Contingency Actions

As we discussed in section 2, all emergencies will result from one or more of the fallowing:

operational problems natural causes third party action

In this section, we discuss the action that must be taken to deal with these problems. Clearly each well or drilling programme must be dealt with individually, however, the following provides a guide for input into Emergency Contingency Manuals.

6.1 Operational problems

These result from human, equipment or system failure and include such emergencies

  1. Well control problems
  2. Oil spills
  3. Release of dangerous substances
  4. Fire and explosions
  5. Serious or fatal accidents
  6. 1.1 Well control problems

Most well control problems will be solved by the rig supervisory staff. However, sometimes matters do get out of control and a blowout follows. The effects of a blowout vary greatly and the Contingency Plan must consider each well's situation with respect to its potential flow and its environment. The factors to be considered in each case are:

  1. Potential well flow
  2. Potential duration of well flow prior to bridging
  3. Onshore: site locations, remoteness or proximity to industry or population centres
  4. Offshore: knock-on effect on multiwell platform
  5. Radiation effects from blowout fire
  6. Potential of toxic gas production
  7. Potential of oil spill
  8. Effects of smoke

Blowout control techniques Once a blow-out has occurred there is a choice of four approaches to handle the problem:

  1. Do nothing and hope that the excessive production rate will allow the formation to bridge with sand production or collapse.
  2. Well capping which is only possible where the wellhead area is relatively undamaged so that auxiliary spools can be placed on the wellhead or suitable casings.
  3. Relief well dynamic kills - relief wells are used to enter the producing wellbore and a high rate of circulation down the relief well and up the blowout well creates sufficient back pressure on the formation to initially reduce flow and ultimately kill the well.
  4. Well saturation methods — relief wells are used to saturate the producing reservoirs around the production point in the wellbore to choke off production.

Of these 1. and 2. are the cheapest options. However, since their chances of success can vary, it is expedient to start a relief well immediately after a blowout to ensure that if options 3. and 4. are required there is minimal delay in achieving these.

Relief well planning Prior to programming the relief well, the following information should be collated:

  1. Positional data of nearby wells and wells being drilled
  2. Predicted new formation pressure regimes
  3. Casing design criteria
  4. Flow area requirements in wellhead and tubing for high volume injection and killing operations

Relief well siting The following criteria should be considered when selecting a suitable relief well site:

  1. Subsurface position of well(s)
  2. Distance from blowout at surface
  3. Access roads suitability
  4. Prevailing wind direction
  5. Water supply possibilities
  6. Seabed conditions and obstructions
  7. Water currents
  8. Nearby shipping lanes

On land relief wells, the killing pump station will be located at the relief well site, consequently any site should be large enough to contain this and a vast amount of drilling fluid storage capacity.

Regaining control of well All initial procedures taking place on site to regain control must be automatic and be laid down clearly in the Emergency Contingency Manual. They should be implemented whilst simultaneous support is being arranged. These actions will typically include:

1, At site

  • a) Raise alarm
  • b) Appraise situation and inform Base together with request for assistance
  • c) Attempt to contain hazard as much as possible
  • d) Secure other wells by closing subsurface safety valves
  • e) If possible, secure and protect the installation and complement by some or all of the following:

Shut down ancillary machinery Shut down process equipment Isolate and depressurise process system Reduce/remove flammable materials

Isolate and protect non-affected areas and equipment

Control access to site

Muster personnel

Deploy fire control teams

Deploy rescue teams

Prepare to abandon rig/area

Prepare to move a floating drilling unit off location Abandon installation

2. At base

  • a) Mobilise Emergency Action Team
  • b) Arranging immediate assistance for fire-fighting and rescue
  • c) Mobilise relief action
  • d) Notify appropriate authorities
  • e) Investigate methods for controlling well and containing situation
  • f) Prepare relief well plan
  • g) If required, organise relief well rig/site prep/logistics 6.1.2 Oil spills

In establishing their anti-pollution plans, operators should study their operating methods and conduct surveys of the regions to identify vulnerable areas and areas of ecological importance. Any risk areas highlighted by the surveys form the basis for contingency planning. Emphasis should be placed upon the requirement to provide protection and containment. Subsequent collection and removal measures are largely remedial, totally dependent on the particular situation and may involve third parties.

In the event of an incident, steps must be taken immediately to assess the situation, eliminate the sources and contain the pollutant. The appropriate local authorities should be consulted when deciding upon removal and clean-up methods, as their approval may be needed.

