北非古生界含油气盆地油气成藏组合特征

Characteristics of Hydrocarbon Reservoir-Cap Assemblages in Paleozoic Hydrocarbon Basins in North Africa

通过对北非地区典型含油气盆地的烃源岩分布、储层特征、盖层特征、圈闭类型等进行综合性讨论分析,总结了成藏组合的基本特征。研究认为,北非地区成藏组合烃源岩较为单一,主要为下志留统和中—上泥盆统的"热"页岩,分布面积广、生烃潜力巨大;各含油气盆地古生界所有砂岩均为储层,主要为奥陶系和泥盆系储层,具有层位多、品质好的特点,而古达米斯盆地存在大面积分布的三叠系储层;主要盖层为下志留统、上泥盆统页岩,次要盖层为石炭系、下泥盆统页岩和碳酸盐岩;主要发育构造圈闭、地层圈闭及构造—地层复合圈闭,不同类型的圈闭形成不同的油气藏;研究区域内油气运移方式主要有3种,以横向长距离或短距离运移为主。综合分析北非地区古生界含油气盆地主要成藏组合特征后认为,古达米斯盆地剩余油气储量最为丰富,并且生储盖匹配良好,圈闭类型多样,保存条件优越,勘探开发程度较低,是北非地区古生界含油气盆地中勘探潜力最大的盆地。

Based on a comprehensive analysis of source rock distribution, reservoir characteristics, cap rock characteristics and trap types in typical hydrocarbon basins in North Africa, this paper summarizes the basic characteristics of reservoir-cap assemblages in the region. The study indicates that source rock of reservoir-cap assemblages in North Africa is fairly homogenerous, mainly the Lower Silurian and Middle-Upper Devonian ＂hot＂ shale, distributed in large areas with huge sourcing potential. All Paleozoic sandstone is reservoir in various hydrocarbon basins. It is mainly the reservoir of Ordovician System and Devonian System. However, the reservoirs in different regions have different characteristics. Triassic reservoirs are distributed in large areas in Ghadames Basin. The main cap rock is Lower Silurian and Upper Devonian shale while the secondary cap rock is Carboniferous and Lower Devonian shale and carbonate rock, with development of structural traps, stratigraphic traps and structttral-stratigraphic compound traps. Different traps shaped different oil and gas reservoirs. There are three main patterns for oil and gas migration in the study zone, mainly the horizontally long-distance or short distance migration. Following analysis of the characteristics of reservoir-cap assemblages in Paleozoic hydrocarbon basins in North Africa, it is assumed that Ghadames Basin is richest in remaining oil and gas reserves and matched with desirable reservoir-cap assemblages. Thanks to a variety of traps, advantageous reservoir conditions and a low level of exploration and development, Ghadames Basin has the greatest potential for exploration in Paleozoic hydrocarbon basins in North Africa.