Injection fluids comprising anionic surfactants and alkoxylated alcohols and the use of such fluids in chemical enhanced oil recovery processes

Abstract

A method for using a surfactant formulation in chemical enhanced oil recovery, wherein said surfactant formulation comprises at least: (i) an anionic salt of an alkyl alkoxylated sulfate, wherein said alkyl alkoxylated sulfate has a molecular structure as shown in (I), wherein R is a linear, branched or mixture of linear and branched alkyl group having from 10 to 20 carbon atoms, n=4 −15, m=0-10, M+ is an alkali metal ion, an alkanolamine ion, an alkyl amine ion or an ammonium ion; and (ii) a non-ionic alcohol O ethoxylate, wherein said alcohol ethoxylate has a molecular structure as shown in (II), wherein R.sub.1 is a linear, branched or mixture of linear and branched alkyl group having from 8 to 24 carbon atoms, y=20-100. ##STR00001##

Claims

1. A surfactant formulation for use in chemical enhanced oil recovery, wherein said surfactant formulation comprises at least: i) an anionic salt of an alkyl alkoxylated sulfate, wherein said alkyl alkoxylated sulfate has a molecular structure as shown in [I]: ##STR00006## wherein R is a linear, branched or mixture of linear and branched alkyl group having from 10 to 20 carbon atoms, n=4-15, m=0-10, M.sup.+is an alkali metal ion, an alkanolamine ion, an alkyl amine ion or an ammonium ion; and ii) a non-ionic alcohol ethoxylate, wherein said alcohol ethoxylate has a molecular structure as shown in [II]: ##STR00007## wherein R1 is a linear, branched or mixture of linear and branched alkyl group having from 8 to 24 carbon atoms, y=20-100.

2. The surfactant formulation of claim 1, wherein R is a branched alkyl group.

3. The surfactant formulation of claim 2, wherein R is a 2-alkyl branched group.

4. The surfactant formulation of claim 1, wherein m=0.

5. The surfactant formulation of claim 1, wherein R has from 12 to 16 carbon atoms.

6. The surfactant formulation of claim 1, wherein R.sub.1=C.sub.12-C.sub.24.

7. The surfactant formulation of claim 1, wherein 40≤y 100.

8. The surfactant formulation of claim 1 wherein the weight ratio of i)/ii) is from 6:1 to 1:6.

9. The surfactant formulation of claim 1 wherein the combined concentration of i) and ii) does not exceed 0.5 weight % of the total formulation.

10. The surfactant formulation of claim 1 wherein said surfactant formulation lowers the interfacial tension of crude oil to ultralow values of at or below 10.sup.−1 mN/m.

11. The surfactant formulation of claim 1 above wherein said surfactant formulation is able to lower interfacial tension values of crude oil in brines with salinities from 4% up to 15% total dissolved solids.

12. A method for chemical enhanced oil recovery from a subterranean formation that is penetrated by at least one injection well and one production well, comprising: i) injecting into an injection well a surfactant formulation such that said surfactant formulation contacts crude oil present in said subterranean formation to lower the interfacial tension of said crude oil to ultralow values at or below 10.sup.−2 mN/m, said surfactant formulation being able to lower interfacial tension values in temperatures from 25° C. up to 70° C. and in brines with from 4% up to 15% total dissolved solids, at least a portion of said dissolved solids being divalent cations, said surfactant formulation comprising at least a) an anionic salt of an alkyl alkoxylated sulfate, wherein said alkyl alkoxylated sulfate has a molecular structure as shown in [I]: ##STR00008## wherein R is a linear, branched or mixture of linear and branched alkyl group having from 10 to 20 carbon atoms, n=4-15, m=0-10, M.sup.+is an alkali metal ion, an alkanolamine ion, an alkyl amine ion or an ammonium ion; and b) a non-ionic alcohol ethoxylate, wherein said alcohol ethoxylate has a molecular structure as shown in [II]: ##STR00009## wherein R1 is a linear, branched or mixture of linear and branched alkyl group having from 8 to 24 carbon atoms, y=20-100, recovering oil from the subterranean formation from a production well.

