OA18259A - Ultra-high salinity surfactant formulation. - Google Patents

Abstract

Methods of enhanced oil recovery are disclosed that use compositions including an alkyl polyether anionic surfactant having the general structure R1JA, wherein R1 is a C8-C18 primary or secondary radical group, J is a random, block, alternating, or alternating block polyether segment having the structure [(PO)x(EO)y(BO)z], wherein x is 4 to 18, y is 0 to 20, and z is 0 to 5, and A is an anionic group; a co-surfactant having the general structure (R2 )q(B)Ph-L-Ph(D)(R3 )r, wherein R2 and R3 are each, independently in each instance, a C8-C24 linear or branched, primary or secondary alkyl group, B and D are anionic groups, q is 1 to 3, r is 1 to 3, and L is O or CH2; and an alkoxy alcohol.

Description

ULTRA-HIGH SALINITY SURFACTANT FORMULATION

FIELD [0001] Embodiments of the présent disclosure generally relate to an enhanced oil recovery well injection composition, using such a composition for enhanced recovery of an oil well, and methods of making the composition.

BACKGROUND [0002] Enhanced oil recovery is a process wherein an oil well that has suffered a décliné in production due to déplétion of the resources in the well and loss of réservoir pressure. Candidates for enhanced recovery are typically wells that hâve been in production for some time so that a significant volume of resources hâve been extracted from the well. In one type of enhanced oil recovery, a fluid is pumped into a réservoir to contact oil that does not flow at réservoir pressure. The fluid is typically designed to disperse the oil, reduce adhesion of the oil to réservoir structures, or otherwise ease movement of the oil out of the réservoir to the surface.

[0003] Many fluids used for enhanced recovery include surfactants and solvents. Such materials are typically blended with water obtained from réservoir structures to form a well injection fluid. The water is usually salty, making mixing with the solvents and surfactants challenging. In wells with high salinity brines, extractors often hâve to resort to expensive and time-consuming water treatment to reduce salinity and/or minerai hardness ofthe water. Thus, there is a need for well injection materials that are stable when mixed with high salinity well brines.

DETAILED DESCRIPTION [0004] A composition is disclosed that includes an alkyl polyether anionic surfactant having the general structure R¹ JA, wherein R¹ is a C₈-C₁₈ primary or secondary radical group, J is a random, block, alternating, or alternating block polyether segment having the structure [(PO)_x(EO)_y(BO)_z], wherein x is 4 to 18, y is 0 to 20, and z is 0 to 5, and A is an anionic group. In this disclosure, “PO stands for “propylene oxide”, ΈΟ stands for “ethylene oxide, and “BO stands for butylène oxide”. R¹ may be a C6-C20 linear, branched, cyclic, or alkyl-cyclic radical, such as a C8-Ci8 primary or secondary radical group, a C10-C15 primary or secondary radical group, for example a C10 radical group or a C13 radical group. Alternately, R¹ may be a C8-Cio alkyl or dialkyl phénol group. The alkyl polyether anionic surfactant generally has a hydrophobie portion that is compatible with a variety of fossil fluids for use in a variety of réservoirs. In some cases, z is 0 and A is SO₃Na. A may also be CH2CH2SO3Na, CH2COONa, or PO3Na. The surfactant may be a mixture of molécules having different proportions of monomers. For example, if a mixture of alkylene oxides is used to make the polyether portion, local reaction conditions may lead to different combinations of monomers in the individual molécules. In such cases, the surfactant may be described by the formula above, where x, y, and z may hâve fractional values to represent the “average” molécule of the blend.

[0005] The surfactant is typically built by reacting an alcohol with alkylene oxides to form the alkyl polyether, and then reacting the alkyl polyether with an acid to attach the anionic portion. The alcohol may be a C₈-C₁₈, such as C-10-C15, for example C_1o or Ci₃, primary or secondary, linear or branched, aliphatic or aromatic molécule. In some cases, the alcohol may be a C₈-C-io alkyl or dialkyl phénol. Mixtures of alcohols may be used.

