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Water Well logging near Bat Shlomo, Israel

Water supply in Israel relies essentially on groundwater from shallow aquifers (Israel Coastal aquifer), deep aquifers and seawater desalination.

A substantial portion of the freshwater supply relies on water abstraction from deep aquifers, which are managed and utilized by mostly Mekorot, the Israel Water Company, which operates hundreds of such wells. Many of the wells are ageing and need to be replaced. In the coming years many wells are expected to be drilled. The depth of the water wells in the deep aquifers ranges between 400m and 1200m, depending on the location and the depth of water bearing layers, having sufficiently good hydraulic properties and sufficiently good groundwater quality.

Shacham, a subsidiary of the Mekorot Company is one of the main drilling contractors for this work. EWRE (Environmental and Water Resources Engineering Ltd) based in Haifa, has been commissioned by Shacham to manage the acquisition of data from the wells it drills. EWRE uses Robertson Geo equipment for the logging.

Loggings occurs at various stages of the drilling process:

• When reaching the upper section (usually 200-300 meters) and the target depth  • After the casing and cementation of the well

So far, the logs conducted during the drilling are:

• Electrical Resistivity  • Temperature  • Natural Gamma  • Full Waveform Sonic  • 3-Arm Caliper

High Resolution Acoustic Televiewer (HRAT), spectral radioactivity and density logs are also expected to be introduced.

After the drilling, a CBL log and Gyroscopic verticality log are completed.

The purpose of the logging during drilling and before the casing is to characterise the geologic profile and correlate with data from other wells. This, to determine the location and size of the perforated section of the well and to determine the target depth of the well. EWRE has developed a module based on several machine learning algorithms to classify the cross section into different rock types, based on the log data. The more logs conducted, the more refined is the classification procedure. The gyroscopic verticality is needed for the installation of the production pump.

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