Denizen™
Subsea Systems
Minimize crew and vessel
requirements for maximum
economic impact
Features and benefits
Baker Hughes, Process & Pipeline
Services (PPS) offers a comprehensivealternative to the large equipment
spreads that are typically required fordeep water pre-commissioning.
Optimize your project budget with ourpatented Denizen™ Subsea System,
while minimizing weather-relateddelays, reducing the project carbon
footprint and enhancing personnel
safety.
Flooding module			Meet the fleet
The technologies employed on
the subsea systems are mature,reliable and complemented by anexperienced team of techniciansand engineers who see each projectthrough, from concept to execution.
From flooding to hydrotesting andsubsequent dewatering, the Denizen
Subsea Systems have you covered.

Hydrotesting module• Minimize crew and vessel
size requirements• Reduce weather-related
downtime• Perform pipeline flooding
and hydrotesting on multiple pipelines simultaneously• Pig speeds are not restricted by high-pressure losses
from downline friction• Subsea datalogger runtime
up to 30 days

CombinedFlooding/Hydrotesting
module (CTS)				

Coiled tubing downline systembakerhughes.com

Denizen™ flooding module

When a new subsea pipeline is installed, it typically contains
air at atmospheric pressure (1 barA / 14.5 psiA). The first
deepwater pre-commissioning operation is to fill it with sea
water to allow for a hydrotest to be performed. To ensure thepipeline is filled, a single pig is typically used, which will act
as a cleaning and gauging pig.
The Denizen™ flooding module connects to the subsea pig
launcher and, using the ambient hydrostatic head pressure,
will launch the cleaning and gauging pig through thepipeline. This is the “Free-Flooding” phase.

During flooding, the water is drawn through 50 micron
filters and is dosed with chemical(s) to the required
dosage rate. Flowrate is controlled using the onboard
flow control device.
Free-Flooding will continue until the pipeline pressure
reaches equilibrium with the subsea ambient hydrostatic
head pressure – this is approximately 95-99% of thepipeline volume. The final 1-5% is completed using
the onboard pigging pump, which is powered by thehydraulics of a work-class ROV.

During flooding operations,critical information isrecorded on the subsea
dataloggers, including:• Water-flow rate
• Chemical ppm• Water volume• Chemical volume• Differential pressure acrossfilters• Injection pressure

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Denizen™ hydrotesting module

After the pipeline is filled with chemically treated andfiltered water, the system is ready to be hydrotested. With
Denizen, the water to fill the pipeline has been drawn fromthe subsea location, therefore minimal thermal stabilization
time is required. This can represent a significant schedule
reduction compared with water pumped in from a warmer
surface location.
The Denizen subsea test manifold (STM) is deployed andlanded next to the Denizen™ hydrotesting module. With
the hydrotesting module connected to the STM, the STM
connects to the pipeline injection tie-in point via theirrespective hotstabs. ROV will re-arrange the hydrotesting
module and STM valves and begin pressurization. The
Hydrotest Module can be configured with both high andlow flow pumps, capable of pressures up to 1,380 bar(20,000 psi), again the pumps are powered by the ROV
hydraulics. The test manifold of the STM can be adapted toallow testing of more than one subsea system at a time.

Pressurization commences at a rate no greater than 1 bar/min (14.5 psi/min), with intermediate hold periods. Injection
water is treated with the project chemical(s) and, once atthe nominated test pressure, the hydrotesting module andSTM are locked in. Pressure and temperature are monitored
for the duration of the test.
Upon completion of a successful test, the system being
tested is depressurized through the hydrotesting module/
STM in a controlled manner using a flow control device.
The system is configurable to allow for acoustic or optical
data modems to transmit the hydrotest data from thesubsea test locations. Additionally, removable data loggers
can be utilized to recover test data without recovering the
Denizen system.

During hydrotesting
operations, criticalinformation can berecorded, including:• Water-flow rate
• Chemical ppm• Water volume• Chemical volume• Ambient temperature• Pipeline pressure

Copyright 2023 Baker Hughes Company. All rights reserved.
21039
03/2023bakerhughes.com

Denizen™ combined flooding
and hydrotesting system

Both the flooding and hydrotesting module can be
deployed as one multi-functional unit. For certain subsea
pipeline systems, this can yield a significant reduction in
overall vessel time. The deeper the water, the more timeconsuming crane and ROV deployment operations canbe. With this in mind, the Denizen system is designed to

Copyright 2023 Baker Hughes Company. All rights reserved.
21039
03/2023

be flexible and efficient, therefore minimizing the numberof deployments required on a project. Furthermore, theability to combine the flooding and hydrotest modules also
reduces vessel deck space requirements and equipment
mobilization costs.

bakerhughes.com

Denizen™ coiled tubing
downline system (CTS)

Traditionally, deepwater vessel-based pre-commissioning
spreads have been connected to a subsea pipeline via
a rubber hose or small-bore (<2”) coiled tubing string.
This temporary connection acts as a conduit for the precommissioning fluids / gases and is known as a “downline”.
The downside of the rubber hose downline is the timeand labor-intensive deployment and recovery procedure.
Further, the multiple hose joins in the downline create achallenge in mitigating the leak paths. With small borecoiled tubing systems, the pressure losses in deepwater
either limit the pigging parameters or required a large andpowerful pumping spread to overcome the losses.
The Baker Hughes, Process & Pipeline Services Denizen
coiled tubing downline system (CTS) was designed
to overcome the shortfalls of the traditional downline
methods.
Our CTS is capable of operating in water depths up to 3,000m (9,842 ft) and designed for large diameter coiled tubing
strings of 2.88” or 3.5”.
DNV-certified to allow offshore lifting, the Baker Hughes CTS
is road transportable in two loads, and the flexible frame
allows use on a wide variety of vessels, either through amoonpool or over the side.

Some of the benefits of using our CTS include:•

Large downline diameter allows high flow rates at low
pressure drops.

•

One continuous coil section from vessel to seabedminimizes leak paths.

•

Self-supporting coil string allows for fast deployment
and recovery with minimal personnel•

PPS experience in all deepwater arenas around the
world

•

The deployment skid and over boarding structure are
specifically designed for vessel and pipeline precommissioning applications•

The module can be used to flood and hydrotest fromthe surface to the deepwater pipeline, delivering therequired fluids and compressed gases required during
pre-commissioning•

Coil tubing is collapse resistant at deepwaterhydrostatic pressure, allowing pipelines to be fully
depressurized.

•

A flexible hose bundle connection from the end of
the coil string to the pipeline is provided. The allows
for quick connection to the pipeline by ROV. Swivels,
buoyancy and emergency breakaway functionality isalso included.
• DNV-certified lifting frames

Copyright 2023 Baker Hughes Company. All rights reserved.
21039
03/2023bakerhughes.com