RU2720658C1 - Method for vapor-phase analysis of combinations of water-soluble volatile and low-volatility reservoir indicators - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to analytical chemistry and can be used in oil and gas industry. Method for vapor-phase analysis of a combination of water-soluble volatile and low volatile formation indicators in which a sample of formation water is placed in a sealed glass container with a rubber membrane, held in a thermostat at temperature of 95 °C for at least 30 minutes, 2 cm³ of a vapor phase is taken with a medical syringe and dosed into the evaporator of a gas chromatograph for analysis, during extraction of the vapor phase between the replaceable needle and the body of the medical syringe a disposable paper filter is installed to remove small droplets of water with tracers dissolved in them.

EFFECT: simplified sample preparation for vapor-phase analysis of a combination of water-soluble volatile and low-volatile tracers.

1 cl, 1 tbl, 1 dwg

Description

The invention relates to gas chromatographic analysis methods and can be used in the oil and gas industries for the quantitative determination of water-soluble formation indicators in formation waters.

It is known that in the oil fields various water-soluble organic and inorganic substances are used for indicator (tracer) studies. Aqueous solutions of tracers are injected into the injection wells and record their flow into the production wells. The information obtained allows us to make effective engineering decisions to increase oil recovery. The most difficult stage of indicator research is the quantitative determination of the marking substance (tracer) in reservoir fluids. This is due to the multicomponent composition of the formation fluids and their high contamination (see: Sokolovsky EV, Soloviev GB, Trenchikov Yu.I. Indicator methods for studying oil and gas bearing strata. - M .: Nedra, 1986. 158 p.) .

It is also known that gas chromatography is widely used to control environmental pollutants. The analysis of volatile components is often carried out by vapor phase analysis. To control the main pollutants in aquatic environments, a large number of standards have been developed in the USA, EU countries and certified methods in our country. According to the analysis of environmental pollutants, hundreds or thousands of works are published every year (see: Yashin Y.I., Yashin E.Ya., Yashin A.Ya. Gas chromatography. M.: Trans-Lit Publishing House, 2009. P. 469-478).

It is known (see: Arutyunov Yu.I., Efremov A.O., Onuchak L.A., Dudikov V.S. // Bulletin of Samara State University, Natural Science Series, 2012. No. 3/1 (94). S. 123-131), the use of aliphatic monohydric alcohols as water-soluble tracers, the quantitative determination of which is carried out by gas chromatography.

A disadvantage of the known methods for the quantitative determination of water-soluble tracers is the relatively low accuracy of the measurement, due to unaccounted for during calibration errors introduced by the changing composition of formation fluids in the research process on the measurement results.

Closest to the proposed invention in terms of essential features is a method of preparing a sample of produced water for gas chromatographic analysis of isopropanol, including separating the sample from oil, removing solids by filtration through a paper filter, mixing 10 cm ^{3 of the} sample with 5 cm ^{3 of} hexane to extract dissolved non-polar substances and after mixing and phase separation, 8 cm ^{3 of the} aqueous layer are taken and poured into a sealed glass container with a rubber membrane. The capacity is kept in a thermostat at a temperature of 95 ° C for at least 30 minutes. Then, 2 cm ^{3 of the} equilibrium vapor phase is taken with a medical syringe and dosed into the vaporizer of a gas chromatograph for analysis of isopropanol (see: RF Patent No. 2478948 C2 // Bull. Inventory No. 10 of 04/10/2013).

The disadvantage of this method is the relatively low precision and increased complexity of the measurement.

The objective of the invention is to increase the precision of measurement and simplify the method of vapor-phase analysis of a combination of water-soluble volatile and low-volatile tracers.

This problem is solved due to the fact that in the method of vapor-phase analysis of a combination of water-soluble volatile and low-volatile tracers, in which a sample of produced water is placed in a sealed glass container with a rubber membrane, it is kept in a thermostat at a temperature of 95 ° C for at least 30 minutes, 2 cm ³ are taken the vapor phase with a medical syringe and dispense it into the vapor of the gas chromatograph for analysis, and when selecting the vapor phase, a disposable paper filter is installed between the removable needle and the body of the medical syringe to remove small water droplets with tracers dissolved in them.

When solving this problem, a technical result is created, which consists in the following:

1. Increases the precision of measurement of volatile and low-volatile tracers, due to the use of a disposable paper filter between the interchangeable needle and the body of the medical syringe to remove small droplets of water with tracers dissolved in them.

2. The procedure for preparing a sample for vapor-phase analysis of a combination of water-soluble volatile and low-volatile tracers is greatly simplified by eliminating non-polar substances from hexane from formation water that interfere with the gas chromatographic analysis of volatile tracers.

