PROCEEDINGS
OF THE TOMSK POLYTECHNIC INSTITUTE
OF THE ORDER OF THE OCTOBER REVOLUTION AND THE ORDER
OF THE RED BANNER OF LABOR
named after S. M. KIROV

Vol. 281 1976

ON THE QUESTION OF METHODS FOR EXPLORING COAL DEPOSITS, USING AS AN EXAMPLE THE EXPLORATION OF MINE FIELDS IN THE TOM–USINSK DISTRICT OF THE KUZBASS

V. Ya. Koudelny, P. I. Sherin

(Presented by the scientific seminar of the Department of Geology and Exploration, MPI)

In the article by V. Ya. Koudelny and Yu. N. Popov, included in this collection, certain features of the tectonics of the coal deposits of the Tom–Usinsk district of the Kuzbass are indicated. These features make it necessary to seek new techniques in carrying out exploration work in order to study more fully the structures of mine fields. Below, characteristic errors in deciphering tectonics will be shown, and ways of reducing and eliminating them will be outlined.

In the classification of Kuzbass deposits proposed by E. M. Pakhom and E. M. Senderzon [2], for the purposes of exploration, the simplest type of gentle monoclines with the Biryulinsk and Usinsk subtypes is distinguished. In the characterization of the latter it is stated that it is marked by a monoclinal, gently undulating occurrence of coal seams with dips of 10–35° and by a few minor faults and additional folding. This characterization reflected the coal explorers’ information on the tectonics of the fields of the Tom–Usinsk district at the time the classification was created.

In subsequent years, under the influence of preparatory and production mining operations, ideas about the tectonics of the district were substantially refined, and now its mine fields are assigned to the group with complicated tectonics. In summarizing and comparing the materials of exploration work and of the mine geological service, one has to deal with changes in ideas about the complexity of the structure of particular areas. Naturally, it becomes necessary to consider certain questions of exploration methods under the specific conditions of the district, so that the results of exploration may be assessed more correctly and, at the same time, ways may be outlined for improving the study of deposits of this type. As an example, let us consider the exploration of the field of the V. I. Lenin mine, characterized by a structure typical of many sectors of the Western monocline.

The field of this mine was explored in compliance with the usual stages of exploration. At the stage of preliminary exploration (1946), 8 core boreholes were drilled and 4 adits were driven along seams III, IV–V, and VI over the area from exploration line I to exploration line III (Fig. 1, a). These works confirmed the previously established general gentle monoclinal occurrence of the coal-bearing strata, as well as the high quality of the coal in seams persistent in thickness and simple in structure.

Fig. 1. Seam map of hor. +245 m according to: a) preliminary (1946) and detailed (1949) exploration; b) supplementary exploration and production.
Symbols: correlation of coal seams according to data from: 1 — preliminary exploration; 2 — detailed exploration; 3 — supplementary exploration and production; 4 — disjunctive faults; 5–7 — core-drilling boreholes, drilled: 5 — at the stage of preliminary exploration; 6 — at the stage of detailed exploration; 7 — during supplementary exploration.

Taking into account the notion of the simple structure of the field, at the stage of detailed exploration a sparse grid of exploratory boreholes was selected. The dimensions of the field at this stage were increased in area and included the coal seams of the Usyat and Kemerovo suites. In the southwestern part of the field the distances between exploration lines proved to be within 200–250 m, while over the greater remaining part they amounted to 750 m. The distances between boreholes on the lines were not constant and varied from 100 to 900 m. Detailed exploration made it possible to substantially refine the hypsometry of the coal seams, but showed an almost complete absence of tectonic faults (Fig. 1, a).

The above-indicated density of the exploration grid did not ensure the obtaining of reserves of high categories in the required proportions. The construction of the Usinsk open-pit coal mine and the V. I. Lenin mine (previously called the “Tom-Usinskaya 1–2” mine) required further exploration work. In this connection, in the period 1950–53, additional exploration was carried out, during which 43 core boreholes were drilled with a total footage of 5870 linear m, which amounted to about 80% of the entire preceding volume of core drilling.

Preparatory cutting mine workings and the additional exploration carried out substantially changed the understanding of the fault structure of the mine field (Fig. 1, b) within the boundaries of preliminary exploration. Numerous dislocations were identified and additional folds were refined. It should be noted that this refinement of the structure was due mainly to mine workings. The additional exploration sharply increased the degree of exploration of the coal seams. The coal reserves in the mine field decreased by 9.5%. This decrease occurred as a result of refinement of the hypsometry of the seams, their thickness, and their position at the outcrops beneath the overburden.

