METHODOLOGICAL ISSUES IN THE CONSTRUCTION OF HYDROGEOLOGICAL AND HYDROGEOCHEMICAL MAPS OF PLATFORM AREAS

P. A. UDODOV, N. M. RASSKAZOV, A. D. NAZAROV, V. G. BYKOV

In constructing hydrogeological and especially hydrogeochemical maps, as well as maps of mineral waters of closed and semi-closed territories, the researcher has to confront a number of difficulties. They are caused by the horizontal, mutually overlapping occurrence of stratigraphic sequences, which makes it difficult to provide a complete characterization of all identified aquifer complexes or horizons. This was what led to the broad introduction into practice of the methodology for constructing sectional maps and horizon-by-horizon maps [4]. The positive aspect of these methods is the possibility of detailed coverage of any aquifer complex of interest. However, such maps make it difficult to trace the vertical zonality of groundwater. In addition, the method still used up to now of placing factual material on maps by hatching, isolines, numbers, or signs distributed uniformly over the area, etc., led to heavy overloading and poor readability of the map.

The method of constructing maps proposed by VSEGINGEO [6], which has recently become widespread, proved entirely satisfactory only for mapping open territories. For closed territories it has the same shortcomings indicated above. Under this method, in essence, it appears possible to characterize in detail only the upper aquifer complex (horizon). Its rational element is the idea, proposed earlier by A. M. Ovchinnikov [4], of characterizing lower aquifer complexes by the method of “illumination.” However, the variant recommended by VSEGINGEO for implementing this idea is not entirely successful and does not allow all of its possibilities to be revealed. A map in this variant is also heavily overloaded and poorly readable.

The methods of VSEGEI, L. A. Yavorsky, V. V. Ivanov, and other authors [2, 37] also possess limited possibilities for a full characterization of groundwater. They make it possible to show only individual hydrogeochemical features of water-bearing deposits, often neglecting other indicators of no little importance.

When compiling any map, the researcher resolves two interrelated questions: what and how to show on the map? That is, he determines its form and content. The content of the map is determined by the purpose of its compilation, and the form by the applied method of depicting (plotting) the necessary material. As noted above, at present there is still no universal method for compiling hydrogeochemical maps. Therefore, in generalizing a large amount of material, the authors were compelled to…

factual material on the groundwaters of Tomsk Oblast, to develop a new methodology for compiling maps (the TPI methodology). We shall not dwell here on the content of the maps; it is covered in detail in other articles—“Mineral Waters of Tomsk Oblast” and “Hydrogeochemical Conditions of the Oil-and-Gas-Bearing Regions of Tomsk Oblast,” where schematic maps of Tomsk Oblast are also presented. We shall consider in somewhat greater detail only the method of depicting factual material proposed by the authors as early as 1968 [6].

The proposed methodology makes it possible to place a large amount of factual material on a single map, to substantially reduce its congestion, and to trace changes in the chemical composition of waters both areally and in section. All this is achieved by combining on one map, by the method of “transilluminating” maps constructed for each aquifer complex, and by placing generalized factual material on horizontal lines, rather than uniformly over the area, as is done at present. The horizontal lines are distributed uniformly over the area. When the maps are combined, the horizontal lines corresponding to the aquifer complexes being characterized are arranged so that they form bundles of lines uniformly distributed over the area. In the bundles, the lines are arranged in accordance with the occurrence of the complexes being characterized in section (by “age”), forming a simplified hydrogeological section.

Factual material can be plotted on the lines in a variety of ways. Below a variant is proposed for a black-and-white version of the map (Fig. 1). For each aquifer complex a map is constructed by generally accepted methods; then zoning is carried out according to selected criteria. For example, by water types: a) by salt composition—the areas of development of chloride–sodium, chloride–calcium–sodium, hydrocarbonate–sodium, and other waters; b) by mineralization—fresh, saline, brine, etc. waters; c) by gas composition—methane, nitrogen, etc.; d) by the content of specific components—iodine, bromine, siliceous, etc.—or by other indicators.

In the case of regional development of one or another water type (according to the selected indicators), the latter can easily be shown on the map by the corresponding symbol on the horizontal lines. Thus, in Fig. 1, water types by mineralization are shown by the character of the lines (brines—solid, strongly saline—dashed, etc.); by salt composition—by symbols (chloride–sodium—birds, chloride–calcium–sodium—an inverted letter “t,” etc.); by gas composition—by circles (methane—fully shaded, nitrogen—not shaded, etc.); by temperature—by numbers; by the content of balneologically active components—by hatching of zones (already after combining the maps). The local development of certain water types (radon, sulfide) in Fig. 1 is shown by definite symbols.

Depending on the purpose pursued in compiling the map (assessment of prospects for oil-and-gas potential, potash content, distribution of mineral waters, etc.), zoning of the territory is carried out (in Fig. 1, zoning is shown according to the development of types of mineral waters by aquifer complexes). A map of mineral waters is given as an example, but the same methodology can easily be applied to the construction of hydrogeochemical and other geological maps. Only the indicators will change. For example, for a map of oil-and-gas prospects according to hydrogeological criteria, the principal indicators will be the content of organic matter, heavy hydrocarbons, ammonia, biogenic nitrogen, gas saturation, gas composition, and, to a lesser extent, salt composition, mineralization, and iodine and bromine content.

