准噶尔盆地车排子地区石炭系顶部风化壳结构及其控藏作用

基于实钻资料与地质综合研究，系统分析了准噶尔盆地车排子地区石炭系顶部风化壳结构地质特征及其发育主控因素，总结了风化壳结构发育模式与控藏作用。研究认为，车排子地区石炭系顶部风化壳垂向上具层状结构，自上而下依次为风化粘土层、水解层、淋滤层。风化壳结构形成主要受控于原岩岩性、间断时间和古地形三大因素。风化粘土层和水解层起着封盖、遮挡作用，分布较广的淋滤层具有较好的储集性能，利于油气横向输导。在有水解层或风化粘土层条件下，形成“毯砂”“壳”双输导模式；反之，则油气上窜或下灌，形成单一输导体。在其控制下，该区石炭系顶部风化壳发育壳内、毯砂前缘和复合岩性3种油气藏分布类型。

Structure and reservoir-controlling of top Carboniferous weathering crust in Chepaizi area,Junggar Basin

Based on drilling data and integrated geological research,structural characteristics and main controlling factors of the weathering crust on top Carboniferous in Chepaizi area of the Junggar Basin were systematically analyzed.The development model of weathering crust structure and its reservoir-controlling was summarized.Results show that the weathering crust features in vertically layered structure,consisting of weathered clay layer,hydrolysis layer and weathering leached layer in top-down order.The weathered clay layer is thin and has limited areal distribution and poor physical property.The hydrolysis layer is thicker and has poor physical property but wide distribution in most areas.The weathering leached layer is very thick and has better physical property and extensive distribute in the whole area.The structure of the weathering crust is mainly controlled by facies of mother rocks,hiatus time and paleotopography.The weathered clay and hydrolysis layer serve as cap rocks for petroleum reservoir,while the weathering leached layer has favorable physical property and thus can serve as lateral migration pathway on top of the Carboniferous.Under the condition of the hydrolysis layer or weathered clay layer,double migration path model can be built which includes carpet sand and wea-thering crust.Otherwise,there would be one migration path with oil and gas channeling or irrigating.Under the control of weathering crust structure,there developed three types of reservoirs including weathered crust,carpet tip and composite lithology in the Carboniferous.