Effects of Drilling Fluid Exposure to Oil and Gas Workers ...

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Research Journal of Applied Sciences, Engineering and Technology 2(8): 710-719, 2010
ISSN: 2040-7467
© M axwell Scientific Organization, 2010
Submitted date: August 17, 2010
Accepted date: September 22, 2010
Published date: December 10, 2010
Effects of Drilling Fluid Exposure to Oil and Gas Workers Presented
with Major Areas of Exposure and Exposure Indicators
E. B roni-Bediak o and R. Am orin
Petroleum Engineering Department, University of Mines and Technology, Tarkwa, Ghana
Abs tract: Drilling fluid is any fluid which is circulated through a well in order to remove cuttings from a
wellbore. The y are u sed b roadly in the oil and gas industry, on exploration rigs, and are critical to ensuring a
safe and productive oil or gas well. During drilling, a large volume of fluids are circulated through the well and
into open , partially enclosed or completely enclosed systems at elevated temperatures. When these drilling
fluids are agitated during circulating process there is significant potential for chemical exposure to workers and
subsequent health effects. This study seeks to identify major areas of drilling fluid exposu re and hea lth hazard
associated with th e use of drilling flu id. Th e stud y also prese nts som e cha llenge s in setting drilling fluid
exposu re standard which has always not been given the same attention or concern as effects and risk
management of drilling fluid. Some exposure indicators are also presented.
Key w ords: BTEX (Benzene, Toluene, Ethylbenzene, Xylene), dermatitis, drilling fluids
down the drill string, through the bit, and back to the
surface via the annulus ASME (2005) and Gardner (2003)
In deciding on the type of drilling flu id syste m to use
as show n in Fig . 1 (HW U, 20 09). A ccord ing to
in any drilling operations, there must be proper and an
Baker (1995), D arley and G ray (1988 ), drilling fluid must
extensive planning of the well in order to select the best
fulfil man y functions in order for a well to be drilled
drilling fluid to drill holes that are usable, safe and of
successfully, safely, and economically. The most
minimal cost. Safety sh ould be the highe st priority in the
important functions are:
selection of the type of drilling fluid to use during and
after drilling. Failure to stress crew safety h as resu lted in
Remov e drilled c uttings from u nder the bit.
loss of life and burned or permanently crippled
Carry those cuttings out of the hole.
individuals (C hukw u, 2008).
Suspend cutting s in the flu id when circulation is
Due to the nature of drilling operations in drilling
environments, typically in the areas such as mud
Prevent the bore hole from collapsing or caving in.
preparation, breaking out of pipes, addition of pipes to the
Protect producing formations from damage which
strings and other related issues, drilling engineers need to
could impair production.
conduct comprehensive risk ass essm ents o f drilling fluid
Clean, cool, and lubricate the drill bit etc.
systems, considering all its associated problems
(James et al., 2007). This risk asses sme nt inclu des h ealth
Types of drilling fluid: According to OGP, (2003), and
aspects, environmental and safety a spec ts, so as to be ab le
Neff et al. (2000), there are two primary types of drilling
to strike an appropriate balance betw een th em s o to
fluids: W ater Based Fluids (WB Fs) and Non-Aqueous
minimize the exposure of drilling fluids to drilling
Drilling Fluid s (NA DF s) or N on-A cqueous Ba se Flu id
operators, environmental effects and other related issues.
(NA BFs).
This study seeks to identify potential areas of drilling
fluid exposure, health hazard associated with the use of
Water Base d Fluids (W BFs ): WB Fs consist of water
drilling fluid and som e expos ure indicators that could be
mixed with bentonite, clay and barium sulph ate (ba rite) to
used in place of the ye t to be established h ealth expos ure
standards of drilling fluids.
control mud density and thus, hydrostatic head. Other
substa nces are added to gain the desired drilling
properties. The se ad ditives in clude thinne rs (e.g.,
lignosulphonate, or anionic po lymers), filtration control
Drilling fluids and its functions: A drilling fluid, or
agen ts (polyme rs such as ca rboxymethyl cellulose or
mud, is any fluid that is used in a drilling opera tion in
starch) and lubrication agents (e.g., polyglycols) and
which that fluid is circulated or pumped from the surface,
numerous other compo unds for specific functions.
Corresponding Author: E. Broni-Bediako, Petroleum Engineering Department, University of Mines and Technology, Tarkwa,

