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Characterising Gas-lift Instabilities with OLGA2000 ASME/API/ISO Fall 2003 Gas-Lift Workshop

Characterising Gas-lift Instabilities with OLGA2000 ASME/API/ISO Fall 2003 Gas-Lift Workshop 21-22 October 2003, Kuala Lumpur. Bin Hu Ph.D Candidate Department of Petroleum Engineering and Applied Geophysics Norwegian University of Science and Technology E-mail: hubin@ipt.ntnu.no

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Characterising Gas-lift Instabilities with OLGA2000 ASME/API/ISO Fall 2003 Gas-Lift Workshop

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  1. Characterising Gas-lift Instabilities with OLGA2000 ASME/API/ISO Fall 2003 Gas-Lift Workshop 21-22 October 2003, Kuala Lumpur Bin Hu Ph.D Candidate Department of Petroleum Engineering and Applied Geophysics Norwegian University of Science and Technology E-mail: hubin@ipt.ntnu.no Telephone: +47 7359 4975 Fax: +47 7394 4472

  2. If gas injection isnot critical... • Casing heading may happen • To thoroughly eliminate casing heading, make the gas injection critical

  3. Is the well unconditionally stable if gas injection is critical? Replace the orifice with a venturi

  4. Vertical air/water two-phase flow No slug tracking Iso-thermal Initiated from steady-state Boundary conditions Static IPR Psep is constant Constant gas source is given near the bottom of the well OLGA2000 simulation settings

  5. Density wave instability can occur!

  6. OLGA simulation results PR is 90bara and air injection rate is about 18000Sm3/D

  7. OLGA simulation results PR is 90bara and air injection rate is about 40000Sm3/D

  8. OLGA simulation results PR is 90bara and air injection rate is about 54000Sm3/D

  9. Increasing reservoir pressure and gas injection rate increases stability. Increasing well depth, tubing diameter, PI and system pressure decreases stability Instability occurs only when Summary

  10. Production loss due to density wave instability

  11. Apply feedback control to the well Variation of choke opening after controller is started

  12. Variation of Pwf and wellhead production rate

  13. Manual control at the same choke opening

  14. Density wave instability can occur in deep depleted gas-lift wells. The instability not only causes operating problem, but also reduces production. Active feedback control is an effective method for both stabilising and avoiding production loss. OLGA is at least capable of qualitatively capturing the instability dynamics. Conclusions

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