西湖凹陷平湖斜坡带平湖组煤系地层储层逐级预测

    Progressive prediction of coal-measure reservoirs in the Pinghu Formation, Pinghu Slope Belt, Xihu Sag

    • 摘要: 为了识别薄煤层影响下的含油气砂岩,综合钻井、地震等资料开展地质认识驱动下砂体富集区识别→复合砂体刻画→单砂体表征的储层逐级预测研究。首先,基于研究区坡槽复合构造背景,总结坡折控砂模式,挖掘梯度张量、倾角、曲率等结构类地震属性优势,开展挠曲坡折精细识别,坡折带与地貌低势区相叠合指示有利砂体富集区。然后,在砂体富集区内,通过“地震尺度煤层识别、过滤、去煤”方法处理,得到弱化煤层影响的叠前地震数据,基于该资料再开展叠前反演工作,有效消除反演结果中的煤层假象,实现复合砂体刻画。最后,在复合砂体约束之下利用多元井震资料信息优势,针对性开展复合砂体内部的单砂体边界刻画,提出“反演识砂,三瞬(瞬时频率、瞬时相位、瞬时振幅)定边”研究思路,实现了单砂体精细表征。该方法有效解决了西湖凹陷煤系地层储层预测可靠性差、分辨率低的难题,将储层预测精度提升23%,对研究区的构造-岩性油气藏滚动挖潜意义重大。

       

      Abstract: To identify hydrocarbon-bearing sandstones under the influence of thin coal seams, an integrated study using drilling and seismic data was conducted to perform a progressive reservoir prediction workflow, driven by geological understanding, which includes: identification of sand-rich zones → delineation of composite sand bodies → characterization of individual sand bodies. First, based on the slope-trough composite structural background of the study area, the slope-break controlled sand deposition model was summarized. Leveraging the advantages of structural seismic attributes such as gradient tensor, dip, and curvature, fine identification of flexural slope breaks was carried out. The overlap of slope-break zones and low-potential geomorphic areas indicated favorable sand-rich zones. Subsequently, within these sand-rich zones, pre-stack seismic data with reduced coal influence were obtained through a method involving "seismic-scale coal seam identification, filtering, and coal removal." Pre-stack inversion based on this processed data effectively eliminated coal-induced artifacts in the inversion results, achieving accurate delineation of composite sand bodies. Finally, constrained by the composite sand bodies, the advantages of multi-attribute well and seismic data were utilized to delineate the boundaries of individual sand bodies within the composite sand bodies. A research strategy of "inversion for sand identification, instantaneous attributes (frequency, phase, amplitude) for boundary definition" was proposed, enabling detailed characterization of individual sand bodies. This method effectively addresses the challenges of poor reliability and low resolution in reservoir prediction within coal-bearing strata of the Xihu Sag, improving prediction accuracy by 23%. It holds significant importance for the progressive exploration and potential tapping of structural-lithological reservoirs in the study area.

       

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