WO2020000357A1

WO2020000357A1 - Surfactant composition for reducing viscosity of heavy crude oil

Info

Publication number: WO2020000357A1
Application number: PCT/CN2018/093627
Authority: WO
Inventors: Wenke MIAO; Peng Gao; Pramod D. Patil; Cheng Shen; Lixin You
Original assignee: Dow Global Technologies Llc
Priority date: 2018-06-29
Filing date: 2018-06-29
Publication date: 2020-01-02

Abstract

A surfactant composition may include a surfactant mixture, where the surfactant mixture includes water and a surfactant having 30 to 100 weight percent (wt. %) of a non-ionic surfactant of a Formula I and 70 to 0 wt. % of an anionic surfactant of a Formula II where each R is independently a C4 to C10 linear alkyl or branched alkyl; each R1 is independently a methyl or an ethyl; each m is independently an integer of 1 to 11, each n is independently an integer of 1 to 20, and X is a sulfate salt. The surfactant composition may further include a heavy crude oil mixed with the surfactant mixture.

Description

SURFACTANT COMPOSITION FOR REDUCING VISCOSITY OF HEAVY CRUDE OIL

TECHNICAL FIELD

The present disclosure relates generally to surfactants and more particularly surfactant compositions for reducing the viscosity of heavy crude oil.

BACKGROUND

Heavy crude oil is defined as an oil having an API (American Petroleum Industry) gravity of less than 20° and is viscous at lower temperature when produced from a reservoir. Heavy crude oil is comprised of large amount of saturates, aromatics, resins and asphaltene. The presence of wax in heavy crude oil can result in the formation of wax crystals, which in turn causes the heavy crude oil to have low mobility. The viscous heavy crude oil, with very high viscosity at low temperature can cause low oil recover from a reservoir. In addition, overly viscous heavy crude oil can cause flow assurance issues during transportation through pipelines especially at low temperature.

Solvents including hydrocarbons have previously been used as a diluent for heavy crude oil. However, diluting heavy crude oil with solvents can be economically challenging and can cause environmental health and safety issues. In addition, heat in conjunction with formation of emulsions have been previously used to transport heavy crude oil. However, thermal heating can be demanding on energy requirements.

Attempts to form low viscosity emulsions of heavy crude oil have had limited success due to difficulties in stabilizing the emulsions, and the demulsification of the produced fluid is also a technical challenge. As such, there continues to be a need in the art for ways of reducing the viscosity of heavy crude oil to help improve its recovery and transportation.

SUMMARY

The surfactant composition of the present disclosure helps in reducing viscosity in heavy crude oil, which can help improve its recovery and transportation. The surfactant composition includes a surfactant mixture, where the surfactant mixture includes water and a surfactant having 30 to 100 weight percent (wt. %) of a non-ionic surfactant of a Formula I:

and 0 to 70 wt. %of an anionic surfactant of a Formula II:

where each R is independently a C4 to C10 linear alkyl or branched alkyl; each R ¹ is independently a methyl or an ethyl; each m is independently an integer of 1 to 11, each n is independently an integer of 1 to 20, and X is a sulfate salt. The surfactant composition can further include a heavy crude oil mixed with the surfactant mixture. The weight percent of the surfactant is based on the total weight of the surfactant, where the non-ionic surfactant and the anionic surfactant of the surfactant total 100 wt. %.

The present disclosure also provides for a method of treating heavy crude oil comprising providing the surfactant mixture and mixing the surfactant mixture with heavy crude oil at a temperature of 5 ℃ to 100 ℃ and a pressure of 100 Kpa to 69 Mpa to produce a surfactant composition. As discussed above, the surfactant mixture can include water and a surfactant having 30 to 100 wt. %of a non-ionic surfactant of a Formula I:

and 0 to 70 wt. %of an anionic surfactant of a Formula II:

where each R is independently a C4 to C 10 linear alkyl or branched alkyl; each R ¹ is independently a methyl or an ethyl; each m is independently an integer of 1 to 11, each n is independently an integer of 1 to 20, and X is a sulfate salt. The weight percent of the surfactant is based on the total weight of the surfactant, where the non-ionic surfactant and the anionic surfactant of the surfactant total 100 wt. %.

