准噶尔盆地西北缘三叠系层序地层与隐蔽油气藏勘探

Sequence Stratigraphy and Subtle Reservoir Exploration of Triassic System in Northwestern Margin of Junggar Basin

层序地层学及层序地层原理指导下的地震资料解释为地层、岩性油气藏勘探提供了理论和技术支持。为配合准噶尔盆地西北缘油气勘探从克乌断裂带上盘向下盘、从构造油气藏向地层、岩性等隐蔽油气藏的转变,利用陆相层序地层学理论和地球物理资料,将三叠系划分为1个二级层序、5个三级层序和8个体系域,进而总结出拗陷完整型和拗陷残缺型两种层序类型。结合测井约束地震反演和井间沉积对比,探讨了三叠系砂体结构和湖侵体系域地层超覆、湖退体系域及最大湖泛面附近小规模滑塌浊积体岩性透镜体等5种圈闭发育模式。油气成藏综合条件分析指出有效圈闭和油源断层的识别是制约斜坡带岩性油气藏勘探的关键。

Sequence stratigraphy and seismic data interpretation based on sequence stratigraphic principle provide useful theory and technology for exploration of stratigraphical and lithological oil and gas reservoirs. In order to fulfill the needs of exploration changes from hanging wall of Ke-Wu fault zone to its foot wall and from structural reservoirs to subtle stratigraphical and lithological pools, sequence stratigraphy and sedimentary characteristics were studied carefully with continental sequence stratigraphy theories and geophysical data. As a result, the Triassic system was divided into one second order sequence, five third order sequences and eight system tracts. Two sequence styles of depressions, i.e. wholly developed depression and partially developed depression, were recognized. The architectures of sandstone and development features of five subtle trap types were discussed according to sequence stratigraphic principle, logging constrained seismic interpretation and sedimentary strata correlation of wells. Based on the analysis of oil and gas accumulation conditions, the hydrocarbon accumulation model was established. It is indicated that the effectiveness of traps and recognition of oil/gas transporting faults are key constraints in exploring the lithological oil and gas reservoirs in the slope zones.