断裂密集带油气差异富集主控因素探讨——以歧口凹陷歧南断阶带为例

为研究歧南断阶带油气成藏规律，以三维地震、钻井、测井、岩心等资料为基础，利用断裂密集带划分，累计隆起幅度和盖层断接厚度计算等研究方法，分析了渤海湾盆地歧南断阶带中浅层油气平面和垂向差异富集规律，并建立了油气成藏模式。结果表明，①歧南断阶带内以似花状断裂密集带为主，走向北东向和北东东向，其中以发育背形断裂密集带为主；②平面上，油气主要富集区域位于断裂密集带内部及边部，内部油气富集程度较边部高，从断裂密集带类型分析，油气主要富集于背形断裂密集带，背形断裂密集带内累计隆起幅度控制着油气富集程度；③垂向上，东营组下段泥岩盖层断接厚度控制断裂密集带内中浅层的油气聚集；④背形断裂密集带内累计隆起幅度较大且东营组下段泥岩盖层断接厚度小于50 m的区域，油气可穿越东营组下段泥岩盖层在中浅层富集。该项成果可为研究区下一步的勘探评价提供参考。

Main controlling factors of differential enrichment of oil and gas in fault concentrated zones: a case study from Qinan step-fault zone in Qikou Sag

In order to study the oil and gas accumulation law of Qinan step-fault zone,based on 3D seismic,drilling,logging and core data,through the division of fault concentrated zones and the calculation of cumulative uplift amplitude and the thickness of cap rock juxtaposition,the horizontal and vertical differential enrichment law of shallow oil and gas in Qinan step-fault zone of Bohai Bay Basin was analyzed,and the oil and gas accumulation model was established. The results show that:(1)Flower-like faults,mostly antiformal faults,are well developed and densely distributed in NE and NNE-trending belts of Qinan step-fault zone.(2)Horizontally,oil and gas mainly enrich in the inner and marginal parts of the fault concentrated zones,with enrichment degree being higher in the inner part than that in the marginal part. According to the types of fault concentrated zones,oil and gas are mainly concentrated in the antiformal fault concentrated zones,and the cumulative uplift amplitude in the antiformal fault concentrated zones controls the degree of oil and gas enrichment.(3)Vertically,cap rock juxtaposition thickness of E₃d₂ controls the oil and gas accumulation in middle and shallow layers of the fault concentrated zones.(4)In the antiformal fault concentrated zones with larger cumulative uplift amplitude and cap rock juxtaposition thickness of E₃d₂ being less than 50 m,oil and gas can pass through the cap rock of E₃d₂ and accumulate in the middle and shallow layers. The achievement can provide reference for further exploration and evaluation in the study area.