DETAILED DESCRIPTION

Surfactant compositions are disclosed herein. Embodiments of the present disclosure provide surfactant composition including a non-ionic surfactant and an anionic surfactant, as discussed herein. The present disclosure uses a surfactant composition that contains both non-ionic surfactant and anionic surfactant for reducing the viscosity of heavy crude oil. The surfactant composition of the present disclosure can help to reduce the viscosity of heavy crude oil by “wetting” the heavy crude oil through the formation of hydrogen bonds with the gelatinous and asphaltene in the heavy crude oil. The surfactant compositions describe herein have unique functions in heavy crude oil viscosity reduction applications, which can include (a) a non-ionic/anionic surfactant system that possesses the advantages of both ionic and non-ionic surfactants, such as salinity stability, low Kraft point, high cloud point and environmental friendliness, (b) branched hydrophobic hydrocarbon chains, which provides good wettability and interaction with hydrophobic and wax like components in the heavy crude oil to help disperse the heavy crude oil into water; (c) non-ionic units to help form stronger hydrogen bonds with gelatinous and asphaltene present in the heavy crude oil, thus helping to reduce aggregation between these compounds; and (d) the sulfate groups of the anionic surfactant help provide solubility and enable better dispersions for the heavy crude oil into water.

The surfactant compositions disclosed herein can produce properties in heavy crude oil that are desirable in the transport of heavy crude oil. For instance, the surfactant compositions disclosed herein can improve, i. e. reduce, the viscosity of heavy crude oil. The surfactant compositions disclosed herein can improve the transport and recovery of heavy crude oil by reducing the viscosity of heavy crude oil.

The surfactant composition disclosed herein can include a surfactant mixture including water and a surfactant having 30 to 100 weight percent (wt. %) of a non-ionic surfactant of Formula I:

and 70 to 0 wt. %of an anionic surfactant of a Formula II:

where each R is independently a C ₄ to C ₁₀ linear alkyl or branched alkyl; each R ¹ is independently a methyl or an ethyl; each m is independently an integer of 1 to 11, each n is independently an integer of 1 to 20, and X is a sulfate salt, where the wt. %of the surfactant is based on a total weight of the surfactant, where the non-ionic surfactant and the anionic surfactant total 100 wt. %.

As noted herein, the surfactant can have 30 to 100 wt. %of the non-ionic surfactant of Formula I. All individual values and subranges from 30 to 100 wt. %are included herein and disclosed herein; for example, the non-ionic surfactant of Formula I can be present in the surfactant from a lower limit of 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %or 50 wt. %to an upper limit of 70 wt. %, 75 wt. %, 80 wt. %, 85 wt. %, 90 wt. %, or 100 wt. %. Examples of ranges for the non-ionic surfactant of Formula I in the surfactant include 30 to 100 wt. %; 50 to 100 wt. %; 60 to 95 wt. %; or 70 to 90 wt. %.

Similarly, as noted herein, the surfactant can have 0 to 70 wt. %of the anionic surfactant of Formula II. All individual values and subranges from 0 to 70 wt. %are included herein and disclosed herein; for example, the anionic surfactant of Formula II can be present in the surfactant from a lower limit of 0 wt. %, 5 wt. %, 10 wt. %, 15 wt. %, 20 wt. %, 25 wt. %or 30 wt. %to an upper limit of 50 wt. %, 55 wt. %, 60 wt. %, 65 wt. %or 70 wt. %. Examples of ranges for the anionic surfactant of Formula II in the surfactant include 0 to 70 wt. %; 0 to 50 wt. %; 5 to 60 wt. %; 10 to 65 wt. %; or 10 to 30 wt. %.

