Well surveillance by continuous temperature profiling using DTS kit

by

Wim der Kinderen

Consultant Production Technologist

Shell UK Exploration and Production

Aberdeen

w.derkinderen@expro.shell.co.uk

API/ASME Gas Lift Workshop, Houston, February 2001

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

The physics behind DTSDistributed 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)

Water Pump

Casing

Optic fibre deployment 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

Real Time Data Management

System (RTMS)

Fibre reelSensa® Signal Conditioner

Packer

Adaptor Flange

Xmas Tree

DTS specs:

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

ahd (m)

T (C)

t 1 = 14:16 h - kick-off started

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

0

20

40

60

80

100

120

12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00

CH

P (

ba

rg)

FL

TE

MP

(C

)t1 t2 t3 t4 t5 t6

Annulus pressure and wellhead temperature trends during unloading

t 2 = 17:16 h - top ULV opent 3 = 18:01 h - 2nd ULV and orifice pass gast 4 = 18:46 h - ULVs closed, inflow startedt 5 = 21:46 h - ULVs re-open at higher gas ratet 6 = 23:01 h - ULVs closed, tubing warming upt 6 = 23:01 h - estimated tubing temperatureahd (m)

T (C)

• 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

What’s planned next?

Subsea Deployment

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 Connectorfor Tree/TH

Optical Wet Connect

OK 2001