On behalf of the operators on the Norwegian Continental Shelf, the Norwegian Clean Seas Association for Operating Companies (NOFO) has the responsibility for providing a documented and verified level of oil spill response, fulfilling the requirements set by the regulatory authorities for each individual production and exploration activity. To meet this responsibility and document the established oil spill preparedness, a comprehensive and cross-disciplinary project has been undertaken, integrating results and lessons learned from oil on water exercises and test facilities in the period 1985 to 2018. The structured results feed into standardized algorithms for system capability and operational windows, applicable across all combat methods in the NOFO toolbox. Through gap and sensitivity assessments, topics for R & D area prioritisation are identified. Data and information are structured in order to fit into the assessment methodology for Environmental Risk Assessments (ERA) and Spill Impact Mitigation Assessments (SIMA), and a step by step methodology for oil spill response assessments (OSRA) was developed as part of the project, facilitating standardised and comparable oil spill response plans. In addition to this standardisation and documentation process, templates for presentation of key data for oil spill response planning purposes are developed, and disseminated to a dedicated web site, as well as the NOFO Common Operating Picture GIS. In this way, a cohesive set of data and standards are available for use in assessments, planning, authority assessment and in incidents.
There is a high level of E & P activity on the Norwegian Continental Shelf (NCS), with 566 production licences, 83 oil and gas fields in production and extensive exploration drilling. New license awards are to some extent in environmentally sensitive areas, including nearshore and in the Arctic. According to Norwegian legislation, environmental risk and oil spill contingency assessment are mandatory elements in Applications for Activities, and reports are available to stakeholders and the general public for review. Oil spill response is a key risk reducing measure in the case of major spill events, but the capacity and effectiveness has been a matter of widely diverging opinions. This has resulted in drawn out permit processes, as well as assessments of relatively similar E& P activities concluding with significantly different oil spill response requirements. The uncertainties also affected the process of developing environmental management plans for the NCS.
In 2017, Norwegian environmental authorities challenged the industry to achieve standardisation of approaches with documentation of capacities and assumptions to be used in assessments and planning. As a result, the Norwegian Clean Seas Association for Operating Companies (NOFO) initiated a major project, the results of which are now organised and available through a web interface.
Organisation and process
Organisation and structuring of spill response information for the NCS started in 1999, at a regional level (Skeie et al., 2000). In 2017, the expectations and requirements in terms of detail and documentation had increased significantly. To ensure a comprehensive approach that included all relevant issues, a working group was established that included specialists from the three major operators on the NCS, in addition to key personnel from NOFO. From an initial development of a mind map of elements to be addressed and their interconnections, the group systematically addressed and reviewed each individual issue. As the process also would need to meet the expectations and requirements of the Norwegian Environmental Agency (NEA), being the regulatory authority, the group undertook a series of meetings with the Norwegian Environmental Agency (NEA), in an iterative process starting with the general approach and ending with the results and findings. In a parallel iterative process, the Norwegian operator's technical forum for oil spill preparedness and the NOFO General Assembly was informed and consulted.
Operation cycle and performance
A key element in the early phase was to develop a framework for identifying parameters for which information and documentation was needed. Based on the overarching principle of 5 barriers, from operations near the spill sources to shoreline clean-up (Figure 1), this was addressed in the form of an operation cycle, to derive a daily performance in terms of combat of oil emulsion given a continuous operation (Figure 2). The framework assumes resources have been mobilised (location dependent) and includes a) active combat (recovery/application of dispersant), b) preparation for transfer/refill, c) transfer of recovered emulsion/refill of chemical dispersant and d) preparation for resuming active combat.
The optimal performance of a response unit is dependent on technical and logistical aspects, and includes the following elements:
K = Capacity during active combat (m3 oil emulsion/h).
L = Storage capacity of recovered emulsion/amount of chemical dispersant.
D = Sum of transfer/refill and preparation (h/d).
