金属套管对钻孔波速测试的影响问题探讨

The Influence of Metal Casing on Drilling Wave Velocity Test

波速测试中,决定波速测试精度的关键在于判断弹性波到达的初至时刻。实际测试中往往存在各种各样的干扰,使得初至时刻难以判别,这是长期以来困扰从事波速测试技术人员的难点。其中预埋套管对波速测试的数据影响不仅仅体现在套管内的部分,套管以下的深部测试数据也会受到不同程度的影响。套管对深部数据的影响是如何形成的,套管长度、材质与数据受影响的深度之间存在什么关系,除套管本身的长度、材质以外,数据受影响的深度与其他因素有没有关系?为了解答这一系列问题,构建了一个简化的波速测试模型,从理论上进行了初步的分析探讨。最终推导出了沿套管传播的折射波对直达S波影响深度的简易计算公式;并对钻孔波速测试中套管的选材、套管长度的确定给出了指导意见。

The key to determining the accuracy of wave velocity test is to determine the first wave.Practical tests often have a variety of interference,making it difficult to determine the first wave,which has long been a difficult problem for technicians engaged in wave velocity testing.The influence of embedded casing on the data of wave velocity test is not only reflected in the casing part,but also the deep test data below the casing will be affected to some extent.How is the influence of casing on deep data formed？What is the relationship between casing length,material quality and the depth affected by data？Is the depth ofthe data affected related to other factors except for the length and material of the casing itself？In order to solve these problems,a simplified wave velocity test model is built,and a preliminary analysis is carried out in theory.Finally,a simple formula for calculating the influence depth of the refraction wave propagating along the tube to the depth of shear wave is derived,and the guiding opinions are given for the selection of the casing and the length of the casing in the testing of the borehole wave velocity.