StatoilHydro Tordis

Landmark: The World’s First Full-Scale Commercial Subsea Separation,
Boosting and Injection System

Block: Tampen Block 34/7

Project Overview
Contract Award: 2005
Sales: Kongsberg, Norway
Fab. Trees: Dunfermline, U.K.
Fab. Controls: Kongsberg, Norway
Service Base: Bergen, Norway
Host Type: Integrated Foundation
Contract Type: EPC

Project Characteristics
No. Trees: 1
Water Depth: 200 m (656 ft)
Tree Type: Water Injection XT
Separator Design Pressure 200 bar (2900 psi)
Tree Pressure: 5,000 psi
Tree Bore Size: 11”
Hydrocarbon: Water Disposal

Project Ownership
Petoro 30%
StatoilHydro 41.5%
Esso 10.5%
Idemitsu 9.6%
Total 5.6%
RWE-DEA 2.8%

Scope of Work
•One (1) pipeline inline manifold (PLIM) interconnecting the existing flowlines from the Tordis field to Gullfaks C platform
•One (1) new design large capacity water injection subsea tree
•One (1) Subsea separation, de-sanding and wear resistant
•Subsea boosting system for multi-phase flow and water injection, including instrumentation for performance
•Monitoring and process control
•Approximately 12 km (7 miles) control umbilical
•Approximately 12 km (7 miles) power umbilical
•Topside HPU’s for pumps and control system
•Topside VSD’s for power to pumps subsea
•Topside process control system
•System integration, testing, installation assistance, service and maintenance

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System Description:

Pipeline Inline Manifold (PLIM)

The PLIM will be installed summer 2006 to interconnect the flowlines from the Tordis Subsea Manifold to the Gullfaks C platform allowing re-routing of the Tordis Well Stream to Gullfaks C via the Subsea Separation Station.

The PLIM allows full bypass of the Tordis Subsea Separation, and will be installed during a planned maintenance shut-down of the Gullfaks C Platform

Water Injection Tree

The Water Injection Tree is a simple Xmas Tree consisting of a 12” ball valve. A conventional internal tree cap is installed in the vertical entry section of the tree allowing for workover of the well. The reinjected water is pumped through this Xmas Tree through a 13 5/8 casing direct into the Utsira water reservoir. This is a non hydrocarbon reservoir with ambient pressure.

Subsea Separation Boosting and Injection (SSBI) Station

The Subsea Separation Station separates the water from the well stream which is reinjected through the large bore Water Injection Tree. After separation, gas and oil is mixed and pumped via a multiphase pump back to the Gullfaks C platform. The SSBI Station is installed in October 2007.

The Separation Station contains the following main elements:

Foundation Structure and Manifold
The Tordis SSBI Station has an independent conventional, overtrawlable foundation structure supporting the manifold, the separation module and all other components. The structure has four suction anchors, one in each corner for foundation and leveling.

The manifold module provides connection to the flowlines via Rovcon connection system and interconnects the various modules. The estimated installed weight of the Subsea Separation Station with manifolds and separation modules is approx. 900 tons.

Separation Module
The well fluid from the Tordis field is first routed into the separation tank. The inlet cyclone separator in the tank does a first separation where the majority of the gas is separated out and routed through a separate pipe outside of the tank, thereby minimizing the size of the separation tank. The remaining water, oil and gas are separated through the gravity principle inside the tank. The water is the heaviest part which is pumped via a water injection pump directly back into the Utsira reservoir through the Xmas Tree. Oil and gas are remixed and pumped through a multiphase pump back to the Gullfaks C platform. Any deposit of sand inside the separation tank is handled by the sand removal system.

The Separation Module is retrievable as a separate unit.

Sand Removal System
Any sand from the well stream will deposit at the bottom of the separation tank. A flushing system with specially designed nozzles has been developed to flush out the sand at certain intervals. The sand is transported into the Desander Module where it can be remixed with the injection water and reinjected into the reservoir downstream of the water injection pump. Alternatively the sand can be remixed with the oil and gas flow and pumped back to the Gullfaks C platform.

Water Injection Pump
The Water Injection Pump is a standard Framo pump system which is driven by an electrical motor powered through an electrical power cable from the Gullfaks C platform. The pump can be retrieved for maintenance by a separate pump running tool.

Multiphase Pump
The Multiphase Pump is a standard Framo pump, similar to the Water Injection Pump, and is powered through an electrical power cable from the Gullfaks C platform.

It can also be retrieved by a separate pump running tool.

Other
The Subsea Separation Station is equipped with two multiphase flow meters (Roxar) which will measure the composition of the well flow to prepare the separation system settings. A level monitoring system is installed in the separation tank to monitor water, oil and gas interfaces which again provide input to the water pump speed and the multiphase pump speed. The Subsea Separation Station includes one subsea control module with 51 functions to control the various functions of the station and communicate back to the Gullfaks C platform.

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Main Suppliers:

CDS Engineering:	Separation system design, Internals of the separation tank
Framo Engineering:	Water Injection Pump, Multiphase Pump, Topside Electrical Power system
ScanRope Subsea Cable:	Subsea Electro-hydraulic Umbilical
NN:	Power Cable
Roxar:	Multiphase Flowmeters
Leffer:	Separation Tank
Grenland Offshore:	Fabrication of Foundation Structure and Manifold

Comments
FMC has delivered a full scale separation facility to enable re-injection of bulk water into a non-hydrocarbon reservoir and send hydrocarbons through a multi-phase pump back to Gullfaks C.
The system including boosting pumps has been designed to handle high amounts of sand (50 - 500 kg pr day) with its sand management system.
Along with other upgrades to the field infrastructure, the recovery factor for the Tordis field is expected to increase from 49% to 55% (approximately 35 million barrels).

The PLIM was installed during the field shutdown summer 2006. The water injection tree was installed early 2007 and the subsea separation, boosting and injection system summer 2007.
Tordis Subsea separation Boosting and injection station is now on stream.