Hydrogen sulphide (H2S) is one of the most toxic of all naturally occurring gases. It occurs world-wide in various concentrations in the scope of the drilling industry. It is explosive and heavier than air. In small concentrations it has an offensive rotten egg odourwhile greater concentrations can paralyse the olfactory nerves so no odour is detected. When ignited it burns with a blue flame producing sulphur dioxide (S02) which also can cause serious injury.
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PPM of H2S |
Classifications |
Physiological Effect |
|
10 |
Minor Irritation |
Can smell (like rotten eggs). Minimum eye irritation. |
|
15 |
|
Minimum lung irritation |
|
70-150 |
Olfactory nerve paralysis
Major Irritation
|
Paralyses sense of smell in 3-15 minutes. Nausea
Major irritation of eyes, throat and lungs |
|
150-400 |
Injuries |
Loss of smell, dizziness, difficult respiration, coughing, burns eyes, throat and lungs. Needs prompt removal to fresh air to avoid respiratory paralysis. |
|
400-700 |
Dangerous |
Coughing, collapse and unconsciousness. Breathing will stop and death will result in a few minutes if artificial resuscitation is not given immediately. |
|
700-1000 |
Immediate threat to life. |
Rapidly produce unconsciousness. Death will occur in a few minutes. |
|
1000 and above |
Fatal |
Immediate unconsciousness. Death will occur in a few minutes. |
Drilling Operations
When drilling a well where H2S is suspected, sound practice demands that all personnel be trained in special procedures relative to well control, testing and coring. Also, it is recommended that all H2S equipment be installed and functional one week prior to penetration of the suspected zone, or as necessary to comply with Company regulations.
Well Control
H2S monitoring equipment should be continually surveyed and tested periodically.
Personnel should be trained in H2S procedures and personal breathing apparatus.
When H2S is expected to surface, rig floor personal should wear breathing apparatus.
Emergency Procedures
In the event of an emergency situation involving the release of H2S into the atmosphere, at either the visual or auditory alarm, all off duty and non-essential personnel should immediately secure their personal breathing apparatus and proceed to the designated briefing area upwind of the wellbore.
H2S alarm procedure guide – offshore
- Yellow/Amber Flashing Light (<10 ppm)
|
Driller and Asst. Driller on shift |
Evacuate area of non essential personnel Standby with 30 min breathing apparatus Inform toolpusher |
- Audible Alarm (20 ppm) – A two tone alternating high to low sound
|
Driller and Asst. Driller on shift |
Put on 30 min breathing set and evacuate area of non essential personnel Stop ventilating fans Close of source of H2S (Secure Well) Proceed to muster point and report |
|
Driller and Asst. Driller off shift |
Standby at muster point with 30 min breathing apparatus |
|
Petroleum Engineer |
Standby at muster point with 30 min breathing apparatus and test equipment |
|
Radio Operator |
Notify standby boat/s to proceed up wind from the rig. |
|
Barge Engineer |
Put on 30 min breathing apparatus and standby to close deck hatches |
|
Campboss |
Take roll and report to tool pusher |
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Remain at muster point until all clear is given by Tool Pusher. |
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