合肥盆地下白垩统朱巷组沉积相与油气勘探前景

合肥盆地是中国东部较大的含油气远景沉积盆地，但油气勘探一直未有突破。下白垩统朱巷组被认为是合肥盆地主要的烃源岩层之一，但对其沉积相和古地理的认识尚存在分歧，研究未受到足够的关注。根据野外剖面测量、沉积层序、沉积构造鉴别，以及岩石薄片显微观察和粒度分析，认为下白垩统朱巷组沉积物来自盆地东侧的张八岭隆起，主要为冲积沉积，冲积扇、河流、洪泛平原、滨湖—浅湖等沉积相带自东向西依次展布。大桥凹陷一带的朱巷组不发育深湖相沉积，不具备生烃条件，这不同于前人的认识；大桥凹陷古城地区钻孔揭示的原“朱巷组”暗色泥岩烃源岩层累计厚度在600m以上，是否属于下白垩统朱巷组需要进一步研究，其可能仅形成于郯庐断裂带内部的小型断陷盆地。郯庐断裂带中的小型断陷盆地可能是研究区油气勘探具有潜力的新领域。

Sedimentary facies and prospects for oil-gas exploration of Zhuxiang Formation of Lower Cretaceous in Hefei Basin

The Hefei Basin is a sedimentary basin with oil and gas prospects in the east of China.There has been no breakthrough in oil and gas exploration for decades.The Lower Cretaceous Zhuxiang Formation is considered to be one of the main source rocks in Hefei Basin，and its sedimentary facies and paleogeography have not received enough attention.According to the field profile survey，sedimentary sequence，sedimentary structure identification，microscopic observation of rock slices and grain size analysis，it is concluded that the Lower Cretaceous Zhuxiang Formation mainly belongs to alluvial deposits.The distribution of sedimentary facies consist alluvial fan，river，flood plains and offshore lake-shallow lake from east to west and its source came from the eastern basin of the Zhangbaling uplift belt.The analysis shows that the Zhuxiang Formation in the area of Daqiao Depression west of the Tanlu Fault may not have hydrocarbon generation conditions，which is different from the previous understanding.The drilling results in Gucheng area of Daqiao Depression in the eastern part of the basin show that the dark mudstone has cumulative thickness over 600 meters and it is a set of good source rock.It was formed in a small faulted basin in the Tanlu Fault zone.Whether it belongs to the Zhuxiang Formation of the Lower Cretaceousor not requires more study.The small fault depression in the Tanlu Fault zone may be a new field of oil and gas exploration in Hefei Basin.