CHARACTERISTICS AND SIGNIFICANCES OF HYDROCARBON SHOWS IN THE NIQIUJI SAG, THE SOUTHERN NORTH CHINA BASIN

There are 16 exploration wells drilled in the Niqiuji Sag,the Southern North China Basin and 7wells of them have obtained hydrocarbon shows.The Well Nan 12 located in Dawangzhuang structure is an industrial discovery well with producing commercial crude oil of 32.26 m³s in well testing.In this article,statistics of the oil and gas shows was made and the conclusions have obtained as follows: the oil and gas shows occur mainly in Shuangfu Formation in Paleogene,the predominant reservoir rocks are medium-grained and fine-grained sandstones,oil shows occur mainly in the depths of 1 000 to 2 000 meters and gas shows occur mainly in the depths of 3 000 to 4 000 meters,the crude oil is characteristic of coal-derived oil and has undergone biodegradation and water-washing.The above conclusions suggest that there is at least one epoch of petroleum formation,migration and accumulation in Niqiuji depression.The preliminary conclusions for exploration orientation include that both primary and secondary pool are the exploration targets,the Upper Cretaceous is a disadvantageous factor for petroleum accumulation because it may be a barrier of vertical petroleum migration from the source rocks in CarboniferousPermain to the reservoirs in the Paleogene.