![]() ![]() If the mud is too thin, cuttings will not be brought to the surface and the drill bit and drill pipe may get stuck in the borehole by settling cuttings. It will also make it difficult to remove the mud from the borehole walls and adjacent aquifer during well development and rate of penetration is also potentially reduced. The thickness of the drilling fluid often needs to be adjusted during drilling by adding more water and/or removing some of the accumulated cuttings from the settling pit.įluid which is too thick will be difficult to pump and will cause unnecessary wear of the mud pump since cuttings will not have settled out of the mud before the mud is pumped back down the borehole. The desired results are obtained by properly designing the mud pits, controlling the viscosity and weight of the drilling fluid and adjusting the pump speed.ĭuring the drilling process, solids accumulate in the drilling fluid – especially when drilling silt, clay or weakly consolidated shale. After cuttings are brought to the surface, however, it is essential that they drop out as the fluid flows through the settling pit. The ability of a fluid to lift cuttings increases rapidly as viscosity (the degree to which a fluid resists flow under an applied force) and up-hole velocity are increased. It is, therefore, very important to understand the properties of drilling muds and their proper use: Drilling fluids must be mixed thick (viscous) enough to bring soil cuttings up from the bottom of the hole to the surface, yet not so viscous as to prevent their settling out in the mud pits. Cool and clean the drill bit and lubricate the bit, bearings, mud pump and drill pipe.ĭrilling mud is created by thoroughly mixing water with clay usually bentonite to a desired consistency.Seal the borehole wall to reduce fluid loss (minimizing volumes of drilling fluid is especially important in dry areas where water must be carried from far away).Create a film of small particles on the borehole wall to prevent caving and to ensure that the upward-flowing stream of drilling fluid does not erode the adjacent formation.Prevent cuttings from rapidly settling while another length of drill pipe is being added (if cuttings drop too fast, they can build-up on top of the bit and seize it in the hole).Allow cuttings to drop out in the mud pit so that they are not re-circulated (influenced by mud thickness, flow rate in the settling pits and shape/size of the pits).Lift soil/rock cuttings from the bottom of the borehole and carry them to a settling pit.Water remains the primary constituent of water well drilling fluids. Drilling mud is pumped down the hollow drill pipe through the by-bass hose to the drill bit, where it exits the pipe and then is flushed back up the borehole to the settling pits at surface. Drilling mud, also called drilling fluid is use for water borehole drilling. ![]()
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