When it comes to the mining industry, core drilling is their main mode for exploration. For instance in the Western United States alone, core drilling for copper, gold as well as silver is something that is done all year round. The actual concept of this technique is quite simple. There is a rod that is attached to a diamond carbide bit that has an open end. The normal size and type of rod is called an NQ coring rod. This rod is measured in millimeters that usually has an outside diameter of 69.9mm and the inside diameter being 69.3mm or 2.75 inches by 2.72 inches. The whole idea is to have the bit spin fast enough to make a core that is then pushed up inside of the rod.
After the core drilling goes a few feet, the core is extracted by using what is known as a retrieval tool. So that they can keep the core intact and the bit cool, they use a bentonite drilling gel and water. As the diamond bit cuts out the core they want there are very fine drilling cuttings that are made. These fin cuttings can actually cause a lot of issues down inside the hole like broken cores, lost cores and premature wear on the bit. Since there is less than a .60mm of tolerance it is vital to keep the drilling fluid very clean. Clean fluid should be less than 9 pounds per gallon of mud weight and the sand content should be less than 1%.
To help out with the core drilling what is known as a mud puppy solids control unit is used to remove these fine cuttings. It does this by using de-sanding cones that let the fluid stay below 1% sand. Then there is a scalping screen desander that will help to manage the mud weight if it is done correctly. By making sure the mud weight is kept down it will let the miners use the minimal amount of drilling fluid needed to finish their job. When it comes to coring, it is vital to retrieve good cores and then move to the next hole and with the help of a mud puppy solids control system miners have a better chance of staying on schedule and having increased success drilling cores.