Incident Prevention and Response

This section includes information on the following:

1.   Types of spills and releases from a blowout

2.    Probability of a blowout

3.    Spill trajectory modelling

4.    Managing hazards

         i). Introduction

         ii). Increased Regulatory Expectations Post -Macondo


1) Types of spills and releases from a blowout

In the unlikely event of a blowout occurring while drilling a well, a release of water, brine, natural gas or oil could occur.  By its very nature, the probability of encountering hydrocarbons in an exploratory well is not high.  Should such an event occur, the environmental response techniques would depend strictly upon the type of hydrocarbon that is released.    A blowout involving natural gas would have relatively minor environmental impact.  Should it be light oil, similar to that which was discovered and produced in the Cohasset Panuke project, the oil would float on the ocean surface in a thin layer and breakup / evaporate naturally within hours to days depending on the sea state.  Response techniques to be employed would need to be more robust and varied should medium or heavy grade oil be spilled.  

2) Probability of a Blowout

A detailed analysis of the probability of potential blowouts from offshore exploration wells, taking into account historical international and national spill data, was completed as part of the Environmental Impact Statement filed by Shell Canada Ltd. pursuant to the CEAA 2012 environmental assessment process. 

In the conclusion of the analysis, the estimated probability that a specific individual exploratory well from the Project (with up to seven proposed wells) would have a blowout with an extremely large spill (1.5 million barrels) is once in every 18,392 years (or 0.0055%).  The analysis further identified that only 41% of past blowout events resulted in a release of oil, as opposed to water, brine or gas. Historical information also showed that the majority of well blowouts lasted less than five days.

There have been approximately 50,000 exploratory wells drilled worldwide.  There have been two instances, both in the Gulf of Mexico (in 1979 in Mexican waters and in 2010 in U.S. waters), where a blowout of an exploratory well resulted in a major spill of oil (millions of barrels) into the ocean.  Other past exploratory well blowout events spilled less than 250,000 barrels (39,750 cubic metres) of oil. 

Modelling was also done to estimate the combined probability of a blowout of a Shell Canada exploratory well that would also result in a large volume spill of oil.  Such probabilities are summarized in Table 1 below.  Spill probabilities are commonly expressed as the time required for an event to occur once (Return Period).


Volume (cubic metres)

Probability in Project Time (%)

Return Period (Yrs)

Spill (Site-1) - Blowout

234,000 (1,500,000 barrels)



Spill (Site-2) - Blowout

118,000 (750,000 barrels)



Source: ERC [Environmental Research Consulting]. 2014. Analysis of Potential Blowouts and Spills from Offshore Wells and Activities: Perspectives on Shelburne Basin Venture Exploration Drilling Project. [2014 Jan 17] Prepared by Etkin, D.S. for Shell Canada Limited, Stantec Consulting Ltd., RPS ASA.

3) Spill Trajectory Modelling 

Oil spill fate and trajectory modelling and analyses were performed to help evaluate potential environmental effects of accidental spills and to enable oil spill response planning. Worst-case spill scenarios were conservatively modeled in similar environments and conditions by assuming that no response measures are put in place to minimize or reduce effects.  In the unlikely event of a major spill, oil spill response measures would be used to reduce adverse effects on the environment.  Oil spill containment and recovery and shoreline protection operations would be undertaken to reduce adverse effects to marine and coastal resources and to mitigate the spill’s impacts.  

The use of dispersants would only be considered in cases where a net environmental benefit analysis concludes that it is better for the environment to do so.  By legislation, dispersants cannot be used without the approval of the CNSOPB’s Chief Conservation Officer (CCO), which would only be considered at the time of an event.  The CCO would firstly consult with experts of Environment Canada’s Environmental Emergencies Science Table, which brings together relevant experts in the field of environmental protection, as appropriate, such as response agencies, all levels of government, Aboriginal representatives, local communities, industries, environmental non-government organizations, and academic institutions. Additionally, the CCO is obligated by legislation to consult with appropriate federal and provincial Ministers before granting approval to use a dispersant.    

Shell modelled a worst-case scenario of a 30-day period (with no response measures in place) of oil flow resulting from a blowout event.  Shell has demonstrated that a well would be capped and contained in a shorter time period than 30 days, and as such this modeling is considered to be conservative.  This resulted in the following findings: 

1.  Oil generally travels to the east and northeast of spill sites; however, seasonal trends were observed:

a.    during winter conditions, oil was more likely to be  transported to the east farther offshore;

b.    during summer conditions, transport was uniformly  multi-directional;

c.    higher percentages of the oil were found within the  water column during winter months as a result of increased wind and wave action, which drawing surface oil droplets into the water column.; and

d.    the greatest surface oiling occurred during summer months, with calmer conditions reducing drawing in of droplets.

