Method for detecting and quantifying additives used in the enhanced recovery of oil and shale gas

Abstract

A method for the detection and quantification, in a complex aqueous fluid, of additives and water-soluble polymers used in the enhanced recovery of oil and shale gas.

Claims

1. A method for detecting additives used in the enhanced recovery of oil and shale gas, in injection water or production water, said method comprising: a. mixing a detecting solution comprising at least one lanthanide cation and optionally a chelating agent of the lanthanides, with a sample of injection water or of production water to be analysed comprising at least one additive used in the enhanced recovery of oil and shale gas, under conditions allowing complexing of the lanthanide by the additive present, b. detecting and, if appropriate, quantifying the variation in fluorescence associated with the presence of the additive in the injection water or the production water by time-resolved fluorescence, wherein the additive used in the enhanced recovery of oil and shale gas is a water-soluble polymer having a molecular weight between 1 MDa and 30 MDa.

2. The method according to claim 1, wherein the additive is selected from: polymers comprising at least one repeat unit comprising an amide bond; anionic biopolymers; cationic polymers.

3. The method according to claim 2, wherein the polymer comprising at least one repeat unit comprising an amide bond comprises a repeat unit of formula I ##STR00005## where R.sub.1 is —H or —CH.sub.3, R.sub.2 is —H or a substituted or unsubstituted C.sub.1 to C.sub.4 alkyl group, R.sub.3 is —H or a substituted or unsubstituted C.sub.1 to C.sub.4 alkyl group, or an -L-R.sub.4 group, where L is a bond or a substituted or unsubstituted C.sub.1 to C.sub.10 alkyl group, interrupted by 0, 1 or more —NR.sub.2— or —O— or —S— bonds, or a -(substituted or unsubstituted C.sub.1 to C.sub.10 alkyl)-(N.sup.+R.sub.6R.sub.7)-(substituted or unsubstituted C.sub.1 to C.sub.10 alkyl)- group with R.sub.6 and R.sub.7 which are either —H or a substituted or unsubstituted C.sub.1 to C.sub.4 alkyl group, and R.sub.4 is —H or a carboxylate group (—COO.sup.−) or a sulphonate group (—SO.sub.3.sup.−), or with optionally with a counter-ion.

4. The method according to claim 3, wherein the polymer moreover comprises a repeat unit of formula II ##STR00006## where R.sub.1 is —H or —CH.sub.3, and OR.sub.7 is O—H or O.sup.− and a counter-ion.

5. The method according to claim 3, wherein the polymer moreover comprises a repeat unit of formula III ##STR00007## where R.sub.1 is —H or —CH.sub.3, R.sub.2 is —H or a substituted or unsubstituted C.sub.1 to C.sub.4 alkyl group, L is a bond or a substituted or unsubstituted C.sub.1 to C.sub.10 alkyl group, interrupted by 0, 1 or more —NR.sub.2— or —O— or —S— bonds, or a -(substituted or unsubstituted C.sub.1 to C.sub.10 alkyl)-(N.sup.+R.sub.6R.sub.7)-(substituted or unsubstituted C.sub.1 to C.sub.10 alkyl)- group with R.sub.6 and R.sub.7 which are either —H or a substituted or unsubstituted C.sub.1 to C.sub.4 alkyl group, and R.sub.4 is —H or a carboxylate group (—COO.sup.−) or a sulphonate group (—SO.sub.3.sup.−), optionally with a counter-ion.

6. The method according to claim 3, wherein the polymer moreover comprises a repeat unit originating from the polymerization of a non-ionic monomer, the non-ionic monomer is selected from acryloyl morpholine, N-vinylcaprolactam, N-vinylpyrrolidone, N,N-dimethylacrylamide, N-ispropylacrylamide, diacetone acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyridine, hydroxybutyl vinyl ether and isoprenol.

7. The method according to claim 3, wherein the polymer moreover comprises a repeat unit comprising a hydrophobic group, of formula IV ##STR00008## where R.sub.1 is —H or —CH.sub.3, R.sub.8 and R.sub.9 are independently a substituted or unsubstituted C.sub.7 to C.sub.20 alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted -aryl-(C.sub.1 to C.sub.20 alkyl) group or substituted or unsubstituted —(C.sub.1 to C.sub.20 alkyl)-aryl group, where R.sub.8 and/or R.sub.9 are different from H.