13. The method of claim 12, wherein R is a branched alkyl group.

14. The method of claim 12, wherein R is a 2-alkyl branched group.

15. The method of claim 12, wherein m=0.

16. The method of claim 12, wherein R has from 12 to 16 carbon atoms.

17. The method of claim 12, wherein R.sub.1=C.sub.12-C.sub.24.

18. The method of claim 12, wherein 40<y≤100.

19. The method of claim 12, wherein the weight ratio of i)/ii) is from 6:1 to 1:6.

20. The method of claim 12, wherein the combined concentration of i) and ii) does not exceed 0.5 weight % of the total formulation.

21. The method of claim 12, wherein said surfactant formulation lowers the interfacial tension of crude oil to ultralow values of at or below 10.sup.−1 mN/m.

22. The method of claim 12, wherein said surfactant formulation is able to lower interfacial tension values of crude oil in brines with salinities from 4% up to 15% total dissolved solids.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the dynamic IFT in 4% TDS brine of formulations of MIPA salt of ISALCHEM C12/C13-8 PO sulfate (0.4 wt %) and co-surfactant (0.1 wt %) with heavy crude oil (Crude H1) over the temperature range of 25-60° C.

(2) FIG. 2 shows the dynamic IFT in 4% TDS brine of MIPA salt of ISALCHEM C12/C13-8 PO sulfate (0.4 wt %) and co-surfactant (0.1 wt %) with light crude oil (Crude L1) over the temperature range of 25-60° C.

(3) FIG. 3 shows the dynamic IFT in 4% TDS brine of MIPA salt of ISALCHEM C12/C13-8 PO sulfate (0.4 wt %) and co-surfactant (0.1 wt %) for various crude oils at 25° C.

(4) FIG. 4 shows the dynamic IFT in 4% TDS brine of MIPA salt of ISALCHEM C12/C13-8 PO sulfate (0.4 wt %) and co-surfactant (0.1 wt %) for various crude oils at 40° C.

(5) FIG. 5 shows the dynamic IFT in 4% TDS brine of MIPA salt of ISALCHEM C12/C13-8 PO sulfate (0.4 wt %) and co-surfactant (0.1 wt %) for various crude oils at 60° C.

(6) FIG. 6A shows the dynamic IFT of MIPA salt of ISALCHEM C12/C13-8 PO sulfate and Surfactant 1 at various surfactant concentration ratios in 4% TDS brine for Crude H1 oil at 25° C.

(7) FIG. 6B shows the dynamic IFT of MIPA salt of ISOFOL C16-8 PO sulfate and Surfactant 1 at various surfactant concentration ratios in 4% TDS brine for Crude H1 oil at 25° C.

(8) FIG. 7 shows the dynamic IFT in 11.8% TDS brine of MIPA salt of ISALCHEM C12/C13-4 PO sulfate (0.25 wt %) and Surfactant 1 (0.25 wt %) for various crude oils at 25° C.-40° C.

(9) FIG. 8 shows the dynamic IFT in 11.8% TDS brine of MIPA salt of ISALCHEM C12/C13-4 PO sulfate (0.25 wt %) and co-surfactant (0.25 wt %) for various crude oils at 40° C.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(10) The surfactant formulations of the present invention deliver aqueous-stable solutions over a range of temperatures and salinities, and produce ultra-low interfacial tensions with a very wide variety of crude oils. The performance of these formulations can be improved by tailoring the hydrophobe structures, together with the number of PO and or EO units of both the anionic and non-ionic structures to the needs of a specific well.

Materials

(11) The surfactants used to prepare the surfactant formulations for the examples, are mixtures of anionic and non-ionic surfactants. The anionic surfactants specifically evaluated are in particular methyl isopropyl amine (MIPA) and sodium (Na) salts of alkyl alkoxylated sulfates, and include, but are not limited to the surfactant structures derived from alcohols with propoxy (PO) and/or ethoxy (EO) units as described in Table 1.

