Offshore Equipment, Procedures and Plans
A major success factor for the safe drilling of a well is to ensure adequate control and management of well fluid pressures whilst drilling.
Minimising and Mitigating Risk
A major success factor for the safe drilling of a well is to ensure adequate control and management of well fluid pressures whilst drilling. Good well control ensures the appropriate level of pressure in the well bore fluids necessary to counter-balance the pressures experienced in the rocks being drilled through – whether they contain oil and gas or not – all being managed through the application of proper safety procedures and the use of calibrated equipment. Various mechanisms are routinely used to ensure well control and balancing of the pressures in the wellbore:
Analysis of the data from historical wells drilled in the region in the same or similar rocks types. Such data indicates the reservoirs in The Bahamas to be at or below ‘normal’ pressure – hydrostatic head equals pore pressure.
Rig crews receive extensive training on how to recognise and deal with any impending problems, like formation fluids (oil or gas) entering the wellbore, and how to respond appropriately.
The use of onboard fluid management systems that identify the relative flows of fluids into and out off the well bore. Nowadays equipment is capable of automatically balancing the pressures in the wellbore by increasing or decreasing the hydrostatic head in realtime. Routinely this balancing is achieved by ensuring that the mud density is carefully calculated, monitored and maintained.
Therefore, well control is customarily managed using the onboard systems. Additionally, every well is fitted with a Blow Out Preventer (BOP), situated on the seabed, which can seal off fluid flow from the well through multiple devices activated by multiple systems. In accordance with regional regulations, upgraded since the Macondo well incident in the Gulf of Mexico, and international best practices, Bahamas Petroleum Company will look to have either a Top Hat or a Capping Stack on standby, ensuring industry standard redundancy, in the unlikely event of loss of well control (Additional Well Controls – right).
Before operations commence, a final well plan will define the life of a well, from initial drilling to plugging and abandonment. The plan will describe in detail how the well will be drilled including all procedures associated with the drilling and dimensions (i.e. hole size, casing specifications, cement etc). A well plan has already been substantially completed. High quality data 3D seismic, the shallow hazard survey, the geologic and stratigraphic assessment, historical well data detailing potential reservoir conditions (e.g. temperature and pressure) have been used in the planning of the well and will continue to assist in the completion of the plan. All cementing operations will be a key component of this plan. All this information will assist with the minimisation of possible risks and identify key mitigation processes and procedures.
Qualified International Operator
A drilling rig with advanced safety equipment, significant system redundancy and qualified/trained staff will be utilised to drill the well. Personnel on the rig must undergo intensive training and be certified and experienced in adequate “Well Control”. This includes all the onshore engineering and supervisory groups. Personnel will be certified by passing a mandatory exam every two years known as the IWCF (International Well Control Forum). Persons without the certification or who fail renewals are not allowed to work in a position of significance relating to the drilling operation.
Emergency Response Plan
The Emergency Response Plan will identify and address potential emergency scenarios inclusive of well control problems, evacuations, security, spills, natural disasters, property loss, fire and/or explosions, hazardous releases, public relations, personnel, transportation and any public impacts. Regular training exercises are mandated to ensure the adequacy and relevance of the plan and the proficiency of staff in compliance with its regular implementation. Such exercises are often coordinated regionally to engage responders, the authorities and support services.
Safety Management System
The Safety & Environmental Management System (SEMS) Plan, adopted in the Gulf of Mexico, promotes safety and environmental protection by ensuring all personnel aboard a facility are familiar with and comply with the component policies, procedures and actions defined in the SEMS and that they have adequate skills and knowledge to perform their assigned duties. The SEMS programme looks to identify, address and manage safety, environmental hazards and impacts during the design, construction, startup, operation, inspection and maintenance of mobile offshore drilling units (MODU).
Additional Well Controls
Since the spill in the Gulf of Mexico (after June 2010) more than 300 new wells have been approved for drilling in the Gulf.
That this is considered safe is due to the enhancement and implementation of regulations on Well Integrity and Blow Out Preventer’s & Control Systems in conjunction with enhanced spill response and well containment resources based on Worst Case Discharge calculations. Additionally, all operators are now required to implement a coordinated Safety & Environmental Management System (SEMS) that had been hitherto voluntary. Additional well containment resources (pictured below) include a Capping Stack or a Top Hat.
Images: Helix Well Containment Group www.hwcg.org