苏北盆地复杂小断块油气成藏特征及地震识别技术

Hydrocarbon pooling features and seismic recognizing technologies of small complex fault blocks in Subei basin

苏北盆地由小型箕状凹陷组成,断层密度高、圈闭面积小、油气贫富不均是其复杂性的主要表现。苏北盆地的成藏特点是:1)成藏时间为始新世晚期;2)生油层单向排烃;3)始新世断陷和古新世坳陷两种沉积体系具不同运聚特点。断陷体系发育小型不连通砂体,油气以断裂为通道垂向运移成藏,分布于深凹并沿断裂纵向多层分布,以构造-岩性复合油气藏为主。坳陷体系发育大型三角洲砂体,油气自生自储、侧向运移活跃,在斜坡、隆起区储集,以构造油气藏为主,成排、成带富集;4)油气富集普遍受源岩成熟度、砂岩物性、断层封闭性等因素控制,上组合受油源通道等因素控制,中、下组合受疏导层、圈闭发育等因素控制。为适应复杂小断块油藏的勘探,发展并完善了一整套地震采集、处理、解释技术。

Subei basin is composed of small half grabens and features in closely-spaced faults, small traps, and homogeneous hydrocarbon abundance. Hydrocarbon pooling in Subei basin has the following characteristics： （ 1 ） The Late Eocene is the pooling period ; （2） Hydrocarbon expulsion of source rocks is unilateral ; （3） The migration and accumulation styles are different in the Eocene fault depression and the Palaeocene depression. The Eocene fault depression has small and isolated sandbodies, where hydrocarbons accumulate through vertical migration along the faults, the pools are distributed in the deep depression and occur vertically in multiple layers along the faults, and are dominated by structural-lithologic reservoirs. While the depression develops large delta sandbodies, hydrocarbon generation and accumulation occurring in the same layer and hydrocarbon migration is active. The pools mainly occur in the slope and uplift zones and are dominated by structural reservoirs. （4） Hydrocarbon enrichment is mainly controlled by of the faults. The upper source-reservoir-cap source rock maturity, physical properties of sandbodies and sealing rock combination is controlled by hydrocarbon migration, and the middle and lower combinations are controlled by the development of carrier beds and traps. To deal with the exploration of small complex fault block reservoirs, a set of technologies concerning seismic acquisition, processing, and interpretation, have been developed and improved.