RU2461712C2 - Development method of mineral deposits by drilling of large-diameter core - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: deposit developments are performed after stripping of the deposit; extraction field is separated into a mesh with rhombic cells with sides and a short diagonal equal to diameter of development well. In mesh nodes as centres there first drilled are service wells with diameter of not less than 93-112 mm and core is removed; then, in case there is no frost, wells are filled with surface-active substance solution. Strength and drilling capacity of kimberlite and its fracturing is determined with regard to the core. As per the obtained data there determined is drilling bit of large diameter, method and type of device for separation of well large-diameter core from mass, depth and drilling mode parameters are set for the main well of large diameter, and then, the main well of large diameter is drilled as per the obtained data concentrically to service well; core is removed from mass, lifted to surface and removed from core tube.

EFFECT: higher development efficiency of steep deposits due to optimum selection of drilling tool and parameters of drilling mode.

4 cl, 2 dwg

Description

The invention relates to the mining industry and can be used in the development of mineral deposits, mainly tube-shaped low-volume diamondiferous kimberlites or refinement of the root part of diamond deposits after excavation by underground method.

A known method of underground mining by drilling cylindrical workings [1]. The essence of the method is the sinking from the upper borehole floor of a pilot well with a diameter of 250-300 mm to the height of the floor. In its lower part, on the delivery horizon, an expander (up to 3-5 m) is attached to the drill stand and the well is drilled back to the design dimensions in reverse. After practicing the camera, it is filled with a hardening tab. The disadvantage of this method is the need for underground mining for various purposes.

There is a method of layer-by-layer drilling of tube-shaped diamond deposits, the essence of which is to drill a large diameter hole with a continuous bottom and its subsequent expansion by a mining machine to the contour of a mining field [2]. The advantage of this method is the ability to develop shallow deposits without attaching almost vertical sides of the quarry during the cold season. The disadvantage is the inability to use the method without fixing the sides of the quarry with increasing depth of kimberlite and a high level of mechanical transshipment of kimberlite, contributing to the destruction of kimberlite crystals.

The closest in technical essence and the achieved effect is a method of developing mineral deposits by drilling large diameter core, which can be carried out by various devices for drilling large diameter core-hole method, for example, a mechanical core drill, which is also used to implement the core separation method [3]. In this case, at first, in the usual way, an auxiliary borehole of small diameter is passed, then a device for core removal is introduced into this borehole, and at the same time, a borehole of large diameter passes through a core drill. Core detachment is carried out by supplying drilling fluid under high pressure, but when the rocks are strong, the fluid pressure is increased by the action of explosives.

The through hole on the axis of the core has the advantage that in the cavity of this hole you can place various devices for tearing the core. If the core cannot be torn off by the device, then it is possible to additionally act by any known method and device outside the core by placing a specific device for this in the annular cavity of a large diameter well. But the main advantage is that in the volume of large diameter kimberlite core diamonds remain intact. However, the drilling of an auxiliary well by a conventional method, i.e. continuous slaughter, does not allow sufficient use of the presence of a central channel in a large diameter core, for example, to obtain reliable information for determining the location (drilling depth) and the method of separating the core from the array, selecting a core and optimizing the parameters of the drilling mode with a core. The following tasks follow from this:

- drilling of an auxiliary well with core extraction and determination by core of a rational type of drill bit and parameters of the mode of drilling by it of the main well of large diameter, concentric auxiliary well;

- selection of the strength and fracture of the core of the auxiliary well of the method and type of device for separating the core of the main well of large diameter from the array and the location (drilling depth) of this compartment.

These tasks can be solved as follows. According to the proposed method for the development of minerals, including the opening of minerals, drilling auxiliary wells of small diameter and major wells of large diameter with core drilling, its separation from the array, surface elevation and subsequent shipment, the excavation field is divided into a grid with rhombic cells, sides and short the diagonal of which is equal to the diameter of the main well, in the nodes of this grid, as the centers of boring wells, they drill the entire depth of the mineral deposit with core extraction auxiliary wells with a diameter of not less than 93-112 mm, express methods are used to investigate the strength properties of core rocks, outline the rational type of the drill bit and the parameters of the drilling regime for the main large diameter well by these properties, select the location (depth of drilling) of the core according to the strength and fracture of the core from the array, the method and type of device for this separation, then the main borehole of large diameter, concentric to the auxiliary borehole, is drilled with core extraction.

