Challenge of Removing Sand from Subsea Separator

Monday, 05 November 2007

Figure 1 - Separator and Desander Vessels Shown in Orange

Merpro Limited announced today that their patented TORE® - Solids Hydro-Transportation Device has been incorporated into FMC’s Tordis Subsea processing Module.

FMC’s Tordis Subsea Processing Module (Figure 1) is one of the industry’s first fully functional, commercial subsea separation system of oil, water, and sand and has been completed for Statoil’s Tordis field.

Figure 2 - TORE® Solids Hydro-Transportation

FMC’s development team selected Merpro’s TORE® (Figure 2), because the subsea processing system required sand handling components proven to be robust, reliable and with a proven topsides track record. Also key to the TORE®s selection is its unique ability to remove sand while the separation vessel remains online, without affecting the liquid-liquid separation interface, adding turbulence to the vessel, or creating emulsions. FMC’s team qualified best available technologies, completed small scale testing, and then full-scale testing to fully demonstrate the capabilities and efficiency of the sand removal system.

TORE®s are installed down the bottom center of the Tordis separator (Figure 3). The TORE®s generate a vortex which fluidize solids within their surrounding area. When fluidized the solids are drawn to the TORE®s discharge tube allowing for controlled hydro-transportation out of the separator. The solids are transported to the desander vessel,

Figure 3 - Separator with Tore® Hydro-Transportation System

where the solids are separated from the TORE®s discharge sand slurry stream. The recovered sand accumulates in the bottom of the desander, and another TORE® installed in the desander is subsequently activated to discharge the sand. The sand is discharged from the desander into the water injection stream downstream of the water injection pump, so that the subsea pump are not exposed to the produced sand. The desanding operation is semi-automated with operators activating an automatic sequence once or twice per week depending on actual sand production rates. The sand is removed while the separator remains online with no interruption to production.

References:
Ann Christin Gjerdseth, FMC Technologies. Separate Oil from Water on the Seafloor with the Tordis IOR (increased oil recovery project) in the North Sea, the engineers’ dream of separating oil from water on the seafloor is becoming a reality.

Toine Hendriks and Rune Fantoft, August 16, 2004, Scandinavian Oil Gas Magazine Online, Design and Performance – Testing of a New Solution for Subsea Separation.