Study on Controlling Lost Circulation of Pilot Hole in Raise Boring by Using Fuzzy Ball Drilling Fluid

Abstract

The fuzzy drilling fluid can effectively solve the serious lost circulation problem in the surface layer, it can be used in the raise drilling. The fuzzy ball drilling fluid with the density of 0.9g/cm3 was prepared in the laboratory. With the driving pressure increases, researchers do the plugging experiment with & without 0.5MPa back pressure. The experiments show that in a back pressure condition, fuzzy ball drilling fluid can effectively plugging formation. Besides, fuzzy ball drilling fluid can effectively control the leakage without back pressure. In the process of GuiZhou LongAn raise boring, the surface layer of the hole leaked seriously with leak off rate of more than 40m3/h in the first 10m and once exceeded 100 m3/h.The field use Fuzzy ball drilling fluid on the well plugging. The circulation is rapidly established after the Fuzzy ball drilling fluid was injected into the well, and the leakage rate has been effectively controlled.In the raise drilling, the fuzzy ball drilling fluid can only control the leakage rate but can’t seal the leakage formation.