Abstract: The ultra-deep oil and gas resources are abundant in China’s superimposed basins, which are an important strategic replacement field. The exploration and research work has revealed that there is a dichotomy of accumulation conditions for ultra-deep oil and gas reservoirs; favorable accumulation conditions only exist in specific basin environments, characterized with regionality, while the unfavorable accumulation conditions are inherent attributes of ultra-deep layers, characterized with universality. The decisive factors determining whether ultra-deep layers have exploration value are the effectiveness and scale of source kitchens, the effective reservoir and its scale, as well as the spatial combination and effectiveness of source, reservoir, and cap. The basins with exploration potential in ultra-deep layers have the following characteristics: (1) there is differential subsidence evolution in cratons, which have not been deeply buried during a long geological history, and where source kitchens are developed and still in an effective hydrocarbon-generation window to this day; (2) sedimentary strata mainly composed of carbonate rocks are developed, with granular platform marginal-platform shoals and intraplatform shoals, and have undergone constructive diagenesis and modification, or have experienced groundwater dissolution and leaching during geological history, as result of which reservoirs with pores in ultra-deep layers (including fractures and caves) are developed and have been effective till today; (3) the development of clastic rock, basement, or volcanic reservoirs requires a combination of single or multiple factors, such as long-term shallow burial and later deep burial with a short burial time, the presence of structural bridges for supporting effect, less compaction, the generation of fractures by tectonism, or long-term weathering for constructive reformation of crystalline rocks; (4) the basin generally presents a medium to low geothermal field, or there is no excessive radioactive material in the environment during the development of source rock, and the large-scale hydrocarbon generation is not accelerated. The reasons for the occurrence of unfavorable accumulation conditions in ultra-deep layers include: (1) mechanical compaction and high temperature and pressure result in strong diagenesis and increased plasticity of rock particles in ultra-deep layers, which is not favorable to the preservation of reservoir pore space; (2) most source rocks in ultra-deep layers have lost their hydrocarbon-generation potential, and the effectiveness of source kitchens is limited due to deep burial and long burial history; (3) there is a low probability for forming an effective combination of source-reservoir-seal-trap, and the probability of economic resource mineralization is reduced. China has abundant oil and gas resources and great exploration potential in ultra-deep layers, but large-scale exploration faces challenges in terms of the hydrocarbon accumulation theory to be perfected and engineering technology, and it is urgent to carry out researches to achieve relevant breakthroughs.

Key words: ultra-deep layers, dichotomy of accumulation conditions, source kitchen, reservoir, source-reservoir-seal combination, effectiveness, exploration position, onshore China

摘要： 中国叠合盆地超深层油气资源丰富,是重要的战略接替领域。勘探研究与实践揭示,超深层油气成藏条件具有两分性:有利成藏条件只存在于特定的盆地环境,具有地域性;不利成藏条件是超深层固有属性,具有普遍性。烃源灶有效且有规模、储集层至今保持有效储集性能且有规模、生-储-盖要素存在空间组合且至今保持有效性是超深层是否具有勘探价值的决定性要素。有利于超深层具备勘探潜力的盆地具有以下特征:①存在克拉通差异沉降演化,且在漫长地质历史时期未被深埋,烃源灶发育且至今仍在有效生烃窗口;②发育碳酸盐岩为主的沉积层系,存在颗粒型台缘和台内滩并经过建设性成岩作用改造,或者在地质历史时期曾经历地下 水溶蚀淋滤,使超深层孔隙(含裂缝、溶洞)发育的储层至今依然有效;③碎屑岩、基岩或火山岩储层发育需要满足长期浅埋+ 后期深埋且深埋时间不长、存在构造桥的托举作用、较少压实作用影响、构造作用产生裂缝或长期风化作用建设性改造结晶岩类等单一要素或多种要素组合作用;④盆地总体呈中—低地温场,或烃源岩发育阶段环境中无过量放射性物质存在,规模生烃过程不被速化。不利于超深层成藏的原因有:①机械压实和高温高压导致超深层成岩作用强、岩石颗粒塑性增加,不利于储层孔隙空间的保存;②超深层因埋藏深、埋藏历史长,多数烃源岩已经失去生烃能力,烃源灶有效性受限;③形成生-储-盖-圈有效组合的机会偏少,且有经济性的资源成矿几率降低。中国超深层油气资源丰富,勘探潜力大,但规模勘探面临着成藏理论有待完善、工程技术有待提高等挑战,亟待开展攻关研究。

关键词: 超深层, 成藏条件两分性, 烃源灶, 储集层, 生-储-盖组合, 有效性, 勘探地位, 中国陆上