Specific examples of the wt. %for each of the compounds of Formula I and Formula II for the surfactant for the present disclosure include where the surfactant has 50 to 100 wt. %of the non-ionic surfactant of Formula I and 0 to 50 wt. %of the anionic surfactant of Formula II. Another example includes where the surfactant has 70 to 90 wt. %of the non-ionic surfactant of Formula I and 10 to 30 wt. %of the anionic surfactant of Formula II.

The surfactant represented by Formula I and Formula II includes R, where each R is independently a C ₄ to C ₁₀ linear alkyl or branched alkyl. Preferably, each R is a C ₆ to C ₁₀ linear alkyl or branched alkyl. More preferably, each R is a C ₇ to C ₉ linear alkyl or branched alkyl, where the branched alkyl is most preferred. Preferably, R is the same for both Formula I and Formula II.

Each m in Formula I and Formula II is independently an integer of 1 to 11. All individual values and subranges from 1 to 11 are included herein and disclosed herein; for example, m can be present in Formula I and Formula II from a lower limit of 1, 2, 3, 4 or 6 to an upper limit of 7, 8, 9, 10 and 11. Examples of ranges for m in Formula I and Formula II include 1 to 11; 2 to 10; 3 to 9 and 3 to 7. The most preferred range for m is from 3 to 7.

Each n in Formula I and Formula II is independently an integer of 1 to 20. All individual values and subranges from 1 to 20 are included herein and disclosed herein; for example, n can be present in Formula I and Formula II from a lower limit of 1, 2, 3, 4, 5, 6, 7, 8, 9or 10to an upper limit of 11, 12, 13, 14, 15, 16, 17, 18, 19, or20. For instance, n can include from 1 to 20, 2 to 17, 3 to 14, 3 to 11, 3 to 9, or 3 to 7. The most preferred range for n is from 3 to 7.

The surfactant represented by Formula II includes X, which provides the sulfate salt to the surfactant. Examples of X can be formed from sodium sulfate, sodium aluminum sulfate, sodium bisulfate or sodium magnesium sulfate.

The surfactant represented by Formula I and Formula II can be prepared using known equipment, reaction components, and reaction conditions. The surfactant represented by Formula I and Formula II may be obtained commercially. Examples of commercially available surfactant represented by Formula I and Formula II include, but are not limited to, DOWFAX ^TM surfactants available from The Dow Chemical Company. One preferred example of the surfactant for the present disclosure includes DOWFAX ^TM AS-801 available from The Dow Chemical Company.

The surfactant compositions disclosed herein can also further include a C ₈ to C ₂₀ sodium alpha-olefin sulfonate. The sodium alpha-olefin sulfonate can include mixtures of sodium alpha-olefin sulfonates having carbon amounts from a lower limit of C ₈, C ₉, C ₁₀, C ₁₁, C ₁₂, or C ₁₃ to an upper limit of C ₁₄, C ₁₅, C ₁₆, C ₁₇, C ₁₈, C ₁₉, or C ₂₀. For instance, the sodium alpha-olefin sulfonate can include mixtures of sodium alpha-olefin sulfonates having carbons ranging from C ₈ to C ₂₀; C ₁₂ to C ₁₄; C ₁₄ to C ₁₈; C ₁₄ to C ₁₆; or C ₁₆ to C ₁₈. The numbers indicate the average lengths of the carbon chains of the alpha olefins.

As mentioned above, the surfactant composition disclosed herein can include a surfactant mixture including water. The surfactant mixture can include water varying from fresh water to concentrated brine water. For instance, the water can be a Brine Water Composition including sodium chloride, calcium chloride, magnesium chloride, sodium hydrogen carbonate, or combinations thereof. The Brine Water Composition included in the surfactant mixture can have 0 to 30 wt. %of a salt such as sodium chloride, calcium chloride, magnesium chloride, sodium hydrogen carbonate, or combinations thereof.

