Abstract The pore network attributes help assess the fluid-flow behaviour in various reservoir rocks. As, in the cases of various unconventional energy exploration, the reservoir rocks are being exposed to different sets of temperatures that result in microstructural alteration in the pore and throat scale. Since the last decade, X-ray computed tomography (XCT) has been proved to be a useful tool in determining the micro-scale pore structures. However, such results are greatly influenced by the structure of the rocks, pore spaces, grain size, and nature of minerals. Here in this study, an attempt has been made to investigate the microstructural alteration and pore-network configuration of thermally-treated three Indian sandstones (Dholpur sandstone, Jodhpur sandstone and Gondwana sandstone) of varying mineralogy using the high-resolution micro-CT techniques. Microstructural modifications, the evolution of pores spaces, pore-size distribution, pore-network attributes such as nature of connectivity, pore radius, pore-volume, pore coordination number, throat radius and throat channel lengths of the three sandstones were investigated in a temperature range from 25 °C to 800 °C. The microstructural responses of these sandstones in terms of pore-space evolution and pore network models were found to be dependent on the presence of clay minerals. The overall trend of porosity for Dholpur and Gondwana sandstone was found to increase as a function of temperature. For Jodhpur sandstone, the maximum porosity was achieved at 600 °C and thereafter a decreasing trend up to 800 °C. Gondwana sandstone, most clay-rich, was found to be most vulnerable to elevated temperatures compared to the other two sandstones. The maximum average pore coordination number for Dholpur and Jodhpur sandstone was observed at 600 °C (7.097) and 800 °C (6.953), respectively.

中文翻译：

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使用计算机断层扫描深入了解高温热处理砂岩的孔隙网络模型

摘要 孔隙网络属性有助于评估各种储层岩石中的流体流动行为。因为，在各种非常规能源勘探的情况下，储层岩石暴露在不同的温度下，导致孔隙和喉道尺度的微观结构变化。自过去十年以来，X 射线计算机断层扫描 (XCT) 已被证明是确定微尺度孔隙结构的有用工具。然而，这些结果受岩石结构、孔隙空间、粒度和矿物性质的影响很大。在本研究中，尝试研究热处理后的三种印度砂岩（Dholpur 砂岩、焦特布尔砂岩和冈瓦纳砂岩），使用高分辨率显微 CT 技术。研究了三种砂岩的微观结构改造、孔隙空间演化、孔径分布、连通性、孔隙半径、孔隙体积、孔隙配位数、喉道半径和喉道长度等孔隙网络属性。温度范围为 25 °C 至 800 °C。发现这些砂岩在孔隙空间演化和孔隙网络模型方面的微观结构响应取决于粘土矿物的存在。发现 Dholpur 和 Gondwana 砂岩的孔隙度总体趋势随着温度的增加而增加。对于焦特布尔砂岩，最大孔隙度在 600 °C 时达到，此后在 800 °C 时呈下降趋势。冈瓦纳砂岩，与其他两种砂岩相比，最富含粘土的砂岩被发现最容易受到高温的影响。Dholpur 和 Jodhpur 砂岩的最大平均孔隙配位数分别在 600 °C (7.097) 和 800 °C (6.953) 下观察到。