ENVIRONMENTAL STATEMENT BARDOLINO DEVELOPMENT

Bardolino Development Environmental Statement
A valve skid will also be installed alongside the existing Howe manifold, with dimensions 4 m
x 5.5 m x 3.5 m. The valve skid protection structure will also be secured to the seabed using
piles, of smaller diameter and length than those required for the manifold structure.
The total area of seabed which will be covered by the tree, manifold and valve skid will be
approximately 56 m 2 .
The tree, manifold and valve skid will be connected to the installed pipelines using flexible
jumpers and spool pieces. Concrete mattresses will be used to protect these items of subsea
infrastructure. The mattresses planned for use are likely to be standard density concrete of
dimensions 6 m x 3 m x 1.5 m, with mattresses 6 x 3 x 0.3 m in dimension in areas of high
risk to dropped objects. It is anticipated that 60 mattresses will be required at the Bardolino
location to protect the manifold structure and tree, and 70 mattresses will be required at the
Howe location. The total area of seabed that would be covered by the mattresses would be
approximately 0.0023 km 2 .
3.5.5 Pre-commissioning and testing the pipelines, manifold, valve skid and tree
At this stage the full extent of the subsea pre-commissioning and commissioning is not fully
defined. A worst-case estimate has therefore been made of the planned chemical use and
discharge during pre-commissioning and commissioning activities for the 6” production
pipeline, 3” gas lift line and umbilical. Efforts will be made to ensure that chemical use and
discharge is minimised as far as possible through the detailed design stage of the project.
In summary, pre-commissioning of the pipelines will be undertaken in three main phases:
• pipeline flooding/ cleaning / gauging (i.e. monitoring pipe wall thickness);
• pipeline system hydro-testing; and
• de-watering in preparation for commissioning.
When installed, the pipelines will contain atmospheric air. Immediately after installation, the
6” production pipeline will be flooded with water to ensure stability on the seabed for
trenching. The production pipeline may also be gauged during this operation to verify that
there are no dents or buckles that could impair the integrity of the pipeline. The 3” gas lift
pipeline will be subjected to a high velocity flush to ensure stability on the seabed for
trenching and also verify that there are no dents or buckles that could impair the integrity of
the pipeline.
The water used for flooding, flushing and (optional) gauging of the pipelines will be filtered
and dosed with the chemicals required to maintain the integrity of the pipelines during
subsequent pre-commissioning and commissioning activities. These chemicals may include
corrosion inhibitor, biocide and oxygen scavenger. Some treated water will be discharged to
the environment during the flooding, flushing and (optional) gauging operation. The water will
be seawater for the gas lift pipeline and potable water for the production pipeline.
Following post-trench gauging, both pipelines will be subjected to a hydrostatic strength test
to 1.5 times the design pressure for a period of 24 hours. The water used for the strength
testing will be filtered and dosed with chemicals to maintain the integrity of the pipelines
during subsequent pre-commissioning and commissioning activities. These chemicals may
include corrosion inhibitor, biocide, oxygen scavenger and fluorescent dye. Some treated
water will be discharged to the environment during strength testing activities. The water used
for strength testing will be seawater for the gas lift pipeline and potable water for the
production pipeline.
On completion of the hydrostatic strength testing, the ends of the production pipeline would
be filled with a water-based gel sealer gel to minimise seawater ingress during tie-in. A slug
of gel would be injected into one end of the pipeline and then a slug of gel of half this volume
would be injected into the opposite end. Some treated potable water will be discharged to the
environment during the injection of the first slug and some gel will be discharged to the
environment during injection of the second slug.
The manifolds and tie-in spools to connect the manifolds, wells and pipelines will then be
installed. All spools, and all manifold production and gas lift pipe work, will be pre-flooded
with a glycol-based gel onshore prior to offshore shipment, deployment and installation. This
April 2008 Page 3-21