SU1588863A1 - Method of determining chemical stability of surfactants - Google Patents

Abstract

The invention relates to the oil industry, in particular to determining the chemical stability of surface-active substances (surfactants) used to extract residual oil, and can be used to assess their suitability for industrial testing. The purpose of the invention is to improve the rapidity of the method for determining non-ionic surfactants -active substances (nonionic surfactants). The method includes keeping the nonionic surfactant solution in formation water with disintegrated reservoir rock under the thermobaric conditions of a particular field for at least 21 hours. The weight ratio of nonionic surfactants: reservoir reservoir rock: reservoir water is (0.5-1): 1: (49, 5-49). In order to ensure the correctness of the results, the monitoring of the state of the nonionic surfactants includes the quantitative isolation, identification and analysis of nonionic surfactants and chemical degradation products, which is carried out using thin-layer chromatography on Silufol plates, eluent ethyl acetate: ethanol: ammonia in a 1: 1: 0 ratio, four. The products of chemical degradation of nonionic surfactants are also separated from the mixture by stepwise extraction with solvents taken in the sequence: hexane, ether, benzene, chloroform, or column chromatography with the sequence of eluents: hexane, benzene, ethanol, acetone. 3 hp f-ly, 3 ill.

Description

The invention relates to the oil industry, in particular to the determination of the chemical stability of surfactants used to extract

- residual oil, and can be used to assess their suitability for industrial tests.

1, the stability of α-surfactants and compositions on their basis is one of the main requirements imposed on surfactants during injection and the effective use of the latter in various water-flooding technologies for enhanced oil recovery. ,

The purpose of the invention is to increase the expressiveness of the method for determining non-, ionic surface-active substances (nonionic surfactants) and ensure the correctness of the results.

I FIG. 1 shows the kinetic curves that characterize the process of destruction of nonionic surfactants in time; in fig. 2 factors influencing the law on the stability of surfactants: a) temperature; b) pressure; c) degree of hydroxyethylation; FIG. 3 shows the control of the conversion of nonionic surfactants by thin layer chromatography. : Experimental conditions: solution; nonionic surfactants in formation water are maintained; under thermobaric conditions of an I-disintegrated core rock with mixing; In addition, the weight ratio of nonionic surfactants: core rock is about 10 times higher than in the I stratum conditions.

The weight ratio of nonionic surfactants: core; rock: reservoir water (0.5-.; - 1): 1: (49.5-49) J which does not meet the reservoir conditions of any real field, is universal, the same for all deposits, necessary for prompt and reliable determination of the degree of chemical degradation of nonionic surfactants under the conditions of any field (see table).

The essence of the method is as follows.

The ground representative sample of the rock is mixed — with the investigated for chemical stability, a solution of nonionic surfactants of 0.5–10% concentration in the charge water from the field under study, taken in mass ratios of core rock: nonionic surfactants: surface water (0.5–1): 1: (49., 5-49), placed in an airtight container.

Create thermobaric conditions of a particular field. The pressure corresponding to the reservoir is maintained with nitrogen. The temperature is strictly regulated.

The reaction mass is maintained under conditions as close as possible to the reservoir of a specific field.

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neither, within 7-21 hours, preferably 14h.

The control over the processes occurring with the surfactant is carried out by thin layer chromatography (TLC) using a force of ethanol: ethyl alcohol: alcohol: ammonia 1: 1: 0.4 (see Fig. 3).

The products of chemical degradation and the remaining surfactant are separated from the aqueous solution by one of the known methods: stepwise solvent extraction: hexane, ether, benzene, chloroform: extraction with chloroform or with required alcohol.

Separation of the degradation products was carried out using silica gel column chromatography (silica gel 0.2-0.4 mm), eluents: hexane; benzene, alcohol, acetone (150 ml each).

The solvents are distilled off, and the individual degradation products and surfactants isolated and checked by TLC are analyzed by physicochemical methods (IR, PMR spectroscopy, GLC and elemental analysis). The chemical stability of the latter is determined by the amount of the isolated products of the chemical destruction of the surfactant and the amount of the remaining molecular surfactant.

