Dynamic Response of a Fluid-filled 3-D Crack and its Application to Characterization of Geothermal Reservoir Cracks

充液三维裂纹的动态响应及其在地热储层裂纹表征中的应用

基本信息

批准号：
10650070
负责人：
HAYASHI Kazuo
金额：
$ 1.34万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10650070/
关键词：
Geothermal Energy HDR Geothermal Reservoir Crack Crack Characterization AE Elastic Wave

项目摘要

The dynamic response of a fluid-filled penny shaped crack, which was a typical example of 3-D cracks, was analyzed in detail in the framework of the theory of elasto-dynamics. It was revealed that the response was divided into tree types (Type I, II and III). Type I is the group that does not have any clear peaks in the power spectrum of the oscillation of the crack surface, and Type III is the group that has very clear peaks of fundamental modes in the power spectrum. Type II is in between Type I and Type III. Type III appears under the condition that attenuation of the wave traveling along the crack surfaces is weak and thus standing wave can be easily formed due to the reflection of the elastic wave at the crack periphery. Since Type III is far more informative than the other two and thus is preferable for the estimation of the crack parameters, it can be recommended that the reservoir pressure should be kept as higher as possible during the field experiments of active acoustic techniques.A new method is proposed for estimating the crack size, aperture and interfacial stiffness which is caused due to the asperity contact between the two crack surfaces. The method compares the frequencies of the fundamental modes of the standing wave, that are theoretically determined by the analyses just mentioned above, with the peak frequencies of the elastic waves observed during the field experiments such as hydraulic fracturing. The method was successfully applied to the field data obtained during hydraulic fracturing conducted in Hijiori and Ogachi HDR/HWR fields. Crack size and aperture in Hijiori field were estimated to be 5-11m and 1-44mm, respectively. Those in the Ogachi field are 4-28n and 10-22mm.

充液硬币形裂纹是三维裂纹的典型例子，在弹性动力学理论框架下对其动态响应进行了详细分析。据透露，反应分为树型（I型、II型和III型）。类型I是在裂纹表面振荡的功率谱中没有任何明显峰值的组，类型III是在功率谱中具有非常清晰的基模峰值的组。 II型介于I型和III型之间。 Ⅲ型出现在波沿裂纹表面传播的衰减较弱、由于弹性波在裂纹周边的反射而容易形成驻波的情况下。由于III型比其他两种信息丰富，因此更适合裂缝参数的估计，因此建议在主动声波技术的现场实验过程中，应尽可能保持储层压力较高。提出用于估计由于两个裂纹表面之间的粗糙接触而引起的裂纹尺寸、孔径和界面刚度。该方法将通过上述分析理论上确定的驻波基模频率与在水力压裂等现场实验中观察到的弹性波峰值频率进行比较。该方法已成功应用于 Hijiori 和 Ogachi HDR/HWR 油田水力压裂过程中获得的现场数据。 Hijiori 油田的裂缝尺寸和孔径估计分别为 5-11m 和 1-44mm。 Ogachi领域的有4-28n和10-22mm。