云南陆良盆地新近系茨营组近岸水下扇沉积特征

陆良盆地上新统茨营组主要为一套扇三角洲沉积体系的陆相断陷湖盆沉积,其中,在茨二、三段盆地东部边缘断阶带发育一套近岸水下扇沉积。根据岩性组合特征、沉积序列、测井和地震响应等划分出扇根、扇中和扇端三个亚相。钻探资料显示在扇中亚相和扇端亚相识别出辫状水道微相、辫状水道间微相、扇中前缘微相、扇端泥微相和扇端席状砂微相5个沉积微相,扇中辫状水道是重要的储集砂体类型。结合成藏分析,认为该区近岸水下扇体具备形成构造-岩性气藏的条件,储层的分布对气藏富集具有明显的控制作用,沿形成扇体的辫状水道和扇中前缘砂体应成为扩展勘探领域的有利区带。

Sedimentary characteristics of nearshore subaqueous fan of Neogene Ciying Formation in Luliang basin.Yunnan

The Pliocene Ciying Formation in Luliang basin mainly consists of a fan-delta depositional system of nonmarine faulted lacustrine basin,in which a nearshore subaqueous fan was deposited in the second and third member of Ciying For- mation in the step-faulted zone of the eastern basin.On the basis of the lithelogy association,the sedimentary sequcnce and the characteristics of seismic and well logging responses. the nearshore subaqueaus fan can be subdivided into three subfacies:the fan root.the fan medium and the fan end. Drilling data show that five micro-facies such as the braided stream,the space between braided streams,the leading edge of fan medium subfacies,the mud and sheet stone and the fan-end subfacies can be identified in the fan medium and the fan end subfacies,of which the braided stream of fan me- dium subfacie is the main reservoir.By combining with the analysis on pool formation,it is considered that the near- shore subaqueous fan is of setting to form the structure-li- thologic reservoir and the lithologic reservoir.The distribu- tion of reservoir obviously controls the enrichment of gas pool,and the favorite area for hydrocarbon exploration should be along the main water channel and the fan-mid- dling front sand where the fan bodies were formed.