The Research Of Hydrocarbon Accumulation Conditions Of Buried Hills In Shijiutuo Uplift Of Bozhong Depression

As one of the important oil and gas exploration sites in Bozhong Depression,Shijiutuo Uplift has a good prospect of exploration.Buried hill as an exploration layer,the oil and gas accumulation conditions and the main control factors are lagging behind.Thus,taking the buried hills in Shijiutuo uplift as the main research object.On the basis of previous studies,this paper systematically analyzes the relevant data from petroleum geology and geochemistry,and analyzes the data from the aspects of hydrocarbon conditions,reservoir conditions,seal ability,trap,migration and preservation.Which is based on the anatomy of typical buried hill reservoirs and summarizes the main controlling factors and reservoir formation model of buried hill in Shijiutuo uplift.The third section of Shahejie formation hydrocarbon source rock in Bozhong Sag is the main source for the buried hills hydrocarbon reservoir in Shijiutuo uplift,and part of the region for Bozhong sag and Qinnan sag of the third section of the mixed input.It's rich in organic matter,and well on organic type,and high in organic maturity.Besides,the first section hydrocarbon source rock has some contribution too.In general,the oil in buried hills hydrocarbon reservoirs show the characteristics of the mixed crude oil.There develops three layers of strata and three kinds of reservoirs in Shijiutuo Uplift buried hills,which are clastic rocks,carbonatite rocks and metamorphic rocks.The reservoir is controlled by lithology,tectonic movement and the depth of the buried hillThe two sets of area mud seal of the Paleogene Dongying formation and the first section of Shahejie formation overlaps the buried hills.The difference between the main strata and the tectonic amplitude of buried hill is different,which makes the difference between the buried hill and the lithology.And the seal condition of the tilting end is better than that of the mortar body.Buried crude oil as a whole to the main crude oil,accompanied by a small amount of heavy oil.Natural gas is associated with oil.Oilfield water salinity is low,which generally lower than the seawater,and the average value is 12.05g/L.The main water types are the calcium chloride magnesium and the sodium bicarbonate,indicating the semi-closed and closed water type.The dominating factors for hydrocarbon accumulation in buried hills are high quality reservoir,advantageous transportation system and strong filling of near oil source.The oil and gas accumulated rapidly in late period.And its accumulation modes could be divided to two types which are single sag mixed sources compound transporting system type and double sags mixed sources compound transporting system type.