Vortex controlled variable flow resistance device and related tools and methods

摘要

A vortex-controlled variable flow resistance device ideal for use in a backpressure tool for advancing drill string in extended reach downhole operations, especially in horizontal wells. The shape, frequency and duration of the pressure waves generated by the device are controlled by the growth and decay of vortices in the vortex chamber(s) of a flow path. The flow path includes a switch, such as a bi-stable fluidic switch, for reversing the direction of the flow in the vortex chamber. The flow path may include multiple vortex chambers, and the device may include multiple flow paths, through which flow may be parallel or sequential. This device generates backpressures of short duration and slower frequencies approaching the resonant frequency of the drill string, which maximizes axial motion in the drill string and weight on the bit. Additionally, fluid pulses produced by the tool enhance debris removal ahead of the bit.

主权项

1. A downhole tool comprising a tool housing, wherein the tool comprises an insert captured inside the tool housing, wherein the insert defines four flow paths arranged circumferentially and so that fluid flows through the flow paths in parallel, wherein the insert comprises an elongate tubular structure with an upper flow transmitting section and a lower flow path section, wherein the tool further comprises a retrievable plug that diverts fluid through the four flow paths in the insert, wherein the plug comprises a upper plug member, a lower plug member, and a connecting rod therebetween, wherein the upper flow transmitting section comprises an open upper end with external splines and is sized to sealingly receive the upper plug member, and wherein the upper flow transmitting section further comprises sidewall extending from the upper end, the sidewall having flow passages therethrough, wherein the circumferentially arranged flow paths in the flow path section define an open center continuous with the inlets and the outlets of the flow paths and with the flow passages of the connection section, wherein the open center of the flow path section is sized to sealingly receive the lower plug member between the inlets and the outlets of the flow paths, whereby when the plug is received in the insert, fluid flow entering the tool flows between the external splines, through the flow passages in the sidewall, then into the inlets of each of the flow passages, and then out the outlets of the flow passage.