ABSTRACT
56-mm wireline coring is widely used in geological exploration in China. It gives fast drilling in solid intermediate to hard rocks and is easy to handle and transport. In fractured strata core blocking happens, very frequently with a marked reduction in length per core run. To overcome these problems a small-diameter hydraulic impactor is attached to the inner tube assembly which transmits impulse forces to the bit. To make it possible for the small-diameter hydraulic impactor to fracture rock, the amplitude of impulsive stress wave must be chosen properly according to rock properties. An impactor controlled by one valve has been developed, which strikes the anvil at a high terminal impact velocity. The bearing block can expand and contract to make the impactor work more reliably. The main parameters of the impactor are: borehole diameter, outer diameter of impactor, wireline drill rods, impact force per blow, pump volume, and pressure drop.
