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    How To Read A Log

    Uploaded by

    Shaho Abdulqader Mohamedali
    This document provides examples and explanations for how to read well logs and use Archie's equation. It begins with an overview of well logs and the physical properties they measure. It then demonstrates how to interpret specific logs to understand properties like porosity, resistivity, and water saturation. The document explains Archie's equation for calculating water saturation from resistivity measurements. It provides two examples of using Archie's equation and interpreting a full log suite to determine where hydrocarbons versus water are present in different zones of a formation.

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    © All Rights Reserved
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    How To Read A Log

    Uploaded by

    Shaho Abdulqader Mohamedali
    34 views29 pages
    This document provides examples and explanations for how to read well logs and use Archie's equation. It begins with an overview of well logs and the physical properties they measure. It then demonstrates how to interpret specific logs to understand properties like porosity, resistivity, and water saturation. The document explains Archie's equation for calculating water saturation from resistivity measurements. It provides two examples of using Archie's equation and interpreting a full log suite to determine where hydrocarbons versus water are present in different zones of a formation.

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    how to read a log

    Original Title

    How to read a log

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    This document provides examples and explanations for how to read well logs and use Archie's equation. It begins with an overview of well logs and the physical properties they measure. It then demonstrates how to interpret specific logs to understand properties like porosity, resistivity, and water saturation. The document explains Archie's equation for calculating water saturation from resistivity measurements. It provides two examples of using Archie's equation and interpreting a full log suite to determine where hydrocarbons versus water are present in different zones of a formation.

    Copyright:

    © All Rights Reserved
    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    34 views29 pages

    How To Read A Log

    Uploaded by

    Shaho Abdulqader Mohamedali
    This document provides examples and explanations for how to read well logs and use Archie's equation. It begins with an overview of well logs and the physical properties they measure. It then demonstrates how to interpret specific logs to understand properties like porosity, resistivity, and water saturation. The document explains Archie's equation for calculating water saturation from resistivity measurements. It provides two examples of using Archie's equation and interpreting a full log suite to determine where hydrocarbons versus water are present in different zones of a formation.

    Copyright:

    © All Rights Reserved
    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    of 29

    How to read a Log and

    Archies Equation with examples


    Bien Nguyen (HB49051)
    WPS Vung Tau City
    29th August 2010

    I. How to read a Log?

    Well Logging?
    Well log is a continuous record of measurement made in

    bore hole respond to variation in some physical


    properties of rocks through which the bore hole is
    drilled.
    Logs are display on grided papers, films, images, or
    digital format.

    Physical properties of rocks


    Spontaneous Potential: SP
    Gamma Ray: GR
    Caliper
    Porosity: D, N, S
    Resistivity: Rxo, Ri, Rt

    How to understand a Log?

    GR/SP log vs. Caliper log


    GR (5330 ft) = 21 API
    21 API

    Porosity log: D, T
    D (5330 ft) = 41 (%)
    N (5330 ft) = 19 (%)
    41 (%)

    19 (%)

    Resistivity log
    RT (5330 ft) = 55 (ohm)

    55 (ohm)

    .2

    20

    200

    2000

    How to read a log?


    GR = 80 (API)
    RT = 25 (Ohm)
    N = 0.11 (=11%)
    b = 2.55 (g/cm3)

    At 3450m?

    Logs functions?
    Archie
    Equation

    II. Archie Equation


    The fraction of pore space occupied by water can be
    calculated using the Archie equation

    Archie Equation
    Assume a 100% water-bearing formation (connected porosity) filled with water.

    Water is a conductor
    Rock is an insulator
    Physical measurement

    provided is RESISTIVITY

    Rw

    Archie Equation
    Assume a 100% water-bearing formation (connected porosity) filled with water.

    Increase porosity

    decrease Ro
    Decrease porosity

    increase Ro
    Therefore
    Rw

    Archie Equation
    Now add OIL to that formation.

    Oil is an insulator, current path

    now longer because of oil.


    Resistivity is increased.

    Rt
    In a Hydrocarbon-bearing rock,

    this is referred to as TRUE


    resistivity (Rt)

    Archie Equation
    Now add OIL to that formation.

    Rt = F(Rw, amount of water, amount of oil)

    Ro = F x Rw
    Rt

    Archie Equation
    Now add OIL to that formation.

