鄂尔多斯盆地曙光地区延长组低丰度油藏成藏机理

根据油气二次运移理论对曙光地区延长组特低丰度油藏的油气运移机理进行了分析,主力烃源岩延长组长7段在燕山中、晚期(白垩纪)大量生烃排烃,长6、长8砂体成为油气运移的疏导层。在油气的运移过程中,由于物性的差异、岩性变化形成局部遮挡,使得少量石油"残留"下来,从而形成"石油运移泄流区内的低丰度油藏"的成藏机理。该类油藏是鄂尔多斯盆地,甚至国内其他大型盆地应该重视的主要油藏类型之一,也应该是今后研究的主体和勘探开发的重要目标。

Accumulation mechanism of low-abundance oil reservoirs in the Yanchang Formation of Shuguang oilfield,the Ordos Basin

The mechanism of oil-gas migration of the exceptionally low-abundance oil reservoirs in the Yanchang Formation of the Shuguang oilfield,Ordos basin,is analyzed in this paper by applying the theory of secondary hydrocarbon migration.The results show that the major source rocks of the Chang-7 member(the 7th member of the Yanchang Formation) had generated and expelled large amount of hydrocarbons during the mid-late Yenshanian(Cretaceous),and the Chang-6 and Chang-8 sandbodies acted as carriers beds for hydrocarbon migration.During the migration process,small amount of hydrocarbon was 'left behind' because of local barriers formed by physical property contrast and lithology changes,and formed the so-called low-abundance oil reservoirs inside the migration-discharge zone.This kind of reservoir is one of the most important reservoirs that deserve much more attention not only in Ordos Basin but also in other large basins in China.It shall be regarded as an important target for future hydrocarbon exploration.