Quantitative magnetic resonance imaging methods for core analysis

Abstract

AbstractThe majority of sedimentary rocks have significant paramagnetic impurities, which lead to magnetic resonance signal lifetimes too short to be detected by clinical magnetic resonance imaging (MRI) methods. Quantitative information is the ultimate goal for rock-core analysis. The SPRITE (single-point ramped imaging with T1 enhancement) imaging technique has proven to be a very robust and flexible method for the study of a wide range of systems with short signal lifetimes. As a pure phase-encoding technique, SPRITE is largely immune to image distortions generated by susceptibility variations, chemical shift and paramagnetic impurities, unlike clinical magnetic resonance imaging methods. It enables systems with transverse lifetimes as short as tens of microseconds to be successfully visualized. Our experimental results show that most sedimentary rocks have a single exponential transverse magnetization decay for T*2, which suggests that quantitative imaging of local fluid content can be easily obtained. Some examples of MRI techniques are represented that reveal internal sedimentary characteristics and heterogeneity. In addition, the application of quantitative MRI techniques to examine flow mechanisms in rock cores is outlined.