Methods and Devices for Analog Downlinking of Drilling Commands

Abstract

Methods and systems for adjusting a drill direction continuously during a drill operation comprising the steps of: selecting a desired downhole response value; computing from a preset mathematical relationship a corresponding surface control value; setting the surface control variable to the desired surface control value; measuring the surface control variable continuously downhole and computing at downhole an averaged surface control value; computing a corresponding downhole response value from the averaged measured surface control value; and setting the downhole response variable to the computed downhole response value.

What is claimed is: 
     
         1 . A method for controlling a downhole tool in a drilling operation, the method comprising the steps of:
 selecting a desired first downhole response variable value;   computing a desired first surface control variable value corresponding to the desired first downhole response variable value according to a preset mathematical relationship wherein the preset mathematical relationship is accessible by one or more surface and/or downhole controllers;   setting the first surface control variable to the desired first surface control variable value;   measuring the first surface control variable at a bottom hole assembly and obtaining a plurality of measured values of the first surface control variable;   processing the plurality of measured values to determine a representative value for the first surface control variable;   computing a first downhole response variable value corresponding to the representative value for the first surface control variable of the plurality of measured surface control values according to the preset mathematical relationship; and,   controlling the downhole tool according to the computed first downhole response variable value.   
     
     
         2 . The method according to  claim 1  wherein determining the representative value is based on those of the plurality of measured values of the first surface control variable associated with a first window. 
     
     
         3 . The method according to  claim 2  wherein determining the representative value comprises processing the plurality of those of the measured values of the first surface control variable corresponding to the first window to remove outliers and determining the representative value for the remaining ones of the measured values of the surface control variable corresponding to the first window. 
     
     
         4 . The method according to  claim 2  further comprising the steps of:
 selecting a desired second downhole response variable value; 
 computing a desired second surface control variable value corresponding to the desired second downhole response variable value according to a second preset mathematical relationship; 
 setting the second surface control variable to the desired second surface control variable value; 
 measuring the second surface control variable at the bottom hole assembly and obtaining a plurality of measured second surface control values; 
 computing over a second window that is the same as or different from the first window a representative value of the plurality of second surface control variable values; 
 computing a second downhole response variable value corresponding to the representative value of the plurality of measured second surface control variable values according to the second preset mathematical relationship; and, 
 setting the second downhole response variable to the computed second downhole response variable value. 
 
     
     
         5 . The method according to  claim 4  wherein the second downhole response variable is a steering rate of the downhole tool, the second surface control variable is a drilling fluid flow rate or drilling fluid pressure or the second mathematical relationship comprises a mapping between a range of values of the steering rate and a range of values of the drilling fluid flow rate or drilling fluid pressure. 
     
     
         6 . The method according to  claim 1  wherein the representative value is an average value, a weighted average value, a median value, a root mean square (RMS) value, an exponential moving average value, or an output of a Kalman filter that filters the measured values of the surface control variable. 
     
     
         7 . The method according to  claim 1  wherein the first downhole response variable corresponds to a toolface angle of a drill bit. 
     
     
         8 . The method according to  claim 1  wherein the first downhole response variable is a steering rate of the downhole tool. 
     
     
         9 . The method according to  claim 1  wherein the first surface control variable is a rotational speed of a drill string of a drill rig. 
     
     
         10 . The method according to  claim 9  wherein the mathematical relationship comprises a mapping between a range of values of a toolface angle and a range of values of the rotational speed of the drill string. 
     
     
         11 . The method according to  claim 10  wherein the range of values of the toolface angle exceeds one full revolution. 
     
     
         12 . The method according to  claim 1  wherein the mapping is a repeating function with dead bands. 
     
     
         13 . An analog method of downlinking a plurality of downhole response variables to a bottom hole assembly during a drilling operation, the method comprising the steps of:
 selecting a desired plurality of downhole response variable values;   computing a desired respective surface control variable value corresponding to each of the plurality of desired first downhole response variable values according to respective preset mathematical relationships, wherein the mathematical relationships are accessible by one or more surface and/or downhole controllers;   setting each of the plurality of surface control variables respectively to the desired surface control variable values;   measuring each of the plurality of surface control variables downhole at or near the bottom hole assembly to obtain a time sequence of measurements of each of the plurality of surface control variables;   for each of the plurality of surface control variables computing over a respective window a representative value of a portion of the time sequence of measurements of the respective surface control variable corresponding to the respective window;   computing respective first downhole response variable values corresponding to the representative values for the respective surface control variables according to the respective preset mathematical relationships; and,   setting each of the downhole response variables to the respective computed downhole response variable values.   
     
     
         14 . The method according to  claim 13  comprising for each of the plurality of surface control variables computing over the respective window the representative value of the portion of the time sequence of measurements of the respective surface control variable corresponding to the respective window at a respective frequency. 
     
     
         15 . The method according to  claim 13  wherein determining the representative value for at least one of the surface control variables comprises processing the portion of the time sequence of measurements of the respective surface control variable corresponding to the respective window to remove outliers and determining the representative value for the remaining ones of the measured values of the surface control variable corresponding to the first window, wherein the representative value is an average value or a median value. 
     
     
         16 . The method according to  claim 13  wherein the respective preset mathematical relationships each comprise a mapping between a range of values of the respective downhole response variable and a range of values of the respective surface control variable. 
     
     
         17 . The method according to  claim 16  wherein at least one of the mappings is a discrete function. 
     
     
         18 . The method according to  claim 13  wherein one of the plurality of downhole response variables is a toolface angle of a drill bit of the bottom hole assembly. 
     
     
         19 . The method according to  claim 13  wherein one of the plurality of surface control variables is a rotational speed of a drill string. 
     
     
         20 . The method according to  claim 13  wherein one of the plurality of downhole response variables is a steering rate of the bottom hole assembly. 
     
     
         21 . The method according to  claim 13  wherein one of the surface control variables is a drilling fluid flow rate or drilling fluid pressure. 
     
     
         22 . An analog method of downlinking a toolface angle to a bottom hole assembly during a drilling operation, the method comprising the steps of:
 selecting a desired toolface angle value;   computing a rotational speed of a drill string (RPM) corresponding to the desired toolface angle value according to a preset mathematical relationship;   rotating the drill string at the computed rotational speed;   measuring RPM of the drill string at the bottom hole assembly to obtain a sequence of measured RPM values;   computing a representative value of the plurality of time-stamped RPM values obtained in a first window;   computing a toolface angle corresponding to the representative value according to the preset mathematical relationship; and,   setting a toolface angle of a steering system to the computed toolface angle value.   
     
     
         23 . The method according to  claim 22  further comprising the steps of:
 selecting a desired steering rate value; 
 computing a desired drilling fluid flow rate or pressure value corresponding to the desired steering rate value according to a second preset mathematical relationship; 
 setting the drilling fluid flow rate or pressure to the desired drilling fluid flow rate or pressure value; 
 measuring the drilling fluid flow rate or pressure at the bottom hole assembly and obtaining a sequence of measured drilling fluid flow rate or pressure values; 
 computing a representative value for the drilling fluid flow rate or pressure values obtained in a second window; 
 computing a steering rate corresponding to the representative value for the drilling fluid flow rate or pressure values obtained in the second window according to the second preset mathematical relationship; and 
 setting a steering rate of the steering system to the computed steering rate value.