Nuclear magnetic resonance pulse sequences for use with borehole logging tools

摘要: An NMR pulse sequence for use in the borehole environment is provided which combines a modified fast inversion recovery (FIR) with series of more than ten, and typically hundreds, CPMG pulses according to [W.sub.i -180-τ.sub.i -90-(t.sub.cp -180-t.sub.cp -echo).sub.j ].sub.i where j index echoes gathered, i wait times sequence, Wi are times, before pulses, tcp Carr-Purcell spacing. Measurements made signals induced formation as result magnetic fields. Determinations Mo and/or T1 then from measurements relationships relate Mpo, T2 signal magnitude. Other provide stretched exponentials or multiple can also be used. From determinations, parameters such porosity permeability may derived equations known art. In obtaining most accurate determinations least amount time, various (I, J, Wi, τi) optimized prior logging. Additional accuracy obtained by integrating gated portion rather measuring amplitude, utilizing phase alternated repetitive order eliminate baseline shift error.