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

中文翻译：

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低渗透碳质岩的岩石物理特征：不同实验方法的比较

摘要 在页岩气勘探开发方面，对伊朗西南部卢雷斯坦省侏罗系Sargelu组和白垩系Garau组14个样品的孔隙结构和输气性质进行了研究。孔隙率由氦比重瓶和水饱和度（阿基米德原理）确定。N2 的低压吸附用于确定总孔体积、比表面积和微孔率。高压压汞孔隙率测定法 (MIP) 用于评估孔径分布。使用稳态和非稳态方法在 40 至 10 MPa 的围压下用氦气和甲烷进行渗透率测量。由不同方法确定的渗透率和孔隙率值具有很好的一致性。对于低渗透性样品（小于 1 microdarcy ~ 10−18 m2），“恒定下游压力”技术是滑流评估的最有效方法（Klinkenberg 图），在很宽的倒数平均压力范围内产生表观渗透系数（ 1/pmean) 一次运行。发现 TOC 含量、孔隙度和渗透系数之间呈正相关。显示出明显再结晶迹象的样品往往表现出更高的渗透率。然而，本研究中确定的参数均未显示与矿物学相关。Klinkenberg 修正渗透系数和围压之间的关系可以用指数衰减函数表示。低渗透性样品的应力敏感性通常更高。含有高度重结晶碳酸盐的样品表现出较低的应力敏感性，表明由于重结晶导致刚度增加。未发现甲烷/氦气渗透率比、吸附能力和 TOC 含量之间存在相关性。因此，该样品组的气体传输特性不受有机物吸附和/或溶胀的影响。