Rotary Drilling Rig Depth Capabilities for Different Work Scenarios

The maximum drilling depth of a rotary drilling rig is a critical specification, determined by the length of its Kelly bar or continuous drilling system, mast height, and hoisting capacity. Different work scenarios demand vastly different depth capabilities, from shallow urban foundations to deep bridge piers and geothermal wells. Here, we outline typical depth requirements for various scenarios and list specific rig models with their depth ranges.

1. Drilling Depth Requirements by Work Scenario

The required depth is driven by geotechnical conditions and structural design.

• Urban Low-Rise / Residential Buildings:
  • Typical Depth: 15 - 30 meters.
  • Reason: Piles need to reach stable bearing strata below superficial layers, often within moderate depths.
• High-Rise Buildings & Industrial Plants:
  • Typical Depth: 30 - 60 meters.
  • Reason: Heavier loads require deeper foundations to reach competent soil or rock, or to develop sufficient skin friction.
• Bridge & Viaduct Piers:
  • Typical Depth: 40 - 80+ meters.
  • Reason: Must penetrate through soft alluvial deposits near rivers to reach stable bedrock, and resist large lateral and vertical loads.
• Large Infrastructure & Wind Turbine Foundations:
  • Typical Depth: 25 - 50 meters.
  • Reason: Often use large-diameter, shorter piles grouped for stability; depth varies with soil profile and overturning moments.
• Geothermal Wells & Specialized Geotechnical Investigation:
  • Typical Depth: 100 - 200+ meters.
  • Reason: Requires reaching deep geothermal reservoirs or conducting deep soil sampling.

2. Rig Models and Their Depth Capabilities

Depth capability is a key differentiator between small, medium, and large rigs.

• Small/Medium Rigs for Urban Construction (Depth: ~20-50m):
  • XCMG XR150: Max drilling depth ~46m (with 4-section Kelly bar).
  • SANY SR200: Max drilling depth ~52m.
  • Soilmec SR-30: Max drilling depth ~48m.
  • Zoomlion ZR160: Max drilling depth ~44m.
• Large Rigs for High-Rise & Bridge Piers (Depth: ~50-90m):
  • XCMG XR280: Max drilling depth ~80m (with 5-section bar).
  • SANY SR280: Max drilling depth ~86m.
  • Bauer BG 28: Max drilling depth ~70m+ (depending on tool).
  • Soilmec SR-60: Max drilling depth ~78m.
• Extra-Large / Super Deep Rigs (Depth: 90m+):
  • XCMG XR460: Max drilling depth ~120m+.
  • SANY SR460: Max drilling depth ~130m.
  • Bauer BG 48: Max drilling depth ~100m+ (can be configured for greater depths).
  • Sunward SWDM450: Max drilling depth ~110m.

3. Key Factors Influencing Achievable Depth

The rated maximum depth is theoretical; actual performance depends on several factors.

• Kelly Bar Type & Sections: Telescopic bars (3/4/5 sections) determine the practical depth. More sections allow greater depth but add weight and complexity.
• Soil/Rock Conditions: Hard rock or dense layers slow progress and may require different tools, potentially reducing effective depth range compared to soft soils.
• Hoisting Capacity & Pullback Force: Must be sufficient to lift the full length of Kelly bar, drill tool, and excavated soil from the maximum depth.
• Mast Height & Stability: Must accommodate the longest single bar segment during handling and provide stability for deep drilling operations.

Drilling Depth Capability Reference Table

Conclusion: Matching a rig's depth capability to the project's geotechnical requirements is paramount. For most urban construction (15-50m), medium-sized rigs like the XCMG XR150/XR220 or SANY SR200 are sufficient. For high-rises and standard bridges (40-80m), large rigs such as the XCMG XR280, SANY SR280, or Soilmec SR-60 are required. For mega-projects requiring depths over 90m, extra-large rigs like the SANY SR460, XCMG XR460, or Bauer BG series must be deployed. It is crucial to select a rig whose maximum rated depth exceeds the required depth with a safe margin, accounting for tooling and soil conditions.