1. Well surveillance by continuous temperature profiling using DTS kit
Wim der Kinderen
Consultant Production Technologist
Shell UK Exploration and Production
Aberdeen
API/ASME Gas Lift Workshop, Houston, February 2001

2. Distributed Temperature System (DTS)
How does it work?
Sensor is ‘standard’ optical fibre
Fibre is pumped into well through control line post completion
or ‘hardwired’ using fibre optic braided cable
Measures temperature along the length of fibre (1 m resolution)
History
>100 Oil well industry installations (e.g. Aera-steam flood)
BPA Wytch Farm successes KA-7, M12, M17
Value Drivers
Gas lift optimisation, tubing integrity, reservoir inflow data
Reliability of system potentially higher than standard PDGs

3. The physics behind DTS
Distributed temperature is measured by sending a pulse of laser light down the optical fibre. Molecular vibration, which is directly related to temperature, creates weak reflected signals. The reflected signal is detected in the surface read-out unit and converted to values of temperature at 1 metre intervals along the fibre and well.
Multi-mode fibre is 50µm diameter with a 125µm doped silicon cladding, within a wear resistant acrylate coating.
Time =ƒ(depth)
Anti-Stokes vs. Stokes amplitude = ƒ(temp)

4. Optic fibre deployment
Xmas Tree
Fibre reel
Packer
Sensa® Signal Conditioner
Adaptor Flange
Casing
Water Pump
Real Time Data Management System (RTMS)
Optic fibre deployment
DTS specs:
Accuracy & resolution up to 0.1°C
Datapoint every metre
Up to 10,000 datapoints
Operates -40°C to + 300°C
Up to 10 wells per surface unit

5. TA27 DTS installation, April 2000
- platform well
- initial GL producer, later water injector
- encapsulated dual 1/4”sensor tube
clamped to tubing, down to packer
- datasets (T versus depth) collected
every 20 minutes and sent to shore
- latest 10 datasets accessible on the web
- temperatures at 10 selected depths
recorded in PI data historian

6. T (C)
ahd (m)
t 1 = 14:16 h - kick-off started

7. Observations: Bunch of wells coming together beneath the platform:
earth heated up by producing wells
Lift gas:
100+ °C at wellhead
cooled by seawater
Sensor tubes are plastic encapsulated:
insulated from the tubing
effectively Tannulus is measured
Above lift point:
Ttubing > Tannulus > Tformation
Below lift point:
Ttubing  Tannulus

8. Annulus pressure and wellhead temperature trends during unloading

9. T (C)
ahd (m)
t 6 = 23:01 h - ULVs closed, tubing warming up
t 5 = 21:46 h - ULVs re-open at higher gas rate
t 3 = 18:01 h - 2nd ULV and orifice pass gas
t 6 = 23:01 h - estimated tubing temperature
t 4 = 18:46 h - ULVs closed, inflow started
t 2 = 17:16 h - top ULV open

10. What’s planned next?
Combine gas lift surveillance and reservoir inflow monitoring
DTS across reservoir sections inside/outside casing
Develop real-time thermal profiling analyses tools
Develop sub-sea Xmas tree wet mateable connector (on-going)
Develop downhole liner top wet mateable connector
Develop long distance DTS capability via umbilicals

11. Subsea Deployment OK 2001 Subsea Distribution SDU Wellhead & SCM
Optical Wet-Mate Connector
SDU
Subsea DTS pod
Main Umbilical
SCM
Well Jumper
Upper Completion
Lower Completion
Subsea Distribution
Wellhead &
Tubing
Hanger
Pod Jumper
UTDA
Data Comms.
DTS POD
DTS Processor
Wet-Mate Connector
for Tree/TH
OK 2001
Optical Wet Connect