Paper on the developments of ROV hydrate remediation skids, and non-ROV hydrate skids. A market comparison. Authored by Fernando C. Hernandez for Wrights Well Control Services

1. New Developments for
Ultra Deepwater Hydrate Remediation Technology in the
Gulf of Mexico
Authored By: Fernando C. Hernandez

2. Hydrate Remediation WWCS
Introduction
Hydrate Formation
Hydrates (a freezing of condensate and other liquids, mixed with hydrocarbons, solids and gases) occurs
when a combination of temperature and pressure is reached in a subsea pipeline or other asset. The
Hydrate Formation Curve is illustrated in the graph below.
Hydrate Diagnosis
There are different methods to indentify hydrate has formed in a subsea asset:
The emergence of a pressure differential between two transducers within the same circuit,
where pressure builds higher, and or lower than a sensor which is located within the same
circuit. Examples of such locations are on a PLET, Pipeline, Riser, Tree, Umbilical, BOP, etc.Note:
multiple hydrates can form within a single circuit
Loss of continuity within the same subsea assets will reveal that there is no longer a path from
which product can flow interrupted. In some cases the hydrates are mixed with asphaltyne and
paraphin within the same circuit.
Disassociating Hydrates
The methods below are employed to remove/remediate hydrates, and are split into six categories. Using
a singular approach is practical, but greater progress is achieved when multiple methods are utilized.
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Heat Application- This method requires an operator to circulate heated fluids to the area
affected by hydrate
Mechanical application- Coiled tubing can be employed to drill, or used to circulate heated
fluids to affected area
Condensate and Gas Separation- The separation method is highly effective, as it separates
fluids and gases which decreases the chances of forming hydrates in the equipment which is
being utilized to displace/remove hydrates from source
Utilization of pressure- Pressuring against a hydrate can allow an operator to attempt to
dislodge the hydrate, but can also cause greater solidification in the plugged area in the region
where the hydrate is formed
De-pressurization- By choosing this method the operator can bring the pressure below the
hydration formation curve which correlates with temperature
Chemical Injection- Clients can equally choose to inject thermodynamic inhibitors through
tubing or a chemical injection line, directly to the point of blockage. Such inhibitors include,
glycol, methanol, or low dose hydrate inhibitors, injections are also used to dose the equipment
which is removing the hydrate
Wright’s Well Control Services (WWCS)has hybridizeda majority of these methods, and has patented the
WWCS Hydrate Remediation System consisting of a pump/motor assembly in a 71’ long skid with a and
modular gas separator which sits atop the skid. The WWCS Hydrate Remediation System can robustly
inject chemicals, while pressurizing or depressurizing. Note: The heat and mechanical approaches
mentioned above are not used by WWCS, but are listed to provide the readerwith an in depth
understanding of the different hydrate remediation processes.
Identifying the Exact Location of Hydrates to Begin Remediation
Once a blockage is confirmed the operator will begin to form a plan of action utilizing the methods listed
in the above section. During the planning process the operator can opt to pump from a host platform
and perform testing to see if continuity can be achieved in a circuit. If this surface method is not fruitful
the hydrate will need immediate remediation via subsea intervention. For efficient and successful
intervention, the hydrate(s) must be properly located. However, as a Host Platform will only register the
most immediate point of blockage or where there is a sensor for monitoring pressure.
The utilization and advancements in non-intrusive technology in regards to nucleonic
measurement greatly aids in locating blockage. Such instrumentation is radioactive, and highly
robust. This particular instrument is attached to the ROV and is utilized to scan a pipeline. In
lengthy pipelines/circuits the scans conducted by this system are segmented and done in
sections. However, scans of the entire asset are most effective. All scans are logged via a
topside controller. The raw data received is then interpreted by electronics
equipment/hardware and software.
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ROV tools can also be deployed to measure and monitor pressures providing a secondary way of
pinpointing the area which is affected.
The following section will cover the different tools that are utilized to combat minor hydrates/blockages.
Hydrate Skids and Hydrate Tooling- The Past, Present and Future
This section will not only describe the current skids/tooling which are on the market that are used for
hydrates, but will also give a visual and written description of their capabilities, strengths and
drawbacks. This section will focus on tooling that mounts via the ROV’s porch.
