莱州湾凹陷垦利油区沙三上亚段辫状河三角洲沉积特征表征

渤海湾盆地莱州湾凹陷垦利油区沙三上亚段是目前中深层油气勘探开发的重点主力含油层系。综合研究区沉积背景，以三维地震资料、岩心及测井资料为依托，结合地震沉积学研究，开展了垦利油区沙三上亚段辫状河三角洲沉积特征及演化规律研究。结果表明，莱州湾凹陷垦利油区沙三上亚段沉积期，发育以莱北低凸起、垦东凸起及潜在物源区潍北低凸起供源形成的辫状河三角洲沉积体系。研究区辫状河三角洲平原砂体以细—中砂岩为主，前缘砂体以粉—细砂岩为主，分选性中等较好。牵引流性质的沉积构造十分发育，多见生物扰动构造，反映三角洲前缘动荡的水体环境。顺物源方向发育斜交前积反射地震相，垂直物源方向识别出多期丘状反射地震相。综合古地貌、沉积特征及振幅属性切片，明确研究区沙三上亚段以北部物源莱北低凸起供源为主导，沉积中块及沉积东块为主体沉积区，莱北低凸起供源的三角洲呈后退趋势，其展布面积大（95~130 km2）。沉积西块及东块为多物源供给区，来自垦东凸起的三角洲前缘沉积逐渐萎缩，来自潍北低凸起的三角洲区前缘沉积逐渐向湖盆中央推进。上述沉积展布及演化规律为进一步精细勘探开发提供了沉积地质基础。

Geological and Geophysical Characterization of the SedimentaryFeatures on Braided River Delta in the Upper Member 3 of theShahejie Formation,Kenli Oilfield,Laizhouwan Sag

The upper Member 3 of the Shahejie Formation (E2s3U) in the KenLi (KL) Oilfield is the primary target strata for medium-deep oil and gas exploration in Laizhouwan Sag, Bohai Bay Basin. Integrating the analyses of sedimentary background, three-dimensional seismic, core, and well-logging data, using the seismic sedimentological technique, we studied on sedimentary characteristics and depositional evolution of the braided river delta formed during the E2s3U interval in KenLi Oilfield. The results show that braided river deltas developed in the study area received sediments from three source areas, namely Laibei Low Uplift, Kendong Uplift, and Weibei Low Uplift. The well-sorted sand bodies in the delta plain were mainly fine-medium sandstone; whereas the sand bodies in the delta front were fine sandstone and siltstone. Sedimentary structures were developed well under tractive currents. Additionally, wavy bedding and bioturbation structures are common, suggesting turbulent water conditions in the delta front environment. The oblique progradation reflections were developed along the source direction, and multi-unit mounded-shape seismic reflections were observed across the source direction. Comprehensive analyses of paleo-geomorphology, sedimentary characteristics, and amplitude attribute slices of strata reveal that the Laibei Low Uplift is the dominant source area, which provided abundant sediments to the depositional area. Middle and eastern districts of the sedimentary area were central depositional regions, where a large area of braided river delta deposits (95~130 km2) with landward-stepping was developed. Western and eastern districts of the sedimentary area were fed by multi source areas. The delta front from the Kendong Uplift gradually shrank, and the delta front from the Weibei Uplift gradually prograded basinward. Study on the sedimentary characteristics and evolution of depositional processes of the braided river delta systems will serve as a reference for reservoir prediction and oil exploration and development.