Method and apparatus for determining speed and properties of flowing fluids using NMR measurements
A method for determining a property of a flowing fluid by nuclear magnetic resonance includes applying a static magnetic field to the flowing fluid; acquiring a suite of nuclear magnetic resonance measurements on the flowing fluid using a pulse sequence comprising a spoiling pulse, a wait time, and an acquisition pulse sequence, wherein the suite of nuclear magnetic measurements have different values for the wait time; and fitting the suite of nuclear magnetic resonance measurements to a forward model for responses of the flowing fluid to derive a parameter selected from a flow speed, longitudinal relaxation times of the flowing fluid, and a combination thereof.
1. A method for determining a property of a flowing fluid by nuclear magnetic resonance, comprising:
applying a static magnetic field to the flowing fluid;
acquiring a suite of nuclear magnetic resonance measurements on the flowing fluid using a pulse sequence comprising a spoiling pulse, a wait time, and an acquisition pulse sequence, wherein the suite of nuclear magnetic measurements have different values for the wait time; and
fitting the suite of nuclear magnetic resonance measurements to a forward model for responses of the flowing fluid to derive a parameter selected from a flow speed, longitudinal relaxation times of the flowing fluid, and a combination thereof.
2. The method of claim 1 , wherein the acquisition pulse sequence comprises one selected from a spin-echo pulse sequence and a single pulse.
3. The method of claim 1 , wherein the fitting is performed by inversion of the forward model.
4. The method of claim 1 , further comprising estimating a viscosity of the flowing fluid based on the derived flow speed and a pressure drop across a selected length of a pipe in which the flowing fluid travels.
5. The method of claim 4 , wherein the estimating is according to one selected from
η
=
Δ
P
·
r
o
2
8
·
v
·
L
and
η
=
K
·
Δ
P
v
,
where η is the viscosity, ν is an average speed of the flowing fluid, L is the selected length of the pipe, ΔP is the pressure drop over the selected length of the pipe, and r o is a radius of the pipe, and K is an experimentally determined constant.
6. The method of claim 1 , further comprising estimating a viscosity of the flowing fluid based on the derived longitudinal relaxation times and a gas-oil ratio of the flowing fluid.
7. The method of claim 6 , wherein the estimating is according to:
η
o
=
kT
T
1
,
LM
·
f
(
GOR
)
where η o is the viscosity, k is an empirically determined constant for the flowing fluid, T is a temperature in Kelvin, T 1,LM is a logarithmic mean of the longitudinal relaxation times of the flowing fluid, and ƒ(GOR) is an empirically determined function of the gas-oil ratio.
8. A method for determining a property of a flowing fluid by nuclear magnetic resonance, comprising:
applying a static magnetic field to the flowing fluid;
acquiring a suite of nuclear magnetic resonance measurements on the flowing fluid using a pulse sequence comprising a longitudinal relaxation investigation pulse sequence and an acquisition pulse sequence, wherein the suite of nuclear magnetic measurements have different values for a delay time within the longitudinal relaxation investigation pulse; and
fitting the suite of nuclear magnetic resonance measurements to a forward model for responses of the flowing fluid to derive a parameter selected from a flow speed, longitudinal relaxation times of the flowing fluid, and a combination thereof.
9. The method of claim 8 , wherein the longitudinal-relaxation-investigation pulse comprises one selected from a inversion-recovery pulse sequence and a saturation-recovery pulse sequence.
10. The method of claim 8 , wherein the acquisition pulse sequence comprises one selected from a spin-echo pulse sequence and a single pulse.
11. The method of claim 8 , wherein the fitting is performed by inversion of the forward model.
12. The method of claim 8 , further comprising estimating a viscosity of the flowing fluid based on the derived flow speed and a pressure drop across a selected length of a pipe in which the flowing fluid travels.
13. The method of claim 12 , wherein the estimating is according to one selected from
η
=
Δ
P
·
r
o
2
8
·
v
·
L
and
η
=
K
·
Δ
P
v
,
where η is the viscosity, ν is an average speed of the flowing fluid, L is the selected length of the pipe, ΔP is the pressure drop over the selected length of the pipe, and r o is a radius of the pipe, and K is an experimentally determined constant.
14. The method of claim 8 , further comprising estimating a viscosity of the flowing fluid based on the derived longitudinal relaxation times and a gas-oil ratio of the flowing fluid.
