Why Seal a Borehole?
Sealing a borehole with FLUTe liners after drilling prevents cross contamination. With traditional practice, the borehole is left open for extended periods of time between the time the borehole was drilled and downhole characterization. Additionally, if straddle packer are used for characterization, large portions of the borehole remain unsealed during all portions of the investigation.
The problems that can occur when boreholes remain open include mobilization of contaminants into the open borehole, contaminant adhesion to the borehole wall , and contaminated migration from the open borehole into previously uncontaminated fractures (Figure 1 and 2). Additionally, when making measurements with straddle packers which by default leave portions of the borehole open, leakage past the packer can result in exaggerated flow rates and contaminant distributions that are erred from cross contamination with mixed borehole water.
By using FLUTe liners, the borehole is either sealed while all downhole measurements are collected or as the liner sequentially seals off flow paths. In this way, the data integrity is very high as cross contamination and cross flow measurements cannot occur.
Figure 1. DNAPL Confined to an Isolated Fracture
Figure 2. DNAPL spread to other fractures as a result of the newly drilled borehole acting as a flow path between otherwise unconnected fractures.