초록 ▼

An improved servo-driven pulser is disclosed, for use in measurement while drilling applications. In the pulser, a battery powered on-board DC electric motor is used to operate a servo-valve, which in turn adjusts internal tool fluid pressures to cause operation of a main valve to substantially redu

An improved servo-driven pulser is disclosed, for use in measurement while drilling applications. In the pulser, a battery powered on-board DC electric motor is used to operate a servo-valve, which in turn adjusts internal tool fluid pressures to cause operation of a main valve to substantially reduce mud flow to a drill bit, thereby creating a positive pressure pulse detectable at the surface. De-energizing the motor driving the pilot valve results in re-adjustment of internal fluid pressures, causing the main valve to reopen, thereby terminating the pressure pulse.

대표청구항 ▼

[ What is claimed is:] [1.] A pulser apparatus responsive to a signal from a downhole sensor for creating a positive pressure pulse in a column of drilling fluid being circulated through a drill string to a drill bit, said apparatus comprising:a wire-line retrievable assembly adapted to be received

[ What is claimed is:] [1.] A pulser apparatus responsive to a signal from a downhole sensor for creating a positive pressure pulse in a column of drilling fluid being circulated through a drill string to a drill bit, said apparatus comprising:a wire-line retrievable assembly adapted to be received within the bore of the drill string;seating means on the retrievable assembly for seating the assembly in the lower portion of the drill string, above the drill bit, in a position substantially blocking the flow of drilling fluid around said assembly, so that a major portion of the drilling fluid which flows to said drill bit will flow through an annulus between said assembly and said drill string and through a fluid passageway in said assembly, before being supplied to said drill bit;a main bore in the assembly having an inlet and outlet through which a major portion of the drilling fluid which flows to said bit may flow, said inlet for said main bore being in communication with said annulus and the outlet of said main bore being in communication with said drill string below said assembly;main valve means in said assembly for selectively restricting the flow of drilling fluid through said main bore, said main valve means comprising,orifice means defining a main orifice in said main bore,a valve tip in said main bore above said main orifice and adjustable toward and away from said main orifice to adjust the amount of drilling fluid flowing through said main bore;a main valve spring for urging said main valve tip toward said main orifice,a main valve piston connected to said main valve tip by a main valve stem,a cylinder in surrounding relationship to said main valve piston and comprising an upper chamber above said main valve piston and a lower chamber below said main valve piston;a first fluid passageway in said assembly having an inlet in communication with said main bore and an outlet in communication with said upper cylinder chamber for supplying drilling fluid at a pressure substantially equal to the pressure in said main bore below said main valve tip to said upper cylinder chamber;a second fluid passageway in said assembly having an inlet in communication with said annulus and an outlet in communication with said upper cylinder chamber for supplying drilling fluid at a pressure substantially equal to that of the drilling fluid in said annulus to said upper cylinder chamber;pilot valve means in said assembly for selectively closing said second fluid passageway responsive to a signal from said sensor; anda third fluid passageway having an inlet in communication with said annulus and an outlet in communication with said lower cylinder chamber for supplying drilling fluid at a pressure substantially equal to the pressure in said annulus to said lower cylinder chamber;said main bore, said inlet to said main bore, said main valve tip and said orifice means being so configured, and said main valve tip being adapted to be so positioned with respect to said orifice means, when said main valve means is open, that the flow of drilling fluid through said inlet to said main bore, around said main valve tip and through said orifice means produces a first fluid pressure in said main bore at said inlet to said first fluid passageway, which first fluid pressure is lower than the annulus fluid pressure at said inlets to said second and third fluid passageways,whereby, when said pilot valve is closed, said first fluid pressure will be communicated through said first fluid passageway to the said upper chamber of said cylinder while said higher annulus fluid pressure will be communicated through said third fluid passageway to said lower cylinder chamber, creating a pressure differential across the main valve piston which is sufficient to overcome the closing effect of said main valve spring, so as to retain said main valve open and, when said pilot valve is opened responsive to said signal, said annulus fluid pressure will be transmitted through said second fluid passageway to said upper cylinder chamber, reducing the pressure differential across said main valve piston sufficiently to permit said main valve spring to cause said main valve tip to move toward said main orifice, so as to reduce the flow of drilling fluid through said main bore and create a positive pressure pulse in said drilling fluid in said drill string above said assembly.