GB2116966A

GB2116966A - Aqueous compositions of N-oxyalkylated quaternary ammonium salt surfactants

Info

Publication number: GB2116966A
Application number: GB08304830A
Authority: GB
Inventors: Ian Charles Callaghan; Rhianydd Mary Gordon
Original assignee: BP PLC
Current assignee: BP PLC
Priority date: 1982-02-26
Filing date: 1983-02-22
Publication date: 1983-10-05
Also published as: GB8304830D0; GB2116966B

Abstract

A surfactant composition comprises an aqueous dispersion of a surfactant containing in its molecule an oxyalkylene chain and one or more quaternary nitrogen atoms. The composition is suitable for modifying the wettability of an underground oil-bearing formation and may be used for enhanced oil recovery or injectivity improvement.

Description

SPECIFICATION Compositions suitable for modifying wettability and their use This invention relates to surfactant compositions suitable for use in the recovery of crude oil, in particular to surfactant compositions suitable for modifying the wettability of underground formations, and also to a method for employing same.

The use of surfactant compositions to assist in the recovery of crude oil from an underground formation has been previously proposed and several surfactants have been described which modify the wettability of the underground formation.

An improved surfactant composition has now been invented which has improved wetting characteristics compared with those of the prior art.

According to the present invention there is provided a surfactant composition suitable for modifying the wettability of an underground formation which composition comprises an aqueous dispersion of a surfactant compound containing in its molecule an oxyalkylene chain and one or more quaternary nitrogen atoms.

Preferred surfactant compounds are those of formula: X R33 N-R- (ORlJn-HR23 X wherein R is an alkylene group containing 2 to 6 carbon atoms,

R2 and R3 are alkyl or polyalkyleneoxy groups containing 1 to 8 carbon atoms, n is an integer from 1 to 20 and Xis an anion, preferably a halide; or of formula

wherein R4 is an alkylene group containing 1 to 6 carbon atoms,

R6 and R7 are alkyl groups containing 1 to 8 carbon atoms, m is an integer from 1 to 20 and Y is an anion, preferably a halide.

Surfactant compounds which are particularly convenient are those containing two quaternary nitrogen atoms with a polyoxyalkylene chain between them. Alternatively compounds containing only one quaternary nitrogen atom may be used. In either case one or both of the nitrogen atoms can be in a ring, for example a morpholine ring.

The aqueous component of the dispersion is suitably sea water where this is readily available.

The pH of the dispersion is preferably less than 7. Since sea water is usually slightly alkaline, it should be acidified when used as the aqueous component.

The concentration of surfactant in the dispersion is suitably in the range 0.01 to 1.0% by weight.

According to another aspect of the present invention, there is provided a method for treating a formation either to maintain its water wettability in the presence of crude oil or modify its condition to a water wettable state in the presence of crude oil which method comprises contacting the formation with a surfactant composition as hereinbefore described.

The method may involve a flooding operation commonly referred to as enhanced oil recovery or a more localised well treatment, for example to improve the injectivity of a water injection well.

The invention is illustrated by the following Examples.

PREPARATION 1 Reaction ofpolyethylene glycol halides with trimethylamine A solution of polyoxyethylene dichloride (av.m.w. 637, 18g, 0.03 mol) in dry ethanol (50 ml) was treated with a 33% solution oftrimethylamine in ethanol (10.1 5g, 0.06 mol) and the mixture heated at refluxfor 70h.

A further quantity of trimethylamine soiution (5.07g, 0.03 mol) was added after 24h. The cooled reaction mixture was evaporated under reduced pressure and the residual yellow liquid treated with ether. The solvents were evaporated and the hygroscopic residue freeze dried, 8.2g. (NMR analysis suggested that the product was approximately 2/3 quaternised).

The reaction may be illustrated thus:

n=13.2 Compound (A) PREPARATION 2 Reaction of tetramethyl(ethylenediamine) with halo gena ted methoxypolyethylene glycols A mixture of chloro-methoxypolyethylene glycol (av.m.w. 368, lOg, 0.027 mol) and tetramethylethylene diamine (1.58g, 0.014 mol) in dry acetone (50 ml) was heated at refluxfor 48h. The precipitated quaternary salt was filtered, washed with dry ether and dried in vacuo. (2.5g, approx 15%). (NMR confirms the salt formation).

