Method and system for transmitting information in a jet drilling system

Abstract

An abrasive jet drilling system is employed for transmitting information from a downhole location to a surface location. A jet drilling system is provided, with a drill string extending from surface to a downhole location in a borehole. A fluid flow with a mixture of drilling fluid and a quantity of abrasive particles is generated in the drill string. The quantity of abrasive particles in the mixture is modulated in dependence of information obtained regarding a downhole condition, to generate data pulses downhole which are detected at surface. A transmitted downhole condition is determined based on the detected data pulses.

1 . A method for transmitting information from a downhole location to a surface location in an abrasive jet drilling system, comprising the steps of:
 providing a jet drilling system, comprising a drill string extending from surface to a downhole location in a borehole;   generating a fluid flow in the drill string, the fluid flow comprising a mixture of drilling fluid and a quantity of abrasive particles;   obtaining information regarding a downhole condition;   modulating the quantity of abrasive particles in the mixture in dependence of said information, to generate data pulses downhole;   detecting said data pulses at surface;   determining a transmitted downhole condition based on the detected data pulses.   
     
     
         2 . The method of  claim 1 , the drill string being provided with a jetting head at a downhole end thereof, the jetting head comprising at least one jet nozzle;
 the method comprising the steps of:
 rotating the drill string at a selected rotational speed; 
 expelling the fluid flow from said jet nozzle; 
 controlling a frequency of the generated data pulses to prevent correlation between the selected rotational speed and said frequency. 
   
     
     
         3 . The method of  claim 1 , comprising the steps of:
 providing the drill string with a downhole recycling device for recycling of the abrasive particles; and   recycling the abrasive particles by said downhole recycling device.   
     
     
         4 . The method of  claim 1 , wherein the step of modulating the amount of abrasive particles includes varying the time duration of the data pulses. 
     
     
         5 . The method of  claim 1 , wherein the step of modulating the amount of abrasive particles includes varying the amplitude of the data pulses. 
     
     
         6 . The method of  claim 1 , wherein the step of modulating the amount of abrasive particles includes varying the frequency of the data pulses. 
     
     
         7 . The method of  claim 1 , wherein the step of modulating the amount of abrasive particles includes varying a particle release characteristic as a function of time. 
     
     
         8 . The method of  claim 1 , wherein the step of modulating the amount of abrasive particles includes providing a regular rhythm of data pulses. 
     
     
         9 . The method of  claim 1 , wherein the step of modulating the amount of abrasive particles includes omitting data pulses according to a predetermined coding. 
     
     
         10 . The method of  claim 1 , comprising the steps of:
 defining an operating window for rotation of the drill string, selected from a specific range of rotations per minute (RPM), a preselected increase of RPM, or a preselected decrease of RPM;   detecting the operating window;   upon detection of said operating window, starting the steps of modulating the amount of abrasive particles, detecting data pulses, and determining the downhole condition.   
     
     
         11 . The method of  claim 1 , comprising the steps of:
 defining an operating window of flow rate;   detecting said operating window of flow rate;   upon detection of said operating window of flow rate, starting the steps of modulating the amount of abrasive particles, detecting data pulses, and determining the downhole condition.   
     
     
         12 . The method of  claim 11 , wherein the operating window of flow rate includes a predetermined flow rate variation pattern. 
     
     
         13 . The method of  claim 1 , comprising the steps of:
 defining a weight-on-bit operating window;   detecting said weight-on-bit operating window;   upon detection of said weight-on-bit operating window, starting the steps of modulating the amount of abrasive particles, detecting data pulses, and determining the downhole condition.   
     
     
         14 . An abrasive jet drilling system for drilling a borehole, comprising:
 a drill string comprising a drill bit at a downhole end thereof;   a drive system rotating the drill string;   a pump for generating a fluid flow through the drill string, the fluid flow comprising a mixture of drilling fluid and an amount of abrasive particles;   at least one sensor sensing a downhole condition;   a modulating device at or near the drill bit for modulating the amount of abrasive particles in the fluid flow in response to the downhole condition as provided by the at least one sensor to generate data pulses downhole;   a detector at surface for detecting said data pulses; and   a controller coupled to the detector for determining a transmitted downhole condition based on the detected data pulses.   
     
     
         15 . The abrasive jet drilling system of  claim 14 ,
 the at least one sensor being selected from the group of: a flow sensor for sensing a flow condition of the drilling fluid, and a stress sensor for detecting a stress condition of the drill string or the drill bit;   the modulating device being coupled to said sensor and being adapted to be activated or de-activated based on the flow condition or the stress condition.   
     
     
         16 . An abrasive jet drilling system adapted for use in the method as described in  claim 1 . 
     
     
         17 . A method wherein communicating data from a downhole location to a surface location by using data pulses generated by modulating an abrasive particle concentration in a drilling fluid in an abrasive jet drilling system over time. 
     
     
         18 . The method of  claim 17 , wherein detecting the data pulses at the surface location. 
     
     
         19 . The method of  claim 18 , wherein the data pulses are related to downhole condition information. 
     
     
         20 . The method of  claim 19 , wherein determining the downhole condition information based on the detected data pulses at the surface location.