Downhole Event Detection

Abstract

A method for downhole event detection includes measuring a parameter of a wellbore using a first sensor of a drill string, and measuring the parameter of the wellbore using a second sensor of the drill string. The method also includes detecting, by surface equipment, an event in the wellbore based on a first set of measurements provided by the first sensor, and detecting, by the surface equipment, the event in the wellbore based on a second set of measurements provided by the second sensor. The method further includes assigning, by the surface equipment, a probability value to the event based on the event as detected in the first set of measurement values and the event as detected in the second set of measurement values.

What is claimed is: 
     
         1 . A drilling system comprising:
 a drill string and surface equipment coupled to the drill string, in which:   the drill string includes:
 a sensor array having first and second sensors distributed along a length of the drill string, the first and second sensors configured to: 
 measure a parameter of a wellbore; and 
 transmit measurement values representative of the parameter to the surface equipment; and 
   the surface equipment is configured to:
 detect an event in the wellbore based on a first set of measurement values received from the first sensor; 
 detect the event in the wellbore based on a second set of measurement values received from the second sensor; and 
 assign a probability value to the event based on the event as detected in the first set of measurement values and the event as detected in the second set of measurement values. 
   
     
     
         2 . The drilling system of  claim 1  wherein:
 the drill string includes a third sensor configured to:
 measure the parameter of the wellbore; and 
 transmit a third set of measurement values representative of the parameter to the surface equipment; 
 
 the surface equipment is configured to:
 detect the event in the wellbore based on the third set of measurement values received from the third sensor; and 
 update the probability value assigned to the event based on the event as detected in the third set of measurement values. 
 
 
     
     
         3 . The drilling system of  claim 1 , wherein the surface equipment is configured to generate smoothed measurement values by partitioning the measurement values into overlapping or non-overlapping segments and assigning a slope value to each of the segments, the slope value representing the slope of a line fit to the measurement values of a segment. 
     
     
         4 . The drilling system of  claim 3 , wherein the surface equipment is configured to:
 identify peaks, valleys, and zero-crossings in the smoothed measurement values, and   assign symbol values to the peaks, valleys, and zero-crossing including:
 assignment of a first symbol to each peak, assignment of a second symbol to each valley, and assignment of a third symbol to each zero-crossing. 
   
     
     
         5 . The drilling system of  claim 4  wherein the surface equipment is configured to detect the event by comparing a symbol set that includes multiple sequential ones of the symbol values to an event definition that identifies the event based on the symbol values. 
     
     
         6 . The drilling system of  claim 4 , wherein the surface equipment is configured to assign the probability value to the event based on a time difference between a peak of the event in the first set of measurement values and a peak of the event in the second set of measurement values. 
     
     
         7 . The drilling system of  claim 1 , wherein the surface equipment is configured to identify the event as being real based on the probability value exceeding a threshold. 
     
     
         8 . The drilling system of  claim 7 , wherein the surface equipment is configured to halt drilling based on the event being identified as real. 
     
     
         9 . The drilling system of  claim 7 , wherein the surface equipment is configured to, based on the event being identified as real:
 determine a location of a fluid influx in the wellbore; and   determine a time at which the fluid influx will reach a target location.   
     
     
         10 . A method for downhole event detection comprising:
 measuring a parameter of a wellbore using a first sensor of a drill string;   measuring the parameter of the wellbore using a second sensor of the drill string;   detecting, by surface equipment, an event in the wellbore based on a first set of measurements provided by the first sensor;   detecting, by surface equipment, the event in the wellbore based on a second set of measurements provided by the second sensor; and   assigning, by surface equipment, a probability value to the event based on the event as detected in the first set of measurement values and the event as detected in the second set of measurement values.   
     
     
         11 . The method of  claim 10 , further comprising:
 measuring the parameter of the wellbore using a third sensor of the drill string;   detecting, by surface equipment, the event in the wellbore based on a third set of measurements provided by the third sensor; and   updating, by surface equipment, the probability value assigned to the event based on the event as detected in the third set of measurement values.   
     
     
         12 . The method of  claim 10 , further comprising generating, by the surface equipment, smoothed measurement values by partitioning the measurement values into segments and assigning a slope value to each of the segments, the slope value representing the slope of a line fit to the measurement values of the segment. 
     
     
         13 . The method of  claim 12 , further comprising:
 identifying, by the surface equipment, peaks, valleys, and zero-crossings in the smoothed measurement values, and   assign, by the surface equipment, symbol values to the peaks, valleys, and zero-crossing including:
 assignment of a first symbol to each peak, assignment of a second symbol to each valley, and assignment of a third symbol to each zero-crossing. 
   
     
     
         14 . The method of  claim 13 , further comprising detecting the event by comparing a symbol set that includes multiple sequential ones of the symbol values to an event definition that identifies the event based on the symbol values. 
     
     
         15 . The method of  claim 13 , further comprising assigning the probability value to the event based on a time difference between a peak of the event in the first set of measurement values and a peak of the event in the second set of measurement values. 
     
     
         16 . The method of  claim 10 , further comprising identifying, by the surface equipment, the event as being real based on the probability value exceeding a threshold. 
     
     
         17 . The method of  claim 16 , further comprising halting drilling responsive to the event being identified as real. 
     
     
         18 . The method of  claim 16 , further comprising:
 based on the event being identified as real:
 determining a location of a fluid influx in the wellbore; and 
 determining a time at which the fluid influx will reach a target location. 
   
     
     
         19 . A non-transitory computer-readable medium encoded with instructions that when executed cause a processor to:
 receive a first set measurement values representative of a parameter of a wellbore measured by a first sensor of a drill string;   receive a second set of measurement values representative of the parameter of the wellbore measured by a second sensor of the drill string;   receive a third set of measurement values representative of the parameter of the wellbore measured by a third sensor of the drill string;   detect an event in the wellbore based on the first set of measurement values received from the first sensor;   detect the event in the wellbore based on the second set of measurement values received from the second sensor;   detect the event in the wellbore based on the third set of measurement values received from the second sensor;   assign a probability value to the event based on the event as detected in the first set of measurement values and the event as detected in the second set of measurement values; and   update the probability value assigned to the event based on the event as detected in the third set of measurement values.   
     
     
         20 . The non-transitory computer-readable medium of  claim 19 , wherein the instructions when executed cause the processor to generate smoothed measurement values by partitioning the measurement values into segments and assigning a slope value to each of the segments, the slope value representing the slope of a line fit to the measurement values of a segment. 
     
     
         21 . The non-transitory computer-readable medium of  claim 20 , wherein the instructions when executed cause the processor to:
 identify peaks, valleys, and zero-crossings in the smoothed measurement values, and   assign symbol values to the peaks, valleys, and zero-crossing including:
 assignment of a first symbol to each peak, assignment of a second symbol to each valley, and assignment of a third symbol to each zero-crossing. 
   
     
     
         22 . The non-transitory computer-readable medium of  claim 19 , wherein the instructions when executed cause the processor to:
 assign the probability value to the event based on a time difference between a peak of the event in the first set of measurement values and a peak of the event in the second set of measurement values; and   identify the event as being real based on the probability value exceeding a threshold.   
     
     
         23 . The non-transitory computer-readable medium of  claim 22 , wherein the instructions when executed cause the processor to halt drilling based on the event being identified as real. 
     
     
         24 . The non-transitory computer-readable medium of  claim 22 , wherein the instructions when executed cause the processor to, based on the event being identified as real:
 determine a location of a fluid influx in the wellbore; and   determine a time at which the fluid influx will reach a target location.