SURFACTANT SYSTEMS FOR EOR IN HIGH-TEMPERATURE HIGH-SALINITY ENVIRONMENTS Maura Puerto, George J. Hirasaki, Clarence A. Miller, Rice University Julian R. Barnes, Shell Global Solutions International B.V. 1 SPE

2 Objective Without addition of alcohol, determine the potential of Alkoxy Glycidyl Sulfonates (AGS) and Internal Olefin Sulfonates (IOS) for EOR in high-temperature, high-salinity environments. Focusing in Finding low-tension microemulsion systems that could be injected as aqueous, single-phase compositions for a range of high temperatures and salinities found in many potential EOR projects.

3 Fluids NaCl-only brines NaCl-only brines and n-octane at WOR~ 1 n- Octane : The optimal salinities of various surfactants are not greatly different when determined against either n-octane or many crude oils (Cayias et al 1976, Nelson 1983). Experimental Tests were carried out in oil baths with Glass Pipette Method* * Barnes, J.R., Smit, J.P., Smit, J.R., Shpakoff, P.G., Raney, K.H., Puerto, M.C., 2008 Development of surfactants for chemical flooding at difficult reservoir conditions, SPE presented at Symp. on IOR, Tulsa, OK.. 6 “

4 Alkoxy Glycidyl Sulfonates (AGS) AGS hydrophobes from primary NEODOL TM alcohols NEODOL 23 → C12,13 alcohol 80% linear, 20% branched NEODOL 25 → C12-15 alcohol NEODOL 67 → b-C16,17 alcohol fully methyl branched Thermally stable (unlike alkoxy sulfates), High Salt, Ca ++, Mg ++ tolerance Internal Olefin Sulfonates (IOS) IOS Internal Olefin with carbon cut C20-24, two different feedstocks and different sulfonation conditions. Batches A, B, C (Barnes et al, 2008) Range of optimal salinities from about 1%-7% NaCl Thermally stable; less Ca ++, Mg ++ tolerance than AGS

Optimal Salinity Map Glycidyl Sulfonates (2%) against n-octane, 120°C 5 Example of AGS Limitation 2% aqueous N679EO_N25 7EO 70°C Aqueous Saline Solutions separate into two clear liquid phases similar to the Cloud Point phenomenon observed in non-ionic surfactants Map provides starting point for initial surfactant selection AGSs Advantage: high oil solubilization Limitation: aqueous saline solutions separate

6 Three Examples of Phase Behavior of Ethoxylated GS Neodol Alcohols- (O CH 2 -CH 2 ) x -C C-SO 3 Na OH

2% b-C16,17 – 9EO GS salinity scan MW ~ 760 WOR~1, n-octane at 120°C 7 Ethoxylated GS : Phase Behavior Example 1 Phases clear at test temperature Difficult to photograph

2% C12,13 - 3EO GS. MW ~ 460 WOR ~ 1, n-octane, NaCl brine 8 Ethoxylated GS : Phase Behavior Example 2

2% C EO GS sample with 19.8% NaCl, WOR~1, n-octane, 120°C at four times after removal from oil bath 9 Ethoxylated GS : Phase Behavior Example 3

Effect of temperature on Optimal Salinity, Cø Ethoxylated GS 10 Cø decreases about 0.15% NaCl/°C

11 Test results and Examples of Propoxylated GS Neodol Alcohols- (O CH 2 -CH 2 ) x -C C-SO 3 Na OH CH 2

Solubilization Parameters at 95°C and 130°C WOR~1, n-octane 12 b-C16,17 - 3PO GS C ø, appears independent of temperature (Vo/Vs) Cø decreases as temperature increases Effect of Adding PO groups to a large Hydrophobe such as b-C16,17 Example

Optimal Salinity, Cø, Vs. Number of POs 2% b-C16,17 - xPO GS with octane at selected temperatures 13 Cø is independent of temperature in range tested Propoxylated GS Effect of Adding PO Groups to a Large Hydrophobe Such as b-C16,17

2% b-C16,17 - 7PO GS with octane at 110°C. 14 Effect of Adding PO groups to a large Hydrophobe such as b-C16,17 VCPs can be eliminated by (1)+ alcohol (2)↑ test temperature (3)↨ oil molar volume of test oil 2% NaCl High-viscosity phase or Very Condensed Phase (VCP) Looks like a soft piece of wax

15 IOSs are mixtures SO 3 -Na SO 3 -Na R-CH 2 -CH 2 - CH –CH -CH 2 -CH 2 -R’ + R-CH 2 – CH-CH= CH-CH 2 -R’ OH Hydroxyalkane Sulfonates + Alkene Sulfonates

IOS Phase behavior Example IOS (batch C) with octane 16

Summary of C ø and (Vo/Vs) Cø for IOS Further research needed on the effects of feedstock & variations in the sulfonation process High (Vo/Vs) Cø for batch C unlikely caused only by disulfonates; other factors such as hydroxyalkanesulfonates / alkenesulfonates make significant contributions to the observed behavior.

Solubility Maps IOS Batches A, B and C 18 In General: Solubility increases with increasing temperature but boundary between regions shifted to lower salinites for batches A and B, indicating that they are much less soluble. Differences in solubility attributable to different IO feedstocks and synthesis parameters (temperature, aging, degree of sulfonation etc.) B A C

Application Example Blend scan for b-C16,17 - 9EO GS and IOS (Batch C) n-octane and synthetic reservoir brine at 90°C 19 60/40 50/50 40/60 30/70 20/80 10/90 0/100 Optimal Blend : 45/55

Solubility Map of Blends Synthetic sea water (Ca, Mg) b-C16,17 - 9EO GS and IOS (Batch C) 20 A suitable choice for injection in an EOR process is the 50/50 blend, which is soluble from 25°C - 90°C, only slightly under-optimum with n-octane and field brine at 90°C. IOS GS

Conclusions 1 Alkyl Glycidyl Sulfonates (AGS ) Many n-octane/NaCl brine systems exhibit classical Winsor phase behavior with no added alcohol or other cosolvents for temperatures between about 85°C and 120°C. Optimal salinities from less than 1% NaCl to more than 20% NaCl have been observed with different combinations of (EO or PO) and chain length. Oil solubilization is high, indicating ultralow IFTs near optimal conditions. Salinity Maps can provide useful tools for initial surfactant selection. 21

Conclusions 2 AGS Aqueous Saline Solutions Separate into two liquid phases at elevated temperatures. This could compromise the EOR process. 22

Conclusions 3 IOS surfactants IOS surfactants are suitable for high temperature reservoir conditions and can be adjusted to work over a wide range of optimal salinities by varying the internal olefin (IO) feedstock and sulfonation condition. 4 Blends of AGS and IOS Have promise for overcoming AGS limitation (two liquid phases at elevated temperatures) but still providing the ultralow IFTs that are required to displace oil. 23

Special Thanks to Shell Global Solutions International B.V. for supporting this work at Rice University. 24 Questions Discussion Thank You!