The surfactant compositions disclosed herein can also include an organic solvent having a flash point greater than 60 ℃. Examples of such organic solvents include those selected from a group consisting of diethylene glycol, diethylene glycol dimethyl ether, dimethyl sulfoxide, ethylene glycol, n-methyl-2-pyrrolidione and combinations thereof. Others organic solvents are also possible.

The surfactant compositions disclosed herein can also include an ether selected from a group consisting of diethylene glycol ethyl ether, diethylene glycol n-butyl ether, ethylene glycol propyl ether, propylene glycol phenyl ether, dipropylene glycol phenyl ether and combinations thereof.

As discussed herein, the surfactant composition of the present disclosure includes the surfactant mixture and heavy crude oil, where the heavy crude oil is mixed with the surfactant mixture. Also, as previously noted the surfactant mixture includes at least the water, as discussed herein, and the surfactant, also as discussed herein. For these various embodiments, the surfactant composition of the present disclosure can have a mass ratio of heavy crude oil to surfactant mixture (heavy crude oil: surfactant mixture) of 0.1: 1 to 2.3: 1. Other examples for the mass ratio of heavy crude oil to surfactant mixture (heavy crude oil: surfactant mixture) include 0.3: 1 to 1.5: 1 and 0.5: 1 to 1: 1.

The surfactant compositions disclosed herein can have a pH range from 7 to 14 measured at a temperature of 23 ℃. For instance, the surfactant composition can have a pH of 7 to 12 when measured at a temperature of 23 ℃, a pH of 7 to 11 when measured at a temperature of 23 ℃, or a pH of 7 to 10 when measured at a temperature of 23 ℃.

The surfactant compositions disclosed herein can have a dynamic viscosity range from 500 cps to 100,000 cps. For instance, the surfactant composition can have a dynamic viscosity from 500 cps to 100,000 cps, 1000 cps to 50,000 cps, or 1000 cps to 40,000 cps. For example, the surfactant composition can have a dynamic viscosity of 16453 cps at 30 ℃, 9105 cps at 50 ℃, or 544 cps at 90 ℃. The dynamic viscosity is measured according to ASTM D7042-04.

The heavy crude oil mixed with the surfactant mixture to form the surfactant compositions disclosed herein can also have a have a total acid number ranging from 4 to 6 mg KOH/gram of heavy crude oil. For instance, the heavy crude oil mixed with the surfactant mixture can have a total acid number from 6 mgKOH/gram of heavy crude oil, 5 mgKOH/gram of heavy crude oil, or 4.17 mgKOH/gram of heavy crude oil.

The present disclosure also includes a method of treating heavy crude oil, which includes providing the surfactant mixture, as discussed herein, that includes water and the surfactant, both as discussed herein, and mixing the surfactant mixture with heavy crude oil at a temperature of 5 ℃ to 100 ℃ and a pressure of 100 Kpa to 69 Mpa to produce the surfactant composition. As previously discussed, the surfactant can have 30 to 100 wt. %of a non-ionic surfactant of Formula I

where each R is independently a C ₄ to C ₁₀ linear alkyl or branched alkyl; each R ¹ is independently a methyl or an ethyl; each m is independently an integer of 1 to 11, each n is independently an integer of 1 to 20, and 0 to 70 wt. %of an anionic surfactant of a Formula II:

where each R is independently a C ₄ to C ₁₀ linear alkyl or branched alkyl; each R ¹ is independently a methyl or an ethyl; each m is independently an integer of 1 to 11, each n is independently an integer of 1 to 20, and X is a sulfate salt, wherein a wt. %of the surfactant is based on a total weight of the surfactant, where the non-ionic surfactant and the anionic surfactant total 100 wt. %.

