Quick Test

Rock Typing

Rock Typing
Rock Typing

In the field of reservoir engineering, calculating permeability accurately is crucial. Various methods, such as logging techniques (NMR, Sonic, Resistivity, MDT/RFT) and coring methods, particularly rock typing, play significant roles.

Today, let's delve into Rock Typing:

Geological Facies Rock Typing

  • Involves rocks with common lithology, grain size, and texture linked to the depositional environment.

Petrophysical Rock Typing

  • Focuses on rocks with a Porosity-Permeability relationship.
  • Hint: G&G and RE should agree on the same number of rock types.

For Petrophysical Rock Typing, we employ methods like:

  • K-Phi Cross Plot
  • FZI
  • Modified Lorenz Plot
  • Winland

We'll explore the first two methods:

  1. K-Phi Cross Plot
    • Indicates multiple rock types when a single porosity value corresponds to a wide range of permeability values.
    • Example 1:

Hint: No single equation fits the scattered data, necessitating multiple equations for different rock types in the reservoir.

  1. FZI (Flow Zone Indicator)
    • Developed by Amaefule et al. (1993), it identifies Hydraulic Flow Units (HFU) based on porosity and permeability measurements.
    • Characterized by functions such as Reservoir Quality Index (RQI), Pore Volume to Grain Volume Ratio, and Flow Zone Indicator (FZI).
    • Equations

  • Reservoir Quality Index (RQI)

  • Pore Volume to Grain Volume Ratio

  • Flow Zone Indicator (FZI)

Using all the available measured core permeability and porosity data, RQI and ϕz can be calculated by using Equations the previous equations.

Steps to apply FZI:

  1. Calculate RQI and Φz for each core sample.
  2. Plot RQI vs. Φz on log-log coordinates.
  3. Identify parallel unit slope straight lines representing different FZIs.
  4. Treat each line as an HFU characterized by an average FZI.
  5. Use the provided equations to calculate permeability for each FZI, assuming porosity, and formulating equations for each FZI.

Example 2:

Hint; Here, We have 5 Rock Types.

Then we will use the following equation to calculate Permeability for each FZI and assuming porosity and then making an equation for each FZI:

We determine which facies"FZI" we are against for new wells, then calculate permeability from porosity logs.

 

For a detailed analysis, download our Excel sheet

 

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