Establishment of Laboratory Hydraulic Tests for Saturated and Unsaturated Low-permeability Rocks

阐明了用常规实验室方法测试低渗透地质材料存在的主要问题。一个新的和多功能的实验室系统的设计，可以实现任何三种测试方法，恒定的头，流量泵和瞬态脉冲测试，同时保持相对较低的水力梯度和受试件高围压和孔隙压力，从而模拟在现场条件下在很大的深度。为了检验这一新的实验室系统的能力，还对白滨砂岩和稻田花岗岩进行了一系列交叉检查渗透性试验。主要结论如下：（1）由三种互补的实验室方法得到的渗透率在相同数量级上变化基本一致。这些差异可能反映了在脉冲测试期间的非常早期测量液压的实质性变化所产生的误差。也可能与V有关。 ...更多信息 非常小的管道泄漏或影响长期测试响应的轻微温度变化。(2)恒定水头和恒定流速试验的试验持续时间大致相同，所得渗透率值也大致相同。由于渗透率的“真实的”或“参考”值是未知的，我们无法评估哪种技术是最好的。但是，通过对不同测试方法的比较和结果的检验，可以提高低渗试件测试的准确性，并取得一致的结果。(3)在恒定流速测试过程中获得的瞬态相数据的严格的理论分析，允许测试时间显着缩短，而不会牺牲精度估计的渗透性和特定的存储的测试样本。(4)根据ASTM标准（D5084），当测试具有非常低的水力传导率（小于约1 × 10- 9 m/s）的试样时，建议使用小于30的水力梯度。在此条件下成功地进行了一系列交叉检查渗透率试验。少

We clarified some major problems in using conventional laboratory methods for testing low permeability geological materials. A new and versatile laboratory system is devised that can implement any of the three test methods, the constant-head, flow-pump and transient-pulse tests, while maintaining relatively low hydraulic gradients and subjecting a specimen to high confining pressures and pore pressures, thereby simulating in situ conditions at great depths. To exam the capabilities of this new laboratory system, a series of cross-check permeability tests is also performed on Shirahama sandstone and Inada granite. The major conclusions drawn from this research are as follows:(1) The permeabilities derived from the three complementary laboratory methods are in general agreement with variations in the same order. These differences may reflect the errors arising from measuring substantial changes in hydraulic pressure at very early times during the pulse test. They may also be related to v … More ery small plumbing leaks or slight temperature variations that affect long-term test response.(2) The test durations for the constant-head and the constant flow-rate tests are roughly the same and so are the resulting permeability values. Since a "real" or "reference" value for permeability is unknown, we cannot assess which technique is the best. However, further comparison among techniques and examination of the results does increase the accuracy of testing low-permeability specimen and achieve consistent results.(3) The rigorous theoretical analysis of the transient-phase data obtained during a constant flow-rate test permits the test duration to be significantly shortened without sacrificing accuracy in estimating both the permeability and the specific storage of a test specimen.(4) According to the ASTM standards (D5084), it is recommended to use hydraulic gradient less than 30 when testing specimens having very low hydraulic conductivities (less than about 1 x 10-9m/s). A series of cross-check permeability tests were successfully performed under this conditions. Less