The method of treating heavy crude oil includes mixing the surfactant mixture and the heavy crude oil at a temperature range from 5 ℃ to 100 ℃ and a pressure of 100 Kpa to 69 Mpa to produce a surfactant composition. The method of treating heavy crude oil can include mixing the surfactant mixture and the heavy crude oil at temperatures having a lower limit of 5 ℃, 10 ℃, 20 ℃, 30 ℃, 40 ℃, or 50 ℃ to an upper limit of 60 ℃, 70 ℃, 80 ℃, 90 ℃, or 100 ℃. For instance, the surfactant mixture and heavy crude oil can mix at an operating temperature ranging from 5 ℃ to 100℃, 10 to 90 ℃, 20 to 80℃, 50℃ to 70℃, 40℃ to 70℃, or 30℃ to 70℃. Similarly, the method of treating heavy crude oil can include mixing the surfactant mixture and the heavy crude oil at a pressure having a lower limit of 100 Kpa, 100 Kpa, 500 Kpa, 1 Mpa, 2 Mpa, to an upper limit of 10 Mpa, 20 Mpa, 30 Mpa, 40 Mpa, 50 Mpa or 69 Mpa. For instance, the surfactant mixture and heavy crude oil can mix at a pressure ranging from 100 Kpa to 69 Mpa, 500 Kpa to 50 Mpa, 1 Mpa to 40 Mpa or2 Mpa to 30 Mpa. Combinations of the ranges provided for both the temperature and pressure for mixing the surfactant mixture and the heavy crude oil, as provided herein, are recognized as being possible.

Examples of the present disclosure are as follows.

Examples

In the Examples, various terms and designations for materials are used including, for instance, the following:

Surfactant “DOWFAX ^TM AS-801” (30 to 100 wt. %of a non-ionic surfactant of Formula I, wherein each R is independently a C ₄ to C ₁₀ linear alkyl or branched alkyl; each R ¹ is independently a methyl or an ethyl; each m is independently an integer of 1 to 11, each n is independently an integer of 1 to 20, and 0 to 70 wt. %of an anionic surfactant of a Formula II, wherein each R is independently a C ₄ to C ₁₀ linear alkyl or branched alkyl; each R ¹ is independently a methyl or an ethyl; each m is independently an integer of 1 to 11, each n is independently an integer of 1 to 20, and X is a sulfate salt) and surfactant mixture (surfactant and water) .

Examples 1 -5 of Table 2 were prepared in the following manner. Heavy crude oil was heated to a temperature of 90 ℃ for one week to remove the free water in heavy crude oil to produce a “dry heavy crude oil. ”

The surfactant was diluted with a Brine Water Composition (freshly prepared) according to the composition in Table 1 to produce a surfactant mixture.

For each Example in Table 1, 30 grams of dry heavy crude oil was added to 70 grams of surfactant mixture to form a surfactant composition. The surfactant composition for each Example was then heated in an oven having a temperature of either 30 ℃, 50 ℃ or 90 ℃ for one hour. After one hour each surfactant composition was removed from the oven at their respective temperature and stirred using a rectangular mixer head with perforations at a speed of 300 rpm for 2 minutes to form the emulsions in Examples 1 -5 of Table 2.

Materials

Water Composition

Table 1

The test method for the oil viscosity reduction evaluation was conducted in accordance with ASTM D341, Q/SH1020 2193-2013 and Q/SH 0055-2007. The evaluation was conducted as follows. A few drops of the emulsions in Examples 1 -5 of Table 2 were transferred onto their own respective filter paper to check the type and classify the emulsion (oil-in-water or water-in-oil) . The viscosity of Examples 1 -5 of Table 2 were measured using a BROOKFIELD DV1 viscometer, having a number 02 Spindle at a temperature of 25 ℃.

The test method for the emulsion stability test was conducted as follows. 10 mL of the emulsions in Examples 1 -5 of Table 2 were poured into their own respective vials. The vials with the emulsions of Example 1 -5 of Table 2 were heated to either 30 ℃, 50 ℃, or 90 ℃ and the separation of free water recorded.

