Liu Liang, Huang Guoshu, Ding Hui, Li Gongqiang, Ma Senyao
Department of Earth Science and Engineering, Shanxi Institute of Technology, Yangquan, 045000, China.
Key Laboratory of Deep Geothermal Resources, MNR, Wuhan, 430074, China.
Sci Rep. 2025 Jul 1;15(1):22383. doi: 10.1038/s41598-025-06236-x.
In the central region of the Lower Shihezi Formation within the Hangjinqi Gas Field, Ordos Basin, China, gas-bearing tight sandstone reservoirs exhibit a coexistence of low-resistivity and medium-to-high-resistivity characteristics. These reservoirs are characterized by significant resistivity fluctuations, posing challenges to the accurate calculation of gas saturation using the classical Archie equation and its derivatives. Consequently, both qualitative and quantitative evaluations of gas-bearing tight sandstone reservoirs are often hindered. To address these complexities, a comprehensive analysis was conducted utilizing an integrated dataset comprising mercury intrusion porosimetry (MIP), conventional thin-section petrography, whole-rock and clay mineral analyses, scanning electron microscopy (SEM), natural gamma ray (GR), spontaneous potential (SP), deep and shallow lateral resistivity (LLD and LLS), array induction resistivity (HDIL), acoustic travel time (AC), density (DEN), neutron (CNL), and nuclear magnetic resonance (NMR) logging data. The results demonstrate that among various factors influencing resistivity-including sedimentary characteristics, clay mineral distribution, porosity, pore structure, and gas content-porosity within distinct pore size ranges is the primary controlling factor driving resistivity variations. Specifically, analysis of NMR T spectrum data reveals that low resistivity is predominantly associated with porosity in the 3-12 ms pore size range, while high resistivity is primarily controlled by porosity in ranges exceeding 24 ms and below 12 ms. These findings enhance the understanding of the mechanisms underlying resistivity fluctuations in gas-bearing reservoirs. This understanding is essential for improving the accuracy of reservoir identification and optimizing development strategies, offering valuable insights for the exploration and exploitation of similar reservoirs worldwide.
在中国鄂尔多斯盆地杭锦旗气田石盒子组下段中部地区，含气致密砂岩储层呈现出低电阻率与中高电阻率特征并存的情况。这些储层的电阻率波动显著，给利用经典阿尔奇方程及其衍生公式准确计算含气饱和度带来了挑战。因此，含气致密砂岩储层的定性和定量评价常常受到阻碍。为应对这些复杂情况，利用包括压汞法（MIP）、常规薄片岩石学、全岩和黏土矿物分析、扫描电子显微镜（SEM）、自然伽马射线（GR）、自然电位（SP）、深浅双侧向电阻率（LLD和LLS）、阵列感应电阻率（HDIL）、声波时差（AC）、密度（DEN）、中子（CNL）以及核磁共振（NMR）测井数据在内的综合数据集进行了全面分析。结果表明，在影响电阻率的各种因素中，包括沉积特征、黏土矿物分布、孔隙度、孔隙结构和含气率，不同孔径范围内的孔隙度是驱动电阻率变化的主要控制因素。具体而言，对NMR T2谱数据的分析表明，低电阻率主要与孔径在3 - 12毫秒范围内的孔隙度相关，而高电阻率主要受孔径超过24毫秒和低于12毫秒范围内的孔隙度控制。这些发现加深了对含气储层电阻率波动机制的理解。这种理解对于提高储层识别的准确性和优化开发策略至关重要，为全球类似储层的勘探和开发提供了有价值的见解。
