Rotary Drilled Holes

Rotary Drilled Holes

In rotary drilled wells where the hole is first drilled to full depth before installing casing, there are numerous methods for completing the well with a screen, with techniques varying among drillers. The pipe and screen may be welded or screwed together into a single assembly and lowered into the well as one unit.

The use of outer casing is optional in these installations. When employed, the outer casing may either be permanently cemented in place or removed after the screen and inner casing are properly positioned. The telescoping method can also be utilized, with the casing being set either before or after drilling the final section of the hole.

For most applications, it is recommended to place stabilizing material such as sand or gravel in the annular space between the screen and borehole wall. This stabilizing material serves to fill voids in the well structure, thereby reducing the risk of sudden shifts in the native formation that could potentially cause screen collapse during the development phase.

Construction techniques and screen setting tools show considerable variation between different drilling operations. The most suitable methods and tools for a particular area can only be determined through practical field experience. However, there are several fundamental rules that should be followed in all completion operations: First, ensure the casing is securely anchored in its final position. Second, have accurate knowledge of the size distribution of the formation in the interval to be screened. Third, maintain proper control of the screen during the lowering process. Fourth, fill any significant voids in the annular space with appropriate stabilizing material. Fifth, create an effective seal between the screen top and well casing if they are not mechanically connected. Sixth, install a proper plug in the bottom of the screen if it was run into the well open-ended. These guidelines help ensure successful well completion regardless of the specific techniques employed.