Detecting a Drill String Washout Event

Abstract

A method for detecting a drill string washout event. The method includes locating a drill string in a wellbore formed in a subterranean formation. A drilling fluid is pumped into the drill string. The drill string includes a turbine that spins in response to the drilling fluid flowing therethrough. A comparison is made between a rate that the drilling fluid is pumped into the drill string and a spin rate of the turbine. A defect is determined to be formed in the drill string based upon the comparison.

What is claimed is: 
     
         1 . A method for detecting a drill string washout event, comprising:
 locating a drill string in a wellbore formed in a subterranean formation;   pumping a drilling fluid into the drill string, wherein the drill string comprises a turbine, and wherein the turbine spins in response to the drilling fluid flowing therethrough;   comparing a rate that the drilling fluid is pumped into the drill string to a spin rate of the turbine; and   determining that a defect is formed in the drill string based upon the comparison.   
     
     
         2 . The method of  claim 1 , wherein comparing the rate that the drilling fluid is pumped into the drill string to the spin rate of the turbine comprises determining a ratio of the rate that the drilling fluid is pumped into the drill string to the spin rate of the turbine. 
     
     
         3 . The method of  claim 2 , further comprising determining that the defect is formed in the drill string when the ratio is below a predetermined threshold. 
     
     
         4 . The method of  claim 3 , further comprising triggering an alarm when the ratio is below the predetermined threshold for a predetermined amount of time. 
     
     
         5 . The method of  claim 1 , wherein the defect comprises a crack or opening formed in the drill string that allows the drilling fluid to flow therethrough and into an annulus formed between the drill string and a wall of the wellbore. 
     
     
         6 . The method of  claim 5 , further comprising determining a flow rate through the defect. 
     
     
         7 . The method of  claim 5 , further comprising determining a location of the defect in the drill string. 
     
     
         8 . A method for monitoring fluid flow in a wellbore, comprising:
 locating a drill string in a wellbore formed in a subterranean formation, wherein an annulus is formed between the drill string and a wall of the wellbore;   pumping a drilling fluid into the drill string from a surface location, wherein the drilling fluid flows through a drill bit positioned at an end portion of the drill string and back to the surface location via the annulus;   measuring a flow rate into the drill string with a first flow rate sensor disposed at the surface location;   measuring a downhole flow rate with a second flow rate sensor disposed within the wellbore;   measuring a flow rate out of the annulus with a third flow rate sensor disposed at the surface location; and   establishing a multi-dimensional relationship based upon the flow rate into the drill string, the downhole flow rate, and the flow rate out of the annulus.   
     
     
         9 . The method of  claim 8 , wherein the multi-dimensional relationship is determined using a parametric theoretical model, a statistical analysis technique, a principal component analysis, a factor analysis, neural network empirical correlations, or combinations thereof. 
     
     
         10 . The method of  claim 8 , further comprising determining that a defect is formed in the drill string if the downhole flow rate is less than the flow rate into the drill string by a predetermined amount, if the downhole flow rate is less than the flow rate out of the annulus by the predetermined amount, or both, wherein the defect comprises a crack or opening formed in the drill string that allows the drilling fluid to flow therethrough and into the annulus. 
     
     
         11 . The method of  claim 10 , further comprising determining a location of the defect in the drill string using:
 at least one of the flow rate into the drill string, the downhole flow rate, and the flow rate out of the annulus;   a pressure differential between two sensors, wherein the two sensors are selected from the group consisting of a sensor disposed at the surface location and adapted to measure a pressure of the drilling fluid being pumped into the drill string, a sensor disposed within the drill string and adapted to measure a pressure of the drilling fluid within the drill string, a sensor disposed within the annulus and adapted to measure a pressure of the drilling fluid within the annulus, and a sensor disposed at the surface location and adapted to measure a pressure of the drilling fluid flowing out of the annulus; and   a depth of the drill bit.   
     
