致密砂岩油“甜点”预测技术研究——以渭北油田延长组长3油层为例

The research of "sweet spot" prediction technologyfor tight sandstone reservoir——a case study of Chang 3 reservoir of Yanchangformation in Weibei Oilfield

渭北油田延长组长3油层属于致密砂岩油,储层为辨状河三角洲前缘水下分流河道砂体,砂体厚度薄且横向变化快.地质研究和动态分析表明,宽河道及河道汇聚部位,砂体厚度大,储层物性好,含油饱和度高,油井产量相对较高,是该油田的"甜点"区.由于油藏埋藏浅且地表条件复杂,地震资料分辨率低,河道砂体识别困难;地震振幅属性与砂体厚度对应关系弱。利用常规属性识别河道精度低.本文主要介绍应用谱反演技术进行地震资料处理,有效提高了地震分辨率,处理后的地震资料能够满足厚度小于λ/4的薄砂体识别;通过井震标定、地震正演模拟,总结砂体地震波形特征模式,采用地震波形结构法追踪砂体顶底反射,砂体识别精度大大提高,在密井网区识别砂体与钻井吻合率达90%以上;结合地质研究和动态分析成果,在开发区WB2井区外围优选出三个"甜点"区,是油田下一步开发和产量接替的有利阵地.

Chang3 reservoir of Yanchang Formation in Weibei Oilfield is a tight sandstone oil reservoir. As the reservoir is subaqueous distributary channel sandstone of braided river delta front,the thickness of sandstone is thin and lateral changes quickly. Geology study and dynamic production analysis shows that the broad parts of channel or places, where rivers come together, is oilfield^s ＂sweet spot＂, with thick sandstone, good physical property, high oil saturation, and high oil production. As the reservoirs are shallow and the surface condition isvery complex, it＇s difficult to identify sand bodies. And there is no corresponding relation between seismic amplitude properties and thickness of sandstone, so identifying rivers with regular properties has low precision. This paper mainly introduce using spectrum inversion technology to enhance the resolution of seismic data effectively, and the seismic data processed can fulfille identifying sand bodies, whose thickness is less than a quarter wavelength. According to well-seismic calibration and seismic forward simulation, We summarize the seismic waveform structure patterns of the channel sand bodies, and trace top and bottom reflection of them. The precision of sand body recognition is improved evidently, over 90%o in crowd-well area. Base on the results of geology research and dynamic analysis, three ＂sweet spots＂ areselected, and they are the oilfield＇s future production and reserves bases.