What are well logs used for?

Engineers and drillers use well logs to measure depths of formation tops, thickness of formations, porosity, water saturation, temperature, types of formations encountered, presence of oil and/or gas, estimated permeability, reservoir pressures and formation dip — ultimately determining whether a well is commercially …

What is in a well log?

The well logs record physical properties of the borehole which must then be petrophysically interpreted to obtain the associated rock and fluid properties of the well. The standard well logs are the temperature log, the caliper log, and the resistivity log.

What is a well log data?

Well logs are records of petro-physical data acquired along a borehole, providing direct information about what is in the subsurface. The data collected by logging wells can have significant economic consequences, due to the costs inherent to drilling wells, and the potential return of oil deposits.

Why do the scientists are doing well logging?

The main purpose of keeping a well log is to determine the suitability of the well for its intended use. Well logs are also used by researchers to explore the underground. There are different types of well logs depending on drilling needs.

What are the three main uses of well logging?

3 Applications. Well logging is used for electrical imaging, mine mapping, and hydrocarbon and hydrological exploration to obtain in situ properties of possible reservoir rocks. Electric logs are considered useful for evaluating formation fluid properties.

How many types of well logging are there?

The two types of porosity logs (acoustic logs and nuclear logs) date originally from the 1940s. Sonic logs grew out of technology developed during World War II. Nuclear logging has supplemented acoustic logging, but acoustic or sonic logs are still run on some combination logging tools.

What is coring in well logging?

Coring and Core Analysis The process involves obtaining cylindrical samples of rock (cores) from a drilled well and analysing these cores in the laboratory to determine fundamental rock properties such as lithology, porosity, permeability and saturation of the various fluids in the formation.

What does density log measure?

The density log measures electron density by detecting gamma rays that undergo Compton scattering. The intensity of scattered gamma rays is proportional to electron density. Electron density is the number of electrons in a volume of the formation. Electron density is proportional to bulk density.

What is open hole logging?

Open-hole logging refers to logging operations that are performed on a well before the wellbore has been cased and cemented. In other words, the logging is done through the bare rock sides of the formation.

How is well logging done?

Wireline logging is performed by lowering a ‘logging tool’ – or a string of one or more instruments – on the end of a wireline into an oil well (or borehole) and recording petrophysical properties using a variety of sensors.

What are the objectives of well logging?

Well logging is an important contributor to formation evaluation. The objectives of formation evaluation include assessing resource size, supporting the placement of wells, and interpreting reservoir performance during development.

How does well logging work?

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How to read well log?

Well logs present a concise, detailed plot of formation parameters versus depth. From these plots, interpreters can identify lithologies, differentiate between porous and nonporous rock and quickly recognize pay zones in subsurface formations. The ability to interpret a log lies in recognizing the significance of each measurement.

What is logging while drilling (LWD)?

– Total gamma ray – Spectral gamma ray – Azimuthal gamma ray – Gamma ray close to drill bit.