Correction of coriolis flowmeter measurements due to multiphase flows

Abstract

A Coriolis flowmeter is operable as a vibrating tube densitometer where a flowtube is driven to vibrate at a fundamental frequency from which density of the material flowing through the flowtube may be calculated. The drive gain is monitored as an indicator of multiphase flow including gas and liquid components where a substantial increase in drive gain indicates gas damping of the flowtube vibrations due to a transient bubble entering the flowtube. The gas damping effects of the transient bubble and the correspondingly reduced density readings are remediated by the use of historical density measurements corresponding to periods of flow when no transient bubble has entered the flowtube.

1. A Coriolis flowmeter which measures densities of materials including combinations of gas and liquids, gas and solids, or solids and liquids, said flowmeter comprising:
 at least one flowtube;  
 a driver that vibrates said at least one flowtube at a fundamental frequency based on a drive signal, said fundamental frequency corresponding to a density of material flowing through said at least one flowtube;  
 pickoffs affixed to said at least one flowtube that generate pickoff signals responsive to said material flowing through said at least one flowtube; and  
 meter electronics configured to: 
 determine said density of said material flowing through said at least one flowtube based on at least one of said pickoff signals,  
 monitor a drive gain in said at least one flow tube for a change in value to determine if said material flowing through said at least one flowtube comprises a multiphase flow, and  
 if said material flowing through said at least one flowtube comprises a multiphase flow, then determine said density of said material flowing through said at least one flowtube based on a stored density value.  
 
 
     
     
       2. The flowmeter as set forth in  claim 1  wherein said meter electronics is further configured to determine whether said drive gain exceeds a first threshold value to determine if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       3. The flowmeter as set forth in  claim 2  wherein said first threshold value represents said multiphase flow includes gas and liquids. 
     
     
       4. The flowmeter as set forth in  claim 3  wherein said meter electronics is further configured to determine whether said drive gain exceeds a second threshold value, said second threshold value represents that said multiphase flow includes liquid and solid matter. 
     
     
       5. The flowmeter as set forth in  claim 1  wherein said meter electronics is further configured to average historical density measurements over an interval of time to determine said density if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       6. The flowmeter as set forth in  claim 5  wherein said meter electronics is further configured to apply a statistical analysis to said historical density measurements to eliminate or reduce spurious measurements. 
     
     
       7. The flowmeter as set forth in  claim 1  wherein said meter electronics is further configured to process density measurements obtained from laboratory measurements to determine said density if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       8. The flowmeter as set forth in  claim 1  wherein said meter electronics is further configured to process correlations to determine said density if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       9. The flowmeter as set forth in  claim 1  further comprising:
 circuitry configured to close a valve to stop a well test in progress on a fluid flowing from a production well.  
 
     
     
       10. The flowmeter as set forth in  claim 1  further comprising:
 means for indicating an alarm indicative of said multiphase flow.  
 
     
     
       11. A method of operating a Coriolis flowmeter to measure densities of materials, said method comprising the steps of:
 vibrating at least one flowtube of said Coriolis flowmeter at a fundamental frequency corresponding to a density of material flowing through said at least one flowtube;  
 generating pickoff signals that represent motion of said at least one flow tube as said material flows through said at least one flowtube;  
 determining said density of said material flowing through said at least one flowtube based on at least one of said pickoff signals;  
 monitoring a drive gain in said at least one flowtube for a change in value to determine if said material flowing through said at least one flowtube comprises a multiphase flow; and  
 if said material flowing through said at least one flowtube comprises said multiphase flow, then determining said density of said material flowing through said at least one flowtube based on a stored density value.  
 
     
     
       12. The method as set forth in  claim 11  wherein said step of monitoring said drive gain includes comparing said drive gain to a first threshold value to determine if said drive gain exceeds said first threshold value to determine if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       13. The method as set forth in  claim 12  wherein said step of comparing includes setting said first threshold value to represent that said multiphase flow includes gas and liquids. 
     
     
       14. The method as set forth in  claim 11  wherein said step of comparing includes setting a second threshold value to represent that said multiphase flow includes liquids and solid matter and comparing said drive gain to said second threshold value to determine whether said drive gain exceeds said second threshold value. 
     
     
       15. The method as set forth in  claim 11  wherein said step of determining said density of said material flowing through said at least one flowtube based on said stored density value further includes a step of averaging historical density measurements over an interval of time to determine said density. 
     
     
       16. The method as set forth in  claim 15  wherein said step of averaging said historical density measurements further includes a step of applying a statistical analysis to said historical density measurements to eliminate or reduce spurious measurements. 
     
     
       17. The method as set forth in  claim 11  wherein said step of determining said density of said material flowing through said at least one flowtube based on said stored density value further includes processing density measurements obtained from laboratory measurements to determine said density. 
     
     
       18. The method as set forth in  claim 11  wherein said step of determining said density of said material flowing through said at least one flowtube based on said stored density value further includes processing correlations to determine said density. 
     
