This document provides an overview of hydrogen sulfide (H2S) in oilfield operations. It discusses the physical and chemical properties of H2S, why it occurs, health effects at different exposure levels, and regulatory exposure limits. The document also summarizes American Petroleum Institute guidance and Bureau of Land Management regulations regarding H2S monitoring, warning systems, training, contingency planning, and public protection requirements for oil and gas operations that may encounter H2S.

1. HYDROGEN SULFIDE
In the Oilfield

2. OVERVIEW
 General H2S
Information
 API Guidance
 BLM Onshore Order
#6
 Other Regulations
 DOT
 EPA

3. WHAT IS H2S
 Colorless gas
 Flammable
 Heavier than air
 Extremely toxic
 “Rotten egg” smell
 Deadens sense of
smell

4. WHY DOES H2S OCCUR
 Biological breakdown of organic matter in
an anaerobic environment

5. HEALTH EFFECTS
 Low concentrations (<10ppm)–
irritation of eyes, nose, throat and
respiratory system
 Moderate concentrations
(10<x>30ppm)– headache,
dizziness, nausea, coughing,
vomiting and difficulty breathing
 High concentrations (>30ppm)–
shock, convulsions, coma, death

6. EXPOSURE LIMITS
 ACGIH TLV (8hr)= 10 ppm
 OSHA ceiling (15 min)= 20 ppm
 OSHA peak (instantaneous) = 50
ppm
 IDLH = 100 ppm
 ATSDR MRL = 0.07 ppm (acute),
0.03 ppm (intermediate)

7. OTHER PHYSICAL PROPERTIES
 Explosive
 Reacts with water to form Sulfuric Acid
– Tears
– Lungs
 Reacts with iron/steel to form Iron Sulfide
(extremely flammable)
– Iron sponge
 Burns to form Sulfur Dioxide (toxic gas)
 May lead to metal fatigue

8. H2S PRODUCTION

9. AMERICAN PETROLEUM INSTITUTE
 Recommended Practice 49 -Recommended Practice
for Drilling and Well Servicing operations Involving
Hydrogen Sulfide
 Applies to well drilling, completion, servicing, workover,
downhole maintenance and plug & abandonment
procedures.
 Establishes location classifications
 Addresses personnel training, monitoring equipment,
personal protective equipment, contingency planning and
emergency procedures.
 Also establishes Sulfur Dioxide requirements

10. LOCATION CLASSIFICATIONS
 No Hazard Area
 Condition 1 Area – low hazard
 <10 ppm
 Condition 2 Area – medium hazard
 >10ppm, <30 ppm
 Condition 3 Area – high hazard
 >30 ppm

11. WARNING SYSTEMS
 Condition 1 Area –
warning sign with
green flag or light
 Condition 2 Area -
warning sign with
yellow flag or light;
visual and audio alarms
 Condition 3 Area –
warning sign with red
flag or light; visual and
audio alarms

12. MONITORING
 Equipment
 Manufacturer certified for H2S and SO2
 Accurate in a range from well below to well
above action levels (H2S = 10 ppm, SO2 = 2 ppm)
 Mixture of fixed and portable monitors as needed
to protect workers

13. MONITORING EQUIPMENT
 Used during all activities where a potential of H2S
and SO2 to exceed action levels exists.
 Located in the following areas:
 Bell nipple
 Mud return line or shale shaker
 Pipe-trip tank
 Driller’s station
 Living quarters
 Other areas of potential accumulation
 Calibrated and functionally tested per manufacturer

14. WARNING SYSTEM ACTIVATION
 Typical 2 level alarm
 10 ppm
 20 to 300 ppm

16. TRAINING
 All personnel working in an area with potential of
H2S and SO2 to exceed action levels exists.
 Minimum topics;
 Hazards, characteristics and exposure symptoms
 Sources
 Detection equipment, warning signs and wind direction
awareness
 Workplace procedures, location of safety equipment and
location of safe breathing areas
 PPE
 Emergency response

17. CONTINGENCY PLAN
 May be required by certain federal, state or local
agencies.
 Must contain:
 Facility specific description and maps
 Monitoring equipment locations
 Safety equipment locations
 Safe breathing area locations
 Evacuation routes
 Training and drill requirements
 Emergency response procedures

18. BUREAU OF LAND MANAGEMENT
 Onshore Oil and Gas Order No. 6, Hydrogen
Sulfide Operations

19. APPLICABILITY
 All onshore Federal and Indian oil and gas
leases.
 Drilling, completing, testing, reworking,
producing, injecting, gathering, storing, or
treating operations.
 Involving zones which are known or could
reasonably be expected to contain H2S
present in concentrations equal to or
greater than 100 ppm.

20. REQUIREMENTS
 Written H2S Drilling Operations Plan
submitted with APD
 Written Public Protection Plan submitted
with APD, notification of production or when
radius of exposure criteria are met
 Training Program available for review upon
request
 All plans and programs available at site

21. REQUIREMENTS
 H2S Drilling Operations Plan
– Site diagrams showing all safety equipment,
topography, exit roads, briefing (safe breathing)
areas, flare lines and pits
– Appropriate well control equipment, personal
protective equipment, H2S monitoring
equipment, visual and audio warning system,
appropriate mud system, appropriate
metallurgical plan and means of communication
from wellsite

22. REQUIREMENTS
 Public Protection Plan
– Drilling or production site where:
 The 100 ppm radius of exposure is greater
than 50 feet and includes any occupied
residence, scholl, church, park, school bus
stop, place of business or other are where the
public could be reasonably expected to
frequent

23. REQUIREMENTS
 Public Protection Plan
– Drilling or production site where:
 The 500 ppm radius of exposure is greater
than 50 feet and includes any part of a
federal, state, county or municipal road
maintained for public use

24. REQUIREMENTS
 Public Protection Plan
– Drilling or production site where:
 The 100 ppm radius of exposure is equal to
or greater than 3,000 feet and includes any
facility or part of a federal, state, county or
municipal road maintained for public use.

25. RADIUS OF EXPOSURE
 Pasquill-Gifford derrived equation:
X = [1.589)(H2S concentration)(Q)]0.6258
X = radius of exposure
H2S concentration = decimal equivalent of the
volume fraction of H2S in the gas stream
Q = maximum volume of gas determined to be
available for escape in cubic feet per day

26. ESCAPE RATE (Q)
 Gas production facility = maximum daily
absolute open flow gas production rate
 Oil production facility = (gas/oil ratio of
production) (maximum daily production
rate)
 Exploration well = use the above from
producing wells from the target interval in
the area

27. PUBLIC PROTECTION PLAN
 Must include:
– responsibilities of key personnel and institutions
for alerting the public and requesting assistance;
– list of telephone numbers and names of
response agencies or contractors, residents,
those responsible for occupants of public
buildings and those responsible for safety of
public roadways;
– a plat of the 100 ppm and 500 ppm radius of
exposure showing all private and public buildings
and roads;
– emergency response measures

28. PUBLIC PROTECTION PLAN
 May be required to
include: public
education seminars,
mass alert systems
(including
telephone,
commercial radio or
television), and
public input
allowances

29. OTHER REGULATIONS
 OSHA
 Process Safety Management
 DOT
 Pipeline Safety Requirements
 EPA
 Risk Management Plan requirements
 SARA Title 3 requirements
 STATE SPECIFIC