Deepwater Offshore Technology Paper

New Developments for Ultra Deepwater Hydrate Remediation Technology in the

Gulf of Mexico

Authored By: Fernando C. Hernandez

Introduction

Hydrate Remediation WWCS

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 hybridized a 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 reader with 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

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topside controller. The raw data received is then interpreted by electronics equipment/hardware and software.

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 utilize the pumps currently available on the market for minor hydrates, which are 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. Pumps will 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.

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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.

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

Transducers are 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 Meters are 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 remote control 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 referenced in 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

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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.

Pumps in ROV attachable skids offer a higher and consistent output over a stand-alone pump. However, these skids do not have the ability to immediately pull a vacuum on a pipeline, and must 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 winch has 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 case would 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

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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 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 in the 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 supplying fluid, 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 Control Services 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

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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 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 skid has 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 free flowing to a surface gas separator and/or flare boom. The second coil tubing return line receives the processed hydrocarbons and other fluids 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

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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.

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

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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

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 roped will also absorb the tension and will offset to move an ROV friendly valve actuating 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

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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 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

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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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