The in-field performance of a response unit depends on a range of environmental factors varying between locations and time of year, including:
Tb = Fraction of time when wind and wave conditions allow operation
Ts = Fraction of time when light and visibility allow operations (operational light)
Eo = Efficiency within the operation window given by wind and waves in operational light
Em = Efficiency in reduced visibility and darkness compared to efficiency in operational light
Et = Reduction factor due to cold conditions
Ek = Reduction factor between barriers
Ei = Reduction factor due to sea ice
Te = Encounter rate of oil
A response unit has a limit for performance (Es) given as:
Es = ((Eo*(Ts*Tb))+((1−(Ts*Tb))*Em))*Ei*Et
Applying the above parameters, a response unit has an in field performance (Ys) in m3 oil emulsion per day given as:
Ys = (K * (24 – D)) * Es*Te
The process of defining the operations cycle and the elements included in deriving optimal and in field performance served to focus the further process on which parameters to retrieve information on. Key parameters include:
- Effectiveness of recovery/boom leakage
- Effectiveness of applying chemical dispersants
- Water cut in skimmers
- Pumping rates for skimmers at different viscosities
- Pumping rates in transfer operations
- Time needed for at sea transfer operations
Sources for documentation
NOFO has conducted oil on water exercises (Kristoffersen, 2012) since 1985. The reports from these studies were the primary source for information. These were retrieved from external archives and perused to extract quantitative information on the required parameters as well as supporting information.
A review of the extracted information by the working group led to search for additional information in external reports, peer reviewed literature and vendor specifications, and also instigation of test activities to provide additional information where gaps or uncertainties were identified (Figure 3).
As documentation data on the individual parameters would need to be put into context, in terms of environmental (wind, waves, light etc.) and test conditions, a database structure was established to incorporate such information, also allowing future information to be entered in a structured and easily searchable format.
Weathering studies are a mandatory requirement for crude oils on the NCS. NOFO early developed standards for reporting parameters from these tests, stored as individual MS Excel files. To increase the potential for review and assessment across the NCS, data for the more than 100 crude oils were merged into one single database.
A key issue for the NEA was to have access to 24/7 updated specific information on Oil Recovery vessels, combat capability and dispersant stockpile location. This led to development of an interface that allowed excerpts of data from NOFO internal systems to be available to Authorities and the general public.
Visualisation and dissemination
It was agreed in the early phase of the process that the results should be available through a web interface, and open to the general public, thus providing 100 % transparency. This interface was developed step by step throughout the project, for review by the project group.
Review of data
Recovery: Data were available from 55 Oil on Water exercises involving tests of recovery of oil, under conditions of significant wave height (Hs) between 0.5 and 3.5 m, wind conditions ranging from 2 to 23 m/s, with oil and emulsions ranging from 100 to 8800 cP. Under these conditions, recovery efficiency varied from 57 to 100 %.
Dispersant application: These aspects had a focus in the years 1994 to 2012 and were addressed under 6 Oil on Water exercises conducted under wave conditions of 1 to 2.5 m Hs, and wind conditions up to 12 m/s. Effectiveness of dispersants were up to 95 %, based on visual estimates.
Water cut: This was addressed in 11 mesoscale tests and Oil on Water exercises in the period 1987 to 2018, under wave conditions 0.5 to 2 m Hs and wind conditions from 2 to 20 m/s. Water cut varied from 0 to 39 %.
Pumping rate: This was addressed in 51 tests and Oil on Water exercises in the period 1987 to 2018, on fluids ranging from 1 to 137 000 cP.
Reviewing these data, it was concluded that mechanical recovery could be quite efficient even at low viscosities (< 1000 cP), that water cut was significantly improved through development, that viscosities of most NCS crudes did not significantly affect pumping rates, that effective remote sensing was a requirement in daytime as well as night time, that improved logistics would significantly increase the capability of applying chemical dispersants, and that reducing the transfer time of recovered oil would significantly improve the performance of offshore mechanical recovery.
Performance of oil spill response units
Based on the data review, operation cycle and performance parameters, oil spill response units were grouped according to their operational windows:
Group 1: These comprise offshore ship-based units, equipped according to NOFO standards, with a capability of mechanical recovery as well as surface application of chemical dispersants. These units may operate in 0 to 4 m significant wave height, equivalent to wind speeds up to 15 m/s, and are not dependent on operational light or visibility, as they have remote sensing equipment onboard.
