Hydraulically assisted pulser system and related methods
An asynchronous top-mounted pulser system for a measurement while drilling tool uses hydraulic flow, an obstruction, a piston-balance system, and an orifice, to create pressure pulses in drilling fluid, using hydraulic pressure on an obstruction in a main pulser to assist in closing the obstruction. A valve poppet is set above (upstream of) the orifice and is pushed by fluid flow towards a closing position. The piston-balance system, connected to the poppet and located downstream of the orifice in the main pulser, responds to net pressures on the upstream and downstream sides of the piston to move the poppet. The piston also responds to a spring assembly urging the piston downstream, and tending to move the valve poppet to a closed position. A servo pulser, located downstream of the main pulser, opens and closes a rotary shear servo valve-controlled bypass flow path to control the net pressures on the piston.
1. A transmitter assembly for a mud pulse telemetry MWD system for operation in an environment including a drilling fluid flow and an upstream direction and a downstream direction defined by the flow, comprising:
a main pulser, comprising;
a main orifice; and
a movable valve poppet having an upstream stroke position and a downstream stroke position;
at least part of said movable valve poppet being positioned upstream of said main orifice in said upstream stroke position;
said upstream stroke position forming a path for downstream drilling fluid flow to enter said main orifice; and
a main bypass conduit defining an unvalved fluid flow path within said main pulser by-passing said main orifice; and
a servo pulser configured to receive downstream drilling fluid flow from said main orifice.
2. The transmitter assembly of claim 1 :
said movable valve poppet comprising an upstream face and a downstream orifice portion; and
said upstream face being positioned upstream of said main orifice in said upstream stroke position.
3. The transmitter assembly of claim 2 :
said downstream orifice portion being positioned upstream of said main orifice in said upstream stroke position; and
said downstream orifice portion at least partially blocking said path for downstream drilling fluid flow to enter said main orifice in said downstream stroke position.
4. The transmitter assembly of claim 1 :
said downstream stroke position of said movable valve poppet substantially blocking said path for downstream drilling fluid flow to enter said main orifice.
5. The transmitter assembly of claim 1 :
said downstream stroke position of said movable valve poppet fully blocking said path for downstream drilling fluid flow to enter said main orifice.
6. The transmitter assembly of claim 1 :
said servo pulser comprising:
a servo bypass conduit, hydraulically connected to said main bypass conduit;
a servo valve for enabling and disabling fluid flow through said servo bypass conduit; and
wherein said servo bypass conduit provides a single fluid flow outlet for said main bypass conduit.
7. The transmitter assembly of claim 1 :
said main pulser further comprising
a piston; and
a shaft assembly;
said shaft assembly connecting said piston to said movable valve poppet; and
said main bypass conduit passing through said shaft assembly.
8. The transmitter assembly of claim 7 :
said piston being downstream of said main orifice.
9. A method of transmitting a mud pressure pulse in a pulse telemetry MWD system, comprising:
pumping drilling fluid downstream to a main pulser,
said main pulser comprising;
a main orifice;
a movable valve poppet; and
a main bypass conduit defining an unvalved fluid flow path in said main pulser by-passing said main orifice;
positioning at least part of said movable valve poppet upstream of said main orifice in an upstream stroke position;
said positioning in an upstream stroke position step comprising forming a path for downstream drilling fluid flow to enter said main orifice;
commanding a servo pulser to operate a servo valve; and
receiving downstream drilling fluid flow in said servo pulser from said main orifice.
10. The method of claim 9 :
said servo pulser comprising:
a servo bypass conduit, hydraulically connected to said main bypass conduit in said main pulser;
a servo valve for enabling and disabling fluid flow through said servo bypass conduit; and
wherein said servo bypass conduit provides a single fluid flow outlet for said main bypass conduit in said main pulser.
11. The method of claim 9 :
said pumping step comprising said drilling fluid creating a higher pressure zone on an upstream face of said movable valve poppet and a lower pressure zone on a downstream face of said movable valve poppet urging said movable valve poppet to close with respect to said main orifice;
said commanding step further comprising opening the servo valve, said opening step comprising;
opening a second fluid flow path in said servo pulser permitting fluid to escape from said main bypass conduit; and
reducing an upstream force acting on said movable valve poppet that urged said movable valve poppet to remain open with respect to said main orifice.
12. The method of claim 9 :
said movable valve poppet comprising an upstream face and a downstream orifice portion; and
said positioning in the upstream stroke position step comprising positioning said upstream face upstream of said main orifice.
13. The method of claim 12 :
said positioning in the upstream stroke position step further comprising positioning said downstream orifice portion upstream of said main orifice; and
positioning said downstream orifice portion to at least partially block said path for downstream drilling fluid flow to enter said main orifice in a downstream stroke position.
14. The method of claim 9 , further comprising:
substantially blocking said path for downstream drilling fluid flow to enter said main orifice in a downstream stroke position.
15. The method of claim 9 , further comprising:
fully blocking said path for downstream drilling fluid flow to enter said main orifice in a downstream stroke position.
16. A method of controlling a mud pressure pulse in a pulse telemetry MWD system, comprising:
pumping drilling fluid downstream to a main pulser including a main orifice therein;
controlling a movable poppet between an opening stroke position and a closing stroke position;
said controlling step comprising positioning at least part of said movable poppet upstream of said main orifice in said opening stroke position;
said controlling step comprising controlling bypass drilling fluid flow in a main bypass conduit;
said main bypass conduit defining an unvalved fluid flow path in said main pulser by-passing said main orifice; and
permitting drilling fluid flow to flow downstream to a servo pulser from said main orifice.
17. The method of claim 16 , further comprising:
said step of controlling bypass drilling fluid flow in the main bypass conduit comprising operating a servo valve in said servo pulser.
18. The method of claim 16 , further comprising:
said step of controlling the movable poppet further comprising reducing an upstream force acting on said movable poppet thereby unbalancing forces holding the movable poppet in said opening stroke position;
said step of reducing the upstream force comprising opening a single servo valve in said servo pulser to open an outlet fluid flow path;
said outlet fluid flow path hydraulically connecting said main bypass conduit to a low pressure zone.
19. The method of claim 16 :
said pumping step comprising said drilling fluid creating a higher pressure zone on an upstream face of said movable poppet and a lower pressure zone on a downstream face of said movable poppet urging said movable poppet to close with respect to said main orifice.