To implement the proposed development method, various methods and devices can be used for drilling pits, large-diameter wells and mine shafts or drilling stone columns for buildings. When cleaning the face with air or water above the core pipe, the speed of the particles of drill cuttings sharply decreases, and their rise stops abruptly, so a sludge trap should be installed here. Advanced and fast drilling of auxiliary wells in the absence of permafrost creates conditions for the long-term action of surfactant solutions. According to the research of IHD by A.A. Skochinsky, when the surfactant concentration in the solution is not higher than 0.1% in kimberlite, the compressive strength decreases by 1.9-2.2 times, and when combined with liquid and gaseous surfactants (carbon dioxide CO ₂ ) - 2.5-3.5 times. Therefore, the use of surfactants in rocks with a positive temperature will not only facilitate the drilling process, but also the subsequent crushing and grinding of kimberlite. In this regard, the development method involves drilling a pilot well with a diameter of at least 93 mm for pouring a surfactant solution and softening kimberlite. Unfortunately, the use of surfactants is effective if the pores of the rock are not filled with ice. When drilling auxiliary wells, additional measures are taken to set the vertical axis of the wells and prevent their curvature, since the auxiliary well can, if necessary, be used as a guide to set the direction of the axis of the main well.

When drilling kimberlite core, the most intractable problem is core failure. If you drill a well with a diameter of 1000 mm in kimberlite, then to break the core, you need to apply a force of 300-400 tons. To create such a separation force, it is necessary to apply a pressure of at least 150-200 atmospheres to the bottomhole device. Although in our time and 500 atmospheres is not a problem, however, the core itself can be destroyed by crushing under the core grabber, violating the conditions for transferring the separation force to the core. Therefore, it is necessary to search for ways to soften or weaken the core in the area of its separation. In this regard, it is possible to use various sawing devices, well expanders, heating devices, hydraulic fracturing, thermal stresses during heating, and even the energy of microexplosions. In this case, the presence of a cavity in the center of the core can serve as the channel of energy transfer with which the separation force and the torsion moment, developed by the drilling machine for core disruption, will be summed. If this is not enough, it is necessary to raise the core pipe and place in the well cavity devices that implement various methods of separating the core from the array. The simultaneous action of destructive forces inside and outside the core makes it possible to tear off a kimberlite core with a diameter of more than 1 m. However, if there are intersecting cracks or fracture zones in the section of the well, then large core is blasted in the most damaged part of the core, using core grabbing devices, overlapping core section.

Well curvature is mainly caused by uneven rock resistance to fracture, and the curvature occurs in the direction where the fracture resistance is least. Therefore, by artificially creating the necessary resistance and limiting the care of the tool, it is possible to keep the curvature of the well within acceptable limits. Such conditions are created when drilling adjoining and overlapping wells. For such wells, it is possible to manufacture a device for parallel drilling, for example, according to A.S. USSR No. 374451. Using this device, drilling is carried out by a conductor, which is placed in a previously drilled well.

However, it should be emphasized that when drilling large-diameter wells, well curvature when drilling shallow wells in relatively uniform rocks is less likely. As a means of reducing curvature, it is possible to consider laying a drilled well with empty rock after enrichment or overburden rocks before drilling an adjacent well.

An analysis of the known methods for developing tube-shaped and other fields shows that the proposed method is a combination of drilling wells for various purposes, namely drilling exploration wells and large diameter wells with core recovery according to the proposed scheme. With this combination that we offer, it becomes possible to more accurately design the technical and technological side of drilling large diameter wells than according to geological exploration data. According to these data, it is impossible to determine the rational core length of large diameter and to more reasonably choose the type of drill bit and optimize the parameters of the drilling mode. We believe that due to the consistent drilling of these wells during the development of tube-shaped deposits, the proposed method for the development of mineral deposits in comparison with the prototype has the following advantages:

- the rational type of the drill bit and the parameters of the drilling mode for each large-diameter well are determined from the cores of the auxiliary well drilled at its center;

- there is the possibility of choosing the method and type of device for separating the core of a large diameter well from the array and the location (depth of drilling) of this compartment for the strength and fracture of the core of the auxiliary well;

- in the absence of permafrost, the massif of rocks is softened with surfactant solutions to a greater depth, due to their prolonged action without increasing the length of the main cycle of mining.

