RU2571781C1 - Isotopic method for water nature determination in product of gas and gas condensate deposits - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: at the surveyed deposit reference samples of manufacturing water, reference samples of condensate and brine water are taken from gas-producing formation, liquid samples are taken from product in the wells in this formation, chemical analysis and isotopic composition analysis for hydrogen and oxygen is performed, limit values are defined for isotopic composition analysis for hydrogen and oxygen for reference samples of water and liquid samples of the product from wells, areas of values for isotopic composition in reference samples of water and liquid samples of the product from wells are presented in tabulated form or graphically, each water type nature in the well product is assessed against degree of similarity or match in the above areas or separate points.

EFFECT: water nature in product of well at gas condensate deposits is defined by analysis characterising directly nature of water molecules in isotropic composition of hydrogen and oxygen, which does not depend on chemical composition and content of components solved in water.

1 dwg, 2 tbl

Description

The invention relates to gas and oil production and can be used at the stage of operation (development) of wells of gas and gas condensate fields (GCM) to determine the nature of the water entering the production of wells.

The fluid discharged from the well with a gas stream is usually a mixture of condensation water falling out of the vapor phase when the thermodynamic conditions in the way the gas moves from the formation to the wellhead, with man-made water entering the bottom hole zone and into the wellbore during drilling or repair operations, or with produced water that has penetrated into the well from the bottom of the reservoir.

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; катионы - Na⁺+K⁺, Mg²⁺, Са²⁺, Fe²⁺. На основе измерения химического состава рассчитывают эквивалентные отношения ионных компонентов. Эти же соотношения определяются для эталонных проб. По результатам сравнения химического состава воды в продукции скважин с составом пластовой, конденсационной и технической вод, принятых за эталонные, дают заключение о природе воды в продукции скважин. В случае если техническая вода изготовлена на основе хлорида натрия, а не хлорида кальция, используемые в данном случае критерии не позволяют выявить границу между технической и пластовой водами.Known definition of water types based on chemical analysis and general salinity / 1, 2 /. This technology is widely used in oil and gas geology to determine the progress of formation water into the well during field development and the presence of industrial water. According to this technology, samples of formation water, condensation water, technical water and water are taken from well products; the content of the main macrocomponents is determined by chemical methods in the selected samples: anions - Cl ^- ,

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; cations - Na ⁺ + K ⁺ , Mg ²⁺ , Ca ²⁺ , Fe ²⁺ . Based on the measurement of the chemical composition, the equivalent ratios of the ionic components are calculated. The same ratios are determined for reference samples. By comparing the chemical composition of water in the production of wells with the composition of formation, condensation and industrial water, taken as standard, they give an opinion on the nature of water in the production of wells. If the process water is made on the basis of sodium chloride, and not calcium chloride, the criteria used in this case do not allow us to identify the boundary between the process and produced water.

The disadvantage of this technical solution is the ambiguity of assessing the nature of water in the production of wells and, accordingly, the source of water based on only a chemical analysis of the composition of the incoming water. This is due to the complexity of the chemical analysis of groundwater, the composition of which is formed in a multicomponent system, including water and gas phases, as well as rocks that make up this field. When using this method of diagnosing the nature of water in wells, samples remain with an unknown source.

There is also a method in which the determination of the proportion of condensation, industrial and produced water in the liquid carried with the produced gas is carried out on the basis of the analysis of the chemical composition of the incoming water, its total mineralization and additionally measured to determine the total amount of water in the produced gas of the thermobaric parameters of the gas well / 3 /. By the presence of one or another basic macrocomponent in the incoming fluid and their ratio, the types and proportion of each type of water in the well production are determined. The disadvantage of this method is the high complexity, as well as the ambiguity in the delimitation of formation and man-made waters.

All methods based on chemical analysis have one main drawback, namely that the nature of water is determined by the content of chemical components in it. At the same time, the fluid discharged from the wells always contains a certain amount of mineral salts trapped from man-made or produced water and supplied with the gas-condensate fluid to the production of the wells.

