| Rotary mud rig | A rotating bit cuts the formation while drilling fluid circulates through the drill pipe and carries cuttings to the surface. | Water-supply wells, irrigation wells, and many municipal production wells. | Unconsolidated sand, silt, clay, and mixed formations; suitable for many sedimentary sequences. | About 100–600 m (330–1,970 ft), depending on rig capacity and formation. | Efficient in many soft and mixed formations; drilling fluid can help support the borehole walls. | Requires fluid handling and management; fluid may complicate sampling or be unsuitable in some sensitive formations. |
| Air rotary rig | Compressed air circulates down the drill string and returns cuttings through the annular space. | Water wells in hard-rock areas and exploratory boreholes where fluid use should be limited. | Competent rock and formations where air can effectively lift cuttings; some unstable formations may require casing. | About 100–600 m (330–1,970 ft), with depth limited by equipment, hole size, and geology. | Does not require conventional drilling mud; can provide rapid penetration in suitable formations. | Dust and noise control are important; water-bearing or unstable zones can reduce efficiency or require additional methods. |
| Down-the-hole (DTH) hammer rig | A pneumatic hammer positioned near the bit delivers repeated impacts while the drill string rotates. | Deep water wells and boreholes in hard, fractured rock. | Hard granite, basalt, and other competent formations; often used with air circulation. | About 100–1,000 m (330–3,280 ft), depending on hole diameter, compressor capacity, and ground conditions. | Effective penetration in hard rock and generally produces a relatively straight borehole. | Requires substantial compressed-air capacity; performance can decline in loose, water-saturated, or highly fractured ground. |
| Cable-tool percussion rig | A heavy bit repeatedly lifts and drops to break the formation; cuttings are periodically removed with a bailer. | Water wells in formations where a slower, adaptable drilling method is acceptable. | Many consolidated and unconsolidated formations, including some variable or water-bearing ground. | About 30–300 m (100–980 ft), varying considerably with formation and rig design. | Simple drilling-fluid requirements; can be useful where formation samples and water entries need to be observed. | Typically slower than rotary methods and may require more time for deep or large-diameter holes. |
| Hollow-stem auger rig | Helical augers advance the borehole; the hollow center can provide access for sampling or installing small-diameter wells. | Shallow monitoring wells, soil investigations, and some shallow water wells. | Soft to moderately stiff, relatively unconsolidated soils above groundwater or in stable formations. | Commonly about 5–60 m (16–200 ft), depending on soil, water conditions, and equipment. | Can support soil sampling and well installation without circulating drilling fluid. | Generally unsuitable for deep wells, hard rock, cobbles, or very loose formations below the water table. |
| Sonic drilling rig | High-frequency vibration combined with rotation advances a core barrel or casing through the formation. | Environmental monitoring wells, geotechnical borings, and projects requiring continuous samples. | Layered soils and mixed formations, including some difficult unconsolidated materials. | Often about 30–300 m (100–980 ft), depending on borehole diameter and ground conditions. | Can recover continuous, relatively undisturbed samples and reduce the need for drilling fluids. | Equipment is specialized and typically more costly to mobilize; very hard formations may slow progress. |
| Reverse-circulation rotary rig | Circulation carries cuttings upward inside the drill pipe, while fluid or air moves down the annular space. | Large-diameter production wells and high-capacity water-supply wells. | Unconsolidated and mixed formations where large boreholes are required. | About 100–600 m (330–1,970 ft), depending on hole size, circulation system, and geology. | Can efficiently remove cuttings from large-diameter holes and support high-yield well construction. | Requires specialized circulation equipment and substantial site space; setup and fluid management can be complex. |