Method and system for detecting at least one of an influx event and a loss event during well drilling

Abstract

Methods, systems, and techniques for detecting at least one of an influx event and a loss event during well drilling involve using one or both of errors between 1) estimated and measured pit volume, and 2) estimated and measured flow out, to identify or determine whether the influx or loss event is occurring, or to sound some other type of related alert. These determinations may be performed in a computationally efficient manner, such as by using one or both of a time and depth sensitive regression.

1 . A method for detecting at least one of an influx event and a loss event during well drilling, the method comprising:
 (a) determining, using a processor, an estimated pit volume, wherein the processor determines the estimated pit volume as one of a value less than or equal to a trailing median of a measured pit volume and a value greater than or equal to the trailing median of the measured pit volume;   (b) determining, using the processor, a pit volume difference between the estimated pit volume and a measured pit volume, and:
 (i) when the processor determines the estimated pit volume as the value less than or equal to the trailing median, whether the magnitude of the pit volume difference exceeds an influx event threshold and the measured pit volume exceeds the estimated pit volume; and 
 (ii) when the processor determines the estimated pit volume as the value greater than or equal to the trailing median, whether the magnitude of the pit volume difference exceeds a loss event threshold and the estimated pit volume exceeds the measured pit volume; 
   (c) when the processor determines that the magnitude of the pit volume difference exceeds the influx event threshold and the measured pit volume exceeds the estimated pit volume, identifying the influx event as occurring; and   (d) when the processor determines that the magnitude of the pit volume difference exceeds the loss event threshold and the estimated pit volume exceeds the measured pit volume, identifying the loss event as occurring.   
     
     
         2 . The method of  claim 1  wherein the estimated pit volume is determined as the value less than or equal to the trailing median of the pit volume. 
     
     
         3 . The method of  claim 1  wherein the estimated pit volume is determined as the value greater than or equal to the trailing median of the pit volume. 
     
     
         4 . The method of  claim 1  further comprising:
 (a) determining, using the processor, an additional estimated pit volume as the other of the trailing minimum and the trailing maximum of the measured pit volume; 
 (b) determining, using the processor, an additional pit volume difference between the additional pit volume and the measured pit volume, and:
 (i) when the processor determines the additional estimated pit volume as the trailing minimum, whether the magnitude of the additional pit volume difference exceeds the influx event threshold and the measured pit volume exceeds the additional estimated pit volume; and 
 (ii) when the processor determines the additional estimated pit volume as the trailing maximum, whether the magnitude of the additional pit volume difference exceeds the loss event threshold and the additional estimated pit volume exceeds the measured pit volume; 
 
 (c) when the processor determines that the magnitude of the additional pit volume difference exceeds the influx event threshold and the measured pit volume exceeds the additional estimated pit volume, identifying the influx event as occurring; and 
 (d) when the processor determines that the magnitude of the additional pit volume difference exceeds the loss event threshold and the additional estimated pit volume exceeds the measured pit volume, identifying the loss event as occurring. 
 
     
     
         5 . A method for detecting at least one of an influx event and a loss event during well drilling, the method comprising:
 (a) determining, using a processor, an estimated flow out, wherein the estimated flow out comprises a sum of scaled and historical measured flow in readings, wherein weights used to scale the measured flow in readings are determined using the measured flow in readings measured during or around one or both of pump on and off transient events;   (b) determining, using the processor, a flow out difference between the estimated flow out and measured flow out, and at least one of:
 (i) whether the magnitude of the flow out difference exceeds an influx event threshold and the measured flow out exceeds the estimated flow out; and 
 (ii) whether the magnitude of the flow out difference exceeds a loss event threshold and the estimated flow out exceeds the measured flow out; 
   (c) when the processor determines that the flow out difference exceeds the influx event threshold and the measured flow out exceeds the estimated flow out, identifying the influx event as occurring; and   (d) when the processor determines that the flow out difference exceeds the loss event threshold and the estimated flow out exceeds the measured flow out, identifying the loss event as occurring.   
     
     
         6 . The method of  claim 5  wherein the processor determines whether the magnitude of the flow out difference exceeds the influx event threshold and the measured flow out exceeds the estimated flow out, and whether the magnitude of the flow out difference exceeds the loss event threshold and the estimated flow out exceeds the measured flow out. 
     
     
         7 . The method of  claim 5  wherein the weights are determined using a time sensitive regression. 
     
     
         8 . The method of  claim 5  wherein the estimated flow out further comprises a sum of scaled and historical readings of changes with respect to time of a difference between hole depth and bit depth. 
     
