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随着近几年随钻声波测井技术的广泛应用,在实际应用过程中遇到过各种不同类型的地层和钻井环境。其中对随钻声波测井的一个挑战就是在深水油藏钻探中经常遇到的埋藏浅、未压实的慢速地层。通过分析这种地层环境下的声波现象,我们指明一种在3-4KHz范围内进行的低频测量方法。在此频率范围内的纵波有很好的信噪比,甚至在有钻井噪音的情况下数据质量也很好。但是,波通常有衰减和频散特性,频散的程度取决于地层的软度(泊松比)和可能的地层速度的径向变化。油田数据实例阐明了应用上述方法能在未压实慢地层得到可靠的纵波慢度。
With the wide application of LWD logging technology in recent years, various types of formation and drilling environment have been encountered in the practical application. One of the challenges for LWD acoustic logging is the shallow burial, uncompacted, slow formations commonly encountered in deepwater drilling. By analyzing the acoustic phenomena in this formation environment, we indicate a low-frequency measurement method in the 3-4 KHz range. Longitudinal waves in this frequency range have good signal-to-noise ratios, and the data quality is good even with drilling noise. However, waves usually have attenuation and dispersion characteristics, and the degree of dispersion depends on the softness (Poisson’s ratio) of the formation and the possible radial variations in formation velocity. The field data examples illustrate the use of the above method to obtain reliable compressional slowness in uncompacted slow formations.