Abstract:

Thick salt deposits were developed in Paleogene in the northern Dongpu depression. Under sustained stretching stress, extensional forced folds were formed in the overlying formations of salt beds due to their differential subsidence.At the same time, continuous down-tilting of the secondary fault blocks in the underlying formations resulted in increasing of downslide shear stress and even exceeding the shear strength of salt beds, thus listric detached faults were formed in the overlying beds,and rollover anticlines were formed in the upper wall of salt detached faults. The detached deformational salt structures would not only constitute good migration pathway but also provide various traps for hydrocarbon accumulation,such as oil and gas reservoirs in fault block traps, extensional forced fold traps, rollover anticlinal traps, traps in the footwall of the detached faults and reverse drag fault traps in Dongpu depression. The development of detached deformational salt structures led to the formation of hydrocarbon enrichment in the central uplift zone of Dongpu depression

Key words: Dongpu depression, salt structure, detached deformational salt structure, extensional forced fold, rollover anticline