Tuesday, November 25, 2014

HYDROGEN SULFIDE GAS MONITORING AND CONTROL IN THE OIL AND GAS INDUSTRY



Hydrogen Sulfide Gas MONITORING AND CONTROL IN THE OIL AND GAS INDUSTRY


H2S Special Precautions


                                         Figure 1. Hydrogen Sulfide warning sign


Hydrogen Sulfide gas is very corrosive and causes metals to become brittle.  Therefore, employers need to take special precautions when choosing equipment when they may reasonably expect to encounter H2S.  This may include appropriate H2S trimming of equipment in accordance with National Association of Corrosion Engineers (NACE) Standards.
All well-drilling sites should be classified according to areas of potential and/or actual exposure to H2S.  The recommendations and employee instruction will vary depending on the type of area.  The four hazard levels are:
·         No Hazard Condition
·         API Condition I - Low Hazard

Any well that will not penetrate a known Hydrogen Sulfide formation would be categorized as a No Hazard Area. Special Hydrogen Sulfide equipment is not required.
Work locations where atmospheric concentrations of H2S are less than 10ppm.
Recommended for Area:


  • Hydrogen Sulfide warning sign with green flag warning device present.
  • Keep all safety equipment in adequate working order.
  • Store the equipment in accessible locations.


Work locations where atmospheric concentrations of H2S are greater than 10ppm and less than 30ppm.
Recommended for Area:


  • Legible Hydrogen Sulfide warning sign with yellow flag warning device present.
  • Keep a safe distance from dangerous locations if not working to decrease danger.
  • Pay attention to audible and visual alarm systems.
  • Follow the guidance of the operator representative.
  • Keep all safety equipment in adequate working order.
  • Store the equipment in accessible locations.
  • An oxygen resuscitator.
  • A properly calibrated, metered hydrogen sulfide detection instrument.


Work locations where atmospheric concentrations of H2S are greater than 30ppm.
Recommended for Area:


  • Post legible Hydrogen Sulfide warning sign with red flag warning device.
  • Post signs 500 feet from the location on each road leading to the location, warning of the hydrogen sulfide hazard.
  • Check all Hydrogen Sulfide safety equipment to ensure readiness before each tour change.
  • Establish a means of communication or instruction for emergency procedures and maintain them on location, along with contact information of persons to be informed in case of emergencies.
  • Ensure usability of two exits at each location.
  • Do not permit employees on location without hydrogen Sulfide safety training. (Employees may be permitted on location for specific Hydrogen Sulfide training purposes that does not include general rig training.)
  • Pay attention to audible and visual alarm systems.
  • Store the equipment in accessible locations.

    • Two Hydrogen Sulfide detectors should be present (one should be a properly calibrated, metered detection instrument, and the other should be a pump type with detector tubes. The maximum permissible exposure limit (PEL) is 20 ppm. Respiratory protection would be required if periodic testing indicates employee exposures to H2S at concentrations above the PEL. See OSHA Standard Respiratory Protection, [29 CFR 1910.134].

  • Oxygen resuscitator.
  • Three wind socks and streamers.
  • Two NIOSH/MSHA 30-minute, self-contained breathing apparatus for emergency escape from the contaminated area only.


Additional Information
1.   Standards. American Petroleum Institute (API).
2.   Search for Standards. American National Standards Institute (ANSI).
3.   Health, Safety & Environmental (HSE) Reference Guide. International Association of Drilling Contractors (IADC).
4.   ANSI Z390.1 - 2006, Accepted Practices for Hydrogen Sulfide Safety Training Programs. American Society of Safety Engineers (ASSE).
5.   Hydrogen Sulfide. National Institute for Occupational Safety and Health (NIOSH) Safety and Health Topic.
6.   Safety Issues. Association of Energy Services Companies (AESC).
·         Use of Anchors and Guywires
·         Use of Compressed Gas Cylinders
·         Crane Operation
·         Proper Electrical Safety (including hot sticks)
·         Hot Work
·         Fall Protection Systems
·         H2S - Hydrogen Sulfide
·         Respirator Usage
·         Use of wooden, metal and plastic (fiberglass) portable ladders
·         Scaffolding
·         Vehicle Operation


Hydrogen Sulfide Gas


Figure 1. Hydrogen sulfide warning sign: Warning Hazardous Area is in yellow letters on a black background. In black letters on a yellow background, the sign says Hydrogen Sulfide, Extreme Health Hazard, Fatal or Harmful if Inhaled.

