Sedimentary differentiation and its oil-gas geological significance of the Yingshan Formation platform in the west of Manjiaer depression in the Tarim basin
Large karst and fault-controlled oil and gas fields,such as Tahe,Fuman,and Shunbei,have been discovered in the middle and lower Ordovician Yingshan Formation in the western Manjiaer depression.This formation is the primary target for oil and gas exploration in the Tarim basin.However,the lack of breakthroughs in facies-controlled fields and the ambiguity surrounding platform sedimentary structures have hindered further exploration.This study analyzes sedimentary facies,platform structure,and oil and gas geological significance based on the latest drilling and contiguous seismic data.Analysis of interwell and seismic facies reveals a rapid east-west transition in Ordovician sediments and strong differentiation of the carbonate platform.The lower part of the Yingshan Formation exhibits a sedimentary pattern transitioning from basin-slope-open platform-restricted platform to basin-slope-open platform.As sea level rose in the upper part of Yingshan Formation,the platform margin gradually regressed westward,developing into a basin-slop-wide and slowly evolving open platform.The platform margin displays a north-south difference:the gradient decreases from south to north,and the platform margin transitions from an accretion structure in the south to a regressive structure in the north.This difference in platform structure results in the varied distribution of carbonate reservoir groups related to specific facies zones.From Gucheng westward to Caohu,the Yingshan Formation platform margin shifts from accretion to retrogradation,resulting in the development of thick,vertically superimposed reef-flat reservoirs.In the north,the retrograde characteristics of the platform margin in both the lower and upper Yingshan Formation members result in a favorable reservoir-cap combination:high-energy mound reservoirs in the lower Yingshan Member and slope facies in the upper Yingshan Member formed a good reservoir-cap combination.This structure lies in the migration direction of source rocks in the Manjiaer depression,making it highly significant for the formation of large-scale hydrocarbon accumulations in primary lithology traps.
万方数据
维普