     
         12 . The method of  claim 8 , further comprising determining that a portion of the drilling fluid is flowing into the subterranean formation if the flow rate out of the annulus is less than the flow rate into the drill string by a predetermined amount, if the flow rate out of the annulus is less than the downhole flow rate by the predetermined amount, or both. 
     
     
         13 . The method of  claim 12 , further comprising determining a location where the drilling fluid flows into the formation using:
 at least one of the flow rate into the drill string, the downhole flow rate, and the flow rate out of the annulus;   a pressure differential between two sensors, wherein the two sensors are selected from the group consisting of a sensor disposed at the surface location and adapted to measure a pressure of the drilling fluid being pumped into the drill string, a sensor disposed within the drill string and adapted to measure a pressure of the drilling fluid within the drill string, a sensor disposed within the annulus and adapted to measure a pressure of the drilling fluid within the annulus, and a sensor disposed at the surface location and adapted to measure a pressure of the drilling fluid flowing out of the annulus; and   a depth of the drill bit.   
     
     
         14 . The method of  claim 8 , further comprising determining that formation fluid is flowing into the annulus from the subterranean formation if the flow rate out of the annulus is greater than the flow rate into the drill string by a predetermined amount, if the flow rate out of the annulus is greater than the downhole flow rate by the predetermined amount, or both. 
     
     
         15 . The method of  claim 14 , further comprising determining a location where the formation fluid flows from the formation using:
 at least one of the flow rate into the drill string, the downhole flow rate, and the flow rate out of the annulus;   a pressure differential between two sensors, wherein the two sensors are selected from the group consisting of a sensor disposed at the surface location and adapted to measure a pressure of the drilling fluid being pumped into the drill string, a sensor disposed within the drill string and adapted to measure a pressure of the drilling fluid within the drill string, a sensor disposed within the annulus and adapted to measure a pressure of the drilling fluid within the annulus, and a sensor disposed at the surface location and adapted to measure a pressure of the drilling fluid flowing out of the annulus; and   a depth of the drill bit.   
     
     
         16 . The method of  claim 8 , wherein at least one of the flow rate into the drill string, the downhole flow rate, and the flow rate out of the annulus is determined using a plurality of distributed pressure sensors coupled to the drill string. 
     
     
         17 . The method of  claim 8 , wherein the downhole flow rate comprises a flow rate within the drill string, a flow rate in the annulus, or both. 
     
     
         18 . A computer program embodied on a non-transitory computer readable medium that, when executed by a processor, controls a method for detecting a drill string washout event, comprising:
 establishing a multi-dimensional relationship based upon a flow rate into a drill string, a downhole flow rate, and a flow rate out of an annulus, wherein the drill string is disposed in the wellbore, and the annulus is formed between the drill string and a wall of the wellbore; and   determining that a defect is formed in the drill string using:
 at least one of the flow rate into the drill string, the downhole flow rate, and the flow rate out of the annulus; 
 a pressure differential between two sensors, wherein the two sensors are selected from the group consisting of a sensor disposed at the surface location and adapted to measure a pressure of the drilling fluid being pumped into the drill string, a sensor disposed within the drill string and adapted to measure a pressure of the drilling fluid within the drill string, a sensor disposed within the annulus and adapted to measure a pressure of the drilling fluid within the annulus, and a sensor disposed at the surface location and adapted to measure a pressure of the drilling fluid flowing out of the annulus; and 
 a depth of a drill bit coupled to an end portion of the drill string. 
   
     
     
         19 . The method of  claim 18 , wherein the multi-dimensional relationship is determined using a parametric theoretical model, a statistical analysis technique, a principal component analysis, a factor analysis, neural network empirical correlations, or combinations thereof. 
     
     
         20 . The method of  claim 18 , wherein at least one of the flow rate into the drill string, the downhole flow rate, and the flow rate out of the annulus is determined using a plurality of distributed pressure sensors coupled to the drills string.