(12) TABLE-US-00001 TABLE 1 Structures of anionic alkyl alkoxylated sulphate salts Alcohol Alcohol chain Alcohol Number Number name length structure of PO of EO ZIEGLER C10 100% linear 4-15 1 ISALCHEM C12/C13 95% 2-alkyl 4-8  0 branched SAFOL23 C12/C13 50% internally 7-13 3 branched, 50% linear ISOFOL C12-C16 100% 2-alkyl 8-15 0 branched

(13) The non-ionic co-surfactants used are alkoxylated alcohols, in particular ethoxylated alcohols. Suitable alcohols that can be used to synthesize the above described alkoxylated alcohols include, but are not limited to linear alcohols such as linear C6 alcohols (e.g. ALFOL 6) and C20+ alcohols (e.g. ALFOL 20+), and branched alcohols such as 2-alkyl-1-alkanols (Guerbet alcohols, e.g. ISOFOL 12 and ISOFOL 20), and isotridecyl alcohols (e.g. MARLIPAL O13, a C13 oxo-alcohol). All examples represented by trade names are marketed by Sasol Performance Chemicals.

(14) TABLE-US-00002 TABLE 2 Structures of non-ionic ethoxylated alcohols. Non-ionic Alcohol Number Co-surfac- chain Alcohol of tant Alcohol name length structure EO Surfactant 1 ALFOL20+ C20+ linear, long 20, 50, alkyl chain 75, 100 Surfactant 2 ISOFOL 20 C20 2-alkyl 50 branched, long chain Surfactant 3 ISOFOL 24 C24 2-alkyl 50 branched, long chain Surfactant 4 ALFOL20+ C20+ linear, long 25 chain Surfactant 5 iTDA C13 branched, 50 (isotridecanol) medium chain Surfactant 6 ISOFOL 12 C12 2-alkyl 50 branched, medium chain Surfactant 7 ALFOL C6 linear, short 50 6 chain Surfactant 8 iTDA C13 branched, 30 (isotridecanol) medium chain Surfactant 9 ISOFOL 12 C12 2-alkyl 29 branched, medium chain Surfactant 10 ALFOL C6 linear, short 15 6 chain Surfactant 11 iTDA C13 branched, 8 (isotridecanol) medium chain Surfactant 2-ethylhexanol C8 branched, 50 12 short chain

Experimental Section

(15) The brines used in this study have the composition and total dissolved solid (TDS) as shown in Table 3. Brine A, Brine B and Brine C have total divalent concentrations of −4%, 11.8%, and 15%, respectively.

(16) TABLE-US-00003 TABLE 3 Composition of brines used. Component Composition, g/L (a) Brine A with 4% TDS NaCl 30.39 KCl 1.51 CaCl.sub.2•2H.sub.2O 6.73 MgCl.sub.2•6H.sub.2O 1.39 TDS 4% (b) Brine B with 11.8% TDS NaCl 106.03 Na.sub.2SO.sub.4 0.74 MgCl.sub.2•6H.sub.2O 1.23 CaCl.sub.2 10.767 TDS 11.8% (c) Brine C with 15% TDS NaCl 113.96 KCl 5.65 MgCl.sub.2•6H.sub.2O 5.23 CaCl.sub.2•2H.sub.2O 25.25 TDS 15%

(17) Crude oils used in this study have the compositions and densities listed in Table 4. As used herein, the terms “heavy crude” and “light crude” are as follows: heavy crude is crude oil which has less than 30% by weight of hydrocarbons having carbon chains of less than C15, and an API gravity below 30°; and light crude is crude oil which has 30% or more by weight of hydrocarbons having carbon chains less than C15, and an API gravity at or above 30°.

(18) TABLE-US-00004 TABLE 4 Composition and density of crude oils used. Density API % % % % % at 20° C., gravity, Crude oil <C15 Saturate Aromatic Resin Asphaltene g/mL °API (a) Heavy crude oils Crude H1 13.90 50.27 26.52 22.67 0.53 0.8939 26.8 Crude H2 22.13 19.78 51.02 17.11 12.09 0.9745 13.7 Crude H3 24.10 40.69 36.48 15.43 7.40 0.8920 27.1 Crude H4 28.96 18.33 44.55 23.79 13.33 0.9700 14.4 (b) Light crude oils Crude L1 55.46 60.13 32.29 7.35 0.22 0.8334 38.1 Crude L2 42.28 45.57 41.62 12.81 0.00 0.8549 34.0

Experimental Methods

Sample Preparation

(19) Stock solutions of 10% of each of the anionic sulfates and the non-ionic alcohol ethoxylates (AE's) in nanopure water were prepared prior to formulation.

