ORIGINAL RESEARCH article
Front. Earth Sci.
Sec. Economic Geology
This article is part of the Research TopicAdvances in Accumulation Conditions of Unconventional Oil and Gas Resources in Complicated Structure AreasView all 15 articles
Fractal Characteristics of Full-scale Pores and Throats in Tight Sandstone and its application in analysis of main controlling factors of reservoir
Provisionally accepted
- Natural Gas Research Institute of Yanchang Petroleum(Group) Co. LTD, xi'an, China
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Comprehensive and accurate characterization of pore–throat structures is essential for rational resource assessment and enhanced recovery rate in tight sandstone reservoirs. However, the fractal characteristics of full-scale pores and throats in tight sandstones remain poorly understood. In this study, high-pressure mercury intrusion (HPMI), constant-rate mercury intrusion (CRMI) and nuclear magnetic resonance (NMR) experiments are integrated to provide a full-scale characterization of pore and throat distributions in tight sandstone samples. Fractal dimensions are calculated separately for pores and throats using a wetting-phase model and a 3D capillary tube model. Based on these results, seven pore–throat systems are identified: (1) small bundle-like throats within clay interstitial filler; (2) medium tubular/sheet throats generated by intense compaction; (3) large throats formed by localized dilation of tubular/sheet throats; (4) micro pores created by localized constriction of submicron-micron sized intergranular pores; (5) small pores dominated by intragranular dissolution pores; (6) medium pores consisting mainly of residual intergranular pores; and (7) large pores resulting from the combination of moldic pores and residual intergranular pores. Moreover, the reservoir space exhibits a ternary structural characteristic. Both small and medium throats conform to capillary-tube assumption, with mean fractal dimensions of 2.2093 and 2.7214, respectively. Small, medium and large pores fit the spherical assumption, with mean fractal dimensions of 2.8180, 2.7435 and 2.9825, respectively. Extensive overlap between large throats and micropores forming a beaded pore-throat network for which an appropriate fractal model is currently lacking. Porosity and permeability of the samples in this study are primarily controlled by medium pores and medium throats, followed by small pores, while movable fluid resides predominantly within medium pores. The results suggest that relatively weak compaction is a key factor in the development of high-quality reservoirs in the strata studied. The proposed full-scale classification scheme based on fractal dimensions offers new insights into the microscopic heterogeneity of tight sandstones. Furthermore, the full-scale characterization combined with correlation analysis and pore–throat genesis discrimination provides targeted strategies for exploration of high-quality tight sandstone reservoirs.
Keywords: Controlling factor, ternary pore-throat structure, pore-throat system, fractal dimension, Full-scale, reservoir, Tight sandstone
Received: 08 Sep 2025; Accepted: 26 Nov 2025.
Copyright: © 2025 Feng, Wang, Liu and Gao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Linjie Feng
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