三河北工区双复杂滩坝砂储层精细描述方法应用与效果

Fine characterization method for complex beach-bar reservoirs in Sanhebei,North Jiangsu Basin

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;(3)90°相移处理能直观地解释有利砂体;(4)将优势地震属性与T_(0)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 T_(0) structure map and seismic facies.The proposed characterization method is theoretically and practically significant for complex beach-bar reservoirs.