8. The method according to claim 1, wherein the detecting solution moreover comprises at least 1 g/L of chloride ions, and a concentration of chloride ions comprised between 5 and 50 g/L.

9. The method according to claim 1, wherein the detecting solution moreover comprises at least 1 g/L of a chemical compound used in the production of buffer solution, of 4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid (HEPES) or sodium acetate.

10. The method according to claim 1, wherein the lanthanide is selected from: Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm and Yb, as well as mixtures thereof.

11. The method according to claim 1, wherein the additive is present at a concentration less than or equal to 10 ppm in the sample of injection water or of production water to be analysed.

Description

FIGURES

(1) FIG. 1 shows the calibration curve of polymer 3630 with Eu-2,5-diaminopyridine according to Example 8.

(2) FIG. 2 shows the calibration curve of polymer AN977 with Eu-2,5-diaminopyridine according to Example 9.

(3) FIG. 3 shows the calibration curve of polymer AN125 with Eu-2,5-diaminopyridine according to Example 10.

(4) The present invention will be better understood in light of the following non-limitative examples, which are given purely for purposes of illustration and do not aim to limit the scope of this invention, which is defined by the accompanying claims.

EXAMPLES

(5) I—Preparation of the Detecting Solutions and of the Solutions of Polymers

Example 1

Preparation of a Concentrated Solution of Europium

(6) 200 mg of europium chloride hexahydrate (EuCl.sub.3.6H.sub.2O, CAS No. 13759-92-7) is weighed in a 100-mL flask and 100 mL of ultra-pure water is added. A solution of europium chloride hexahydrate at 2000 ppm is obtained.

Example 2

Preparation of a Concentrated Solution of 2,5-diaminopyridine

(7) 100 mg of 2,5-diaminopyridine dihydrochloride (C.sub.5H.sub.7N.sub.3. 2HCl, CAS No. 26878-35-3) is weighed in a 100-mL flask and 100 mL of ultra-pure water is added. A solution of 2,5-diaminopyridine dihydrochloride at 1000 ppm is obtained.

Example 3

Preparation of a Concentrated Solution of HEPES (Buffer)

(8) 1.191 g of HEPES (C.sub.8H.sub.18N.sub.2O.sub.4S, CAS No. 7365-45-9) is weighed in a 100-mL flask and 100 mL of ultra-pure water is added. A solution of HEPES at 11 910 ppm is obtained.

Example 4

Preparation of a Detecting Solution

(9) 5 g of sodium chloride is weighed in a 250-mL flask and 219.4 mL of ultra-pure water is added. The following are then added, in this order: 25 mL of the solution of HEPES prepared according to Example 3, 625 μL of the solution of europium prepared according to Example 1 and 5 mL of the solution of 2,5-diaminopyridine prepared according to Example 2.

Example 5

Preparation of a Stock Solution of Water-Soluble Anionic Polymer 3630

(10) The water-soluble anionic polymer 3630 is a random copolymer of acrylamide and sodium acrylate (70/30 in mol %). It is a linear polymer having a molecular weight of about 18 MDa.

(11) A 10 g/L concentrated solution of water-soluble anionic polymer 3630 in salt water is prepared by dissolving 1 g of polyacrylamide 3630 in 100 mL of salt water (referenced at 6 g/L). 1 mL of this solution is taken and is put in a 100-mL flask and 99 mL of salt water (referenced at 6 g/L) is added. A 100 ppm solution of water-soluble anionic polymer 3630 in salt water is obtained.

Example 6

Preparation of a Stock Solution of Water-Soluble Anionic Polymer AN977

(12) The water-soluble anionic polymer AN977 is a random copolymer of acrylamide and sodium acrylate (34/66 in mol %). It is a linear polymer having a molecular weight of about 8 MDa.

(13) A 100 ppm solution of water-soluble anionic polymer AN977 in salt water is prepared according to the procedure described in Example 5 using 1 g of polyacrylamide AN977 in place of 1 g of polyacrylamide 3630.

