Page 16 - Industrial Plants

Figure 2 - 3D Model
for pipeline string
preparation works
HDD Preparation Works Design (the longest of about 1,100 metres) from the Southern

side. This was primarily driven by the limitation of
The selected HDD profile had a total length of 1,842 earthworks and environmental impact and supported
metres, with a horizontal distance of 1,794.4 metres. by the low risk of bore collapsing, as it required two
The feasibility of the HDD was confirmed in August tie-in welds during the pullback.
2021 when a 1,622 metres exploration borehole had The selected pullback ROW was challenging, featuring
been successfully drilled along the actual pilot hole hilly and rocky terrain with horizontal and vertical
alignment from the South pad to about 200 metres deviations, a 17 degree slope 220 metres long, the
from the North Pad exit point. crossing of two watercourses and one road. The
The exploration borehole confirmed a low risk of frack overbreak section, spanning 280 metres with a
out and bore hole collapse within the rock strata, maximum height of 15 metres to allow the pipeline
increasing to moderate risk in the surficial layers (up to string to pass through the contingency thruster and
10-14 metres depth from the drilling surface at both meet the 11 degree entry angle, was supported by
North and South pads). To manage this risk, installation seven cranes (six 120 tons cranes and one 160 tons
of 60 metres – 70 metres casing pipe was the selected crane) as well as four side booms. The remaining 820
mitigation measure. metres of the drag section had been placed on 100
Particular attention was given to the design of the roller supports designed for the pullback and hydrotest
pullback section and the fabrication of the pipeline loads (40 tons).
string, as the area surrounding Dry Gulch featured To ensure a successful pullback, a comprehensive
uneven terrain, steep slopes, several creeks, and a study for the string preparation was performed,
winding right-of-way, due to environmental constraints. including an integrated 3D Model/Finite Element
Analysis (FEM) Analysis.
“Particular attention was given to
the design of the pullback section Additionally, a FEM analysis was conducted to analyze
and the fabrication of the pipeline both the static and dynamic behaviour of the pipe
string, as the area surrounding Dry string during the pullback phase. In particular, FEM
Gulch featured uneven terrain, steep simulation produced the following results:
slopes, several creeks, and a winding • Verification that the maximum stress induced in
right-of-way, due to environmental the string during lifting and pulling operations was
constraints within acceptable limits, guaranteeing the integrity
of the pipe string;
By the end of 2021, a detailed pullback study analysed • Definition of the distribution of the equipment and
several options, including single or multiple strings from the vertical and lateral loads required for
both the Northern and Southern sides of the gulch. The equipment sizing and design additional anchoring
final selected option was to pull three pipeline strings systems;

IndustrIal Plants - May 2024
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