In the similar conditions of sedimentary sand bodies and fault conduit system, the problems have existed within sandstone reservoirs of Es3Mid in Niuzhuang Sag for a long time as follows: 1)The distribution of sandstone porosity are inconsistent with hydrocarbon accumulation, which characterizes that the oil in the sandstones with low porosity rather than those with high porosity. 2)The oiliness of sandstones which have the same property are different, and the sandstones that the property is approximate show a distinct oil-bearing degree. This paper analyses the reservoir conditions and determines the critical porosity of the sandstone reservoirs in Niuzhuang Sag in accumulation period in paleo porosity recovery. The results demonstrate that the reservoir property is low at present and some of the reservoirs become tight, the paleo porosities which range from 18% to 25% are far more than the critical porosity. Because the loss of pore in bury history is different, so the porosity at present can not reflect that in accumulation period. The porosity was high in accumulation period, which cannot represent that it must high in present. The present reservoir location is consistent with the distribution of the high paleo porosity in accumulation period, which indicates that the high porosity belts prone to accumulate hydrocarbon because of the dominant migration pathways that generated by property differential in the similar fault conduit condition. Thus, the hydrocarbon mainly accumulates in the high porosity belts and the paleo porosity in accumulation period is a vital control factor. As a result, the sandstones with high paleo porosity of Es3Mid in Niuzhuang Sag have a major exploratory potentiality.
. The controls of sandstone paleo-porosity in accumulation period to hydrocarbon distribution：A case study from Es3Mid in Niuzhuang Sag, Dongying Depression[J]. Chinese Journal of Geology, 2014, 49(1): 147-160.