3) leave top-hole cuttings on the seabed, pump deeper sections to the drilling rig for cleaning, then disperse them at the water surface or 4) employ a ‘cuttings transport system’ where cuttings are transported from the drilling site and deposited elsewhere on the seabed (for example to avoid sensitive areas of seabed, such as coral structures). Many variations on each strategy exist.

The issues surrounding drilling fluids and cost-benefit analyses are complex and will not be discussed further in this thesis. However, the general principles are that oil-based drilling fluids are more efficient in providing optimal drilling conditions inside the hole, and thus less fluid needs to be used. However, deposition of cuttings containing oil-based fluids causes longer-lasting and more extensive environmental impacts on the sea-floor than water-based drilling muds [see [Renaud et al., 2008]], and thus the Norwegian government in later years issued a ban on the deposition of oil-based cuttings. In the Barents Sea the use of oil-based muds is not permitted at all, but in the Norwegian and North seas, it is increasingly used in closed-systems, where the oil compounds are not released into the environment.

The earlier drilling sites investigated in this study were drilled with oil-based drilling muds, and the more recent ones with the water-based equivalent.

1.4 Description of the projects BARCUT and Petro- maks II

The Barents Sea drill cutting research initiative (BARCUT) is a research project entirely financed by the oil company Eni Norge, with a financial framework of 34 million NOK, carried out between 2012 to 2017 [[UiT Tromsø, 2016]]. The Univer- sity of Tromsø is project leader, and Akvaplan-niva is work-package leader. The BARCUT project has the fundamental aim of providing scientific knowledge which will assist in decision-making on optimal waste deposition strategies for drill cuttings in the south-western Barents Sea, with a focus on the Goliat development, where Eni Norge is main operator. Through the project, two field campaigns have been conducted, where biological and geological samples were collected, and in addition has a socio-economic component. This thesis uses biological survey data collected during the BARCUT project. The original work has been detailed re-analysed and a quality assurance of video imagery of the seabed around a number of drilling sites (which was preliminarily analysed in situ in the field) was performed using other existing biological analyses to validate results. An innovative method was developed to display results in a GIS-compatible visual system.

Further collaboration has been conducted within a Joint Industry Project (JIP) within the Research Council of Norway (NFR) Petromaks II programme, where 50 % of funding is from NFR and the remaining 50 % is provided by a consortium of oil and gas operators. A new technology company Ecotone AS is project leader, and Akvaplan-niva is scientific partner. Eni Norge is a late-entry to this consor- tium, which comprises (amongst others) Statoil, Shell, Lundin Norway and others, through the Norwegian Deep Water Programme (NDP). The project is entitled ‘New technology and methods for mapping and monitoring of seabed habitats’ and the main goal is to develop UHI sensor technology for use in habitat mapping and biomonitoring, and to assess its efficiency for commercial use. The project started in 2014 and has a duration of three years. [[Joint Industry Research, Development and Demonstration Project, 2014]]

Ecotone’s patented UHI technology represents a completely new and promising technology for marine identification, mapping and monitoring of objects of inter- est (OOI) at the seabed. Automated and improved classification, higher speed, less human interaction and reduced costs are the main benefits in using Ecotone’s meth- ods. The method is based on the fact that all objects (e.g. geological formations, minerals and organisms) reflect a specific light spectra or optical fingerprint when being illuminated, mainly caused by their chemical composition. By using unique spectral ‘libraries’ containing optical fingerprints of a range of OOI, the UHI sys- tem can automatically identify, map and classify OOI, as Ecotone explains on the website [[Joint Industry Research, Development and Demonstration Project, 2014]].

1.5 Summary of objectives

For reasons of structure and clarity a brief description of the processed tasks in this thesis is presented as follows.

The second chapter contains a theoretical background in order to present a more specific view onto this work. It includes a brief depiction of the study area for a geographical placement, followed by thematic definitions which lead on to a deeper understanding, as well as a description of the survey design. The third chapter describes the methodology used in this thesis, which includes the sampling campaign of the available data and the data analysis. In the fourth chapter the results of the visual assessment are presented and compared with available results of macrofaunal assessments, UHI assessments and previous investigations. The fifth chapter includes the interpretation of the processed results of the presented work. Finally the main findings are summarised in the sixth chapter.

