摘要
为了获得塔里木A区古近系地层中膏泥岩在声波测井20kHz频率下纵横波时差之间及与其他静力学参数之间的转换关系．开展了室内1000kHz高频声波测试。根据测试声波波速值、品质因子和频散方程外推20kHz频率的声波波速。2种频率下波速或声波时差对比分析表明：模拟地层条件下转换后的纵波时差（实验校正）与测井纵波时差更为接近；常温到85℃范围内相同净围压下波速和品质因子变化较小，波速变化可以忽略，品质因子变化范围为5％～7％；在不断增加净围压条件下，波速和品质因子都增加，且幅度显著；模拟地层条件下与常温、常压下相比，纵波波速增量为2．7％～8．4％，纵波品质因子增量为27％～58％，膏泥岩频散度为7.4％～24．4％，平均为15．12％，频散度较大。通过对频散方程变形得出了一种可直观表现本区膏泥岩在模拟地层条件下品质因子与波速降低幅度之间的表达式，同时根据膏泥岩品质因子影响因素．将该区古近系地层的膏泥岩纵波按由高到低划分为I，Ⅱ，Ⅲ共3个频散等级，最后探讨了频散效应在横波时差预测中的应用。结果表明：在1000kHz和20kHz频率下，利用纵波时差预测的横波时差在该区膏泥岩声波时差变化范围内，平均相对误差仅2％，误差整体随着石膏含量的增加而增大．这2种频率下纵横波时差拟合公式都可应用到横波时差预测（ft．0用测井纵波时差值进行预测）中，但由于膏泥岩频散度大，因而2种频率间声波时差值变化较大，应用时应进行频散校正。
In order to obtain the transformational relations between shear wave slowness time and compressional wave slowness time and other statics parameters of the gypsum mudstone of Paleogene in A area of Tarim Basin at 20 kHz, we conducted indoor 1 000 kHz high frequency acoustic wave test, and extrapolate the acoustic wave velocity at 20 kHz based on the tested acoustic wave velocity, quality factor and dispersion equation. The comparative analysis of the acousticwave or acoustic wave slowness time at these two kinds of frequencies shows that the compressional wave slowness time is closer to logging compressional wave slowness time value under simulated formation condition; the wave velocity and quality factor change slightly within 85 ℃, the changes of wave velocity can be ignored, and the quality factor ranges from 5% to 7%; both the wave velocity and quality factor increase with the increasing of net confining pressure; comparing with compressional under simulated formation conditions and atmospheric pressure, the compressional wave velocity increment is 2.7% to 8.4%, and the compressional wave quality factor increment is 27% to 58%, gypsum mudstone dispersion degree is 7.4% to 24.4% （average 15.12%）, with relatively large dispersion degree. By using the deformation of dispersion equation, we proposed an intuitive expression between quality factor and wave velocity decline of gypsum mudstone under simulated formation condition. According to the influencing factors of gypsum mudstone quality factor, the compressional wave of gypsum mudstone was divided into I, Ⅱ, Ⅲ three levels of dispersion from high to low, at last dispersion effect was discussed in the application of shear wave slowness time prediction. The results show that under the conditions of 1 000 kHz and 20 kHz frequency, the average relative error of shear wave slowness time predicted by compressional wave slowness time is only 2% within the variation range of gypsum mudstone acoustic time, and the error has the trend of increase with the increasing of gypsum content. The fitting formula of compressional wave slowness to shear wave slowness can be applied to the prediction of shear wave slowness under the two kinds of frequencies. Because the dispersion degree of gypsum mudstone is larger, and the acoustic slowness varies greatly under the two kinds of frequencies, so dispersion calibration should be applied in the actual application.
出处
《岩性油气藏》
CSCD
2014年第1期110-116,共7页
Lithologic Reservoirs
基金
国家"十二五"重大科技专项"缝洞型碳酸盐岩油藏高效酸压改造技术"(编号:2011ZX05014-006)资助
关键词
地层条件
膏泥岩
声波
波速频散
纵横波时差
品质因子
formation conditions
gypsum mudstone
acoustic wave
wave velocity dispersion
compressional wave slowness time and shear wave slowness time
quality factor
