Unconventional oil and gas resources-such as shale oil and gas, volcanic rock oil and gas, and tight sandstone oil and gas-have become an indispensable part of the global energy structure, offering a critical solution to surging energy demand and the gradual depletion of conventional reserves (Zou et al., 2013;Guo et al., 2025). However, exploring and developing these resources in complicated structure areas-characterized by intricate tectonic activities, diverse sedimentary environments, and heterogeneous reservoirs-poses formidable challenges to understanding hydrocarbon accumulation mechanisms (Li et al., 2018;Wang et al., 2024;Guo et al., 2025). Addressing these requires systematic research to unravel key controlling factors, laying the groundwork for efficient and sustainable exploitation. Deepening the understanding of their accumulation rules not only enriches the theoretical framework of oil and gas geology but also provides crucial support for optimizing energy structures and promoting sustainable energy development, which is the core goal of this research topic. This research topic, Advances in Accumulation Conditions of Unconventional Oil and Gas Resources in Complicated Structure Areas, compiles 15 original studies that comprehensively explore unconventional oil and gas accumulation across complex geological settings in China. Covering reservoir characterization, organic matter enrichment, geological impacts, advanced detection technologies, migration mechanisms, and reservoir protection, these works collectively build a multidimensional understanding of accumulation processes, providing valuable theoretical and practical support for exploration and development.Multiple studies in this research topic focus on deciphering the characteristics of different unconventional reservoir types and their controlling factors. Reservoir properties are fundamental to evaluating accumulation potential, and these studies provide targeted insights for various reservoir types.Feng et al. investigated fractal characteristics of full-scale pores and throats in tight sandstones, revealing the link between pore-throat heterogeneity and reservoir quality. They established a quantitative method for analyzing key controls, highlighting the role of fractal dimensions in determining permeability and storage capacity-offering a new perspective for tight sandstone evaluation.Gao et al. focused on He-8 Member tight sandstones in the eastern Yanchuan area of the Yan'an Gas Field, integrating petrological, petrophysical, and geological data. They identified sedimentary facies, diagenesis, and fractures as key factors: favorable facies provide material basis, constructive diagenesis (e.g., dissolution) enhances pore connectivity, and fractures act as migration channelsdelivering targeted insights for local reservoir optimization.In the Western Sichuan Depression, Wang et al. studied Triassic Xu5 tight sandstone reservoirs, finding that interactions between sedimentary environments, diagenesis, and tectonics shape reservoir properties. Tectonic compression controls sedimentary distribution and induces high-angle fractures, significantly improving low-permeability reservoir connectivity. This underscores tectonism's critical role in complex structure areas, aiding favorable zone identification.Huang et al. analyzed the low-permeability to tight transition zone of the Jishan Sandstone in the Huimin Sag of the Jiyang Depression, revealing unique properties that combine conventional reservoirs' high porosity and tight reservoirs' strong hydrocarbon retention. Clarifying enrichment rules here provides a new direction for exploring similar transition zones.Reservoir heterogeneity is a major challenge, especially in marine-continental transitional shales. Wang et al. studied heterogeneity in coal-bearing Permian Longtan Formation shales in the Central Sichuan Basin, emphasizing lithofacies as dominant controls. Different lithofacies show distinct properties, and interbedding of organic-rich shale and coal seams enhances sealing and preservationproviding a framework for shale gas "sweet spot" selection.Igneous rock reservoirs, a special unconventional type highlighted in the call for papers, have gained attention for their formation mechanisms. Echoing the call for papers' attention to buried hill igneous rock reservoirs, Chen et al. studied high-quality Mesozoic igneous reservoirs in the Qikou Sag, identifying magmatic intensity, late tectonic reformation, and secondary dissolution as core qualitycontrol factors. Different genetic types exhibit distinct development patterns, guiding exploration target optimization. Complementing this, Wang et al. proposed an automatic fracture detection method for igneous rocks using K-means and DNN on imaging logs, improving characterization accuracy.Chen et al. focused on the Xixiangchi Formation in the central-southern Sichuan Basin, exploring how structure, deposition, and differential diagenesis synergistically affect reservoir quality. Tectonics control facies distribution, deposition provides material basis, and diagenesis reshapes pores-this framework enables comprehensive quality evaluation under complex tectono-sedimentary backgrounds.As highlighted in the call for papers, the