Method of exploration of uranium deposits

Abstract

FIELD: mining industry.SUBSTANCE: invention relates to methods for exploring uranium deposits for mining by borehole in-situ leaching. The method includes drilling exploratory hole profiles to the ore-bearing horizon with a step according to the exploration stage, core recording, core testing, geophysical logging and groundwater inflow testing, and identifying a thalweg in the ore-bearing horizon. At the first stage, exploratory drilling is carried out along the thalweg up and down the paleovalley, until the uranium content in the ore-bearing rocks decreases to less than satisfactory levels. At the second stage, drilling is carried out in the direction of the paleovalley strike. Drilling in the near-shore parts of the paleovalley is carried out by reducing the distance between wells in the exploration profile at the beginning of the development of the near-shore part of the paleovalley by half the previous distance between boreholes.EFFECT: reduction in exploration costs and an increase in ore reserves for the subsoil user.2 cl, 2 dwg

Description

[0001] Technical field

[0002] The invention relates to the mining industry, namely to methods for exploring infiltration-type uranium deposits for mining by borehole underground leaching.

[0003] Prior Art

[0004] Currently, the range of methods for exploring uranium deposits is quite diverse, from chemical analysis of core rocks, geophysical surveys of wells, analysis of groundwater samples to the determination of radioisotopes in vegetation samples.

[0005] A known method for exploring uranium deposits by determining the boundary of the pinch-out zone of formation oxidation in infiltration deposits of the sandstone type, includes measuring the sulfide ion content in formation waters, drawing the boundary of the pinch-out zone of formation oxidation along the midpoints of the distances between wells where there is no sulfide ion and the nearest isoconcentrate, while the sulfide ion content is determined by polarographic logging at a mercury dripping electrode potential of minus 0.6 V (USSR AS SU 1788226 A1, 15.01.1993, Bulletin No. 2). The main disadvantages of this method are the low reliability of the results obtained with manual data approximation, which entails an approximate determination of the location of the formation oxidation zone, as a result of which there is a risk of unconfirmable reserves during mining development work.

[0006] A known method of exploring uranium deposits for mining by in-situ leaching by identifying the pinch-out of the formation oxidation zone based on the study of core during drilling wells at various stages of exploration. (Shumilin M.V. et al. Exploration of uranium deposits for mining by the method of in-situ leaching. Moscow, Nedra, 1985, p. 66). The main disadvantage of this method is the low core yield in water-saturated ore-bearing horizons due to erosion (sands, sandstones) during drilling and an increase in the cost of wells during core drilling, which reduces the economic efficiency of exploration, and there are also risks (with a constant step between wells in the exploration profile) of missing ore intervals in the tiered location of ore in sediments of different ages.

[0007] The closest (prototype) to the declared one is the method of exploration of uranium deposits, including paleovalley type, which includes drilling exploratory wells along profiles with a step corresponding to the exploration stage, core testing, geophysical studies of wells and conducting experimental filtration works (Brovin K.G., Grabovnikov V.A., Shumilin M.V., Yazikov V.G. "Forecast, prospecting, exploration and industrial evaluation of uranium deposits for mining by underground leaching." - Almaty, Gylym, 1997, pp. 176-205). The main disadvantages of the known method are the increase in drilling costs due to the need to thicken the boreholes in exploration profiles to clarify the morphology of the ore deposit and the failure to expose uranium mineralization in the case of tiered ore occurrence in paleovalley-type deposits.

[0008] The claimed technical solution is aimed at creating a highly effective method for exploring uranium ores of the paleovalley type, allowing for exploration of multi-level ore bodies located in deposits of different ages.

[0009] Disclosure of invention

[0010] The technical result achieved by using a new method for exploring uranium deposits is a reduction in the costs of exploratory drilling and an increase in the reserves of the subsoil user, which will increase the economic attractiveness of the site.

[0011] Unlike the prototype, the claimed method proposes to conduct exploration along the thalweg along the paleovalley strike in the first stage, and transverse profiles in the second stage, while reducing the distances between wells along the exploration profiles in the marginal parts of the paleovalley. This will reduce the number of exploratory wells and ensure the exposure of ore in tiered deposits in sediments of different ages with a corresponding increase in reserves. The distinctive feature "a thalweg is distinguished in the ore-bearing horizon" is essential, since the thalweg in paleovalleys is a permeable and ore-controlling structure with high productivity, through which mass transfer and accumulation of uranium occurred during the movement of uranium-bearing solutions from the upper and lateral sediments of the paleovalleys (Nikitina E.S.Geological structure and conditions of localization of uranium deposits of the paleovalley (basal) type on the Amalat plateau / / Abstract of a dissertation for the degree of candidate of geological and mineralogical sciences, Moscow, 2014, p. 18). For example, thalwegs can be identified based on the results of airborne geophysical studies using electromagnetic sounding with the EKVATOR system, where detailed three-dimensional models of the distribution of specific resistances are created down to a depth of 400 m with a cell of 25×25×10 m, which makes it possible to identify buried paleovalleys and their structural elements - thalwegs, bottoms and sides (Volkovitsky A.K., Karshakov E.V., Moilanen E.V. New helicopter electrical exploration system "Equator" for the airborne method of transient processes / / Zapiski Gornogo Instituta. 2011. Vol. 194, pp. 154-157).

