Characteristics and evolution of Cambrian sedimentary facies in Yaha-Yingmaili area of Tabei uplift,Tarim Basin
Marine carbonate rocks are the important Lower Paleozoic hydrocarbon reservoirs in the Yaha-Yingmaili area of Tabei up-lift of Tarim Basin.Clarifying the Cambrian sedimentary evolution and facies distribution in this area can provide a reliable geological basis for further exploration and development.The Cambrian sedimentary facies characteristics and sedimentary models of the Ya-ha-Yingmaili area were investigated,based on the observation and description on cores and thin sections,combined with logging data and field profile analysis.The results are as follows:(i)Located inside the Tabei large-scale carbonate platform,the Cambrian system in the Yaha-Yingmaili area developed two types of platform facies:restricted platform,and semi-restricted platform.(ii)The restricted platform,developed mainly in the Upper and Middle Cambrian,includes three subfacies(tidal flat,lagoon,and barrier beach bar),with structures such as scour surface and stratified bedding.In the profile,there presents serrated GR logging curves,and an overall high apparent resistivity.(iii)The semi-restricted platform,distributed in the Upper,Middle and Lower Cambrian,includes two subfacies(intra-platform beach and inter-beach sea),with horizontal bedding and rhythmic bedding observed.In the profile,there presents box-shaped GR logging curves,and an overall low apparent resistivity.(iv)In terms of sedimentary evolution characteristics,the sedimen-tary environment in the Early-Late Cambrian transitioned vertically from the restricted platform to the semi-restricted platform.With fluctuations in sea level,there were alternating periods of open and closed environments.
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