Downhole flow pulsing apparatus

Downhole flow pulsing apparatus comprising:

• a housing for location in a string, the housing defining a throughbore to permit passage of fluid therethrough;
• a valve located in the bore defining a flow passage and including a valve member, the valve member being movable to vary the area of the flow passage to, in use, provide a varying fluid flow therethrough;
• and
• a fluid actuated positive displacement motor having a rotor linked to the valve to rotate the valve member and to communicate transverse movement of the rotor to the valve member.

Downhole flow pulsing apparatus comprising:

• a housing for location in a string, the housing defining a throughbore to permit passage of fluid therethrough;
• a valve located in the bore and including first and second valve members each defining a respective axial flow opening and which openings are aligned to collectively define an open axial drilling fluid flow port through the valve, the first member being rotatable about a longitudinal axis of the housing to vary the alignment of the openings and thus vary the open area of said port between a maximum open area and a minimum open area to, in use, provide a varying flow therethrough and variation of the fluid pressure;
• and
• a fluid actuated positive displacement motor operatively associated with the valve for driving the valve member.