Rotary pulser and method for transmitting information to the surface from a drill string down hole in a well

摘要

A rotary pulser for transmitting information to the surface from down hole in a well by generating pressure pulses encoded to contain information. The pulser includes a rotor having blades that are capable of imparting a varying obstruction to the flow of drilling fluid through stator passages, depending on the circumferential orientation of the rotor, so that rotation of the rotor by a motor generates the encoded pressure pulses. A spring biases the rotor toward the stator so as to reduce the axial gap between the rotor and stator. When the pressure drop across the rotor becomes excessive, such as when increasing drilling fluid flow rate or switching from a high data rate to a low data rate transmission mode, the spring bias is overcome so as to increase the axial gap and reduce the pressure drop across the rotor, thereby automatically reducing the thrust load on the bearings.

主权项

1. A rotary pulser for transmitting information from a portion of a drill string operating at a down hole location in a well bore, said drill string having a passage through which a drilling fluid flows, comprising:
a) a stator adapted to be mounted in said drill string and having at least one passage formed therein through which at least a portion of said drilling fluid flows; b) a rotor adapted to be mounted in said drill string proximate said stator, said rotor being rotatable into at least first and second circumferential orientations, said rotor imparting a different degree of obstruction to said flow of drilling fluid flowing through said stator passage depending on the circumferential orientation of said rotor, said first circumferential orientation providing a greater obstruction to said flow of drilling fluid than that of said second rotor circumferential orientation, whereby rotation of said rotor generates 1) a pressure drop in said drilling fluid across said rotor, and 2) as a series of pulses encoded with said information to be transmitted; c) a gap formed between said rotor and said stator, rotor and stator capable of relative displacement with respect to each other during rotation of the rotor, wherein displacement of said rotor toward said stator reduces said gap, and displacement of said rotor away from said stator increases said gap; and d) a spring arranged so that deflection of said spring generates a biasing force resisting relative displacement between said rotor and said stator.