Many drillers will tell you that the hardest ground to drill is reactive: oil-like clay, shale and mudstone. Swelling issues can cause you to lose the pipe you pull back, or your drill string and tools.
Swelling clays create too much hydrostatic pressure downhole and can cause frackouts or blow-outs. A loss of returns to the surface gives you the telltale sign of a problem. The primary issue? Most clays lie dormant just waiting for someone to offer a drink of water. Add drilling fluids and the party is on! As a driller you need to understand the conditions, risks and available solutions. The proper drilling fluids mix can proactively counter these aggressive ground conditions.