Abstract:

The hydrocarbon reservoirs in the Neogene shallow deltas are the main type of recent discoveries in Bohai Sea.Using various data such as depositional facies analysis,grain size,paleontological marker and paleoenvironment response,we have summarized the sedimentary characteristics and development settings of the shallow deltas,determined their distribution pattern and controls and discussed their favorable conditions of hydrocarbon accumulation.The study results show that:1) these shallow deltas developed in shallow and gentle lakes;2) multiple stages of sand-mud interbedding occurred due to the periodical changes of lake level;3) as the main sedimentation type in these deltas,the sublacustrine distributary channels are stable in their regional distribution.These depositional characteristics may lead to good reservoir-seal combinations in the shallow deltas,and the associated later strike-slip faults are favorable to developing various traps,with sufficient oil sources and an unobstructed hydrocarbon migration.Therefore,these shallow deltas are good in hydrocarbon accumulation conditions and are great in exploration potential.