Horizontal drilling is used to install pipes for cables etc under obstacles such as buildings, rivers, roads etc. The drilling operation can be considerably delayed if the depth of drilling is chosen to coincide with underground structures with high drilling resilience. Consequently it is advantageous to perform a pre-drilling survey in order to determine the optimum depth of the pipe.
Resistivity mapping can be successfully applied in order to accomplish this as is shown by the present case story for the Advanced Geosciences STING/Swift system.
The survey data are published courtesy of NK3, Japan
Instrument: AGI Sting R1 resistivity meter with Swift smart electrode system
Array: 28 smart electrodes at 6 meter spacing
Measurement type: Dipole-Dipole
At this site there was already a horizontal hole drilled and during that operation extra time had been spent penetrating several gravel beds. The client wanted to investigate a method that allowed him to select an optimum depth before drilling. As can be seen in the figure it would have been better to drill 4 meters closer to the surface where most of the gravel could have been avoided.
The data were automatically acquired by the Sting/Swift system and inverted using the RES2DINV software package (avaliable from AGI). For presentation the inverted data were imported into Surfer for Windows where the report above was prepared.