Detailed analysis of palaeostructural evolution of the marker on top of Carboniferous limestone shows that the Tazhong 45-Manxi 1block was a large palaeo anticlinal structure before the deposition of Paleogene. The structure was basically stable despite the facts that there were displacement of structural high and modification of structural features during its long succeeding development. The neotectonic movements in Paleogene

especially in Neogene

changed completely the structural appearance into one limb of a north-dippping large nose-like structure

resulting in different hydrocarbon migration direction and reservoiring conditions. In the area along the direction of hydrocarbon migration and accumulation from limb to crest of the structure

the updip pinchout zones of Donghe sandstone in the lower part of Carboniferous and groups of low to very low amplitude structural traps would be favourable to ate reservioring. They would

therefore

be the potential hydrocarbon accumulation zones.