Is it necessary to install a downhole safety valve in a subsea ... - NTNU

APPENDIX A
A1 Subsea production system
This appendix is based on information found in references [5, 6, 12, 21]. The appendix is
included to provide a basis of understanding of a subsea production system and the different
hardware components included.
A production system is essentially a system that provides transportation of fluids from the
reservoir to the surface and separates it into oil, gas and water. The oil and gas streams are
transported from the field and prepared for sale. The water is treated and injected to the
reservoir or brought to disposal. A production system consists of different groups of
mechanical elements.
Subsea system components are normally exposed directly to the sea. The installation and
maintenance operations are carried out by specially designed manipulators, remote operated
vehicles (ROV), conventional divers, drill string from a vessel, or by recovering components
to the surface.
A1.1 Natural flow production well
Production from a natural flow well is probably the most common method of oil production.
Figure A-1 shows a naturally flowing production well. To be able to produce fluid from this
well different components are required. The main components relevant for a natural flow
subsea well are:
1. Casings
2. Tubing string
3. Production packer
4. Downhole Safety Valve (DHSV)
5. Subsea wellhead
6. Subsea x-mas tree
7. Control system
A-1