[0006] The alkylene oxide, or a mixture of alkylene oxides, is added to the alcohol(s) to form a reaction mixture that yields the polyether. The alkylene oxides typically include PO, and may include EO, and BO. The molar ratio of alkylene oxides in the surfactant generally follows the molar ratio of alkylene oxides in the reaction mixture. The alkylation reaction may be performed in batch mode or continuous flow. The alkyl polyether portion ofthe surfactant may be random, block, pseudo-block (i.e. identifiable blocks of different random monomer mixtures), or alternating block, and the blocks may be any length. Blocks may be formed by sequentially adding different alkylene oxides, or mixtures thereof, to the reaction mixture, reacting each mixture to completion, and removing unreacted monomers before adding the next alkylene oxide or mixture. The reactions may be performed in liquid or gas phase. Reaction températures can be, but are not limited to, between 120° and 160°C depending 5 on which oxide is being reacted. At these températures reactor vessels capable of handling high pressures may be used. The choice of catalyst will dépend on the starting radical and the alkyloxide being used. In some cases, a strong base such as Potassium Hydroxide is used. Other options for catalysts include strong acids and coordination catalysts. The catalyst may be introduced as a solution in 10 a solvent, and the solvent may be removed before the alkyl oxides are introduced into the reactor. Depending on the molecular weight of the alcohol used to start the alkyl polyether portion, between 230_Daltons and 2400 Daltons are added to the alcohol to form an alkyl polyether mixture with alkyl polyether molécules ranging in molecular weight from about 350_to about 2700.

[0007] Residual alkylene oxide monomers may be removed, for example by évaporation and stripping with inert gas, for example nitrogen, before attaching the anionic portion. The unreacted monomers, and any solvents used for the reaction or for removing unreacted monomers, may be recycled. An acid is added to the alkyl polyether to attach the anionic portion. The alkyl polyether 20 may be dissolved in a solvent prior to adding the acid, if desired, to facilitate mixing of the reactants, and a solvent may also be included with the acid.

Sulfuric acid may be used to add a sulfate anion (SO₃’). Carboxylate, phosphate, and ether sulfonate ions may also be used.

[0008] The anionic surfactant may be stabilized as a sait. After reaction with acid to attach the anionic portion, excess acid may be neutralized, and the surfactant stabilized, by adding a base such as sodium hydroxide, or another alkali métal hydroxide such as potassium hydroxide, ammonium hydroxide, or an organic amine. An example ofthe primary surfactant is a sodium sait of tridecyl alcohol with 8 PO units and 2 EO units added to the average molécule and capped with a sulfate anion.

[0009] A co-surfactant may be included in the composition to broaden the range of réservoirs in which the composition is an effective hydrocarbon extraction aid. The co-surfactant may hâve the general structure (R²)q(B)Ph-LPh(D)(R³)r wherein R² and R³ are each, independently in each instance, a C8-C24 linear or branched, primary or secondary alkyl group, B and D are anionic groups, q is 1 to 3, r is 1 to 3, and L is O or CH2. In this disclosure, “Ph” represents a phenyl radical. The co-surfactant may be constructed by any etherforming reaction, such as acid catalyzed phénol condensation, base catalyzed halide/alcohol élimination (e.g. Williamson reaction) , or epoxide ring-opening. In some embodiments, R² and R³ may be secondary alkyl groups bonded to the phenyl group at the number two carbon atom of the alkyl group. R² and R³ may be in the meta and/or para positions, relative to L, in some embodiments. B and D may be at any position relative to L and R², or L and R³, respectively. The cosurfactant may be a disodium dialkylarylsulfonate ether. B and D may each be SO3. The anionic co-surfactant may be stabilized as a sait, for example a sodium or potassium sait.

[0010] Examples of co-surfactants that may be used include disodium salts of decyl phenoxybenzenedisulfonic acid, di-decyl phenoxybenzenedisulfonic acid, dodecyl phenoxybenzenedisulfonic acid, di- dodecyl phenoxybenzenedisulfonic acid, and hexyl phenoxybenzenedisulfonic acid.

[0011] An alkoxy alcohol may be included in the composition to adjust flow and pénétration characteristics ofthe composition. The alkoxy alcohol may hâve the general structure R⁴[(PO)m(EO)n(BO)o]OH, wherein R⁴ is a C-ι to C6 linear, branched, cycloaliphatic, or aromatic hydrocarbyl group, m is 0 to 3, n is 1 to 10, and o is 0 to 3. Exampies include alkoxylated n-butanol, i-butanol, and hexanol. An alkoxy alcohol made from n-butanol with two EO groups added is available as

SURFONIC® L4-2 from the Performance Products Division of Huntsman, Corp., located in The Woodlands, Texas. Other SURFONIC® products that may be used include SURFONIC® L4-1, SURFONIC® L4-3, SURFONIC® IBA-3,

SURFONIC® IBA-5, SURFONIC® L6-6, SURFONIC® L6-8, and SURFONIC® L610.

