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GeolOil - Recipes Cookbook and Petrophysics Manual

"The GeolOil website with the recipes articles are some of my favourite petrophysics links, always so concise and well explained"
Gareth Williams. Senior Petrophysicist, CGG. Llandudno, Wales, United Kingdom.∎

A handbook of tips, recipes, and key petrophysical concepts to compute log parameters with GeolOil software:

How to merge LAS files

A recipe on how to merge several different LAS files into a single unified one. Wells usually have log curves scattered in different LAS files of different step resolutions and depth zone coverage.

Access built-in examples

GeolOil ships with a small collection of LAS and GLOG files. Learn how to access them. The built-in collection can be optionally expanded with a learning set of practical study cases —highly recommended—

Importing core data

This recipe shows how to import core data, which should be displayed as a collection of irregularly spaced dots. Core data can be imported from CSV Excel spreadsheets.

Computing Net-Pay and Net-Sand

Learn how to calculate parameters of reservoir quality, like net-reservoir and net-pay thickness, and even to plot them on your log display.

How to compute petrophysical cutoffs

The standard, classical default technique to compute cutoffs for volume of shale, porosity and water saturation. One of our most referenced articles on the internet, even for the year 2019 patents.

Compute VSH from GR index

Learn how to compute volume of shale from the gamma-ray curve using the formulas of Linear Index, Larionov, Clavier, Stieber, and GeolOil blend.

VSH from Neutron & Density

After VSH(GR), this is the most reliable technique. Neutron porosity curve responds to hydrogen content in clays. The overestimated porosity compared to density porosity yields a good estimate for VSH.

How to estimate Water Saturation

GeolOil has 25 different classical models to compute water saturation and Total Organic Content (TOC). Compare results with different models. Check the influence of electrical parameters on SW.

The Indonesia Water Saturation

The Indonesia Poupon-Leveaux model is among the finest SW models. It is a general purpose equation, often more accurate than Simandoux, specially in clastic reservoirs with low salinities.

Geomechanic properties

Our toolbox of equations to calculate common rock geomechanical properties, like Young Modulus of elasticity, Poisson Ratio, Unconfined Compressive Strength (UCS), Sand Production Index, and others.

How to split the rock volume

A simple recipe on how to split the rock components. Visualize and display volumetric proportions of Vshale, non shaly matrix, and split the porosity in water and hydrogen fluids.

GeolOil mineral solvers

Check our fine built-in collection of fuzzy logic mineral solvers. They are easy to use, yet provide reliable results even when compared with X-RAY diffraction core lab measurements.

Estimate fracture porosity from logs

Estimate fracture porosity at the log scale (1-3 feet), using sonic and density logs. Correlate fracture porosity with geomechanical properties to explore where fracture occurs.

How to screen for pay zones?

This article explains the concepts behind the Apparent Water Resistivity (Rwa). Learn how to correct Rwa for clay in shaly reservoirs. Quickly screen for pay zones without a custom fit SW model.

Compute Ionic Water Salinity

Water NaCl equivalent salinity and Rw, are probably the most important parameters to establish a good SW model. Learn how to compute salinity and Rw from ionic water analyses.

How to estimate Rw and m exponent

This article gives clues and techniques on how to estimate formation water resistivity (Rw), and cementation porosity exponent "m" using only log curves data.

How to estimate matrix density RHOM?

This article discusses techniques and hints on how to estimate the rock matrix density (RHOM) based on core, and specially log data using neutron and density curves, as well as mineral solvers.

Zone averages and Upscalings

How to calculate averages of properties for zones like formations, members, beds, facies, and flow units. Estimate upscaled water saturation and porosities suitable for volumetrics.

How to estimate Porosity from Rxo?

Learn to estimate porosity from the flushed zone resistivity. The estimation does not depend on RHOB or NPHI and is robust against the presence of gas. The article also introduces corrections for shaly matrices.

How to estimate SW from Rxo?

The SW Ratio method allows to estimate the water saturation on clean formations without knowing its porosity. This article also introduces corrections to deal with shaly matrices.

How to detect gas caps

This article discusses three techniques to detect gas caps: The neutron-density cross-over difference, the increase in fluid transit time, and the overburden vertical stress gradient change.

LAS curve Mnemonic List

This page shows a dictionary of typically encountered mnemonics for LAS file curves, their descriptions, and our suggested aliases. It is a quick resource reference.

Work-Flow of Sequential Functions

The GeolOil interpretation work-flow is an ordered sequence of chained functions. Each parameter can be a constant or a curve on its own. Change any parameter and update your model with a single click.

GLS Well logging Scripting

GeolOil Logging Scripting is a specific powerful language for well logs. It is probably the easiest tool in the industry of petrophysics software. Far easier than Schlumberger Python TechLog.

GSL Scripting Manual

The reference manual for the GLS language, with the list of functions, syntax, its compact default streaming mode, and its advanced looping mode.

Modified Simandoux Water Saturation

This page shows the modified Simandoux equation for water saturation and two variations that avoid iterative solutions. It also deduces the Simandoux model from the Archie conductivity.

Vshale or Vclay?

An article that highlights the differences between VSH and VCL, and how to compute from logs. A core photograph ilustrates the sealing nature of shales.

LAS curve Mnemonic List

This page shows a dictionary of typically encountered mnemonics for LAS file curves, their descriptions, and our suggested aliases. It is a quick resource reference.

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