Group 2: These are ship-based units targeted for nearshore operations, the majority being fishing vessels with the required certificates and training. The window of operation for these units is up to 1.5 m significant wave height, wind speeds up to 10 m/s, and more than 1000 m horizontal visibility. Provided support by ship- or airborne remote sensing resources, operations do not rely on daylight.
Optimal performance of these units given as combat of oil-in-water emulsion ranged from 40 to 2 800 m3/d. Considering the reduction factors caused by environmental conditions, the in-field performance for offshore systems were reduced by approximately 70 % in mid-winter and 30 % in mid-summer, depending on local conditions (Figure 4).
The dimensioning event for oil spill response on the Norwegian Continental Shelf is loss of well control, with a discharge over a number of days. Developing a formula for an operational cycle allows for including the different aspects and activities involved in a continuous operation over time. Taking a vessel according to the NOFO 2009 standard, with a Transrec 150 weir skimmer, operating in Barrier 1, we have the following values:
K (Capacity during active combat (m3 oil emulsion/h)): 365 m3
L (Storage capacity of recovered emulsion): 1500 m3
D (Sum of transfer/refill and preparation (h/d): 8 h per operation
Te (Encounter rate of oil): 1
Taking these into the formula, we arrive at an optimal performance of a recovery of 2 865 m3 oil emulsion per day.
If this unit were to operate in the Northern North Sea (the Statfjord area) in the winter season (December to February), we have the values:
Tb (Fraction of time when wind and wave conditions allow operation): 0.55
Eo (Efficiency within the operation window given by wind and waves in operational light): 67 %
This gives an in field performance for this unit in this area and season of 1 060 m3 recovered emulsion per day.
Presenting the results
While deriving optimal and in field performance of the oil spill response units were one of the key objectives of the project, the results needed to be put into a context of spill response assessments and planning, as well supported by standardised data to provide location and time specific environmental information. The web interface (http://www.nofo.no/planverk) (Figure 5) was developed to provide such information in a structured manner. Below, the key elements are briefly presented.
Standards and Methods: This heading provides links to relevant Norwegian Oil and Gas guidelines. Also, to BarKal, an Excel based model for determining spill response requirements for a given activity, applying location specific in field performance and organised data from weathering studies of crude oils. This heading also provides guidance and documentation of an approach to operative Spill Impact Mitigation Assessments (SIMA) (IPIECA, 2017) (Figure 6).
Prerequisites: This heading defines the overarching principles of barriers, and also guidance regarding strategies for different release scenarios. Here is also found descriptions and illustrations of the different types of NOFO oil spill response units. Details of the operation cycle and parameters involved in determining in field performance are also given here, as well as quantitative information on optimal performance of the different units in barriers 1 (near the source) through 3 (nearshore). Information on mobilisation time, transit speed and response times for all resources are also presented here.
Data sets: This heading provides strategic environmental response plans (Spikkerud et al., 2011) and high-resolution thematic maps for > 30 key areas for oil spill response planning along the Norwegian coast, including shoreline ESI (Petersen et al., 2019) maps. Also, links to data sets on sites of high priority for protection by the Norwegian Environmental Agency are given. Here is also provided links to the NOFO Common Operating Picture (COP) (Fiksdal, 2017), where data on environmental parameters (met.no, 2018), operational window and in field performance are available for the entire NCS, on the same 10 by 10 km grid applied in environmental risk assessments (Figure 7). This part of the web site also provides key spill response information in “at a glance” sheets (Figure 8), including chemical dispersibility, explosion hazard and applicability of different skimmer types. Here is also access to excerpts of information on mass balance and other characteristics of Norwegian crude oils, as well as downloads of the entire database on oil and emulsion properties over time (Figure 9).
Resources and capabilities: This heading provides exhaustive information on NOFO resources, including response units, bases and depots, vessels, remote sensing units, personnel and environmental surveys. For the most critical information, data are provided in real time from NOFOś internal systems. This part also provides links to the Norwegian Coastal Administration oil spill response resources, available to Norwegian operators through agreements with NOFO.
Quality assurance: This heading provides full information on all reports and documentation reviewed and applied in deriving optimal and in field performance, in a searchable database format. All reports are stored in a digital format in NOFO′s internal document system. This part of the site specifies the update frequency and process.
How to use: As the entire system is comprehensive, and as there is a wide range of user groups, this heading contains “paths” for easily retrieving key information relevant for various user groups, including Authorities, operators, stakeholders and consultants.
