基于成分指示因子的复杂岩相识别以南海宝岛凹陷深水深层低渗气藏为例

    Identification of complex lithofacies based on compositional indicators:a case study of deep-water low-permeability gas reservoir in Baodao Sag, South China Sea

    • 摘要: 针对海上深层低渗砂岩储层岩性复杂、有利储层难以识别的问题,基于岩石激光粒度分析、薄片鉴定对本区复杂岩性进行岩相划分。通过分析岩相与测井曲线间的响应关系,筛选能识别低渗储层岩石相的敏感测井曲线,并利用主成分分析方法,构建了能准确识别3类岩石相的成分因子曲线。研究结果表明:低渗储层岩性复杂多变,从粉砂岩到含砾中、粗砂岩均有分布;根据粒度均值可将本区岩性划分为3种岩石相,分别为相对粗粒岩石相(粒度均值>0.1 mm)、相对细粒岩石相(粒度均值介于0.062 5~0.1 mm)和极细-泥岩相(粒径均值<0.062 5 mm),其中,相对粗粒岩石相储层渗透性最好;构建的岩性成分指示因子较常规单一测井曲线的岩相识别准确率明显提高,所建立的岩相识别方法能更好地指导研究区水平井的入砂位置,对研究区低渗气藏的开发具有重要意义。

       

      Abstract: Aiming at the problem of complex lithology of deep offshore low-permeability sandstone reservoirs and difficulty in identifying favorable reservoirs, the complex lithology in the area was classified based on lithological laser particle size analysis and thin section identification. Through the analysis of the relationship between lithofacies and well logging curves, the sensitive well logging curves that can identify the lithofacies of the low-permeability reservoir were selected. By utilizing the principle of principal component analysis, component factor curves that can accurately identify three types of lithofacies were constructed. Results show that the lithology of the low-permeability reservoir is complex and variable, ranging from siltstone to gravelly medium and coarse sandstone. In the median particle size, the lithology in the lithofacies of this area could be divided into three types, i.e., coarse-grained lithofacies (median particle size (Ms) >0.1 mm), fine-grained lithofacies (Ms 0.1–0.0625 mm), and very fine-mudstone lithofacies (Ms <0.0625 mm). The coarse-grained lithofacies is the relatively high-quality lithofacies zone. In addition, lithological component indicator factors were constructed with which the accuracy of the lithofacies identification was improved significantly compared to the conventional methods using single well logging curve. The lithofacies identification method we established could better guide the sand entry position of horizontal well in the study area, which has important significance for the development of the low-permeability reservoir in the study area.

       

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