Abstract: Huanghua depression in the Bohai Bay Basin has gone through three stages of structural-lithological reservoir exploration, lithological reservoir exploration in slope zones, and lithological reservoir exploration in deep subsag zones. The cumulative proven petroleum geological reserves in Huanghua depression exceed 1.3×10⁸t, and more than 50 % of conventional petroleum reserves have been proved, indicating that the whole Huanghua depression has entered a highly mature exploration stage. By contrast, there are tight oil and gas of low exploration degree and large remaining oil and gas resources in Bohai Bay Basin, which is an important exploration field for Dagang oilfield to increase reserves and production in the future. Based on the data of drilling, geophysical survey, and experimental test in recent years, the paper systematically analyzes the favorable hydrocarbon accumulation conditions, accumulation periods, accumulation model, and resource potential of tight oil and gas in Huanghua depression. The research results show as follows. (1)Huanghua depression possesses favorable conditions for the accumulation of tight oil and gas. The fault activity and thermal subsidence that have a controlling effect on the basin and depressions have led to the formation of vast reservoir spaces in deep layers of the basin, providing a favorable tectonic setting for the input of sedimentary provenance. During the depositional periods of the Kongdian Formation, Shahejie Formation, and Dongying Formation, sand bodies were widely distributed. The four main source rock formations, i.e., Member 2 of Kongdian Formation (E₂k₂), Member 3 of Shahejie Formation (E₃s₃), Member 1 of Shahejie Formation (E₃s₁), and Member 3 of Dongying Formation (E₃d₃), are widely distributed in Huangye depression, and have high hydrocarbon generation intensity and superior hydrocarbon supply conditions, which can provide an important resource foundation for the enrichment of tight oil and gas. Strong dissolution leads to the development of dissolution pores in tight oil and gas reservoirs, thus improving the reservoir conditions. There are three types of source-reservoir assemblage patterns, i.e., lower generation and upper accumulation pattern, three-dimensional filling pattern, and lateral hydrocarbon migration and accumulation pattern, demontrating excellent conditions for configuration of source rocks and reservoirs. (2)There are two main accumulation periods of tight oil and gas in Huanghua depression, i.e., sedimentary period from Shahejie Formation to Dongying Formation and sedimentary period from Minghuazhen Formation to the present. The tight oil and gas reservoirs in Huanghua depression are mainly developed in the deep subsag zone and the lower step fault zone around the sag, with the characteristics of "source-reservoir coupling and continuous accumulation". (3)Huanghua depression is rich in tight oil and gas resources, including the tight oil resources of 2.82×10⁸t, 1.17× 10⁸t and 5.92×10⁸t in E₂k₂ of Cangdong sag, Dongying Formation and Shahejie Formation of Qikou sag, respectively, and also the tight gas resources of 2 875×10⁸m³ in Shahejie Formation of Qikou sag. Based on the comprehensive evaluation and analysis of petroleum geological conditions, remaining oil and gas volume, and exploration practice of different layers of petroleum systems in each area, it is determined that the E₂k₂ of Cangdong deep subsag zone, E₂k₂ of Changzhuang subsag, and Dongying Formation of Qikou deep subsag zone are favorable new areas for exploration of tight oil, and the E₃s₃ of Banqiao subsag and southwestern edge of Qikou sag are favorable new areas for exploration of tight gas. The new understandings of geology and resource potential resulted from the breakthrough in tight oil and gas exploration can provide technological support for the subsequent sustained and highly efficient exploration in Huanghua depression.

Key words: Bohai Bay Basin, Huanghua depression, tight oil and gas, resource potential, accumulation condition, accumulation period

摘要： 渤海湾盆地黄骅坳陷经历了构造-岩性油气藏勘探、斜坡区岩性油气藏勘探、深凹区岩性油气藏勘探3个阶段,累计探明石油地质储量超过13×10⁸t,常规石油探明程度超过50 % ,总体进入了高成熟勘探阶段。相对来说,渤海湾盆地的致密油气勘探程度低,剩余油气资源量大,是未来增储上产的重要勘探领域。基于钻井、地球物理和分析测试等资料,对黄骅坳陷致密油气的有利成藏条件、成藏期、成藏模式和资源潜力进行了系统分析。研究结果表明:①黄骅坳陷具备致密油气成藏的有利条件。控盆控凹断裂活动与热沉降作用导致湖盆形成广阔的可容空间,为物源输入提供了有利场所,其中,孔店组、沙河街组和东营组中沉积砂体发育且分布广;黄骅坳陷广泛分布孔店组二段、沙河街组三段、沙河街组一段和东营组三段4套主力烃源岩,烃源岩生烃强度大,供烃条件优越,为致密油气的富集提供了重要资源基础;储层溶蚀作用强,溶蚀孔隙的发育使得储集条件得以改善;发育下生上储型、立体充注型和旁生侧储型3类源-储组合,源-储配置条件优越。②黄骅坳陷致密油气存在2个主要成藏期,分别在沙河街组—东营组沉积期和明化镇组沉积期至今。黄骅坳陷致密油气主要发育于深凹区以及环凹低断阶带内,具有"源-储耦合、连片成藏"的特点。③黄骅坳陷致密油气资源量丰富,其中,沧东凹陷孔店组二段致密油资源量为2.82×10⁸t,歧口凹陷东营组致密油资源量为1.17×10⁸t,而沙河街组致密油资源量为5.92×10⁸t、致密气资源量为2 875×10⁸m³。根据各地区不同层系油气系统的石油地质条件、剩余油气量、勘探实践等综合评价结果,优选出沧东深凹孔店组二段、常庄次凹孔店组二段、歧口深凹东营组为致密油有利勘探新领域,板桥次凹沙河街组三段和歧口凹陷西南缘沙河街组三段为致密气有利勘探新领域。致密油气勘探突破带来的地质和资源潜力的新认识可为黄骅坳陷后续持续高效勘探提供技术支撑。

关键词: 渤海湾盆地, 黄骅坳陷, 致密油气, 资源潜力, 成藏条件, 成藏期次