concept EIA-rapport - Staatsolie

SRK Consulting: Project No: 439414 Staatsolie Pipeline EIA – Draft EIA Report Page 70
pressure in the borehole. A frac-out is more likely to occur during the pilot drilling phase than during
the reaming or pull-in phases.
Impact if the incident occurs
The northern-most entry point is located on land, near the Suritex property. Frac-outs on land are
relatively easy to contain if containment structures (e.g. straw bales, silt fence or plastic sheeting)
are available. Once contained, the escaped mud can be removed and is not expected to pose a
danger to the environment.
Four of the entry / exit points are located on the riverbank. Frac-outs in aquatic environments are
very difficult to contain, because bentonite readily disperses in flowing water. Water-based
(bentonite) drilling mud is generally not toxic, but could result in increased silt content in the
immediate vicinity of the release point. The increased silt load could impact on the aquatic
environment by e.g. smothering fish (by clogging their gills) and / or fish eggs and benthic organisms
when the bentonite settles out (Sacramento Municipal Utility District, 2001).
Should a frac-out occur, the impact will depend on the volume of mud that is released, which
determines the extent of the plume and settlement patterns. However, given the size of the
Suriname River and its dilution capacity, as well as the absence of sensitive habitats or species in
this area, a frac-out that is quickly detected and dealt with is expected to have limited impacts on the
overall system.
The potential impact of an accidental release of drilling mud, should it occur, is rated to be of local
extent (as the mud quickly disperses in the water) and medium intensity (as a large quantity of mud
could be released). Duration is rated as short-term as the system is expected to restore itself after an
incident. The impact is therefore assessed to be of low (negative) significance.
The implementation of the recommended mitigation measures would reduce the likelihood of an
incident (which is not reflected in the rating below) and the volume of mud released in the event of
an accident, thereby reducing the intensity of the impact and the overall significance to very low
(negative) (see Table 6-11).
Table 6-11: Significance of frac-out, should this occur
Extent Intensity Duration Consequence Probability Significance Status Confidence
Without
mitigation
Local
1
Medium
2
Short-term
1
Low
4
Probable LOW -ve Medium
Essential mitigation measures:
To reduce the probability of an incident (does not affect significance rating):
• Closely monitor drilling pressures and penetration rates. Ensure that mud pressure is optimal to penetrate the
formation.
To reduce the impact in the event of an incident:
• Visually monitor the areas around the drilling site for signs of drilling mud leakage, especially while drilling
shallower sections near the entry / exit points.
• Compare the estimated and actual volume of drilling mud returns, to detect escaping mud.
• Cease drilling operations if returns of drilling mud decrease or if a surface release of drilling mud is detected, to
determine what actions need to be taken, in line with stipulations in the EMMP and the spill response plan.
• Comply with any additional mitigation measures contained in the EMMP.
With
mitigation
Local
1
Low
1
Short-term
1
Very Low
3
Probable VERY LOW -ve Medium
6.7.2 Risk: Accidental release of hydrocarbons due to pipeline rupture or leakage
The discussion below is largely based on the QRA undertaken for the Staatsolie Pipeline Project
(Burger 2012) and contributions by Dirk Noordam.
REUT/DALC 439414_StaatsoliePipelineEIA_Draft EIA Report_Final June 2012