断陷盆地油藏单元分析方法及勘探开发意义

断陷盆地具有典型复式油气聚集特征,同一构造单元上同层系油气藏多藏伴生、成因复杂、认识难度大。传统油藏研究通常以层系或油组为对象,多藏笼统分析,用构造模式认识油藏,造成岩性地层等复杂类型油气藏地质认识存在误区,制约了勘探发现。油藏单元分析方法在理论上突破了经典石油地质理论中圈闭概念的束缚,提出了油藏单元的新概念。以油藏单元为对象开展研究,精细解剖复式油藏,能够准确揭示不同类型油藏的成因机制和富集规律。冀中坳陷大王庄构造带的应用实例表明,油藏单元分析方法使油藏特征和成藏认识发生了重大变化,岩性油藏成因机制和主控因素研究取得了重要进展,"相构配置、满盆成藏"是岩性油藏基本的成因模式,岩性油藏在盆地内不同部位广泛分布。根据新的成藏认识指导大王庄构造带精细勘探获得重大突破,使一个勘探开发40余年的老油田重新焕发青春。这一研究成果不仅对准确认识复杂类型油气藏、丰富完善油气聚集理论具有重要意义,同时探索出了一种成熟探区岩性油藏勘探新思路。

An analysis method based on reservoir unit and its significance in exploration and development of rift basins

Rift basins are characterized with typical composite hydrocarbon accumulation. Multiple reservoirs are associated in the same series of strata in the same structural unit, and their geneses are complicated and difficult to clarify. In traditional researches of reservoir, series of strata or oil group is usually taken as the object for a general analysis on multiple reservoirs. Tectonic models are used to understand reservoirs, which leads to misunderstandings in analyzing composite reservoirs such as lithostratigraphic hydrocarbon reservoir, thus limiting the scope of exploration discovery. The analysis method based on reservoir unit theoretically breaks through the constraint from the concept of trap in the classic theory of petroleum geology, and proposes a new concept of reservoir unit. A study is performed on reservoir unit to meticulously analyze composite reservoirs, so as to accurately reveal the genesis mechanism and enrichment rules of different types of reservoirs. The application example in the Dawangzhuang structural belt shows that the understanding of reservoir characteristics and hydrocarbon accumulation have been significantly changed by the analysis method based on reservoir unit, and great progress has been made in studying the genesis mechanism and main controlling factors of lithologic reservoirs. It is pointed out that the basic genetic model of lithologic reservoirs is characterized with "sedimentary facies-structure configuration, whole-basin accumulation". Lithologic reservoirs are widely distributed in different parts of the basin. According to the new understanding of hydrocarbon accumulation, a major breakthrough has been achieved by fine exploration of the Dawangzhuang structural belt, which has rejuvenated an old oilfield that has been explored and developed for over 40 years. This research result is not only of great significance for accurately understanding composite oil and gas reservoirs and enriching and improving the theory of oil and gas accumulation, but also explores a new idea for exploring lithologic reservoirs in mature exploration areas.