Flow Measurement Using NMR
AssigneeSchlumberger Technology Corporation
InventorKrishnamurthy Ganesan
Life of this patent
Estimating the term…
Abstract
A nuclear magnetic resonance (NMR) method is used to determine a velocity distribution or velocity image of a flowing fluid in a downhole environment. The method comprises applying a radio frequency pulse sequence; applying a magnetic field gradient magnetic field and a gradient pulse duration; measuring a NMR signal; determining a phase characteristic of the NMR signal; and determining the velocity distribution or image of the fluid using the determined phase characteristic, the magnetic field gradient pulse parameters, and a time delay between gradient pulses.
Claims21
A method to determine a velocity distribution of a flowing fluid using a nuclear magnetic resonance (NMR) tool disposed in a wellbore, comprising:
- apply a radio frequency pulse sequence;
- applying a magnetic field gradient pulse sequence, wherein each magnetic field gradient pulse has parameters including a gradient magnetic field and a gradient pulse duration;
- measuring a NMR signal;
- determining a phase characteristic of the NMR signal;
- and
- determining the velocity distribution of the fluid using the determined phase characteristic, the magnetic field gradient pulse parameters, and a time delay between gradient pulses.
a method to determine a velocity image of a flowing fluid using a nuclear magnetic resonance tool disposed in a wellbore, comprising:
- applying a radio frequency pulse sequence;
- applying a magnetic field gradient pulse sequence, wherein each magnetic field gradient pulse has parameters including a gradient magnetic field and a gradient pulse duration;
- measuring a NMR signal;
- repeating, for a desired number of times, the applying the radio frequency and gradient pulse sequences using different values of the gradient parameters, and the measuring NMR signals;
- determining a phase characteristic from the NMR signals;
- and
- determining the velocity image of the fluid using the determined phase characteristic, the magnetic field gradient pulse parameters, and a time delay between gradient pulses.
A method to determine the magnitude of a gradient magnetic field using a nuclear magnetic resonance tool disposed in a wellbore, comprising:
- applying a radio frequency pulse sequence;
- applying a magnetic field gradient pulse sequence, wherein each magnetic field gradient pulse has parameters including a gradient magnetic field and a gradient pulse duration;
- measuring a NMR signal in the presence of a gradient pulse;
- determining a frequency spread from the NMR signal;
- and
- determining the magnitude of the gradient magnetic field using the frequency spread.
A downhole nuclear magnetic resonance apparatus to determine a velocity distribution of a flowing fluid in a downhole environment, comprising:
- a magnet configured to generate a substantially homogeneous magnetic field in a region of investigation;
- an antenna configured to receive an electromagnetic signal from the region of investigation;
- one or more coils configured to generate a magnetic field gradient int he region of investigation;
- an electronics module to determine a NMR signal from the electromagnetic signal received by the antenna;
- and
- a processor to determine a phase characteristic from the NMR signal and the velocity distribution of the flowing fluid using the determined phase characteristic.
A downhole system to determine a flow property of a formation fluid flowing in a flowline, comprising:
- a formation fluid testing tool;
- and
- a nuclear magnetic resonance tool comprising:
- a magnet configured to generate a substantially homogeneous magnetic field in a region of investigation;
- an antenna configured to receive an electromagnetic signal from the region of investigation;
- one or more coils configured to generate a magnetic field gradient in the region of investigation;
- an electronics module to determine a NMR signal from the electromagnetic signal received by the antenna;
- and
- a processor to determine a phase characteristic from the NMR signal and the velocity distribution of the flowing fluid using the determined phase characteristic.
Dependencies are inferred from the claim text.