15. The method of claim 14 , wherein the estimating is according to:
η
o
=
kT
T
1
,
LM
·
f
(
GOR
)
where η o is the viscosity, k is an empirically determined constant for the flowing fluid, T is a temperature in Kelvin, T 1,LM is a logarithmic mean of the longitudinal relaxation times of the flowing fluid, and ƒ(GOR) is an empirically determined function of the gas-oil ratio.
16. A method for monitoring contamination in a flowing fluid being withdrawn into a formation fluid testing tool using nuclear magnetic resonance, comprising:
applying a static magnetic field to the flowing fluid;
acquiring a suite of nuclear magnetic resonance measurements of the flowing fluid using a pulse sequence comprising a spoiling pulse, a wait time, and an acquisition pulse sequence, wherein the suite of nuclear magnetic measurements have different values for the wait time;
fitting the suite of nuclear magnetic resonance measurements to a forward model for responses of the flowing fluid to derive a property of the flowing fluid; and
monitoring a level of contamination in the flowing fluid based on the derived property of the flowing fluid.
17. The method of claim 16 , wherein the property of the flowing fluid comprises one selected from a distribution of longitudinal relaxation times, a logarithmic mean of longitudinal relaxation times, and a combination thereof.
18. The method of claim 16 , wherein the property of the flowing fluid is a viscosity.
19. A nuclear magnetic resonance apparatus, comprising:
a flow pipe including a prepolarization section and an investigation section, wherein the prepolarization section is upstream of the investigation section;
a magnet disposed around the flow pipe for creating a static magnetic field covering the prepolarization section and the investigation section;
an antenna disposed around the flow pipe at the investigation section for generating an oscillating magnetic field having a magnetic dipole substantially perpendicular to a magnetic dipole of the static magnetic field, and for receiving a nuclear magnetic resonance signal; and
a circuitry for controlling generation of the oscillating magnetic field and reception of the nuclear magnetic resonance signal by the antenna, wherein the circuitry includes a program having instructions for acquiring a suite of nuclear magnetic resonance measurements of a flowing fluid using a pulse sequence comprising a spoiling pulse, a wait time, and an acquisition pulse sequence.
20. The apparatus of claim 19 , wherein the acquisition pulse sequence comprises one selected from a spin-echo pulse sequence and a single pulse.
21. The apparatus of claim 19 , wherein the program further comprises instructions for fitting the suite of nuclear magnetic resonance measurements to a forward model for responses of a flowing fluid to derive a parameter selected from a flow speed, longitudinal relaxation times of the flowing fluid, and a combination thereof.
22. The apparatus of claim 21 , wherein the fitting is performed by inversion of the forward model.
23. The apparatus of claim 21 , wherein the program further comprising instructions for estimating a viscosity of the flowing fluid based on the derived flow speed or the derived longitudinal relaxation times.
24. A nuclear magnetic resonance apparatus, comprising:
a flow pipe including a prepolarization section and an investigation section, wherein the prepolarization section is upstream of the investigation section;
a magnet disposed around the flow pipe for creating a static magnetic field covering the prepolarization section and the investigation section;
an antenna disposed around the flow pipe at the investigation section for generating an oscillating magnetic field having a magnetic dipole substantially perpendicular to a magnetic dipole of the static magnetic field, and for receiving a nuclear magnetic resonance signal; and
a circuitry for controlling generation of the oscillating magnetic field and reception of the nuclear magnetic resonance signal by the antenna, wherein the circuitry includes a program having instructions for acquiring a suite of nuclear magnetic resonance measurements of a flowing fluid using a pulse sequence comprising a longitudinal relaxation investigation pulse sequence and an acquisition pulse sequence, wherein the suite of nuclear magnetic measurements have different values for a delay time within the longitudinal relaxation investigation pulse.
25. The apparatus of claim 24 , wherein the acquisition pulse sequence comprises one selected from a spin-echo pulse sequence and a single pulse.
26. The apparatus of claim 24 , wherein the program further comprises instructions for fitting the suite of nuclear magnetic resonance measurements to a forward model for responses of a flowing fluid to derive a parameter selected from a flow speed, longitudinal relaxation times of the flowing fluid, and a combination thereof.
27. The apparatus of claim 26 , wherein the fitting is performed by inversion of the forward model.
28. The apparatus of claim 26 , wherein the program further comprising instructions for estimating a viscosity of the flowing fluid based on the derived flow speed or the derived longitudinal relaxation times.