莺歌海盆地东方气田砂质碎屑流沉积相研究

Sedimentary Facies of Sandy Debris Flow in Dongfang Gas Field in Yinggehai Basin

莺歌海盆地东方气田新近系莺歌海组二段砂体非均质性强,沉积模式一直以来存在争议,且当前沉积相认识与井点实际钻遇情况不符,严重制约了气田开发后期的调整挖潜。通过研究区典型岩心标志及井震结合地震相的精细识别,结合盆地的古地貌特征及特殊沉积背景,重新定义了研究区沉积相类型及沉积模式,并开展精细的沉积微相研究,查明了砂体非均质性的主控因素,对研究区小层级别储层非均质性精细研究及调整挖潜具有重要的意义。研究结果表明东方气田莺歌海组二段为北西向物源砂质碎屑流成因、受泥质水道改造的海底扇沉积,以侵蚀水道、水道侧向溢出朵体及前端朵体沉积为主;砂体展布整体受控于物源供给和古地貌,研究区中东部的泥底辟高地始终影响沉积微相展布和侵蚀水道的发育,后期泥质水道的强烈改造是导致研究区砂体强非均质性的主要原因。

Strong heterogeneity of sandbody,controversial sedimentary model,and inconsistent drilling situation at well sites in the second member of Yinggehai formation in Dongfang Gas Field,seriously restric the adjustment and tapping potential in the later stage of gas field development.Through the fine identification of typical core marks and well-seismic facies in the study area,combined with the paleogeomorphic characteristics and special sedimentary background of the basin,the sedimentary facies and model were redefined,the fine research of sedimentary microfacies were carried out,the main controlling factors of sand body heterogeneity were identified.It is of great significance to the fine research of small scale reservoir heterogeneity,adjustment and tapping potential in the study area.The results show that the second member of Yinggehai formation in Dongfang Gas Field is a submarine fan formed by northwest provenance sandy deris flow and reformed by muddy gravity flow.The main deposition types include erosion channel,lateral overflow lobe and front lobe.The distribution of sandbody is controlled by provenance supply and paleogeomorphology.The distribution of sedimentary microfacies and the development of erosion channels are always affected by the diapir highlands in the middle and east of the study area.The strong transformation of the muddy channels in the later stage is the main reason for the strong heterogeneity of the sand body in the main gas bearing range in the study area.