The geological conditions of the ultra-deepwater area are complex

and the seismic data is disturbed by many factors.The faults have multiple interpretation solutions

so the accuracy of the structure interpretation is seriously affected.According to the fault characteristics of the 3D working area in ultra-deepwater region

the coherence technique is used for fault interpretation and fault analysis

in order to better understand and more accurately interpret the structure characteristics of the whole Baiyun Sag.It is indicated that the along-horizon coherent slice could apparently reveal the planar distribution of the fault system developed in certain periods.The top surface of Enping Formation (T

7

0

) is a regional unconformity and the rift to sag transition interface of Baiyun-Liwan Sag.The faulting and rifting phase of Baiyun Sag ended in early Oligocene

then sag and depression became the dominate characteristics afterwards.The study demonstrates that the rift to sag transition interface T

7

0

of Baiyun-Liwan Sag has significant control on hydrocarbon accumulation in the ultra-deepwater area of ZhuⅡDepression.