Example. 1 g of Arlanskoye rock, 1 g of OP-10 and 49 ml of produced water from the same field are loaded into an autoclave or pressurized vessel. Mix and take a sample to remove thin layer chromatography (microsyringe, sample volume 2-5 µl). The original chromatogram shows the presence of one zone, characteristic of the nonionic surfactants.

The autoclave with the reaction mixture is closed, a pressure of 10 MPa is created and the temperature is set at 30 ° C, corresponding to the conditions of the Arlan field.

The reaction mixture is kept under the specified conditions with stirring for 21 hours.

After cooling and pressure relief, the autoclave is opened and a sample is taken to remove TLC and control the destruction of nonionic surfactants. The presence on TLC, except for the zone characteristic of nonionic surfactants, of other zones qualitatively indicates the occurrence of chemical decomposition of nonionic surfactants, as well as the number of degradation products formed. In this

In the case of 5 additional zones, there are five products of destruction.

The remaining intact nonionic surfactants are extracted from the reaction mass and the degradation products are chloroform 4 times 100 ml. The extract is evaporated to a volume of 7-10 MP.

Separation of nonionic surfactants and individual degradation products is carried out by the method of column chromatography on silica gel. Consecutive elution was carried out with solvents: hexane, benzene, ethanol, acetone, 100 MP each. Distillate solvents -. individual, nonionic surfactants isolated and tested by TLC, and decomposition products are weighed and analyzed by IR and PMR spectroscopy, elemental analysis and GLC chromatography are performed.

The degree of chemical degradation is determined by the quantitatively allocated individual degradation products as the ratio of the total mass of degradation products to the mass of the original nonionic surfactants taken to the test.

For example, destruction products of 0.72 g were isolated, of which, g: alkyl phenol 0.18; unsaturated oxyethylated alkylphenol 0.11; polyethylene glycol 0.21; bis (octylphenoxyethyl sulfide) 0.09; hydrocarbon mixture 0.12.

Accordingly, the degree of chemical degradation is:

and j. 100% L ,.

It is quantitatively the selection of individual degradation products, their identification and analysis ensure the correctness of the determination of the degree of chemical degradation of nonionic surfactants on the rock.

Thus, the method gives an unambiguous direct answer about the degree of chemical destruction or AB stability based on selected individual 50 products.

The time needed to determine the degree of chemical stability of surfactants is reduced, and the tool makes it possible to evaluate in laboratory tests the stability of surfactants in

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conditions as close as possible to the reservoir.

Claims (4)

1. A method for determining the chemical stability of surface-active substances (surfactants), including maintaining the surfactant solution in the formation water for a predetermined time and for this temperature and monitoring of the surfactant state, characterized in that, in order to increase the expression of the method for determining non-ionic surfactants (nonionic surfactants), the nonionic surfactant solution in the reservoir water is kept with the disintegrated reservoir rock under the temperature and pressure conditions of the deposit 21 h, and the mass ratio of the nonionic surfactants: the reservoir rock: water reservoir is (0.5 -1): 1: (49.5-49). 2. The method according to claim 1, in accordance with paragraph 2, in order to ensure the correctness of the results, the monitoring of the condition of the nonionic surfactants includes the quantitative isolation, identification and analysis of nonionic surfactants and chemical degradation products, which is carried out by thin layer chromatography on Silufol plates, eluent ethyl acetate: ethanol: ammonia in the ratio of 1: 1: 0.4. 3. The method according to claim 1, distinguishing from that the chemical decomposition products of the nonionic surfactants are separated from the mixture by step extraction with solvents taken in the sequence: hexane, ether, benzene, chloroform. 4. The method according to claim 1, distinguished by the fact that the chemical decomposition products of NSAS are separated from the mixture by column chromatography with a sequence of eluents: hexane, benzene, ethanol, acetone.