The effects of high debris content on pore structure in tight sandstone reservoirs tight sandstone reservoirs are multifaceted. Pore structure is an important factor controlling reservoir quality. Clarifying the effects of different types of rock debris on reservoirs is necessary to study the pore structure and their control factors of tight sandstones. The Western Sichuan Depression with complex rock components, containing multiple types of rock debris, leads to strong heterogeneity of pore throats, so it is necessary to study the factors controlling the development of different types of pore throats in tight reservoirs. In this paper, the Fourth member of Xujiahe Formation (T₃x⁴) is taken as the research object. Based on high-pressure mercury intrusion experiments and the fractal theory, the types of pore throats and their heterogeneity in tight reservoirs were studied, the relationship of fractal dimensions with reservoir physical properties, pore structure, and rock compositions were investigated, and then the controlling factors for the development of different types of pore throats are clarified. The studies show that there are four types of pore throats developed in the T₃x⁴ of the western Sichuan depression, including primary intergranular pore-throats (>350 nm), residual intergranular pore-throats (75–350 nm), dissolution pore-throats (16–75 nm), and intercrystalline pore-throats (<16 nm), among which the homogeneity of dissolution pore-throats are the best, followed by residual intergranular pore-throats and intercrystalline pore-throats, and the primary intergranular pore-throats the most heterogeneous. The permeability has a better relationship with the proportion and fractal dimension of primary intergranular pore-throats and residual intergranular pore-throats of tight reservoir of the Xujiahe Formation. The relation-ship between porosity and the proportion and fractal dimension of primary intergranular pore-throats and dissolution pore-throats is better. Brittle minerals such as quartz and metamorphic debris, as well as early developed films of chlorite and illite mainly control the development of intergranular pore-throats. Potassium feldspar mainly controls the development of dissolution pore-throats, while sedimentary rock debris, volcanic debris, and kaolinite play a destructive role for all types of pore-throats. The high-quality reservoirs in the T₃x⁴ are controlled by the development of primary intergranular pore throats and dissolution pore throats, and they are mainly developed in environments with strong hydrodynamic conditions, large rock grain sizes, high content of brittle minerals such as quartz and metamorphic debris, extensive development of chlorite and illite films, and low content of sedimentary rock debris, matrix, and cemented materials. This study is of guiding significance in clarifying the causes of heterogeneity in different types of pore-throat systems in tight sandstones and the formation mechanism of high-quality reservoirs in tight sandstones with high content of debris.

The Upper Triassic Xujiahe Formation (T₃x) represents a critical terrestrial source rock system in the Sichuan Basin, exhibiting pronounced vertical and lateral heterogeneity. Previous stratigraphic subdivisions relied primarily on lithological correlations rather than a systematic sequence stratigraphic framework. This approach has led to significant inconsistencies in source rock evaluation. Furthermore, recent discoveries of large gas fields, coupled with data from newly drilled wells, necessitate a comprehensive reassessment of this system. In this study, we re-evaluate the geochemical characteristics and spatial distribution of these source rocks within a newly established sequence stratigraphic framework. This assessment utilizes a robust dataset comprising total organic carbon (TOC) content, Rock-Eval pyrolysis, and vitrinite reflectance (Ro) measurements. The results indicate that the source rocks of the New Member 5 (T₃x⁵) in the slope belt of Central Sichuan exhibit the highest hydrocarbon generative potential. These rocks are characterized by high organic abundance (with 40% of samples showing TOC ≥ 2.0 wt.%), are dominated by Type III and II₂ kerogen (humic–sapropelic), and have reached the mature to high-maturity stage (Ro ranging from 1.0% to 1.7%). Notably, the cumulative thickness of these high-quality source rocks reaches 100~150 m. Specifically, the T₃x⁵ intervals in the Qiulin and Tianfu areas are identified as the most favorable hydrocarbon-generating centers. This reassessment under the new stratigraphic division provides a refined theoretical basis for future exploration targeting the Xujiahe Formation in the Sichuan Basin.

The effects of high debris content on tight sandstone reservoirs are multifaceted. Pore structure is an important factor controlling reservoir quality. Clarifying the effects of different types of rock debris on reservoirs is necessary to study the pore structure and their control factors of tight sandstones. The Western Sichuan Depression with complex rock components, containing multiple types of rock debris, leads to strong heterogeneity of pore throats, so it is necessary to study the factors controlling the development of different types of pore throats in tight reservoirs. In this paper, the Fourth member of Xujiahe Foramtion(T3x4) is taken as the research object. Based on high-pressure mercury intrusion experiments and the fractal theory, the types of pore throats and their heterogeneity in tight reservoirs were studied, the relationship of fractal dimensions with reservoir physical properties, pore structure, and rock compositions were investigated, and then the controlling factors for the development of different types of pore throats are clarified. The studies show that there are four types of pore throats developed in the T3x4 of the western Sichuan depression, including primary intergranular pore-throats, residual intergranular pore-throats, dissolution pore-throats, and intercrystalline pore-throats, among which the homogeneity of dissolution pore-throats are the best, followed by residual intergranular pore-throats and intercrystalline pore-throats, and the primary intergranular pore-throats the most heterogeneous. Brittle minerals such as quartz and metamorphic debris, as well as early developed films of chlorite and illite mainly control the development of intergranular pore-throats. Potassium feldspar mainly controls the development of dissolution pore-throats, while plastic debris, volcanic debris, and kaolinite play a destructive role for all types of pore-throats. The high-quality reservoirs in the T3x4 are controlled by the development of primary intergranular pore throats and dissolution pore throats, and they are mainly developed in environments with strong hydrodynamic conditions, large rock grain sizes, high content of brittle minerals such as quartz and metamorphic debris, extensive development of chlorite and illite films, and low content of mudstone debris, matrix, and cemented materials. This study is of guiding significance in clarifying the causes of heterogeneity in different types of pore-throat systems in tight sandstones and the formation mechanism of high-quality reservoirs in tight sandstones with high content of debris.