Environmental Statement - Maersk Oil

6 ‐ 2
Balloch Field Development Environmental Statement
Section 6 Accidental Spills
environmental damage to biodiversity, water and land from specified activities and remediation
of environmental damage for all other activities through fault or negligence.
6.1.2. LIKELIHOOD OF A BLOWOUT SCENARIO
The International Association of Oil & Gas Producers has issued datasheets (OGP, 2010) on the
likelihood of blowouts for offshore operations of ‘North Sea Standard’. The North Sea Standard refers
to operations that are performed with the Blowout Preventer (BOP) installed (including shear ram), as
well as where the ‘two barrier principle’ to stopping a potential release is followed. The dataset is
derived from the International SINTEF blowout database. Blowout frequencies have been calculated
per well drilled in the North Sea and are not annual frequencies. Table 6‐1 indicates that for gas high
pressure/high temperature (HP/HT) reservoirs, the likelihood of a blowout is higher in than in oil
reservoirs such as Balloch.
Table 6‐1 Blowout and well release frequencies for offshore operations of North Sea Standard (OGP, 2010).
Operation Category Gas Oil Unit
Development drilling (Oil) Blowout ‐ 4.8 x 10 ‐5
Development drilling (HP/HT) Blowout 4.3 x 10 ‐4
Development drilling shallow gas (topside) Blowout 4.7 x 10 ‐4
Development drilling shallow gas (topside) Blowout 7.4 x 10 ‐4
Per well drilled
‐ Per well drilled
‐ Per well drilled
‐ Per well drilled
Tina Consultants Ltd (2010) report that in the UKCS during the period 1975 ‐ 2007 a total of 17,012
tonnes of oil (excluding regulated discharges from the produced water systems, but including spills of
base oil and oil based mud (OBM)) were discharged from 5,826 individual spill events. Figure 6‐1
shows volumes spilled and number of reported spills from 1991 to 2009 (DECC, 2009b). Analysis of
spill data between 1975 ‐ 2005 (UKOOA, 2006) shows that 46 % of spill records relate to crude oil,
with 18 % relating to diesel and the other 36 % relating to condensates, hydraulic oils, oily waters and
others.
Spilled amount (tonnes)
900
800
700
600
500
400
300
200
100
0
1991
1992
Figure 6‐1 Volume of spilled oil and number of spills in UKCS waters.
1993
1994
1995
1996
1997
1998
1999
2000
Year
2001
Total amount spilled (tonnes) Total number of oil spill reports
2002
2003
2004
2005
2006
2007
2008
2009
500
450
400
350
300
250
200
150
100
50
0
Number of spills