Choosing PDC Drill Bits: A Practical Guide for Drilling Contractors

A drill bit may look suitable in a product photograph but perform differently once it reaches the ground. For drilling contractors, the useful questions are practical: Will it match the formation? Can the rig operate it effectively? Will it deliver an acceptable cost per metre?

PDC drill bits are one option for rotary drilling. Understanding their cutting action and design differences helps buyers make a more informed choice.

Understanding PDC Cutting Technology

PDC stands for polycrystalline diamond compact. A conventional PDC cutter has a synthetic diamond layer bonded to a tungsten carbide substrate.

Mounted on the bit body, these cutters remove rock mainly through a shearing action as the bit rotates. Circulation helps cool the cutting structure and carry cuttings away.

However, the presence of diamond cutters does not make every PDC bit suitable for every formation. Cutter selection, blade layout, cleaning and operating conditions all affect performance.

Start with the Ground Conditions

Before selecting a bit, describe the formations expected throughout the drilling interval.

A general description such as “sandstone” may not be enough. Sandstone can vary in strength, abrasiveness and cementation. Fractures and transitions between layers also change the demands on the cutting structure.

Useful information includes:

• Rock types and the approximate thickness of each layer.

• Whether the ground is competent, weathered or fractured.

• Abrasive minerals or hard inclusions.

• Previous drilling results and photographs of worn bits.

Specialist PDC designs can address demanding formations, but their capabilities should not be assumed for a standard model. For hard or highly abrasive intervals, request a recommendation supported by comparable field experience.

Decide Whether You Need a Core Sample

The drilling objective determines the basic tool type.

PDC non-coring bits cut across the hole bottom without preserving a central rock core. They are used where creating the borehole is the main objective.

PDC core bits cut an annular path, allowing a central core to enter a compatible core barrel. For sampling work, confirm the required core diameter and barrel compatibility as well as the outside diameter.

A similar-looking thread or a matching outside diameter does not establish that two tools are interchangeable.

Look Beyond the Number of Wings

Three-wing, four-wing and five-wing configurations are available, but wing count alone does not identify the best bit.

Compare the cutter layout, blade profile, cleaning passages and gauge protection. Ask the supplier to explain how the proposed structure relates to your ground conditions.

More wings should not be treated as a promise of faster drilling or longer service life. The complete design and its operating environment matter more than an isolated feature.

Match the Bit to the Drilling Equipment

A formation recommendation is only part of the selection process. The proposed bit must also suit the rig and circulation system.

Before ordering, confirm:

• Bit diameter and exact thread connection.

• Available rotary speed, torque and feed control.

• Circulation method and available flow.

• Planned drilling depth.

• Any limitations encountered with the current tool.

Request operating guidance for the specific model. Avoid applying the same settings to every bit size or design.

Evaluate Results Before Placing a Repeat Order

For a trial, record metres drilled, drilling time, tool changes and the condition of the bit after use.

Compare similar ground intervals wherever possible. A lower purchase price does not necessarily mean a lower drilling cost, while a higher price does not guarantee better results.

For distributors, keeping a record of each customer's formation and equipment can also make repeat orders more consistent.

PDC Drilling Tools from Chenghui

Chenghui Drilling Tools Manufacturing Co., Ltd. manufactures PDC rock drill bits and PDC core bits for drilling applications including water wells, geothermal projects and geological exploration.

Our range includes drag, arc-profile and concave PDC designs, alongside other drilling tools and equipment. Custom requirements can be discussed according to the application.

For a suitable recommendation, provide the required diameter, connection, ground conditions and rig information. These details create a more useful starting point than choosing by appearance or price alone.