柴达木盆地昆北油田切6区古近系辫状河三角洲沉积特征与砂体叠置模式

Sedimentary Characteristics and Sand-body Superposition Patterns of Paleogene Braided River Delta in Q6 Block of Kunbei Oilfield,Qaidam Basin

为了明确柴达木盆地昆北油田古近系辫状河三角洲砂体叠置关系以指导油田精细挖潜,综合利用岩心分析、测录井及生产动态资料精细表征沉积特征,建立辫状河三角洲沉积模式,明确相控储层砂体展布规律及叠置类型。研究表明:昆北油田切6区古近系岩石类型丰富,以含砾砂岩、粉细砂岩为主,成分成熟度中等—低,结构成熟度中—差,主要发育水上辫状河三角洲平原及水下三角洲前缘2类亚相,其中平原亚相主要发育分流河道、越岸及泛滥平原3种沉积微相,三角洲前缘主要发育水下分流河道、河道侧翼、河口坝、席状砂及河道间5种沉积微相;总结出辫状河三角洲砂体"2类5种"叠置模式,包括堆叠型、拼接型、决口型、溢岸型及孤立型。

In order to clarify the superposition relation of the Paleogene braided delta sandbodies in Kunbei oilfield of Qaidam Basin to guide the fine potential tapping of the oilfield,the sedimentary characteristics of the braided river delta were characterized,the sedimentary pattern of it was established,and the distribution law and superposition types of the facies-controlled reservoir sandbodies were determined based on core analysis,logging data and dynamic production data.It is shown that,there are rich rock types in the Paleogene of Q6 area of Kunbei oilfield,which are mainly conglomerate sandstone and fine siltstone;their component maturity and structural maturity are medium to low;2 subfacies of braided river delta plain and subaqueous delta front are developed,there are 3 sedimentary microfacies of distributary channel,overbank and flood plain in the braided river delta plain subfacies,and there are 5 sedimentary microfacies of subaqueous distributary channel,channel flank,mouth bar,sheet sand and interchannel in the subaqueous delta front subfacies.There are 5 sandbody superposition modes,including the connected-incised stacked mode,the simple splicing mode,the crevasse splay mode,the tracking overbank mode and the isolated channel mode.