[0012] In some cases, a water soluble polymer may be included in the composition to improve the sweep efficiency of the composition as it moves through the réservoir. The polymer prevents viscous fingering ofthe composition as it moves through the réservoir. Partially hydrogenated polyacrylamide polymers like the Flopaam sériés available from SNF are useful in this application. The polymers may also include spécial comonomers like AMPS that help impart extra brine and hardness tolérance.

[0013] The compositions described above may be added to well brines having ultra-high salinity. A composition such as that described herein may be mixed with a well brine to form an injection brine. A concentration of the primary surfactant in the injection brine may be between about 0.5 wt% and about 5 wt%, for example about 1 wt%. The co-surfactant is typically used in a weight ratio to the primary surfactant of about 0.3 to about 0.5, for example from about 0.375 to about 0.438. The co-surfactant may be use in a weight ratio to the primary surfactant of about 0.2 to 2.0. The amounts of co-surfactant and co-surfactant may dépend on salinity and température ofthe réservoir.

[0014] The components described above may be included in a water concentrate containing 75% or more of the active ingrédients described above and up to 25% water, for example 25 to 50% active ingrédients with the balance being water.

[0015] The composition above is generally useful when blended in appropriate amounts with water surfaced from oil wells. The water may be native to the réservoir, or produced water that has resulted from water flooding réservoir may be used. Such produced water is typically a brine solution with 100,000 ppm total dissolved solids or more. In some cases, the compositions described herein may be used with brines having up to 200,000 ppm total dissolved solids. Typical injection water used for water flooding oil réservoirs in the Permian Basin of Texas, for example, hâve salinities in the range of 120,000 to 200,000 ppm of dissolved solids.

[0016] A method of forming an enhanced oil recovery well injection composition is also disclosed, including forming a concentrate by mixing a water solution of a surfactant having the general structure R¹ JA defined above, with a co-surfactant having the general structure (R²)q(B)Ph-L-Ph(D)(R³)r defined above, and an alkoxy alcohol as described above; and forming an enhanced oil recovery well injection composition by mixing the concentrate with untreated well brine having total dissolved solids of about 100,000 ppm or more and hardness of about 4,000 ppm or more.

[0017] The water solution of the surfactant may be formed by mixing an alkyl polyether alcohol having the general formula R¹JOH with sulfuric acid to form an anionic surfactant and neutralizing with sodium hydroxide, or another alkali métal hydroxide such as potassium hydroxide, ammonium hydroxide, an organic amine. The co-surfactants and alkoxy alcohols described above may be added in a mixed vessel or in continuous flow using a mixing insert such as a static mixer. As above, mixtures of surfactants, co-surfactants, and alkoxy alcohols may be used, and a water soluble polymer may be added. The untreated well brine is typically pumped out ofthe well into a mixing vessel, or a tank to be fed through an in-line mixer, as described above. The finished injection composition may be stored in a tank at the well site, and may be heated or cooled to a desired température before injection into the well. Additionally, the injection composition, or any component thereof, may be blended off-site and transported to the well site for injection. For example, a concentrate made from a water solution ofthe surfactants described above, the co-surfactants described above, and the alkoxy alcohols described above, may be obtained and mixed at the well site with the untreated well brine.

[0018] An exemplary composition contains a surfactant having the structure of formula (1):

ΟδΟβΝθ (1) where x is 4 to 18, for example 8, and y is 0 to 20, for example 0.1. A fractional value here indicates that the composition contains molécules of the structure above where y is zéro, and molécules of the structure above where y is non-zero. The exemplary composition also has a co-surfactant with the structure of formula (2):

along with a co-surfactant that is an ethoxylate of butanol having the structure of formula (3):

where x is 0 to 6, and has an average value of about 2. The above components are added in the general proportions described above.

[0019] Results of using compositions as described herein mixed with some actual réservoir samples are shown below. Fluid samples from three different fields were obtained. The samples ail had ultra-high salinity injection waters, and the réservoirs had moderate température. In some cases, only a primary and cosurfactant were used. In other cases a co-surfactant was also used. For each mixture, the Windsor phase type was recorded. Windsor phase I type mixtures ⁵ feature an oil-in-water microemulsion in the aqueous phase. Windsor phase II type mixtures feature a water-in-oil microemulsion in the oil phase. These types indicate that interfacial surface tension is too high for good enhance oil recovery results. Windsor phase III type features a third phase between the oil and water phases that has dissolved hydrocarbons. This type indicates interfacial surface 10 tension is low enough for good results in enhanced oil recovery processes.

