NMR-Based Study of the Pore Types’ Contribution to the Elastic Response of the Reservoir Rock

• Main Authors: Naser Golsanami, Xuepeng Zhang, Weichao Yan, Linjun Yu, Huaimin Dong, Xu Dong, Likai Cui, Madusanka Nirosh Jayasuriya, Shanilka Gimhan Fernando, Ehsan Barzgar
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Energies
• Subjects: NMR relaxation; elastic response; statistical ensembles; deep learning; coalbed methane
• Online Access: https://www.mdpi.com/1996-1073/14/5/1513

Seismic data and nuclear magnetic resonance (NMR) data are two of the highly trustable kinds of information in hydrocarbon reservoir engineering. Reservoir fluids influence the elastic wave velocity and also determine the NMR response of the reservoir. The current study investigates different pore types, i.e., micro, meso, and macropores’ contribution to the elastic wave velocity using the laboratory NMR and elastic experiments on coal core samples under different fluid saturations. Once a meaningful relationship was observed in the lab, the idea was applied in the field scale and the NMR transverse relaxation time (T₂) curves were synthesized artificially. This task was done by dividing the area under the T₂ curve into eight porosity bins and estimating each bin’s value from the seismic attributes using neural networks (NN). Moreover, the functionality of two statistical ensembles, i.e., Bag and LSBoost, was investigated as an alternative tool to conventional estimation techniques of the petrophysical characteristics; and the results were compared with those from a deep learning network. Herein, NMR permeability was used as the estimation target and porosity was used as a benchmark to assess the reliability of the models. The final results indicated that by using the incremental porosity under the T₂ curve, this curve could be synthesized using the seismic attributes. The results also proved the functionality of the selected statistical ensembles as reliable tools in the petrophysical characterization of the hydrocarbon reservoirs.