Comparative Study on Applicability of Permeability Testing Methods in Shale Reservoirs.

Abstract

Permeability is one of the important parameters for reservoir evaluation, development, and production prediction. Shale oil and gas being an important unconventional energy source, the characteristics of extremely low porosity and permeability bring great challenges to development. Therefore, it is crucial to accurately describe the permeability of shale reservoirs. Based on the steady-state method, pulse decay method, and nuclear magnetic resonance (NMR) method, this paper systematically analyzed the adaptability of various test methods in shale reservoir permeability characterization and optimized the best test method. On this basis, a new high-precision NMR single parameter Tw of shale reservoirs is established, and the compatibility between the model and the experimental results is verified. The results show that the new model with Tw as the main parameter is the most accurate one to calculate the permeability of shale reservoirs in the range of 10–3–100 mD. The correlation coefficient between the weighted average relaxation time and pulse decay method is as high as 96.31%, and the relative error between the permeability predicted by the new model and the pulse permeability is 19.43%. These studies have laid a theoretical foundation for the quantitative characterization of fluid seepage capacity in shale reservoirs.