Exercise 5
A production well was designed to yield 2,000 m3/d from a 40 m thick confined gravel‑rich aquifer. The well was 40 cm in diameter and screened over 35 m. Once the well was completed, a step test was conducted by pumping the well at 1,400 m3/d, 1,790 m3/d and then 2,520 m3/d for a total of 90 minutes with each step lasting 30 min. The time‑drawdown data and a semi‑log plot of the time‑drawdown data are presented here.
Step‑drawdown test data for a production well. a) Time‑drawdown data for three steps. b) Plot of the log of time versus drawdown.
An Excel® data base of the time‑drawdown data is available on the web page for this book↗.
- Calculate the value of C and B for this system. Compute the well loss expected when pumping the well at 2,000 m3/d.
- Estimate the total drawdown after pumping the well for 30 min at 2,000 m3/d.
- Estimate transmissivity using the first 30 minutes of time‑drawdown data (step 1) (use the Cooper‑Jacob method).