An example of a specific implementation of the method.

In FIG. 1 schematically shows a device for vapor-phase analysis of a combination of water-soluble volatile and low-volatile tracers. The device contains a sealed glass container 1 with a sample of produced water, a thermostat 2 with a temperature of at least 95 ° C, a rubber membrane with a union nut 3, a replaceable needle for a medical syringe 4 for selecting the vapor phase, a disposable paper filter type FOFS-17 “Blue Ribbon” 5 removal of fine water droplets with dissolved therein tracers medical syringe 6 and 2 cm ³ with a plastic piston for dispensing the vapor phase in a gas chromatograph for analysis of the evaporator.

Small droplets of water with tracers dissolved in them arise in the tank 1 as a result of a change in pressure during the selection of the vapor phase. These droplets, falling into the gas chromatograph evaporator, do not increase the volume of the introduced sample non-systemically and worsen the precision or random component of the measurement error.

An experimental evaluation of the implementation of the proposed method was carried out on the example of the analysis of two model mixtures. The first mixture contains volatile aliphatic alcohols isopropanol and tertbutanol. The second model mixture contains low-volatile alcohols pentanol and cyclohexanol.

The experiment was carried out on a Crystal-5000.2 gas chromatograph CJSC SKB Khromatek with a flame ionization detector and a column 100 cm long with an inner diameter of 0.3 cm filled with a carbon adsorbent Carboblack-V, with a grain size of 60-80 mesh. On this adsorbent, non-polar substances dissolved in formation water are strongly sorbed and do not interfere with the analysis of water-soluble tracers, which greatly simplified the method. Column temperature T _c = 150 ° C. The excess pressure of the nitrogen carrier gas at the column inlet ΔP = 102 kPa, the carrier gas flow rate at the column outlet F _c = 16 cm ³ / min. The temperature of the evaporator and detector is 200 ° C.

The vapor phase of the model mixtures was dosed into the chromatograph with a 2 cm ³ medical syringe. For the known method without a paper filter, and in the proposed method, a disposable paper filter is installed between the needle and the syringe body.

Each mixture was analyzed at least n≥5 times by known and proposed methods and the average values of the area of chromatographic peaks were determined.

The random component of the measurement error of the components of the model mixtures was determined by the equation

- прецизионность измерения в процентах или относительное среднеквадратичное отклонение среднеарифметического результата измерения.Where

- precision measurement in percent or relative standard deviation of the arithmetic mean of the measurement result.

In the table. 1 shows comparative data of experimental verification of the known and proposed methods according to the results of the analysis of two model mixtures.

Table 1. The results of the experimental evaluation of the known and proposed methods of vapor-phase analysis

No. p / p Tracers Introduced analyte, mg / l Known method The proposed method Found analyte, mg / l

Found analyte, mg / l

1 Flying tracers 1.1. Isopropanol 20,0 321.6 12.6 178.7 5,4 1.2. Tretbutanol 20,0 537.0 12.8 298.3 6.5 2 Low-flying tracers 2.1. Pentanol 20,0 754.8 11.3 420.3 4.2 2.2. Cyclohexanol 20,0 193.7 12.5 110.6 6.5

As can be seen from the data in table 1, the precision or random component of the measurement error of volatile and low-volatile tracers for the proposed method is approximately 2.0 times less than the known one. So, for tertbutanol and cyclohexanol S _r = 6.5% in the proposed method, and in the known method, S _r is 12.8% and 12.5%, respectively.

In addition, the removal of small droplets of water with tracers dissolved in them using a disposable paper filter provides for the proposed method the reduction of the analyte in the dosed sample is not more than two times.

Using the proposed method for vapor-phase analysis of a combination of water-soluble volatile and low-volatile tracers allows you to:

1. To increase the sensitivity of determining water-soluble tracers in formation waters when conducting tracer studies in oil and gas fields.

2. To reduce the consumption of volatile and low-volatile tracers when conducting tracer studies.

3. The vapor-phase analysis of a combination of water-soluble tracers will significantly expand the possibility of determining volatile and low-volatile tracers in a wide variety of formation fluids. Including heavily contaminated rock and reagents.

Claims (1)

A method of vapor-phase analysis of a combination of water-soluble volatile and low-volatility formation indicators, in which a formation water sample is placed in a sealed glass container with a rubber membrane, kept in a thermostat at a temperature of 95 ° C for at least 30 minutes, 2 cm ^{3 of the} vapor phase are taken with a medical syringe and dosed into the evaporator gas chromatograph for analysis, characterized in that when selecting the vapor phase between the interchangeable needle and the body of the medical syringe, a disposable paper filter is installed to remove small droplets of water with tracers dissolved in them.

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