Methods and apparatus for measuring capillary pressure in a sample

A method of measuring a parameter indicative of fluid content in a porous sample, comprising:

• measuring a parameter indicative of fluid content in each of a number of different portions of said sample comprising detecting said fluid by one dimensional magnetic resonance imaging along the sample in the direction of spatial separation between the different portions thereof using a phase encoded magnetic field gradient to spatially resolve each portion along the sample, wherein said magnetic resonance imaging comprises one dimensional single-point ramped imaging, which includes the steps of:
• (a) progressively increasing the gradient of a magnetic field directed in a first direction from zero to a predetermined maximum value;
• (b) applying to the sample an RF pulse at each of a number of different values of magnetic field gradient between zero and said predetermined maximum value;
• (c) detecting a nuclear magnetic resonance (nmr) signal from the sample resulting from each excitation pulse to provide a first set of data comprising respective values of magnetic field gradient and the respective values of the detected nmr signal from the sample;
• (d) after said magnetic field gradient reaches said predetermined maximum in said first direction, reducing said field gradient to zero without applying an RF pulse to said sample;
• (e) progressively increasing the gradient of a magnetic field directed in a second direction opposite to said first direction from zero to a predetermined maximum value;
• (f) applying an RF excitation pulse to the sample at each of a number of different values of magnetic field gradient between zero and said predetermined maximum value;
• (g) detecting a nuclear magnetic resonance signal from said sample resulting from each excitation pulse to provide a second set of data comprising respective values of magnetic field gradient and the respective values of the detected nuclear magnetic resonance signal from the sample;
• (h) determining the values of said parameter at said different positions along the sample from the first and second sets of data;
• and
• (i) outputting at least one of:
• (i) the values of said parameter;
• and
• (ii) data based on said values.

An apparatus for measuring a parameter indicative of fluid content in a porous sample comprising a magnetic resonance imaging system which includes a magnet for applying a static magnetic field to said sample, an RF pulse generator for applying RF excitation pulses to said sample, a detector for detecting magnetic induction signals from the sample, a generator for applying a magnetic field gradient to the sample and a controller for controlling the magnetic field gradient, wherein the magnetic resonance imaging system is operable to perform one dimensional single-point ramped imaging, in which said gradient controller is operative to progressively increase the gradient of a magnetic field directed in a first direction from zero to a predetermined maximum value;

• the RF pulse generator is operative to apply to the sample an RF pulse at each of a number of different values of magnetic field gradient between zero and said predetermined maximum value;
• said detector is operative to detect a nuclear magnetic resonance (nmr) signal from the sample resulting from each excitation pulse to provide a first set of data comprising respective values of magnetic field gradient and the respective values of the detected nmr signal from the sample, the magnetic field gradient controller being operative to reduce the field gradient to zero after said magnetic field gradient reaches said predetermined maximum in said first direction without applying an RF pulse to the sample and progressively increasing the gradient of a magnetic field directed in a second direction opposite to the first direction from zero to a predetermined maximum value;
• the RF pulse generator being operative to apply an RF excitation pulse to the sample at each of a number of different values of magnetic field gradient between zero and said predetermined maximum value, said detector being operative to detect a nuclear magnetic resonance signal from the sample resulting from each excitation pulse to provide a second set of data comprising respective values of magnetic field gradient and the respective values of the detected nuclear magnetic resonance signal from the sample, and
• determining means for determining the values of the parameter indicative of fluid content at said different positions along the sample from the nmr signals in the first and second sets of data.