Palaeogeomorphology reconstruction and sandbody distribution of the Chang 7-6 intervals of Triassic Yanchang Formation in northern Zhenyuan area,Ordos Basin
Cui Longtao1, Hao Shuai2, Wang Chunping3, Zhu Wentao2
1 Tianjin Branch of CNOOC Limited,Tianjin 300452
2 Xinzhou Branch of PetroChina Coalbed Methane Company Limited, Xinzhou 036600, Shanxi
3 The Second Oil Producing Plant of Qinghai Oilfield Company,PetroChina, Haixizhou 816400,Qinghai
Triassic Yanchang Formation is one of the main targets of oil and gas exploration in northern Zhenyuan area. The types and distribution of sandbody are controlled by the palaeogeomorphology. Based on cores,well log analyses,and sandy debris flow viewpoints proposed by Shanmugam,the gravity flow deposits can be divided into turbidites,sandy debris flow sediments and slump rocks. After building the high-resolution sequence stratigraphy framework,an optimized backstripping method is used to restore the deposited terrain,and the palaeogeomorphology map of the studied area is drawn by short-term base level unit. The study finds that the north of Zhenyuan situated near the depositional slope break zone,Chang 73 was of the maximum transgression,the degree of the slope is 0.45,turbidites and sandy debris flow sediments developed in the deep lake in the northeastern part of the study area. From Chang 73 to Chang 72 depositional periods,the base level decended,the mouth bar and the slope break zone gradually advanced to the lake,and the angle of the slope break zone began to decrease;from Chang 72 to Chang 71 depositional periods,the base level began to rise,the slope break and the sandbody gradually retreated to the shore. From Chang 63 to Chang 61 depositional periods,the base level decended,sediments deposited in the basin,the slope decreased to 0.1°,sandy debris flow sediments and slump rocks developed under the slope break.
Cui Longtao,Hao Shuai,Wang Chunping et al. Palaeogeomorphology reconstruction and sandbody distribution of the Chang 7-6 intervals of Triassic Yanchang Formation in northern Zhenyuan area,Ordos Basin[J]. JOPC, 2015, 17(6): 805-812.