Table 2

*Phase separation of the emulsion was observed before injecting into vials

Results

At the temperatures of 30 ℃, 50 ℃, 90 ℃ the emulsion type for the emulsions in Examples 1 -5 of Table 2 were oil-in-water emulsion for the surfactant concentration of from about 300 ppm to 3000 ppm. Oil-in-water type emulsions prevent the risk of viscosity build up and de-emulsion issues.

The data of Table 2 illustrates that Examples 1 -5 have an improved, i. e. reduced viscosity. Examples 1 -4 of Table 2 show that at temperatures of 30 ℃ and 50 ℃, the surfactant mixture has significant ability to mobilize heavy crude oil in the surfactant composition. The viscosity reduction rate reached above 94.0%, especially at 50 ℃ for the surfactant concentration of 1000 ppm (Example 3 of Table 2) and 3000 ppm (Example 4 of Table 2) . The final viscosity of the emulsions were about 50 cps for the surfactant concentration of 1000 ppm (Example 3 of Table 2) and 3000 ppm (Example 4 of Table 2) . The viscosity reduction rate dropped to 68.6%for the surfactant concentration of 1000 ppm at the temperature 90 ℃ (Example 5 of Table 2) . The viscosity reduction rate drops at 90 ℃ based on the belief that the viscosity at 90 ℃ is very low and the non-ionic surfactant properties of DOWFAX ^TM AS-801 solubility decreases at 90 ℃ due to the cloud point of non-ionic segments.

The data of Table 2 illustrates the surfactant mixture having a surfactant concentration of 1000 ppm for Examples 1, 3 and 5 reduced the heavy crude oil viscosity from 16453 ± 23 cps to 118 ± 3 (99.3 %reduction) , 9105 ± 543 cps to 56 ± 3 (99.4%reduction) , and 544 ± 14 cps to 171 ± 6 (68.6 %reduction) , respectively. Significantly, for the heavy crude oils having the highest viscosities (e.g., Examples 1 and 3) the reduction in viscosity was over 99 %using the surfactant mixture having a surfactant concentration of 1000 ppm for temperatures of 30 ℃ and 50 ℃, respectively.

Table 2 illustrates the viscosity of Examples 2, 3 and 4 tested at 50 ℃ decreases as the surfactant concentration increase. The viscosity decreases at high concentration based on the belief that more surfactant molecules work with gelatinous and asphaltene to form stronger hydrogen bonds and break the aggregates which results in heavy crude oil mobility improvement.

The stability of each Example of the surfactant composition were tested. There was 3 mL of free water for every 10 mL of oil to provide a heavy crude oil: water ratio of 7: 3 with surfactant dosed in water at various concentrations. The results seen in Table 2 show an unfavorable rapid phase separation at a surfactant concentration of 300 ppm (see Example 2) in water. However, at high temperatures, such as, temperatures of 90 ℃, (see Example 5) the free water after 24 hours was 60.0%separated. The remaining free water was left in the heavy crude oil, which can have demulsification issue. At temperatures of 30 ℃, (see Example 1) after 24 hours 85.0%of the free water was separated, however, separation was slow in the first 10 minutes. At temperatures of 50 ℃ and surfactant concentration of 3000 ppm (Example 4) , nearly all free water was separated after 24 hour and 60.0%was separated in the first 10 minutes. Showing that surfactant concentrations at 3000 ppm and temperature around 50 ℃ work well in reducing the viscosity of heavy crude oil.

When shear viscosity is applied the surfactant has excellent performance on viscosity reduction at wide range of surfactant concentrations (300 ppm to 3000 ppm) and temperatures (30 ℃, 50 ℃, 90 ℃) , especially at 50 ℃ and 1000～3000 ppm (Examples 3 -4 of Table 2) . The surfactant possesses advantages of both ionic surfactants and non-ionic surfactants.

