乍得Bongor盆地白垩系测井特征、低阻油气层成因和分布

Bongor盆地在经历断陷、坳陷构造演化过程后,不同勘探区块的含油性存在差异,同时还存在非常规油气层.地层内不同油气层的电阻率变化范围大,存在低电阻率及低对比度油气层的识别难题.为此,根据岩心、测井、试油及地化分析等资料,以Bongor盆地Baobab区块和Daniela区块为主要研究对象,分析了白垩系层序地层测井特征...

Logging characteristics of Cretaceous sequence stratigraphy and the genesis and distribution of low-resistivity oil and gas layers in Bongor Basin,Chad

After multi-stage structural evolution of faults and depressions in Bongor Basin,differences occur in oil-bearing properties of different fault depressions,and there are also unconventional oil and gas reservoirs.The resistivity of oil and gas reservoirs varies widely,and it is difficult to identify oil and gas reservoirs with low resistivity and low contrast.Therefore,according to the data of core,logging,oil test and geochemical analysis,this paper analyzed the logging characteristics of Cretaceous sequence stratigraphy,as well as the genesis and distribution of low-resistivity oil and gas reservoirs,with Baobab Block and Daniela Block in Bongor Basin as the main research objects.The results show that:1 The logging responses of R-K,M and P Formations are obviously different.The mudstone of M-P Formation develops source rocks with thin organic matter layers,and its logging characteristics are typical and easy to distinguish.M Formation in Baobab,Daniela and other blocks exhibit rapid sedimentary and overpressure logging.2 Self-generation and self-storage P Formation is the main oil-bearing formation of Cretaceous system.3 There are two types of low-resistivity oil and gas reservoirs in M-P Formation(The first type is the thin sand layer or thin argillaceous sand layer,and the second type is the unconventional oil and gas reservoir.)and one type of low-contrast oil and gas reservoir.The low-resistivity oil and gas reservoirs are mainly developed at the bottom of M Formation or the top of P Formation,showing inside source or near source accumulation and possessing extremely high natural productivity under formation overpressure.The low-contrast oil and gas reservoirs are mainly developed in the middle and lower part of the main oil layer of P Formation.The water layer of the corresponding formation is marked with flooding,and the resistivity is generally high,close to or even higher than the that of adjacent oil layer.