地震沉积学在坳陷湖盆滩坝砂体预测中的应用——以酒西盆地Y区块间泉子段为例

Application of seismic sedimentology to prediction of beach and bar sand bodies in lacustrine basin: a case study of Jianquanzi member in Y block, Jiuxi Basin

滩坝砂体是我国陆相湖盆重要的勘探领域之一,由于该类砂体具有砂泥薄互层的特征,储层预测难度较大。针对薄层滩坝砂体预测难题,运用90°相位转换、地层切片等地震沉积学技术,对酒西盆地Y区块间泉子段滩坝砂体进行了识别和描述,结合岩心、录井和测井等资料对地层切片进行了地质解释,从成因、岩性、沉积厚度及地球物理响应特征等方面总结了滩坝砂体的识别标志,并探讨了滩坝砂体分布规律和形成主控因素。研究区滩坝砂体平面上位于辫状河三角洲之间的湖湾区,呈多排条带状平行于湖岸线分布,垂向上主要发育于五级湖平面下降旋回L3油层组。湖岸线频繁迁移、沉积古地形平缓及物源供给相对充足是研究区大面积滩坝砂体形成的主要控制因素。研究表明,地震沉积学相关技术是解决薄层储层预测的有效手段,指导了酒西盆地Y区块岩性油气藏的精细勘探与开发,并可为与其具有相似地质背景地区的储层预测提供参考。

The beach bar sand bodies have become an important exploration target in lacustrine basins of China. The prediction of beach bar sand bodies is difficult due to its thin bed characters. Under the guidance of seismic sedimentary theory, the techniques of 90~ phase shift and stratal slicing were used to identify and characterize the distribution of beach bar sand bodies of Jianquanzi member in Y block of Jiuxi Basin. Based on the comprehensive analysis of core, lithology and logging data, stratal slices were interpreted. The identification signs of beach bar sand bodies were summed up from the aspects of origin, lithology, sedimentary thickness and geophysical response characteristics, and the distribution rule and controlling factors of beach bar sand bodies were discussed. The beach bar sand bodies were developed in lake-bays between braided deltas, and vertically in L3 reservoir group of descending half cycle of fifth-order cycle, and were characterized by thin and multi-row distribution parallel to the shore line. The frequent change of lake level, gentle sedimentary palaeotopography and sufficient supply of source rocks are the main controlling factors for the large area distribution of beach bar sand bodies. The research results show that seismic sedimentology technology is an effective means to predict thin reservoirs and could advantageously guide the fine lithologic reservoir exploration and development. This research could provide reference for the reservoir prediction in other similar areas.