大涝坝地区下白垩统巴什基奇克组浅水三角洲沉积特征

Sedimentary characteristics of shallow-water delta of the Lower Cretaceous Bashijiqike Formation in Dalaoba Area,Tarim Basin,China

塔里木盆地大涝坝地区下白垩统巴什基奇克组砂体井资料少,分布集中,沉积微相研究薄弱。根据岩心观察、岩矿鉴定和测井相分析,基于密井网区单井、连井沉积微相,采用叠后波阻抗反演及地震相刻画拟合、匹配和拓展方法,预测疏井网区沉积微相类型,刻画巴什基奇克组沉积微相平面展布特征;结合岩相古地理特征,建立巴什基奇克组理想沉积模式。结果表明:巴什基奇克组岩相主要包括砾岩相、(粉)砂岩相及泥岩相,进一步划分为块状层理砾岩相、含砾砂岩相、斜层理(粉)砂岩相、平行层理砂岩相、粒序层理砂岩相、变形层理(粉)砂泥岩相和氧化色泥岩相;巴什基奇克组主要形成于浅水三角洲前缘亚相,发育水下分支河道、河口坝和河道间湾等沉积微相类型。该结果可为研究区制定勘探开发方案提供参考。

Due to the scarcity and concentrated distribution of well data,the research on sedimentary microfacies of Lower Cretaceous Bashijiqike Formation in Dalaoba Area of Tarim Basin is relatively weak.Sedimentary microfacies were studied by core observation,rock and mineral identification and well logging facies analysis,combined with post-stack impedance inversion and seismic facies characterization.Based on the analysis of single well and multi-well sedimentary microfacies in dense well pattern area,the methods of post-stack impedance inversion and seismic facies characterization fitting,matching and expansion were used to predict the types of sedimentary microfacies in sparse well pattern area,and the planar distribution characteristics of sedimentary microfacies of Bashijiqike Formation were described.Combined with the lithofacies and paleogeography,the depositional model of Bashijiqike Formation is established.The results show that the lithofacies of Bashijiqike Formation mainly includes conglomerate facies,(silty)sandstone facies and mudstone facies,which can be further divided into massive bedding conglomerate facies,pebbled sandstone facies,oblique bedding(silty)sandstone facies,parallel bedding sandstone facies,graded bedding sandstone facies,deformed bedding(silty)sand mudstone facies and oxidation color mudstone facies.The Bashijiqike Formation is mainly formed in shallow-water delta front subfacies,and the sedimentary microfacies include subaqueous branch channel,mouth bar and subaqueous interbranching bay.The results provide reference for further exploration and development schemes in the study area.