RETURN TO THE ORDOS BASIN：SOME IMPLICATIONS FROM ITS PETROLEUM EXPLORATION HISTORY

There was a tortuous way in the early stage during the last 40 years of petroleum exploration in the Ordos Basin due to shortage of subjective knowledge and limitation of objective conditions(topography et al).The exploration was terminated in the basin for a time and was carried out in the Weihe Graben area.In the end of 1968,Minister Li Siguang demanded that the exploration activity should be given up in the graben area and return to the basin according to his theory of Neocathaysian structural system.Consequently,discoveries of the Middle and Lower Jurassic reservoirs in wells QC and HC-2 and in Maling oilfield revealed the prologue to a great battle for oil as when Changqing oilfield was being opened up in 1970s.With success in Wuqi and Zhidan area,the well known "Qin-Hua-Wu petroleum system" was popularized.In the last 10 years,with determination of deltaic system of the Upper Triassic Yanchang formation and discovery of Qinyang oilfield,the "old" Ordos basin has really restored its vitality.