This article, “What Types of Water Well Drilling Rigs Are There Based on Circulation Methods?”, introduces the characteristics of drilling rigs with different circulation modes. Based on the direction of cuttings circulation, they are classified into forward circulation and reverse circulation. To meet the needs of different application scenarios, not only do the paired drilling tools differ, but other detailed components—apart from the main structure of the rig—also vary. Additionally, reverse circulation drilling rigs are further divided into three categories: pump-suction type, air circulation type, and pump-suction type. Recently, one of our clients in the mining industry requested a custom-built air reverse-circulation drilling rig. Let’s take a closer look at their specific case.
First, let’s examine the advantages of this type of reverse circulation drilling rig from the perspectives of cuttings removal efficiency, operational adaptability, drilling efficiency, and cost control:
This client’s application involves non-ferrous metal exploration at depths of 300–500 meters. To ensure worker safety and reduce labor costs, there is a high demand for automation. Additionally, the project is located in West Africa, a region with limited water resources, which aligns perfectly with one of the key advantages of the air reverse circulation drill rigs mentioned above.
First, the general mobility options for drilling rigs include truck-mounted and crawler-mounted types. Since this client intends to use the rig in a mining site, we recommend a crawler-mounted rig to handle the complex terrain typical of such environments. Crawler-mounted rigs can be configured as split-type (separate components) or integrated-type (where the drill and air compressor are combined into a single unit). However, the integrated crawler-mounted design offers a higher degree of system integration but comes with significantly higher costs. Major brands such as Epiroc and Kaishan manufacture these types of models. If deep-hole exploration is a consideration, the author has only seen Epiroc offer similar models to date. If the budget is limited, we still recommend choosing a split-type model.
Although this client has selected a relatively deep drilling depth, not all mining exploration projects require such depth. The required depth varies depending on the country and the stratigraphic depth of the mineral resources. For example, another client of ours in Namibia only required an exploration depth of 200 meters. Exploration companies must conduct their own preliminary research to determine the appropriate depth for their specific project.
Additionally, this client has specific requirements regarding the rig’s weight, specifying that it must exceed 20 tons. Regarding this point, we have found through communication with past clients that this issue applies not only to reverse circulation drilling but also to water well drilling. When using an air compressor and down-the-hole hammer to drill, the pressurized air blows cuttings out of the borehole. This generates a certain amount of buoyancy; if the rig is too light, it may sway under the influence of buoyancy during drilling, thereby compromising the verticality of the borehole and the success rate of the operation. Additionally, the complete set of drilling tools is very heavy. Under the influence of gravity, this weight pulls the rig downward. While the pulling force provided by the rig’s hydraulic pump must be sufficient to hold the tools in place, the rig’s own weight is also crucial to prevent the tools from pulling the rig into a tilted or swaying position. Most Chinese-made drilling rigs weigh only 10–12 tons, or even less than 10 tons. Experienced manufacturers can reinforce the rig’s frame and increase its weight according to customer requirements.
Reverse circulation drilling rigs must be equipped with double-wall drill pipes, reverse circulation hammers, and drill bits specifically designed for reverse circulation. Common double-wall drill pipe diameters include 89, 102, and 114 mm. Since sufficient clearance is required for cuttings discharge, the drill pipe sizes used in air reverse circulation drilling are generally larger than those used in conventional water well drilling. The specific size to be selected depends on the drilling depth and borehole diameter. For depths of 100–200 m, a 102 mm diameter is recommended, and for 200–400 m, a 114 mm diameter is recommended, unless the customer has special requirements.
Previously, our client in Namibia required the rig to support both reverse circulation and conventional water-based drilling functions. Therefore, we designed a rotary head switching function and modified other settings to accommodate this. If you have specific feature requirements, please feel free to discuss them with us. Generally, features such as rotary head translation, lateral movement, panel folding, or even remote control and automation of the rig can be implemented as long as the budget allows.
Additionally, this client requested a 6-meter drill pipe automatic change system. We typically equip our rigs with a 3-meter automatic change system, which significantly reduces labor costs and improves efficiency. However, 6-meter drill pipes are extremely heavy, placing high demands on the rig’s configuration—requiring comprehensive upgrades to the engine, hydraulic pump, and rig chassis, effectively amounting to a custom-built rig. If your budget is limited and the drilling depth is less than 400 meters, we do not recommend using a 6-meter automatic change system.
D Miningwell, a 20-year drilling rig manufacturer and expert in drilling industry program planning, has served more than 30 countries. We sell not only products, but also services. We consider more details for our customers and reduce their worries. Choosing us is choosing to save your heart!