ROV Porch with WWCS Tooling
Pumps
Operators typically utilizethe pumps currently available on the market for minor hydrates, whichare ROV
mountable via the porch or a skid. Pumps are ideal for applications, such as removing a hydrate from a
tree cap, or removing a blockage from different lines in flying leads - CFL, HFL, SFL’s. The drawback to
pumps is that they do not inject or pull suction at a specific rate, but instead fluctuate with each stroke
causing sudden pressure spikes. Also pumps rates are in gallons per minute (GPM), and due to the
fluctuation of the stroke, the pump will have an average of 2.5 GPM during operations. Pumps can
reach high pressures for chemical injections, but as pressure increases, GPM output is reduced. What
makes pumps robust is that they can pump gas, water, and condensate, and likewise pull a vacuum.
Pumpswill not be able to pull large quantities of these materials from a pipeline nor flush through it (If
the pipeline is measured in miles), due to its GPM capacity.
A second style of pump is commonly used to flood a pipeline with methanol to treat a hydrate. These
pumps are also ROV mountable via the porch or through a skid. Such pumps can pump at a specific rate,
however they are not designed to handle condensate, gas and water mixtures.
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As stated previously the ability to mount on to an ROV porch, directly or via attachment (non skid),
allows for quick deployment. These pumps are very limited in regards to output capacity, since the input
pressure and flow are dictated by an ROV, which is in the 20 GPM range, and function at medium
pressure (This figure will vary due to the different ROV system’s on the market). One must keep in mind,
that these pumps are tied in to the main hydraulic supply of a SUB, which will affect the ROV’s
maneuverability in regards to its thrusters, manipulators etc.
Electronic tooling/software utilized for hydrate remediation
Transducersare sensors which are used in subsea applications to monitor pressure input and
allow the operator to see fluctuations of pressure, which are highly indicative of hydrate
breakage and also gives great insight in how the internals of the pipeline are behaving
(reference locating hydrates section).
Flow Metersare used to monitor injection rates via an ROV mountable pump. Certain styles of
pump will register the output. This allows the user to monitor the input of chemicals to ensure
the storage bladder is not damaged while the inlet part of the pump tries to pull chemicals. Flow
meters are equally important when injecting chemicals/fluids, as this gives the end user a way to
monitor progress and the amount of product displaced from the pipeline.
Valve Packs are submersible remotecontrol systems that are hydro-electric and are composed
of software, and hardware. This allows a user to give commands while transmitting and
receiving data remotely. This data can then be collected, analyzed, interpreted and gathered.
The end result is a system which is self contained and controlled via a topside computer. A valve
pack can easily control the input flow and pressure which comes from the ROV to independently
control the mounted pumps, since tooling suites are aftermarket attachments and are not
developed with the ROV. The same logic can be applied to transducers if one looks at them as
aftermarket products, the data received by the transducers must be registered through the
valve pack.
Note: utilizing an ROV porch has its drawbacks as the space is very limited due to it being populated by
components for the ROV, which are attached to the porch. Equally if various ROV tools are being used,
the operator will not be able to deploy all tooling at once, but will have to remove and re-attach tooling
during operations, increasing down time.
ROV Attachable Skids
When these components referencedin the ROV Porch tooling section are consolidated and used in
unison, a hydrate skid is the finished product. Skids provide the ability to control and arrange multiple
pumps, flow meters, and transducers in one locale, which are monitored via a mascot. A hydrate skid is
an exoskeleton frame that mounts directly below an ROV. The key to mounting is a “sandwich plate”
that mates the skid to the ROV, by doing so the ROV can attack various points of interest to inspect and
remove hydrates.
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Pumps in ROV attachable skids offer a higher and consistent output over a stand-alonepump. However,
these skids do not have the ability to immediately pull a vacuum on a pipeline, andmust be first returned
to the surface for reconfiguration.Skids also cannot be deck deck-tested, leading to downtime as
analyzing the system for faults can only be done during operations.
Lastly, new technologies are constantly evolving in the ROV tooling industry. The skids discussed in this
section make up the majority of the ROV skid hydrate remediation market.
ROV Tooling and Integration
Tooling, whether it is electrical or hydraulic, has to be integrated with the ROV to be fully sustainable
and functional.
Hydraulic-To integrate a valve on a skid hydraulically, a hydraulic circuit must be composed of a
pressure and return line, which is plumbed into a valve pack. This configuration distributes the
hydraulic energy to the necessary components, via valves stored in the valve pack. The ROV
commonly has such valve assemblies, but if not, a skid can be populated with valve packs to
function as a manifold enabling the skid to perform multiple functions. If a single pump is used,
a pressure and return line will only have to be applied to that single item.
