What methods are used to set screens in air rotary drilling?

• A. Gravity placement
• B. Gravity placement, tremie pipe, and surge block
• C. Tremie pipe
• D. Surge block

Answer: (B)

Setting screens in air rotary drilling relies on getting the screen positioned correctly and creating a stable, proper-packed annulus around it. Three methods are commonly used to accomplish this: gravity placement, tremie pipe, and surge block.

Gravity placement uses the weight of the screen and attached equipment to lower the screen into its proper position and seat it against the formation or a gravel pack. This method relies on gravity alone to bring the screen to the right depth and establish a solid seating point.

A tremie pipe is employed to place gravel or grout around the screen from the bottom up. By keeping the material beneath the surface as the pipe progresses, it prevents mixing with drilling fluids and helps form a well-defined, intact gravel pack around the screen, which is essential for filtration and screen support.

The surge block is used to create and control pressure surges in the borehole during setting. This helps seat the screen firmly and helps the surrounding packing material consolidate around the screen, improving the seal and stability of the installation.

Together, these methods cover the key steps of attaching and seating the screen and forming a proper surrounding pack, which is why they’re listed as the standard combination for setting screens in air rotary drilling.