What is a petrophysical log?

What is a petrophysical log?

Petrophysics is the study of physico- chemical properties of rocks and their interactions with the surrounding fluids. The main objective of petrophysical well log analysis is to transform well log measurements into reservoir properties like porosity, permeability, oil saturation etc.

How do you find the porosity of a well log?

The most common method of determining porosity is with Well Logs….

1. ϕsl is the porosity from the sonic log (log measurement) , fraction.
2. Δtsl is value of the acoustic transit time measured by the sonic log, μsec/ft.
3. Δtma is value of the acoustic transit time of the rock matrix measured in the laboratory, μsec/ft.

What is well log analysis?

Well logs present a concise, detailed plot of formation parameters versus depth. Logging tools record the magnitude of a specific formation property, such as resistivity, measured as the tool traverses an interval defined by depth; a well log is a chart that shows the value of that measurement plotted versus depth.

What is petrophysical evaluation?

The petrophysical evaluation consists of estimation of the volumes of minerals and fluids present in the invaded and virgin zones. The volume of clay is first estimated using a combination of Gamma ray (GR) and Neutron-density logs.

What is petrophysical data?

PetroWiki. In making the petrophysical calculations of lithology, net pay, porosity, water saturation, and permeability at the reservoir level, the development of a complete petrophysical database is the critical first step.

What are the different types of porosity logs?

The “Porosity” logs. There are three types of logging tools that are used to estimate the amount of pore space in a rock: the neutron, density, and acoustic velocity (or sonic) tool.

How is oil porosity calculated?

Porosity (ɸ) = (Vp ÷ Vb) × 100

1. Direct methods: measurement from core flush by fluid or air.
2. Indirect methods: well logging tools (density, neutron, and sonic)

What are the different types of well logging?

Types of Well Logging

• Acoustic logging. Acoustic logging includes those techniques that use a transducer to transmit an acoustic wave through the fluid in the well and surrounding elastic materials.
• Electrical Methods. Spontaneous Potential Log.
• Flow Logging.
• Hole-to-Hole Logging.
• Hydrophysical Logging.
• Nuclear Logging.

What is well log correlation?

Well log correlation can be considered the identification and connection of equivalent patterns and/or values between log curves of adjacent wells. “Good’ or “accurate” correlation can almost be viewed as an acquired art or craft hence there can often be much argument and dispute over the results.

What is RT in well logging?

Rxo= Resistivity of flushed zone. Rw= Resistivity of formation water. Rmf= Resistivity of mud filtrate. Rt= Resistivity of uninvaded zone.

What is petrophysical modeling?

1. n. [Reservoir Characterization] A process or procedure used to interpret petrophysical (usually wireline log) data. Usually representing a set of equations, algorithms, or other mathematical processes, petrophysical models often have multiple routines.

Which is the third step in well log analysis?

Porosity calculation is the third step of well log analysis and it could only be done correctly if the first step (lithology interpretation) is correct.

How to analyze uncertainty in well log and petrophysical?

Uncertainties from well-log and petrophysical interpretations should be analyzed, quantified, and explicitly communicated to the integration team to be accounted for in reservoir characterization and modeling. Crossplot of the sonic traveltime and core porosity (in fraction) with the linear regression line (black) and Wylie time average line (red).

How is well log analysis used for reservoir characterization?

Some approaches are needed to characterize reservoir, by using well log data, the user may be able to calculate: The interpretation of well log data must be done in several steps and it is not recommended for the user to analyze them randomly because, the result might be a total error.

Who is the author of the Log Analysis Handbook?

Publication History: This article is based on Chapter 9 of “The Log Analysis Handbook” by E. R. Crain, P.Eng., published by Pennwell Books 1986 Updated 2004, 2021. This webpage version is the copyrighted intellectual property of the author. Do not copy or distribute in any form without explicit permission.