乌尔逊凹陷大磨拐河组油气成藏机制

Hydrocarbon accumulation mechanism of Damoguaihe Formation in Wuerxun Depression

乌尔逊凹陷大磨拐河组油气藏的分布和油气成因机制在凹陷南部和北部表现出差异性,乌南油藏主要分布在大二段上部,乌北油藏分布在大一段底部,乌南大磨拐河组油藏与南屯组油藏具有消长关系。以探索乌南、乌北大磨拐河组油气成藏机制为目的,在研究乌尔逊凹陷晚期构造演化的基础上,结合大磨拐河组GOI指标、成藏时期及原油成熟度变化等分析认为,晚期构造变形控制着乌尔逊凹陷大磨拐河组的油气运移与聚集,乌北大磨拐河组油藏形成于伊敏组末期的张扭变形,乌南大磨拐河组油藏则为南屯组原生油藏在青元岗组沉积末期反转变形中遭受破坏而形成的次生油藏,同时晚期构造变形过程中所形成的断块、断鼻、断背斜、背斜等多种构造圈闭为大磨拐河组油藏提供了聚集条件。

The oil accumulations in Damoguaihe Formation of Wuerxun Depression, Hailaer Basin show great difference in distribution and genetic mechanism between southern and northern Wuerxun Depression. The oil is accumulated at the top of Upper Damoguaihe Formation in southern Wuerxun Depression, where the oil accumulations show a decreasing-and-increasing relationship between Nantun Formation and Damoguaihe Formation, and at the bottom of Lower Damoguaihe Formation in northern Wuerxun Depression. To investigate the mechanism of hydrocarbon accumulation in southern and northern Damoguaihe Formation, based on the study of late tectonic evolution in Wuerxun Depression and combined with GOI characteristics, oil accumulation time and crude oil maturity change, it is believed that the late tectonic deformation controls the oil migration and accumulation in Damoguaihe Formation in Wuerxun Depression. The oil accumulations in Damoguaihe Formation of northern Wuerxun Depression are formed by the transtension deformation at the end of Yimin Formation deposition. In southern Wuerxun Depression, the oil accumulations of Damoguaihe Formation are the secondary oil accumulations that are formed after the original oil accumulations of Nantun Formation were destroyed during the tectonic deformation at the end of Qingyuangang Formation deposition. The diversified structural trap types, such as fault block, fault nose, fault anticline and anticline which were formed during the same late tectonic deformation, provided good trap conditions for the oil accumulation in Damoguaihe Formation.