Drilling Fluids: Chemical Contact Strategy Key to Well Rehabilitation
We have all been told at some point in our life that good things come to those who wait. In well rehabilitation projects, chemical contact time is one part of a successful program. This is an area that I always get questioned on when talking with contractors looking at a well rehabilitation project. When products are not given sufficient time to work, the results can be disappointing for the project. There are several aspects to consider when putting together an estimate and plan for the well owner. The ultimate decision is to rehabilitate their well or drill a new well.
This brush was made by a contractor from steel pipe and cable, but many companies also sell them. Source: CETCO Drilling Products
The well rehabilitation process begins with reviewing the detailed information from when the well was built and any work that has been done over the life of the well. Information such as the static water level and the specific capacity of the well in gallons per minute per foot of drawdown from when it was built, compared to what it is now, are very valuable in deciding what your next steps will be. If the water table has declined and the original well was not built deep enough, the only option may be drilling a new well. If the static water level is the same or near the same as at the time of construction, but the specific capacity has declined, well rehabilitation should be an option. Other indicators of the need for well rehab would be increased pumping costs, color changes in the water discharged from the well, or physical indicators of plugging in or on the drop pipe and pump. Taste, odor and debris in the water being pumped from the well when in use are also indicators of the need for well rehabilitation.
Well plugging begins as soon as the well is built and put into production. Well screen and formation plugging occur in many forms including physical plugging from the drilling fluids and native clays, as well as sand and silt that were not developed fully at the time of well construction. Mineral and biological plugging, as well as plugging from corrosion, can be treated with mechanical and chemical means.
Video inspection and recording of the well can be useful to help identify problem areas or any structural failures in the well. Time needed for proper well rehabilitation starts first with physical brushing of the inside of the well. Brushes for this are available from many companies. They can also be built by the contractor, such as the one in the picture made out of steel pipe and cable.
Once the inside of the casing and screen have been brushed, the material freed from the inside of the well can be bailed out before treating with well rehabilitation products for the problem being treated. Once well rehabilitation products have been introduced into the well, a combination of surging, swabbing, jetting or other type of agitation methods and contact time in the well are vitally important for a successful project. Typical recommended contact time of rehabilitation products in the well is 12 to 48 hours. Checking the pH of the water and rehabilitation products in the well at regular intervals is recommended to ensure that there is enough well rehabilitation products in the well.
After the well has been treated for the recommended time, fluid can be pumped or bailed from the well. Proper neutralization and disposal of the fluids removed needs to be in accordance with any local, state and federal requirements. After the well rehabilitation process has been completed, another video may be done to compare and confirm visual results of the work performed. Upon reinstalling the pumping equipment, the new specific capacity of the well should be checked. Contractors should also document their treatment of the well and the outcome of the project. This is also a good time to recommend any future maintenance to the well owner or set up a maintenance contract with them for future work.
Well rehabilitation products are available from various manufacturers and we are always ready to help you with proper use for a successful and profitable project.