Tracking pore to pore exchange using relaxation exchange spectroscopy.

Area of Science:

• Geology
• Geophysics
• Materials Science

Background:

• Understanding fluid flow in porous media is crucial for resource exploration and management.
• Sandstone reservoirs exhibit complex pore structures influencing fluid transport.
• Nuclear Magnetic Resonance (NMR) is a powerful tool for probing pore structures and fluid dynamics.

Purpose of the Study:

• To observe and quantify water movement between pores of different sizes in Castlegate sandstone.
• To develop a method for extracting characteristic exchange times for various pore sizes.
• To assess the utility of this method for permeability determination and understanding pore subpopulation interactions.

Main Methods:

• Utilized NMR transverse relaxation exchange experiments with varying mixing times.
• Applied a 2D inverse Laplace transform (ILT) to convert relaxation data into 2D T2 distributions.
• Performed quantitative analysis on the resulting ILT distributions.

Main Results:

• Successfully observed and quantified water movement between pores of differing sizes.
• Demonstrated for the first time that quantitative ILT analysis can extract characteristic pore exchange times.
• Identified distinct exchange behaviors associated with different pore size populations.

Conclusions:

• Quantitative analysis of 2D T2 distributions from NMR relaxation exchange experiments provides valuable insights into pore-scale fluid dynamics.
• The extracted characteristic times offer a novel approach for estimating permeability.
• This technique enhances the understanding of fluid exchange between specific pore subpopulations in sedimentary rocks.