Fig. 1. Map of mineral waters of Tomsk Oblast. Legend:

1. Aquifer complexes: Pg—Paleogene, Cr₂—Upper Cretaceous, Cr₁^ap–st—Aptian–Albian–Cenomanian, Cr₁^h–br—Hauterivian–Barremian, Cr₁^v—Valanginian, I₁–₃—Jurassic.
2. Areal zoning: A—area of development of iodine–bromine siliceous (I₁–₃—Cr₁–₂) and iodine–bromine, siliceous ferruginous (I₁–₃) waters; B—area of development of iodine–bromine siliceous (I₁–₃—Cr₁–Cr₂^st), iodine–bromine siliceous ferruginous (I₁–₃, more rarely Cr₁), bromine siliceous (I₁–₃—Cr₁–₂), siliceous (Cr₁^ap–al—Cr₂^st), and mineral waters without specific components and properties (Cr₂); V—area of development of bromine siliceous ferruginous (I₁–₃), bromine siliceous (I₁–₃—Cr₁), siliceous (Cr₁–₂), and mineral waters without specific components and properties (Cr₁–₂); G—area of development of bromine siliceous (I₁–₃), siliceous (Cr₁), and mineral waters without specific components and properties (Cr₁); D—area of development of siliceous (I₁–₃) and mineral waters without specific components and properties (Cr₁); E—area of development of mineral waters without specific components and properties (I₁–₂); Zh—area of development of mineral waters associated with zones of tectonic disturbances—radon, possibly carbon-dioxide waters.
3. Sulfide waters occurrence site.
4. Radon-water discovery site. Vertical zonality: 5—zone of iodine–bromine siliceous (I₁–₃—Cr₁–₂) and iodine–bromine siliceous ferruginous (I₁–₃, more rarely Cr₁) waters; 6—zone of bromine siliceous (I₁–₃—Cr₁–₂) and bromine siliceous ferruginous (I₁–₃) waters; 7—zone of siliceous waters; 8—zone of mineral waters without specific components and properties; 9—zone of sporadic development of fresh ferruginous waters (Cr₂—Pg); 10—zone of fresh waters. Chemical composition: 11—chloride calcium–sodium, 12—chloride sodium, 13—hydrocarbonate–chloride sodium, 14—hydrocarbonate sodium or calcium. Mineralization: 15—more than 36 g/l, 16—36–10 g/l, 17—10–3 g/l, 18—3–1 g/l, 19—less than 1 g/l. Gas composition: 20—methane, 21—nitrogen–methane, 22—methane–nitrogen, 23—nitrogen. Temperature: 24—formation temperature, °C; 25—active wells with mineral waters: 1—Sosninskaya 104-bis with iodine–bromine siliceous thermal saline waters, 2—Kolpashevskaya 5-R with sulfide thermal saline waters, 3—Kolpashevskaya 1-R with mineral waters without specific components and properties, 4—Beloyarskaya 1-R with mineral waters without specific components and properties, 5—Zavarzinskiye with radon cold fresh waters. Boundaries: 26—of areas, 27—of zones, 28—of distribution of aquifer complexes, 29—of basement outcrops.

In a color version of the map, some of the symbols may be replaced by the color of lines or circles. For example, districts may be shown by the corresponding color rather than by letters (as in Fig. 1); the type of water according to salt composition—by the color of the symbols indicating mineralization (for example, a solid red line will correspond to brine chloride-sodium waters, etc.); the type of water according to gas composition—by the coloring of the circle; the type of water according to the content of specific components—by the color of the hatching or of another symbol, and so on.

It should be noted that the proposed variants for plotting factual material are not all-embracing. The method of depicting factual material may be chosen by each author depending on the purpose of the map, the diversity of the factual material, and other indicators.

REFERENCES

1. M. E. Altovskii, N. A. Marinov et al. On the methodology of compiling hydrogeological maps. In: Problems of Hydrogeology. Moscow, Gosgeoltekhizdat, 1960.

2. Hydrochemical Map of the USSR. Map of Mineral Waters. Edited by I. K. Zaitsev and N. I. Tolstikhin, 1964.

3. V. V. Ivanov, A. M. Ovchinnikov, L. A. Yarotskii. Map of Underground Mineral Waters of the USSR. Moscow, Gosgeoltekhizdat, 1960.

4. A. A. Kartsev. Hydrogeology of Oil and Gas Fields. Moscow, Gostoptekhizdat, 1963.

5. Methodological Instructions for Hydrogeological Surveying in Closed Territories at Scales of 1:500,000, 1:200,000, and 1:50,000. Moscow, Nedra, 1968.

6. A. A. Rozin, P. A. Udodov, N. M. Rasskazov, A. D. Nazarov et al. Map of mineral waters of Tomsk Oblast. In: Questions of the Study and Use of Underground Waters of the USSR. Leningrad, Nauka, 1970.