H2S Workover with Cartridge Respirators and a Leaking BOP
A gas-condensate field is preparing a workover on well 12, which produces 2.5% H2S (about 25,000 ppm) and 8% CO2. The contractor’s plan requires half-face respirators with acid-gas cartridges and portable detectors set to alarm at 10 ppm. The detectors’ calibration certificates expired 14 months ago. The well-control stack was pressure-tested, but the annular BOP ram has a slow hydraulic leak. The prevailing wind blows toward a 60-person camp 400 m away, and the emergency plan was last revised before the camp was expanded. Two of the contractor’s four crew members have no H2S training. The operator’s production superintendent wants to start at 06:00 to avoid downtime; the contractor says the leak is “minor” and can be monitored.
1. Should the workover be authorised to start? Explain the key failures.
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No. The start should be refused. At 2.5% H2S, the well stream is immediately dangerous to life and health if released. Half-face respirators with acid-gas cartridges are not acceptable for that concentration; they provide no reliable protection against an oxygen-deficient or high-H2S atmosphere and can be quickly overwhelmed. Supplied-air breathing apparatus or self-contained breathing apparatus, with escape sets, is required for the personnel at risk, supported by continuous gas monitoring and wind indicators.
The expired detector calibration is a second blocking failure: an uncalibrated detector cannot be trusted to give the 10 ppm alarm or the higher evacuation alarm. The annular BOP leak is a well-control barrier defect, not a “minor” housekeeping issue; it must be repaired and pressure-tested before the workover. The emergency plan is also out of date because the camp has expanded and lies downwind. Starting at 06:00 to avoid downtime is not a risk justification.
2. What must be corrected before authorisation, and how should the emergency plan be changed?
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Before authorisation: repair and test the annular BOP; calibrate or replace all portable and fixed H2S detectors and set alarm levels appropriate to the hazard; provide supplied-air/SCBA and escape sets; train all crew members in H2S and rescue; issue a permit-to-work with a pre-job safety meeting; confirm well-control procedures and kick detection; and station rescue personnel with breathing apparatus.
The emergency plan must be revised for the actual camp location, prevailing wind, muster points, alarm levels, evacuation routes and mutual-aid arrangements. It should define who orders evacuation, how the 60-person camp is alerted, how non-essential personnel are moved upwind, and how the injured are rescued without exposing rescuers. The plan should include drills with the contractor and camp management before the workover. The operator should also verify contractor competence and stop-work authority. “Monitoring” a known BOP leak is not an acceptable control; the barrier must be restored.
3. If the superintendent overrides the refusal, what should the industrial safety specialist do?
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The specialist should not sign or verbally endorse the permit. The refusal and the reasons should be recorded in writing, with the specific deficiencies: inadequate respiratory protection, expired detector calibration, defective BOP, outdated emergency plan and untrained crew. The specialist should escalate to the operator’s chief engineer or responsible manager and, where the law provides, notify the state industrial safety authority. If work starts anyway, the specialist should request immediate suspension and evacuation of non-essential personnel from the downwind camp.
The key judgement is that a production superintendent cannot override a well-control barrier defect and a breathing-protection failure by asserting urgency. The specialist’s duty is to protect life and the environment, not to preserve the schedule. The written record also protects the specialist and creates the basis for administrative and disciplinary action against those who ordered the unsafe start.