Introduction v Soluble in water, crude oil or petroleum

Introduction

H2S is colorless, toxic, and flammable gas. It’s
found in number of PDO operation area. PDO assets in encounter varying
concentration and pressures of H2S. Currently harweel ; birba and Al Noor have
the highest concentrations of H2S.Hydrogen sulphide occurs naturally in the
earth in crude petroleum, natural gas reservoirs, volcanic gasses and hot
springs, hydrogen sulphide is also produced from the breakdown of human and
animal wastes by bacteria, petrochemical and chemical refineries, waste water
treatment facilities, also tar and asphalt manufacturing plants. H2S in upstream
oil and gas comes from the original reservoir, as a result of the hydrogen
source material and conditions under which it was converted to oil and gas.

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Prolonged injection of water into a hydrocarbon
reservoir may result in ” souring” of the fluids, due to the action of
sulphate reducing bacteria introduced during the injection process. Any H2S
will be produced with the fluids. H2S is extremely toxic within PDO assests
encountered during normal operation ranging from drilling, well testing,
flaring, production operation, gas injection through to product export , e.g.
drilling/well works on high level H2S wells, breaking containment on process
equipment with H2S in the fluids, confined space entry, maintenance operation,
sulphur removal system, water Knock-Outs, and Vaccum truck vents. The operation,
maintenance and surveillance of process containing hydrogen sulphide hazards
shall be such as to prevent a potentially hazardous situation from developing.
In the event of loss of control hydrogen sulphide hazard, the design and
operation practices should assure the early detection and rectification of the
potentially hazardous situation.

Characteristics or properties of hydrogen sulphide
(H2S)

v  It smells like rotten eggs
at low concentration and causes you to quickly lose sense of small. (100ppm). ,typically
called sour gas

v  Colorless

v  Explosive

v  Corrosive. Can cause
causes severe stress cracking or other metals

v  Soluble in water, crude
oil or petroleum fractions. (natural gas, petroleum ether, gasoline, kerosene,
fuel oil, lubricants and asphalt or coke

v  Slightly heavier than air
and may accumulate in low lying areas and confined space

v  Burns with a blue flame to
form sulpher dioxide SO2 which is a toxic gas

v  Toxic at extremely low
concentrations

v  Venting

v  Broad spectrum toxin- can
injure most body tissues

v  Iron sulpide – pyrophic

v  High concentration-
nervous system impact

v  Tissues the have high
demand are especially vulnerable

v  Rapidly stops oxygen
access for cellular metabolism

 

The flammable range for H2S is between 4.3% and
46% of gas by volume in air. When the gas is burned. Such as during flaring
operations, sulpher dioxide is formed which readily combines with water to form
sulphuric acid in the atmosphere (acid rain).

 

 

Factors influencing toxicity

The way in which H2S affects a person depends
on the following factors

ü  Duration- the length of
time the individuals is exposed

ü  Intensity- the
concentration of exposure

ü  Susceptibility- the
individuals physiological make-up

ü  Frequency- how often is
exposed

At certain (600- 1000 ppm) immediate knockdown
occurs

Other factors include

ü  State of health

ü  Age of the person

ü  Route of exposure

ü  Workplace environmental factors

ü  Previous exposure level

Exposure to hydrogen sulphide causes death by
poisoning the respiratory system at the cellular level. Symptoms from repeated
exposure to low concentration usually disappears after not being exposed for
period of time. Repeated to low concentrations that do not effects eventually may
lead to irritation if the exposure are frequent

Some individauls can extremely vulnerable to
H2S and its by- products.

The ability to tolerate exposure is reduced by
health conditions such as:

o  
Emphysema: disease of the lungs

o  
Bromchial asthma: asthma is a disorder that cause the airways of the
lungs to swell and narrow, leading to wheezing, shortness of health, chest
tightness, and coughing.

o  
Anemia: a condition in which the body does not have enough healthy red
blood. Red blood cells provide oxygen to body tissues

o  
Epilepsy: a brain disorder in which a person has repeated seizures

o  
Angina pectoris or other coronary artery disease: chest pain or
discomfort that usually occurs with activity or stress.

o  
Progressive or sever hypertension; high blood pressure.

Individuals who have consumed alcohol 24 hours
of exposure are known to have been overcome by unusually low concentrations of
H2S

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