在油田开发过程中,同一时期沉积的小层砂体,即单砂体,是油气开发的基本单元,也是储集层沉积旋回研究的主体.小层的划分和对比多以地层中出现的砂体为参照,而砂体在空间的分布通常是变化的,这就增加了小层划分的不确定性.本文采用自然伽马测井曲线,应用滑移窗频谱分析技术,通过鄯善油田多口井的对比分析,在三间房组S3砂层组识别出了6个旋回界面,5个高频旋回.旋回界面的出现与旋回波长的频谱峰特征突变界面相对应,而旋回波长受沉积物沉积速率的控制,与地层中岩性的变化以及砂体的发育没有直接关系,这解决了以岩性为标志划分油层的诸多问题.旋回的厚度在几米至十几米之间,与小层的沉积旋回级别十分接近,而且由沉积速率突变识别出的旋回界面在区域内具有等时性,划分出的高频旋回也可进行横向上的对比,可作为油田小层划分与对比的重要地质参数和依据.

In an oilfield, the sublayers, sedimented at the same time, are the elementary units of its oil/gas development, as well as the main body of the sedimentary cycles of the reservoir bed. In the classification and correlation of sublayers, a sand body in the reservoir is usually taken as the reference. But the distribution of sand bodies in a strata space is often variable, which increases the uncertainty of the classification of sublayers. In this paper, the natural GR curves are used and the method of the evolutive spectral analysis is applied. Through the comparative analysis of several wells in Shanshan oil field, 6 cycle boundaries and 5 high-frequency cycles are identified in the S3 Sand Member of Sanjianfang Formation. The appearance of cycle boundaries is consistent with the abrupt interface of the cyclic wavelength peak in the frequency spectrum. The cyclic wavelength is found to be controlled by the sedimentation rate, but has not direct relation with the lithological change and the appearance of the sandbody. So this method can be used to deal with the classification of oil layers marked by lithology. The thicknesses of these cycles range between several meters and ten or more meters. They are very close to the cycle scale of a sublayer, and these cycle boundaries detected by an abrupt change of the sedimentation rate are isochronous in the regional geologic domain. These high-frequency cycles can also be laterally compared and be considered as an important geologic parameter and a criterion in the classification and the correlation of sublayers in the oilfield development.