Hydrogen Sulfide or sour gas (H2S) is a flammable, colorless gas that is toxic at extremely low concentrations.  It is heavier than air, and may accumulate in low-lying areas.  It smells like "rotten eggs" at low concentrations and causes you to quickly lose your sense of smell. Many areas where the gas is found have been identified, but pockets of the gas can occur anywhere.  Iron sulfide is a byproduct of many production operations and may spontaneously combust with air.
Flaring operations associated with H2S production will generate Sulfur Dioxide (SO2), another toxic gas.
Active monitoring for hydrogen sulfide gas and good planning and training programs for workers are the best ways to prevent injury and death.
Hazards may include and/or be related to the following:



                                                      Figure. 2. SCBA




                                                  Figure. 3. Gas detector

All personnel working in an area where concentrations of Hydrogen Sulfide may exceed the 10 Parts Per Million (PPM) should be provided with training before beginning work assignments.
Potential Hazard:
H2S exposure greater than the Permissible Exposure Limit (PEL).
Possible Solutions:
Implement an H2S contingency plan (see API) including, but not limited to:
Appropriate instruction in the use of hydrogen sulfide safety equipment to all personnel present at all hydrogen sulfide hazard areas.
Gas detection where hydrogen sulfide may exist.
Appropriate respiratory protection for normal and emergency use. [29 CFR 1910.134]
For emergency response information, see Hazardous Waste and Emergency Response (HAZWOPER) Standard, [29 CFR 1910.120].
Comprehensive training should be provided for workers in H2S operations. Example topics include:
·         Identification of the characteristics, sources, and hazards of Hydrogen Sulfide.
·         Proper use of the Hydrogen Sulfide detection methods used on the site.
·         Recognition of, and proper response to, Hydrogen Sulfide warnings at the workplace.
·         Symptoms of Hydrogen Sulfide exposure.
·         Proper rescue techniques and first-aid procedures to be used in a Hydrogen Sulfide exposure.
·         Proper use and maintenance of personal protective equipment. Demonstrated proficiency in using PPE should be required.
·         Worker awareness and understanding of workplace practices and maintenance procedures to protect personnel from exposure to hydrogen sulfide.
·         Wind direction awareness and routes of egress.
·         Confined space and enclosed facility entry procedures.
·         Locations and use of safety equipment.
·         Locations of safe briefing areas.
·         Use and operation of all Hydrogen Sulfide monitoring systems.
·         Emergency response procedures, corrective action, and shutdown procedures.
·         Effects of Hydrogen Sulfide on the components of the Hydrogen Sulfide handling system.
·         The importance of drilling fluid treating plans prior to encountering Hydrogen Sulfide.
Additional Information:
RP 49, Recommended Practice for Drilling and Well Servicing Operations Involving Hydrogen Sulfide. American Petroleum Institute (API), (2001, May/Reaffirmed 2007, March). Includes well drilling, completion, servicing, workover, downhole maintenance, and plug and abandonment procedures conducted with hydrogen sulfide present in the fluids being handled.
Safety Issues. Association of Energy Services Companies (AESC).
·         Use of Anchors and Guywires
·         Use of Compressed Gas Cylinders
·         Crane Operation
·         Proper Electrical Safety (including hot sticks)
·         Hot Work
·         Fall Protection Systems
·         H2S - Hydrogen Sulfide
·         Respirator Usage
·         Use of wooden, metal and plastic (fiberglass) portable ladders
·         Scaffolding
·         Vehicle Operation


Metal fatigue, including hydrogen embrittlement or sulfide stress cracking, can result in a release of hydrogen sulfide gas.
Potential Hazard:
Being exposed to Hydrogen Sulfide.
Getting Injured due to equipment failure.
·         Possible Solutions:
Select materials in accordance with the MR0175/ISO15156 criteria for H2S service.
MR 0175C, Metals for Sulfide Stress Cracking and Stress Corrosion Cracking Resistance in Sour Oilfield Environments. National Association of Corrosion Engineers (NACE), (2003, December) [Also ISO 15156, Petroleum and natural gas industries-Materials for use in H2S containing environments in oil and gas production, International Standards Organization (ISO)].
Treat drilling fluids to chemically reduce corrosion failures.




It is possible for hydrogen sulfide gas to accumulate in any low or enclosed area, such as a gas venting system, mud system, cellars, pits, and tanks.
Potential Hazard:
Being exposed to Hydrogen Sulfide.
Possible Solutions:
Provide adequate ventilation for the removal of any accumulation of H2S.
Implement effective confined space entry program.