Table 1 - Field 1

Réservoir Température 30°C, Total Dissolved Solids 170,000 ppm

Mixture #	Amount in Injection Brine, wt%	Windsor Phase in Mixture
Primary Surfactant	Co-Surfactant
1	1	0.250	II
2	1	0.375	III
3	1	0.438	III
4	1	0.500	I
5	1	0.563	I
6	1	0.625	I

Table 2-Field 1

Réservoir Température 30°C, Total Dissolved Solids 170,000 ppm

Mixture #	Amoun	in Injection Brine, wt %	Windsor Phase In Mixture
Primary Surfactant	Co-Surfactant	Co-surfactant
1	1	0.360	0.200	III
2	1	0.360	0.400	III
3	1	0.360	0.600	III
4	1	0.360	0.800	III
5	1	0.450	0.200	I
6	1	0.450	0.400	I
7	1	0.450	0.600	I
8	1	0.450	0.800	I

Table 3 - Field 2

Réservoir Température 38°C, Total Dissolved Solids 120,000 ppm

Mixture #	Amount in Injection Brine, wt%	Windsor Phase in Mixture
Primary Surfactant	Co-Surfactant	Co-surfactant
1	1	0.300	0.300	III
2	1	0.400	0.300	III
3	1	0.500	0.300	III
4	1	0.300	0.400	III
5	1	0.400	0.400	III
6	1	0.500	0.400	III
7	1	0.300	0.500	III
8	1	0.400	0.500	III
9	1	0.500	0.500	III

Table 4-Field 3

Réservoir Température 38°C, Total Dissolved Solids 120,000 ppm

Mixture #	Amount in Injection Brine, wt%	Windsor Phase in Mixture
Primary Surfactant	Co-Surfactant	Co-surfactant
1	1	0.300	0.500	III
2	1	0.300	1.000	III
3	1	0.300	1.250	III
4	1	0.300	1.500	III
5	1	0.300	2.000	III

[0020] While the foregoing is directed to embodiments of the présent disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims (21)

1. A composition, comprising:

an alkyl polyether anionic surfactant having the general structure R¹ JA, wherein R¹ is a C₈-Ci₈ primary or secondary radical group, J is a random, block, alternating, or alternating block polyether segment having the structure [(PO)_x(EO)y(BO)_z], wherein x is 4 to 18, y is 0 to 20, and z is 0 to 5, and A is an anionic group;

a co-surfactant having the general structure (R²)q(B)Ph-L-Ph(D)(R³)r, wherein R² and R³ are each, independently in each instance, a C₈-C₂4 linear or branched, primary or secondary alkyl group, B and D are anionic groups, q is 1 to 3, r is 1 to 3, and L is O or CH₂; and an alkoxy alcohol.

2. The composition of claim 1, wherein the co-surfactant is a dialkylarylsulfonate ether.

3. The composition of claim 2, wherein the alkoxy alcohol has the general structure R⁴[(PO)m(EO)n(BO)0]OH, wherein R⁴ is a C-, to C6 linear, branched, cycloaliphatic, or aromatic hydrocarbyl group, m is 0 to 3, n is 1 to 10, and o is 0 to

3.

4. The composition of claim 1, wherein z is 0, L is O, and A is SO₃Na, CH2CH2SO3Na, CH2COONa, or PO3Na.

5. The composition of claim 4, wherein B and C are each SO₃Na, and the alkoxy alcohol has the general structure R⁴[(PO)m(EO)n(BO)o]OH, R⁴ is a Ci to C6 linear, branched, cycloaliphatic, or aromatic hydrocarbyl group, m is 0 to 3, n is 1 to 10, and o is 0 to 3.

6. The composition of claim 5, wherein o is 0, m is 0, and R⁴ is a linear or branched C₄ alkyl group.

• ’ ί

7. The composition of claim 6, wherein R² and R³ are each, independently in each instance, a C₈ to C₁₂ linear primary alkyl group, and q and r are each 1.

8. The composition of claim 7, wherein R¹ is a C₁₀ to C15 primary linear alkyl group.

9. The composition of claim 8, wherein J is a block polyether segment

10. The composition of claim 9, further comprising a water soluble polymer.

11. The composition of claim 1, further comprising a sait water solution having at least about 100,000 ppm total dissolved solids and at least about 4,000 ppm of alkaline earth ions.

