Well surveillance by continuous temperature profiling using DTS kit 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 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)

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

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

T (C) ahd (m) 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

Annulus pressure and wellhead temperature trends during unloading

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

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

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