Cased Hole Pre-Packed Well Installation
To install a Direct Push Pre-Packed Well in a cased hole, we advance either a 2.125-inch, or a 3.25-inch, or a 3.50-inch Direct Push casing fitted with an expendable drive point, typically using a 6600 Series Geoprobe®. The expendable point and casing serve to ensure that the hole remains open while the soil is separated and the tooling advanced. Once the point and casing achieve the desired depth, we assemble the components of the pre-packed well to our client’s specifications.
Pre-packed wells offer inner diameters (ID) ranging in size from three quarters of an inch (.75-inch ID) to two inches (2-inch ID). Screen lengths are typically in increments of five (5) feet or can be customized to meet our client’s needs. In addition, the grain size of the sand pack can be modified to meet any project’s requirements resulting from lithological conditions or regulatory protocol.
The next step is to lower the assembled pre-packed well into the open casing. At the top of the screened interval we add a foam bridge and a bentonite sleeve to ensure an absolute seal and to eliminate the potential for “bridging” often experienced in standard well construction. Blank PVC sections are added as we lower the well to the desired depth. When depth is achieved, we then extract the casing, leaving the assembled well and PVC in place. Once the casing is above the screened interval and the bentonite sleeve, we seal the annulus to the surface using a grout slurry. If desired, we will complete each well with either a flush-mounted well cover or a stand-up well box.
Dual Wall Pre-Packed Well Installation
To install a Direct Push Pre-Packed Well using the Dual Wall Sampling Method, we advance a 3.25-inch or a 3.50-inch Direct Push casing that houses an inner 2.125-inch macro core sampler. We advance the outer casing and inner sampler simultaneously in two, four, or five foot intervals, depending upon the application and lithology. At each interval, we raise the inner sampler to the surface and remove the sample, leaving the outer casing in place. After extracting the sample, we replace the sample sleeve and lower the sampler back down the casing to the last depth achieved. We again advance the casing and sampler to the next interval collecting the next sample. We repeat this process until we achieve the final targeted depth.*
With the casing in place and the inner sampler removed, we assemble the components of the pre-packed well to our client’s specifications. Pre-packed wells offer inner diameters (ID) ranging in size from three quarters of an inch (.75-inch ID) to two inches (2-inch ID). Screen lengths are typically in increments of five (5) feet or can be customized to meet our client’s needs. In addition, the grain size of the sand pack can be modified to meet any project’s requirements resulting from lithological conditions or regulatory protocol.
The next step is to lower the assembled pre-packed well into the open casing. At the top of the screened interval we add a foam bridge and a bentonite sleeve to ensure an absolute seal and to eliminate the potential for “bridging” often experienced in standard well construction. Blank PVC sections are added as we lower the well to the desired depth. When depth is achieved, we then extract the casing, leaving the assembled well and PVC in place. Once the casing is above the screened interval and the bentonite sleeve, we seal the annulus to the surface using a grout slurry. If desired, we will complete each well with either a flush-mounted well cover or a stand-up well.
* (Please refer to Vironex Dual Walled Sampling Standard Operating
Procedure (SOP) for further detail.)