(20) The formulations were subsequently prepared to the desired concentration of each surfactant from the stock solutions in each of the brines listed in Table 3. The concentration of the anionic sulfate in the formulation preferably ranges from 0.15 to 0.4 wt %. The concentration of the non-ionicethoxylate in the formulation ranges preferably from 0.1 to 0.35 wt %. The total surfactant concentration in the formulation was kept constant at 0.5 wt %.

Aqueous Stability Test

(21) The prepared formulations were placed in the oven at temperatures ranging from 25 to 70° C. for a period of at least 3 months. The formulations were continuously visually inspected for any phase separation (PS), cloudiness and precipitation. Formulations that showed signs of phase separation, cloudiness, or precipitation failed the aqueous stability test. Formulations that remained clear over time passed the aqueous stability test.

(22) Unless otherwise indicated, throughout this application the performance of aqueous stability tests followed the process set forth above.

Dynamic IFT Measurement

(23) Formulations that passed the aqueous stability test were measured for dynamic IFT against each of the crude oils from Table 4 at different temperatures using DataPhysics Interfacial Tensiometer. The capillary tube was filled with ˜2 mL of the denser phase, which was the surfactant formulation. An amount of 2-3 μL of oil, which is the less dense phase, was injected into the capillary tube filled with the surfactant solution and formed a droplet. The capillary tube was then inserted into the spinning compartment of the instrument. As the tube was spun, the oil droplet started stretching and the IFT value was generated. The IFT gradually changed at first and became constant after 15 minutes in most cases. Once the IFT value remained constant, it was recorded.

(24) Unless otherwise indicated, throughout this application the measurement of dynamic IFT followed the process set forth above.

Results

(25) Formulations with only anionic surfactants, namely the salts of alkyl propoxy ethoxy sulfates described in this invention, prepared in the brines listed in Table 3, did not pass the aqueous stability over the temperature range of 25-70° C. Therefore, a co-surfactant (non-ionic surfactant) was required to improve the aqueous stability of the anionic sulfate surfactants.

EXPERIMENT 1: Aqueous Stability Tests (Formulations of Anionic and Non-Ionic Surfactants)

(26) The aqueous stabilities of the formulations of an anionic surfactant, namely a MIPA salt of C12/C13-8 PO sulfate (0.4 wt %) and various non-ionic alcohol ethoxylates (AE) as co-surfactant (0.1 wt %) were determined over the temperature ranges of 25-60° C. in 4% TDS brine. The results are shown in Table 5.

(27) TABLE-US-00005 TABLE 5 Aqueous stability of 0.4 wt % MIPA salt of ISALCHEM C12/C13 − 8PO sul- fate and 0.1 wt % co-surfactant in 4% TDS brine (PS/cloudy = the solution phase separates and becomes cloudy upon mixing). Alcohol Alcohol chain Alcohol Co-surfactant name length structure # EO 25° C. 40° C. 60° C. Surfactant 1 ALFOL20+ C20+ linear, heavy chain 50 clear clear clear Surfactant 2 ISOFOL 20 C20 2-alkyl 50 clear clear clear branched, long chain Surfactant 3 ISOFOL 24 C24 2-alkyl 50 clear clear clear branched, heavy chain Surfactant 4 ALFOL20+ C20+ linear, heavy chain 25 clear clear clear Surfactant 5 iTDA C13 branched, medium chain 50 clear clear clear (isotride-canol) Surfactant 6 ISOFOL 12 C12 2-alkyl 50 clear clear clear branched, medium chain Surfactant 7 ALFOL 6 C6 linear, short chain 50 clear clear PS/cloudy Surfactant 8 iTDA C13 branched, medium chain 30 clear clear PS/cloudy (isotride-canol) Surfactant 9 ISOFOL 12 C12 2-alkyl 29 clear clear PS/cloudy branched, medium chain Surfactant 10 ALFOL 6 C6 linear, short chain 15 clear clear PS/cloudy Surfactant 11 iTDA C13 branched, medium chain 8 clear cloudy PS/cloudy (isotride-canol)

(28) As can be seen in Table 5, formulations with short chain AE's (C6) containing 15 and 50 EO units (Surfactant 7 and Surfactant 10) as co-surfactant, did not pass the aqueous stability test at 60° C. Formulations with medium chain AE's (C12/C13) containing 30 EO units and less (Surfactant 8, Surfactant 9 and Surfactant 10), also did not pass the aqueous stability test at 60° C. Formulations using medium chain AE's containing 50 EO units, and long, heavy chain AE's containing 25 EO units and higher, pass the aqueous stability test over the entire temperature range.