Electrical- To function or communicate at depths up to 10,000’ with tooling, there is a series of
conditions that must be met. First a multiplexer and a demultiplexer are set in place to turn
electrical data signals within copper into light which is then ran as a fiber optic signals. It is
imperative to send data this way for a variety of reasons:
o The umbilical on the ROV winchhas to be long enough to reach the ROV and travel
through the ROV’s tether. The tether is what allows the ROV to travel freely through an
X,Y and Z axis. Note: electrical signals travelling through copper cannot go as far as one
which is running fiber optically.
o To communicate with electronic tooling, which in this casewould be a valve pack, a
communication path must be established. Also a power source is required to energize
printed circuit boards and related components which make up electronic tooling.
o Lastly, connecting various electrical components has its limitations due to the electrical
power that is required - again this form of energy is also borrowed from the ROV itself.
Chemical Injections
Chemicals such as methanol have a dual function, the first is to be able to inject in to the affected area,
and the second is the obvious treatment of hydrate removal equipment. It is not practical to inject and
then dispel methanol.
The chemicals which have been injected are eventually pulled out of the affected source during
pumping when a vacuum is being applied. These chemicals will need to be stored, due to the fact that
when they are removed from the source the presence of hydrocarbons is highly likely, making it
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imperative to control and contain the incoming gas, condensate, or water. Chemicals upon being
removed can be captured subsea with a secondary or bladder, or they can be brought to surface with
the utilization of coiled tubing. The incoming material can be separated, or taken in as single product.
Separation is ideal as it removes gas from condensate, which takes the two volatiles mediums through
separate circuits which greatly decreases rehydrating of the equipment used inthe removal.
Chemical injections can be split into three categories, the first deals with the injection point, the second
is the location/source of the chemical (surface or subsea), and the third deals with chemical dosing.
Injection Point- a proper injection port must be located and/or configured, this ensures that the
hydrate will be properly targeted. Hydrate ROV panels are utilized to tie in to a PLET, FLET,
pipeline, etc. Other engineered interfaces are used, which is solely dependent on affected area.
Dosing- dosing is highly critical to keep the equipment which is removing the hydrate, from itself
becoming hydrated. Dosing can be accomplished at multiple points but depends on
configuration. It is typical to dose the parts of the equipment that see the incoming hydrate and
also to dose the line that will store the product which is coming out of the affected area. Dosing
has its limitations if the pipeline targeted for remediation is miles in length, which would require
immense amounts of methanol injection and removal.
Chemical Location- methanol can be stored in tanks on the back deck of a vessel. If this is not an
option then the methanol supply will have to come from a subsea source. There are two
different ways of supplyingfluid,one option would be to do so through a host platform that can
supply methanol via a UTA, or a subsea asset which can output methanol. The second option
would be to have a crane deploy a subsea bladder/reservoir to store methanol. While this
solves the source problem in regards to methanol, new issues arise as now there is a limited
fluid supply. Once the supply is depleted the bladder must be recovered and brought to surface
to be refilled and returned back to the ocean floor to provide methanol – often multiple times.
The Wright’s Well ControlServices Approach to Hydrate
Remediation
The Wright’s Hydrate Remediation System is different from the alternatives outlined above in that it
does not depend on limited hydraulic energy from the ROV. This skid is a completely independent
system, powered from the surface. The next sections will highlight and explain the different
components of this system which has achieved results far exceeding current hydrate remediation
solutions.
Hydrate Skid
Prior to the hydrate skid being over-boarded via a crane on a MSV (Multi Service Vessel), mud mats are
put in place on the ocean floor, these mats keep the skid above the mud line by providing extra stability
and support. The skid is then deployed from a MSV and upon reaching the splash zone is lowered to
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operational depth.
The skid itself is composed of a motor and pump assembly, which is powered from surface from a MSV
by filtered seawater via coiled tubing. The skidhas a redundant motor and pump, allowing operations to
continue should there be any difficulties with the initial setup used.
Hydrate Skid
Gas Separator
The gas separator is deployed in a modular fashion as an independent system that is designed to
interface on the top of the hydrate skid, and separates gas from the fluids via coiled tubing. The first coil
tubing line sends gas freeflowing to a surface gas separator and/orflare boom. The second coil tubing
return line receivesthe processed hydrocarbons and otherfluids to the surface for additional
processing and containment.
