To Find Oil, You Have to Drill, Schlumberger

Measurement is key to understanding the science of drilling, and the only way to gain a complete picture of the drilling environment is to combine measurements coming from both downhole and surface sensors. The drilling fluid, which circulates down the drillstring before returning to surface, is an excellent source of information because it carries rock cuttings together with small quantities of formation fluids absorbed during the circulation process.

To Find Oil, You Have to Drill, Schlumberger