AQTESOLV has built-in tools to check the validity of analyses performed with the Cooper and Jacob method and to assist you with visual curve matching. First, you can superimpose on your plot the time when u is less than a critical value. Choose View>Options>Plots tab and check the option for Valid time for Cooper-Jacob approximation (Figure 1).
|Figure 1. Check option to display valid time for Cooper and Jacob solution.|
|Figure 2. Set critical value of u used to check validity of Cooper and Jacob approximation.|
|Figure 3. Cooper and Jacob method (blue line) matched to time-drawdown data from constant-rate pumping test (data from Todd 1980). Dashed vertical line indicates time when Cooper and Jacob approximation becomes valid.|
|Figure 4. Cooper and Jacob method (blue line) matched to drawdown data during period of infinite-acting radial flow when derivative reaches plateau (red line).|
Visit the AQTESOLV Knowledge Base to find more tips on the using the software. The AQTESOLV documentation also includes a number of examples illustrating the use of the Cooper and Jacob straight-line method.
We invite you to follow HydroSOLVE on LinkedIn and Google+!