20 FEBRUARY 2024 WorldWide Drilling Resource® Benefits of Mud Rotary Drilling Adapted from Information by Talon LPE Mud rotary drilling is an excellent technique for the environmental industry to construct groundwater monitoring wells. It will allow monitoring wells to be installed in the shortest amount of time, and allows operators to achieve superior penetration rates in very hard geological formations. Mud rotary drilling was developed during the late 19th and early 20th centuries. It is one of the main methods of drilling for water and oil in areas containing unconsolidated formations. With mud rotary drilling, fluid is pumped down a hollow drill pipe, called the kelly, and forced out of jets in the drill bit. The fluid carries drill cuttings through the hole and up to the surface, and the mud is reused - either through a mud containment system or pit. From there, a suction hose repumps the mud back into the kelly and bit. After the kelly has drilled all the way down, a joint of 20- or 40-foot drill pipe is used, starting the drilling process over again. As the joint drills deeper, more pipe is added until the hole is finished being drilled. Most drilling fluids used contain clay additives, in the form of bentonite, or polymer-based additives. Sometimes a combination of the two are used. This fluid acts as a borehole stabilizer to keep the structural integrity of the borehole in place by forming what is known as a wall cake. This added support allows more well depth. Mud rotary drilling offers some substantial benefits. It is one of the fastest and most efficient ways of drilling with efficient rigs producing hundreds of feet per day using mud rotary drilling techniques. It is also suitable for a wide range of soil conditions, for instance where air rotary drilling is not feasible, mud rotary drilling will get the job done. Like anything else, however, there are some drawbacks to using this method. Mud rotary drilling is slower than some other techniques, such as air rotary drilling. However, mud rotary drilling is more stable, offering more support to complete well construction. Air rotary drilling lacks the support of a mud column, causing borehole collapses in places of unconsolidated formations. If the drilling mud is not formulated properly, it may contaminate some of the well samples. Some compounds typically added to drilling fluids may also interfere with sediment samples. Mud rotary drilling can be the best choice for deep wells or wells completed into well-lithified rocks. When mud rotary drilling is used, wells are more productive than those drilled with other methods, plus, it also allows for larger diameter holes to be drilled quicker and easier than other forms of drilling. It is best suited for bedrock, sand, and gravel formations, as well as broken rock areas. It is actually the preferred method of drilling in sand and gravel formations. ENV
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