Drill bits in mechanical drilling

Drill bits in mechanical drilling

As we all know that drill bits are used for well drilling. Well drilling is the process of drilling a hole in the ground for the extraction of a natural resource such as ground water, brine, natural gas, or petroleum, for the injection of a fluid from the surface to a subsurface reservoir, or for subsurface formations evaluation or monitoring. Drilling for the exploration of the nature of the material underground (for instance in search of metallic ore) is best described as borehole drilling.

The earliest wells were water wells, shallow pits dug by hand in regions where the water table approached the surface, usually with masonry or wooden walls lining the interior to prevent collapse. Modern drilling techniques utilize long drill shafts, producing holes much narrower and deeper than could be produced by digging.

Different types of drill bits

The factors affecting drill bit selection include the type of geology and the capabilities of the rig. Due to the high number of wells that have been drilled, information from an adjacent well is most often used to make the appropriate selection.

Two different types of drill bits exist: fixed cutter and roller cone.

1. A fixed cutter bit is one where there are no moving parts, but drilling occurs due to shearing, scraping or abrasion of the rock. Fixed cutter bits can be either polycrystalline diamond compact (PDC) or grit hot-pressed inserts (GHI) or natural diamond.

2. Roller cone bits can be either tungsten carbide inserts (TCI) for harder formations or milled tooth (MT) for softer rock. The manufacturing process and composites used in each type of drill bit make them ideal for specific drilling situations. Additional enhancements can be made to any bit to increase the effectiveness for almost any drilling situation.

Drill bit selection

A major factor in drill bit selection is the type of formation to be drilled. The effectiveness of a drill bit varies by formation type. There are three types of formations: soft, medium and hard.

1. A soft formation includes unconsolidated sands, clays, soft limestones, red beds, and shale.

2. Medium formations include dolomites, limestones, and hard shale.

3. Hard formations include hard shale, calcites, mudstones, cherty limestones, and hard and abrasive formations.

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