Merpro® Tore® Online Vessel Desander (OVD)Technology Document

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© 2011 National Oilwell VarcoD352002039-GEN-001 Rev. 02

INTRODUCTIONProduced sand accumulating within process trains is one of the major factors that disrupts and limits oil and gas production. Sand screens are installed in the reservoir to eliminate or reduce the amount of sand flowing in the well stream. They are expensive to install and maintain, and have varying levels of success. Early methods used to remove sand from the separation train were jetting and sparging systems. These had limited success when small amounts of sand were produced. Desanders were then introduced and installed to remove sand from the wellstream before it entered the separation train. This method is limited by size of the desander and efficiency of the liquid/solid cyclones. Desanders are prone to blockage and can have a high maintenance requirement.

SAND REMOVAL SOLUTION USING TORE

The application described here involves installing Tores internally within separators and is termed Tore Online Vessel Desander (Tore OVD). This provides guaranteed and effective sand removal whenever required by the operator. It has gained rapid acceptance by the industry as the preferred solution for sand removal, and is replacing traditional methods. It is not a jetting system, but utilizes the unique, localized and controlled, tornado like action of the Tore device to lift and remove the sand.

WHAT IS TORE?

Tore is a solids hydro-transportation device which utilizes natural forces to lift and move solids in a controlled manner. It is a core technology in the process solutions range.

WHAT DOES TORE ONLINE VESSEL DESANDER (OVD) DO?

Tore OVD removes sand from separators. Tore is equally effective in removing fine chalk or clay particles.

HOW IS IT APPLIED IN THE SEPARATION TRAIN?

Within small vessels, a single Tore OVD comprising 4 Tore devices arranged in a linear fashion, usually centrally along the floor of the vessel is sufficient to remove the sand. In larger vessels, Tore OVD is installed comprising 8, 12 or

more Tores, usually in multiples of 4, to provide the required coverage. Vessels more than 3m wide usually require the Tore devices to be in a double bank. For effective removal of sand, the Tore units are installed with approximately 0.8m – 1.2m distance between each Tore. This provides maximum coverage of a vessel floor without overlapping the effect from neighbouring Tore devices.

HOW DOES TORE ONLINE VESSEL DESANDER (OVD) WORK?

The Tore is a highly effective solids fluidization device that can operate even when completely buried in sand. It operates by generating a vortex below the Tore which fluidizes the sand in this area. The vortex is created by introducing fluid through the Tore feed inlet tangentially into the swirl chamber. This establishes a swirling motion which passes through the annulus between the Tore discharge tube and outer tube and over the foot of the Tore. When fluidized, the sand is drawn by the central core of the vortex towards the discharge tube, allowing for controlled transportation. The fluidizing effect created by the Tore is localized with no disruptive effect on a vessel’s liquid interfaces.

Accumulated sand in production separator.

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Merpro Tore Online Vessel Desander (OVD)Technology Document

Schematic of internal Tore OVD arrangement in production separator

© 2011 National Oilwell VarcoD352002039-GEN-001 Rev. 02

OPERATING TORE ONLINE VESSEL DESANDER (OVD)

In order to provide operational flexibility, Tore OVD may be operated individually, all at once, or in any desired combination. Each 1” Tore within a manifold requires approximately 3-4 m3/hr of motive fluid at only 0.5 bar above vessel pressure to operate. In comparison, a jetting system typically requires around 120m3/hour. Motive fluid can be supplied from a plant’s existing produced water system or from any other suitable fluid source. The flowrate can be set manually or automated using flow control valves depending on the application. The sand discharging from the Tores can be routed either to sand washing equipment, such as a Tore Scrub, or to collection equipment such as a bagging system prior to disposal. A small amount of residual sand (typically less than 2% by volume) will remain in the vessel, outside the area of influence of each Tore. The amount of residual sand is dependent on the positioning of each Tore, and the angle of repose of the sand. The residual sand is constantly changed between Tore activation cycles, as the well fluids wash over and redistribute them into the area of influence of the Tores. One operator activates their Tores for half an hour every morning and half an hour every evening, and removes up to 10 tons of sand per week from their separator. Previous practice was to shut down every 3 months for 4 days at a time to dig out sand. In 24 months, Tore OVD has eliminated 32 days of production shut downs. The NOV Merpro In-line Pressure Reducing Cartridge can be installed on the outlet from the separator if pressure requires to be reduced for discharge and collection.

NEW BUILD OR RETROFITTore OVD can be installed in new build or existing separators and is designed in the optimum configuration for maximum sand removal. In retrofit installations, it lends itself to being mounted around existing internal structures such as baffles and weirs. Tore OVD is straightforward to install as a retrofit solution, typically taking 2 days after accumulated sand has been dug out from the separator. Approximately 50% of installations are retrofit applications. Where vessel design prevents internal installation, Tore OVD can be designed for external mounting.

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© 2011 National Oilwell VarcoD352002039-GEN-001 Rev. 02

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Merpro Tore Online Vessel Desander (OVD) Technology Document

FEATURES AND BENEFITS:

• Eliminates unplanned shutdowns. It provides a proven, guaranteed solution, whereby sand is removed from vessels while the separator remains in

full production. There is no need to shut down separators or otherwise interrupt production throughput. One operator saved 32 days production time

over a 2 year period by installing Tore OVD

• Enables separators to operate continuously at maximum efficiency, enabling well fluid production to be maintained at maximum levels. Another

operator reports that they have been able to increase well fluid throughput by 30% since they installed Tore OVD in their production separator, giving

a direct increase in revenues

• Provides a life of field solution to sand production, and handles all levels of sand. One 1” Tore device can remove up to 4 tons of sand per hour, and

can be activated whenever required

• Fluidization effect of the Tore is localized, causes no disruption of the liquid surface/interface and can therefore operate while the vessel is online

• Required feed pressure to the Tore OVD is approximately 0.5 Barg above the vessel operating pressure and each Tore requires only 3-4 m3/hr of feed

water, substantially less than jetting systems

• Easy to retrofit

• Eliminates the need for dedicated desanders, saving space and weight

Tore Online Vessel Desander (OVD) – The combination of a number of Tores with interconnecting pipework to ensure large area sand removal.

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