Architecture, depositional pattern of syn rift sediments in the Northern Song Hong basin and its petroleum system association

Rifting with syn rift sediments originally was formed during two tectonic phases in three stages. The syn rift deposits were composed of four units that have been identified by distinct seismic facies. The seismic expression of these syn rift units gives an idea about the linkage of their deposition with different stages of rift evolution. The lowermost units have wedge shaped reflection packages and hummocky internal reflection configuration, representing initial rifting in early rift stage. The overlying two units comprising divergent reflection, prograding pattern with aggradations on footwall represent climax rift stage and the topmost unit with sub-parallel reflection configuration represents the late phase. The units deposited during the rift climax stage have a good source rock potential, whereas the unit deposited in the late rift stage possesses favourable reservoir facies making a complete petroleum system within syn rift sediments.