UNDERGROUND CONSTRUCTION
TALKING MUD, FROM MIXING TO DISPOSAL Drilling fluid can be an important part of helping HDD crews work more efficiently
M
ud, or drilling fluid, can have an impact on your company. From selecting the right additives to choosing the right volume of fluid to pump to determining the most efficient way to dispose of the used slurry, managing mud is a skill that horizontal directional drilling (HDD) crews need to understand. Mud is key to making an HDD crew work more efficiently. It provides coolant for downhole electronics (sonde), suspends and displaces cuttings, reduces wear on tooling and aids with stability by reinforcing and maintaining the walls of the borehole. However, to do all of that, contractors and their crews need to understand the art and science behind using mud.
Start with the right additives
Bentonite is the staple drill additive for almost every HDD crew. While many bores can be completed with just bentonite alone, there are certain soil conditions where other drilling fluid additives can be helpful. • Working in nonreactive clay? Start with bentonite for primary filtration control. Users may also need to add soap or detergent to keep downhole tooling clean.
Modular mud reclaimers like Vermeer’s R250C can help cut water and additive usage for drilling operations. • Working in reactive clay? Bentonite should be used for primary filtration control with a PAC polymer for secondary control. If there are concerns about the clay swelling, a PHPA polymer can also be used. Drillers may also want to use a soap/detergent to prevent clay from sticking to your tooling. • Working in sand? Again, bentonite is an excellent primary filtration control agent, but a PAC polymer and/ or a larger-molecular-weight polymer
can also help with suspension. • Working in rock or fractured rock? Bentonite may be all that’s needed, but if cuttings aren’t making their way out of the drill hole, the crew may want to use a larger-molecular-weight polymer to aid with suspension. A secondary filtration control additive like a PAC polymer may also help.
Bagged versus premix additives
In recent years, liquid premixed
DON’T DIG IT.
When crews try to use less mud, cuttings don’t get flushed from the hole, which causes the material to build up around the drill string. drilling additives have found their way into the HDD industry. Drilling additive manufacturers have made mixing mud more convenient with premixed drilling additives for a wide range of soil conditions. These new liquid additives are giving HDD crews even more options to consider.
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In addition to making sure the right additives are being used, and that they are being thoroughly mixed to the appropriate viscosity, drillers need to make sure they are pumping the optimum amount of fluid through the drill string to maintain hole integrity and flush cuttings. Soil conditions, hole diameter and distance are all factors in how much fluid the driller should be pumping. The critical thing to remember is ensuring the drill operator is seeing returns that are in line with what’s being pumped into the hole. If the crew isn’t seeing the level of returns it