EXPERIMENT 2: Determination of Dynamic Interfacial Tension (IFT) Values (Various Crudes)

(29) The dynamic IFT's of the formulations using Surfactant 1 to Surfactant 6 (since they passed the aqueous stability test up to 70° C.) were measured against the various crude oils at different temperatures.

Experiment 2.1

(30) The dynamic IFT values for formulations containing Surfactants 1-6 (0.1 wt %) together with anionic surfactant ISALCHEM C12/13-8 PO sulfate MIPA salt (0.4 wt %) were determined in heavy crude oil (H1) over the temperature range of 25-60° C. (4% TDS brine). Results are shown in FIG. 1.

(31) Formulations using long, heavy chain co-surfactants with 25 and 50 EO units (Surfactant 1 to Surfactant 4), produce ultralow IFT (<0.01 mN/m) for the heavy crude oil (Crude H1) at all temperatures from 25 to 60° C. Formulations using medium chain co-surfactants with 50 EO units (Surfactant 5 and Surfactant 6) were not able to produce ultralow IFT for Crude H1, as seen in FIG. 1.

Experiment 2.2

(32) In addition, the dynamic IFT values for formulations containing Surfactants 1-6 (0.1 wt %) together with anionic surfactant ISALCHEM C12/13-8PO sulfate MIPA salt (0.4 wt %) were determined in light crude oil (L1) over the temperature range of 25-60° C. (4% TDS brine). Results are shown in FIG. 2.

(33) Only Surfactant 5 and Surfactant 6 (medium chain co-surfactants with 50 EO units) were able to produce ultralow IFT for the light crude (Crude L1) over the whole range of temperature as seen in FIG. 2.

Experiment 2.3

(34) In order to further validate the results obtained in Experiments 2.1 and 2.2, the dynamic IFT values for formulations containing Surfactants 1, 4, 5 and 6 (0.1 wt %) together with anionic surfactant ISALCHEM 012/13-8PO sulfate MIPA salt (0.4 wt %) were determined in various crude oils over the temperature range of 25-60° C. (4% TDS brine). Results are shown in FIGS. 3-5.

(35) The IFT results in FIGS. 3-5 further validate the findings that Surfactant 1 to Surfactant 4 were able to produce ultralow IFT for heavy crude oils and Surfactant 5 and Surfactant 6 were able to produce ultralow IFT for light crude oils over the range of temperatures 25-60° C.

EXPERIMENT 3: Effect of Anionic vs Non-Ionic Surfactant Blending Ratios on Aqueous Stability and IFT Values

(36) In order to demonstrate the effect of various blending ratios between the anionic and non-ionic surfactants on the aqueous stability and IFT values, two anionic surfactants, namely MIPA salts of ISALCHEM C12/13-8PO sulfate and ISOFOL 016-8PO sulfate, together with non-ionic Surfactant 1, were determined.

Experiment 3.1: Aqueous Stability Tests

(37) The aqueous stability of the formulation of both anionic surfactant ISALCHEM C12/13-8PO sulfate (MIPA salt) and Surfactant 1 (various ratios) were determined in a brine solution of 4% TDS at temperatures 25-70° C. Results are shown in Table 6.

