地震属性预测西湖凹陷N构造“甜点”

Application of Seismic Attributes to Predict “Sweet-Spot” in N-Structure of Xihu Sag

东海盆地西湖凹陷N构造花港组主要的天然气储层为致密砂岩,寻找相对高孔、高渗的"甜点"是该区勘探的关键。分析岩石物理特征,优选孔隙度、渗透率等测井参数,利用加权融合方法计算每口井的"甜点"因子,提取不同角道集分频数据体的多种属性,与"甜点"因子进行相关分析,将相关性高的地震属性进行加权融合得到"甜点"预测值,从而建立"甜点"储层—井—地震之间的联系。研究表明,绝对振幅组合、弧长等属性与井"甜点"因子相关性高,属性融合得到的甜点预测值可以精确描述N构造"甜点"的空间展布,结合沉积相分析,"甜点"分布于N构造中南部的分流河道砂体内。该研究可有效地在致密砂岩中寻找"甜点",对西湖凹陷其他构造的"甜点"研究具有借鉴意义。

The gas reservoir in Huagang Formation of N-Structure in Xihu Sag of East China Sea Basin is dominated by tight sandstone reservoir and the key exploration in this area is to identify 'sweet-spot' with relatively high porosity and permeability. The reservoir petrophysical properties are analyzed to optimize porosity,permeability and other logging parameters and weighting integration is used to calculate the 'sweep- spot'factor of each well. The multiple attributes of frequency-division data volumes in different angle gathers are extracted and used to perform correlation analysis with 'sweet-spot' factor. The seismic attributes with relatively high correlation are used to gain sweet-spot factor by weighting integration and a 'sweetspot' reservoir-well-seismic relation. Research demonstrates that absolute amplitude combination,arc length and other attributes show relatively high correlations with 'sweet-spot' factor. The spatial distribution of 'sweet-spot' in N-Structure can be accurately modeled by this sweet-spot prediction value from multi-attribute integration and the'sweet-spot' is located within the distributary channel sandbodies in the south-central part of N-Structure according to sedimentary analysis. This research could effectively identify 'sweet-spot' in tight sandstone and provide a reference for the 'sweet-spot' exploration in other structures of Xihu Sag.