The traditional geological view holds that overpressure resists mechanical compaction during sedimentary burial, keeping effective stress approximately constant and thereby passively preserving porosity and permeability in deep reservoirs. However, this assumption has relied predominantly on theoretical inference and struggles to explain a widespread geomechanical paradox: in many overpressured formations, the magnitude of permeability enhancement significantly outpaces the degree of porosity preservation. To decode this paradox, we conducted a fundamental proof-of-concept study utilizing high-pressure percolation coupled with in situ micro-CT and fractal analysis to dynamically simulate the effects of overpressure on porous sandstone under constant mean effective stress. The results reveal a counterintuitive phenomenon: while the global porosity remained fundamentally stable, the absolute permeability demonstrated a significant ~8% enhancement. Microstructural analysis indicates that this enhancement is driven by localized hydraulic wedging and the reactivation of sub-resolution throats acting as topological bridges. This active topological optimization physically and mathematically manifests as: (1) the massive reconnection of macroscopic isolated pores; (2) an enhanced space-filling capacity of the flow network, evidenced by an increased coordination number and 3D pore space fractal dimension (D_f); and (3) the structural straightening of fluid pathways, rigorously quantified by a reduction in flow tortuosity and tortuosity fractal dimension (D_T). These findings, derived from a single well-characterized sandstone sample, demonstrate that overpressure-driven permeability enhancement is a physically plausible mechanism in tight sandstones. This discovery offers a candidate physical explanation for the anomalously high permeability observed in certain deep overpressured reservoirs. However, the generalizability of these results to reservoirs with differing porosities, mineralogies, and diagenetic histories remains to be evaluated through multi-sample studies.

Accurate prediction of overpressure in deep reservoirs is critical for hydrocarbon ex-ploration and development. Conventional approaches, such as interpolation of sin-gle-well pressure data and seismic inversion, often produce considerable errors and uncertainty when predicting overpressure in undrilled or inter-well areas, potentially leading to misinterpretation of reservoir pressure-field distributions. To address these limitations, this study proposes a novel approach that integrates identification of overpressure origins with quantitative analysis of the geological factors controlling overpressure magnitude. Multiple regression analysis enabled accurate prediction of overpressure in undrilled areas, with relative errors of less than 5% compared with measured pressures. Based on the conventional classification of normal and overpressure systems in the Bozhong area, three pressure-system types were identified: (1) paleo-overpressure converted to present-day normal pressure, (2) paleo-normal pressure retained as present-day normal pressure, and (3) paleo-overpressure preserved as present-day overpressure. The first type, character-ized by present-day pressure coefficients of 1.0–1.1, occurs predominantly near first- and second-order faults and is attributed to vertical fault opening and subsequent pressure release. The second type occurs mainly on structural slope highs and is asso-ciated with slow sedimentation rates and the absence of high-quality source rocks. The third type, with pressure coefficients ranging from 1.2 to 2.0, is primarily distributed in slope lows and depressions. It exhibits complex origins involving individual mecha-nisms, including undercompaction, hydrocarbon generation, pressure transfer, and tectonic compression, as well as coupled mechanisms, particularly undercompaction combined with hydrocarbon generation. This complex pressure system is controlled by several geological factors, including burial depth, sedimentation rate, vitrinite reflec-tance (Ro), total organic carbon content, fault throw, fault dip angle, and distance from faults.

Inorganic elements in crude oil have been used in the reconstruction of the sedimentary environment and oil–oil (source) correlations; however, the effect of biodegradation on these elements has not been investigated sufficiently. In this study, 14 crude oils from the Miaoxi Sag of the Bohai Bay Basin, eastern China, were analyzed using molecular markers, trace elements, and major elements to determine the effect of biodegradation on inorganic elements. The molecular markers indicated that the oils are in the low maturity stage and are derived from similar parent materials in lacustrine source rocks. The high-sulfur oil came from a more reductive and saltier environment compared with the low-sulfur oil. The oils were subjected to varying degrees of biodegradation. The concentrations of Mg, Ca, Mn, Fe, Be, Sc, Rb, Sr, Zr, Pb, Th, and U increased significantly throughout the biodegradation process, while the concentrations of Na, K, Ti, Al, Cr, Zn, Cs, Nb, Ba, Hf, and Tl increased considerably only during the intense biodegradation stage (PM < 4). The concentrations of P, Li, V, Co, Ni, Cu, Ga, Sn, and Ta were not correlated with the level of biodegradation. The V/Ni, V/Co, Ni/Co, Cr/V, Sc/V, and Th/U ratios were affected by biodegradation when PM ≥ 4. Several ratios, including Mg/P, Ca/P, Mn/P, and Fe/P, are proposed as favorable indicators of the level of biodegradation. Differential enrichment of these elements is associated with the effects of organic acids generated by biodegradation on the oil–water–rock interactions in the reservoir.

《地球科学》(ISSN 1000-2383;CN42-1874/P) (原刊名《地球科学——中国地质大学学报》ISSN 1000-2383;CN42-1233/P)，创刊于1957年，是由教育部主管、中国地质大学主办的综合性地学学术理论期刊，月刊，2015年改名为《地球科学》,她以反映中国地质大学教学与科研最新的、高水平的基础地质、应用地质、资源与环境地质及地学工程技术研究成果为主要任务。