The flow of homogeneous fluids through porous media: analogies with other physical problems

In well-test analysis, a diagnostic plot is a scatter plot of both drawdown and its logarithmic derivative versus time. It is usually plotted in log–log scale. The main advantages and limitations of the method are reviewed with the help of three hydrogeological field examples. Guidelines are provided for the selection of an appropriate conceptual model from a qualitative analysis of the log-derivative. It is shown how the noise on the drawdown measurements is amplified by the calculation of the derivative and it is proposed to sample the signal in order to minimize this effect. When the discharge rates are varying, or when recovery data have to be interpreted, the diagnostic plot can be used, provided that the data are pre-processed by a deconvolution technique. The effect of time shift errors is also discussed. All these examples show that diagnostic plots have some limitations but they are extremely helpful because they provide a unified approach for well-test interpretation and are applicable in a wide range of situations.

/pdf/understanding-diagnostic-plots-for-well-test-interpretation-259xaw3p2o.pdf

Understanding diagnostic plots for well-test interpretation

Perhaps because of the existence of a vast amount of literature, many hydrogeologists believe that well hydraulics is no longer at the frontier of our discipline. Well testing is well established both in theory and practice; its techniques have been applied for decades. However, despite more than 100 years of theoretical development, the plight of the field hydrogeologist is still not enviable (Williams 1985). Often, the data are ambiguous and the model identification is not unique (Al-Bemani et al. 2003). This matter of fact is seldom emphasized within the literature, which is dominated by the development of new theories, of new testing techniques, of new software and so on. This is understandable, brilliant papers are rarely reports of incomprehensible experiments. The aim of this essay is to try to subjectively answer the following questions: What has been accomplished? What has been the recent progress? How could this field evolve in the future?

/pdf/the-future-of-hydraulic-tests-1k94rlnsjs.pdf

The future of hydraulic tests

A.D. Sneyd

Papers

Seepage flow through homogeneous soil into a row of drain pipes

An improved method of least-squares parameter estimation with pumping-test data

Effect of drain depth and gap width on potential flow in homogeneous porous soil

Least-squares estimation of equation parameters for predicting drawdown from a single pumped well