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Well surveillance by continuous temperature profiling using DTS kit

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).

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Well surveillance by continuous temperature profiling using DTS kit

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  1. 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

  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. Xmas Tree Sensa® Signal Conditioner Adaptor Flange Water Pump Fibre reel Packer Casing 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 t1 t2 t3 t4 t5 t6

  9. T (C) ahd (m) t 3 = 18:01 h - 2nd ULV and orifice pass gas t 4 = 18:46 h - ULVs closed, inflow started t 6 = 23:01 h - ULVs closed, tubing warming up t 6 = 23:01 h - estimated tubing temperature t 5 = 21:46 h - ULVs re-open at higher gas rate 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. Data Comms. DTS POD DTS Processor Subsea Distribution Pod Jumper SDU Wet-Mate Connector for Tree/TH Subsea DTS pod Wellhead & Tubing Hanger Main Umbilical SCM Well Jumper UTDA Optical Wet-Mate Connector Upper Completion Optical Wet Connect Lower Completion Subsea Deployment OK 2001

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