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Gas Lift Design Philosophy for Chevron’s Subsea Developments

Gas Lift Design Philosophy for Chevron’s Subsea Developments. Shauna Noonan, Completions Engineering Team Chevron Petroleum Technology Company Houston, Texas. The Challenge. “Size the downhole orifice as big as possible and we can just control the gas injection rates from the FPSO”

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Gas Lift Design Philosophy for Chevron’s Subsea Developments

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  1. Gas Lift Design Philosophy for Chevron’s Subsea Developments Shauna Noonan, Completions Engineering Team Chevron Petroleum Technology Company Houston, Texas

  2. The Challenge... “Size the downhole orifice as big as possible and we can just control the gas injection rates from the FPSO” - general comments heard from various Chevron engineers • THE DOWNHOLE CHOKE (aka orifice) CONTROLS THE RATE OF GAS INJECTION INTO THE TUBING, NOT THE SURFACE CHOKE!!!!!!!!

  3. The Challenge.. “If this stability issue exists, then how come I don’t see this with my platform wells?” - general comments from various Chevron engineers Answer: Turns out they are not continuously injecting through the orifice. As these platform wells are completed with a conventional design (unloading valves), the well instability is dampened due to multipointing.

  4. Predicting Stability Margins with Transient Programs OLGA is the primarily tool used within the industry for transient analysis, however it does not look at transient behavior between the surface and downhole injection chokes. DynaLift addresses the gas lift transient issue, but does a poor job of the flowline assessment. Hence, Chevron has to use both programs…. Flowline/ Riser stability OLGA Gas Lift stability DynaLift

  5. OFFSHORE ANGOLA: Kuito and Benguela-Belize-Tomboco

  6. Kuito 1A

  7. unstable

  8. U-tube effect

  9. THE CHALLENGE ….. “In order to prevent erosion to the orifice, let’s run two of them. Have the upper orifice the “operating point” and then run a REALLY large unloading orifice below it!” - comments made by the reservoir engineering staff working on the project

  10. LOWER “UNLOADING” ORIFICE UPPER “OPERATING” ORIFICE WHY THIS IDEA WILL NOT WORK ….

  11. Kuito Update • Field start-up Jan 2000 • Gas Lift injection began May 2000 • Serious Problems with Flowline Stability • Engineering currently working on next 11 producers ….. Completed field testing to calibrate Olga model and the engineers using Olga and Dynalift are working as one “unit”.

  12. BENGUELA-BELIZE-TOMBOCO PROPOSED DEVELOPMENT - ONLY SUBSEA WELLS EXPECTED ARE 2 WATER SOURCE WELLS EACH SUPPLYING 40,000 BWPD

  13. BBT team wanted to lift 40,000 bwpd using gas lift

  14. EAST COAST CANADA: HEBRON

  15. HEBRON ARTIFICIAL LIFT STUDY • DETERMINE METHOD OF LIFT (ESPs or GAS LIFT) • 1870 m TVD, 21 API, 50 m3/m3 • Emulsions / Hydrates serious issues • Front-End engineering only concerned with horsepower / production relationship …. not stability • Used both static (for emulsions) and transient programs for the gas lift portion.

  16. SAMPLE CURVE FROM HEBRON

  17. Example: Effect of Wellbore Step Out For every set of conditions, an optimum and maximum case was done

  18. EFFECT OF WATERCUT / WELLHEAD PRESSURE FOR ALBA 700 PSI 500 PSI 750 PSI 700 PSI 500 PSI 750 PSI Pr=3200 psi Pr=2800 psi 0% 40% 95% 0% 40% 95%

  19. EXISTING SUBSEA GAS LIFT COMPLETION THAT CHEVRON DOES NOT RECOMMEND!! “the name / location has been removed to protect the innocent” • 16/64th valve • 20/64th valve • 28/64th valve • DUMMY VALVE !! Available gas injection pressure = 1300 psi from 3500 m away In addition, the “flow conduit” ID goes from 3.5” (gravel pack completion) to 9 5/8” (for 700 m / 2300 ft) to 4.5 (upper completion)

  20. Thank You For Listening Chevron’s World of Artificial Lift North Sea (ESP/GL) Canada (PCP/GL/BP/ESP) USA (PCP/GL/BP/ESP/JP) Kuwait (PCP) China (ESP/GL) Thailand (GL) Nigeria (ESP/GL) Venezuela (BP/ESP/PCP) Indonesia (ESP/BP/PCP/GL) Colombia (PCP) Angola (GL/PCP/CTESP) Australia (GL/BP) Argentina (BP/ESP/ GL)

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