Petrophysical characterization of low-permeable carbonaceous rocks: Comparison of different experimental methods

摘要: Abstract Pore structure and gas transport properties of fourteen samples from the Jurassic Sargelu Cretaceous Garau formations in Lurestan province, southwest Iran, were studied under aspect shale exploration production. Porosity was determined by helium pycnometry water saturation (Archimedes principle). Low-pressure adsorption N2 used to determine total pore volumes, specific surface areas microporosity. High-pressure mercury intrusion porosimetry (MIP) applied assess pore-size distributions. Permeability measurements performed with methane at confining pressures 40 10 MPa using steady state non-steady methods. porosity values different methods are a good agreement. For low-permeable (less than 1 microdarcy ~ 10−18 m2) “constant downstream pressure” technique is most efficient method for slip flow evaluation (Klinkenberg plot), yielding apparent permeability coefficients over wide range reciprocal mean (1/pmean) one single run. A positive correlation found between TOC content, coefficients. Samples displaying clear signs recrystallization tend exhibit higher permeability. None parameters this study, however, showed mineralogy. The relationship Klinkenberg-corrected pressure could be expressed an exponential decay function. Stress sensitivity typically samples. containing highly recrystallized carbonates exhibited lower stress sensitivity, indicating increase rigidity due recrystallization. No methane/helium ratios, sorption capacity, contents. Thus, sample set not affected and/or swelling organic matter.