残余盆地构造分析与油气地质评价

垂向上层序不完整,平面上沉积体系和相带不齐全,盆地以侵蚀或断层为边界以及周缘和邻近地区露头的构造特征都可作为识别残余盆地的标志。残余盆地大多经过多次构造的叠加,从系统论和信息论的角度可将这一过程抽象为建造过程、构造过程和信息记录过程。要认识和重建某个地质历史时期盆地的原始构造格局和沉积特征,就必须除去后期叠加的构造层和构造变形,即反序构造分析法。该方法主要包括构造成像、变形年代确定和变形恢复等几项关键技术。残余盆地油气地质条件复杂,一般分两个步骤对其进行油气地质评价 :一是运用反演技术恢复原型盆地构造格局、沉积特征以及原生油气地质特征;二是以原型盆地为出发点,运用正演技术对其进行理论分析,将结果与现存实际对照,修正主观因素的影响。以此为基础,建立盆地改造过程中空间结构层次、时间发生序次与成烃、成藏事件的时空耦合关系,并由此深化对油气形成和聚集规律的认识。

STRUCTURAL ANALYSIS AND PETROLEUM GEOLOGY ASSESSMENT OF RELICT BASINS

The structural characteristics such as vertically stratigraphical sequence hiatus,planar sedimentary system and facies incompleteness,delimitation of a basin by erosion or fault,and the structural feature of outcrop in peripheral and near arears could be taken as marks in recognizing relict basins.Most the relict basins underwent multi-tectonic superposition.According to the theory of system and information,the multi-tectonic superposition could be abstracted as the processes of construction,structure and the information record.Then use antitone structural analysis method to recognize and reconstruct the primary tectonic structure and sedimentary feature of a basin in certain geological history.The method includes mainly several key technologies such as tectonic imaging,the determination of deformation age and deformation reversion.Usually one should adopt two steps to assess the petroleum geological conditions in relict basins:(1)use inversion technology to reconstruct the structural framework of the prototype basin,the deposition feature and the primary oil and gas geological feature of the prototype basin;(2)use forward solution to theoretically analyze the prototype basin,then compare the analysis results with actural basin,and correct the effect of subjective factors.On this basis,the space structural hierarchy,the time order and time-space coupling relationship of hydrocarbon generation,pool-forming events could be found,and then oil and gas generation and accumulation regularity could be further understood.