    Where:
    Sw = water saturation of un-invaded zone
    n

    = saturation exponent

    = tortuosity factor

    m = cementation exponent
    = porosity
    Rw = formation water resistivity
    Rt = true resistivity of un-invaded zone

    Archie Equation
    a = Tortuosity factor, related to the rock conductivity
    m = Cementation or Porosity exponent
    n = Saturation exponent (Usually = 2)

    Example 1:
    Calculate Sw of formation at 5300 (ft)
    T = 30%
    RT = 55 (Ohm)
    Assume:
    a = 0.62
    m = 2.15
    (for sandstone)
    n = 2.0
    Rw = 0.15 (Ohm)

    Example 1:
    Calculate Sw of formation at 5300 (ft)
    Solution

    Sw = 15%

    Example 1:
    Calculate Sw of formation at 5300 (ft) by Archie Nomograph:
    Procedure:

    1. Rw = 0.15 (Ohm)
    T = 30%
    2. Rt = 55 (Ohm)
    3. n = 2
    4. Sw = 15 (%)

    Sw = 15%

    Example 2:
    Where are Hydrocarbon (oil&gas)
    and water in Limestone formation?

    Procedures:
    1. Pick the intervals that are more interest than
    others bases on high Rt and
    2. Determine formation Rw from the low resistivity
    and relatively high porosity zones
    3. Calculate Sw of the interest zones

    Example 2:
    Where are Hydrocarbon (oil&gas)
    and water in limestone formation?

    Procedures:
    1. Pick the intervals that are more interest than
    others based on high Rt and (1, 2, 3)
    2. Determine formation Rw from the low resistivity
    and relatively high porosity zones

    3. Calculate Sw of the interest zones

    Example 2:
    Where are Hydrocarbon (oil&gas)
    and water in limestone formation?
    Procedures:

    A
    B

    1. Pick the intervals that are more interest than


    others based on high Rt and (1, 2, 3)
    2. Determine formation Rw from the low resistivity
    and relatively high porosity zones (B, D)

    3. Calculate Sw of the interest zones

    3
    D

    Example 2:
    Where are Hydrocarbon (oil&gas)
    and water in limestone formation?

    A
    B

    Procedures:

    2. Determine formation Rw from the low resistivity


    and relatively high porosity zones (B, D)
    Assume Sw = 100%, m = 2.0, a = 1.0

    At B (8535 ft): = 0.28, Rt = 0.7 (Ohm)


    Rw(B) = 0.055 (Ohm)
    At D (8710 ft): = 0.31, Rt = 0.4 (Ohm)
    Rw(D) = 0.038 (Ohm)

    3
    D

    Example 2:
    Where are Hydrocarbon (oil&gas)
    and water in limestone formation?

    A
    B

    Procedures:

    2. Determine formation Rw from the low resistivity


    and relatively high porosity zones (B, D)
    Which Rw should be use:
    Rw(B) = 0.055 (Ohm)
    or

    Rw(D) = 0.038 (Ohm)

    It is based on experiences of log analyst???

    3
    D

    Example 2:
    Where are Hydrocarbon (oil&gas)
    and water in limestone formation?
    Procedures:

    A
    B

    1. Pick the intervals that are more interest than


    others bases on high Rt and (1, 2, 3)
    2. Determine formation Rw from the low resistivity
    and relatively high porosity zones (B, D)

    3. Calculate Sw of the interest zones


    Zone1: A
    Zone2: C
    Zone3: D

    3
    D

    Example 2:
    Where are Hydrocarbon (oil&gas)
    and water in limestone formation?
    Procedures:

    A
    B

    3. Calculate Sw of the interest zones


    Zone1 (A):
    = 0.28, Rt = 5.0 (Ohm), RwD = 0.038 (Ohm)
    SwA = 31.14 (%)

    Zone2 (C):
    = 0.09, Rt = 8.4 (Ohm), RwD = 0.038 (Ohm)
    SwC = 74.73 (%)
    Zone3 (D):
    = 0.31, Rt = 0.5 (Ohm), RwD = 0.038 (Ohm)
    SwD = 88.93 (%)

    3
    D

    Example 2:
    Where are Hydrocarbon (oil&gas)
    and water in limestone formation?
    Zone1 (A):

    A
    B

    SwA = 31.14 (%)


    Zone2 (C):
    SwC = 74.73 (%)

    Zone3 (D):
    SwD = 88.93 (%)
    Conclusion:
    A: Hydrocarbon
    B, D: Water
    C: ???

    3
    D

    Thank you your contributions!

    Study more and more!

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