HSE Annual Report 2010 (English) - WINTERSHALL

FRACING: A WORLDWIDE PROvEN TECHNOLOGY.
various factors determine how fast and for how
long oil or gas can be produced from a reservoir,
including the geological structure of the reservoir,
the porosity and permeability of the reservoir rock,
and the consistency and viscosity of the hydrocarbons
it contains.
Special techniques are required to extract oil or gas
enclosed in extremely impermeable reservoir rock.
Alongside horizontal drilling, hydraulic fracturing
has been in use around the world for decades and
is being improved all the time. The technique is
used to exploit high-density reservoirs which lie
deep underground.
The process involves injecting water at high pressure
at previously defined points into the solid rock
layers to create fine millimeter-thin cracks in the
rock. Sand mixed with the water (proppants) helps
to keep these cracks open longer. The cracks make
it easier for the hydrocarbons in the reservoir to flow
toward the well for production. This method has
also been used for decades in Germany in crude
oil and gas production from conventional reservoirs,
in drilling for hot water or, in recent years, in geothermal
drilling.
99 % of the fluid mixture used in fracing comprises
water and sand, with around 1% being made up of
chemical additives to ensure that silica sand, for
example, blends with the water. The deliberately
created flow channels stay open long enough and
bacteria do not enter the reservoir. Apart from the
natural seal due to the pressure from the mighty
weight of the several hundred meter thick overlying
rock, usually consisting of clay or salt layers, the
well’s system of steel pipes, which are cemented
into place, form secure barriers against the waterbearing
aquifer layers.
For several decades now, Wintershall has used fracing
to produce crude oil and gas, mostly in tight gas
deposits in Russia, Argentina, the Netherlands and
Germany, with high safety and environmental standards
– without any impact on the environment.
HEALTH SAFETY ENVIRONMENT
Fracing facility drilling hole Leer Z4 in Germany