Abstract
This work investigates the morphological heterogeneity of pore systems in the carbonate rocks of the Canglangpu Formation, Sichuan Basin, aiming to explain the significant gas production disparity between two adjacent wells. An integrated methodology combining scanning electron microscopy (SEM) with digital image analysis was employed to classify pore morphologies and calculate fractal dimensions for 132 and 153 SEM images from Wells P7 and P9, respectively. The results demonstrate that Well P7 exhibits a more heterogeneous and intricate pore network, characterized by a higher median D value and a broader distribution, dominated by sub-circle pores across a wide complexity spectrum. In contrast, Well P9 possesses a more homogeneous pore structure with a lower, more clustered D value distribution. This morphological difference provides a mechanistic explanation for the production data, where the complex pore architecture of P7 likely impedes fluid flow, resulting in minimal production, while the more uniform system of P9 suggests better matrix connectivity. This matrix characteristic, combined with a more developed natural fracture network (the primary driver for high flow rates in such tight rock), correlates with its high daily gas output. In contrast, the complex pore architecture of P7 likely impedes matrix flow, contributing to its minimal production. The findings underscore that quantitative pore-scale characterization is critical for accurately assessing reservoir quality and predicting productivity in heterogeneous carbonate reservoirs, with direct implications for optimizing exploration and development strategies.
Data availability
The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.
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Acknowledgements
The authors gratefully acknowledge Dr. Xi Wu from the Analytical & Testing Center of Sichuan University for his help with the SEM characterization.
Funding
This study was financially supported by the National Natural Science Foundation of China (No. U2344209), PetroChina Scientific Research Project (No. 2023ZZ16YJ01) and Oil & Gas Major Project (No. 2025ZD1400400).
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Ya Zhang and Hongyu Long contributed to the study design and methodology development, with Ya Zhang leading the manuscript drafting and Hongyu Long overseeing data acquisition and SEM experiments. Yong Li, provided overall supervision, project administration, and funding acquisition. Yuan He and Di Chen performed the digital image analysis using ImageJ software, including pore parameter extraction and fractal dimension calculations. Chi Zhang and Chenglong Li were responsible for data validation, geological interpretation, and statistical analysis. Huachuan Jiang and Jing Wang prepared all figures, including the geological settings, methodology workflows, SEM examples, and fractal dimension plots, and contributed to visualization and manuscript review. All authors participated in writing, reviewing, and approving the final manuscript.
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Zhang, Y., Long, H., Li, Y. et al. Fractal dimension and morphological heterogeneity of pore in carbonate rocks: implications for production differences between adjacent wells. Sci Rep (2026). https://doi.org/10.1038/s41598-026-47223-0
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DOI: https://doi.org/10.1038/s41598-026-47223-0