Chapter 2 Theoretical background

2.1 Study area

illustration not visible in this excerpt

Figure 2.1: Study area of the examined drilling sites

The examined drilling sites located in the south-western Barents Sea are shown in red.

The Barents Sea is located north of Norway and Russia. Its borders are marked by the east coast of Svalbard (Norway), the southern archipelago of Franz Josef Land (Russia), the west coast of Novaya Zemlya (Russia), the north coast of Norway, Russia and the Kanin Peninsula (Figure 2.1). The average depth is 230 m and besides that three different water masses influence the Barents Sea: the warmer Atlantic waters, the colder Arctic waters and the warmer coastal waters [[Stiansen and Filin, 2007]]. These currents carry along an important information, as they affect the spatial extent of the impact of drill cuttings on sediment conditions. Throughout this work the study area focusses on the south-western part of the Barents Sea (Figure 2.1).

2.2 Thematic definitions

2.2.1 Drill cuttings

illustration not visible in this excerpt

Figure 2.2: How drill cuttings emerge

1. shows a heap of drill cuttings after drilling into a wall. 2. presents the use of a drilling fluid. 3. illustrates an offshore drilling procedure with emerging drill cuttings. Source: [Cochrane et al., 2016]

What are drill cuttings and how do they look like? When drilling a hole it is well-known that drill dust emerges (No. 1 in Figure 2.2). Additionally the drill’s temperature raises in the course of the drilling procedure. To possibly keep the temperature low it is common to use a cooling fluid (No. 2 in Figure 2.2). Thus, the drill dust is a mixture of the material that was drilled and the cooling fluid. The same understanding can be applied to drill cuttings in the sea (No. 3 in Figure 2.2). Other than at home the drill cuttings cannot be easily hoovered up from the ground. Instead they smother the seabed and change the sediment structure. Further to that the chemical constituents of the cooling fluid might also affect the health of the habitat [Breuer et al., 2004].

Drill cuttings can appear in different aspects. Sometimes they look clayey and sometimes they arise as small dark particles. In Figure 2.3 the first two examples display the clayey aspects of drill cuttings. The third example presents the drill cuttings at one corner of a drill hole. Similar to no. 1 in Figure 2.2 the drill cuttings heap up all around the hole. Drill cuttings in the shape of small particles are shown in the last example. It is very important to identify the various emergences for further investigations.

illustration not visible in this excerpt

Figure 2.3: Different appearances of drill cuttings

1. and 2. are examples of clayey drill cuttings. 3. shows a heap of drill cuttings at a corner of a drill hole. 4. presents an example of particulate drill cuttings. Source: Akvaplan-niva, 2015

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Figure 2.4: Magnified drill cuttings

1. shows a light microscopy of drill cuttings 1300 m below the sea-floor. Source: Akvaplanniva 2. presents the SEM 4200 x magnification of drill cuttings. Source: Tom Eilertsen, University of Tromsø The magnification of drill cuttings, shown in Figure 2.4, illustrates the consistence 9 of different compounds in the emerging mud. The mixture of various sediment layers in addition to the drilling fluid creates the brown colour gradation that is presented in the first part of Figure 2.4. It is approximately 300 times magnified, whereas the second example is magnified 4200 times. This immense magnification reveals the structure of drill cuttings that is particulate and mostly shaped like a cuboid.

