Princess Subsea Gas Lift Start-Up

Transcription

1 40 th Gas-Lift Workshop Houston, Texas, USA Oct , 2017 Princess Subsea Gas Lift Start-Up Belle Ibanez, Shell Steven Freeman, Shell 2017 Gas-Lift Workshop 1

2 Agenda Princess Field Background Subsea Gas Lift Overview Princess P4 Gas Lift Design and Equipment Installed Well Unloading/Gas Lift Start-Up Results and Learnings 2017 Gas-Lift Workshop 3

3 Princess Field Background Subsea Tie-back to the Ursa TLP (3 miles North of TLP) 6 producers flow to 3 subsea flowlines Seawater injection through 2 subsea flowlines to 3 water injection wells 2017 Gas-Lift Workshop 4

4 Subsea Gas Lift Overview Background: Subsea gas lift was installed to support the Princess wells in November System was placed out of service in 2012 due to inactivity. System was then hydrotested and recommissioned in April 2017 to begin injection. Gas lift flowline from TLP Subsea Hardware includes: Gas lift flowline from TLP 4-slot Gas Distribution Manifold (GDM) with future expansion capability Subsea Gas Lift Flow Modules Gas lift jumper or Gas lift Steel Flying Leads (GSFL) Modified standard 15K trees to allow for gas injection- Annulus Gas Lift Valve (A) Gas lift Distribution Manifold (GDM) Gas lift Steel Flying Lead (GSFL) Modified Subsea Tree P Gas-Lift Workshop 5

5 Princess P4 Well completed in 2009 with 7 unloading valves and 1 orifice installed in the tubing A-annulus displaced from 8.4ppg KCl brine to gas lift down to first (7,094 MD) At the time of completion, P4 was the first subsea well in the world with multiple unloading valves Downhole Instability psi pressure swings Well Choked back to manage instability SCSSV GLO Prod. Packer Frac & Pack Completion 2017 Gas-Lift Workshop 6

6 P4 Gas Lift Start-Up Objective: Unload remaining 8.4ppg KCl brine from the A- annulus through the gas lift valves to the maximum injection depth Major Risk: liquid cutting check valves in gas lift mandrels compromising tubing integrity SCSSV Comprehensive study of gas lift valves and mandrels Unloading valves originally rated to dome charge pressures up to 2500psi. Valves were then de-rated to 2200psi (affecting valves 1 and 2). 2400psi is where elastic deformation occurs, so expected operating conditions were within acceptable envelope Start-Up plan consistent with API 11V5 guidelines to ensure the liquid rate does not exceed the recommended 1bpm GLO Prod. Packer Frac & Pack Completion 2017 Gas-Lift Workshop 7

7 P4 Gas Lift Start-Up Pre-Start Up Conditions A-annulus pressure reaches kick off A-annulus pressure and FBHP decline as gas lift is transferred to deeper valves Wellhead Pressure Downhole Pressure Production Choke A-annulus Pressure Gas Lift Injection Rate Unrelated gas lift shut FBHP reaches operating down limit with 1.7MMscfd gas lift injection rate 2017 Gas-Lift Workshop 8

8 Results Gas lift restored downhole pressure stability, allowing the well to ramp up to it s technical operating limit Double-digit percentage increase in oil rate as well as life extension and incremental recovery from the well Successful gas lift delivery to Princess P4 de-risks gas lift at other wells in the field: P6, P7, P Gas-Lift Workshop 9

9 Learnings Subsea Challenges: Uncertainties in effectiveness of flushing/drying subsea flowline after hydrotesting, presenting the risk of residual liquid entering the A-annulus Unexpected dp within subsea system particularly in Gas Lift Steel Flying Lead (GSFL shown below) immediately upstream of the tree Reduced the maximum injection pressure at the subsea tree Looking into new design options for future producers Learnings: A-annulus surface pressures required to kick off the well and transfer down the valves were generally higher than expected Valve de-rating impacts other producers in the field as well as future wells designs 2017 Gas-Lift Workshop 10

10 Q&A 2017 Gas-Lift Workshop 11

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