【摘要】 松辽盆地徐家围子断陷下白垩统营城组四段致密砂砾岩储层是该区深层天然气勘探的储量接替层系之一,为预测其有利勘探区带,应用高精度层序地层学方法,研究了营四段层序地层与致密气藏形成的关系。①根据地层发育特征、地层旋回性和岩相发育特征,将营四段划分为2个三级层序,每一层序界面都有明显的地震响应、测井响应和沉积学标志特征。②建立了营四段层序地层格架,营四段下层序(Sq1)分布仅局限在断陷中心部位,发育半深湖—扇三角洲前缘亚相,以暗色泥岩为主,其为优质的烃源岩,可为上覆营四段提供气源;营四段上层序(Sq2)的辫状河三角洲前缘亚相物性好,是主要储层发育的有利部位。③构建了营四段致密砂砾岩气藏的2种成藏模式:一种是沙河子组为烃源岩,断裂为运移通道,砂砾岩与火山岩为储层的下生上储式成藏模式,有利勘探区位于兴城、徐东和徐南地区,预测天然气资源潜力达450×108 m3;另一种是营四段下层序暗色泥岩为烃源岩,上层序砂砾岩为储层,自生自储或下生上储式成藏模式,有利区位于断陷中心的XS22井区,预测天然气资源潜力约为100×108 m3。更多还原

【Abstract】 Tight sandy conglomerate reservoirs in the 4th member of the Lower Cretaceous Yingcheng Formation,Xujiaweizi fault depression,Songliao Basin,are potential targets of deep gas exploration.In order to predict play fairways there,high-resolution sequence stratigraphic methods were used to study the relationship between sequence stratigraphy and tight gas pooling.First,according to the features of stratigraphic development,cyclicity and petrographic facies,the 4th member of the Yingcheng Formation was divided into 2 third-order sequences with each having its own specific seismic responses,logging responses and sedimentological markers.On this basis,a sequence stratigraphic framework is then established for this study area.The lower sequence(Sq1) only occurs in the central part of the fault depression where semi-deep lake-fan delta front subfacies are developed,where quality source rocks are dominated by dark mudstones with sufficient hydrocarbons supplied to the overlying 4th member of the Yingcheng Formation.In contrast,the upper sequence(Sq2) is braided river delta front subfacies with good poroperm characteristics favorable for the development of quality reservoirs.Finally,two modes of hydrocarbon pooling are established for this study area.The first is the lower source rock with upper reservoir mode in which source rocks are in the underlying Shahezi Formation,faults act as migration pathways,and sandy conglomerate & volcanic rocks are reservoirs.For this kind of hydrocarbon pooling mode,the play fairways are located in Xingcheng,Xudong and Xunan areas with estimated original gas in place(OGIP) of 45 billion m3.The other is the indigenous-sourcing mode or the lower source rock with upper reservoir mode in which source rocks are the dark mudstones in Sq1 and reservoirs are mainly the sandy conglomerate in Sq2.For this kind of hydrocarbon pooling mode,the representative play fairways occur in the XS22 wellblock in the center of fault depression with the estimated OGIP of about 10 billion m3.更多还原