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How do petrophysical engineers measure the properties of reservoir rocks and fluids?

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petroleum production A semisubmersible oil production platform operating in water 1,800 metres (6,000 feet) deep in the Campos basin, off the coast of Rio de Janeiro state, Brazil.

Petrophysical engineers, also known as formation-evaluation engineers, determine the characteristics of reservoir rocks and fluids by employing a combination of analytical techniques and specialized measurement tools.1

To assess these properties, they measure the acoustic, radioactive, and electrical characteristics of the rock-fluid system. Historically, this was performed using well logging, where tools were lowered into a borehole via steel cable to record signals based on differences in electrical conductivity, radioactivity, neutron absorption, and acoustic wave absorption.12

Modern practices utilize advanced logging-while-drilling (LWD) and measurement-while-drilling (MWD) technologies. These methods allow for real-time data collection, including:
* Gamma ray logging
* Resistivity measurement
* Density and neutron porosity logging
* Sonic logging
* Pressure testing and fluid sampling
* Borehole diameter measurements using calipers2

Additionally, engineers take physical samples of rocks and well fluids to directly determine porosity, permeability, and fluid content. These measurements are essential for characterizing the reservoir and minimizing uncertainties in oil and gas development.1