(38) TABLE-US-00006 TABLE 6 Aqueous stability of blends of anionic sulfate and non-ionic ethoxylated alcohol at various surfactant ratios in 4% TDS brine at up to 70° C. Anionic sulfate, Surfactant wt % 1, wt % 25° C. 40° C. 60° C. 70° C. (a) Anionic sulfate is MIPA salt of ISALCHEM C12/C13 - 8PO sulfate 0.5 0 Cloudy cloudy PS/cloudy PS/cloudy 0.45 0.05 Clear clear PS/cloudy PS/cloudy 0.4 0.1 Clear clear Clear Clear 0.35 0.15 Clear clear Clear Clear 0.3 0.2 Clear clear Clear Clear 0.25 0.25 Clear clear Clear Clear 0.2 0.3 Clear clear Clear Clear 0.15 0.35 Clear clear Clear Clear 0.1 0.4 Clear clear Clear Clear (b) Anionic sulfate is MIPA salt of ISOFOL C16 - 8PO sulfate 0.5 0 Cloudy cloudy PS/cloudy PS/cloudy 0.45 0.05 Clear clear PS/cloudy PS/cloudy 0.4 0.1 Clear clear Clear clear 0.35 0.15 Clear clear Clear clear 0.3 0.2 Clear clear Clear clear 0.25 0.25 Clear clear Clear clear 0.2 0.3 Clear clear Clear clear 0.15 0.35 Clear clear Clear clear 0.1 0.4 Clear clear Clear clear

(39) Without the co-surfactant, the anionic sulfate solution at 0.5 wt % concentration in 4% TDS brine was cloudy at 25° C. up to 70° C. The anionic/non-ionic surfactant blends were only clear when the concentration of the non-ionic surfactant was 0.1 wt % or higher with the total surfactant concentration being 0.5 wt %.

Experiment 3.2: Determination of IFT Values for Various Surfactant Ratios in Heavy Crude

(40) The dynamic IFT values in heavy crude (crude H1) of the formulation of both anionic surfactant ISALCHEM C12/13-8PO sulfate (MIPA salt) and Surfactant 1 (various ratios) were determined in a brine solution of 4% TDS at 25° C. Results are shown in FIG. 6.

(41) FIG. 6 shows that the dynamic IFT for Crude H1 oil was affected by the anionic/non-ionic ratio. For MIPA salt of ISALCHEM C12/C13-8PO sulfate, the IFT was lowest at anionic/non-ionic ratio of 0.4 wt %/0.1 wt % while it was 0.35 wt %/0.15 wt % for MIPA salt of ISOFOL C16-8PO sulfate.

Experiment 3.3: IFT Values in a High TDS % Brine Solution in Various Crudes

(42) a) The dynamic IFT values for a blend of 0.25 wt % anionic surfactant (ISALCHEM 012/013-4PO sulfate, MIPA salt)/0.25 wt % non-ionic surfactant (Surfactant 1) were determined with various crudes at temperatures 25 and 40° C., using a brine solution of 11.8% TDS. Results are shown in FIG. 7.

(43) FIG. 7 demonstrates that the formulation of the MIPA salt of ISALCHEM C12/13-4PO (0.25 wt %) and Surfactant 1 (0.25 wt %) in 11.8% TDS brine for various crude oils at 25 and 40° C. was able to produce ultralow IFT values.

(44) b) The dynamic IFT values for a blend of 0.25 wt % anionic surfactant (ISALCHEM C12/C13-4PO sulfate, MIPA salt) and various non-ionic surfactants (Surfactant 1, 5 and 6—all 0.25 wt %) were determined with heavy crudes (Crude H1 and H2) at temperatures 40° C., using a brine solution of 11.8% TDS. Results are shown in FIG. 8.

(45) Non-ionic Surfactant 1 produced an ultra-low IFT value at the conditions described above.

(46) In addition to the detailed experiments described above, the invention was further exemplified over an extended range of experimental conditions for a variety of combinations of surfactants/ratios of surfactants in heavy and light crudes. The results for various anionic surfactants combined with Surfactant 1 (specifically ALFOL C20+50EO) are summarised in Table 7.1 below (Exp. 4-9). Table 7.2 further illustrates variations of surfactant combinations and different conditions (Exp. 10-15). Aqueous stabilities and dynamic interfacial tensions were determined according to the general procedures described earlier.

