Analysis of Slope-Matching Methods for Aquifer Parameter Determination

Various methods for numerical determination of aquifer transmissivity and storage coefficients from a single observation well data have recently been proposed. Most of these methods involve reading the slope values from a table or providing an initial estimate for iterative solution. A different formulation of the slope-matching technique has been suggested in the field of petroleum engineering which obtains the parameter values without using any tables or iterative procedures. In this study we adopt a similar approach and compare the prediction of various techniques. The modification of the approach to include cases with time-varying parameters is examined. Numerical experiments are performed first on synthetic data to ascertain the relative accuracy of different slope evaluation techniques. It is shown that the slope of the drawdown with respect to the logarithm of time results in the most accurate prediction of aquifer parameters. The inaccuracy involved in application of the slope-matching methods to cases involving time-varying parameters is analyzed. The methods are then applied to some field data and the results are compared with published data. AH the methods are found to work reasonably well for the field application.