Res. J. Appl. Sci. Eng. Technol., 2(8): 710-719, 2010
Fig. 1: Circulating system
Non-Aqueous Drilling Fluid s (NADF s): NA DFs are
which conta in leve ls of total aromatics below
emulsions whe re the continuous phase is the Non-
0.5% and polycyclic arom atic hydrocarbon
Aqueous Bas e Fluid (NA BF ) with water and chemicals as
(PAH) levels below 0.001 %, according to
the internal phase. T he NAD Fs comprise all non-water
the OGP definition.
and non-water dispersable base fluids. Similar to W BFs,
additives are used to control the properties of NAD Fs.
Emu lsifiers are used in NA DF s to stab ilise the w ater-in
oil emu lsions. Non-aqueous drilling fluid can further be
Field findings:
group into 3 (James et al., 2007):
Workers mostly affected by drilling fluid exposure:
W orkers mostly affected by drilling exposure include the
Group I:
high-arom atic content fluids. This category
includes crude oil, diesel and conventional
mineral oils. These fluids are refined from
Derrickman: These people are responsible for mixing
crude oil and contain levels of total aromatics
and adding chemical to the drilling fluid and also
b etw ee n 5 an d 3 5% .
collecting samples. They also monitor pum ps an d han dle
Gro up II: m e d i u m - a r o ma tic c o n t e n t f l u id s . T h i s
pipes tripping activities.
category contains products produced from
crude oil with levels of total aromatics
Mud engineer: Mud engineer may periodically check the
between 0.5 and 5% and is often known as
mud by measuring its viscosity, density, and other
‘low toxicity m ineral oil’.
Group III: low/negligible-aromatic content fluids. This
group includes fluids produced by chemical
Roughneck: These people make pipe connection during
reactions and highly refined mine ral oils
tripping activities from the drill neck, collect cores and

Res. J. Appl. Sci. Eng. Technol., 2(8): 710-719, 2010
cutting samples and also perform the general house-
Deep sea diver: People who make contact with discarded
cuttings on the sea bed during operations.
Laboratory supervisor: Responsible for periodical
checks on additives etc.
M otor Man: People responsible for all the motors,
generators and general maintenance of equipment at the
working area.
Major areas of drilling fluid exposure: Exposures are
mos tly encountered in a typical drilling environment
during drilling operation. The following are as we re
identified during the study as the major areas of drilling
fluid exposure:
Fig. 2: Aerosol and vapour/mist exposure at shale shaker house
Shale shaker house
Drilling floor
Mud pit system
Sack room
Laundry services
Deck operations
Sha le shaker house: Workers may be exposed to drilling
fluids either by inhaling aerosols and vapours/mist or by
skin contact (Fig. 2). Other form of major exposure
opportunities identified includes:
W ashing shale shak er with high-p ressure guns using
a hyd rocarb on-b ased fluid
Cleaning and changing shale shaker screens
Che cking the sh aker screen s for wears
Solid and Liquid separation
Mechanical agitation of the Shale shaker
Fig. 3: Mud pit system
Drilling floor: Contact with drilling fluids as well as
lubricants, pipe d ope, hydra ulic oils, etc. by roughnecks
and other personnel on the drill floor is predomina ntly
dermal contact. This can be prolonged and repetitive due
to the manual nature of the work involved. In most cases
contact may be through manual handling of unclean pipes
during breaking out of pipes, preparing to break out pipes,
handling of tubular, lowering of drill pipe, sprays, and
spills from cleaning operations and high pressure
Mud p it s ys te m : The mud is monitored throughout the
drilling process. A mud engineer and or the Derrickman
may periodically check the mud by me asurin g its
viscosity, density, and other properties. The mud engineer
can be ex pose d to bu rns, or p hysic al injury caused by
Fig. 4: Additive mixing at sack room
contact with skin or eyes. Persons in the area are ge nerally
needed to perfo rm less com plicated tasks but on regular
explosions or violent reactions from chem ical mixed
basis with the potential of inhalation hazard and also
imprope rly (Fig. 3).

