成像测井资料在湖盆沉积研究中的应用

Application of imaging logs in studying lake basin sedimentations

湖盆沉积砂体规模小,分布不稳定,非均质性强,在研究过程中,特别需要运用具有高分辨率、高覆盖率、高直观性特点的成像测井资料。讨论了成像测井资料在湖盆沉积研究中的主要应用:①基于成像测井资料分析常规测井曲线形态对微相分析的可靠性,钟型、箱型曲线代表正韵律的可靠性很好,卵型曲线代表正韵律的可靠性较差,漏斗型曲线并不完全代表反韵律。②识别指相标志。除岩石的颜色外,大部分指相标志都可通过成像测井资料获取。③判断层段的砂体骨架主体。例如在H油田某构造沙三段辫状三角洲前缘亚相的沉积中,根据成像测井资料和常规测井曲线分析沉积韵律,结果是正韵律的数量及厚度远远大于反韵律,从而判断出该层段的砂体骨架主体是水下分流河道砂体,而不是河口坝砂体。④用经过刻度的成像测井资料反映的沉积特征修正地质录井剖面,不仅可以准确识别湖盆沉积的岩性、岩石组合和沉积序列,还可以修正复杂地质层段地质录井资料的失误,恢复正确的岩性剖面及沉积环境。

The sand bodies in lake basins are of small size, irregular distribution and strong heterogeneity, and the imaging logs with high resolution, large coverage and fine visualizability are required to study such reservoirs. The main applications of imaging logs in the study of lake basin sedimentations include the following. The imaging logs were used to verify the reliability of rhythmicity indicated by the shapes of conventional logs, which shows that it is reliable to use the bell-shaped and box-shaped logs to indicate the positive rhythm, while the reliability of using the egg-shaped logs to represent the positive rhythm is not so good, and the funnel-shaped logs do not necessarily correspond to the negative rhythm. The imaging logs can be employed to identify facies marker, most of the facies markers can be identified by using imaging logs except for the colors of rocks. The imaging logs can be applied in determining sand body frames, in the rocks of the subfacies of the braided river delta front in H Oilfield, the analysis based on the imaging and conventional logs shows that the number and thickness of the positive rhythms are much bigger than that of the negative rhythms, leading to the conclusion that the main sand bodies are of the underwater distributary channel, not of mouth bar. Sedimentary characteristics from the calibrated imaging logs can also be used to accurately identify lithology, rock combination, and sedimentary sequences, and correct the cutting logs in complex formations, hence recover the correct lithological profile and sedimentary environment.