accumulation and preservation conditions of unconventional oil and gas in complex structural environments are critical research priorities, and organic matter enrichment, as the material basis for hydrocarbon generation, is closely linked to sedimentary environments and geological settings (Delle Piane et al., 2018;Zhao et al., 2023).Yao et al. used the NT1H Well in the Central Sichuan Basin to study Permian Longtan Formation organic enrichment, identifying anoxic deep-water shelves, high paleoproductivity, and low sedimentation rates as key preservation factors. This clarifies high-quality source rock formation conditions in complex areas, supporting generation potential evaluation.Wang et al. analyzed the Taiyuan Basin's karst geothermal system, revealing coupling between karst development, fault activity, and geothermal fluid migration. Faults control cave formation and act as fluid channels, creating favorable hydrocarbon generation and preservation conditionsresponding to the call for papers' focus on accumulation and preservation mechanisms in complex structures. This expands understanding of coexisting geothermal and oil-gas resources in intermountain basins, aiding integrated exploration.Jin studied hydrocarbon charging in Ediacaran Dengying Formation deep fractured-vuggy dolomites in the Southern Sichuan Basin. Reconstructing charging history, they identified two phases: early oil and late gas charging. Late charging, driven by deep hydrothermal activity and tectonic uplift, is key to high-yield reservoirs-deepening understanding of deep dolomite accumulation mechanisms in complex structural environments.To address the exploration challenges posed by complex geological conditions emphasized in the call for papers, innovative advanced detection and prediction technologies have become a key focus of this research topic-providing technical support for deciphering accumulation mechanisms in complicated structure areas.Zhang et al. proposed a GAN-based fracture prediction method integrating seismic attributes (e.g., coherence, curvature) and logging data. This improves detection accuracy in noisy complex areas, providing a vital tool for identifying fracture networks critical to tight reservoir migration and accumulation.Chen et al. developed a geological information-driven deep learning model for log-based lithology identification. Integrating prior knowledge (e.g., stratigraphy, sedimentary facies) reduces data ambiguity in complex formations, achieving high accuracy for tight sandstones and shales-laying the groundwork for intelligent reservoir characterization.Responding to the call for papers' focus on hydrocarbon accumulation mechanisms and preservation conditions in complex structures, studies in this section explore hydrocarbon migration processes and reservoir protection strategies-complementing the full-chain research on unconventional oil and gas accumulation.Hydrocarbon migration timing and pathways directly impact accumulation efficiency (Curtis et al., 2012;Zou et al., 2023). Wen and Wang established a quantitative model for oil-source fault effective charging periods, based on fault activity, mudstone smearing, and generation timing. They identified effective charging windows and confirmed that high-seal faults favor high-yield reservoirsclarifying fault regulation of migration and aiding favorable zone identification in complex areas.Reservoir protection is critical for development efficiency. Tang et al. investigated microscopic mechanisms of formation damage from oil-bearing wastewater reinjection. Experimental analysis revealed how oil droplets, solids, and chemicals block pores, identifying permeability reduction causes. This provides a theoretical basis for targeted protection measures and wastewater process optimization, filling gaps in unconventional reservoir damage research and supporting sustainable development of resources in complex areas.Collectively, these 15 studies cover multiple scales (micro-pore-throat to basin-scale tectonics), resource types (tight sandstone, shale gas, deep dolomite, igneous rock), and the full development chain (accumulation, detection, protection), forming a systematic understanding of unconventional accumulation in complex areas. They deepen theoretical insights and offer practical supportadvanced detection boosts drilling success, control factor identification optimizes "sweet spots," and protection research ensures sustainability. Amid global energy transition, these findings are significant. They confirm substantial exploration potential in complex areas, expanding energy supply paths. Additionally, multi-disciplinary integration (geology, geophysics, AI, environmental engineering) drives intelligent, green oil-gas development, serving as a global reference for complex geological challenges. Despite progress, challenges remain: multi-scale geological process coupling (tectonism, diagenesis, generation) needs clarification, and long-term reservoir dynamic evolution and development impacts require deeper study. Future research should integrate multi-dimensional data, develop coupled numerical models for accurate accumulation prediction, and build full-life-cycle protection systems.
Wang et al. (Wed,) studied this question.