What Is a Wellbore?

A wellbore refers to a vertical or inclined project that is excavated from the ground to the ore body during the construction of underground mining or underground engineering. The vertical project is called a vertical well and the inclined project is called an inclined well.

Wellbore

Vertical wellbore bedrock construction refers to the construction of wellbore below the topsoil or weathered rock. According to the nature of the rock formation that the wellbore passes, it is mainly constructed by drilling and blasting. According to the different drilling methods of the wellbore, the main construction procedures of the wellbore drilling blasting method include drilling blasting, grasping and lifting, unloading and discharging, and wall support.

The level of mechanization of the construction of the foundation shaft of the shaft in China has been greatly improved. The well drilling technology, which has the main contents of deep hole light explosion, large-scale equipment, mechanization of support and grouting to block dry water, has made great progress. It has made a brand-new appearance in the construction of vertical shafts in China, and provided a reliable material foundation and technical guarantee for accelerating the speed of well construction, improving labor conditions, and improving work efficiency.

1.Drilling work

In the whole drilling blasting work, the drilling man-hour takes the longest. Speeding up the drilling speed, increasing the depth of the eye, improving the quality of the eyelet, and improving the mechanization of the drilled hole are the main development directions. In order to meet the requirements of vertical shaft construction, the rock drill should have the characteristics of high drilling speed, large torque, strong adaptability and reliable operation.

2. Blasting work

The blasting work mainly includes the selection of blasting equipment and the determination of blasting parameters, and the preparation of blasting charts and instructions.

3. Rock loading work

Rock loading is the most important work in the shafting cycle of a vertical shaft. It is time consuming and heavy, accounting for about 50% to 60% of the total cycle time of the roadway. Therefore, improving rock loading efficiency and mechanization is the key to speeding up the construction of vertical shafts.

4. Promotion and exhaustion

In the construction of a vertical shaft, in order to eliminate the vermiculite on the working surface of the shaft, lowering equipment, equipment, and lifting operators, a lifting system should be installed in the shaft. This hoisting system is slightly modified and should also be able to serve the yard and roadway construction and permanent well equipment. Whether the selection of the drilling and hoisting system is reasonable will not only directly affect the drilling and installation operations and the drilling construction speed, but also affect the smooth development of the post-construction work.

The drilling and hoisting system is composed of a lifting container, a hook head coupling device, a hoisting wire rope, a crown wheel, a hoist, and a guide rope and a skid necessary for hoisting. During the drilling of the well, the lifting container is mainly a vermiculite bucket, and sometimes a container such as a bottom unloading bucket and a dropping frame is also used. When moving into the yard and roadway construction, the lifting container is changed from a bucket to a well cage.

When the vertical shaft is being excavated, in order to suspend the hanging plate, the wall formwork, the safety ladder, the hanging pump and a series of pipeline cables, the corresponding suspension equipment must be reasonably selected. Suspension system consists of wire rope, sky wheel and drilling winch.

Wellbore

When the roadway is driven in a thin coal seam, in order to ensure the working height of the roadway, the roof or bottom must be raised. Therefore, there are both coal and rock layers on the cross section of the roadway. When the rock layer occupies 1/5 4/5 of the working area, it is called coal-rock roadway. The construction method of coal-rock roadway is basically the same as that of rock roadway and coal roadway.

1.Drilling blasting

Drilling and blasting is a major process, the quality of which is good or bad, has a great impact on the progress of roadway excavation, specifications and quality, support effect, ergonomics and cost, so the best construction process parameters must be adopted to obtain the best Construction effect.

The main technology development trend of drilling blasting is the development of medium and deep hole, smooth blasting and fracture forming (notch) blasting technology. Increasing the depth of the eye, perfecting the straight-hole cutting method of deep holes, reducing the number of shot holes, accelerating the drilling speed and improving the blasting efficiency. Modern engineering uses the shortest drilling and blast man-hours per metre of roadway, the highest blasthole utilization rate, and light explosion quality standards to evaluate construction effects.

