Drilling Fluids: Well Rehabilitation an Option for California Drought
Over this past year, California has experienced one of the worst droughts on record with attention focused on the upcoming irrigation season and what effect it will have on reservoirs and groundwater aquifers. Recently, the areas most affected by the drought have received much needed rain and snow, but from all indications, it will fall short of the large quantities of water needed to sustain the 2014 growing season.
With groundwater levels dropping and reservoirs being depleted, farmers and ranchers are taking action to ensure they will have the water needed for the upcoming irrigation season. For some, it is just a matter of setting the pumps deeper with a possible bowl/impeller change, which can greatly increase the overall pumping costs. With others, we are finding well capacities have dropped off considerably from when they were built—some as much as 70 percent. For these irrigators, well rehabilitation is proving to be the most cost-effective way to manage their watering needs.
Steve Beymer of Beymer Well & Pump Service out of Colusa, Calif., was contracted to service some irrigation wells for a large grower near Dixon, Calif. The first well worked on was built in the early 90s to a depth of 1,025 feet, with 16-foot casing set to 348 feet and 14-foot casing set from 348 feet to 1,025 feet. Static water level was around 40 feet when the well was built and measures 48 feet today. The pump was set at 180 feet and was breaking suction at 1,700 gpm.
The pump was pulled and inspected, and the well was videoed to see what condition the casing and perforated area was in. The video showed excessive mineral encrustation built up on the perforations, which was also evident on the column pipe and shaft tube that was pulled.
We evaluated what would be needed to chemically treat the well and what mechanical means of agitation would be sufficient to rejuvenate the well. Well capacity and the amount of perforated area was calculated, and it was decided to use a NSF/ANSI Standard 60-certified, dry-penetrating acid such as CETCO DPA.
The well was brushed and cleaned of excess mineral deposits prior to adding the acid. A special dispersing chamber was built to hold the acid, which was placed at specific depths throughout the well to ensure the product was dispersed in the perforated areas at the same time the well was being brushed and swabbed. After two days of adding chemicals and working the well, a pump was set to remove the treated water until the pH returned to the natural pH of 6.8.
The pump that had been pulled was inspected, cleaned and reinstalled back to 180 feet. Test pumping results show the well is now producing 2,600 gpm with a drawdown to 128 feet, which is more than a 150 percent increase in the gpm per foot of drawdown. The results were so favorable that the grower is looking to have two other wells rehabilitated.
Well rehabilitation results like this are often attainable. They offer a good reason for contractors to explore their options before the added expenses of chasing the water to deeper depths, which greatly increases the pumping costs.