References: This heading provides links to rules and regulations, as well as a database on standardised terms to be used in the Norwegian oil spill response community.
Operative plan: This heading is for the use of operative personnel, describing notification and information procedures, tactics and operation manuals for equipment and units.
Where there is a lack of data, opinions flourish, and when diverging opinions form the basis for seemingly standardised and semi-quantitative assessments, the analysed oil spill response requirements for relatively similar activities naturally diverged. This observation from the NEA was a key incentive in starting the project.
Although quantitative information on capacities and performance of individual components of oil spill response (e.g. pumping rate of a skimmer at different viscosities) are valuable, the variability in terms of location, release characteristics, environmental conditions, unit configurations and encounter rate preclude the systematic testing of all possible combinations.
Our approach was to extract data from tests in the field under oil on water exercises, mesoscale testing of equipment under standard configurations, and put these into the context of release and environmental conditions. Although fully realising that this does not provide a fully exhaustive data set on spill response performance, it does provide a platform for achieving a consensus of the current status. In an R&D context it has provided valuable insight in what elements of the operation cycle where improvements will have the highest impact on improved performance, including logistical and technological improvements. By providing full insight in the data reviewed and the conclusions drawn from these data, feedback and concerns from authorities and stakeholders now are more focussed, allowing the oil spill response community to address these in a specific manner.
By integrating these findings in deriving standardised optimal and in field performance characteristics, and further provide a methodology for assessments, standardised assessments are made possible. This is supported by developing standardised data sets on all parameters used in oil spill response assessments, ranging from oil properties through wind and wave conditions to environmental priority sites. Use of information has been the topic of several courses and are also the topic of e-learning elements, available on the web site.
Lessons learned for future training and exercises, as well as R&D are to invest intellectual efforts in defining what data to extract from the activities planned, and to make sure that these are consistently followed through implementation and subsequent incorporation in the databases established through the project. Further – to ensure update of performance parameters over time.
Feedback from parties involved in the process is a generally increased understanding of oil spill response issues, finding its way into more standardised and comparable oil spill response assessments and evaluations. Authorities find it easier to assess exploration and production applications, reducing the timeline and processes involved in obtaining permits. By providing a wealth of information and data through the web site, assessment reports now to a large extent refer to the web site, reducing the volume and increase the readability of the reports.
Oil spills may have different characteristics in terms of oil type, rate, duration and release depth. Potential environmental impact and performance of oil spill response will further depend on a range of factors, including location, time of year, temperature, wind, waves and ocean currents. This wide range does not preclude a systematic approach to documentation and planning of adequate oil spill response and establishing standard methods and approaches. By transparent presentation of the data used in deriving oil spill response performance, stakeholder and authority concerns may be focussed and addressed in a constructive way, while also providing input to R&D activities. Standardisation of methodology and data allows for improved comparability between activities, as well as evaluation of spill response alternatives in a SIMA context.
Lessons learned from this work include:
a) Developing a set of parameters and a formula for performance over an operational cycle allows for identification of which factors should be focussed on for an overall performance improvement.
b) Developing an overall architecture on what data to collect from all activities (including tests, exercises and training) increases the awareness of the value of documentation and provides robustness in an audit and quality control context.
c) Designing data templates for tests and exercises so that they provide information in an operational cycle context increases the quality and credibility of optimal and in field performance, which forms the basis for oil spill response requirements on the NCS.
d) During tests and exercises, data need to be recorded according to the templates agreed upon, and focus should be kept on storing the results according to the overall data architecture.
e) Even simple tests and exercises benefit from a review of what parameters are relevant for recording, to provide documentation and a basis for periodic reviews of potential for improvement and development.
f) By applying a fully transparent and openly available approach and documentation, a consensus may be reached on key aspects of oil spill response, and issues where there are disagreements may be addressed in a focussed manner.
Finally, having a small, dedicated and technically competent working group, staying the course over a three-year period made it possible to keep track of and put in context the many issues involved. Extensive outreach and consultations with authorities and operators allowed for a common understanding and providing transparency by publishing all resulting data on an open web site has been seen as positive by operators, authorities, contractors and stakeholders.