准噶尔盆地腹部下侏罗统曲流河地震沉积学解析

Seismic Sedimentological Analysis on Meandering River of Lower Jurassic in Hinterland of Junggar Basin

为深入探查埋深大、压实作用强、成岩程度高、储层物性差陆相油藏的区域分布规律,在准噶尔盆地腹部通过层序地层理论和基于地震拉平数据体提取的瞬时相位、均方根振幅、分频属性,对下侏罗统进行了地震沉积学解析。共识别出3个层序,SQ1~SQ2湖侵体系域均以曲河流沉积体系为主,SQ2高位体系域至SQ3以三角洲沉积体系为主。地震属性分析具有很好的一致性,结果表明:河道的形态清晰,位置可靠;河流在迁移演化过程中,河道单一,牛轭湖、决口扇等微相较发育;河流经历了低弯度-宽河床到高弯度-窄河床,再到中弯度-宽河床的演化,流向则由南北向逐渐演变为北东-南西向。研究结果可为利用地震资料识别曲流河的研究提供借鉴和指导。

For exploring the regional distribution of continental reservoirs characterized by deep burial depth,intense compaction,high diagenesis,and tight reservoir pore space,the seismic sedimentology was analyzed in the Lower Jurassic strata in the hinterland of the Junggar Basin utilizing the sequence stratigraphy and the instantaneous phase,root mean square amplitude and frequency decomposition attributes extracted from flattened seismic data volume.Three sequences are identified,including SQ1,SQ2 and SQ3.From SQ1 to the transgressive systems tract of SQ2,sequences are dominated by fluvial sedimentary,while the highstand systems tract of SQ2 to SQ3 were dominated by deltaic sedimentary.The seismic attribute analysis exhibits consistent results which channels are recognizable and reliable.They are single-channel configurations to oxbow lakes,crevasse splay,and other fluvial microfacies during their migration and evolution.Rivers evolves from low curvature and wide riverbeds to high curvature and narrow riverbeds,before settling into medium-curvature and wide riverbeds.Additionally,there is a gradual shift in flow direction from south-north to northeast-southwest.The results can provide reference and guidance for utilizing seismic data to identify meandering rivers.