塔南凹陷古地貌特征对沉积体系和油气分布的影响

为研究海拉尔—塔木察格盆地塔南凹陷铜钵庙组和南屯组的油气分布,应用三维地震和钻井资料,通过盆地构造建模恢复古地貌特征,明确不同地质历史时期古地貌对沉积体系及油气分布的控制作用。结果表明:①铜钵庙组沉积期,塔南凹陷具有“泛洼槽多物源”的特征,物源主要来自NW—SE向扇三角洲和WS向凹陷古隆起。南屯组沉积期全区发育4个规模较大的沉降中心,从西次凹逐渐向凹陷中心发生迁移。②铜钵庙组主要发育冲积扇、扇三角洲和滨浅湖沉积,凹陷内部古隆起控制了冲积扇的形成与分布。南屯组主要发育三角洲、扇三角洲、近岸水下扇、湖底扇和湖相沉积,古隆起、古坳陷分别控制了近岸水下扇的形成与烃源岩的展布范围。③塔南凹陷古地貌对油气分布的控制作用表现为“古隆-坡控储、古坳陷控源、古断-坡控藏”。西部为“源-储对接”、“古断-坡”组合控运聚的构造油藏,东部为陡坡控制下以近岸水下扇和湖底扇为储集体的岩性油藏,古地貌演化特征和“古断-坡”组合对源、储空间配置及油气运聚起决定性作用。该成果对认识塔南凹陷油气分布规律具有重要的指导意义。

Influence of paleogeomorphic characteristics on sedimentary system and hydrocarbon distribution in Tanan Depression

In order to research the hydrocarbon distribution of Tongbomiao Formation and Nantun Formation in Tanan Depression of Hailar-Tamuchage Basin,three-dimensional seismic,logging and mud logging data were used to restore the paleogeomorphology through basin structural modeling,so as to clarify the control effect of paleogeomorphology on sedimentary system and hydrocarbon distribution in different geological periods. The results show that:(1)The sedimentary period of the Tongbomiao Formation has the characteristics of "extensive troughs and multi-sources sediment",and the source is mainly the fan delta in NW-SE and paleo uplift in WS. During the sedimentary period of Nantun Formation,there were four large-scale subsidence centers developed in the whole area,and the subsidence center gradually migrated from the west sub-depression to the depression center. (2)Alluvial fan,fan delta and coastal shallow-lake facies were mainly developed in Tongbomiao Formation, and the formation and distribution of alluvial fan were controlled by the paleo uplift in the depression. Delta,fan delta,nearshore subaqueous fan,sublacustrine fan and lacustrine were mainly developed in Nantun Formation, and paleo-uplift and paleo-depression controlled the formation of nearshore underwater fan and the distribution of hydrocarbon source rocks respectively.(3)The paleogeomorphology of Tanan Depression controlled the distribution of oil and gas in the form of "paleo-uplift and slope controlled reservoir,paleo-depression controlled source,paleofault and slope controlled accumulation". In the west,there were structural reservoirs controlled by "source-reservoir connection" and "paleo-fault and slope" combination,while in the east,there were lithologic reservoirs controlled by steep slope with nearshore subaqueous fan and sublacustrine fan as reservoirs. Paleogeomorphic evolution as a decisive role in the distribution of source and reservoir,and the "paleo-fault and slope" combination as a decisive role in the transportation and accumulation of hydrocarbon. The research results have important guiding significance for understanding the law of hydrocarbon distribution in Tanan Depression.