Comparative Study on Applicability of Permeability Testing Methods in Shale Reservoirs

Area of Science:

• Petroleum Geoscience
• Reservoir Engineering
• Unconventional Resources

Background:

• Permeability is critical for evaluating and predicting production in shale oil and gas reservoirs.
• Extremely low porosity and permeability in shale present significant development challenges.
• Accurate permeability characterization is essential for effective shale reservoir management.

Purpose of the Study:

• To systematically analyze and optimize test methods for shale reservoir permeability.
• To establish a new, high-precision nuclear magnetic resonance (NMR) based model for permeability characterization.
• To validate the compatibility of the new model with experimental data.

Main Methods:

• Comparative analysis of steady-state, pulse decay, and nuclear magnetic resonance (NMR) methods.
• Development of a novel NMR single-parameter model using T_w.
• Experimental verification of the model's accuracy and correlation with existing methods.

Main Results:

• The new NMR model with T_w as the primary parameter accurately calculates shale reservoir permeability (10^-3 - 10^0 mD).
• A high correlation coefficient (96.31%) was observed between weighted average relaxation time and the pulse decay method.
• The new model demonstrated a low relative error (19.43%) compared to pulse permeability measurements.

Conclusions:

• The developed T_w NMR model provides a highly accurate and reliable method for shale reservoir permeability characterization.
• This research establishes a theoretical foundation for quantitatively assessing fluid seepage capacity in challenging shale formations.
• Optimized permeability assessment using NMR enhances the potential for efficient development and production of unconventional energy resources.