Accurate water cut measurement
A method of incorporating the influence of diffusion into the CPMG-based T2 measurement for one or more of the following: water cut measurement; performing inline measurements of flow rate; density; and rheology of a flowing fluid. The method includes conducting a “standard T1/T2 experiment” at least twice by providing one scan without a field gradient during the CMPG echo train. Then, providing a second scan with the application of a gradient, where in the second experiment the measured T2 (T2 app ) is affected solely by water diffusion, thus shifting cross peaks which represent water on the first T1/T2 spectrum to lower T2 values on the second spectrum.
1. A method for determining a distribution between oil and water in a fluid, the method comprising:
performing, via an NMR spectrometer, a first measurement of the fluid, wherein the first measurement is taken without a field gradient during a CPMG pulse sequence of the first measurement;
performing, via the NMR spectrometer, a second measurement of the fluid, wherein the second measurement is taken with a field gradient applied during a CPMG pulse sequence of the second measurement; and
comparing the first measurement to the second measurement to determine the distribution between oil and water in the fluid,
wherein:
the first measurement is a first T1/T2 spectrum and the second measurement is a second T1/T2 spectrum,
each of the T1/T2 spectra include a cross peak representing water and a cross peak representing oil,
the cross peak representing oil in the first T1/T2 spectrum is substantially the same as the cross peak representing oil in the second T1/T2 spectrum, and
the cross peak representing water in the second T1/T2 spectrum corresponds to a lower T2 value as compared to the cross peak representing water in the first T1/T2 spectrum.
2. The method of claim 1 wherein the fluid is drilling mud.
3. The method of claim 1 wherein the NMR spectrometer generates a first and a second radial pressure profile based on the first measurement and the second measurement, respectively.
4. The method of claim 1 wherein the first measurement, the second measurement or both are in-line measurements of drilling mud.
5. The method of claim 1 , wherein the field gradient is applied during at least a CPMG pulse sequence of the second measurement.