Vortex controlled variable flow resistance device and related tools and methods

A method for running a drill string into a borehole of an oil or gas well, the method comprising:

• advancing the drill string into the borehole, wherein the drill string comprises a bottom hole assembly that includes a backpressure tool;
• wherein the backpressure tool comprises a vortex-controlled variable flow resistance device configured to produce alternating primary and secondary vortices, the secondary vortex being opposite in direction and weaker in strength relative to the primary vortex;
• and
• pumping fluid through the drill string to hydraulically operate the backpressure tool in the bottom hole assembly to produce alternating strong and weak pressure pulses in the drill string thereby reducing frictional engagement between the drill string and the borehole.

A method for running a drill string into a borehole of an oil or gas well, the method comprising:

• advancing the drill string into the borehole, wherein the drill string comprises a bottom hole assembly that includes a first backpressure tool and a second backpressure tool;
• wherein the first backpressure tool comprises a vortex-controlled variable flow resistance device configured to produce alternating primary and secondary vortices, the secondary vortex being opposite in direction and weaker in strength relative to the primary vortex;
• wherein the second backpressure tool comprises a vortex-controlled variable flow resistance device configured to produce alternating vortices that are opposite in direction and about equal strength;
• and
• pumping fluid through the drill string to hydraulically operate the first and second backpressure tool in the bottom hole assembly to produce alternating multi-frequency pulses in the drill string thereby reducing frictional engagement between the drill string and the borehole.