Res. J. Appl. Sci. Eng. Technol., 2(8): 710-719, 2010
Sack r oo m : Gardner (2003), reported that although base
drop lets of the hydrocarbon fraction used. This
oils have attracted the most attention, worke rs are
hydrocarbon fraction may c ontain add itives, sulphur,
poten tially expo sed to a range of pa rticulates , especially
mono-aromatics and/or polyc yclic aroma tics. It should be
during powder hand ling of v arious additiv es esp ecially
noted that although the hydrocarbon fraction may conta in
barium sulphate in the sack room. The hand ling of these
negligible amounts of known hazardous constituents such
various pow dered products can cause exposure of mud
as Benzene, toluene, ethylbenzene and xylenes (BTEX) at
enginee rs and other operators in the sack room to both
low boiling point, these will evaporate at relatively higher
skin contact and inhalation. In practice, the potential
rates po tentially re sulting in highe r conc entratio ns in the
problems of exposu re and the opportunities for control are
vapour phase than anticipated.
much the same as in comp arable situations ons hore
McD ougal et al. (2000), also reported that petroleum
(Fig. 4; Saleem and R oss, 2009 ).
distillates such crude oil, diesel oil (Group I-Non Aqueous
Fluids) have been associated with renal, hepatic,
Laundry: Ineffective cleaning of personal protective
neurologic, immunologic, and pulmonary toxicity when
equipment may leave residues of drilling fluids on the
they are inhaled or ingested. They are also irritating to the
clothes which may be exposed to the skin. Cauchi (2004)
skin and mucus membrane. ATSDR (1999a) reported
reported that detergent used by the rig laundry service
some health effects associated with inhalation
may not be efficient or ada pted to remo ve O il Base Mud
exposure as:
(O B M ) or Non-Aq ueous Drilling Fluid (NADFs)
derivatives from the pro tective c lothing , resulting in
Ne urological effects
chemical accumulation into the clothing fibers.
Carcinog enicity
Haematological effect
Hea lth effect associated with drilling fluids contact:
Immunological effect
The risk of adverse h ealth effects from drilling fluids is
Lym pho reticular e ffects
determined by the hazardous components of the fluids,
Pulm onary effec ts
additives and by huma n exposure to those components.
Skin irritation and contact dermatitis are the most
Dermal exposure: M ost ch emic als are readily absorbed
common health effects observed from drilling fluids
through the skin and can cause other health effects and/or
exposu re in human beings, with headache, nausea, eye
contribute to the dose absorbed by inhalation of the
irritation, and coughing seen less frequently. The effects
chemical from the air. When drilling fluids are circulated
are caused by the physico-chemical properties of the
in an open system with agitation, there is a high likelihood
drilling fluid as w ell as the inherent properties of drilling
of dermal exposu re resu lting in de rmatitis and sk in
fluid additiv es, and are dependent on the route of
irritation. The potential dermal exposure is not limited to
exposure such as dermal, inhalation, oral and others.
the hands and forearms, but extends to all parts of the
body. Actual exposure d epen ds on the drilling fluid
Inhalation exposure: Gardner (2003) reported that the
system and the use of Personal Protection Equipment
potential chemical changes in drilling during use and
(PPE). Many studies indicate that absorption of che mica ls
recycling can re sult in more toxic substance being
through the skin can occur without being noticed by the
released. Since drilling fluids are subjected to elevated
work er. In ma ny ca ses, sk in is a more significant route of
temperatures and increased pressures, there has been a
exposu re than the lung (OSH A, 200 9).
concern that organic components might break down, or
chemical reactions might occur, to form more toxic
De rm atitis and irritation: Skin contact with drilling
substances. There was a particular co ncern that base oil
fluids or mud can also cause inflammation of the skin,
high in arom atics m ight co ntain, o r form P olycy clic
referred to as dermatitis. Signs and symptoms of
Aro matic Hydrocarbons (PAHs), while muds (drilling
derm atitis can include itching, redness, swelling, blisters,
fluids) based on alkyl benzenes might break down to yield
scaling, and other changes in the normal condition of the
free benzene.
skin (Fig. 5, An ony mou s, 200 9). O n the d rill floor, in
OGP and IPIECA (2009) also reported that drilling
particular, skin contamination can be broad, but
fluids are often circulated in an open system at elevated
occasionally dermatitis also occurs in divers who make
temperatures with agitation that can result in a
contact with discarded cuttings on the sea bed
com bination of vapours, aerosol and/or dust above the
(Ormerod et al., 1998).
mud pit. In the case of wa ter-based fluids the va pours
Petroleum hydrocarbons will remove natural fat from
comprise steam and dissolved additives. In the case of
the skin, w hich results in drying and cracking. These
non-aqueous drilling fluids the vapours can consist of the
conditions allow com pou nds to perm eate throug h the skin
low boiling-point fraction of hydrocarbons (paraffin,
leading to skin irritatio n and derm atitis. Som e indiv iduals
olefins, naphthenes and aromatics), and the mist contains
may be especially susceptibility to these effects. Skin

