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Foam Flow Small vs. Large Scale Facilities

Foam Flow Small vs. Large Scale Facilities. Ayantayo Ajani The University of Tulsa. Outline. Introduction Objectives Small Scale Experimental Set up Data Collection Prediction of Holdup Preliminary Conclusions. Introduction.

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Foam Flow Small vs. Large Scale Facilities

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  1. Foam FlowSmall vs. Large Scale Facilities Ayantayo Ajani The University of Tulsa

  2. Outline • Introduction • Objectives • Small Scale Experimental Set up • Data Collection • Prediction of Holdup • Preliminary Conclusions

  3. Introduction • Accumulation of formation water, condensed water or hydrocarbon condensate at the bottom of a well can cause decline in reservoir pressure and this will result in decline in gas well’s production rate • Chemical foamers are used as a means of artificial lift to enhance the productivity of gas wells

  4. How Do Surfactants Work? • Foam consist of small bubbles surrounded by thin liquid film • The foam structure has a reduced gravitational gradient due to high gas holdup • The slippage between gas and liquid under foam conditions is reduced.

  5. Desirable Characteristics • Stability – should be stable with little agitation; however, cannot be too stable so that it cannot be separated at separator • Flexibility & Tolerance – should create foam at varied conditions – different concentrations of brines and various temperatures • Concentration – should be effective at low concentration to be cost effective

  6. Objectives • To build an experimental facility that will be used to study the foaming ability and unloading potential of surfactants. • To use stability and unloading rig test to evaluate efficacy of foamers (Bench Top Test) • To define appropriate measurement parameters for foam stability which will capture foam behavior as desired in gas wells

  7. Objectives • To investigate different foaming agents’ liquid unloading potential at different surfactant concentrations, temperatures, and formation brine compositions. • To extrapolate results from above in studying surfactant effect on pressure gradient and liquid holdup in 2-in and 4-in 40-ft vertical pipes (Large scale test)

  8. Objectives • To develop a model which will utilize the transient data in small scale facility (foam height vs. time, liquid collected vs. time) to predict the behaviour in gas wells

  9. Outline • Introduction • Objectives • Small Scale Experimental Set up • Data Collection • Prediction of Holdup • Preliminary Conclusions

  10. Progress on Experiment • S-2158 - Completed • S-2557 - Completed • S-3311 - This ABM • S-2160 • S-3442

  11. Experiments • Bench Top Tests: • Surface Tension Test • Unloading Test • Stability Test

  12. Surface Tension Test - Pendant Drop Method

  13. Results – Surface Tension Test 400 ppm 600 ppm 2400 ppm

  14. Unloading Test • Features • Filtered compressed air at 18psi • Porous ceramic disc • Heating jacket • Weighing scale connected to PC • Procedure

  15. Data Gathered - Liquid Unloading • The unloading rate is reported as the percent of liquid transferred at 10 minutes after the test is started. • Unloading rate (mL/sec) • Quantifies the incremental unloading benefit (volumetric rate per time) associated with using a higher concentration of the surfactant. X 100

  16. Test Matrix - Liquid Unloading

  17. Stability Test • Features • Modifications of the unloading rig • Unloading facility was used to conduct stability test • Stability and Unloading tests have similar foam quality • Procedure

  18. Data Gathered at Varying Concentration - Stability Test • Drained volume with time • Volumetric rate of liquid drainage, • Half life – time to recover 50% of initial liquid

  19. Test Matrix – Stability Test

  20. Outline • Introduction • Objectives • Small Scale Experimental Set up • Data Collection • Prediction of Holdup • Preliminary Conclusions

  21. Experimental Observation : Stability Test (S3311) • Air rate driven: • 0.75 & 0.80 LPM vs 0.35 & 0.40 LPM (S2158) • Concentration lower limit • <600 ppm – 100 mL cannot be sparged fully

  22. Experimental Observation: Stability Test (S3311)

  23. Volumetric Rate of Liquid Drainage, (mL/ secs)

  24. Experimental Observation : Half Life, (secs)

  25. Unloading Test: 750 mL

  26. Mass Unloaded at 10 minutes

  27. Mass Unloaded at 10 minutes: 750 mL

  28. Outline • Introduction • Objectives • Small Scale Experimental Set up • Data Collection • Prediction of Holdup • Preliminary Conclusions

  29. Exploratory Holdup Model

  30. Exploratory Holdup Model

  31. Exploratory Holdup Model • A relationship exist between pressure gradient and holdup in 4-in pipe up to the minimum pressure gradient point • Predict holdup • Residual/frictional pressure gradient dominates in 2-in pipe • Predict frictional pressure gradient

  32. Exploratory Holdup Model Under Foam Flow: 750 mL, 0.75 LPM

  33. Liquid Holdup: S-2158, 2 inch, Vsl = 0.01 m/s

  34. Liquid Holdup Prediction Under Foam Flow • Slope of linear part of unloading plot (incremental unloading benefit associated with using a higher concentration of the surfactant, (mL/sec)) • Rate of Liquid Removal, (m/s)

  35. Liquid Holdup Prediction Under Foam Flow: 750 mL Test Solution

  36. Liquid Holdup Prediction Under Foam Flow • Unloading test data: 750 mL, 0.50 LPM • n • Unloading test data: 750 mL, 0.75 LPM • n

  37. Liquid Holdup Prediction Under Foam Flow: 750 mL Unloading Test Data

  38. Liquid Holdup Prediction Under Foam Flow • Model is still been developed to accommodate slip at higher holdup values (>5%) • Two surfactants are yet to be tested

  39. Preliminary Conclusions • Half life values (slide 24) • S-2158 (70 secs) • S-3311 (38 secs) • S-2557 (36 secs) • S-2158 retains liquid more hence have highest volumetric rate of liquid removal (slide 36) • Using concentrations at half life: • S-2158 (1000ppm), S-2557 (600 ppm) & S-3311 (1000 ppm): • S-2158 unloads 75% of its initial mass at 10 minutes; S-2557 and S-3311 unloaded 54% and 67% respectively (slide 33)

  40. Preliminary Conclusions • Holdup in the large scale test could be predicted by using the volumetric rate of liquid unloaded in the small scale unloading rig test. • S-2158 has a higher unloading potential than S-2557 and S-3311 based on its higher volumetric rate of liquid removal (slide 36) • To be justified further in the holdup analysis of the large scale test

  41. Preliminary Conclusions • More stability and unloading tests are required for S-2557 to determine its optimum unloading potential • Concentration of foamers corresponding to highest half life value (stability test), percentage of unloaded mass at 10 minutes and volumetric rate of liquid removal (unloading test) are quite different from those measured with the tensiometer.

  42. Future Work • Conduct small scale test on S-2160 and S-3442 • Conduct stability test at room temperature and high temperatures using saturated rock salt solution (alternative for formulated brine) • Conclude all large scale test summer 2014 • Predict holdup and pressure gradient under foam flow

  43. Timeline • Literature Review Ongoing • Building Facility Completed • Collection of Expt data Ongoing • Building Foam Flow Model Ongoing • Building Model/Validation Sept 2014 • Final Report Oct 2014

  44. Foam Flow Small vs. Large Scale Facilities Acknowledgements Questions? Recommendations

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