concept EIA-rapport - Staatsolie

SRK Consulting: Project No: 439414 Staatsolie Pipeline EIA – Draft EIA Report Page 16
Figure 3-3: Schematic drawing of drilling operation at entry points
3.3.3.2 Alignment
The approximately 4 km of Suriname riverbank that fall within the study area accommodates
more than ten jetties and structures. Most of these are constructed on pilings. The typical
piling depth for jetties is about 18 m below riverbed. Newer and larger jetties may have been
founded on longer piles, penetrating up to about 24 m below the riverbed (Visser & Smit
Hanab, 2011).
The pipeline will be aligned such that the horizontal, deepest part of the pipeline runs
underneath the piles wherever possible or that the pipeline runs between the piles where
necessary. As a general rule, the pipeline must be a minimum distance of 2 m from vertical
structures or 4 m if beneath such structures. Known plans for the future extension of existing
or construction of new jetties will be taken into account in the alignment - the pipeline will not
impose a constraint on such plans.
HDD can achieve accuracy of less than 1 m deviation from the planned path per 1 000 m
distance drilled (IMAR, not dated). For the longest drill section of 1 640 meter, this implies a
maximum deviation of some 1.5 m. This will be taken into account when the detailed drill path
is determined.
3.3.3.3 Drilling mud
Drilling mud is used to:
• Cool, lubricate and clean the drill head during the drilling operation;
• Suspend and carry drill cuttings out of the bore path; and
• Stabilise the bore path prior to and during pull back.
A benign, non–toxic water-based mud consisting of a mixture of approximately 95% water and
5% bentonite clay will be used. An estimated 170 tons of bentonite, equating to 3 400 tons of
drilling mud, will be used. The precise composition of the drilling mud will be chosen based on
the soil conditions. Additives can be used in small amounts to influence the viscosity and other
properties of the drilling fluid, and could include cement, Pac-L
(Sodiumcarboxymethylcellulose), Multisorb (a superabsorbent polymer) and N-seal (a silicate).
During HDD drilling the borehole is filled and kept filled with the drilling mud. After the pull-in of
REUT/DALC 439414_StaatsoliePipelineEIA_Draft EIA Report_Final
June 2012