Systems and methods for generating a downlink signal

Abstract

A flow regulation system for downlink communication includes a fixed flow valve and a variable flow valve on a discharge line. A pressure sensor is located between the fixed flow valve and the variable flow valve. A sinusoidal communication flow pattern in the drilling fluid is generated by adjusting the position of the variable flow valve based on measured valve pressures from the pressure sensor.

What is claimed is: 
     
         1 . A method for generating a downlink signal, comprising:
 determining a pressure drop across a flow regulation system, wherein the pressure drop is associated with a communication fluid flow;   determining a flow pressure upstream of a fixed choke based at least partially on the pressure drop and an outlet pressure of the flow regulation system;   measuring a measured valve pressure using a pressure sensor; and   adjusting a position of a variable flow valve until the measured valve pressure is equal to the determined flow pressure.   
     
     
         2 . The method of  claim 1 , further comprising determining an outlet pressure drop between the variable flow valve and an outlet to a drilling fluid pit. 
     
     
         3 . The method of  claim 2 , wherein determining the outlet pressure includes determining a fixed pressure drop across the fixed flow valve between the variable flow valve and the outlet. 
     
     
         4 . The method of  claim 3 , wherein the measured valve pressure is measured between the fixed flow valve and the variable flow valve. 
     
     
         5 . The method of  claim 2 , wherein determining the flow further includes determining the flow pressure based at least partially on the outlet pressure. 
     
     
         6 . The method of  claim 2 , wherein the pressure sensor is a first pressure sensor, and further comprising measuring the outlet pressure using a second pressure sensor. 
     
     
         7 . The method of  claim 1 , wherein adjusting the position of the variable flow valve includes adjusting the position of the variable flow valve to between a fully open position and a fully closed position. 
     
     
         8 . The method of  claim 1 , further comprising determining a communication position of the variable flow valve based on the variable valve pressure. 
     
     
         9 . The method of  claim 8 , wherein adjusting the position of the variable flow valve includes adjusting the position of the variable flow valve to the communication position. 
     
     
         10 . A method for generating a downlink signal, comprising:
 determining a flow pressure pattern upstream of a fixed flow valve for a communication flow pattern, wherein the flow pressure pattern is sinusoidal;   adjusting a position of a variable flow valve to generate the flow pressure pattern; and   generating a sinusoidal communication flow pattern of a drilling fluid based on the variable valve pressure pattern and the position of the variable flow valve.   
     
     
         11 . The method of  claim 10 , further comprising measuring a measured valve pressure, wherein adjusting the position of the variable flow valve includes adjusting the position of the variable flow valve until the measured valve pressure matches a variable valve pressure from the variable valve pressure pattern. 
     
     
         12 . The method of  claim 11 , wherein the measured valve pressure is measured between the variable flow valve and a fixed flow valve. 
     
     
         13 . The method of  claim 10 , wherein the variable valve pressure pattern changes at least one of amplitude or frequency. 
     
     
         14 . The method of  claim 10 , further comprising discharging a portion of the drilling fluid to a drilling fluid pit, wherein adjusting the position of the variable flow valve causes the portion of the drilling fluid to discharge in a discharge flow pattern. 
     
     
         15 . The method of  claim 10 , wherein the sinusoidal communication flow pattern includes substantially few frequencies at one or more sinusoidal transitions.