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Bench Top Tests for Surfactant Selection

Bench Top Tests for Surfactant Selection. Ayantayo Ajani The University of Tulsa. Outline. Introduction Objectives Small Scale Experimental Set up Types of Surfactants Bench Top Tests Data Gathered Experimental Observations Brine and High Temperature Tests Preliminary Conclusions.

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Bench Top Tests for Surfactant Selection

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  1. Bench Top Tests for Surfactant Selection Ayantayo Ajani The University of Tulsa

  2. Outline • Introduction • Objectives • Small Scale Experimental Set up • Types of Surfactants • Bench Top Tests • Data Gathered • Experimental Observations • Brine and High Temperature Tests • 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. Introduction: Need for Testing Surfactants • Foaming agents are not all the same; they will perform differently on fluids of varying compositions • Apply a product that has been tested on fluids from applicable wells

  5. Objectives • To build an experimental facility that is 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

  6. Objectives • To investigate different foaming agents’ stability and liquid unloading potential at different surfactant concentrations, temperatures, and formation brine compositions.

  7. Outline • Introduction • Objectives • Small Scale Experimental Set up • Types of Surfactants • Bench Top Tests • Data Gathered • Experimental Observation • Brine and High Temperature Tests • Preliminary Conclusions

  8. Surfactants tested in this Study

  9. Small Scale Experiments • Bench Top Tests: • Surface Tension Test • Unloading Test • Stability Test

  10. Experimental Facility: Surface Tension Test Pendant Drop Method

  11. Experimental Facility: Base Fluid (DI Water) Surface Tension Results

  12. Results – Surface Tension Test

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

  14. 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

  15. Test Matrix - Liquid Unloading

  16. 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/Criterion for successful test

  17. 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

  18. Test Matrix – Stability Test

  19. Outline • Introduction • Objectives • Small Scale Experimental Set up • Types of Surfactants • Bench Top Tests • Data Gathered • Experimental Observations • Brine and High Temperature Tests • Preliminary Conclusions

  20. Experimental Observation: Least Gas Rate & Least Concentration for Sparging 100 mL of Test Solution

  21. Stability Test: Drained Volume (Sulphonate)

  22. Stability Test: Drained Volume (Cationic)

  23. Stability Test: Rate of Liquid Drainage, (mL/secs) (All Foamers)

  24. Stability Test: Half Life, (secs) (All Foamers)

  25. Stability Test: Appropriate Sparge Rate Required for Different Foamers

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

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

  28. Unloading Test: Mass Unloaded at 10 minutes: 750 mL

  29. Unloading Test: Unloaded Mass Using Concentrations at Half Life

  30. Experimental Observations • The tensiometer is not a good indicator of efficacy of surfactants based on half life, rate of liquid drainage and percent mass of liquid unloaded at 10 minutes • Stability parameters (half life, rate of liquid drainage & percent mass of liquid unloaded in 10 minutes) are better indicators of critical concentration for a given chemical • An ability to foam at low sparging rate is also a good indication of good surfactant

  31. Experimental Observations: Optimum Concentration Indicators

  32. Experimental Observations • Certain chemicals can foam effectively at low gas flow rates • Anionic and Sulphonate foamers are able to foam and show higher half life than other chemicals at low gas flow rates • At higher injection gas flow rates, the difference between different chemicals tend to be minimized at critical concentration

  33. Outline • Introduction • Objectives • Small Scale Experimental Set up • Types of Surfactants • Bench Top Tests • Data Gathered • Experimental Observation • Brine and High Temperature Tests • Preliminary Conclusions

  34. Brine Tests • Brine I • Saturated rock salt prepared in the laboratory • 150 g/L • Brine solution sample has been sent for composition analysis • Density = 1.0957 g/cm3 • Brine II • GOM model brine found in the literature • Composition: DI Water – 8743.60 g NaCl -1140 g CaCl2 -111g • Density = 1.0905 g/cm3

  35. Test Matrix – Brine & High Temperature Stability Test

  36. Brine & High Temperature: Half Life Vs. Drainage Rate

  37. Experimental Observation • Except in Brine II at 1000 ppm and 74 deg F, the Sulphonate lost its efficacy in Brine I, Brine I HT and Brine II HT when sparged at 0.40 LPM • It is worth while testing it in DI-water, the two Brine solutions and at high temperature using 0.75 LPM and 0.80 LPM

  38. Brine & High Temperature: Half Life Vs. Drainage Rate

  39. Experimental Observation • Cationic foamer exhibited enhanced foaming ability in Brine I and II at 74 deg. F using 0.80 LPM & 0.75 LPM • Interface cannot be followed • Test was re-conducted at 0.35 and 0.40 LPM for Brine II only • Visible interface • Could stop sparging gas when 100 mL test solution is converted to foam

  40. Brine II: Half Life Test; Cationic Foamer at Lower Gas Rate Failed

  41. Brine II: Drainage Rate Test; Cationic Foamer at Lower Gas Rate

  42. Test Matrix – Brine Unloading Test

  43. Brine & High Temperature: % Mass Unloaded in 10 mins

  44. Brine & High Temperature: % Mass Unloaded in 10 mins

  45. Preliminary Conclusions • Anionic foamer is resistant to both brine and high temperature • Although its efficacy was impacted • Sulphonate foamer is impacted by brine and high temperature at 0.35 & 0.40 LPM gas rate • Further tests required at 0.75 & 0.80 LPM before its performance can be fully described

  46. Preliminary Conclusion • Amphoteric foamers I and II are resistant to Brine and high temperature • Although both were slightly impacted • Amphoteric II shows better resistance • Cationic foamer exhibited enhanced foaming ability in brine and good resistance to high temperature • It is more effective in brine than in de-ionized water

  47. Bench Top Tests for Surfactant Selection Questions Recommendations

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