DTH (Down-the-Hole) hammer drilling for water wells is an efficient and reliable technology with promising applications. It has many advantages and has been through which people have created many new processes, methods, and equipment. In this article, we’ll introduce the advantages of DTH hammer drilling and how to choose the equipment for drilling water wells.
What is a DTH (Down-the-Hole) hammer?
DTH (Down-the-Hole) hammer drilling employs the force generated by compressed air to impact rocks through the DTH hammer. With the assistance of pressure and rotation from the drill jumbo, the process involves continuous impacts and rotations. The crushed rock powder is blown away by the working exhaust gas of the DTH (Down-the-Hole) hammer and the central exhaust gas, thus gradually forming holes.
Advantages of DTH hammer drilling
DTH hammer drilling not only addresses the fundamental challenge of utilizing water in drilling construction within arid and water-scarce regions but also offers several advantages:
- Simplicity of Drilling Rig Usage: The drill jumbo is straightforward to operate, requiring only devices for air supply, rotation, pressurization, and lifting.
- High Efficiency with Impact Drilling: Utilizing impact drilling and air cleaning results in rapid progress, high efficiency, and extended rock drilling tools’ service life.
- Preservation of Hole Wall and Rock Formation: The intact hole wall ensures that the rock formation is shielded from erosion and damage caused by liquid media. This preservation allows the maintenance of the original structure and natural permeability, contributing to high well quality.
- Low Axial Pressure Requirement: The drilling process necessitates minimal axial pressure, coupled with low rotation speed, resulting in low torque, reduced power consumption, easy disassembly of the drill bit, and extended service life.
- Effective Response to Water Inrush: During water layer drilling, DTH hammer drilling exhibits a noticeable response to water inrush and leakage. This characteristic facilitates hydrogeological recording, timely measurement of water inrush, and a significant reduction in well-cleaning time.
- No Leakage Issues in Formations with Severe Leakage: In formations with significant leakage, as long as powder discharge remains unaffected, DTH hammer drilling eliminates leakage problems.
- Reducing the auxiliary workload: DTH hammer drilling eliminates the need for recycling and processing flushing media, reducing auxiliary workload and simplifying cold-proof measures for winter construction.
How to choose equipment for drilling water wells?
DTH hammer
Choosing the appropriate model for the DTH hammer is crucial, and it should be based on the specific geological conditions of the drilling site and the requirements for the completed well. Typically, the selection involves opting for a model with specifications falling within the diameter range close to the wellbore. The high-air pressure valveless type DTH hammer is often a preferred choice.
Here are the considerations for choosing the high-air pressure valveless DTH hammer:
- Proportional Drilling Speed: The drilling speed of the DTH hammer is directly proportional to the air supply pressure. Higher air pressure generally leads to increased drilling speed.
- Importance of Air Pressure: Air pressure is a critical factor determining the performance of DTH hammers. It is recommended to select a high-pressure DTH hammer within the capability of the air compressor to maximize drilling efficiency.
- Working within Specified Wind Pressure Range: Once a specific down-the-hole impactor is selected, it is imperative to ensure that the drilling tool operates within the manufacturer’s specified wind pressure range. Operating outside this range, whether too low or too high, can lead to malfunctions and potential damage to the equipment.
In summary, selecting the appropriate DTH hammer model involves considering the drilling site’s geological conditions, the desired well specifications, and the air compressor’s capacity. The aim is to achieve optimal drilling efficiency by operating within the recommended air pressure range of the chosen DTH hammer model.
Air compressor
In DTH hammer drilling, the air supply pressure of the air compressor is evaluated based on two primary considerations. Firstly, it involves delivering the necessary pressure to the selected DTH hammer, including accounting for pressure loss from the air compressor to the DTH hammer and further through the removal of rock chips from various parts of the hole. Secondly, the air pressure necessary for the chip removal cycle or the exhaust resistance that the DTH hammer must surmount for regular operation. This resistance is also affected by the drilling depth, the size of the annulus between the drill pipe and the hole wall, the height of the water column and the amount of water inflow, and the particle size of the cuttings during the circulation process. Consequently, when opting for an air compressor pressure setting, it’s imperative to consider these two factors and ensure a sufficient reserve is incorporated.
The air supply volume of the air compressor is mainly determined based on the concentration of the cuttings produced, the particle size of the cuttings, the structure and parameters of the rock drilling tool, and the conditions in which the cuttings move near the bottom of the hole and along the purge space.
When choosing the air supply capacity of the air compressor, initially compute the air consumption necessary for chip transport and then compare it with the performance parameters of the chosen DTH hammer. Should the air consumption necessary for chip transport exceed that required by the DTH hammer, the elevated air consumption takes precedence as the decisive factor. Conversely, the air compressor’s air consumption is selected in alignment with the DTH hammer’s air consumption if it exceeds the chip transport requirements.
Drill jumbo
DTH hammer drilling does not have strict requirements on the drill jumbo. Generally speaking, all kinds of drill jumbos can use DTH hammer drilling. Considering the structural performance characteristics of the drill jumbo, opting for a power head drill jumbo equipped with essential components such as a foam pump, oil injector, water storage tank, and oil storage tank is preferable.
The choice of drill jumbo directly affects the increase or decrease of auxiliary time and the working intensity of the operator, so if possible, try to choose an advanced drill jumbo.
Drill pipe
The drill pipe stands as a crucial tool in the drilling process, steering the DTH hammer’s rotation and facilitating the conveyance of compressed air to the DTH hammer. During the drilling process, the stress on the drill pipe is intricate, encompassing tension, compression, torsion, and bending stresses. Consequently, the drill pipe is susceptible to damage and constitutes one of the components prone to wear and tear.
Selecting the drill pipe diameter entails maintaining a specific proportion to the hole diameter. For example, pairing a well with a drilling diameter of 155mm with a drill pipe of 114mm or 127mm diameter is a sensible practice. Utilizing a single drill pipe specification across various hole diameters is highly irrational and poses significant safety risks. At the same time, the improper ratio of drill pipe diameter to hole diameter can significantly impact air consumption.
By selecting the appropriate water well drilling equipment, we can further improve the efficiency and service life of the DTH hammer. In the future, there remains a necessity to continue refining and optimizing this technology, alongside reinforcing training initiatives and expanding its application to more effectively align with and address market demand.
