Patent ID: 8693284
Filing Date: 2014-04-08
Classification: E21B

Abstract:
1. A device for creating pressure pulses in the fluid of a bore hole, the device comprising: a housing for deployment in a bore hole, the housing having a chamber, and a piston mounted within the chamber for reciprocal motion along a longitudinal axis of the device, wherein the piston has first and second opposing faces and forms a first variable volume chamber between the first opposing face and a first end wall of the chamber, and a second variable volume chamber between the second opposing face and a second end wall of the chamber; a hollow valve linkage member, mounted on the second opposing face of the piston, and extending out of the second end wall of the chamber towards a fluid flow restriction in the bore hole, the hollow valve linkage member being in fluid communication with the bore hole fluid in the vicinity of the restriction via an opening in the hollow valve linkage member, and wherein the end of the hollow valve linkage member outside of the chamber forms a valve tip arranged to cooperate with the fluid flow restriction to create a pressure pulse in the fluid according to the position of the piston; a control port in the piston providing a fluid communication path between the hollow valve linkage member and the first variable volume chamber; biasing means, located in the chamber for biasing the piston away from the first end wall of the chamber, towards the fluid flow restriction; a port in the chamber wall providing fluid communication between the bore hole and the second variable volume chamber, wherein the pressure of fluid pressure in the second volume variable chamber acts against the biasing means; a pilot valve in the first end wall of the chamber, which when open provides a fluid communication path between the bore hole and the first variable volume fluid chamber, and when closed shuts the fluid communication path; and a controller for controlling the pilot valve; wherein the pilot valve comprises a valve seat and a valve member, wherein the valve seat comprises one or more valve ports through which fluid can flow, each valve port having an opening, and wherein the valve member is mounted for movement in a direction across the openings of the one or more valve ports to respectively reveal or block the one or more valve ports.