COMPLEX LITHOLOGIC RESERVOIR FORMATION CONDITION AND LAWS IN PUWEI SUB-DEPRESSION, DONGPU SAG, BOHAI BAY BASIN

Lithologic reservoirs are formed in complicated conditions in the Puwei sub-Depression,the Dongpu Sag,the Bohai Bay Basin.Wide spread mature source rocks are prolific material basis for reservoir formation.Multiple sources,various sedimentary system types and rapid changes of lithology control distribution and development of lithologic traps.Thick salt development and phase changes form good barrier bed and cap rock for hydrocarbon,which are also the main causes to develop lithologic pools with high pressure and charging.Geological factors such as frequently developed alternated unconventional reservoirs and hydrocarbon formation in multi-phases have made it more complicated for lithologic reservoirs formation.In this paper,it has been carefully researched 4 types of lithologic reservoirs developed in the area,including sandstone up-dip pinch-out trap reservoir,structural-lithologic trap reservoir(sandstone pinch-out collocated with fault),up-dip petrophysical property sheltered trap reservoir and lenticular lithologic trap reservoir.After deep studies on main factors responsible for hydrocarbon generating beds,lithologic phase changes,unconventional reservoir development,breaking activity and so on,reservoir formation law has been definite,which will play an important role for further exploration of the Dongpu Sag.