     
         9 . The method of  claim 8  wherein weights used to scale the readings of changes with respect to time of the difference between hole depth and bit depth are determined during or around events during which bit depth changes while hole depth stays constant. 
     
     
         10 . The method of  claim 9  wherein the weights used to scale the readings of changes with respect to time of the difference between hole depth and bit depth are determined within five minutes of events during which bit depth changes while hole depth stays constant. 
     
     
         11 . The method of  claim 9  wherein the weights used to scale the readings of changes with respect to time of the difference between hole depth and bit depth are determined using a time sensitive regression. 
     
     
         12 . A method for detecting at least one of an influx event and a loss event during well drilling, the method comprising:
 (a) determining, using a processor, an estimated pit volume, wherein the processor determines the estimated pit volume by using historical flow in measurements;   (b) determining, using the processor, a pit volume difference between estimated pit volume and measured pit volume, and at least one of:
 (i) whether the magnitude of the pit volume difference exceeds an influx event threshold and the measured pit volume exceeds the estimated pit volume; and 
 (ii) whether the magnitude of the pit volume difference exceeds a loss event threshold and the estimated pit volume exceeds the measured pit volume; 
   (c) when the processor determines that the magnitude of the pit volume difference exceeds the influx event threshold and the measured pit volume exceeds the estimated pit volume, identifying the influx event as occurring; and   (d) when the processor determines that the magnitude of the pit volume difference exceeds the loss event threshold and the estimated pit volume exceeds the measured pit volume, identifying the loss event as occurring.   
     
     
         13 . The method of  claim 12  wherein the estimated pit volume comprises a difference between a sum of historical flow out measurements and a sum of historical flow in measurements. 
     
     
         14 . The method of  claim 13  wherein the flow in measurements that are summed are compensated for the time for drilling fluid to travel from a mud tank to an input flow meter. 
     
     
         15 . The method of  claim 13  wherein the flow out measurements that are summed are compensated for the time for drilling fluid to travel from a return flow meter to a mud tank. 
     
     
         16 . The method of  claim 13  wherein the historical flow in and flow out measurements correspond to flow in and flow out during or around one or both of pump on and off transient events. 
     
     
         17 . The method of  claim 12  wherein the processor determines the estimated pit volume by:
 (a) determining a sum of scaled and historical measured readings of changes with respect to time of flow in, wherein weights used to scale the readings of changes with respect to time of flow in are determined from measured flow in readings measured during or around one or both of pump on and off transient events; and 
 (b) summing the sum of scaled and historical measured readings of changes with respect to time of flow in to determine the estimated pit volume. 
 
     
     
         18 . A method for detecting at least one of an influx event and a loss event during well drilling, the method comprising:
 (a) determining, using a processor, an estimated pit volume, wherein the processor determines the estimated pit volume by applying at least one of a time and depth sensitive regression;   (b) determining, using the processor, a pit volume difference between the estimated pit volume and a measured pit volume, and at least one of:
 (i) whether the magnitude of the pit volume difference exceeds an influx event threshold and the measured pit volume exceeds the estimated pit volume; and 
 (ii) whether the magnitude of the pit volume difference exceeds a loss event threshold and the estimated pit volume exceeds the measured pit volume; 
   (c) when the processor determines that the magnitude of the pit volume difference exceeds the influx event threshold and the measured pit volume exceeds the estimated pit volume, identifying the influx event as occurring; and   (d) when the processor determines that the magnitude of the pit volume difference exceeds the loss event threshold and the estimated pit volume exceeds the measured pit volume, identifying the loss event as occurring.   
     
     
         19 . The method of  claim 18  wherein the processor determines the estimated pit volume using the time sensitive regression and not the depth sensitive regression. 
     
     
         20 . The method of  claim 18  wherein the processor determines the estimated pit volume using the depth sensitive regression and not the time sensitive regression. 
     
     
         21 . The method of  claim 18  wherein the processor determines the estimated pit volume using the depth sensitive regression and the time sensitive regression. 
     
     
         22 . The method of  claim 18  wherein the processor determines whether the magnitude of the pit volume difference exceeds the influx event threshold and the measured pit volume exceeds the estimated pit volume, and whether the magnitude of the pit volume difference exceeds the loss event threshold and the estimated pit volume exceeds the measured pit volume. 
     
     
         23 . The method of  claim 21  wherein:
 (a) the estimated pit volume is determined as a sum of the depth sensitive regression and the time sensitive regression; 
 (b) each of the depth and time sensitive regressions is a linear regression; 
 (c) the depth sensitive regression is determined from historical measurements of hole depth and the pit volume; and 
 (d) the time sensitive regression is determined from historical values of the depth sensitive regression.