地震沉积学研究方法在渤南洼陷沙三下9砂组中的应用

The Application of Seismic Sedimentology Research on the Lower Es_3x9 Sand-Body in Bonan Sag

摘要: 浊积岩油藏是济阳坳陷重要的油气储量阵地，勘探潜力巨大，由于其“单期砂体薄、垂向相叠置、边界难识别”的特点，导致该砂质沉积体分布隐蔽、识别困难，严重制约油气高效勘探开发。为解决浊积扇砂体识别难度大的问题，以渤南洼陷南部缓坡带义141-994井区沙三下9砂组为研究对象，在岩电及井震标定共同确定的等时地层格架约束下，将沙三下9砂组进一步细分为Es3_x9¹、Es_3x9²、Es_3x9³小层；综合运用正演模拟、Wheeler域等时切片、波形聚类等地球物理技术对目的层砂体进行精细解剖，明确沉积相带平面展布及沉积演化规律，并建立浊积扇沉积微相井震识别模板。研究中主要形成以下几点认识：① 地震剖面上浊积扇多发育于断层下降盘，其中，主水道砂体呈“双眼皮”弱反射，侧缘砂呈“单眼皮”中弱反射，水道间呈连续强反射特征；② 通过Wheeler域等时切片与频率域波形聚类属性相结合，能准确刻画岩性边界，反映河道展布特征；③ 9砂组横向呈东–西向迁移，纵向Es_3x9²小层连通性最好，断层为主要控藏因素。

Abstract: Turbidite is an important oil gas reserves field of Jiyang depression which has a great exploration potential. As the characteristic as “single sand-body is thin, with overlapped vertically with many others, and the boundaries are hard to identify”, the distribution of this kind of sandy sediments is concealed and hard to identify, leading to a serious constraint in efficient oil exploration. To solve the difficult issue in identifying the turbidite fan sand bodies, by taking the lower Es₃9 sand-body in the south gentle slope belt 141-994 of Bonan sag as a research object, in the limit of isochronal stratigraphy framework which is based on the lithology-electrify variations and well-seismic calibrate, the authors subdivide the lower Es_3x9 sand-body into three single layers: Es_3x9¹、Es_3x9² and Es_3x9³. With the comprehensive use of forward modelling, isochronous slice of Wheeler domain and waveform clustering, the sand-body in target horizon is precisely analyzed, and so that the evolving laws and distribution of sedimentary facies are clarified, then build a well-seismic identified template of turbidite fan. Following conclusions can be drawn from this research: ① according to the seismic section, it can be found that most turbidite fan bodies locate in the descending stage of the fault, and the main channel sand bodies show “double-fold eyelids” with weak reflections, the lateral sand bo-dies show “single-fold eyelid” with weaker reflections, and the inter-channel sand bodies show continuous strong reflections; ② by combining isochronous slice of Wheeler domain with waveform clustering properties of frequency domain, lithologic boundaries and the patterns of channel distribution are more explicit to depict; ③ Es3x9 sand-bodies are usually shifted in east-west horizon, Es_3x9² has best conjunction in vertical, and oil reservoirs are mainly prone to be affected by faults.