The reaction may be illustrated thus:

n=1.2 Compound (B) PREPARATION 3 Reaction ofpolyoxypropylene amine with methyl iodide A mixture of a polyoxypropylene amine solid under the Trade Name Jeffamine D-230 (10g, 0.04 mol), sodium bicarbonate (21 .67g, 0.26 mol), methyl iodide (36.62g, 0.26 mol) and methanol (100 ml) was heated under reflux with stirring for 72h. Methyl iodide (9.1 6g) was added after 24 and 48h; The total amount of methyl iodide used was about 0.39 mol. The reaction mixture was evaporated to dryness under reduced pressure and the residue extracted with boiling chloroform (3 x 100 ml). The combined extracts were evaporated under reduced pressure and the residue freeze dried. (5.8g, 23%). (NMR confirmed the product structure).

The reaction may be illustrated thus:

n=2.6 Compound (C) Example 1 Solutions of the compounds of formulae (A), (B) and (C) prepared as described above were made up with acid adjusted sea water (pH 6.5 - adjusted with HCI) to a concentration of 0.2% by weight.

Forties separator sand (MeOH/toluene extracted) in size fraction < 500 micron was mixed with excess surfactant at 96"C for a minimum of 18 hours. The sand was then filtered with hot (96"C) distilled water several times until no foaming existed; and the sand was then dried in an oven.

Wetting test Several grains were placed in a bottle and the sea water solution of surfactant (pH 6.5) added. The sand was contacted with a drop of Forties Oil injected from a micrometer syringe and the oil wetting behaviour of the sand in the aqueous environment oil was observed and recorded.

The qualitative results were ranged according to the scale: 1 = Grains not attached to the oil drop 2 = Grains very weakly attached - removed by shaking 3 = Grains moderately attached - removed by shaking 4 = Grains strongly attached - removed by shaking 5 = Grains attached but not removed by shaking For comparison the wetting test was repeated but in the absence of surfactant employing the sea water, sand and oil only.

The results were as follows:

Structure Wetting by oil Cle ClO Me3N-ICH2-CH2-0}n CH2-CH2-NMe3 Me3 fl:13.2 Compound (A) CLOMe Me CIO 1e 133 Me-N1 -C112-C112-N Nl-Me n=7 2 ICH2-CH2-O)n-CN3 (CHZ-CHZ-O),-EH3 Compound 18) ie Me3N-CN-(112-(O CH-CH),--N Me3 n=2.6 CH3 CH3 Compound (C) No surfactant | 5 *Only 67% conversion to quaternary salt These results demonstrate that in the absence of the surfactant the sand grains which are normally water wettable quickly take on an oil wet character, but in the presence of the surfactant the surface of the sand can retain its water wettability in the presence of the crude oil. Also demonstrated is that a surfactant with a polyethyleneoxy chain between its nitrogen atoms is more effective than one with the polyethyleneoxy chains attached to the nitrogen atoms as side chains.

Claims

1. A surfactant composition suitable for modifying the wettability of an underground oil-bearing formation, the composition comprising an aqueous dispersion of a surfactant containing in its molecule an oxyalkylene chain and one or more quaternary nitrogen atoms.

2. A surfactant composition according to claim 1 wherein the surfactant is of formula X R33N-R-tSRlXn-NR23 X wherein R is an alkylene group containing 2 to 6 carbon atoms,

R2 and R3 are alkyl or polyalkyleneoxy groups containing 1 to 8 carbon atoms, n is an integer from 1 to 20 and Xis an anion.

3. A surfactant composition according to claim 1 wherein the surfactants is of formula

wherein R4 is an alkylene group containing 1 to 6 carbon atoms,

R6 and R7 are alkyl groups containing 1 to 8 carbon atoms, m is an integer from 1 to 20 and Y is an anion.

4. A surfactant composition according to any of the preceding claims wherein the anion is a halide.

5. A surfactant composition according to any of the preceding claims wherein the aqueous component of the dispersion is sea water.

6. A surfactant composition according to any on the preceding claims wherein the concentration of surfactant in the dispersion is in the range 0.01 to 1.0% by weight.

7. A surfactant composition according to any of the preceding claims wherein the pH of the composition is less than 7.0.

8. A method for treating a formation either to maintain its water wettability in the presence of crude oil or to modify its condition to a water wettable state in the presence of crude oil which method comprises contacting the formation with a surfactant composition according to any of the preceding claims.

9. A surfactant composition as hereinbefore described with reference to Example 1.