July 29, Bench Top Tests for Surfactant Selection Ayantayo Ajani The University of Tulsa

July 29, Outline Introduction Objectives Small Scale Experimental Set up o Types of Surfactants o Bench Top Tests o Data Gathered Experimental Observations Brine and High Temperature Tests Preliminary Conclusions

July 29, 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

July 29, 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

July 29, 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

July 29, Objectives To investigate different foaming agents’ stability and liquid unloading potential at different surfactant concentrations, temperatures, and formation brine compositions.

July 29, Outline Introduction Objectives Small Scale Experimental Set up o Types of Surfactants o Bench Top Tests Data Gathered Experimental Observation Brine and High Temperature Tests Preliminary Conclusions

July 29, Surfactants tested in this Study Product NameSurfactant Type Specific Gravity pHChemical CompositionWeight % MC MXI ANIONIC Surfactant Isopropyl alcohol Varies 5-10 MC MXI AMPHOTERIC I – – 8.0Surfactant30-60 MC-MX AMPHOTERIC II Surfactant NaCl MC-MXI SULPHONATE (ANIONIC) – Dodecane-1-sulfonic acid, Na Salt Dodecanesulfonic acid, hydroxyl-, Na salt Dodecene1-5 Sodium sulfate1-5 MC-MX FLUOROCHEMICAL CATIONIC SURFACTANT Fluorochemical cationic Surfactant Hexylene glycol7-13

July 29, Small Scale Experiments Bench Top Tests:  Surface Tension Test  Unloading Test  Stability Test

July 29, Experimental Facility: Surface Tension Test Pendant Drop Method

July 29, Experimental Facility: Base Fluid (DI Water) Surface Tension Results

July 29, Results – Surface Tension Test

July 29, Unloading Test Features  Filtered compressed air at 18psi  Porous ceramic disc  Heating jacket  Weighing scale connected to PC Procedure

July 29, 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.

July 29, Test Matrix - Liquid Unloading Anionic Amphoteric I Amphoteric II SulphonateCationic Sparger size, (micron) 22 Initial Volume, (mL) 750, Gas Flowrate, (LPM) 0.50, 0.75 Concentrati ons, (ppm) 400, 600, 800, 1000, 1600, 2000, 2400, , 200, 300, 400, 600, 800, , 200, 300, 400, 600, 800, 1000, 1400, 2000, , 600, 800, 1000, 1200, 1600, , 1000, 1200, 1600, 2000, 2400, 3000, 4000, 5000

July 29, 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

July 29, 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

July 29, Test Matrix – Stability Test Anionic Amphoteric I Amphoteric II SulphonateCationic Sparger size, (micron) 22 Initial Volume, (mL) 100 Gas Flowrate, (LPM) 0.35, , , , 0.80 Concentrati ons, (ppm) 400, 600, 800, 1000, 1600, 2000, 2400, , 200, 300, 400, 600, 800, , 800, 1000, 1400, 2000, , 600, 800, 1000, 1200, 1600, , 1000, 1200, 1600, 2000, 2400, 3000, 4000, 5000

July 29, Outline Introduction Objectives Small Scale Experimental Set up o Types of Surfactants o Bench Top Tests Data Gathered Experimental Observations Brine and High Temperature Tests Preliminary Conclusions

July 29, Experimental Observation: Least Gas Rate & Least Concentration for Sparging 100 mL of Test Solution

July 29, Stability Test: Drained Volume (Sulphonate)

July 29, Stability Test: Drained Volume (Cationic)

July 29, Stability Test: Rate of Liquid Drainage, (mL/secs) (All Foamers)

July 29, Stability Test: Half Life, (secs) (All Foamers)

July 29, Stability Test: Appropriate Sparge Rate Required for Different Foamers

July 29, Exploratory Holdup Model Under Foam Flow: 750 mL, 0.75 LPM

July 29, Exploratory Holdup Model Under Foam Flow: 750 mL, 0.75 LPM

July 29, Unloading Test: Mass Unloaded at 10 minutes: 750 mL

July 29, Unloading Test: Unloaded Mass Using Concentrations at Half Life

July 29, 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

July 29, Experimental Observations: Optimum Concentration Indicators SampleTensiometerRate of Liquid Drainage, (mL/secs) Half Life, (secs) Mass Unloaded in 10 mins, (%) [0.50 LPM Tests] Anionic2400 ppm1600 ppm Plateau at 1000 ppm Amphoteric I400 ppm600 ppm Inflection at 600 ppm Amphoteric II600 ppm1000 ppm Inflection at 1000 ppm Sulphonate3000 ppm1000 ppm Plateau at 800 ppm Cationic3000 ppm Unstable

July 29, Experimental Observations Certain chemicals can foam effectively at low gas flow rates o 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

July 29, Outline Introduction Objectives Small Scale Experimental Set up o Types of Surfactants o Bench Top Tests Data Gathered Experimental Observation Brine and High Temperature Tests Preliminary Conclusions

July 29, Brine Tests Brine I o Saturated rock salt prepared in the laboratory o 150 g/L o Brine solution sample has been sent for composition analysis o Density = g/cm3 Brine II o GOM model brine found in the literature o Composition: DI Water – g NaCl g CaCl2 -111g o Density= g/cm3

July 29, Test Matrix – Brine & High Temperature Stability Test Anionic Amphoteric I Amphoteric II SulphonateCationic Gas Flowrate, (LPM) Concentration at Half Life, (ppm) *400, Stability Test Solution Brine I at 74 deg. F Brine I at 150 deg. F Brine II at 74 deg. F Brine II at 150 deg. F

July 29, Brine & High Temperature: Half Life Vs. Drainage Rate

July 29, 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

July 29, Brine & High Temperature: Half Life Vs. Drainage Rate

July 29, Experimental Observation Cationic foamer exhibited enhanced foaming ability in Brine I and II at 74 deg. F using 0.80 LPM & 0.75 LPM o 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

July 29, Brine II: Half Life Test; Cationic Foamer at Lower Gas Rate Failed

July 29, Brine II: Drainage Rate Test; Cationic Foamer at Lower Gas Rate

July 29, Test Matrix – Brine Unloading Test Anionic Amphoteric I Amphoteric II SulphonateCationic Concentration at half Life, (ppm) *400, Sparge Rate, (LPM) 0.50, 0.75 Unloading Test Solution Brine I at 74 deg. F Brine II at 74 deg. F

July 29, Brine & High Temperature: % Mass Unloaded in 10 mins

July 29, Brine & High Temperature: % Mass Unloaded in 10 mins

July 29, Preliminary Conclusions Anionic foamer is resistant to both brine and high temperature o Although its efficacy was impacted Sulphonate foamer is impacted by brine and high temperature at 0.35 & 0.40 LPM gas rate o Further tests required at 0.75 & 0.80 LPM before its performance can be fully described

July 29, Preliminary Conclusion Amphoteric foamers I and II are resistant to Brine and high temperature o Although both were slightly impacted o Amphoteric II shows better resistance Cationic foamer exhibited enhanced foaming ability in brine and good resistance to high temperature o It is more effective in brine than in de- ionized water

July 29, Bench Top Tests for Surfactant Selection Questions Recommendations