2.   The likelihood of oil reaching the shore was demonstrated to be very low, demonstrably:

a.    oil would need to remain on the surface for one month or more to be transported to shore;

b.    predominately westerly winds would transport surface oil away from the coast; and

c.    the possibility of shoreline oiling would only exist during the calmer summer months when a higher percentage of oil remains on the surface and there is a slightly increased probability of winds from the east and northeast transporting surface oil toward land.

In the unlikely event of a blowout, the probability of shoreline oiling for the modeled scenarios was found to be between 0.83 and 1.88 percent of over 400 model runs conducted for the two blowout scenarios, and was only observed during the May, June, and July model runs. It is expected that stranded oil would be highly weathered as the minimum time to shore would be between 20 and 30 days. 

4) Managing Hazards

i)..    Introduction

The regulatory system enforced by the CNSOPB requires operators to identify hazards, to eliminate them where possible, and to properly manage those that remain. Risks are required to be reduced to As Low As Reasonably Practicable (ALARP).  This is achieved through the selection of appropriate designs, and through the implementation of appropriate controls (or safeguards).  The primary focus of CNSOPB’s efforts is to ensure that operators take all reasonable precautions to prevent the occurrence of incidents that may pose a threat to safety of personnel or to the environment. 

In addition, operators are required to identify and understand the potential consequences of each hazard, and develop appropriate recovery strategies, to the satisfaction of the CNSOPB, that would be implemented should an unwanted incident occur.

This approach is displayed pictorially in Figure 1 for a potential spill event.  In this example, a threat could be a loss of well control event (which could result in a blowout).  There are a number of controls and safeguards that must be in place to prevent a spill incident from occurring, some of the key ones being listed under the left side of the ‘bow tie’.  Some of the key recovery strategies that would be implemented should a spill incident actually occur are detailed in the right side of the ‘bow tie’.  Since the Macondo incident that occurred in 2010, significantly increased regulatory expectations have been introduced to further reduce the probability of a well control event, and to reduce the consequences of a blowout should it occur. 

Multiple Drilling Safeguards

Regulations enforced by the CNSOPB require many systems to be in place to prevent accidental releases or blowouts during a drilling program. These systems include proper drilling unit selection, hazard identification and risk assessments, the mud system and the steel (casing) design, downhole measurements of pressure and temperature real time, and finally BOPs. The information generated by the downhole measurements enables appropriate personnel to make proper decisions while a well is being drilled.

ii)..    Increased Regulatory Expectations – Post Macondo

Regulators worldwide have increased their expectations of operators since the Macondo incident.  The CNSOPB is no exception.  Key improvements that are now required by the CNSOPB and being applied to Shell Canada’s proposed drilling program include both additional preventative control and recovery measures, as detailed in Figure 1, and as discussed below.

Additional Preventive Control Measures – Post-Macondo (as listed under the left side of the ‘bow tie’ in Figure 1)

a.    Independent Well Examiner

The CNSOPB now requires that the detailed design of each well that is to be drilled, which is originally prepared by an operator’s drilling team, be subsequently reviewed and verified by a qualified, independent well examiner, and that a verification checklist be produced covering the life of the well. The CNSOPB then reviews the examiner’s report for acceptability. During the drilling of the well, if the drilling program deviates from the verified well design, operations must be stopped and corrective actions taken to bring the drilling program back into compliance. Any changes to the well design that may be proposed at any time during the execution of the drilling program also require the independent well examiner to review and sign off confirming that the change is appropriate and maintains well safety, and such information must be submitted to the CNSOPB.  This provides additional layers of oversight that previously didn’t exist.

b.    Improved Blow Out Preventers (BOPs)

A number of significant improvements have been made to BOPs since the Gulf of Mexico incident, and are summarized as follows:



BOP re-certification not required

5 year re-certification required

Shearing of pipe within the BOP not always possible (preventing sealing of well in some instances)

Verification of shearing capability required at maximum anticipated wellhead pressure

One blind shear (cutting) ram required

2 blind shear rams mandatory (the BOP to be used by Shell Canada has 3

Remote operated vehicle (ROV) intervention at BOP not robust enough to perform all required functions in case of an emergency event

ROV functional testing must be undertaken and verified at the time BOP is installed 

No acoustic back-up system for BOP activation in case drilling installation loses connection to BOP

Acoustic back-up system required and must be tested.

c.    Real Time Monitoring

The CNSOPB now requires that data that is continuously collected from the well during the execution of a drilling program be sent to an onshore base in real time. This data must then be monitored by qualified drilling experts 24 hours a day, seven days a week, to ensure that drilling personnel on site do not overlook something that could lead to a loss of well control. The onshore personnel must be able to phone to the drilling installation and speak directly with the drilling personnel to discuss what they are observing and actions that may need to be taken.  This provides an additional layer of oversight that previously didn’t exist.

d.   Increased Training and Competencies

According to regulations, and established standard practices validated by the CNSOPB, offshore operators must ensure that each worker has appropriate training specific to their position. These requirements meet or exceed standards set out by the International Maritime Organization. They have been evaluated by Lloyd’s Register and found to be some of the most robust in the world. Since the Macondo incident, the CNSOPB has significantly increased training and competency expectations, with an emphasis on greater well control training and ongoing recertification of long-serving personnel. Refer to the Atlantic Canada Offshore Petroleum Industry Standard Practice for the Training & Qualifications of Personnel for details.

e.    CNSOPB Oversight Program

This Plan details the CNSOPB’s oversight measures during the planning and execution of drilling operations that are to take place in deep water, and / or for wells that may encounter high pressure / high temperature.  These oversight measures are being applied to the wells to be drilled by Shell Canada.  