12. The composition of claim 4, further comprising a sait water solution having at least about 100,000 ppm total dissolved solids and at least about 4,000 ppm of alkaline earth ions.

13. The composition of claim 9, further comprising a sait water solution having at least about 100,000 ppm total dissolved solids and at least about 4,000 ppm of alkaline earth ions.

14. A method of forming an enhanced oil recovery well injection composition, comprising:

forming a concentrate by mixing a water solution of a surfactant having the general structure R¹ JA, wherein R¹ is a C8-Ci8 primary or secondary radical group, J is a random, block, alternating, or alternating block polyether segment having the structure [(PO)x(EO)y(BO)zj, wherein x is 4 to 18, y is 0 to 20, and z is 0 to 5, and A is an anionic group, with a co-surfactant having the general structure (R²)q(B)Ph-LPh(D)(R³)r, wherein R² and R³ are each, independently in each instance, a C8-C₂₄ • * ’.

linear or branched, primary or secondary alkyl group, B and D are anionic groups, q is 1 to 3, r is 1 to 3, and L is O or CH₂, and an alkoxy alcohol; and forming an enhanced oil recovery well injection composition by mixing the concentrate with untreated well brine having total dissolved solids of about 100,000 ppm of more and hardness of about 4,000 ppm or more.

15. The method of claim 14, wherein the water solution of the surfactant is formed by mixing an alkyl polyether alcohol having the general formula R¹JOH with sulfuric acid to form the surfactant and neutralizing residual sulfuric acid with sodium hydroxide.

16. The method of claim 14, wherein the co-surfactant is a dialkylarylsulfonate ether, the alkoxy alcohol has the general structure R⁴[(PO)m(EO)n(BO)0]OH, R⁴ is a Ci to C6 linear, branched, cycloaliphatic, or aromatic hydrocarbyl group, m is 0 to 3, n is 1 to 10, and o is 0 to 3.

17. The method of claim 16, wherein z is 0, B and D are each SO₃Na, and the alkoxy alcohol has the general structure R⁴[(PO)m(EO)n(BO)0]OH, wherein R⁴ is a Ci to C6 linear, branched, cycloaliphatic, or aromatic hydrocarbyl group, m is 0 to 3, n is 1 to 10, and o is 0 to 3.

18. The method of claim 14, wherein z is 0, L is O, A is SO₈Na, B and D are each SO₃, the alkoxy alcohol has the general structure R⁴[(PO)m(EO)n(BO)o]OH, m is 0, n is 1 to 10, 0 is 0, R⁴ is a linear or branched C4 alkyl group, R² and R³ are each, independently in each instance, a C₈ to C-|₂ linear primary alkyl group, q and r are each 1, and J is a block polyether segment.

19. A method of enhanced oil recovery, comprising:

obtaining a concentrate comprising a water solution of a surfactant having the general structure R¹ JA, wherein R¹ is a C₈-Ci₈ primary or secondary radical group, J is a random, block, alternating, or alternating block polyether segment having the structure [(PO)_x(EO)_y(BO)_zj, wherein x is 4 to 18, y is 0 to 20, and z is 0 to 5, and A

1 X is an anionic group, a co-surfactant having the general structure (R²)_q(B)Ph-LPh(D)(R³)r, wherein R² and R³ are each, independently in each instance, a C8-C₂4 linear or branched, primary or secondary alkyl group, B and D are anionic groups, q is 1 to 3, r is 1 to 3, and L is O or CH₂, and an alkoxy alcohol;

5 forming an enhanced oil recovery well injection composition by mixing the concentrate with untreated well brine having total dissolved solids of about 100,000 ppm of more and hardness of about 4,000 ppm or more; and injecting the enhanced oil recovery well injection composition into a well.

20. The method of claim 19, wherein z is 0, L is O, A is SO₃Na, B and D are each

10 SO₃Na, the alkoxy alcohol has the general structure R⁴[(PO)m(EO)_n(BO)₀]OH, m is

0, n is 1 to 10, o is 0, R² and R³ are each, independently in each instance, a C₈ to C12 linear primary alkyl group, q and r are each 1, and J is a block polyether segment.

21. The method of claim 20, wherein the untreated well brine has total dissolved

15 solids of about 120,000 ppm or more.