Selection of Drilling Rigs for Different Geological Conditions

Selection of Drilling Rigs for Different Geological Conditions

Choosing the right drilling rig is essentially matching the right "drilling tool" to different underground adversaries. The properties of underground soil and rock vary greatly, from soft sand to hard rock; no single drilling rig can efficiently handle all situations. Therefore, understanding the "strengths" of mainstream rigs and their compatibility with geological conditions is crucial for making correct decisions and ensuring efficient and economical projects.

In soft to medium-hard strata, such as common clay, sand, silt, and some highly weathered soils, rotary drilling rigs are usually the most efficient and economical choice. The working principle of this type of rig is similar to cutting soil with a rotating drill bit. It uses a drill rod to drive the drill bit to rotate at high speed, grinding up the soil and rock, while a water pump pumps clean water or prepared mud into the bottom of the hole, circulating the debris to the surface. This method results in fast drilling speeds, high-quality holes, and smooth hole walls, making it ideal for drilling agricultural irrigation wells or household wells tens to hundreds of meters deep, and is the most widely used type of rig.

However, when encountering hard rock layers, large pebble layers, or very dense strata, the cutting efficiency of rotary drilling rigs drops drastically, the drill bit wears out very quickly, and drilling may even become impossible. In these situations, percussion drilling rigs, with their completely different working principle, are needed. Their operation is more direct and powerful; one can imagine a heavy hammer (drill bit) being repeatedly lifted to a certain height and then dropped freely, relying on its enormous impact kinetic energy to crush the rock. Although its drilling speed in hard rock may not be as fast as that of rotary drilling in soft soil, its ability to break hard rock is unmatched by rotary drilling. Therefore, in mountainous areas dominated by bedrock such as granite and hard sandstone, or when it is necessary to penetrate thick layers of gravel to find water sources, percussion drilling rigs are a more reliable tool.

In reality, underground conditions are often complex and varied, frequently alternating between soft and hard rock or with unclear strata. To cope with this uncertainty and balance efficiency and adaptability, multi-functional drilling rigs have become the ideal choice. These devices typically integrate both rotary and percussion functions, and some can also provide high-frequency vibration. Operators can flexibly switch working modes in the cab based on the geological formations encountered in real time: using rotary drilling for rapid drilling when encountering soft soil, and immediately activating the impact function for breaking up hard rock. This "multi-functional" feature greatly reduces the trouble and cost of changing equipment mid-journey due to geological changes. Although the initial investment in the equipment itself may be higher, the overall benefits are significant in complex geological formations. Therefore, before selecting a model, it is essential to collect local geological data or refer to the construction records of nearby wells to identify the main "opponents," which is the first step in choosing the most suitable "tool."