Pre-job requirements of the Operator include demonstration of readiness for the drilling program and submission of contingency and response plans to be implemented in the case of a spill. A critical and systematic assessment of the robustness of the well design from a wellbore security, well safeguard and well control perspective is conducted by CNSOPB staff.  Particular attention is paid to: 
•    the adequacy of the casing and cementing program;  
•    well suspension and abandonment plans;
•    and the need for a comprehensive risk assessment of all anticipated well hazards.  

The CNSOPB review process also includes the verification the adequacy of the well safeguards on an initial and ongoing basis and confirmation of the operator’s ability to drill a relief well and to access well containment systems such as a capping stack. 

During drilling program execution, there are daily reporting requirements and special reporting of all events such as BOP testing, casing pressure tests and cement logging that is done to confirm cement integrity. Weekly meetings with the Operator’s senior staff are held to ensure well control is being maintained at all times. Throughout the program, audits and inspections of the vessel, procedures and key activities are performed by CNSOPB staff.

Regular meetings will be held with Shell Canada focusing on kick prevention, kick detection, well control and blowout prevention and anomalies or upset conditions. “Time-outs” must be called as required until an anomaly (if one has occurred) is fully understood; its impact on the execution of the program is determined; and, any necessary remedies are implemented.

A full scrutiny of any proposed drilling program changes will be undertaken by CNSOPB staff prior to being implemented by the operator.

Additional Recovery Measures – Post-Macondo (as listed under the right side of the ‘bow tie’ in Figure 1)

Operators have traditionally been, and still are, required to submit an Oil Spin Response Plan in relation to a drilling program.  This Plan is to document the procedures for responding to an oil spill. The Plan must describe spill response resources, including those on-site, in the local region, nationally and internationally and arrangements to mobilize to site. Typical spill response methods are described on the CNSOPB website here.

Additional recovery measures now required by the CNSOPB include a Net Environmental Benefit Analysis to guide the selection of appropriate oil spill response tools, and a Well Containment Plan to address the drilling of a relief well and the deployment of a capping stack should a blowout occur.  The preparation and submission of both of these to the CNSOPB is also a condition imposed in the Decision Statement issued by the Minister of the Environment. 

a.    Net Environmental Benefit Analysis 
Net environmental benefit analysis (NEBA) is a structured approach used by the response community and stakeholders during oil spill preparedness planning and response, to compare the environmental benefits of potential response tools and develop a response strategy that will reduce the impact of an oil spill on the environment. A NEBA is one of the considerations used to select spill response tools that will effectively remove oil and will minimize the impact of the spill on the environment. 

During the planning phase of Shell Canada’s drilling project, a NEBA was prepared to inform the development of the response strategy to be detailed in the Oil Spill Response Plan.  The NEBA was reviewed by the CNSOPB.  Advice was provided to the CNSOPB through Environment Canada’s Environmental Emergencies Science Table Science Table. Participants included representatives from Fisheries and Oceans Canada, Environment Canada, Canadian Wildlife Service, Canadian Coast Guard, Transport Canada and Natural Resources Canada.

Although contemplated under certain situations, neither the acceptance of the NEBA, nor the granting of an authorization for a drilling program (and any related approvals to drill a well), grant approval for the use of a dispersant in responding to an oil spill.

If a major incident was to occur, and an Operator was to consider the use of a dispersant, legislation requires that a specific request for approval be made at that time to the CNSOPB’s Chief Conservation Officer (CCO).  Such a request would have to be accompanied by an incident specific NEBA.  The use of dispersants would only be considered in cases where a net environmental benefit analysis concludes that it is better for the environment to do so.  The CCO would firstly consult with experts of Environment Canada’s Environmental Emergencies Science Table, which brings together relevant experts in the field of environmental protection, as appropriate, such as response agencies, all levels of government, Aboriginal representatives, local communities, industries, environmental non-government organizations, and academic institutions. Additionally, the CCO is obligated by legislation to consult with appropriate federal and provincial Ministers before granting approval to use a dispersant.    

b.    Well Containment Plan

Shell Canada’s final well containment plan/source control contingency plan outlines the numerous tools that Shell would use to stop the flow of hydrocarbons in the unlikely event of a blowout. To view this plan, click here.