2. Rock loading and transportation

Loading and transportation are the processes with a large amount of labor and the longest cycle time in roadway tunneling. Generally, it can account for 35% -50% of the cycle time of tunneling.

Since the 1970s, China has successfully developed rake bucket rock loaders, side-loading rock loaders, crab claw rock loaders and vertical claw rock loaders. Among them, the rake bucket rock loaders developed according to the characteristics of coal mines have simple structures, The advantages of easy manufacturing, low cost, good reliability, and strong adaptability have become the main loading equipment for the mine tunneling in China.

In recent years, the supporting re-transportation equipment has also been continuously researched and improved. QZP-160 bridge transfer machines, SJ-80 and SJ-44 retractable tape conveyors, ZP-1 tape transfer machines, and S4 , S6, S8 shuttle mine cars and ILA, CCJ warehouse trains, and explosion-proof battery electric vehicles above 5t. Most of the above are equipment that transports vermiculite from the working surface. At the same time, belt conveyors, wire rope traction trucks and wire rope traction monorail cranes that can transport materials to the work have also been developed.

Inclined shaft

By the 1980s, the rapid construction of inclined shafts in China had formed mechanized operating lines and equipment matching methods with Chinese characteristics. The operation methods and labor organization have been further optimized, the work efficiency has been further improved, and construction technology has made great progress. After entering the new century, with the reform of the national system and the implementation of the contract system, the technology of inclined shaft construction has entered a brand new stage.

1.Drilling blasting

(1) Selection of rock drilling equipment

For the excavation of bedrock in inclined wells, a smooth blasting and slag-blasting blasting are used for the full section of the middle and deep holes. Guided rock drills are used for inclined well drilling. Although it helps to achieve deep hole light blasting, it takes a long time to relocate the rock drilling trolley. The use of drilling rigs cannot make the two main processes of drilling and rock loading Parallel operation; the hydraulic pneumatic leg rock drill produced has a faster drilling speed, but the work vehicle equipped at the rear affects the rock loading work.

(2) Determination of blasting parameters

Blasthole depth

In order to achieve medium and deep hole blasting, the blasthole depth is generally between 2.0 and 3.5 m. The average depth of the blasthole should be determined through experiments, verified according to working practices, and finally a reasonable blasthole depth should be determined.

Number of gun holes

The number of blastholes is determined by experiments or experience based on the size of the section of the inclined well, rock properties, and explosive performance, and is adjusted in practice to obtain a reasonable number of blastholes. It can also be estimated according to the method of determining the number of blastholes in level lanes.

(3) Grooving method and blasthole layout

To achieve smooth blasting of medium and deep holes, straight-line grooves or a combination of straight-line and oblique eyes must be used. Straight-cut trenching has been widely used in metal mines in the past, mainly for hard rock mining.

(4) Charge structure and blasting technology

The blastholes in the working face of the inclined shaft have a certain inclination angle, and the working face generally has accumulated water. Therefore, water-resistant explosives must be used. Water gel explosives or No. 2 water-resistant rock ammonium nitrate explosives are mostly used at the scene. In order to achieve a good blasting effect, the slotted eye should be continuously reversely charged with high-power explosives, and the peripheral eyes should be continuously reverse-charged with low-power explosives or small-diameter explosives, which is basically the same as the flat-loading, except The eye should increase the charge, and finally blast the bottom eye to achieve slag throwing.

2. Rock loading promotion

Rock loading and hoisting are the main links of inclined wellbore driving, which directly affect the driving speed. Both account for 60% to 70% of the driving cycle time. Therefore, the construction of inclined shafts at home and abroad has emphasized the degree of mechanization of rock loading and promotion and the comprehensive ability of supporting equipment.

3. Support technology

Inclined shafts are permanently supported. Prior to the 1970s, stone-masonry concrete slabs and concrete scaffolds were used for support. Anchor-shotcrete support was widely used. When using anchor and shotcrete support, we should focus on solving the problems of establishing a wellhead concrete mixing station, rationally controlling the wind pressure of the spraying work, reducing the wear of the conveying pipe, preventing pipeline breakdown, preventing and handling pipeline blockage. ^[5]