Method for nuclear magnetic resonance diffusion measurements

A method for determining a property of a substance using nuclear magnetic resonance (NMR), the method comprising:

• applying a NMR pulse sequence comprising a first set of pulses and a second set of pulses to the substance, wherein the first set of pulses and the second set of pulses encode for overlapping diffusion times;
• detecting a NMR signal produced by the NMR pulse sequence to obtain NMR signal data;
• and
• determining the property of the substance using the NMR signal data over each of the overlapping diffusion times wherein the substance is a fluid within an underground formation and the NMR sequence is applied to the fluid using a NMR logging tool.

A method for determining a property of a substance using nuclear magnetic resonance (NMR), the method comprising:

• applying an NMR pulse sequence to the substance, wherein (i) the NMR pulse sequence comprises a first set of pulses and a second set of pulses, (ii) the first set of pulses and the second set of pulses encode for a first diffusion time and a second diffusion time, (iii) the first diffusion time and a second diffusion time overlap, (iv) the first set of pulses comprises two pulses that are each defined by a first area parameter and separated by a time period, and (v) the second set of pulses comprises two pulses that are each defined by a second area parameter and separated by the time period;
• detecting a NMR signal produced by the NMR pulse sequence to obtain NMR signal data;
• applying the NMR pulse sequence and detecting the NMR signal produced by the NMR pulse sequence a number of times using different values for at least one of the first area parameter and the second area parameter;
• performing a Laplace inversion on the NMR signal data to obtain diffusion coefficients for the first diffusion time and the second diffusion time;
• and
• determining the property of the substance using the diffusion coefficients.