2.2.2 ROV

A ROV is a huge (∼ twice the size of a human, see no. 1 in Figure 2.5) vehicle that is used for underwater research. It is controlled by a crew on board of a vessel (see no. 2 in Figure 2.5). Attached with a camera and a robot-arm it is possible to take grab and core samples as well as a video sequence of the seabed. For sampling the grabs and cores it is also necessary to provide additional tools (e.g. a core sample device, see no. 3 in Figure 2.5).

illustration not visible in this excerpt

Figure 2.5: Necessary devices for a marine sediment surface sampling campaign

1. shows an ROV. Source: Akvaplan-niva 2. presents the Njord Viking vessel. Source: Jan Inge Hillesøy, MarineTraffic.com 3. portrays a core sample device. Source: Akvaplan-niva

2.2.3 Underwater hyper-spectral imaging

In contrast to the video sequence of a digital camera the UHI can receive many more wavelength bands than the three discrete colour bands (centred around red, green and blue) and so give more detailed spectral information. It is an underwater push-broom scanner pointed perpendicular (90◦) towards the sea floor and attached to an ROV including a rig of external lights [[Johnsen, 2013]].

2.2.4 Grab sampling

The two previous assessment techniques cover the visual parameter of the analysis, whereas grab samples cover the biological parameter.

Biological investigation gives the necessary information about the habitat condition. How many different species can be detected and how many of them are there? A good habitat condition is defined by the diversity and the abundance of the species. Some species are also a significant indicator for a ‘healthy’ habitat and other species for an ‘unhealthy’ habitat. Nevertheless over this project the macrofaunal analysis works a bit differently. Grab samples are taken at four different stations of different distance from the well hole (30 m, 60 m, 125 m and 250 m). A grab sample over 250 m away from the drill hole is considered as the ‘healthy’ habitat condition. The more a sample differs from that reference sample, the higher is that area affected by drill cuttings. This biological parameter serves as a verification of the results of the visual assessment.

2.2.5 Core sampling

Core samples are used for the geological parameter of the sediment analysis of the seabed condition around the drill hole. When examining the sediment condition visually it is not possible to see the depth of the by drill cuttings smothered area. The visual analysis will classify a thin layer of cultivated sediment as ‘healthy’, although below this layer there might be deposed drill cuttings. That is why it is important to take core samples of the sediment as well. They are taken from different distances of the drill hole using the same specific stations as for the grab samples. This procedure allows to again classify the sediment conditions into different zones which can be used as validation of the results of the visual assessment.

2.3 Survey design

In order to compare different situations to each other, the location of the drilling sites were chosen deliberately (Figure 2.6). Two of these six drilling locations were drilled over twenty years ago (E 1991 and T 1987). The most recently drilled sites were drilled a couple of weeks before (post-drilling) the sampling campaign started (GF 2015 and GI 2015). In between of old and post-drilling sites there are the last two ones that are of average age: S 2012 and G 2000. A detailed table with more information about the investigated drilling locations can be found in the appendix (see Table A.3). Another important reason for this choice was the distance. Not to spend all the budget on driving around needlessly, the drilling sites are quite close to each other as well as not too far away from the departure in Hammerfest.

The procedure of the sampling campaign is well organised to be able to relocate the collected data more easily. As it would take too much time and energy to go through the whole area around a drill hole, it is more wisely to divide it into different sections.

illustration not visible in this excerpt

Figure 2.6: Locations of the sampling campaign for the BARCUT project

The six investigated drilling sites shown in red are located in the south-western Barents Sea north-west from the Hammerfest harbour. Grab and core samples as well as video transects of the sea floor were taken in September 2015.

As shown in the zoom of Figure 2.6 the area is divided into four sections. Each of these sections is represented by one line, although it is not possible to tell what the seabed is like between those lines. However, it is good enough to approximately define the drill cuttings affected area around the drill hole.

[...]

Details

Pages
70
Year
2016
ISBN (eBook)
9783668505841
ISBN (Book)
9783668505858
File size
7.6 MB
Language
English
Catalog Number
v370045
Institution / College
University of Kassel – Akvaplan-niva, Norway
Grade
1,0
Tags
Bohrschlamm Umweltauswirkungen Meeresboden drill cuttings Barents Sea environmental footprint ROV Hyperspectral Imager

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Title: Drill Cuttings in the Barents Sea and their Environmental Footprint. A Visual Assessment of the Seabed Condition