Drilling Muds
During drilling,
specially formulated fluids called "muds" are used to cool and
lubricate the drill bit, control pressure and bring the
cuttings (rock or sand from a borehole) back to the surface.
These muds are most commonly based on water (WBM), but in some
cases mineral oil (OBM), or synthetics (SBM) which are
believed to be more biodegradable. Although the use of WBM is
preferred, sometimes OBM or SBM has to be used when drilling
conditions are more difficult.
Inevitably, when drilling with OBM, rock cuttings are
contaminated with oil from the muds. In the past, when working
offshore these cuttings were often discharged of sea, in
accordance with local regulation. Now, when OBM is used
offshore, the spent mud and cuttings are re-injected or
transported to shore for treatment and disposal, or recycling.
The objective of environmental management of drilling
operations is to attempt to minimise the potential
environmental impacts. There are now drilling technologies
that offer opportunities for minimising environmental impacts,
but not all are applicable to every drilling operation.
Produced Waters
When crude oil
is produced from the reservoir it is frequently
accompanied by water. This is either naturally present
or it has been injected into the reservoir to maintain
pressure for production. The proportion of water
produced increases as the oil field matures. Some of
this water is re-injected. If environmental quality
standards are not exceeded the remainder may be
discharged to surface waters. The objective of
environmental management of produced water is to reduce
the quantity and to improve the quality of discharged
produced water.
Produced water is the largest volume of aqueous waste
arising from production operations. The composition of
produced waters varies considerably, but typically may
include: inorganic salts, heavy metals, solids,
production chemicals, hydrocarbons, benzene,
polyaromatic hydrocarbons (PAHs) and on occasions
naturally occurring radioactive material.
The environmental impact of
produced waters depends on the quantity, the components, the
receiving environment and its dispersion characteristics.
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Findings
from the OEF Expert Meeting,
Norway, 2002:
1- There is to date no
universal solution for the
treatment of produced water.
There is a need
for further experience and information
exchange on the use of different technologies
associated
with produced water.
2- Integrated produced
water management
should be based on the following prioritised
strategies: Prevent the production or inject
produced water for reservoir pressure
maintenance, -
Inject produced water for
disposal if energy
requirements do not cause
more environmental tradeoffs Minimise waste
production Treat and dispose remaining
production water.
3- Integrated produced water management
would also
require the minimisation of
hazardous chemicals use in
the treatment
process.
4- Integrated produced water management
should take into
account specific local
conditions and engineering
limitations.
5- The industry should continuously seek to
develop new
technologies, but also implement
an optimal utilisation
of existing technology
and resources including
continuous training
of personnel. |
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What can we do?
Since water is
naturally produced with the oil there is limited potential to
eliminate the source. However, some progress has been
made to limit water production. Water shut-off
technology such as diverting gels can provide an efficient way
of reducing quantities of water requiring treatment.
Reinjection of produced water, either into the reservoir, or
into another formation, may provide a practical optimum
solution if suitable geological formations are available.
New technologies are emerging
for the treatment of produced water, particularly related to
the removal of dispersed oil. These include:
skimming/gas flotations; static; hydrocyclones; mechanical
centrifugation; and gas stripping. Other processes are
being examined for potential application.
[Source:
Environmental Management in Oil and Gas Exploration and
Production  (E&P /
UNEP, 1997)]
More information >> Visit
The International Association of Oil and Gas Producers (OGP)
Catalogue of Publications.
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