Characterization of Brazilian tight gas sandstones relating permeability and Angstrom-to micron-scale pore structures

• Angstrom-to micron-scale pore structures characterization combining N2GA and MICP.
• Investigation of the implications of N2 adsorption and desorption branches in PSD results.
• Investigation of the BJH, D-H and DFT models and BET and Langmuir theories to achieve porosity and specific surface area.
• Dependency of effective stress and Klinkenberg slippage factors for PDP measurements.
• Estimation and validation of intrinsic permeability.

This work focuses on the characterization of the overall pore size distribution in tight gas sandstones originating from distinct Brazilian fields, as well as fluid flow circulation described by single-phase permeability. The former was achieved by the combination of nitrogen adsorption and mercury intrusion techniques and the latter estimated by empirical relations validated by the pulse-decay technique. The nature of nitrogen permeability change was investigated on tight gas core samples under a varying effective stress of 2–40 MPa, while the gas slippage was verified shifting mean pore pressures from 8.62 to 2.76 MPa in the laboratory pulse-decay. The best agreements between the estimated and measured permeabilities (from 0.00033 to 0.016 mD and from 0.0004 to 0.034 mD) reveal that obtained overall pore structure’ parameters play significant role in the results which were also supported by Field Emission Scanning Electron Microscopy (FESEM) and X-Ray Diffraction (XRD) analysis.

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