Apparatus and method for real time and real flow-rate measurement of multi-phase fluids

Abstract

A method for measuring flow rate of at least one fluid in a multi-phase fluid comprises: providing a magnetic resonance module through which the fluid phases flow and at least one pre-polarization module of variable effective length upstream of the magnetic resonance module; and conducting, a measurement by: i) setting the pre-polarization module to have a first effective length, ii) applying a RF pulse sequence to the fluid, in the magnetic resonance module, iii) determining the intensity of a pre-determined number of spin echoes produced by the RF pulse sequence, iv) determining a line approximating the attenuation of the intensity during the RF sequence, v) determining slope and y-intercept of the line, vi) determining the ratio of the slope and intercept, vii) applying a calibration between the slope:intercept ratio and multi-phase flow rate so as to determine the flow velocity of the fluid in the multi-phase fluid.

1 . A method for measuring the flow velocity of at least one fluid of interest in a multi-phase fluid flowing in a pipe at a known overall flow rate, said fluid comprising first, second, and third fluid phases, the method comprising the steps of:
 a) providing an MRI-compatible device comprising:
 a magnetic resonance module through which the fluid phases flow; and 
 at least one pre-polarization module producing a pre-polarization magnetic field of variable effective length through which the multi-phase fluid flows before entering the magnetic resonance module; 
 wherein a previously determined velocity calibration of the magnetic resonance module, between slope : intercept ratios and flow velocities for each of a plurality of fluids flowing through the device, is known and wherein each calibration is obtained by determining the slope : intercept ratio at each of a plurality of flow velocities; 
   conducting a measurement comprising the steps of:
 i) setting the pre-polarization module so as to pre-polarize resonant nuclei of said multi-phase fluid for a time period that is adequate with respect to the spin-lattice relaxation time T i  of a first selected fluid phase; 
 ii) applying in the magnetic resonance module a CPMG pulse sequence corresponding to said first selected fluid phase so as to excite said resonant nuclei and thereby generate a magnetic resonance signal; 
 iii) determining the intensity of a pre-determined number of spin echoes that are produced by the CPMG pulse sequence; 
 iv) determining a line that approximates the attenuation of the intensity of the pre-determined number of spin echoes with increasing time during which the RF sequence is applied; 
 v) determining slope and y-intercept of the line determined in step iv); 
 vi) determining the ratio of the slope and the intercept determined in step v); 
 vii) using the previously determined velocity calibration in order to determine the flow velocity of the fluid of interest in the multi-phase fluid; and 
 viii) providing the flow velocity determined in step b)vii) to a user; and 
   
     
     
         2 . The method according to  claim 2 , further including using the determined flow velocity to determine the fluid fraction of the first fluid in the multi-phase fluid by using a predetermined intensity calibration, for a module through which only the first fluid is flowing, between signal intensity and fluid velocity at each of a plurality of velocities and comparing the detected intensity to the single-fluid intensity at the determined, flow velocity. 
     
     
         3 . The method according to  claim 2 , further including repeating step b) using a second setting of the pre-polarization module so as to determine the flow velocity of a second fluid of interest in the multi-phase fluid and using, the determined flow velocity of the second fluid to determine the fluid fraction of the second fluid in the multi-phase fluid by using a predetermined calibration, for a module through which only the second fluid is flowing, between signal intensity and fluid velocity at each of a plurality of velocities and comparing the detected intensity to the single-fluid intensity at the determined flow velocity for the second fluid. 
     
     
         4 . The method according to  claim 3  wherein said first and second fluids are oil and water. 
     
     
         5 . The method according to  claim 3  wherein the multi-phase fluid comprises water, oil, and gas.