Known geochemical method for determining the nature of water, independent of the presence of chemical components in it, based on the determination of the isotopic composition of oxygen and hydrogen in water, adopted as a prototype / 4, for example, pp. 131-151 /.

The specified method finds application in geochemical studies to determine the genesis of natural waters and allows you to separate the waters of marine genesis from the waters of meteor and surface water bodies (rivers, lakes). In geological practice, this method is used to isolate the waters of various aquifers of oil and gas basins. However, this method cannot be applied to determine the nature of the liquid entering the production of production wells, since in it, as in other sources of information known to us, the isotopic compositions of oxygen and hydrogen are not considered as characteristic for different types of water (condensation, formation , technical) carried out from the wells of HC deposits.

The objective of the invention is to increase the reliability in determining the nature of the water entering the production of wells GK deposits.

The technical result of the invention is the determination of the nature of water in the production of wells of GK deposits by analyzing the isotopic composition of hydrogen and oxygen in water, which directly characterizes the nature of water molecules, independent of the composition and content of components dissolved in water.

The claimed technical result is achieved by the fact that at the studied field they carry out the selection of reference samples of industrial water, reference samples of condensation and produced water from the gas production horizon, carry out sampling of liquid from the production of wells of this horizon, in these samples carry out chemical analysis and analysis of the isotopic composition of hydrogen and oxygen , determine the boundaries (areas) of the values of the isotopic composition of hydrogen and oxygen for reference water samples and liquid samples from well products, tabular and / or gra The ranges of values of the isotopic composition for reference samples and samples from well production are shown in physical form; by the degree of similarity or coincidence of the indicated areas or individual points, the nature of water in the well production is judged.

The method is based on the empirical dependence of the isotopic composition of hydrogen on the isotopic composition of oxygen for various types of water, which can be represented by the linear equation:

δD = Aδ ¹⁸ O + B.

Coefficients A and B are determined based on the values of the isotopic composition of the reference water samples in the studied field.

The share of each type of water in the production of wells in the gas production horizon is determined from the following equations:

a) the proportion of produced water (N _p ):

δD _pr = δD _pl.sr × N _n + δD _k.sr × (1-N _n)

δ ¹⁸ = δ _ave O ¹⁸ O _pl.sr × N _n O ¹⁸ + δ _k.sr × (1-N _n)

b) the proportion of industrial water (N _t ):

δD _pr = δD _t.sr × N _t + δD _k.sr × (1-N _t)

δ ¹⁸ = δ _ave O ¹⁸ O _t.sr × N _t + δ ¹⁸ O _k.sr × (1-N _t)

The proportion of produced water (N _p ) is determined provided:

δ ¹⁸ O and δD _{pr pr>} δD _k.sr and δ ¹⁸ O _k.sr

The proportion of industrial water (N _t ) is determined provided:

_{Dd, etc.,} and δ ¹⁸ _{O, etc.} <δD _k.sr and δ ¹⁸ O _k.sr. ,

where: δD _ave , δ ¹⁸ About _pr - isotopic composition of hydrogen and oxygen in water in the production of wells;

δD area _sr , δ ¹⁸ O area _sr - average isotopic composition of hydrogen and oxygen in produced water;

δD _k.s. , δ ¹⁸ O _k.s. - the average isotopic composition of hydrogen and oxygen of condensation water;

δD _tsr , δ ¹⁸ O _tsr is the average isotopic composition of hydrogen and oxygen of industrial water.

The drawing shows a graph (palette) illustrating the method according to the invention.

The method according to the invention is implemented as follows.

At the gas condensate field under study, two collections of water samples are taken: the first (reference) - samples of formation and condensation water from the wells of the gas producing horizon and samples of process water and the second - samples of liquid from the production of wells of the gas producing horizon.

For a qualitative characterization of water in the selected samples of both collections by chemical method, the macrocomponent composition and total mineralization are determined.