Res. J. Appl. Sci. Eng. Technol., 2(8): 710-719, 2010
likely to be exposed, together with a risk of expos ure
then, the following hierarchy of princip les of co ntrols
should be considered:
Elimination (not feasible)
Substitution (low toxic base oils, WBFs)
Engineering controls(greater enclosure)
Adm inistrative controls (rotate jobs, hygiene
measures, education of Control of Substances
Hazardous to Health (COSHH ), skin management
systems and improved laundry practices)
Personal protective equipment (chemical resistant
slicker suit and gloves)
Fig. 5: Dermatitis of the hands
Challenges in setting drilling fluid exposure standards:
irritation can be petroleum hydrocarbons, spec ifically
The health expo sure sta ndard of drilling fluid d uring oil
with aromatics and C8-C14 paraffins. Petroleum streams
and gas operations has always not be given the same
containing these compounds, such as kerosene and diesel
attention or concern as its effects and risk management
(gas oil), are clearly irritating to skin. T his is suggested to
guidelines due to the following challenges:
become malignant caused by the paraffins, which do not
readily penetrate the skin but are absorbed into the skin,
Drilling fluids are com plex m ixtures of varia ble
hereby causing irritation (M cD oug al et al., 2000). Linear
alpha olefins and esters commonly used in drilling fluids
It unclear about the longer term of health effect
are only slightly irritating to skin, whereas linear internal
There is no scientific basis on which to set hea lth
olefins are no t irritating to sk in.
exposure limit
In additio n to the irritancy o f the drilling fluid
Exposure must be made up of all pertinent fractions
hydrocarbon constituents, several drilling fluid additives
such aerosol, vapo ur, etc., and all variatio n in
may have irritants, corrosive or sensitizing properties
(Cauchi, 2004). For example calcium chloride has irritant
Expo sure should reflect the level that can be achieved
properties and zinc bromide is corrosive whereas a
using good practices
polyamine emulsifier has been associated with sensitizing
properties. Although water based fluids are not based on
Exposure indicators: In spite of the challenges of setting
hydrocarbons, the additives in the fluid may still cause
health exposure standards of drilling fluid expo sure to oil
irritation or dermatitis. Excessive exposure under
and gas workers, Agency for Toxic Substances and
conditions of poor personal hygiene may lead to oil acne
Disease Registry (ATSDR ) has researched into the
and folliculitis (OGP and IPIECA, 2009). ATSDR (1997)
BTEXs which are released as a result of drilling fluids
concluded that it is reasonable to expect that adverse
during agitation under high pressures and temperature.
haematological and immunological effects might occur
The study presents these findings by ATSDR as an
following dermal exposure to benzene.
Expo sure Indicator or Lowest Observed Adverse Effect
Level (LOAEL) for drilling fluid ex posu re to op erators to
Oral exposure: Ora l expo sure n egligib le as co mpa red to
help reduce the dangers of abnormal drilling fluids
the other exposure routes such dermal, inhalation and
exposure. Appendices A and B sho wed for exposu re
others. Oral exposure may occur when hands are not well
washed before they are used to handle thing like cigarette.
Da ta for the oral route of exposure are less extensive.
The BT EX s cau se ne urological effects, ge nerally central
nervous system depre ssion, by the oral route. Renal and
hepatic effects are also seen with oral exposure to these
This study revea led the majo r areas of drilling flu id
compounds. Renal effects are the basis for the
exposu re as setting of pipe at the drill floor, manual
intermediate. The hepatic effects tend to be mild,
handling of sack at the sack room and other related issues
including increased liver weight and cytochromes.
as major areas of drilling fluid exposure.
Benzene causes hae mato logica l effects b y the o ral route
Findings also revealed tha t, the major health ha zard
that is similar to those seen from inhalation exposu re
such as dermatitis, body irritation, ne urological effects
(ATS DR , 1999a).
etc., assoc iated w ith drilling fluids expo sure is m ainly
through inhalation, skin contact and oral exposure.
Hierarchy of principle o f contro l: If hazardous
Expo sure Indicator or LOAE L could serve as
comp onents of d rilling fluids are identified at each stage
guidelines for oil and gas worker so as to prevent the
of any drilling operation or areas whe re drilling fluids are
dangers of abnormal exposure of drilling fluids.

Res. J. Appl. Sci. Eng. Technol., 2(8): 710-719, 2010
Appendix A
a : A r o m at ic E C - E C exposures associated with health effects-inhalation-benzene, modified after ATSDR (1997)
b: Aromatic EC -EC exposures associated with health effects-inhalation-toluene, modified after ATSDR (2000)

Res. J. Appl. Sci. Eng. Technol., 2(8): 710-719, 2010
c : A r o m at ic E C - E C exposures associated with health effects-inhalation-mixed xylenes, modified after ATSD R (1999a)
d : A ro m a ti c E C - E C exposures associated with health effects-inhalation-ethylbenzene, modified after (ATSDR , 1999b)

Res. J. Appl. Sci. Eng. Technol., 2(8): 710-719, 2010
Appendix B
a : A r o m at ic E C - E C exposures associated with health effects-oral-benzene, modified after ATSDR (1997)
b : A ro m a ti c E C - E C exposures associated with health effects-oral-xylenes, modified after ATSDR (1999 a)

Res. J. Appl. Sci. Eng. Technol., 2(8): 710-719, 2010
c : A r o m at ic E C - E C exposures associated with health effects-oral –toluene and ethylbenzene, modified after ATSDR (1999 a)
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