海拉尔盆地乌尔逊-贝尔凹陷大磨拐河组油气成藏条件

Petroleum accumulation conditions of Damoguaihe Formation in Urxun—Beier Sags,Hailaer Basin

运用地层学、构造地质以及成藏系统等理论和方法,系统阐述乌尔逊—贝尔凹陷大磨拐河组油气成藏条件。凹陷断裂经历了铜钵庙组—大磨拐河组沉积期的伸展变形、伊敏组沉积期的走滑变形和青元岗组沉积期—古近纪末期的强烈反转变形3个阶段。大磨拐河组地层划分为3个三级层序和15个砂岩组,各个时期控制着不同沉积演化过程。大磨拐河组原油来源于南屯组,与南一段关系密切,存在2种油气运移方式:1)当断距大于300m时,南屯组生油源岩与大磨拐河组储层对接,从而构成直接侧向运移的旁生侧储型油藏;2)油沿(不整合面)油源断层自南屯组向上垂向运移至大磨拐河组,再短距离侧向运移形成下生上储型油藏,总结油藏类型为构造、岩性、地层及岩性—构造4大类。

The petroleum accumulation conditions of Damoguaihe Formation in the Urxun—Beier Sags of the Hailaer Basin were studied with stratigraphic,tectonic and accumulation system theories.The fractures in the study area experienced 3 stages of deformation including the extension during Tongbomiao and Damoguaihe periods,the strike-slip during Yimin period and the strong inversion during Qingyuangang and the late Paleogene periods.Damoguaihe Formation was divided into 3 third-grade sequences and 15 sand layers.Different stages controlled different sedimentary evolution processes.The crude oil in Damoguaihe Formation came from Nantun Formation and was closely related to the first member of Nantun Formation.There existed 2 ways of hydrocarbon migration.1） When the fault displacement was over 300 m,the source rocks in Nantun Formation connected with the reservoirs in Damoguaihe Formation,resulting in side-generating and side-reserving reservoirs.2） The hydrocarbon in Nantun Formation migrated upwards into Damoguaihe Formation,and then moved laterally for a short distance,forming lower-generating and upper-reserving reservoirs.The reservoirs in the region were classified into 4 types： tectonic,lithologic,stratigraphic and lithologic—tectonic.