志丹地区延长组三角洲的识别特征及演化

Identification characteristic of delta facies and its evolution in Zhidan area

目的探究志丹地区延长组沉积环境及古地理演化,进而寻找有利砂体及石油聚集区。方法采用野外观察与室内研究相结合的方法。结果研究区主要发育三角洲沉积体系,在古地理演化过程中,长10,长9,长8为三角洲前缘亚相;长7北部为三角洲前缘,南部发育深湖亚相;长6期发育三角洲前缘,三角洲发育达到鼎盛时期;长4+5,长3,长2三角洲逐渐萎缩,其北部均为三角洲平原,南部为三角洲前缘及浅湖;长1演化为三角洲平原。结论分支河道及水下分流河道砂体是下一步勘探开发的重点。

Aim To ascertain the depesitional system in Zhidan area, forthermore, probe favorable sand body and high-yield oil area. Methods Combined research methods of field exploration and indoor analysis are adopted. Results It is held that normal delta in Yanchang formation is mainly developed in Zhidan area, by sedimentary facies analysis, forthermore, sub-facies and micro-facies are also recognized. During the evolution of paleo-geography, delta front was developed in study area in Chang 8 ,Chang 9 ,Chang 10,and north of study area in Chang 7 ,deep-lake in the south of study area in Chang 7 ;delta front was developed in study area in Chang 6 member, in which delta is developed best; delta is shrinking away gradually, delta plain was developed in north of study area and delta front and shallow-lake were developed in the south of study area in Chang 2, Chang 3, Chang 4 ＋ 5 member of Yanchang formation. And evolved entirely to delta plain in study area in Chang 1 member. Conclusion Distributary channel and subaqueous distributary channel of delta are still the target of explaration and exploitation in the near future.