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Characterization of a Geothermal Reservoir Crack Based on the Analysis of Dynamic Response of a Crack Filled with Fluid

基于充液裂缝动态响应分析的地热储层裂缝表征

基本信息

批准号：
08650086
负责人：
HAYASHI Kazuo
金额：
$ 1.22万
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：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08650086/
关键词：
Geothermal Energy HDR Geothermal Reservoir Crack Characterization of Crack AE Elastic Wave

项目摘要

The objective of the present project is the establishment of a method for characterizing the geometrical and physical characteristics of a fluid-filled geothermal reservoir crack. Firstly, we have proposed a model for a fluid-filled crack within an elastic medium with permeation of fluid. The upper and lower surfaces are in partial contact to each other, thus there exists interface stiffness along the crack, and also the fluid viscosity is taken into account. It has been revealed that, in the case that the partial contact is absent, the eigen angular frequencies are highly dependent on the aspect ratio (the ratio between the crack size and aperture), when the viscosity and permeability are small. However, in the case that the partial contact is present, the eigen angular frequencies are highly dependent on the interfacial stiffness. When the permeability is large as that of a formation in a usual geothermal field, then the effects of the permeability and viscosity become stronger. In order to get clear understanding of the effects of permeability and fluid viscosity, we have analyzed the case that the rock is rigid and have found that there exists an optimum value of fluid viscosity which gives the largest pressure response. The optimum value of fluid viscosity is mostly determined by the permeability of the formation. Inversely speaking, it is possible to get the maximum pressure response by choosing the fluid with the optimum value of viscosity depending on the formation permeability. Finally, on the basis of the results of the analysis, we have set up the inverse problem to estimate the aspect ratio of the crack, the initial crack aperture and the interfacial stiffness by using a newly introduced objective function.

本项目的目标是建立一种方法，用于表征充满流体的地热储层裂缝的几何和物理特性。首先，我们提出了一个模型的流体渗透的弹性介质中的充满流体的裂纹。由于上、下表面部分接触，因此沿裂纹存在沿着界面刚度，并考虑了流体粘性。它已被揭示，在部分接触是不存在的情况下，本征角频率是高度依赖于纵横比（裂纹尺寸和孔径之间的比率），当粘度和渗透率小。然而，在存在部分接触的情况下，本征角频率高度依赖于界面刚度。当地层渗透率达到常规地热田地层渗透率时，渗透率和粘度的影响更大。为了更清楚地了解渗透率和流体粘度的影响，我们分析了岩石是刚性的情况，并发现存在一个最佳的流体粘度值，使最大的压力响应。流体粘度的最佳值主要取决于地层的渗透率。因此，根据地层渗透率的不同，选择具有最佳粘度值的流体，可以获得最大的压力响应。最后，在分析结果的基础上，通过引入新的目标函数，建立了估算裂纹纵横比、初始裂纹孔径和界面刚度的反问题。