Additional features of the gas separator include a methanol injection panel to prevent the formation of
additional hydrates. Several injection points throughout the hydrate skid and separator are able to
receive methanol. Also a ball check in the stack prevents fluid from filling the gas line and the gas
separator has a built in sand trap.
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Gas Separator
Hydrate Remediation System Choke
At surface the choke developed by Wright’s methodically designates the separated condensate and gas
to the appropriate circuitry. At this point the gas and condensate returns are thoroughly measured, the
amount of each particular medium is closely analyzed as it is a direct manifestation of what is internally
trapped inside the affected source.
The choke also acts as a safety barrier that allows the personnel on the back deck, to shut in and keep
gas and condensate returns contained. Equally, the choke can isolate both items at liberty, if the gas
pressure needs to be analyzed then the choke is closed and the pressure is monitored at surface, while
allowing condensate returns to flow freely. The choke can also be adjusted to restrict the amount of gas
which will be returning on surface, while allowing the condensate to remain unrestricted, by doing this
the operator can further affect the hydrate remediation process.
Emergency Quick Disconnects
In the event of a MSV drive off and/or loss of power; the release of hydrocarbons; or salt water flooding
the pipeline asset and hydrates reforming, subsea accumulators engage Emergency Quick Disconnects
(EQD) from the vessel. There are three methods for send the signal to initiate deployment of the EQDs:
Acoustically- Allows a signal to be sent via ROVNAV on the ROV or from the bridge. The signal
travels in a sound wave from the vessel surface which then activates a solenoid that releases the
stored hydraulic energy
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ROV Manipulators - The gas separator is equipped with an ROV panel that includes an ROV
friendly valve that can be moved to allow the stored energy to actuate the contingency circuit
Wire Ropes -Provides a final line of defense to engage the emergency circuit via a steel wire
rope that is tightly connected to the coiled tubing on the separator. In the event of a drive off,
the coiled tubing will begin to experience tension. The wire ropedwill also absorb the tension
and will offset to move an ROV friendly valveactuating the accumulators, and separating the
vessel from the subsea equipment.
Once actuated the EQDs initiate the follow sequence:
Ongoing hydrate operations on the pipeline/subsea asset are shut off by isolating barriers
All four hot stabs eject at tie in points, thus overcoming differential pressure caused by a
vacuum effect in the pipeline vs. hydrostatic pressure
Subsea Integration
Pressure Monitoring
Multiple gages on the skid and separator have been strategically placed to measure and interpret the
behavior of the internals of a pipeline, this is very advantageous as it allows constant monitoring and for
adjustments to be made instantaneously by WWCS service personnel. Both the skid and separator have
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a total of three mounted analog gages. The separator has an extra dedicated receptacle which is used
to digitally monitor pressure via three transducers. These devices are all designed to monitor
combination of pressures, which is necessary due to the skid’s ability to pull a vacuum within a pipeline.
When this is accomplished the pipeline or the internal hydrate sources will have a pressure differential
due to the hydrostatic pressure. When this differential occurs, the internals of a pipeline will ultimately
fall below sub ambient, which requires monitoring in absolute pressure. The WWCS hydrate
remediation system can operate under these parameters.
Analog and Digital Advantage- By using both medias, the operator is equipped to keep a diligent view of
all segments of the equipment, likewise what a transducer provides is the utilization of data logging
equipment. Such data is relayed back to the ROV control room from where the data is not only
logged/monitored but also gives a real time and historical log that is charted. The charting of data is
what ultimately indicates what kind of process is being made for removing the hydrate. Pressure can be
monitored hydrostatically, while changes in differential pressure are analyzed and then compared to the
pipeline, which is the primary focus with ambient pressures to determine effectiveness of operations.
The Hybrid Valve Pack/ROV Tooling
The hybrid valve pack is a ROV tooling suite designed, built and tested by WWCS.The pack includes ROV
deployable bladders with a secondary pumping system to charge the accumulators subsea and to
actuate the different functions during operations. From the software, to the hardware and mechanical
components, this system is unique as it does not require a skid and can be mounted and prepared for
service immediately upon arriving on deck. The valve pack can monitor and record the pressures
referenced in the prior section, as well as monitor the GPM being injected.
Hybrid Valve Pack
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