Comparison of the exploration results with the materials obtained during operation shows that, with the advance of preparatory and production work, the number of small tectonic faults and flexure-like folds increases. The form of tectonic faults is substantially refined. With core-drilling boreholes, under existing methods of logging and documentation of core material, it is impossible not only to identify small elements of tectonics, but also to reliably detect, under conditions of a dense network of small faults, the relatively larger ones among them. Especially difficult is the detection of shear-type faults located parallel to the main exploration lines.

As a rational basis for a borehole grid at the stage of detailed exploration in areas of similar structural complexity, a borehole grid with distances between exploration lines of 500–600 m may be recommended. Provided that the coal seams are normally explored at their outcrops beneath the overburden and that special structural mapping of boreholes is carried out, this grid ensures the identification of the main regularities of the tectonics of the area being explored. The tectonic faults and folds detected from the boreholes of this grid and from mine workings should be traced by additional boreholes or by intermediate lines.

With a uniform arrangement of exploratory boreholes to the full depth of exploration (350–400 m) and insufficient tracing of coal seams at the outcrops by means of mapping-drilling boreholes and shallow mine workings, a poor degree of study of the near-surface parts of the coal seams is observed. The consequence of this is the familiar situation in which the share of reserves of high categories toward the lower horizons—

there increases sharply. On the horizons scheduled for priority mining, the percentage of reserves of the higher categories (A+B) proves to be very low.

Taking into account the structural features of the monocline areas, as well as the coal industry’s requirements for the volume and quality of the initial geological materials submitted for the design of new construction and the reconstruction of mines and open pits, we proposed that, in exploration of deposits of this type, exploration boreholes be arranged along paired exploration lines [1]. The proposal is based above all on consideration of the specific tectonic features of the Main Monocline, because of which the usual densification of the exploration network by no means always ensures a corresponding increase in the completeness of tectonic study. This is also evident from the history of exploration of the field of the V. I. Lenin Mine. The above point can be illustrated even better by the exploration materials for the more structurally complex field of the “Tom-Usinsk 3–4” open-pit coal mine (Kiizassk areas 1–4).

According to the data from preliminary-exploration boreholes and by analogy with the simple structure of the coal-bearing formation of the same name in the already explored Usinsk areas of the Olzherassk deposit, and also on the basis of geophysical data from the Kiizassk areas, the tectonics of the latter was regarded as very simple. This determined the choice of a comparatively sparse borehole network at the stage of detailed exploration of the areas. The distance between exploration lines proved to be 800–1100 m, and between boreholes on the lines, 250–1000 m.

On the basis of a set of works that included core drilling and hand drilling, the driving of adits, inclines, trenches, and shallow pits, the general monoclinal occurrence of the coal-bearing formation was established, complicated by broad-amplitude wave-like transverse folds and disrupted by a thick diabase dike. The achieved degree of exploration of the coal seams proved to be fairly high. Despite the fact that, when approving the reserves, the VKZ in a number of cases substantially reduced the ratio of reserves of high categories presented by the authors of the detailed-exploration report, pointing both to generally insufficient exploration and to insufficient tracing of the coal seams at their outcrops beneath the overburden, the share of reserves of categories A+B nevertheless proved to be above 50%.

Additional exploration for the purpose of preparing the area for open-pit mining, carried out by densifying the borehole network to distances between exploration lines of 250–500 m and between boreholes of 200–500 m, and by driving mine workings, substantially changed the geological-structural concepts [3]. The main changes consisted in the identification of additional transverse folds in all coal seams, a series of tectonic faults, and in the refinement of the hypsometry of the seams in their near-surface part. The largest tectonic fault of the area (1—1), of the thrust-fault type, was represented at this stage of study as a complex folded surface. In general, the tectonic faults and additional folds identified at this stage of exploration, as well as the character of distribution in the coals of the zone affected by contact influence of the diabase dike, proved to be insufficiently studied for the purposes of preparing the design for construction of the open-pit coal mine. An expression of the latter, in particular, was a significant reduction in the share of category A reserves compared with that approved on the basis of the detailed-exploration data. Owing to the gentler occurrence of the coal seams and the refinement of their outcrops beneath the overburden, the total coal reserves in the area increased substantially.

In parallel with construction of the open-pit coal mine, additional exploration work was carried out. The principal task of this additional exploration was to ...

of the period was the detailing of the conditions of occurrence of the upper coal seams and of fault 1—1, their relationship with the diabase dike, and the nature of its contact effect on the coal. The density of intersections of the upper coal seams in the area of development of priority mining operations increased to 100 m along the strike and to 50 m along the dip of the seams (Fig. 2, a).