All this allows us to argue that our proposal has novelty and significant differences, because new properties are not an arithmetic sum of the properties of each individual development method and are not simply a consequence of the development of the prior art.

Figure 1 shows the implementation diagram of the proposed development method; figure 2 - sequence of implementation of the proposed method of extraction:

a) drilling an auxiliary well;

b) core drilling of large diameter;

c) laying the cavity of a large diameter well.

The method is as follows. After overburden of the field, the excavation field is divided into a grid with rhombic cells with sides and a short diagonal equal to the diameter (D) of the large-diameter working well 1. First, an auxiliary well 2 with a diameter of at least 93-112 mm is drilled in the nodes with core extraction, then, in the absence of permafrost, a surfactant solution is poured into the well. The core is determined by the express method the strength and drillability of kimberlite 3 (Fig. 2), its fracture, photographed and shipped for enrichment. The core can be stored until the end of drilling a large diameter working well. According to the obtained data, a large-diameter crown 4 is selected, the method and type of device for separating the core 5 of the working well 1 from the array, the depth (core length 5) and the drilling mode parameters of the large-diameter working well 1, concentric auxiliary well 2 are set.

According to these data, the geological and technical conditions and modes of drilling a large diameter well and core separation 5 from the array are projected, graphically presented as a geological section of a well with a planogram of core drilling operations. Such geological and technological maps are developed for each well. After that, drilling of a large diameter well begins and, having reached a predetermined drilling depth, the core is torn off, and the core pipe 6 with the core is lifted up, where it is laid in a special place equipped with core extraction means. If necessary, according to the results of drilling, the drilling modes are corrected, as well as the methods and means of separating the core from the array. The next core is drilled in the same way, and so on, until the planned drilling depth is reached. If the well has no deviation from verticality, then it is laid with a mixture of sand and gangue 7 after enrichment and overburden. If the well deviates from verticality, as described above, a conductor is used for drilling parallel wells, for example, as USSR No. 374451.

Information sources

1. Borodin A.A. On the possibility of excavating kimberlite ore with vertical cylindrical mine workings [Text] / A.A. Borodin, N.P. Borodin, A.A. Borodin // Actual problems of the development of kimberlite deposits: current status and prospects: collection. doc. / International scientific-practical conference "Peace-2001: July 1-9, 2001". - M., Publishing House "Ore and Metals", 2002. - S.339-345.

2. Russian patent No. 2090754, E21C 41/26. The method of open development of mineral deposits [Text] / L.N. Fedorov. - No. 94025105/03; declared 07/04/94; publ. 09/20/97, bull. No. 26. - 6 p.: Ill.

3. A.S. 67474 USSR, Class 5a, 37. Method for core removal after sinking with core drill [Text] / G.I. Bulakh (USSR). - No. 30-46 (343046); declared 02/19/1946; publ. 12/31/1946. - 4 s .; silt.

Claims (4)

1. A method of developing mineral deposits by drilling a core of large diameter, including opening a mineral, preliminary drilling an auxiliary well of small diameter and a main well of large diameter with drilling a core, separating the core from the array, lifting it to the surface and subsequent shipment, characterized in that it is excavated the field is divided into a grid with rhombic cells, the sides and short diagonal of which are equal to the diameter of the main well, at the nodes of this grid, like the centers of drill holes, an auxiliary well with a diameter of at least 93-112 mm is drilled to the entire depth of the excavation field with core extraction, the rational type of the drill bit and the parameters of the drilling mode, the strength and fracture of the core, the method and type of device for separating it from the array and location (depth) of this compartment, then, with core extraction, drill the main borehole of large diameter, concentric to the auxiliary borehole. 2. The method according to claim 1, characterized in that the blasting of core of large diameter is carried out in the most destroyed part of the core, using core grabbing devices that overlap the core section. 3. The method according to claims 1 and 2, characterized in that the drilling of wells is carried out by a conductor, which is placed in a previously drilled well. 4. The method according to any one of paragraphs, characterized in that a surfactant solution is poured into wells drilled in rocks with a positive temperature.

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