松辽盆地安达古隆起风化壳特征及控藏机制

Characteristics of the weathered crust and reservoir-controlling mechanism for Anda Palaeohigh in Songliao Basin

为了探索松辽盆地安达古隆起风化壳特征及控藏机制,利用钻井、测井、地震、岩心及实验分析资料,从风化壳的岩性、结构、规模方面对安达古隆起风化壳的地质特征及控藏机制进行了深入分析。研究结果表明安达古隆起是由片岩、千枚岩、变质砾岩及糜棱岩组成的古生代基岩隆起,构造幅度超过3 500 m,从晚侏罗世到早白垩世经历了约20 Ma风化剥蚀,形成了大规模的基岩隆起型变质岩风化壳,最大厚度为80～90 m,主体面积约为200 km2。风化壳具有典型的三元结构,即风化堆积层、半风化层及未风化基岩层,其中半风化层分为裂缝充填层、裂缝氧化层和原生裂缝层。风化壳被后期盆地坳陷地层覆盖且保存完整,形成良好的封盖条件,周边断陷期烃源岩生成的油气沿着隆起上超通道运移到风化壳内部聚集,形成了新生古储型气藏,半风化层储集性能及风化堆积层的封盖能力成为风化壳圈闭成藏的主控因素。研究成果对于松辽盆地中央古隆起带及其他古隆起勘探具有重要的指导意义。

In order to explore the characteristics of the weathered crust in Anda Palaeohigh of Songliao Basin, with the help of the drilling, well Logging, seismic, core and experimental analyzed data, from the viewpoints of the lithology, structure, scale, the geological characteristics and reservoir-controlling mechanism of the crust were deeply figured out. The study results show that Anda Palaeohigh is Paleozoic bedrock uplift which is made up of schist, phyllite, metamorphic conglomerate and mylonite, which structural amplitude is more than 3 500 m and experienced weathering and erosion about 20 Ma during Late Jurassic and Early Cretaceous, a large scale weathered crust of the bedrock uplifted-metamorphic rocks was formed, its maximal thickness is 80-90 m and the main body area is about 200 km^2. The weathered crust has typical three-composition structures: weathered accumulative formation, partly weathered layer and unweathered bedrock. The partly weathered layer can be divided into fracture-filled layer, fracture oxidation layer and primary fracture layer. The weathered crust is covered by the depression layer in the later formed basin and preserved integrally, thus much better sealed and trapped conditions were developed, the oil and gas generated by the surrounding fault-period source rocks were migrated along the uplift upward passage into the weathered crust and accumulated a new paleo-source-rock gas reservoir, the accumulating performances of the partly weathered crust and the sealing ability of the weathered accumulation layer are the main controlling factors for the hydrocarbon accumulation of the weathered crust traps. The study results possess important guiding significance for the explorations of the Central Paleo-uplift Belt and other paleo-uplifts in Songliao Basin.