Method and solution for assaying inhibitors in a petroleum fluid containing water
A method for detecting and quantifying additives in a complex aqueous fluid, and a method for detecting an inhibitor of mineral deposition or corrosion, injected in a gas or oil well. The invention also relates to a developer solution including a lanthanide and a chelating agent for detecting said additives or inhibitors.
1. Method for detecting additives in an aqueous fluid, comprising:
a. mixing a developing solution comprising a lanthanide cation and a lanthanide chelating agent, with a sample of the aqueous fluid to be analysed optionally comprising at least one additive, under conditions allowing complexing of the lanthanide by the chelating agent and by the additive that is optionally present,
b. detecting and, optionally, quantifying the variation in fluorescence associated with the possible presence of the additive in the aqueous fluid by time-resolved fluorescence,
wherein the chelating agent is selected from the group consisting of diaminopyridine, imidazoline, hydrolysed poly(maleic anhydride), EDTA, oxalic acid, acetylacetonate, thiodiacetate, nitrilotriacetic acid, or derivatives thereof.
2. Method according to claim 1 , wherein the developing solution further comprises at least 1 g/L of chloride ions.
3. Method according to claim 1 , wherein the developing solution further comprises at least 1 g/L of a chemical compound used in the production of buffer solution, by 4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid (HEPES).
4. Method according to claim 1 , wherein a concentration ratio of the chelating agent to the lanthanide cation is between 1:10 and 10:1.
5. Method according to claim 1 , wherein the lanthanide cation is selected from: Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm and Yb, and mixtures thereof.
6. Method according to claim 1 , wherein said additive to be detected is present and is an inhibitor of mineral deposits or of corrosion.
7. Method according to claim 6 , wherein the inhibitor is of mineral deposits and is selected from:
polyphosphates,
organophosphonates,
polycarboxylic acids,
polymers with a sulphonic acid function, in particular the copolymers of styrenesulphonic acid and maleic acid,
polyphosphinocarboxylic acid (PPCA), optionally sulphonated,
polyethyleneimine (PEI),
silicone polymers functionalized with amine groups, and
copolymers based on quaternary ammonium.
8. Method according to claim 6 , wherein the corrosion inhibitor is selected from cyclohexylamine, hexylamine, morpholine, octadecylamine, diethylaminoethanol, the imidazolines and the betaines.
9. Method according to claim 1 , wherein an integration delay between excitation of the sample to be analysed and measurement of a signal emitted is between 0.001 and 10 ms.
10. Method according claim 2 , wherein the concentration of chloride ions is between 10 and 50 g/L.
11. Method according to claim 4 , wherein the concentration ratio is between 1:3 and 3:1.
12. Method according to claim 5 , wherein the lanthanide cation is Eu.
13. Method according to claim 9 , wherein the integration delay between excitation of the sample to be analysed and measurement of the signal emitted is between 0.01 and 5 ms.
14. Method according to claim 9 , wherein the integration delay between excitation of the sample to be analysed and measurement of the signal emitted is between 0.1 and 3 ms.
15. Method according to claim 1 , wherein said additive to be detected is present and does not have intrinsic fluorescence.
16. Method according to claim 1 , wherein the aqueous fluid is an extract of a petroleum fluid containing water.