Goliat Produced Water Management

Transcription

1 Goliat Produced Water Management Hans Tore Nordbø, Process Engineer, Eni Norge AS Tekna Produced Water Management, , Clarion Hotel Stavanger

2 PL229 Goliat location, ownership and current status Licence awarded in 1997 Present owners Eni Norge AS (op) 65% Statoil Petroleum AS 35% Milestones Installation work at the field Drilling from 2011 Production start-up Q Current status and schedule Subsea Production System: CA Q Flowlines and Risers: CA Q FPSO: Contract to be awarded Q1 2010

3 Reservoir characteristics for Goliat Shallow Reservoir meter below sea level Reservoir temperature: C Reservoir pressure: bara Crude oil API gravity (@ 15 C) Realgrunnen: Kobbe: Realgrunnen formation ~1150 m 120 bar 32 o C Kobbe formation ~1830 m 180 bar 48 o C

4 Subsea System Flowlines Production Loop: Gas Injection: Gas Lift: Sea Water Injection: Produced Water Injection: 12 ID 10 ID 6 ID 10 ID 10 ID Reservoir Type of well No. of wells Prod. 7 Kobbe WI 5 GI 2 22 wells in 8 of 4-slot templates meter water depth Realgrunnen Main/Central Realgrunnen South Prod. 3 WI 3 Prod. 1 WI 1 Total wells (All types) 22

5 Goliat FPSO Topside Design Basis Main Topside Systems Process Capacities: Gas processing: 3.9 million Sm 3 /day Oil production: Sm 3 /day ( bbl/d) Produced Water: Sm 3 /day ( bbl/d) Water injection (incl. produced water): Sm 3 /day ( bbl/d) Product Specifications: Gas Export/Injection/Lift: Outlet pressure: P = 225 bara Outlet temperature: T = 50º C H 2 S content: < 10 ppm Oil Export TVP: < bara at 35 C Water in Oil: 0.3 vol % BS&W max. Max temperature: 50 C Max salt content: 150 ppm

6 Regulatory requirements for the Barents Sea Zero discharge policy No PW discharge during normal operation. Maximum 5 vol% of the PW can be discharged during operation interruptions, provided the PW is cleaned according to Best Available Techniques (BAT) before discharge. No discharge of red and black chemicals Barents Sea

7 Eni Norge environmental requirements for the Goliat field Requirements included in technical and functional requirements, contractual requirements and design basis No discharges to sea during normal operations >95 % regularity of produced water (PW) injection, and application of Best Available Techniques (BAT) for treatment of discharged PW. Re-injection of drainage-water generated on unit as for PW Minimize chemical consumption Minimize the emissions to air Electrification from shore Closed flare units Energy efficient processes and systems BAT evaluation and documentation for all systems that may affect the environmental performance of the facility

8 Design basis for Goliat produced water and water injection system Produced water shall be re-injected into the reservoir to minimise discharges according to regulatory requirements and contribute to increased recovery. Minimum 95% of the produced water shall be re-injected Produced water treatment system consists of 3 treatment stages; Hydrocyclones (HC), compact gas flotation units (CFU) and a produced water flash tank. PW treatment system shall operate in parallel with water injection system. Chosen design is based on BAT evaluations. The WI system shall be designed with the possibility to dedicate pumps to either produced water re-injection or seawater injection to avoid mixing of the water streams. Dedicated riser, pipeline and wells for injection of PW and SW. Slop tanks installed for temporarily storage of produced water during WI shut down (~9000 m 3 ). One clean and one dirty slop tank, where the dirty also receives reject streams from the process.

9 Design basis for Goliat produced water and water injection system cont. Online OiW analysis instruments shall be installed for process control downstream hydrocyclones and downstream produced water degassing vessel. Sand jetting installed in separators and degasser. Sand washing system installed to clean the removed sand before it is shipped to shore The drain water from exposed areas shall, during normal operation, be routed to the slop tank from where it further shall be routed to the water injection system Analysis shows that discharge requirements will be met with good margin due to flexibility in pump system, slop tanks for temporarily storage of produced water, separated flowlines for produced water re-injection (PWRI) and seawater injection (SWI) and several injection wells for both PWRI and SWI

10 PFD - Goliat Produced water treatment and injection system

11 Hydrocylones system ~1.8 bara ~10 bara ~2 bara Common spare HC for inlet and test separator Screw pumps chosen to prevent oil droplet break up Online OIW monitoring for process control 2x100% sparing for LP and coalescer HC PW from LP and coalescer is boosted to appropriate pressure to be commingled with PW from inlet separator d/s HC

12 Hydrocylones system 3D model view Inlet and Test HC LP and Coalescer HC

13 Compact flotation units and produced water flash tank Recirculation of the released gas from the water Two CFU s operates in series Possibility to inject additional fuel gas and/or flocculating chemicals Possibility to inject fuel gas upstream of produced water flash tank The produced water tank will also function as a buffer tank for the injection system Online OIW monitoring for process control

14 CFU s and produced water flash tank 3D model view Produced Water Degasser Compact flotation units

15 Water injection system VSD control of booster and injection pumps Separate injec. flowlines and wells for SWI and PWI (inj. pressure bara) 2x100% automatic backwashing filter (50μm) Injection of scale inhibitor

16 Water injection system 3D model view Water Injection Pumps

17 Scale potential and prevention strategy Potential Low possibility of carbonate scale Sulphate scale forms from mixing of seawater and formation water Sulphate scale (Ba and Sr) anticipated in formation and screen Prediction Prediction of seawater breakthrough by tracer option in Eclipse Gas export -> Increased water rates -> Increased scaling risk in Kobbe wells Mitigation Separate water injection systems for seawater and formation water Inject produced water in Realgrunnen and seawater in Kobbe Continuous scale inhibitor injection at each OP HXMT Use of Multi-Phase meters on all production wells to measure water salinity for detection of water break-through Remedial Planned scale squeeze inhibition twice a year per well after seawater breakthrough Scale squeeze shall be performed from FPSO

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21 Thank you!