Additional guidance materials are available from:
RP 49, Recommended Practice for Drilling and Well Servicing Operations Involving Hydrogen Sulfide. American Petroleum Institute (API), (2007, March). Includes well drilling, completion, servicing, workover, downhole maintenance, and plug and abandonment procedures conducted with hydrogen sulfide present in the fluids being handled.
Spec 6A, Specification for Wellhead and Christmas Tree Equipment (includes Errata 3 dated June 2006). 19th Edition. (2004, July). [Also ISO10423:2003] Specifies requirements and gives recommendations for the performance, dimensional and functional interchangeability, design, materials, testing, inspection, welding, marking, handling, storing, shipment and purchasing, of wellhead and christmas tree equipment for use in the petroleum and natural gas industries.
Spec 6A 718, Specification of Nickel Base Alloy 718 (UNS N07718) for Oil and Gas Drilling and Production Equipment (includes Addendum dated March 2006). 1st Edition. (2004, March). Provides specification requirements for Nickel Base Alloy 718 (UNS N07718) that are intended to supplement the existing requirements of API Spec 6A and ISO 10423. These additional specification requirements include detailed process control requirements and detailed testing requirements.
For additional information, see the API website.
Safety Issues. Association of Energy Services Companies (AESC).
Use of Anchors and Guywires
Use of Compressed Gas Cylinders
Crane Operation
Proper Electrical Safety (including hot sticks)
Hot Work
Fall Protection Systems
H2S - Hydrogen Sulfide
Respirator Usage
Use of wooden, metal and plastic (fiberglass) portable ladders.
Scaffolding
Vehicle Operation
MR 0175, Metals for Sulfide Stress Cracking and Stress Corrosion Cracking Resistance in Sour Oilfield Environments. National Association of Corrosion Engineers (NACE), (2003, December) [Also ISO 15156, Petroleum and natural gas industries—Materials for use in H2S containing environments in oil and gas production, International Standards Organization (ISO)].
Accident Prevention Guide. International Association of Drilling Contractors (IADC).
Respiratory protection as it relates to oil fields. OSHA Standard Interpretation, (1993, April 14).
29 CFR 1910.134, Respiratory protection. OSHA Standard.
NFPA 70, National Electrical Code. National Fire Protection Agency (NFPA), (2014).
State Programs
Alaska Administrative Code: Title 20 - Chapter 25. Alaska Administrative Code, Alaska Oil and Gas Conservation Commission, Title 20, Chapter 25.
Petroleum Safety Orders--Drilling and Production. Cal/OSHA Standards: California Code of Regulations, Title 8; Chapter 4, Division of Industrial Safety; Subchapter 14.
Chapter 3, Oil and Gas Division. Texas Administrative Code (TAC); Title 16. Economic Regulation; Part 1. Railroad Commission of Texas; Chapter 3.
R614-2. Drilling Industry. Title 34A, Chapter 6, Utah Occupational Safety and Health Act of 1973.
Rules and Statutes. Wyoming Oil and Gas Conservation Commission.
Training Programs
Drilling Technology Series. Petroleum Extension Service (PETEX), University of Texas at Austin.
Unit I: The Rig and Its Maintenance
Unit II: Normal Drilling Operations
Unit III: Non-routine Operations
Unit IV: Man Management and Rig Management
ASC Z390.1, Accepted Practices for Hydrogen Sulfide Safety Training Programs. American Society of Safety Engineers (ASSE), (2006, June).
H2S Training and Information Links
API-U Training. American Petroleum Institute (API).



A.1 Physical Data
Chemical Name: Hydrogen Sulfide
CAS Number: 7783-06-4
Synonyms: Sulfureted hydrogen, hydrosulfuric acid, dihydrogen sulfide
Chemical Family: Inorganic sulfide
Chemical Formula: H2S
Normal Physical State: Colorless gas, slightly heavier than air. Vapor density (specific gravity) at 59°F (15°C) and 1 atmosphere = 1.189.
Auto ignition Temperature: 500º F
Boiling Point: -76º F
Melting Point: -117.2º F
Flammable Limits: 4.3-46 percent vapor by volume in air
Solubility: Soluble in water and oil: solubility decreases as the fluid temperature increases
Combustibility: Burns with a blue flame to produce sulfur dioxide (SO2). Refer to Appendix B Odor and Warning Properties: Hydrogen sulfide has an extremely unpleasant odor, characteristic of rotten eggs, and is easily detected at low concentrations: however, due to rapid onset of olfactory fatigue and paralysis (inability to smell) ODOR SHALL NOT BE USED AS A WARNING MEASURE.
A.2 Exposure Limits
The American Conference of Governmental Industrial Hygienists recommends a Threshold Limit Value of 1 ppm and a short-term exposure (STEL) limit of 5 ppm averaged over 15 minutes. Exposure at the STEL should not be repeated more than four times per day with at least 60 minutes between successive exposures in this range.
A.3 Physiological Effects
Inhalation at certain concentrations can lead to injury of death. The 300 ppm is considered by the ACGIH as Immediately Dangerous to Life and Health. Hydrogen sulfide is an extremely toxic, flammable gas that may be encountered in the production of gas well gas, high-sulfide, high sulfur content crude oil, crude oil fractions, associated gas, and waters. Since hydrogen sulfide is heavier than air, it can collect in low places. It is colorless and has a foul rotten egg odor. In low concentrations, H2S sometimes can be detectable by its characteristic odor; however, the smell cannot be relied upon to forewarn of dangerous concentrations (greater than 100ppm) of the gas because it rapidly paralyzes the sense of smell due to paralysis of the olfactory nerve. A longer exposure to the lower concentrations has a similar desensitizing effect on the sense of smell.
It should be well understood that the sense of smell will be rendered ineffective by hydrogen sulfide, which can result in an individual failing to recognize the presence of dangerously high concentrations. Exposure to hydrogen sulfide causes death by poisoning the respiratory system at the cellular level. Symptoms from repeated exposures to low concentrations usually disappear after not being exposed for a period of time. Repeated exposures to low concentrations that do not produce effects eventually may lead to irritation if the exposures are frequent.
A.4 Respiratory Protection
Respiratory protection shall be worn above the action level. Refer to 6.6 for proper breathing equipment recommendations for oil and gas well drilling and servicing operations involving hydrogen sulfide.


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