鄂尔多斯盆地南部延长组长7段致密油成藏条件与富集主控因素

Tight oil accumulation mechanisma of Chang 7 interval in southern Qrdos Basin

为评价鄂尔多斯盆地南部延长组长7段致密油的勘探前景,以地化分析测试、场发射扫描电镜、平衡深度法等研究手段,通过对烃源岩、储层、油气运移等方面的研究,深入探究该区长7段致密油各项成藏条件并进行潜力评价。结果表明,该区长7段优质烃源岩分布稳定,生油能力强,且上下邻近砂岩发育,具有良好的源储配置条件;该区致密油藏在早白垩世大规模形成,属于晚期成藏;在形成和聚集过程中主要受沉积微相和物性条件控制;根据评价结果可知,长71亚段油层组I类,Ⅱ类有利区发育较多。研究后认为,长7段致密油藏富集的主控因素有:源储配置是致密油形成的关键因素,各类孔隙发育是致密油富集的重要前提,顶部盖层和侧向遮挡是致密油保存的必要条件。

The tight oil of Chang 7 interval was found at the south part of Ordos Basin,but the research of accumulation geological conditions was seldom involved in study.In order to evaluate tight oil exploration prospect of Chang 7 interval,the analysis of geochemical test,field emission scanning electron microscopy(sem)and balance depth research were used to study sedimentary microfacies,reservoir rock and hydrocarbon migration.Finally the control factors of tight oil accumulation conditions in study area were identified.The high quality source rocks of Chang 7 interval are widely developed in the study area,the sandstone near hydrocarbon source rocks.The geological conditions of forming tight oilreservoir is good.The tight oil accumulation period in Yanchang Formation is at early Cretaceous,tight oil accumulation occurred in late stage.Tight oil reservoir formation and enrichment are controlled by sedimentary microfacies and quanlity reservoirs.The Chang 7 1interval is the main targets for exploration of tight oil in Yanchang Formation in study area.The main controlling factors of Chang 7 tight oil enrichment are as follows:good configuration of source rock and reservoir and constant charging are the key to the formation of the tight oil province,all kinds of pore development are the premise of tight oil enrichment,the top of the cap rocks and lateral block is necessary for dense oil saving.