The Gas Source Condition And Gas-controlling Study Of Natural Gas In Ordovician Of West Ordos Basin

The sedimentary of the Ordovician in the western margin of Ordos Basin is extensively distributed,and the strata are well developed.Its lithology mainly contains limestone?dolomite?marlite?mudstone.There exists good hydrocarbon source rock and the distribution area.Through the evaluation of hydrocarbon source rock,we can discuss the contribution of effective hydrocarbon source rock and the hydrocarbon-generating strength,also can determine the source of gas reservoir,and then offer the basis of oil and gas exploration of Ordovician in the western margin.This paper makes a good use of former researches and uses many datas like geology,log,geochemistry.After having a lot of analysis of samples,we have discussed the development and distribution of hydrocarbon source rock,abundance,type and maturity of organic matter.Besides,we calculate the gas-generating strength combined with the hydrocarbon generating and evolution characteristics of source rocks.At last,we study the control of gas reservoir according to the hydrocarbon source condition.After having comprehensive analysis,we think,abundance of organic matter is low whose type is mainly ?-?1 and most of which have reached high mature stage.However,there are only few samples in immature stage.By using logging,we have identified effective hydrocarbon source rock,and the thickest is Wulalike Formations with the best development of high quality source rocks.Kelimoli Formations take the second place,Lashizhong Formations is the worst.According to the analysis of burial history and the history of hydrocarbon source rocks of Yutan 1 well,it thinks gas reservoir forming time mainly occurred in the late Triassic-Early Cretaceous.According to the hydrocarbon-generating strength of the Ordovician in the western margin,we can see the cavity groove area of Huitan 1-Yutan 1 in south is the main hydrocarbon zone.Huitan 1 well can yield more than 16×108m3/km2,followed by the Qitan 1 well in north.Through the study of thickness of effective hydrocarbon source rock,hydrocarbon-generating strength and gas source,combined with gas and water distribution characteristics,we can see hydrocarbon source rock of Ordovician has a certain ability of hydrocarbon-generating and form the self-generating and self-storage reservoir type(Yutan 1 well).