Nuclear magnetic resonance (NMR) physical principles and evaluation techniques have been utilized and applied in conventional sandstone-and carbonate dominated reservoir applications for decades. The nuclear physical principles relying on a time versus spin echo amplitude response of protons after excitation and full polarization in the down-hole environment have long been understood to quantify the relaxation-decay of atomic molecules residing within given pore space in a formation. With respect to the characterization of unconventional play types using NMR, including hybrid thinly-bedded source and reservoir lithologies, legacy NMR tool physics and acquisition parameters need to be re-evaluated and calibrated to these challenging environments for accurate quantification.
In this study variable open-hole wireline acquisition settings in nuclear magnetic resonance tools were used by investigating and quantifying the impact of these logging parameters on raw and processed results (i.e. pore space binning schemes and moveable versus bound fluid in defined pore space distributions). Investigation and quantification based on the variation in the following parameters as applied in a hybrid shale-reservoir formation are displayed: 1. Number of wait time echoes, 2. Signal acquisition variation, 3. Larmor-Frequency Tuning sensitivity, 4. Number of Bursts per Echo, 5. Wait time bursting sequence, 6. Polarization correction, 7. Up hole stacking interval (note inter echo-spacing was not adjusted and the standard acquisition for these purposes was 0.2 ms). Post down-hole acquisition and initial inversion for T2 distributions were investigated and quantify sensitivity in the following; 1. Binning Scheme (Varying summed pore space), 2. Cutoffs, 3. Moveable versus Bound Fluid. These results can guide the petrophysical calibration and quantification of various pore space distributions for a complex, heterogeneous source-reservoir play. Improved reservoir property characterization and understanding can lead to advanced petrophysical integration and inter-disciplinary understandings.
