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Different methods are used to drill wells for accessing underground liquids, including rotary drilling, downhole hammering, and cable tool drilling. Rotary drilling uses a motor to rotate a bit and break through rock or shale, while downhole hammering uses a jackhammer powered by compressed air. Cable tool drilling involves repeatedly lifting and dropping a heavy bit attached to a cable. In areas with limited technology and shallow water tables, a sand point drill can be used.
A well is a system used to drill an artificial hole in the ground to access underground liquids. While the purpose of all well drilling is essentially the same, the methods of breaking through the various geological strata can vary. A water well driller can use one of three or more methods – rotary drilling, downhole hammering, or cable tool drilling – to penetrate sand, shale, clay and rock to reach an aquifer or water source. underground water.
When using a rotary well driller, a well driller attaches a bit made of durable material such as tungsten to the end of a drill string or series of pipes that extend from the wellhead on the surface to the wellhole bottom. . Rotary motion is provided to the bit via the drill string by a motor at the wellhead and, as the bit is rotated, it breaks rock or shale into small pieces. These small pieces, sometimes called cuttings, are carried up and out of the hole by circulating drilling fluid down the drill string pipes and to the surface from outside the well’s drilling system.
The drill bit and pipe of the well are cooled by the passage of the drilling fluid, and the walls of the well drilled through sand or silt are stabilized, preventing collapses. When it meets groundwater, the clear water travels up the well, allowing the well driller to identify the depth of the top of the water source. Typically, drilling continues beyond the first water entry, often to 100 feet (about 30.5 m) or more, to allow for fluctuations in the water table.
In large areas of hard rock, a jackhammer is often the drill of choice. An air line is run up the shaft and the compressed air supplies power for the jackhammer in the bottom hole. The compressed air is also used to help blow debris or clippings out of the hole.
The cable tool well drill has typically been replaced by the rotary well drilling system. In cable tool drilling, a heavy bit is attached to a strong cable and the bit is repeatedly lifted and dropped, cutting its way through the underground rock layers. Debris is periodically flushed out of the hole with a water hose.
In areas where technology is limited and water tables are close to the surface, a driven point or sand point can be used. A sand point drill is simply a series of short tubes joined with threaded ends terminating in a hardened steel point with a section of reinforced shield over the point. The screen allows for water pumping while blocking sand. The whole apparatus resembles a javelin or a spear.
The drive pipe is simply short sections of threaded steel pipe that connect when the sand point is driven into the sand with a driver post raised and dropped by the driller. Sand point well drillers are limited to use in essentially rock-free terrain. Despite the ease of use, the sand tip has limited water flow and is primarily for residential applications. This technology has been used extensively in the United States where conditions permit and is still widely used in many developing nations.
