Specification of borehole mode contributes to frequency domain acoustic logs

用现场资料验证了频率域斯通利波测井探测地层边界的能力。斯通利波的主频与地层性质密切相关。在东八幡台地热田EE-4井中，频率域斯通利波测井探测到的地层边界与熔接度和岩性测井非常吻合，提出了一种新技术，可以探测围岩弹性性质变化很大的井中的薄渗透性裂缝。该方法利用不同频率的斯通利波振幅测井。用该技术探测的渗透性裂缝位置与全井增压声波测井结果一致，并对斯通利波透射系数出现的超调及其振荡进行了研究。超调量和超调量的振荡是由于井眼回流引起的 关于我们 从渗透性断裂带流出的流体。回流波的振荡特征与反射波相似，但回流波的振幅大于反射波。因此，透射系数出现振荡的周期与渗透性裂隙带的厚度有关。回流波的详细模拟对于开发渗透性裂缝带的新表征方法具有重要意义，这些实例表明，频率域斯通利波测井可以作为一种有效的地层边界和渗透性裂缝检测方法。所提出的技术不需要波源谱的知识。只需要不同频率的多个斯通利波振幅测井。因此，所提出的技术不仅适用于用宽带测井工具获得的测井数据，而且适用于使用变频测井工具，尽管在后一种情况下需要在不同频率下重复测量。少

The ability of the frequency-domain Stoneley wave log to detect formation boundaries have been tested with field data. The dominant frequencies of Stoneley waves are highly dependent on formation properties. Formation boundaries detected from the frequency-domain Stoneley wave logs are in excellent agreement with the logs of degree of welding and lithology in the well EE-4 of the Higashi-Hachimantai geothermal field.And, a new technique to detect thin permeable fractures in a well in which the elastic properties of the surrounding rock vary widely has been proposed. The method utilizes several Stoneley wave amplitude logs at different frequencies. The location of a permeable fracture detected with this technique agrees with the result of acoustic logging with full well-bore pressurization.In addition, overshoot and its oscillation appearing on the transmission coefficient of Stoneley wave have been investigated. The overshoot and its oscillation are attributable to backflow of borehole … More fluid from the permeable fracture zone. The characteristic of oscillation in the backflow wave is similar to the refection wave, though the magnitude of the backflow wave is larger than that of refection wave. Therefore, the period of oscillation appearing on transmission coefficient is concerned with the thickness of a permeable fracture zone. The detailed modelling of backflow wave is important for developing a new characterization method of the permeable fracture zone.These examples demonstrate that the frequency-domain Stoneley wave log can be used as an effective method for detection of formation boundaries and permeable fractures. The proposed technique does not require knowledge of the wave source spectrum. Only multiple Stoneley amplitude logs at different frequencies are required. The proposed technique is therefore applicable not only to logging data obtained with a broad-band logging tool, but also to the use of a variable-frequency logging tool, although in the latter case repeated measurements at different frequencies are required. Less