Hydrogen Sulphide (H2S)

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 odour while 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.

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
Remain at muster point until all clear is given by Tool Pusher.