The Water Well Geologist’s Field Notebook—Using the Penetration Rate

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The penetration rate is useful while drilling to understand how a particular drilling rig and process are moving through different formation types.

By Christopher S. Johnson, PG, CHg

I’ve said designing a well is like trying to build a jigsaw puzzle without the top of the box, which is why you need as many puzzle pieces to figure out what you’re looking at.  Along with the usual geologic information, drilling data should be collected because it’s part of the puzzle.

Collecting data on the interaction of various drilling methods and the subsurface is invaluable to the water well geologist. This information can be correlated to formation samples, geophysical logs, and to other wells in the project area. Furthermore, drilling data is useful when drilling more than one well in an area or trying to interpret reported information from other wells in an area.

The drilling process is complex. Important portions of that process to understand include the configuration of the drill string, the capabilities of the entire drilling fluid circulation system, the sample collection and handling process, and the measurement of specific drilling process characteristics.

Drilling processes have characteristics unique to themselves, but all drilling processes have some shared and similar characteristics. It is a few of those shared characteristics that interest a well site geologist.

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