     
       19. A Coriolis flowmeter which measures mass flow rates of materials including combinations of gas and liquids, gas and solids, or solids and liquids, said flowmeter comprising:
   at least one flowtube;        a driver that vibrates said at least one flowtube at a fundamental frequency based on a drive signal;        pickoffs affixed to said at least one flowtube that generate pickoff signals responsive to said material flowing through said at least one flowtube; and        meter electronics configured to:      determine said mass flow rate of said material flowing through said at least one flowtube based on said pickoff signals,        monitor a drive gain in said at least one flow tube for a change in value to determine if said material flowing through said at least one flowtube comprises a multiphase flow, and        if said material flowing through said at least one flowtube comprises a multiphase flow, then determine said mass flow rate of said material flowing through said at least one flowtube based on a stored mass flow rate value.       
     
     
       20. The flowmeter as set forth in  claim 19  wherein said meter electronics is further configured to determine whether said drive gain exceeds a first threshold value to determine if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       21. The flowmeter as set forth in  claim 20  wherein said first threshold value represents that said multiphase flow includes gas and liquids. 
     
     
       22. The flowmeter as set forth in  claim 21  wherein said meter electronics is further configured to determine whether said drive gain exceeds a second threshold value, said second threshold value represents that said multiphase flow includes liquid and solid matter. 
     
     
       23. The flowmeter as set forth in  claim 19  wherein said meter electronics is further configured to average historical mass flow rate measurements over an interval of time to determine said mass flow rate if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       24. The flowmeter as set forth in  claim 23  wherein said meter electronics is further configured to apply a statistical analysis to said historical mass flow rate measurements to eliminate or reduce spurious measurements. 
     
     
       25. The flowmeter as set forth in  claim 19  wherein said meter electronics is further configured to process correlations to determine said mass flow rate if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       26. The flowmeter as set forth in  claim 19  further comprising:
   circuitry configured to close a valve to stop a well test in progress on a fluid flowing from a production well.     
     
     
       27. The flowmeter as set forth in  claim 19  further comprising:
   means for indicating an alarm indicative of said multiphase flow.     
     
     
       28. A method of operating a Coriolis flowmeter to measure mass flow rates of materials, said method comprising the steps of:
   vibrating at least one flowtube of said Coriolis flowmeter at a fundamental frequency corresponding to a mass flow rate of material flowing through said at least one flowtube;        generating pickoff signals that represent motion of said at least one flow tube as said material flows through said at least one flowtube;        determining said mass flow rate of said material flowing through said at least one flowtube based on said pickoff signals;        monitoring a drive gain in said at least one flowtube for a change in value to determine if said material flowing through said at least one flowtube comprises a multiphase flow; and        if said material flowing through said at least one flowtube comprises said multiphase flow, then determining said mass flow rate of said material flowing through said at least one flowtube based on a stored mass flow rate value.     
     
     
       29. The method as set forth in  claim 28  wherein said step of monitoring said drive gain includes comparing said drive gain to a first threshold value to determine if said drive gain exceeds said first threshold value to determine if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       30. The method as set forth in  claim 29  wherein said step of comparing includes setting said first threshold value to represent that said multiphase flow includes gas and liquids. 
     
     
       31. The method as set forth in  claim 28  wherein said step of comparing includes setting a second threshold value to represent that said multiphase flow includes liquids and solid matter and comparing said drive gain to said second threshold value to determine whether said drive gain exceeds said second threshold value. 
     
     
       32. The method as set forth in  claim 28  wherein said step of determining said mass flow rate of said material flowing through said at least one flowtube based on said stored mass flow rate value further includes a step of averaging historical mass flow rate measurements over an interval of time to determine said mass flow rate. 
     
     
       33. The method as set forth in  claim 32  wherein said step of averaging said historical mass flow rate measurements further includes a step of applying a statistical analysis to said historical mass flow rate measurements to eliminate or reduce spurious measurements. 
     
     
       34. The method as set forth in  claim 28  wherein said step of determining said mass flow rate of said material flowing through said at least one flowtube based on said stored mass flow rate value further includes processing correlations to determine said mass flow rate. 
     
     
       35. A flowmeter, comprising:
   at least one flowtube;        a driver that vibrates said at least one flowtube based on a drive signal;        pickoffs affixed to said at least one flowtube that generate pickoff signals comprising a vibrational response to said material flowing through said at least one flowtube; and        meter electronics configured to:      monitor said vibrational response for a change in value to determine if said material flowing through said at least one flowtube comprises a multiphase flow; and        substitute remediation data in place of a flowmeter measurement if said material flowing through said at least one flowtube comprises said multiphase flow.       
     
