1. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Sergio Caicedo ASME/API Gas-Lift Workshop Houston, Texas, Spring 2002

2. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions OUTLINE Introduction Two-packer Chamber Equations Insert Chamber Equations Algorithm Results Conclusions Recommendations

3. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Chamber Lift Application Window Particularly suitable for wells with very low reservoir pressure, high productivity Chamber Lift Design Goal Accumulate more liquid volume per bottom hole flowing pressure Chamber Lift Main Problem Formation Gas in the chamber INTRODUCTION

4. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Production Cycle Accumulation Stage Liquid Accumulation In Annulus and Tubing Formation Gas Accumulation in Annulus Described by Gas and Liquid balance coupled with Reservoir inflow Chamber Displacement Slug Lifting Venting INTRODUCTION

5. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions TWO-PACKER CHAMBER COMPLETION TWO-PACKER CHAMBER EQUATIONS

6. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Gas Balance in the annulus Liquid Balance Pressure relationship TWO-PACKER CHAMBER EQUATIONS P anu P top Y anu Y top Bleeding Valve Operating Valve m gout  m gres Standing Valve Y perf Y pinf

7. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions 2x2 System of Non Linear Differential equations !!! TWO-PACKER CHAMBER EQUATIONS P anu P top Y anu Y top Bleeding Valve Operating Valve m gout  m gres Standing Valve Y perf Y pinf

8. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Reservoir Inflow Bottom Hole Flowing Pressure Gas rate through the Bleeding Valve TWO-PACKER CHAMBER EQUATIONS P anu P top Y anu Y top Bleeding Valve Operating Valve m gout  m gres Standing Valve Y perf Y pinf

9. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions INSERT CHAMBER COMPLETION INSERT CHAMBER EQUATIONS

10. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Gas Balance in the external annulus Gas Balance in the internal annulus Liquid Balance INSERT CHAMBER EQUATIONS Y perf P anu1 P top Y an u1 Y top Bleeding Valves Operating Valve m 1gout      m gres P anu2   m gres m 2gout Y anu 2 Standing Valve Y pinf

11. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Gas rate through the Bleeding Valves INSERT CHAMBER EQUATIONS Y perf P anu1 P top Y an u1 Y top Bleeding Valves Operating Valve m 1gout      m gres P anu2   m gres m 2gout Y anu 2 Standing Valve Y pinf

12. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions ALGORITHM

13. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions The key to simulate the accumulation process in both cases is to introduce the proper initial conditions and suitable boundary or limit conditions. For instance, the initial level in the annulus is zero because all the liquid has been displaced during the previous injection stage, meanwhile the initial liquid level depends on the fall back of the slug in the previous production cycle. Among the limit conditions, the limit when the liquid level in the annulus approaches zero requires special care in order to keep the system consistent. INITIAL AND BOUNDARY CONDITIONS

14. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Liquid Levels vs. Time for a 100-feet two-packer chamber with a 3/16" bleeding port and 10% of gas coming into the annulus RESULTS Annular & Tubing Liquid Levels vs. Accumulation Time Column (ft) Accumulation Time (s) -- Annulus -- Tubing

15. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Liquid Levels vs. Time for a 100-feet two-packer chamber with a 1/32” bleeding port and 10% of gas coming into the annulus. Annular & Tubing Liquid Levels vs. Accumulation Time Column (ft) Accumulation Time (s) RESULTS -- Annulus -- Tubing

16. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions. Liquid Levels vs. Time for a 100-feet two-packer chamber with a 3/16” bleeding port and 50% of gas coming into the annulus. Annular & Tubing Liquid Levels vs. Accumulation Time Column (ft) Accumulation Time (s) RESULTS -- Annulus -- Tubing

17. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Liquid Levels vs. Time for a 200-feet Insert Chamber with a 3/16” internal and external bleeding ports. Annular & Tubing Liquid Levels vs. Accumulation Time Column (ft) Accumulation Time (s) RESULTS -- Annulus1 -- Annulus2 -- Tubing

18. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Liquid Levels vs. Time for a 200-feet Insert Chamber with a 3/16” internal and a 1” external bleeding ports Annular & Tubing Liquid Levels vs. Accumulation Time Column (ft) Accumulation Time (s) RESULTS -- Annulus1 -- Annulus2 -- Tubing

19. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Liquid Levels vs. Time for a 200-feet Insert Chamber with 1" internal and external bleeding ports Annular & Tubing Liquid Levels vs. Accumulation Time Column (ft) Accumulation Time (s) RESULTS -- Annulus1 -- Annulus2 -- Tubing

20. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Insert Chamber Improvement RESULTS P anu1 P top Y an u1 Y top Bleeding Valves Operating Valve m 1gout      m gres P anu2   m gres m 2gou t Y an u2 Standing Valve Y perf Y pinf

21. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Liquid Levels vs. Time for a 200-feet Insert Chamber with a 3/16" internal and a 1/2" external bleeding ports Annular & Tubing Liquid Levels vs. Accumulation Time Column (ft) Accumulation Time (s) RESULTS -- Annulus1 -- Annulus2 -- Tubing

22. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions The complexity of the accumulation process in chamber lift requires the previous analysis for a better sizing of the bleeding valves. The coherence and physical behavior of the results along with the field experiences backups the theoretical model and the numerical method. The slight differences between the two-packer and insert chambers completions do not allow applying the same practices in both installations. CONCLUSIONS

23. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions In insert chamber completions it is highly recommended to connect directly the external annulus with the tubing whether it is possible. Apply the model developed in this paper when designing or simulating wells with two-packer or insert chamber lift installations. Start a research work in order to determine the gas percentages of separation that flow into the annulus and tubing in chamber lift installations in order to include that key information in the presented model. RECOMMENDATIONS

24. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions QUESTIONS ??? FEEL FREE PLEASE

25. PDVSA INTEVEP Accumulation Process and Phenomena in Chamber Lift Completions Thanks for your attention