三河北工区双复杂滩坝砂储层精细描述方法应用与效果

苏北盆地三河北滩坝砂储层具有“盖储叠合、厚度变化, 储层信号弱、岩性相变”的盖层、储层双复杂特点, 其精细描述较常规滩坝砂储层更为困难。为此, 首先对目标区开展井震标定分析, 明确阜二段3个砂组的主要地震特征, 根据其特点, 提出“提频+去屏蔽+90°相移”的研究思路与对策, 采用压缩感知方法进行拓频处理, 在此基础上利用多道匹配追踪方法进行去强屏蔽处理, 最后利用90°相移技术精细刻画砂体。模型测试与实际资料应用结果表明: ①针对变厚度的复杂盖层, 基于压缩感知反射系数稀疏反演的提频目标处理, 可以有效分离叠合的复合波; ②利用幅度可调制的多道匹配追踪方法, 能可控去除顶部强屏蔽层的部分能量, 使储层内砂组反射同相轴与厚度相一致; ③90°相移处理能直观地解释有利砂体; ④将优势地震属性与T₀构造图相融合, 并结合地震相分析, 可以较好地判识研究区滩坝砂体的分布区域。该方法对复杂滩坝砂储层砂体刻画具有理论研究与推广应用价值。

Beach-bar reservoirs in the Sanhebei area of the North Jiangsu Basin are complex for thickness-varying caprocks shielding the underlying lithofacies-varying reservoir with weak signals.Fine characterization of such reservoirs is more challenging than conventional beach-bar reservoirs.In this paper, well-seismic calibration was conducted for the area of interest to clarify the features of three sand zones in the second member of Funing Formation (Fu-2 Member).On this basis, an approach of frequency enhancement by compressed sensing+strong reflection deshielding by multi-trace matching pursuit+90° phase shift was proposed for sandstone prediction.The results of model tests and field data application are obtained in four aspects.First, the composite reflections from thickness-varying caprocks could be separated effectively using frequency enhancement through sparse reflectivity inversion based on compressed sensing.Second, using the amplitude-modulated multi-trace matching pursuit method, reflection energy from caprocks could be partially mitigated under a controlled manner, so that the reflection events of the sand zone in the reservoir are consistent with the thickness of the sand zone.Third, favorable sands can be visually interpreted after 90° phase shift.Fourth, the distribution of beach-bars in the study area can be well identified through combining dominant seismic attributes with T₀ structure map and seismic facies.The proposed characterization method is theoretically and practically significant for complex beach-bar reservoirs.