Mixing mud is one step of solids control processing. It mainly has two part: 1, add chemical materials into mud for changing or keep mud attitudes. 2. agitate mud to keep solids suspend in the drilling fluid.
But there are some mistakes would happen. So drilling contractors should open eyes to avoid them.
One common error, especially in small horizontal directional drilling projects, is to idle the mix pump down as soon as all of the bentonite goes in through the mixing hopper, and then add the polymers and additives. This yields lumps of bentonite that get coated by polymers and additives, which prevents bentonite from yielding/mixing. In addition, if a mixing hopper is poorly designed, it creates plugging problems that lead to more lost time and inadequately mixed drilling fluids. It is also important to remember that liquid polymers and additives should never be added through a mixing hopper, and that plugged mixing gun/tank stirring jet lines will cause bentonite and polymer to settle out in areas of the tank where agitation is inadequate.
It is very important to know the order of addition when mixing drilling fluids. Soda ash is always the first product to be added to mix water in order to raise the pH and neutralize and precipitate out contaminants such as calcium, so that the bentonite and polymers can perform as needed. Bentonite is mixed after soda ash (until fully yielded), before polymers and additives are added. If polymers are mixed before bentonite, the bentonite will not hydrate/mix properly and end up in large clumps on the bottom of a mix tank. Drilling detergent, if used, must be added last. Mixing drilling detergent before adding polymer can cause polymer to gum up and make a mess in the mix tank. Contractors should not hesitate to contact their drilling fluids supplier if they have any questions on mixing order.
Adequate mixing time is an essential component in mixing drilling fluids. Mixing time is determined primarily by the efficiency of mixing equipment and water temperature. Mixing time will be shorter in warmer temperatures, and much longer in colder temperatures. An easy way to determine if bentonite has fully yielded is to simply stick one’s hand into the mix tank and look for un-yielded lumps of bentonite. Another method is to check the top screen on a viscosity funnel for lumps of un-yielded bentonite when testing drilling fluids. If lumps of un-yielded bentonite are visible, allow additional mixing system time before introducing polymers and additives. As previously mentioned, the mixing pump plays an essential role in separating bentonite platelets, and the mixing pump should be running at full speed until the mixing process is completed.