Mud pulse telemetry synchronous time averaging system

Abstract

Apparatus and methods for removing the effects of directional drilling systems drilling fluid pulses to allow a MWD mud pulse telemetry system to operate without interference. The methodology is based upon Synchronous Time Averaging (STA). With STA, any pressure fluctuation that is cyclical (or synchronous) with a measurable event can be profiled and subsequently subtracted from a mud pulse telemetry signal. STA functions by placing a strobe in such a manner that the strobe is triggered for each cyclical event. The cyclical event in this disclosure is one (or more) revolution(s) of the drill string. If there is a pressure fluctuation that correlates to that cyclical event, it will be identified by a stable profile of that pressure fluctuation. This pressure profile is then used to remove the cyclical pressure fluctuation from the input mud pulse telemetry signal thereby allowing normal operation of the mud pulse telemetry system.

What is claimed is: 
     
         1 . A MWD mud pulse telemetry system for telemetering sensor data while operating a directional drilling system, the telemetry system comprising:
 (a) a telemetry section for measuring a composite pressure signal;   (b) a trigger sensitive to a stimulus and cooperating with a strobe to define a plurality of strobe increments; and   (c) a processor cooperating with said telemetry section
 (i) to algebraically sum increment composite pressure pulse signals measured during said plurality of strobe increments to define a cyclical pressure pulse component related to said directional drilling system, and 
 (ii) to combine said cyclical pressure pulse component with said composite signal to obtain a mud pulse telemetry signal component. 
   
     
     
         2 . The mud pulse telemetry system of  claim 1  wherein said stimulus comprises a predetermined azimuth point on a rotating element. 
     
     
         3 . The mud pulse telemetry system of  claim 1  wherein said stimulus comprises a signal generated by a clock. 
     
     
         4 . A method for mud pulse telemetering sensor data while operating a directional drilling system, the method comprising:
 (a) measuring a composite pressure signal with a telemetry section;   (b) defining a plurality of strobe increments with a trigger sensitive to a stimulus and cooperating with a strobe; and   (c) within a processor cooperating with said telemetry section
 (i) algebraically summing increment composite pressure pulse signals measured during said plurality of strobe increments to define a cyclical pressure pulse component related to said directional drilling system, and 
 (ii) combining said cyclical pressure pulse component with said composite signal to obtain a mud pulse telemetry signal component. 
   
     
     
         5 . The method of  claim 4  wherein said stimulus comprises a predetermined azimuth point on a rotating element. 
     
     
         6 . The mud pulse telemetry system of  claim 4  wherein said stimulus comprises a signal generated by a clock. 
     
     
         7 . A MWD logging system comprising:
 (a) a directional drilling system;   (a) a downhole mud pulse telemetry section for transmitting a signal component from a downhole sensor;   (b) a surface mud pulse telemetry section for measuring a composite signal comprising said signal component;   (c) a trigger responsive to an azimuth point on a rotating element and cooperating with a strobe to define a plurality of strobe increments; and   (d) a processor cooperating with said surface mud pulse telemetry section
 (i) to algebraically sum increment composite signals measured during said plurality of strobe increments to define a cyclical pulse component used to operate said directional drilling system, and 
 (ii) to combine said cyclical pulse component with said composite signal to obtain said signal component. 
   
     
     
         8 . The logging system of  claim 7  wherein said cyclical pulse component is normalized as a function of said definition of said plurality of said strobe increments. 
     
     
         9 . The logging system of  claim 7  further comprising a predetermined relationship for converting said signal component into a parameter of interest. 
     
     
         10 . The logging system of  claim 9  further comprising a recorder cooperating with said processor to generate a log of said parameter of interest. 
     
     
         11 . The logging system of  claim 7  wherein said directional drilling system comprises:
 (a) a bent sub cooperating with a drill string and drill bit; and 
 (b) a mud motor disposed within said bent sub; wherein
 (i) said drill string and said mud motor are operationally connected to said drill bit to operate said drill bit independent of rotation of said drill string, 
 (ii) said cyclical pulse component is used vary the rotational speed of said drill bit, and 
 (iii) said borehole is deviated by said periodic variation of said rotary speed of said drill bit. 
 
 
     
     
         12 . A MWD logging method comprising:
 (a) providing a directional drilling system;   (a) transmitting a signal component from a downhole sensor with a downhole mud pulse telemetry section;   (b) measuring a composite signal comprising said signal component with a surface mud pulse telemetry section;   (c) defining a plurality of strobe increments with a trigger responsive to an azimuth point on a rotating element and cooperating with a strobe; and   (d) with a processor cooperating with said surface mud pulse telemetry section
 (i) summing algebraically increment composite signals measured during said plurality of strobe increments to define a cyclical pulse component used to operate said directional drilling system, and 
 (ii) combining said cyclical pulse component with said composite signal to obtain said signal component. 
   
     
     
         13 . The method of  claim 12  further comprising normalizing said cyclical pulse component as a function of said definition of said plurality of said strobe increments. 
     
     
         14 . The method of  claim 12  further comprising converting said signal component into a parameter of interest with a predetermined relationship. 
     
     
         15 . The method of  claim 14  further comprising generating a log of said parameter of interest with a recorder cooperating with said processor. 
     
     
         16 . The method of  claim 12  wherein said directional drilling system comprises:
 (a) a bent sub cooperating with a drill string and drill bit; and 
 (b) a mud motor disposed within said bent sub; wherein
 (i) said drill string and said mud motor are operationally connected to said drill bit to operate said drill bit independent of rotation of said drill string, 
 (ii) said cyclical pulse component is used vary the rotational speed of said drill bit, and 
 (iii) said borehole is deviated by said periodic variation of said rotary speed of said drill bit.