基于地震沉积学方法的沉积相研究——以珠江口盆地番禺4洼古近系为例

Research on sedimentary facies based on seismic sedimentology: A case study of Paleogene Strata of Panyu 4 Sag in the Pearl River Mouth Basin

油气勘探与开发实践表明,在少井、无井及低分辨率地震资料的海域,利用地震沉积学的方法和技术,可有效建立高频层序地层格架,刻画沉积体系演化规律,这是陆相断陷湖盆地层—岩性油气藏勘探的有效手段。本研究以番禺4洼古近系文昌组为例,在地震沉积学理论指导下,基于高分辨率处理地震资料,在三级层序地层格架约束下,以体系域旋回为单位,结合单井的岩性资料,利用90°相位转换、地层切片及定量岩石物理分析技术,对珠江口盆地番禺4洼始新统文昌组开展了地震沉积学研究,划分了6个三级层序,建立了地层岩性与地震极性关系,并对已钻井开展岩石物理分析,最终在SQ2筛选不同时期切片,雕刻了文二段沉积时期,东、西两侧向湖盆推进的扇三角洲、近岸水下扇及辫状河三角洲的沉积体系展布和演化规律。

Through practices of litho-stratigraphic hydrocarbon exploration and development, the theory and technical methodof seismic sedimentology can be effectively applied to build high-frequency stratigraphic frame and study the variation ofdepositional system in terrestrial rifted lake basin. Here, we present our study on the Wenchang formation of Paleogene strata ofPY4 Sag using seismic sedimentology theory. Based on high-resolution processed seismic data and third-order sequence frame,system tract cycle is defined as a study unit. Combined with lithological data of drilled wells, six third-order sequences can berecognized, and the relationship between seismic polar and lithological attribute can be established by 90° phase-rotation, seismicslice and quantitative rock-physical technical. Key slices are chosen in SQ2 to reveal the depositional system variation of fandelta, nearshore subaqueous fan and braided river delta that prograde basinward from west and east of PY4 Sag.