冀中坳陷碳酸盐岩深层古潜山油气成藏有利条件

近年来的勘探实践表明，渤海湾盆地冀中坳陷深层碳酸盐岩古潜山具有广阔的油气勘探前景。为系统总结该区深层古潜山（深度大于4 000 m）的油气富集规律，利用多种地震属性参数分析成果并结合区域地层对比认识，准确解析了深层古潜山的构造形态，确定了古潜山层位；在此基础上，根据测井、野外勘察和岩心分析等资料，研究了该区深层古潜山的油源、储集空间、盖层、油气输导等油气成藏的有利条件，总结了深层古潜山油气的成藏模式。结果表明：①深层古潜山多数在渐新世以后进入稳定深埋期，古潜山圈闭的形成时间早，相应的烃源岩埋藏深度大、有机质丰度高、生烃窗口跨度大、生排烃期长、热演化程度高，为古潜山成藏提供了油气源保障；②碳酸盐岩储集空间主要为孔、洞、缝组成的网络体系，埋藏深度对其物性影响较小；③2套上覆区域性盖层与5套古潜山内部直接盖层，为深层古潜山油气成藏提供了良好的封盖条件；④在断层、不整合面近源输导下，深层古潜山各类油气成藏要素在时间和空间上具有很好的配置关系，形成以长6井、宁古1井等为典型代表的“新生古储”古潜山成藏模式。

Favorable hydrocarbon accumulation conditions for carbonate reservoirs in deep buried hills in the Jizhong Depression,Bohai Bay Basin

Exploration in recent years reveals that huge potential exists in the carbonate reservoirs in deep buried hills in the Jizhong Depression, Bohai Bay Basin. This paper systematically summarized the hydrocarbon accumulation patterns in the deep buried hills, the burial depth of which is over 4000 m, in this study area. First, various seismic attribute parameters were integrated with stratigraphic correlation to accurately define the structural shapes and horizons of the deep buried hills. Then, logging, outcrop observation and core data were used to study the conditions favorable for hydrocarbon accumulation such as oil source, reservoir space, cap rocks and carrier beds, and summarized the patterns of hydrocarbon accumulation in the deep buried hills. The following conclusions were obtained. (1) The deep buried hills mostly entered the stable deep burial period since the Oligocene. The palaeo buried hill traps were formed early, thus the source rocks were correspondingly great in burial depth, high in organic abundance, wide in oil/gas window, time consuming in hydrocarbon generation and expulsion, and high in thermal maturity, thus providing sufficient oil/gas source for the buried hill pools. (2) The reservoir space of carbonates was dominated by a network system consisting of pores, vugs and fractures, thus its burial depth had little impact on reservoir poroperm characteristics. (3) Two overlying regional seals and 5 local seals within the buried hills provided supreme sealing conditions for the hydrocarbon accumulation and preservation in the buried hills. (4) The near source carrier system such as fault and unconformity led to the favorable temporal and spatial assemblage of reservoir, source and cap rocks, resulting in a typical buried hill reservoir of “new source rock and old reservoir” represented by the wells like Chang 6 and Ninggu 1.