Fig. 2. Structural map of seam IV—V according to geological-exploration (a) works (1961) and according to geological-exploration and mining (b) works (as of 1966). Legend: 1 — outcrop of a coal seam; 2 — contours of the floor of the coal seam; 3 — truncations of seams by tectonic faults: a — footwall, b — hanging wall; 4 — diabase dike; 5 — boreholes of core drilling; 6 — prospect pits; 7 — mined-out areas of the seam

Along with mining operations, exploration work also continued by means of driving prospect pits and drilling core boreholes. A fundamentally new point in the geologic-structural concepts for the field of the coal seam, on the basis of these works, was the proposition that coal seams and faults are displaced by a diabase dike. A second point was the partial re-correlation of fault 1—1 and the identification of new faults. The hypsometry and outcrops of the coal seams were substantially refined (Fig. 2, b).

Analyzing the changes in the density of the exploration network and the changes achieved at each stage of exploration in the concepts of tectonics, one may conclude that the principal elements of tectonics are revealed fairly fully when the spacing between exploration lines is 40 m.

500 m. Further ordinary densification of the grid makes it possible to detail individual tectonic nodes, but this is achieved at the cost of an excessive increase in the footage of exploratory drilling. More economical detailing can be achieved by drilling wells along paired exploratory lines. In general, for mine fields with tectonics having features similar to the structure of the areas of the Main Monocline, the following sequence in the study of tectonics by stages of geological-exploration work may be recommended.

At the stage of preliminary exploration, the tasks of studying tectonics should be:

confirmation of the monoclinal occurrence of the coal seams, determination of the elements of their occurrence in different parts of the monocline, and establishment of the principal regularities in changes of strikes and dip angles over the exploration area;

obtaining a general picture of the complications of monoclinal occurrence: the presence and character of undulation, additional folds, flexures;

a preliminary characterization of additional folds of medium size, taking into account their location, morphology, dimensions, and orientation;

establishment of the majority of medium-amplitude faults. If such faults are not found within the explored area, convincing evidence of this fact must be obtained;

systematization of factual materials for judging the degree of disturbance of the coal seams by small-amplitude faults.

To solve these tasks, one or two main exploratory lines should not be single, as is usually the case, but should be accompanied by parallel lines spaced 50–100 m from the main lines. Correlation of sections along paired (closely spaced) lines will make it possible to obtain reliable geological material that more fully characterizes the types and degree of manifestation of plicative and disjunctive disturbances.

At the stage of detailed exploration, great attention should be paid to establishing the regularities of changes in the elements of occurrence of the coal seams within the main structure and the character of the universally developed undulation. Additional folds of medium and partly small dimensions should be detected and studied. Particular attention should be paid to the study of the dimensions and morphology of folds, as well as to the study of the regularities of their position and the character of their manifestation in adjacent seams, bearing in mind the change in plicative disturbance in the section of the coal-bearing sequence. The task is also to identify and trace all medium-amplitude faults. Due attention must be given to determining their form. Transverse strike-slip faults present great difficulty; without careful tracing of seam outcrops beneath the overburden by boreholes, their presence is difficult to determine. The general disturbance of the workable coal seams by small-amplitude faults must be studied: their zones, the intensity and persistence of the zones in adjacent seams, and also their connections with various plicative and disjunctive structures must be established.

At this stage of work, the number of paired lines should be increased. This can be achieved by laying out new exploratory lines near those lines of preliminary exploration along which more complex tectonics is observed or elements of multivariancy occur. Analysis and joint comparison of materials from paired and single-

borehole exploration lines makes it possible to specify the regularities of the tectonics both of individual sectors and of the entire mine field as a whole.

Taking into account the regularities obtained, the next stage of detailed exploration should be the drilling of boreholes along intermediate exploration lines. A fundamental difference between these works and those carried out so far is that the intermediate lines should not be the result of doubling the density of the exploration grid. The locations, as well as the number of lines, should be determined on the basis of the specific geological situation revealed by the preceding work.

A second distinction is that the boreholes of the intermediate lines should be predominantly shallow and should refine the geological situation in the upper horizons. They will also contribute to obtaining reserves of high categories here. The completion of detailed exploration should be the drilling of single deep structural boreholes.

Exploration of coal deposits with the proposed arrangement of exploration intersections should be based on a thorough study and forecasting of tectonics. The latter should be used in choosing the locations of paired exploration lines and especially in arranging intermediate lines and boreholes.

REFERENCES

1. V. Ya. Koudelnyi. On the question of the rational placement of exploration boreholes in the exploration of coal deposits in Kuzbass. Izv. TPI, vol. 201, Tomsk, TSU Publishing House, 1972.

2. E. M. Pakh, E. M. Sendezon. Density of the detailed exploration grid and testing of coal deposits of Kuzbass. Problems of the Geology of Kuzbass, 2. Izv. TPI, vol. 99, Tomsk, TSU Publishing House, 1959.

3. A. M. Chursanov. Basic requirements imposed by design and operating organizations on geologists conducting exploration of quarry fields. Problems of the Geology of Kuzbass, 2, Izv. TPI, vol. 99, Tomsk, TSU Publishing House, 1959.