Examples of slug tests in textbooks: given interpretation and correct interpretation

ABSTRACT: When a slug test is performed in a monitoring well, the test data of the water column Z(t) versus time t may be analyzed using several methods. These use three types of graphs, which provide a clear diagnosis for the test data when used all together. According to experience, most test data contain a systematic error H0 on the water column data, which is due to five sources of error. According to experience, most plots of log Z(t) versus t yield an upward curvature, a minority give a downward curvature, and very few provide a straight line. The upward and downward curvatures correspond to positive and negative values of H0, whereas a straight line means no piezometric error. For this paper, 21 sets of slug test data found in textbooks were analyzed, using the three diagnostic graphs. For these textbook data, the plots of log Z(t) vs. t are either curved upward or straight, but no data set has the downward curvature. The optimization method easily found the H0 value in all cases, and the velocity graph for almost all sets. Therefore, the authors of textbooks have ignored the upward curvatures, and often have provided an incorrect interpretation for their examples.