A rapid measurement of T1/T2: The DECPMG sequence

The Driven-Equilibrium Carr-Purcell Meiboom-Gill (DECPMG) pulse sequence is a rapid method for obtaining the average ratio of longitudinal to transverse relaxation times 〈T1/T2〉 as a function of T2. Since this is a one-dimensional experiment, the 〈T1/T2〉T2 ratio can be acquired, potentially, in just two scans; the second scan being a reference CPMG measurement. Conventionally, T1/T2 is determined from a two-dimensional T1-T2 relaxation correlation experiment. The method described here offers a significant reduction in experimental time without a reduction in signal-to-noise. The 〈T1/T2〉 ratio is useful for comparing the behaviour of liquids in porous media. Here we demonstrate the application of the DECPMG sequence to the study of oil-bearing rocks by differentiating oil or water saturated rock cores, and by observing the relative strengths of surface interaction for water in two types of rock by measuring 〈T1/T2〉 as a function of magnetic field strength.