Example 7

Preparation of a Stock Solution of Water-Soluble Anionic Polymer AN125

(14) The water-soluble anionic polymer AN125 is a random copolymer of acrylamide and acrylamido-2-methyl-2-propanesulphonic acid (75/25 in mol %). It is a linear polymer having a molecular weight of about 8 MDa.

(15) A 100 ppm solution of water-soluble anionic polymer AN125 in salt water is prepared according to the procedure described in Example 5 using 1 g of polyacrylamide AN125 in place of 1 g of polyacrylamide 3630.

(16) II—Detection and Quantification of the Polymers

(17) Quantification of the Additives by Time-Resolved Fluorescence (TRF):

(18) The measurements were carried out on an Agilent Cary Eclipse spectrofluorometer. The luminescence lifetime of the rare earths increases with the decrease in the number of water molecules in their coordination sphere. Complexing of the rare earths by the polymers thus allows them to be detected and quantified.

(19) The fluorescence lifetimes of these complexes are typically of the order of a millisecond. This property in particular makes it possible to distinguish them from the fluorescence of organic compounds, which is of the order of a microsecond.

(20) The complexes of europium have four notable emission peaks in the visible: 536, 595, 614 and 650 nm. The limits of the equipment (loss of sensitivity for λem>650 nm) led us to quantify these entities via the emission at 614 nm. The intensity of the peak is related to the concentration, the degree of complexing and the detection conditions.

Example 8

Quantification of Polymer 3630—Plotting a Calibration Line

(21) A range of standard solutions 0-100 ppm is prepared by dilution with salt water at 6 g/L of the solution at 100 ppm prepared in Example 5. Each standard is then diluted 10-fold in the detecting solution prepared according to Example 4. For this, 9 mL of the detecting solution prepared according to Example 4 is taken and introduced into a 10-mL flask. 1 mL of the standard solution to be assayed is added. After 1 h, 2.5 mL of the mixture of standard and detecting solution is taken and introduced into a spectrophotometer tank (ref: Sarstedt® PMMA cuvette 2.5-4.5 mL). The contents of the cuvette are finally analysed by time-resolved fluorescence.

(22) FIG. 1 shows the calibration line obtained. These data show that it is possible to carry out quantitative analyses of additives used in the enhanced recovery of oil and shale gas in an aqueous fluid.

Example 9

Quantification of Polymer AN977—Plotting a Calibration Line

(23) A range of standard solutions 0-100 ppm is prepared by dilution in salt water at 6 g/L of the solution at 100 ppm prepared in Example 6. Each standard is then diluted 20-fold in the detecting solution prepared according to Example 4. For this, 9.5 mL of the detecting solution from Example 4 is taken and introduced into a 10-mL flask. 0.5 mL of the standard solution to be assayed is added. After 1 h, 2.5 mL of the mixture of standard and detecting solution is taken and introduced into a spectrophotometer tank (ref: Sarstedt® PMMA cuvette 2.5-4.5 mL). The contents of the cuvette are finally analysed by time-resolved fluorescence.

(24) FIG. 2 shows the calibration line obtained. These data show that it is possible to carry out quantitative analyses of additives used in the enhanced recovery of oil and shale gas in an aqueous fluid.

Example 10

Quantification of Polymer AN125—Plotting a Calibration Line

(25) A range of standard solutions 0-60 ppm is prepared by dilution with salt water at 6 g/L of the solution at 100 ppm prepared in Example 7. Each standard is then diluted 5-fold in the detecting solution prepared according to Example 4. For this, 8 mL of the detecting solution from Example 4 is taken and introduced into a 10-mL flask. 2 mL of the standard solution to be assayed is added. After 1 h, 2.5 mL of the mixture of standard and detecting solution is taken and introduced into a spectrophotometer tank (ref: Sarstedt® PMMA cuvette 2.5-4.5 mL). The contents of the cuvette are finally analysed by time-resolved fluorescence.

(26) FIG. 3 shows the calibration line obtained. These data show that it is possible to carry out quantitative analyses of additives used in the enhanced recovery of oil and shale gas in an aqueous fluid.