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What We Do Project Data Total Otter Field Development
Project : Nuggets Field Development
Client: |
TOTAL EXPLORATION & PRODUCTION UK plc |
Operator/End User: |
TOTAL EXPLORATION & PRODUCTION UK plc |
Date: |
1999 - 2000 |
Project Description : |
Subsea development of oil field |
Location : |
Central North Sea |
Services Provided : |
Options studies and front end engineering |
Detailed Description :
Background
The Otter field is a marginal oil accumulation located in UKCS block 210/15a in the northern North Sea. The water depth is 182m. Total (field operator) and co-venturers Agip, Esso and Shell developed Otter as a subsea tie-back to a neighbouring platform (Eider). ode was responsible for option development and screening followed by front end engineering (FEED) of the selected scheme.
Otter field description:
Otter lies approximately 21 km south-west of the Magnus field and 27km north of the Tern field. The reservoir is located within the Brent Group reservoir sequence, with the majority of the oil being held in two members of this sequence, at a depth of approximately 6600 ft.
The oil is a light crude (36.50 API) with a low GOR (448 scf/bbl). It is undersaturated with a saturation pressure around 900 psi below initial reservoir pressure 2980 psi. There is no evidence of H2S and only 0.22% of CO2.
The reservoir can initially be produced under natural drive but artificial lift will be required after approximately one year. This will be provided by subsea downhole ESP’s.
Water injection for pressure support will be necessary very early in field life and the capability for total fluid replacement will be provided from the start of production. For this purpose the produced water may be re-injected into the reservoir, supplemented by water from another source, after treatment.
Services provided
- Process and hydraulic studies/simulation (HYSIM/PIPESIM)
- Design of subsea well systems, subsea manifold/cluster, all flowlines and control systems
- Pipeline, ESP cable and umbilical design and installation philosophy
- Review of host platform topsides modifications
- Evaluation of conventional and coiled tubing subsea deployed ESP’s versus gaslift.
- Design of topsides VSD modules and power distribution for subsea downhole ESP’s
- Simulation of downhole variable speed ESP performance
- Transient thermal analysis of start-up and shutdown operations and chemical requirements
- Definition of Operations/Topsides/IMR/Workover interfaces
- HUC and start-up and workover provisions
- Cost estimates, economics and analyses
- Generation and review of gas export and gas to liquids options for an FPSO
- Design and economic evaluation of a remote production buoy option
- Examination of economics of a subsea pig launcher and lined water injection pipe
Development Scenarios
Three main field development options were considered (option ‘A’ selected):
| Option A | Subsea production centre with 21km tie-back to Shell ‘Eider’ |
| Option B | FPSO 2km east away from subsea production centre |
| Option D | Subsea production centre with 28km tie-back to BP ‘Magnus’ |
| Option E | Subsea production centre with 27km tie-back to Shell ‘Tern’ |
Production Issues
The selected facility option utilises a number of unique production techniques.
- Horizontal wells with high integrity completion to minimise sand production
- Subsea facility design to optimise installation schedule
- Use of dual subsea deployed downhole ESP’s to allow flexible production from potentially fragmented reservoir.
- Mini-separator slug suppression devices to maximise uptime (following extensive multiphase simulation)
- KHI for hydrate inhibition
- Installation of topsides modification only utilising platform crane
In order to produce an economically viable project for the Otter field conventional technology was extensively examined, challenged and adapted to allow this marginal field to meet current development screening criteria.