     
       36. The flowmeter of  claim 35 , with said flowmeter comprising a Coriolis flowmeter. 
     
     
       37. The flowmeter of  claim 35 , with said flowmeter comprising a vibrating densitometer. 
     
     
       38. The flowmeter of  claim 35 , with said vibrational response comprising a pickoff frequency to drive frequency ratio. 
     
     
       39. The flowmeter of  claim 35 , with said vibrational response comprising a drive gain. 
     
     
       40. The flowmeter of  claim 35 , with said monitoring further comprising:
   comparing said vibrational response to a first threshold value; and        determining that said material flowing through said at least one flowtube comprises said multiphase flow if said vibrational response exceeds said first threshold value.     
     
     
       41. The flowmeter of  claim 35 , with said monitoring further comprising:
   comparing said vibrational response to a second threshold value; and        determining that said multiphase flow includes liquids and solid matter if said vibrational response exceeds said second threshold value.     
     
     
       42. The flowmeter of  claim 35 , with said remediation data comprising historical data. 
     
     
       43. The flowmeter of  claim 35 , with said remediation data comprising averaged historical data. 
     
     
       44. The flowmeter of  claim 35 , with said remediation data comprising historical data wherein spurious measurement values have been substantially eliminated. 
     
     
       45. The flowmeter of  claim 35 , with said remediation data comprising empirical measurement data. 
     
     
       46. The flowmeter of  claim 35 , with said remediation data comprising measurement data received from an outside density meter. 
     
     
       47. The flowmeter of  claim 35 , with said remediation data comprising previous measurement data. 
     
     
       48. The flowmeter of  claim 35 , with said remediation data comprising previous measurement data and with the method further comprising:
   comparing said vibrational response to a multiphase threshold value;        determining that said material flowing through said at least one flowtube comprises said multiphase flow if said vibrational response exceeds said multiphase threshold value;        testing measurements of a previous measurement interval for flowmeter measurements above said multiphase threshold value; and        using said measurements of said previous measurement interval as said remediation data if said measurements of said previous measurement interval do not exceed said multiphase threshold value.     
     
     
       49. The flowmeter of  claim 35 , further comprising generating an alarm if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       50. The flowmeter of  claim 35 , further comprising increasing a back pressure in a connected flow conduit if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       51. The flowmeter of  claim 35 , further comprising stopping said material from flow if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       52. The flowmeter of  claim 35 , further comprising generating flow measurements for one or more selected flow components of the multiphase flow if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       53. A method of operating a flowmeter, comprising:
   vibrating at least one flowtube of said flowmeter based on a drive signal;        monitoring a vibrational response in said at least one flowtube for a change in value to determine if said material flowing through said at least one flowtube comprises a multiphase flow; and        substituting remediation data in place of a flowmeter measurement if said material flowing through said at least one flowtube comprises said multiphase flow.     
     
     
       54. The method of  claim 53 , with said flowmeter comprising a Coriolis flowmeter. 
     
     
       55. The method of  claim 53 , with said flowmeter comprising a vibrating densitometer. 
     
     
       56. The method of  claim 53 , with said vibrational response comprising a pickoff frequency to drive frequency ratio. 
     
     
       57. The method of  claim 53 , with said vibrational response comprising a drive gain. 
     
     
       58. The method of  claim 53 , with said monitoring further comprising:
   comparing said vibrational response to a first threshold value; and        determining that said material flowing through said at least one flowtube comprises said multiphase flow if said vibrational response exceeds said first threshold value.     
     
     
       59. The method of  claim 53 , with said monitoring further comprising:
   comparing said vibrational response to a second threshold value; and        determining that said multiphase flow includes liquids and solid matter if said vibrational response exceeds said second threshold value.     
     
     
       60. The method of  claim 53 , with said remediation data comprising historical data. 
     
     
       61. The method of  claim 53 , with said remediation data comprising averaged historical data. 
     
     
       62. The method of  claim 53 , with said remediation data comprising historical data wherein spurious measurement values have been substantially eliminated. 
     
     
       63. The method of  claim 53 , with said remediation data comprising empirical measurement data. 
     
     
       64. The method of  claim 53 , with said remediation data comprising measurement data received from an outside density meter. 
     
     
       65. The method of  claim 53 , with said remediation data comprising previous measurement data. 
     
     
       66. The method of  claim 53 , with said remediation data comprising previous measurement data and with the method further comprising:
   comparing said vibrational response to a multiphase threshold value;        determining that said material flowing through said at least one flowtube comprises said multiphase flow if said vibrational response exceeds said multiphase threshold value;        testing measurements of a previous measurement interval for flowmeter measurements above said multiphase threshold value; and        using said measurements of said previous measurement interval as said remediation data if said measurements of said previous measurement interval do not exceed said multiphase threshold value.     
     
     
       67. The method of  claim 53 , further comprising generating an alarm if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       68. The method of  claim 53 , further comprising increasing a back pressure in a connected flow conduit if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       69. The method of  claim 53 , further comprising stopping said material from flow if said material flowing through said at least one flowtube comprises said multiphase flow. 
     
     
       70. The method of  claim 53 , further comprising generating flow measurements for one or more selected flow components of the multiphase flow if said material flowing through said at least one flowtube comprises said multiphase flow.