In these samples, the isotopic composition of hydrogen and oxygen is determined by mass spectrometric method. The boundaries (areas) of the obtained values for the specified reference water samples are determined. Table and graphically in the coordinates δD and δ ¹⁸ O show the obtained ranges of the values of the isotopic composition of the reference water samples.

Then, for selected samples of the second collection, the isotopic composition of hydrogen and oxygen is analyzed in accordance with the sequence described above.

By the degree of similarity or coincidence of the obtained regions (or individual points) of the isotopic composition of hydrogen and oxygen, the samples of the liquid from the production of wells with the values of the reference pallets judge the nature of the studied water from the production of wells.

The following is an example implementation of the method.

The method according to the invention was tested on a gas condensate field in Western Siberia (Zapolyarnoye oil and gas condensate field), where there were problems with determining the type of water in the production of wells operating the Cenomanian horizon (Upper Cretaceous K ₂ ). The proposed method was used to determine the nature of the water entering the production of the Cenomanian production wells of this field.

At the first stage, reference samples were taken: condensation and produced water from wells, industrial water from a water conduit and surface water sources, as well as liquid samples from well products, the sources of water in which it was necessary to determine. The isotopic composition and chemical composition of the waters of both collections were measured, and the range of values for each type of water was determined. The results are presented in table. 1 and shown graphically in the drawing (palette).

The relationship between the isotopic composition of hydrogen and oxygen for reference waters of all types in this field is represented by the dependence: δD = 7δ ¹⁸ O + 12, where the coefficient values (A = 7, B = 12) are calculated based on the measured values of the isotopic compositions of the reference samples (Table 1 ) As can be seen from the table. 1 and the resulting palette, the ranges of oxygen and hydrogen isotopic compositions for different types of reference samples do not overlap and are clearly divided into three ranges of values, respectively, of formation (P), condensation (K) and technical (T) water. All three regions have statistically significant differences in the isotopic composition of hydrogen and oxygen in water. The range of values of the isotopic composition of water samples from well products (Pr) does not go beyond the values for the reference samples of condensation, formation and industrial water. Using the above formulas, the values of δ ¹⁸ О and δD were calculated for a liquid (water) in products containing a different proportion of produced, condensation and industrial water (Table 2, points 1-11 on the graph).

According to the results of comparing the isotopic compositions of hydrogen and oxygen (Table 1 and the graph shown, palette), the types of water entering the production of wells of the Zapolyarnoye gas condensate field were identified. As can be seen from the above graph and the data in Tables 1-2, the water in the production of wells is mainly condensation water of the Cenomanian horizon or a mixture of these waters with different proportions of formation (Cenomanian horizon) and industrial water.

In addition, using the interdependence of the isotopic composition of oxygen and hydrogen in the water, the method according to the invention allowed to reliably determine the sources of water input into the production of fifteen production wells of the Cenomanian horizon of the Zapolyarny oil and gas condensate field.

Information sources

1. Zhdanov M.A. Oilfield geology. - M.: Gostoptekhizdat, 1962, p. 186-190.

2. The water of oil and gas fields of the USSR. Directory. Ed. L.M. Zorkina. M .: Nedra, 1989, 382 p.

3. RF patent №2128280, ЕВВ 43/00. "Diagnostic method according to chemical analysis of water discharged from gas wells."

4. Ferronsky V.I., Polyakov V.A. Isotopy of the hydrosphere. M .: "Science", 1983, 277 p.

Claims (1)

An isotopic method for determining the nature of water in the production of wells of gas and gas condensate fields, characterized in that the studied field takes reference samples of process water, reference samples of condensation and produced water from the gas producing horizon, and fluid samples are taken from the production of wells of this horizon, in the indicated samples conduct chemical analysis and analysis of the isotopic composition of hydrogen and oxygen, determine the boundaries (areas) of the values of the isotopic composition of hydrogen and oxygen d For reference water samples and liquid samples from well products, the ranges of isotopic composition values for reference samples and samples from well products are tabulated and / or graphically judged by the degree of similarity or coincidence of the indicated areas or individual points about the nature of water in the well production.

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