Prevention Working practices should be such as to minimise the likelihood of accidental release. Drip trays and closed drain systems should be designed to contain likely spillages prior to detection and treatment. In areas of ecological sensitivity, protective booms and skimmers must be available.

Collection and containment The plans used for this must be realistic for the prevailing wind and wave conditions that could be expected in the areas. The effective methods to be used are very dependent on the wind and waves and include barriers, booms or chemicals offshore and physical damming onshore.

Removal The removal method selected is also dependent on the local conditions and the spill to be removed. The use of absorbent materials, skimming and pumping methods, chemical removal or even burning (if permitted) should be considered.

Dispersal Dispersants are now widely used in the removal of oil spills offshore and can be effectively applied in rough seas. None of the above-mentioned removal methods, with the exception of burning (which has to be done very quickly after the spill has occurred) is effective in rough seas, so in most heavy weather offshore locations, dispersal will probably be the best method to apply to the spill.

6.1.3 Release of dangerous substances

In developing contingency plans for accidental releases of hazardous materials, operators must evaluate the potential hazards associated with such products. They should identify vulnerable areas and determine the measures necessary to effect rapid containment and reduce the exposure risk to life and property.

Should an incident occur, prompt action must be taken to stem the flow at source, thereby preventing further spread of the substance. Particular attention must be paid to the prevailing wind strength and direction and the effect this may have on the spread of dangerous liquids or gases.

As an aid to determining different response levels to a particular situation, various operating conditions can be considered. Certain conditions represent situations of minor or moderate concern, whilst others may involve considerable loss of control, possibly with the release of lethal concentrations of gas. This condition, mainly applicable to blowout situations, might require ignition. This will, undoubtedly complicate subsequent control operations, but if lives are at risk, the decision should not be delayed.

For wells containing H2S, drills must be carried out on a regular basis on the installation to ensure that crews are familiar with H3S procedures. If a blowout occurs, consideration must be given to igniting all produced gas as quickly as possible. This matter must be covered in the Emergency Contingency Manual and not just left until the situation arises.

When H3S or SO, (which is created after igniting H,S) is released in an uncontrolled manner, it can affect areas much larger than the immediate installation. Prevailing winds can carry the gas to population centres and the possibility of this must be analysed and planned for in the Emergency Contingency Manual.

6.1.4 Fire and explosions

In the event of a major fire or explosion, the Emergency Contingency Manager will be confronted with a very confused situation. Reports will be coming in from several sources and in practice they will often contradict each other. Consequently, the Emergency Contingency Manual must provide guidelines for the Site Supervisor to send a clear and concise appraisal of the situation. The initial situation appraisal must determine the following:

  1. Likely source of fire and containment potential
  2. Type of combustibles present
  3. Any casualties
  4. Any missing crew
  5. Potential knock-on effect
  6. Emergency system status

Immediate priorities for the Site Supervisor are:

  1. Give medical treatment to any casualties
  2. Rescue any missing personnel
  3. Contain or restore control to situation

To contain and control the situation the following methods can be used:

  1. Stop the flow of combustibles and blow down any pressurised process facilities
  2. Isolate any redundant electric circuits
  3. Shut down ventilation in affected areas
  4. Apply maximum water cooling to affected areas

All personnel on the installation must be conversant with all emergency procedures, which should be along the lines of:

  1. Sound the alarm
  2. Ensure their escape routes are clear
  3. Report the situation to the Site Supervisor
  4. Help any casualties to clear the affected areas

The Site Supervisor upon being notified of the fire should:

  1. Direct actions, including fire and rescue teams and firefighting systems, to control and contain the emergency
  2. On offshore rigs, use the radio operator to inform the standby boat, any shipping or helicopters in the area and the coastguard
  3. Direct medic, HLO, waking team and life boat crews
  4. Contact the Emergency Contingency Manager giving full details of the emergency and initial back-up requirements
  5. Consider evacuation of the installation
  6. Make a head count
  7. 1.5 Serious or fatal accidents

In the event of a serious or fatal accident, the Site Supervisor has three functions to fulfil:

  1. To ensure that the casualty is given immediate treatment
  2. To ensure that the workplace is safe and that the accident count cannot recur
  3. To comply with all company and national authorities requirements with regard to incident reporting and investigation

In most cases, work at the scene of a fatality may not be resumed except with permission of the appropriate national authorities; unless, in the opinion of the Site Supervisor^ to fail to do so might endanger the lives of others.

The Emergency Contingency Manual should lay down the correct formula to be employed when informing the relatives of a casualty.

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