Claims

A surfactant composition, the surfactant composition comprising:

a surfactant mixture including:

water; and

a surfactant having:

30 to 100 weight percent (wt.%) of a non-ionic surfactant of a Formula I:

0 to 70 wt.%of an anionic surfactant of a Formula II:

wherein each R is independently a C ₄ to C ₁₀ linear alkyl or branched alkyl; each R ¹ is independently a methyl or an ethyl; each m is independently an integer of 1 to 11, each n is independently an integer of 1 to 20, and X is a sulfate salt, wherein a wt.%of the surfactant is based on a total weight of the surfactant, where the non-ionic surfactant and the anionic surfactant total 100 wt.%; and

heavy crude oil mixed with the surfactant mixture.
The surfactant composition of claim 1, wherein the sulfate salt of X is formed from sodium sulfate.
The surfactant composition of any one of claims 1-2, wherein each m is independently an integer of 3 to 9 and each n is independently an integer of 3 to 9.
The surfactant composition of any one of claims 1-2, wherein each m is independently an integer of 3 to 7 and each n is independently an integer of 3 to 7.
The surfactant composition of any one of claims 1-4, further including a C ₈ to C ₂₀ sodium alpha-olefin sulfonate.
The surfactant composition of any one of claims 1-5, further including an organic solvent having a flash point greater than 60 ℃, the organic solvent selected from a group consisting of diethylene glycol, diethylene glycol dimethyl ether, dimethyl sulfoxide, ethylene glycol, n-methyl-2-pyrrolidione and combinations thereof.
The surfactant composition of any one of claims 1-6, further including an ether selected from a group consisting of diethylene glycol ethyl ether, diethylene glycol n-butyl ether, ethylene glycol propyl ether, propylene glycol phenyl ether, dipropylene glycol phenyl ether and combinations thereof.
The surfactant composition of any one of claims 1-7, wherein the surfactant has 50 to 100 wt.%of the non-ionic surfactant of Formula I and 0 to 50 wt.%of the anionic surfactant of Formula II.
The surfactant composition of any one of claims 1-7, wherein the surfactant has 70 to 90 wt.%of the non-ionic surfactant of Formula I and 10 to 30 wt.%of the anionic surfactant of Formula II.
The surfactant composition of any one of claims 1-9, wherein the surfactant composition has a mass ratio of heavy crude oil: surfactant mixture of 0.1∶1 to 2.3∶1.
The surfactant composition of any one of claims 1-9, wherein the surfactant composition has a ratio o f heavy crude oil: surfactant mixture o f 0.3∶1 to 1.5∶1.
The surfactant composition of any one of claims 1-9, wherein the surfactant composition has a ratio of heavy crude oil: surfactant mixture of 0.5∶1 to 1∶1.
The surfactant composition of any one of claims 1-12, wherein the surfactant composition has a pH of 7 to 12 measured at a temperature of 23 ℃.
The surfactant composition of any one of claims 1-12, wherein the surfactant composition has a pH of 7 to 10 measured at a temperature of 23 ℃.
A method of treating heavy crude oil, comprising:

providing a surfactant mixture including:

water; and

a surfactant having:

30 to 100 weight percent (wt.%) of a non-ionic surfactant of a Formula I:

70 to 0 wt.%of an anionic surfactant of a Formula II:

wherein each R is independently a C ₄ to C ₁₀ linear alkyl or branched alkyl; each R ¹ is independently a methyl or an ethyl; each m is independently an integer of 1 to 11, each n is independently an integer of 1 to 20, and X is a sulfate salt, wherein a wt.%of the surfactant is based on a total weight of the surfactant, where the non-ionic surfactant and the anionic surfactant total 100 wt.%; and

mixing the surfactant mixture with heavy crude oil at a temperature of 5 ℃ to 100 ℃ and a pressure of 100 Kpa to 69 Mpa to produce a surfactant composition.