(47) TABLE-US-00007 TABLE 7.1 Summarised results for various anionic surfactants combined with Surfactant 1 (specifically ALFOL C20.sup.+ 50EO), illustrated over an extended range of experimental conditions in heavy and light crude AQUEOUS ANIONIC NON-IONIC STABILITY DYNAMIC INTERFACIAL TENSION SURFACTANT SURFACTANT TDS Appearance Heavy Crude (H1) Light Crude (L1) EXP Name Wt % Name Wt % (%) 25° C. 40° C. 70° C. 25° C. 40° C. 70° C. 25° C. 40° C. 70° C. 4 Ziegler 0.40 Surfactant 1: 0.10 11.8 clear clear 0.0015 0.0432 C10-4PO-1EO 0.35 50EO 0.15 clear clear 0.0011 0.0364 sulfate, Na salt 5 ISOFOL 0.25 Surfactant 1: 0.25  4.0 clear clear 0.3000 0.0015 C12-15PO 0.15 50EO 0.35 clear clear 0.0930 0.0100 sulfate, MIPA salt 6 SAFOL 0.40 Surfactant 1: 0.10 4.0 clear clear 0.0016 0.0127 C1213-13PO-3EO 0.25 50EO 0.25 clear clear 0.0550 0.0028 sulfate, MIPA salt 7 SAFOL 0.30 Surfactant 1: 0.20 11.8 clear clear 0.0027 0.0136 C1213-7PO-3EO 0.25 50EO 0.25 clear clear 0.0037 — sulfate, MIPA salt 0.20 0.30 clear clear 0.0170 0.0048 8 ISALCHEM 0.35 Surfactant 1: 0.15 11.8 clear 0.0011 0.0364 C1213-4PO 0.25 50EO 0.25 clear 0.0089 0.0162 sulfate, Na salt 0.20 0.30 clear 0.0031 0.0196 0.15 0.35 clear 0.0153 0.0060 9 ISALCHEM 0.20 Surfactant 1: 0.30 15.0 clear clear 0.0052 0.0059 0.0441 0.0145 C1213-4PO 0.15 50EO 0.35 clear clear 0.0354 0.0135 0.0095 0.0095 sulfate, Na salt

(48) TABLE-US-00008 TABLE 7.2 Summarised results for various anionic surfactants combined with various non-ionic surfactants, illustrated over an extended range of experimental conditions in heavy and light crude ANIONIC NON-IONIC AQUEOUS STABILITY DYNAMIC INTERFACIAL TENSION SURFACTANT SURFACTANT TDS Appearance Heavy Crude (H1) Light Crude (L1) EXP Name Wt % Name Wt % (%) 25° C. 40° C. 70° C. 25° C. 40° C. 70° C. 25° C. 40° C. 70° C. 10 ISALCHEM 0.20 Surfactant 12: 0.30  4.0 clear clear 0.031  0.0025 C1213-8PO 0.15 50EO 0.35 clear clear 0.0426 0.0030 sulfate, Na salt cloud 11 ISALCHEM 0.35 Surfactant 12: 0.15 11.8 clear 0.0352 0.0030 C1213-4PO 0.30 50EO 0.20 clear 0.0853 0.0190 sulfate, Na salt 12 ISALCHEM 0.30 Surfactant 1: 0.20  4.0 clear clear clear 0.0123 0.0060 0.0049 0.0110 0.0083 0.0017 C1213-8PO 0.25 75EO 0.25 clear clear clear 0.0144 0.0700 0.0090 0.0132 sulfate, MIPA salt 0.15 0.35 clear clear clear 13 ISALCHEM 0.25 Surfactant 1: 0.25 11.8 clear clear clear 0.2378 0.0022 0.0400 0.0175 0.0080 C1213-4PO 0.20 75EO 0.30 clear 0.0974 0.0070 sulfate, MIPA salt 0.15 0.35 0.0170 14 ISALCHEM 0.20 Surfactant 1: 0.30 11.8 clear clear clear 0.0285 0.0030 0.0268 0.0069 0.0074 0.0080 C1213-4PO 0.15 100EO 0.35 clear 0.0168 0.0065 sulfate, MIPA salt 15 ISALCHEM 0.35 Surfactant 1: 0.15  4.0 clear clear clear 0.0118 0.0010 0.0270 0.0097 0.0142 0.0036 C1213-8PO 0.25 20EO 0.25 clear clear 0.0080 0.0590 0.0020 sulfate, MIPA salt 0.20 0.30

(49) Tables 7.1 and 7.2 illustrate the superior performance of the invention's surfactant formulations, specifically with regard to aqueous stability and ultralow IFT values, obtained over a wide range of temperatures, salinities and concentrations.

REFERENCES

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