徐家围子断陷深层气藏类型及成藏模式

Types and pooling patterns of deep gas reservoirs in Xujiaweizi fault depression

松辽盆地北部徐家围子断陷隐蔽型天然气藏形成机制和分布规律复杂,制约了勘探开发工作的进展。为此,依据天然气藏的成因,从勘探开发实用性出发,研究了该区深层气藏类型和成藏模式。结果认为:徐家围子断陷深层主要发育有构造—岩性、岩性—构造、岩性、构造—地层、基岩风化壳等5种气藏类型和上生下储式、自生自储式、下生上储式、幔生上储式等4种成藏模式。另外,根据甲烷碳同位素值、乙烷碳同位素值和干燥系数3方面的天然气成因类型划分结果,认为下白垩统营城组天然气主要分布在煤成气区域,主要来源于下白垩统沙河子组的湖相泥岩和煤层。

The subtle gas reservoirs in Xujiaweizi fault depression of the Songliao Basin are characterized by complex genetic mechanisms and distribution patterns,challenging gas exploration and development.For this reason,we analyzed the types and pooling patterns of the deep gas reservoirs in this fault depression on the basis of the genesis study of gas reservoirs.There are five types of gas reservoirs in the deep fault depression,including structural-lithologic,lithologic-structural,lithologic,structural-stratigraphic and weathered crust of the basement,and four types of pooling patterns,including ①generation form the upper source rocks and accumulation in the lower reservoirs,②indigenous generation and accumulation,③generation from the lower source rocks and accumulation in the upper reservoirs,and ④generation from the mantle and accumulation in the upper reservoirs.According to the analyses of genetic types of gas in aspects of methane carbon isotope,ethane carbon isotope and drying coefficient(C1/C2+C3),it is believed that the gas in the Lower Cretaceous Yingcheng Formation is mainly of coal-derived gas sourced from the lacustrine mudstone and coal layers in the Lower Cretaceous Shahezi Formation.