Pressure pulse generator

Abstract

A pressure pulse generator for use in MWD operations in a drilling installation having a drillstring, a drilling bit, means for supply drilling fluid via the interior of the drillstring to the drilling bit, and an annulus between the drillstring and the wall of the bore hole being formed. The pressure generator generates a pressure pulse signal in the drilling fluid which transmits such signal to pressure monitoring equipment at the surface. The pressure pulse generator includes an outer housing which can be mounted in a drillstring component, and in which the operating components of the pulse generator are housed; a main valve having a valve operating chamber which allows drilling fluid to pass from the interior of the drillstring to the exterior when the valve is opened, and thereby to generator a pressure pulse signal that travels to the surface. A first pilot valve allows fluid in the operating chamber of the main valve to communicate with the drilling fluid in the annulus, and a second pilot valve controls flow of drilling fluid between the inside of the drillstring and the operating chamber of the main valve.

1 . A pressure pulse generator for use in MWD operations in a drilling installation ( 10 ) having a drillstring ( 11 ), a drilling bit ( 19 ), means ( 13 ,  14 ) for supplying drilling fluid via the interior of the drillstring ( 11 ) and to the drilling bit ( 19 ), and an annulus ( 16 ) between the drillstring ( 11 ) and the wall ( 12 ) of the borehole which is being formed, said pressure generator being operative to generate a pressure pulse signal in the drilling fluid, and to transmit such signal to pressure monitoring equipment ( 20 ,  21 ) at the surface, and in which the pressure pulse generator comprises: 
 an outer housing ( 30 ) which can be mounted in a drillstring component, and in which the operating components of the pulse generator are housed;    a main valve ( 256 ,  257 ) having a valve operating chamber which, when the valve is opened, allows drilling fluid to pass from the interior of the drillstring to the exterior, and thereby to generate a pressure pulse signal that will travel to surface;    a first pilot valve ( 116 ,  120 ) which is normally open, to allow fluid in the operating chamber of the main valve to communicate with the drilling fluid in the annular; and,    a second pilot valve ( 88 ,  89 ,  90 ) which is normally closed, to control flow of drilling fluid between the inside of the drillstring and the operating chamber of the main valve.    
     
     
         2 . A pressure pulse generator according to  claim 1 , in which the first and second pilot valves are electrically actuated valves.  
     
     
         3 . A pressure pulse generator according to  claim 2 , in which the actuators for the first and second pilot valves are arranged to be immersed in hydraulic oil to prevent access of the particulate drilling fluid to the sensitive actuator parts.  
     
     
         4 . A method of generating pressure pulse signals in a drilling fluid which is being supplied to a drilling installation ( 10 ) having a drillstring ( 11 ), a drilling bit ( 19 ), means ( 13 ,  14 ) for supplying drilling fluid via the interior of the drillstring ( 11 ) and to the drilling bit ( 19 ), an annulus ( 16 ) between the drillstring ( 11 ) and the wall ( 12 ) of he borehole which is being formed, and a pressure pulse generator installed in the drillstring; 
 in which the pressure generator comprises an outer housing ( 30 ) which is mounted in a drillstring component, and in which the operating components of the pressure pulse generator are housed;    a main valve ( 256 ,  257 ) having a valve operating chamber which, when the valve is opened, allows drilling fluid to pass from the interior of the drillstring to the exterior, thereby to generate a pressure pulse signal that will travel to surface;    a first pilot valve ( 116 ,  120 ) which is normally open, to allow fluid in the operating chamber of the main valve to communicate with the drilling fluid in the annulus; and,    a second pilot valve ( 88 ,  89 ,  90 ) which is normally closed, to control flow of drilling fluid between the inside of the drillstring and the operating chamber of the main valve;    in which a pressure pulse signal is generated in the drilling fluid by the following steps: 
 actuating the main valve ( 256 ,  257 ) through a sequence of events at successive time intervals;  
 closing the first pilot valve and disconnecting the piston of the main valve from the flow pressure drilling fluid in the annulus;  
 opening the second pilot valve, allowing access for high pressure fluid from the drillstring to the main valve piston, whereby the main valve consequently opens;  
 closing the second pilot valve, leaving the main valve position unchanged;  
 after a selected time interval reopening the first pilot valve, allowing the main valve operating chamber to vent to the lower pressure region of the annular outside the drillstring, and consequently the main valve reclosing and the system being restored to its original state.