Pressure pulse generator for downhole tool

A pressure pulse generator consists of a stator 40 with an orifice 41 through which a stream of fluid can pass, and a rotor 43, arranged to rotate opposite the stator that also features an orifice 44 allowing a stream of fluid from the stator orifice to pass through as the rotor rotates. In a preferred embodiment, a communicating area 48 exists in the centre of the rotor and stator, meaning that as the rotor rotates, there is always a fluid flow path through the rotor and stator, allowing debris to pass through. Furthermore, a turbine (65 figure 11F) may be attached to the generator, so that the fluid exiting the rotor operates to turn the blades (80, 81, 82 figure 11F) of the turbine. In one embodiment, the pressure pulses generated by the system are sinusoidal.