Pressure pulse generator for MWD
A pressure pulse generator to generate pressure signals in drilling fluid for transmission to surface includes an outer housing having an inlet and an outlet for supply to the drilling assembly; a control element slidably mounted in the housing for opening and closing said inlet, the element being operative to generate a pressure pulses when it closes; a control passage extending through the element and closable by a valve element arranged to be exposed to the pressure in the passage; and an actuator assembly connected to the control element. The control element moves upon activation relative to the inlet to generate a pulse. When deactivated, it blocks the flow through the passage so that all of the fluid bypasses via the inlet.
1. A pressure pulse generator for use in transmitting pressure signals to surface in a fluid-based drilling system, said generator being arranged in use in the path of a pressurized fluid to operate a drilling assembly and being operative, upon actuation, to generate pressure signals in such fluid for transmission to surface pressure monitoring equipment, in which the pulse generator comprises:
an outer housing positionable in the path of the supply of pressurized fluid, said housing having an inlet arrangement for admitting a portion of the fluid to the interior of the housing, and an outlet arrangement for discharging fluid from the interior of the housing for supply to the drilling assembly;
a control element slidably mounted in the housing for movement between an open and a closed position with respect to said inlet arrangement, said control element being operative to generate a pressure pulse in the supply of pressure fluid when the control element takes-up the closed position;
a control passage extending through the control element and closable by a valve element arranged to be exposed to the pressure of the fluid in the passage; and
an actuator assembly which is connected to the control element and which, upon actuation, moves the control element relative to the inlet arrangement in order to generate a pressure pulse in the fluid for transmission to the surface, said actuator assembly also, when deactivated, blocking the flow of fluids through the control passage so that all of the fluid flows as by-pass flow via the inlet arrangement, in which the actuator assembly includes a pilot valve which is connected via a first mentioned actuator to be moved between an open and the closed position with respect to a valve seat in order to activate or deactivate the pulse generator, said pilot valve being connected to a secondary valve via a further actuator, said secondary valve blocking flow through the control passage when the first mentioned actuator is deactivated.
2. A pressure pulse generator according to claim 1 , in which the pilot valve is connected to the first mentioned actuator via a lost-motion connection.
3. A pressure pulse generator according to claim 1 , in which the first mentioned actuator connected to the pilot valve comprises a first actuator connected to an electromagnetic actuator, a second actuator connect to the pilot valve, and a connector between the first and second actuators.
4. A pressure pulse generator according to claim 1 , in which the inlet arrangement comprises a fixed ring mounted internally of the housing and which defines an internal entry passage for fluid between itself and said moveable control element.
5. A pressure pulse generator according to claim 4 , in which the ring defines, or includes a by-pass port.