准南前陆冲断带油气成藏的主控因素

MAIN CONTROL FACTORS OF HYDROCARBON RESERVOIRING IN FORELAND THRUST BELT IN SOUTHERN JUNGGAR BASIN

准噶尔盆地南缘前陆冲断带油气资源丰富,但探明率很低,亟待开展油气成藏的主控因素分析。为此,在对该冲断带油气成藏地质条件及成藏过程综合研究的基础上,通过系统分析油气成藏要素对油气成藏的控制及目前勘探中油气分布的特征,得出控制准南前陆冲断带油气成藏的主要因素如下:①以中下侏罗统煤系和上二叠统泥岩为主的4套烃源岩的分布范围宏观上控制了油气藏的平面展布及含油、气性质;②具良好储集性能的滨浅湖和三角洲砂体控制了油气分布的层位及油气藏的规模;③早于主要排烃期而形成的圈闭,是油气聚集的最有效场所;④从更深层次上看,断裂是控制成藏的最根本因素,它通过控制圈闭的形成、纵向的沟通作用及对原生油气藏进行破坏形成次生油气藏而最终决定油气藏的分布。由此建议,在今后的油气勘探中应注重对烃源岩、储集层、圈闭和断裂的综合分析,尤其要突出对断裂发育特征的分析,以不断提高勘探成功率。

The foreland thrust belt in the southern Junggar Basin is rich in petroleum resources, but is low in the degree of exploration, thus an analysis of the main control factors of hydrocarbon reservoiring is in urgent need. Based on a comprehensive research of the geologic conditions and process of hydrocarbon reservoiring in the thrust belt, the control of various key elements on the reservoiring and distribution of hydrocarbons are systematically analyzed and the following main factors that control the reservoiring of hydrocarbons in the study area are proposed. ① The distribution range of 4 source rock intervals dominated by the Lower-Middle Jurassic coal measures and the Upper Permian shale control macroscopically the plane distribution of oil and gas reservoirs and the oil- and gas-bearing properties. ② The sandbodies of shore-shallow lake facies or delta facies with good poroperm characteristics control the horizons of hydrocarbon distribution and the scale of oil and gas reservoirs. ③ The traps formed before the main hydrocarbon expulsion phase are the most effective places for hydrocarbon accumulation. ④ Fault is the most fundamental factor that controls the reservoiring of hydrocarbons. It determines the final distribution of oil and gas reservoirs through controlling the formation and vertical communication of traps, damaging the original oil and gas reservoirs and causing the formation of secondary oil and gas reservoirs. It is proposed that much attention should be paid to the comprehensive analysis of source rocks, reservoir rocks, traps and faults, especially the features of fault development in future petroleum exploration, so as to increase the success rate of exploration.