[0012] The distinguishing feature, "at the initial stage, exploratory drilling is conducted up and down the paleovalley along the thalweg until the uranium content in the less-than-qualified ore-bearing rocks decreases," is also new, as the exploration profiles are set across the strike of the paleovalley, whereas drilling up and down the thalweg along the paleovalley has not been reported in the public domain. This approach allows for mapping the qualifiable ores along the strike of the paleovalley, determining the length of qualifiable mineralization, and setting transverse exploration profiles not "blindly," but purposefully, based on the ore already explored.

[0013] The distinguishing feature, "in the second stage, drilling is carried out across the strike of the paleovalley, while drilling in the marginal parts of the paleovalley is carried out, reducing the distance between boreholes in the exploration profile," is also new. This approach allows for a reduction in the number of boreholes in the exploration profile in the marginal parts of the paleovalley while simultaneously not missing ore bodies in tiered deposits of different ages. The author has not encountered this approach in the open literature.

[0014] The distinctive, essential feature "the distances between boreholes in the profile begin to decrease at the onset of development of the paleovalley marginal portion" is a clarifying feature that determines the location where the distances between exploration boreholes begin to decrease, as staged ore formation occurs in sediments of various ages in the marginal portions of the paleovalley. For example, the pinching out of the oxidation zone, which retreats toward the margins in the lower reaches of paleotributaries and the margins of stem paleovalleys, as well as in the upper layers of sedimentary deposits, was practically not detailed during exploration of the Khiagda ore field (Vitim uranium ore district). Uranium mineralization, due to the pinching out of the ground-stratal oxidation zone, is formed:

[0015] • in the weathering crust of the granite foundation;

[0016] • in sedimentary deposits of the lower sub-formation of the Lower Dzhilindinskaya Formation;

[0017] • in the volcanogenic-sedimentary deposits of the upper subsuite of the Lower Dzhilindinskaya suite;

[0018] • in the volcanogenic deposits of the Upper Dzhilindinskaya suite (Novgorodtsev A.A., Martynenko V.G., Gladyshev A.V. Prospects for increasing the resource potential of the Khiagda ore field / / Proceedings of the Third International Symposium on Uranium Geology, FSUE VIMS. Moscow, 2013, pp. 114-115). A targeted study of the named ore-bearing horizon over the entire ore field will reveal multi-tiered mineralization due to the wedging out of the oxidation zone not only in the upper reaches of the paleotributaries, but also in the sides of the Amalat and Atalanginskaya trunk paleovalleys.

[0019] The distinctive essential feature "the distance between wells in the profile is reduced by half of the previous distance between wells" prescribes a change in the network of exploratory wells in the profiles for a more detailed study of the near-side parts of paleovalleys, where tiered ore bodies are located in sediments of different ages, and which will reduce the risks of incomplete exploration of the ore field, which will subsequently lead to complications during operational work, including failure to confirm reserves (Novgorodtsev A.A., Martynenko V.G., Gladyshev A.V. Prospects for increasing the resource potential of the Khiagda ore field / / Proceedings of the third international symposium on uranium geology, FSUE VIMS.M. 2013. pp. 114-115).

[0020] The combination of the above-mentioned distinctive essential features of the claimed technical solution will make it possible to achieve the stated goal in full.

[0021] Implementation of the invention

[0022] Below is information provided confirming the implementation of the proposed invention and showing its effectiveness in relation to known technical solutions.

[0023] The diagram - Fig. 1 and Fig. 2 shows an example of implementing the claimed method.

[0024] In the paleovalley, the thalweg (1), bottom (2) and sides (3) of the paleovalley are identified using known methods - Fig. 1. In the first stage, exploratory wells (4) are drilled along the identified thalweg (1) of the paleovalley up and down the strike of the paleovalley until the uranium content in the exploratory wells (5) decreases below the standard parameters. In the second stage of exploration, exploratory wells (6) and (8) are drilled in the cross of the strike of the paleovalley - Fig. 2, until the uranium content in the exploratory wells (5) decreases below the standard parameters. In this case, exploratory wells (8) in the near-shore part of the paleovalley (3) are drilled at distances between wells (4) and (6) that are reduced by half compared to the previous ones, which makes it possible to identify the lower tier of mineralization (7) and the upper tier of mineralization (9), including in sediments of different ages that make up the section of the paleovalley.

[0025] The effectiveness of using the claimed method lies in the possibility of identifying uranium reserves in the near-shore parts of the paleovalley and reducing the risks of missing ore bodies, which leads to an increase in the reliability of exploration, as clearly demonstrated by the ore projection contour (10) - Fig. 2 and, accordingly, a reduction in the risks of not confirming reserves at the stage of operation during mining preparation work.

Claims

1. A method for exploration of uranium deposits, including drilling profiles of exploratory boreholes into an ore-bearing horizon with a step according to the exploration stage, core documentation, core testing, conducting geophysical studies of boreholes and experimental filtration work, characterized in that a thalweg is identified in the ore-bearing horizon, wherein at the first stage exploratory drilling is carried out along the thalweg up and down the paleovalley, until the uranium content in the ore-bearing rocks of less than standard quality decreases, and at the second stage drilling is carried out in the cross of the strike of the paleovalley, wherein drilling in the marginal parts of the paleovalley is carried out by reducing the distances between boreholes in the exploratory profile, and the distances between boreholes in the profile begin to be reduced at the beginning of the development of the marginal part of the paleovalley.

2. The method according to paragraph 1, characterized in that the distances between wells in the profile are reduced by half the previous distance between wells.

Images